VINAYAKA INSTITUTE OF NURSING, BAKROL

SECOND INTERNAL EXAM

GNM FIRST YEAR

BIO-SCIENCE

Hours-3 hrs Total-75 marks

Q-1) write down the answers.

1) DESCRIBING THE STRUCTURE OF LONG BONE AND MICROSCOPIC STRUCTURE OF LONG BONE

Structure

The outer shell of the long bone is made of cortical bone also known as compact bone. This is covered by a membrane of connective tissue called the periosteum. Beneath the cortical bone layer is a layer of spongy cancellous bone. Inside this is the medullary cavitywhich has an inner core of bone marrow made up of yellow marrow in the adult and red marrow in the child.

Microscopic Structure Of A Long Bone

Numerous hollow tunnels called Haversian canals occur within the matrix of bone tissue and run parallel with the length of the bone. Under the microscope they appear as black circles against a lighterbackground.

Each Haversian canal is surrounded by concentric rings of compact bone called lamellae

Each of these layers contains a ring of fluid-filled cavities called lacunae. Each of these lacuna will contain a number of bone cells called osteocytes.

The lacunae are linked to each other and to the Haversian canal by a system of very tiny interconnecting canals called canaliculi. Strands of cytoplasm extend through these canals which supply the osteocytes with oxygen and nutrients and remove waste products

The Haversian canals, lacunae, osteocytes and canaliculi together form a unit called a Haversion System and a number of these systems make up compact bone.

Apart from osteocytes which are embedded in the lacunae of bone there are two other types of bone cells

Osteoblasts : Bone forming cells. These cells allow the bone to change and remodel its shape as the organism grows and responds to stresses. If a bone is broken or if strengthening is needed, bone cells lay down new tissue and repair damaged tissu

Q-2) WRITE HEALING PROCESS OF FRACTURE

Bone healing

From Wikipedia, the free encyclopediaBone healing of a fracture by forming a callus as shown by X-ray.

Bone healing, or fracture healing, is a proliferative physiological process in which the body facilitates the repair of a bone fracture.

Generally bone fracture treatment consists of a doctor reducing (pushing) displaced bones back into place via relocation with or without anaesthetic, stabilizing their position to aid union, and then waiting for the bone's natural healing process to occur.

Adequate nutrient intake has been found to significantly affect the integrity of the fracture repair.[1] Age, Bone type, drug therapy and pre existing bone pathology are factors which affect healing. The role of bone healing is to produce new bone without a scar as seen in other tissues which would be a structural weakness or deformity.[2]

The process of the entire regeneration of the bone can depend on the angle of dislocation or fracture. While the bone formation usually spans the entire duration of the healing process, in some instances, bone marrow within the fracture has healed two or fewer weeks before the final remodeling phase.[citation needed]

While immobilization and surgery may facilitate healing, a fracture ultimately heals through physiological processes. The healing process is mainly determined by the periosteum (the connective tissue membrane covering the bone). The periosteum is one source of precursor cells which develop into chondroblasts and osteoblasts that are essential to the healing of bone. The bone marrow (when present), endosteum, small blood vessels, and fibroblasts are other sources of precursor cells.

2) DEFINE ACTION POTENTIAL IN NEURON CELLn physiology, an action potential occurs when the membrane potential of a specific axon location rapidly rises and falls:[1] this depolarisation then causes adjacent locations to similarly depolarise. In the original work of HH speed of transmission of an action potential was undefined and it was assumed that adjacent areas became depolarised due to released ion interference with neighbouring channels. Measurements of ion diffusion and radii have since shown this to not be possible. Moreover contradictory measurements of entropy changes and timing disputed the HH as acting alone. More recent work has shown that the HH action potential is not a single entity but is a Coupled Synchronised Oscillating Lipid Pulse (Action potential pulse) powered by entropy from the HH ion exchanges.[2]Action potentials occur in several types of animal cecalled excitable cells, which include neurons, muscle cells, and endocrinecells, as well as in some plant cells. In neurons, action potentials play a central role in cell-to-cell communication by providing for (or assisting in, with regard to saltatory conduction) the propagation of signals along the neuron's axon towards boutons at the axon ends which can then connect with other neurons at synapses, or to motor cells or glands. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas, they provoke release of insulin.[a] Action potentials in neurons are also known as "nerve impulses" or "spikes", and the temporal sequence of action potentials generated by a neuron is called its "spike train". A neuron that emits an action potential is often said to "fire".

Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane.[b] These channels are shut when the membrane potential is near the (negative) resting potential of the cell, but they rapidly begin to open if the membrane increases to a precisely defined threshold voltage, depolarising the transmembrane potential.[b] When the channels open they allow an inward flow of sodium ions, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential. This then causes more channels to open, producing a greater electric current across the cell membrane, and so on. The process proceeds explosively until all of the available ion channels are open, resulting in a large upswing in the membrane potential. The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse, and the ion channels then rapidly inactivate. As the sodium channels close, sodium ions can no longer enter the neuron, and then they are actively transported back out of the plasma membrane. Potassium channels are then activated, and there is an outward current of potassium ions, returning the electrochemical gradient to the resting state. After an action potential has occurred, there is a transient negative shift, called the afterhyperpolarization.

In animal cells, there are two primary types of action potentials. One type is generated by voltage-gated sodium channels, the other by voltage-gated calcium channels. Sodium-based action potentials usually last for under one millisecond[citation needed], whereas calcium-based action potentials may last for 100 milliseconds or longer[citation needed]. In some types of neurons, slow calcium spikes provide the driving force for a long burst of rapidly emitted sodium spikes. In cardiac muscle cells, on the other hand, an initial fast sodium spike provides a "primer" to provoke the rapid onset of a calcium spike, which then produces muscle contraction

Q-3) STRUCTURE OF THE HEART

The human heart is a four-chambered muscular organ, shaped and sized roughly like a man's closed fist with two-thirds of the mass to the left of midline.

The heart is enclosed in a pericardial sac that is lined with the parietal layers of a serous membrane. The visceral layer of the serous membrane forms the epicardium.

Layers of the Heart Wall

Three layers of tissue form the heart wall. The outer layer of the heart wall is the epicardium, the middle layer is the myocardium, and the inner layer is the endocardium.

Chambers of the Heart

The internal cavity of the heart is divided into four chambers:

Right atriumRight ventricleLeft atriumLeft ventricle

The two atria are thin-walled chambers that receive blood from the veins. The two ventricles are thick-walled chambers that forcefully pump blood out of the heart. Differences in thickness of the heart chamber walls are due to variations in the amount of myocardium present, which reflects the amount of force each chamber is required to generate.

The right atrium receives deoxygenated blood from systemic veins; the left atrium receives oxygenated blood from the pulmonary veins.

Valves of the Heart

Pumps need a set of valves to keep the fluid flowing in one direction and the heart is no exception. The heart has two types of valves that keep the blood flowing in the correct direction. The valves between the atria and ventricles are called atrioventricular valves (also called cuspid valves), while those at the bases of the large vessels leaving the ventricles are called semilunar valves.

The right atrioventricular valve is the tricuspid valve. The left atrioventricular valve is the bicuspid, or mitral, valve. The valve between the right ventricle and pulmonary trunk is the pulmonary semilunar valve. The valve between the left ventricle and the aorta is the aortic semilunar valve.

When the ventricles contract, atrioventricular valves close to prevent blood from flowing back into the atria. When the ventricles relax, semilunar valves close to prevent blood from flowing back into the ventricles.

Pathway of Blood through the Heart

While it is convenient to describe the flow of blood through the right side of the heart and then through the left side, it is important to realize that both atria and ventricles contract at the same time. The heart works as two pumps, one on the right and one on the left, working simultaneously. Blood flows from the right atrium to the right ventricle, and then is pumped to the lungs to receive oxygen. From the lungs, the blood flows to the left atrium, then to the left ventricle. From there it is pumped to the systemic circulation.

Blood Supply to the Myocardium

The myocardium of the heart wall is a working muscle that needs a continuous supply of oxygen and nutrients to function efficiently. For this reason, cardiac muscle has an extensive network of blood vessels to bring oxygen to the contracting cells and to remove waste products.

The right and left coronary arteries, branches of the ascending aorta, supply blood to the walls of the myocardium. After blood passes through the capillaries in the myocardium, it enters a system of cardiac (coronary) veins. Most of the cardiac veins drain into the coronary sinus, which opens into the right atrium.

Q-5) Name of the bones of lower limb

Femur and Patella. The femur is the single bone of the thigh region. It articulates superiorly with the hip bone at the hip joint, and inferiorly with the tibia at the knee joint. The patella only articulates with the distal end of the femur.

The narrowed region below the head is the neck of the femur. This is a common area for fractures of the femur. The greater trochanter is the large, upward, bony projection located above the base of the neck. Multiple muscles that act across the hip joint attach to the greater trochanter, which, because of its projection from the femur, gives additional leverage to these muscles. The greater trochanter can be felt just under the skin on the lateral side of your upper thigh. The lesser trochanter is a small, bony prominence that lies on the medial aspect

of the femur, just below the neck. A single, powerful muscle attaches to the lesser trochanter. Running between the greater and lesser trochanters on the anterior side of the femur is the roughened intertrochanteric line. The trochanters are also connected on the posterior side of the femur by the larger intertrochanteric crest.The elongated shaft of the femur has a slight anterior bowing or curvature. At its proximal end, the posterior shaft has the gluteal tuberosity, a roughened area extending inferiorly from the greater trochanter. More inferiorly, the gluteal tuberosity becomes continuous with the linea aspera (“rough line”). This is the roughened ridge that passes distally along the posterior side of the mid-femur. Multiple muscles of the hip and thigh regions make long, thin attachments to the femur along the linea aspera.The distal end of the femur has medial and lateral bony expansions. On the lateral side, the smooth portion that covers the distal and posterior aspects of the lateral expansion is the lateral condyle of the femur. The roughened area on the outer, lateral side of the condyle is the lateral epicondyle of the femur. Similarly, the smooth region of the distal and posterior medial femur is the medial condyle of the femur, and the irregular outer, medial side of this is the medial epicondyle of the femur. The lateral and medial condyles articulate with the tibia to form the knee joint. The epicondyles provide attachment for muscles and supporting ligaments of the knee. The adductor tubercle is a small bump located at the superior margin of the medial epicondyle. Posteriorly, the medial and lateral condyles are separated by a deep depression called the intercondylar fossa. Anteriorly, the smooth surfaces of the condyles join together to form a wide groove called the patellar surface, which provides for articulation with the patella bone. The combination of the medial and lateral condyles with the patellar surface gives the distal end of the femur a horseshoe (U) shape.

Patella

The patella (kneecap) is largest sesamoid bone of the body (see Figure 1). A sesamoid bone is a bone that is incorporated into the tendon of a muscle where that tendon crosses a joint. The sesamoid bone articulates with the underlying bones to prevent damage to the muscle tendon due to rubbing against the bones during movements of the joint. The patella is found in the tendon of the quadriceps femoris muscle, the large muscle of the anterior thigh that passes across the anterior knee to attach to the tibia. The patella articulates with the patellar surface of the femur and thus prevents rubbing of the muscle tendon against the distal femur. The patella also lifts the tendon away from the knee joint, which increases the leverage power of the quadriceps femoris muscle as it acts across the knee. The patella does not articulate with the tibia.

adults, and is more common in females. It often results from excessive running, particularly downhill, but may also occur in athletes who do a lot of knee bending, such as jumpers, skiers, cyclists, weight lifters, and soccer players. It is felt as a dull, aching pain around the front of the knee and deep to the patella. The pain may be felt when walking or running, going up or down stairs, kneeling or squatting, or after sitting with the knee bent for an extended period.Patellofemoral syndrome may be initiated by a variety of causes, including individual variations in the shape and movement of the patella, a direct blow to the patella, or flat feet or improper shoes that cause excessive turning in or out of the feet or leg. These factors may cause in an imbalance in the muscle pull that acts on the patella, resulting in an abnormal

tracking of the patella that allows it to deviate too far toward the lateral side of the patellar surface on the distal femur.

Because the hips are wider than the knee region, the femur has a diagonal orientation within the thigh, in contrast to the vertically oriented tibia of the leg (Figure 2). The Q-angle is a measure of how far the femur is angled laterally away from vertical. The Q-angle is normally 10–15 degrees, with females typically having a larger Q-angle due to their wider pelvis. During extension of the knee, the quadriceps femoris muscle pulls the patella both superiorly and laterally, with the lateral pull greater in women due to their large Q-angle. This makes women more vulnerable to developing patellofemoral syndrome than men. Normally, the large lip on the lateral side of the patellar surface of the femur compensates for the lateral pull on the patella, and thus helps to maintain its proper tracking.

However, if the pull produced by the medial and lateral sides of the quadriceps femoris muscle is not properly balanced, abnormal tracking of the patella toward the lateral side may occur. With continued use, this produces pain and could result in damage to the articulating surfaces of the patella and femur, and the possible future development of arthritis. Treatment generally involves stopping the activity that produces knee pain for a period of time, followed by a gradual resumption of activity. Proper strengthening of the quadriceps femoris muscle to correct for imbalances is also important to help prevent reoccurrence.

Figure 2. The Q-Angle. The Q-angle is a measure of the amount of lateral deviation of the femur from the vertical line of the tibia. Adult females have a larger Q-angle due to their wider pelvis than adult males.

Tibia

The tibia (shin bone) is the medial bone of the leg and is larger than the fibula, with which it is paired (Figure 3). The tibia is the main weight-bearing bone of the lower leg and the second longest bone of the body, after the femur. The medial side of the tibia is located immediately under the skin, allowing it to be easily palpated down the entire length of the medial leg.

The proximal end of ttibia is

greatly expanded. The two sides of this expansion form the medial coof the tibia and the lateral condyle of the tibia. The tibia does not have epicondyles. The top surface of each

condyle is smooth and flattened. These areas articulwith the medial and lateral condyles of the femur to form the knee joint. Between the articulating surfaces of the tibial condyles is

the intercondylar eminence, an irregular, elevated area that serves as the infsupporting ligaments of the knee.The tibial tuberosity is an elevated area on the anterior side of the tibia, near its proximal end. It is the final site of attachment for the muscle tendon associated with the patella. More inferiorly, the shaft of the tibia becomes triangular in shape. The anterior apex ofMH this triangle forms the anterior border of the tibia, which begins at the tibial tuberosity and runs inferiorly along the length of the tibia. Both the anterior border and the medial side of the triangular shaft are located immediately under the skin and can be easily palpated along the entire length of the tibia. A small ridge running down the lateral side of the tibial shaft is the interosseous border of the tibia. This is for the attachment of the interosseous membrane of the leg, the sheet of dense connective tissue that unites the tibia and fibula bones. Located on the posterior side of the tibia is the soleal line, a diagonally running, roughened ridge that begins below the base of the lateral condyle, and runs down and medially across the proximal third of the posterior tibia. Muscles of the posterior leg attach to this line.The large expansion found on the medial side of the distal tibia is the medial malleolus (“little hammer”). This forms the large bony bump found on the medial side of the ankle region. Both the smooth surface on the inside of the medial malleolus and the smooth area at the distal end of the tibia articulate with the talus bone of the foot as part of the ankle joint. On the lateral side of the distal tibia is a wide groove called the fibular notch. This area articulates with the distal end of the fibula, forming the distal tibiofibular joint.

Fibula

The fibula is the slender bone located on the lateral side of the leg (see Figure 3). The fibula does not bear weight. It serves primarily for muscle attachments and thus is largely surrounded by muscles. Only the proximal and distal ends of the fibula can be palpated.

The head of the fibula is the small, knob-like, proximal end of the fibula. It articulates with the inferior aspect of the lateral tibial condyle, forming the proximal tibiofibular joint. The thin shaft of the fibula has the interosseous border of the fibula, a narrow ridge running down its medial side for the attachment of the interosseous membrane that spans the fibula and tibia. The distal end of the fibula forms the lateral malleolus, which forms the easily palpated bony bump on the lateral side of the ankle. The deep (medial) side of the lateral malleolus articulates with the talus bone of the foot as part of the ankle joint. The distal fibula also articulates with the fibular notch of the tibia.

Tarsal Bones

The posterior half of the foot is formed by seven tarsal bones (Figure 4). The most superior bone is the talus. This has a relatively square-shaped, upper surface that articulates with the tibia and fibula to form the ankle joint. Three areas of articulation form the ankle joint: The superomedial surface of the talus bone articulates with the medial malleolus of the tibia, the top of the talus articulates with the distal end of the tibia, and the lateral side of the talus articulates with the lateral malleolus of the fibula. Inferiorly, the talus articulates with

the calcaneus (heel bone), the largest bone of the foot, which forms the heel. Body weight is transferred from the tibia to the talus to the calcaneus, which rests on the ground. The medial calcaneus has a prominent bony extension called the sustentaculum tali (“support for the talus”) that supports the medial side of the talus bone.

The cuboid bone articulates with the anterior end of the calcaneus bone. The cuboid has a deep groove running across its inferior surface, which provides passage for a muscle tendon. The talus bone articulates anteriorly with the navicular bone, which in turn articulates anteriorly with the three cuneiform (“wedge-shaped”) bones. These bones are the medial cuneiform, the intermediate cuneiform, and the lateral cuneiform. Each of these bones has a broad superior surface and a narrow inferior surface, which together produce the transverse (medial-lateral) curvature of the foot. The navicular and lateral cuneiform bones also articulate with the medial side of the cuboid bone.

Metatarsal Bones

The anterior half of the foot is formed by the five metatarsal bones, which are located between the tarsal bones of the posterior foot and the phalanges of the toesThese elongated bones are numbered 1–5, starting medial side of the foot. The first metatarsal bone is shorter and thicker than the others. The second metatarsal is the longest. The base of the metatarsal bone is the proximal end of each metatarsal bone. These articulate with the cuboid or cuneiform bones. The base of the fifth metatarsal has a large, lateral expansion that provides for muscle attachments. This expanded base of the fifth metatarsal can be felt as a bony bump at the midpoint along the lateral border of the foot. The expanded distal end of each metatarsal is the head of the metatarsal bone. Each metatarsal bone articulates with the proximal phalanx of a toe to form a metatarsophalangeal joint. The heads of the metatarsal bones also rest on the ground and form the ball (anterior end) of the foot.

Phalanges

The toes contain a total of 14 phalanx bones (phalanges), arranged in a similar manner as the phalanges of the fingers. The toes are numbered 1–5, starting with the big toe (hallux). The big toe has two phalanx bones, the proximal and distal phalanges. The remaining toes all have proximal, middle, and distal phalanges. A joint between adjacent phalanx bones is called an interphalangeal joint.

Q-5) gross structure of kidney.

Structure of the kidney

Externally, the kidney is surrounded by the renal fascia, the perirenal fat capsule, and the

renal capsule. Internally, the kidney is most importantly filled with nephrons that filter blood

and generate urine.

Q-4) fill in the blanks

1. Neuron is functional unit of neuron system.

2. Periosteum is the name of outer covering of bone.

3. Bladder is the reservoir for urine.

4 Action of biceps muscle is flexion,extection..

5.Dura matter is the second matter of meanings.

Q-5) true or false

1. antidiuretic hormone increase urine output- false

2. Acetylecholine is released during muscle action- true

3. Right ventricle sends the blood into aorta -False

4. sciatic nerve is the longest nerve in the body- True

5. Olfactory nerve are responsible for the vision- False

Q-4) write down following answers

Cerebral Cortex – Functional Areas

 The cerebral cortex is divided into sensory, motor and association areas. Sensory areas receive sensory input, motor areas control movement of muscles. Association areas are involved with more complex functions such as learning, decision making and complex movements such as writing.The central sulcus divides the primary sensory and motor areas. Both the sensory cortex and the motor cortex have been mapped out according to what part of the body it controls. A larger portion of the cortex is involved with the lips, face, and fingers which contain a greater number of sensory receptors.

Broca’s area, the motor speech area, is involved in translating thoughts into speech. Impulses from this area control the muscles of the larynx, pharynx and mouth that enable us to speak.

The visual area receives visual stimuli and the visual association area helps to interpret those stimuli. It is also involved with memory and recognition.

The auditory area receives auditory information. The auditory association area is where sound is interpreted as noise, music or speech.

Structure and function of nephron

he nephron carries out nearly all of the kidney's functions. Most of these functions concern the reabsorption and secretion of various solutessuch as ions (e.g., sodium), carbohydrates (e.g., glucose), and amino acids (e.g., glutamate). Properties of the cells that line the nephron change dramatically along its length; consequently, each segment of the nephron has highly specialized functions.[citation needed]

The proximal tubule as a part of the nephron can be divided into an initial convoluted portion and a following straight (descending) portion.[8]Fluid in the filtrate entering the proximal convoluted tubule is reabsorbed into the peritubular capillaries, including approximately two-thirds of the filtered salt and water and all filtered organic solutes (primarily glucose and amino acids).[citation needed]

The loop of Henle is a U-shaped tube that extends from the proximal tubule. It consists of a descending limb and an ascending limb. It begins in the cortex, receiving filtrate from the proximal convoluted tubule, extends into the medulla as the descending limb, and then returns to the cortex as the ascending limb to empty into the distal convoluted tubule. The primary role of the loop of Henle is to concentrate the salt in the interstitium, the tissue surrounding the loop.

Q-2) write the ans of the following.Conducting system of the heart.

The SA node is the natural pacemaker of the heart. You may have heard of permanent pacemakers (PPMs) and temporary pacing wires (TPWs) which are used when the SA node has ceased to function properly.

The SA node releases electrical stimuli at a regular rate, the rate is dictated by the needs of the body. Each stimulus passes through the myocardial cells of the atria creating a wave of contraction which spreads rapidly through both atria.

As an analogy, imagine a picture made up of dominoes. One domino is pushed over causing a wave of collapsing dominoes spreading out across the picture until all dominoes are down.

The heart is made up of around half a billion cells, In the picture above you can see the difference in muscle mass of the various chambers. The majority of the cells make up the ventricular walls. The rapidity of atrial contraction is such that around 100 million myocardial cells contract in less than one third of a second. So fast that it appears instantaneous.

The electrical stimulus from the SA node eventually reaches the AV node and is delayed briefly so that the contracting atria have enough time to pump all the blood into the ventricles. Once the atria are empty of blood the valves between the atria and ventricles close. At this point the atria begin to refill and the electrical stimulus passes through the AV node and Bundle of His into the Bundle branches and Purkinje fibres.

Imagine the bundle branches as motorways, if you like, with the Purkinje fibres as A and B roads that spread widely across the ventricles . In this way all the cells in the ventricles receive an electrical stimulus causing them to contract.

Using the same domino analogy, around 400 million myocardial cells that make up the ventricles contract in less than one third of a second. As the ventricles contract, the right ventricle pumps blood to the lungs where carbon dioxide is released and oxygen is absorbed, whilst the left ventricle pumps blood into the aorta from where it passes into the coronary and arterial circulation.At this point the ventricles are empty, the atria are full and the valves between them are closed. The SA node is about to release another electrical stimulus and the process is about to repeat itself. However, there is a 3rd section to this process. The SA node and AV node contain only one stimulus. Therefore every time the nodes release a stimulus they must recharge before they can do it again.Imagine you are washing your car and have a bucket of water to rinse off the soap. You throw the bucket of water over the car but find you need another one. The bucket does not magically refill. You have to pause to fill it.In the case of the heart, the SA node recharges whilst the atria are refilling, and the AV node recharges when the ventricles are refilling. In this way there is no need for a pause in heart function. Again, this process takes less than one third of a second.The times given for the 3 different stages are based on a heart rate of 60 bpm , or 1 beat per second.The term used for the release (discharge) of an electrical stimulus is "depolarisation", and the term for recharging is "repolarisation".So, the 3 stages of a single heart beat are:Atrial depolarisationAtrial and ventricular repolarisation.

Spinal cord

he spinal cord is the main pathway for information connecting the brain and peripheral nervous system.[2][3] Much shorter than its protecting spinal column, the human spinal cord originates in the brainstem, passes through the foramen magnum, and continues through to the conus medullaris near the second lumbar vertebra before terminating in a fibrous extension known as the filum terminale.

It is about 45 cm (18 in) (45 cm) long in men and around 43 cm (17 in) (43 cm) in women, ovoid-shaped, and is enlarged in the cervical and lumbar regions. The cervical enlargement, stretching from the C5 to T1 vertebrae, is where sensory input comes from and motor output goes to the arms and trunk. The lumbar enlargement, located between L1 and S3, handles sensory input and motor output coming from and going to the legs.

The spinal cord is continuous with the caudal portion of the medulla, running from the base of the skull to the body of the first lumbar vertebra. It does not run the full length of the vertebral column in adults. It is made of 31 segments from which branch one pair of sensory nerve roots and one pair of motor nerve roots. The nerve roots then merge into bilaterally symmetrical pairs of spinal nerves. The peripheral nervous system is made up of these spinal roots, nerves, and ganglia.

The dorsal roots are afferent fascicles, receiving sensory information from the skin, muscles, and visceral organs to be relayed to the brain. The roots terminate in dorsal root ganglia, which are composed of the cell bodies of the corresponding neurons. Ventral roots consist of efferent fibers that arise from motor neurons whose cell bodies are found in the ventral (or anterior) gray horns of the spinal cord.

The spinal cord (and brain) are protected by three layers of tissue or membranes called meninges, that surround the canal . The dura mater is the outermost layer, and it forms a tough protective coating. Between the dura mater and the surrounding bone of the vertebraeis a space called the epidural space. The epidural space is filled with adipose tissue, and it contains a network of blood vessels. The arachnoid mater, the middle protective layer, is named for its open, spiderweb-like appearance. The space between the arachnoid and

the underlying pia mater is called the subarachnoid space. The subarachnoid space contains cerebrospinal fluid (CSF), which can be sampled with a lumbar puncture, or "spinal tap" procedure. The delicate pia mater, the innermost protective layer, is tightly associated with the surface of the spinal cord. The cord is stabilized within the dura mater by the connecting denticulate ligaments, which extend from the enveloping pia mater laterally between the dorsal and ventral roots. The dural sac ends at the vertebral level of the second sacral vertebra.

In cross-section, the peripheral region of the cord contains neuronal white matter tracts containing sensory and motor axons. Internal to this peripheral region is the grey matter, which contains the nerve cell bodies arranged in the three grey columns that give the region its butterfly-shape. This central region surrounds the central canal, which is an extension of the fourth ventricle and contains cerebrospinal fluid.

The spinal cord is elliptical in cross section, being compressed dorsolaterally. Two prominent grooves, or sulci, run along its length. The posterior median sulcus is the groove in the dorsal side, and the anterior median fissure is the groove in the ventral side.

Cranial nerveSmell

The olfactory nerve (I) conveys the sense of smell.

Damage to the olfactory nerve (I) can cause an inability to smell (anosmia), a distortion in the sense of smell (parosmia), or a distortion or lack of taste. If there is suspicion of a change in the sense of smell, each nostril is tested with substances of known odors such as coffee or soap. Intensely smelling substances, for example ammonia, may lead to the activation of pain receptors (nociceptors) of the trigeminal nerve that are located in the nasal cavity and this can confound olfactory testing.[1][11]

Vision

The optic nerve (II) transmits visual information.[3][10]

Damage to the optic nerve (II) affects specific aspects of vision that depend on the location of the lesion. A person may not be able to see objects on their left or right sides (homonymous hemianopsia), or may have difficulty seeing objects on their outer visual fields (bitemporal hemianopsia) if the optic chiasm is involved.[12] Vision may be tested by examining the visual field, or by examining the retina with an ophthalmoscope, using a process known as funduscopy. Visual field testing may be used to pin-point structural lesions in the optic nerve, or further along the visual pathways.[11]

Eye movement

Various deviations of the eyes due to abnormal function of the targets of the cranial nervesThe oculomotor nerve (III), trochlear nerve (IV) and abducens nerve (VI) coordinate eye movement.Damage to nerves III, IV, or VI may affect the movement of the eyeball (globe). Both or one eye may be affected; in either case double vision (diplopia) will likely occur because the movements of the eyes are no longer synchronized. Nerves III, IV and VI are tested by observing how the eye follows an object in different directions. This object may be a finger or a pin, and may be moved at different directions to test for pursuit velocity.[11] If the eyes do not work together, the most likely cause is damage to a specific cranial nerve or Damage to the oculomotor nerve (III) can cause double vision (diplopia) and inability to coordinate the movements of both eyes (strabismus), also eyelid drooping (ptosis) and pupil dilation (mydriasis).[12][12] Lesions may also lead to inability to open the eye due to paralysis of the levator palpebrae muscle. Individuals suffering from a lesion to the oculomotor nerve may compensate by tilting their heads to alleviate symptoms due to paralysis of one or more of the eye muscles it controls.[11]Damage to the trochlear nerve (IV) can also cause diplopia with the eye adducted and elevated.[12] The result will be an eye which can not move downwards properly (especially downwards when in an inward position). This is due to impairment in the superior oblique muscle, which is innervated by the trochlear nerve.[11]Damage to the abducens nerve (VI) can also result in diplopia.[12] This is due to impairment in the lateral rectus muscle, which is innervated by the abducens nerve.[11]

Trigeminal nerve (V)[

The trigeminal nerve (V) comprises three distinct parts: The Ophthalmic (V1), the Maxillary (V2), and the Mandibular (V3) nerves. Combined, these nerves provide sensation to the skin of the face and also controls the muscles of mastication (chewing).[1] Conditions affecting the trigeminal nerve (V) include trigeminal neuralgia,[1] cluster headache,[13] and trigeminal zoster.[1] Trigeminal neuralgia occurs later in life, from middle age onwards, most often after age 60, and is a condition typically associated with very strong pain distributed over the area innervated by the maxillary or mandibular nerve divisions of the trigeminal nerve (V2 and V3).[14]

The facial nerve passes through the petrous temporal bone, internal auditory meatus, facial canal, stylomastoid foramen, and then the parotid gland.

Facial expression

Lesions of the facial nerve (VII) may manifest as facial palsy. This is where a person is unable to move the muscles on one or both sides of their face. A very common and generally temporary facial palsy is known as Bell's palsy. Bell's Palsy is the result of an idiopathic (unknown), unilateral lower motor neuron lesion of the facial nerve and is characterized by an inability to move the ipsilateral muscles of facial expression, including elevation of the eyebrow and furrowing of the forehead. Patients with Bell's palsy often have a drooping mouth on the affected side and often have trouble chewing because the buccinator muscle is affected.[1]

Hearing and balance

The vestibulocochlear nerve (VIII) splits into the vestibular and cochlear nerve. The vestibular part is responsible for innervating the vestibules and semicircular canal of the inner ear; this structure transmits information about balance, and is an important component of the vestibuloocular reflex, which keeps the head stable and allows the eyes to track moving objects. The cochlear nerve transmits information from the cochlea, allowing sound to be heard.[3]

When damaged, the vestibular nerve may give rise to the sensation of spinning and dizziness. Function of the vestibular nerve may be tested by putting cold and warm water in the ears and watching eye movements caloric stimulation.[1][11] Damage to the vestibulocochlear nerve can also present as repetitive and involuntary eye movements (nystagmus), particularly when looking in a horizontal plane.[11] Damage to the cochlear nerve will cause partial or complete deafness in the affected ear.[11]

Oral sensation, taste, and salivation

Deviating uvula due to cranial nerve IX lesion

The glossopharyngeal nerve (IX) innervates the stylopharyngeus muscle and provides sensory innervation to the oropharynx and back of the tongue.[1][15] The glossopharyngeal nerve also provides parasympathetic innervation to the parotid gland.[1] Unilateral absence of a gag reflex suggests a lesion of the glossopharyngeal nerve (IX), and perhaps the vagus nerve (X).[16]

Vagus nerve

Loss of function of the vagus nerve (X) will lead to a loss of parasympathetic innervation to a very large number of structures. Major effects of damage to the vagus nerve may include a rise in blood pressure and heart rate. Isolated dysfunction of only the vagus nerve is rare, but can be diagnosed by a hoarse voice, due to dysfunction of one of its branches, the recurrent laryngeal nerve.[1]

Damage to this nerve may result in difficulties swallowing.[11]

Shoulder elevation and head-turning

Winged scapulamay occur due to lesion of the spinal accessory.

Damage to the accessory nerve (XI) will lead to ipsilateral weakness in the trapezius muscle. This can be tested by asking the subject to raise their shoulders or shrug, upon which the shoulder blade (scapula) will protrude into a winged position.[1] Additionally, if the nerve is damaged, weakness or an inability to elevate the scapula may be present because the levator scapulae muscle is now solely able to provide this function.[14] Depending on the location of the lesion there may also be weakness present in the sternocleidomastoid muscle, which acts to turn the head so that the face points to the opposite side.[1]

Tongue movement

A damaged hypoglossal nerve will result in an inability to stick the tongue out straight.

A case with unilateral hypoglossal nerve injury in branchial cyst surgery.

The hypoglossal nerve (XII) is unique in that it is innervated from both the motor cortex of both hemispheres of the brain. Damage to the nerve at lower motor neuron level may lead to fasciculations or atrophy of the muscles of the tongue. The fasciculations of the tongue are sometimes said to look like a "bag of worms". Upper motor neuron damage will not lead to atrophy or fasciculations, but only weakness of the innervated muscles.[11]

When the nerve is damaged, it will lead to weakness of tongue movement on one side. When damaged and extended, the tongue will move towards the weaker or damaged side, as shown in the image.

Cardiac cycle The cardiac cycle refers to the sequence of mechanical and electrical events that repeats with every heartbeat.[1] It includes the phase of relaxation diastole and the phase of contraction systole. Because the human heart is a four chambered organ, there are atrial systole, atrial diastole, ventricular systole and ventricular diastole. The frequency of the cardiac cycle is described by the heart rate, which is typically expressed as beats per minute. Each cycle of the heart, from the point of view of the ventricles and the status of their valves, involves a minimum of four major stages: Inflow phase, Isovolumetric contraction, outflow phase and Isovolumetric relaxation.

The first and the fourth stages, together constitute the "ventricular diastole" stage, involve the movement of blood from the atria into the ventricles. Stages 2 and 3 involve the "ventricular systole" i.e. the movement of blood from the ventricles to the pulmonary artery (in the case of the right ventricle) and the aorta (in the case of the left ventricle).

"Ventricular diastole," begins when the ventricles starts to relax. At this point, some blood of the previous cycle's systole is still flowing out of the ventricles through the semilunar valves, due to the inertia of the moving blood column, which overcomes the higher pressure in the aorta/pulmonary trunk with respect to the pressure in the ventricles. This short lasting phase, called "protodiastole" ends with the closure of the semilunar valves, producing the second heart sound (S2). Now that both the AV valves and the semilunar valves are closed, the ventricles are now closed chambers. Hence, this phase is known as isovolumetric (also called isovolumic, isometric) relaxation phase. Then the atrioventricular (AV) valves (the mitral valve and the tricuspid valve) open, allowing blood to fill the ventricles. This ventricular inflow phase can be sub-divided into the 'first rapid filling phase' as blood rushes in from the atria as a result of ventricular dilation; a phase of slow ventricular filling called 'Diastasis', and the 'last rapid filling phase' due to atrial contraction (systole).

As the ventricular systole begins, pressure within the ventricle rises and the AV valve closes producing the 'first heart sound' (S1). The semilunar valves remain closed. The contracting ventricles become closed chambers again and this phase is termed as "isovolumic contraction". As the name implies, there is no change in volume, but intra-ventricular pressure rises. The outflow phase, "ventricular ejection," is when the intra-ventricular pressure has achieved a higher pressure than the blood in the aorta (or the pulmonary trunk), the corresponding semilunar valves open. Ejection phase begins.[2][3]

Throughout the cardiac cycle, blood pressure increases and decreases. The cardiac cycle is coordinated by a series of electrical impulses that are produced by specialised pacemaker cells found within the sinoatrial node and the atrioventricular node. The cardiac muscle is composed of myocytes which initiate their own contraction without the help of external nerves (with the exception of modifying the heart rate due to metabolic demand). The

duration of the cardiac cycle is the reciprocal of heart rate. Assuming a heart rate of 75 beats per minute, each cycle takes 0.8 seconds

Q-5) write down the short ans.Name of the neuro transmitter in brain

The three major categories of substances that act asneurotransmitters are (1amino acids (primarily glutamic acid, GABA, aspartic acid & glycine), (2) peptides (vasopressin, somatostatin, neurotensin, etc.) and (3) monoamines (norepinephrine, dopamine & serotonin) plus acetylcholine

Define circulation of heart

Blood comes into the right atrium from the body, moves into the right ventricle and is pushed into the pulmonary arteries in the lungs. After picking up oxygen, the blood travels back to the heart through the pulmonary veins into the left atrium, to the left ventricle and out to the body's tissues through the aorta

What is nerve and covering layer of nerve

a whitish fibre or bundle of fibres in the body that transmits impulses of sensation to the brain or spinal cord, and impulses from these to the muscles and organs."the optic nerve"

What is csf

cerebrospinal fluid (CSF) is a clear, colorless bodyfluid found in the brain and spinal cord. It is produced in the choroid plexuses of the ventricles of the brain. It acts as a cushion or buffer for the brain, providing basic mechanical and immunological protection to the brain inside the skull.

Name of the joint in body.

Movement Muscles Origin Insertion

Flexion(150°–170°)

Anterior fibers of deltoid Clavicle

Middle of lateral surface of shaft of humerus

Clavicular part of pectoralis major Clavicle

Lateral lip of bicipital groove of humerus

Long head of biceps brachii Supraglenoid tubercle of scapula Tuberosity of

radius, Deep fascia of forearmShort head

of biceps brachii Coracoid process of scapula

Coracobrachialis Coracoid process Medial aspect of shaft of humerus

Extension(40°)

Posterior fibers of deltoid Spine of scapula

Middle of lateral surface of shaft of humerus

Latissimus dorsiIliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3–4 ribs, inferior angle of scapula

Floor of bicipital groove of humerus

Teres major Lateral border of scapulaMedial lip of bicipital groove of humerus

Abduction(160°–180°)

Middle fibers of deltoid Acromion process of scapula

Middle of lateral surface of shaft of humerus

Supraspinatus Supraspinous fossa of scapulaGreater tubercle of humerus

Adduction(30°–40°)

Sternal part of pectoralis major

Sternum, upper six costal cartilages

Lateral lip of bicipital groove of humerus

Latissimus dorsiIliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3-4 ribs, inferior angle of scapula

Floor of bicipital groove of humerus

Teres major Lower third of lateral border of scapula

Medial lip of bicipital groove of humerus

Teres minor Upper two thirds of lateral border of scapula

Greater tubercle of humerus

Lateral rotation

(in abduction:

95°;in

adduction: 70°)

Infraspinatus Infraspinous fossa of scapula Greater tubercle of humerus

Teres minor Upper two thirds of lateral border of scapula

Greater tubercle of humerus

Posterior fibers of deltoid Spine of scapula

Middle of lateral surface of shaft of humerus

Medial rotation

(in abduction: 40°–50°;

in adduction:

70°)

Subscapularis Subscapular fossa Lesser tubercle of humerus

Latissimus dorsiIliac crest, lumbar fascia, spines of lower 3-4 ribs, inferior angle of scapula

Floor of bicipital groove of humerus

Teres major Lower third of lateral border of scapula

Medial lip of bicipital groove of humerus

Anterior fibers of deltoid Clavicle

Q-6) Define followingMicrobiologythe branch of science that deals with microorganisms.

Immunitythe ability of an organism to resist disease, either through the activities of specialized blood cells or antibodies produced by them in response to natural exposure or inoculation (active immunity) or by the injection of antiserum or the transfer of antibodies from a mother to her baby via the placenta or breast milk

AntibodyAn antibody (Ab), also known as an immunoglobulin (Ig),[1] is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as bacteria and viruses. 

ChemotherapyChemotherapy is the use of any drug to treat any disease. But to most people, the word chemotherapymeans drugs used for cancer treatment. It's often shortened to “chemo.” Surgery and radiation therapy remove, kill, or damage cancer cells in a certain area, but chemo can work throughout the whole body.Feb 16, 2016Antigena toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies

Microscopoe an optical instrument used for viewing very small objects, such as mineral samples or animal or plant cells, typically magnified several hundred times.

Q-7) Structure of bacterial cell wall

The cell envelope is composed of the plasma membrane and cell wall. As in other organisms, the bacterial cell wall provides structural integrity to the cell. In prokaryotes, the primary function of the cell wall is to protect the cell from internal turgor pressure caused by the much higher concentrations of proteins and other molecules inside the cell compared to its external environment. The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cytoplasmic membrane. Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape. It is relatively porous and is not considered to be a permeability barrier for small substrates. While all bacterial cell walls (with a few exceptions e.g. extracellular parasites such as Mycoplasma) contain peptidoglycan, not all cell walls have the same overall structures. Since the cell wall is required for bacterial survival, but is absent in some eukaryotes, several antibiotics (notably the penicillins and cephalosporins) stop bacterial infections by interfering with cell wall synthesis, while having no effects on human cells which have no cell wall only a cell membrane. There are two main types of bacterial cell

walls, those of gram-positive bacteria and those of gram-negative bacteria, which are differentiated by their Gram staining characteristics. For both these types of bacteria, particles of approximately 2 nm can pass through the peptidoglycan.[3] If the bacterial cell wall is entirely removed, it is called a protoplast while if it's partially removed, it is called a spheroplast. β-Lactam antibiotics such as penicillin inhibit the formation of peptidoglycan cross-links in the bacterial cell wall. The enzyme lysozyme, found in human tears, also digests the cell wall of bacteria and is the body's main defense against eye infections.

Write about sterilization method

Steam[

Front-loading autoclave

A widely used method for heat sterilization is the autoclave, sometimes called a converter or steam sterilizer. Autoclaves use steam heated to 121-134 °C under pressure. To achieve sterility, the article is heated in a chamber by injected steam until the article reaches a time and temperature setpoint. Meantime almost all the air is removed from the chamber, because air is undesired in the moist heat sterilization process (this is one trait that differ from a typical pressure cooker used for food cooking). The article is then held at that setpoint for a period of time which varies depending on the bioburden present on the article being sterilized and its resistance (D-value) to steam sterilization. A general cycle would be anywhere between 3 and 15 minutes, (depending on the generated heat)[10] at 121 °C at 100 kPa, which is sufficient to provide a sterility assurance level of 10−4 for a product with a bioburden of 106 and a D-value of 2.0 minutes.[11] Following sterilization, liquids in a pressurized autoclave must be cooled slowly to avoid boiling over when the pressure is released. This may be achieved by gradually depressurizing the sterilization chamber and allowing liquids to evaporate under a negative pressure, while cooling the contents.Proper autoclave treatment will inactivate all resistant bacterial spores in addition to fungi, bacteria, and viruses, but is not expected to eliminate all prions, which vary in their resistance. For prion elimination, various recommendations state 121-132 °C for 60 minutes or 134 °C for at least 18 minutes.[citation needed] The 263K scrapie prion is inactivated relatively quickly by such sterilization procedures; however, other strains of scrapie, and strains of CJD and BSE are more resistant. Using mice as test animals, one experiment showed that heating BSE positive brain tissue at 134-138 °C for 18 minutes resulted in only a 2.5 log decrease in prion infectivity.[12]Most autoclaves have meters and charts that record or display information, particularly temperature and pressure as a function of time. The information is checked to ensure that the conditions required for sterilization have been met. Indicator tape is often placed on packages of products prior to autoclaving, and some packaging incorporates indicators. The indicator changes color when exposed to steam, providing a visual confirmation.Biological indicators can also be used to independently confirm autoclave performance. Simple bioindicator devices are commercially available based on microbialspores. Most contain spores of the heat

resistant microbe Geobacillus stearothermophilus (formerly Bacillus stearothermophilus), which is extremely resistant to steam sterilization. Biological indicators may take the form of glass vials of spores and liquid media, or as spores on strips of paper inside glassine envelopes. These indicators are placed in locations where it is difficult for steam to reach to verify that steam is penetrating there.

For autoclaving, cleaning is critical. Extraneous biological matter or grime may shield organisms from steam penetration. Proper cleaning can be achieved through physical scrubbing, sonication, ultrasound or pulsed air.[13] Pressure cooking and canning are analogous to autoclaving, and when performed correctly renders food sterile.

Moist heat causes destruction of micro-organisms by denaturation of macromolecules, primarily proteins. This method is a faster process than dry heat sterilization.

Dry heat[

Dry heat sterilizer

Dry heat was the first method of sterilization, and is a longer process than moist heat sterilization. The destruction of microorganisms through the use of dry heat is a gradual phenomenon. With longer exposure to lethal temperatures, the number of killed microorganisms increases. Forced ventilation of hot air can be used to increase the rate at which heat is transferred to an organism and reduce the temperature and amount of time needed to achieve sterility. At higher temperatures, shorter exposure times are required to kill organisms. This can reduce heat-induced damage to food products.[14]The standard setting for a hot air oven is at least two hours at 160 °C. A rapid method heats air to 190 °C for 6 minutes for unwrapped objects and 12 minutes for wrapped objects.[15][16] Dry heat has the advantage that it can be used on powders and other heat-stable items that are adversely affected by steam (e.g. it does not cause rusting of steel objects).

Flaming[

Flaming is done to loops and straight-wires in microbiology labs. Leaving the loop in the flame of a Bunsen burner or alcohol lamp until it glows red ensures that any infectious agent gets inactivated. This is commonly used for small metal or glass objects, but not for large objects (see Incineration below). However, during the initial heating infectious material may be "sprayed" from the wire surface before it is killed, contaminating nearby surfaces and objects. Therefore, special heaters have been developed that surround the inoculating loop with a heated cage, ensuring that such sprayed material does not further contaminate the area. Another problem is that gas flames may leave carbon or other residues on the object if the object is not heated enough. A variation on flaming is to dip the object in 70% or higher ethanol, then briefly touch the object to a Bunsen burner flame. The ethanol will ignite and burn off rapidly, leaving less residue than a gas flame.

Incineration[edit]

Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. This method also burns any organism to ash. It is used to sterilize medical and other biohazardous waste before it is discarded with non-hazardous waste. Bacteria incinerators are mini furnaces used to incinerate and kill off any micro organisms that may be on an inoculating loop or wire.[17]

Tyndallization[edit]

Named after John Tyndall, Tyndallization[18] is an obsolete and lengthy process designed to reduce the level of activity of sporulating bacteria that are left by a simple boiling water method. The process involves boiling for a period (typically 20 minutes) at atmospheric pressure, cooling, incubating for a day, then repeating the process a total of three to four times. The incubation periods are to allow heat-resistant spores surviving the previous boiling period to germinate to form the heat-sensitive vegetative (growing) stage, which can be killed by the next boiling step. This is effective because many spores are stimulated to grow by the heat shock. The procedure only works for media that can support bacterial growth, and will not sterilize non-nutritive substrates like water. Tyndallization is also ineffective against prions.

Glass bead sterilizers[edit]

Glass bead sterilizers work by heating glass beads to 250 °C. Instruments are then quickly doused in these glass beads, which heat the object while physically scraping contaminants off their surface. Glass bead sterilizers were once a common sterilization method employed in dental offices as well as biologic laboratories,[19] but are not approved by the U.S. Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) to be used as a sterilizers since 1997.[20] They are still popular in European as well as Israeli dental practices although there are no current evidence-based guidelines for using this sterilizer.[19]

Chemical sterilization[edit]

Chemiclav

Chemicals are also used for sterilization. Heating provides a reliable way to rid objects of all transmissible agents, but it is not always appropriate if it will damage heat-sensitive materials such as biological materials, fiber optics, electronics, and many plastics. In these situations chemicals, either as gases or in liquid form, can be used as sterilants. While the use of gas and liquid chemical sterilants avoids the problem of heat damage, users must ensure that article to be sterilized is chemically compatible with the sterilant being used. In addition, the

use of chemical sterilants poses new challenges for workplace safety, as the properties that make chemicals effective sterilants usually make them harmful to humans.

Ethylene oxide[edit]

Ethylene oxide (EO, EtO) gas treatment is one of the common methods used to sterilize, pasteurize, or disinfect items because of its wide range of material compatibility. It is also used to process items that are sensitive to processing with other methods, such as radiation (gamma, electron beam, X-ray), heat (moist or dry), or other chemicals. Ethylene oxide treatment is the most common sterilization method, used for approximately 70% of total sterilizations, and for over 50% of all disposable medical devices.[21]

Ethylene oxide treatment is generally carried out between 30 °C and 60 °C with relative humidity above 30% and a gas concentration between 200 and 800 mg/l.[22] Typically, the process lasts for several hours. Ethylene oxide is highly effective, as it penetrates all porous materials, and it can penetrate through some plastic materials and films. Ethylene oxide kills all known microorganisms such as bacteria (including spores), viruses, and fungi (including yeasts and molds), and is compatible with almost all materials even when repeatedly applied. It is flammable, toxic and carcinogenic, however, with a reported potential for some adverse health effects when not used in compliance with published requirements. Ethylene oxide sterilizers and processes require biological validation after sterilizer installation, significant repairs or process changes.

The traditional process consists of a preconditioning phase (in a separate room or cell), a processing phase (more commonly in a vacuum vessel and sometimes in a pressure rated vessel), and an aeration phase (in a separate room or cell) to remove ethylene oxide residues and lower by-products such as ethylene chlorohydrin (EC or ECH) and, of lesser importance, ethylene glycol (EG). An alternative process, known as all-in-one processing, also exists for some products whereby all three phases are performed in the vacuum or pressure rated vessel. This latter option can facilitate faster overall processing time and residue dissipation.

The most common ethylene oxide processing method is the gas chamber method. To benefit from economies of scale, ethylene oxide has traditionally been delivered by filling a large chamber with a combination of gaseous ethylene oxide either as pure ethylene oxide, or with other gases used as diluents (chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), or carbon dioxide).

Ethylene oxide is still widely used by medical device manufacturers . Since ethylene oxide is explosive at concentrations above 3%,[23] ethylene oxide was traditionally supplied with an inert carrier gas such as a CFC or HCFC. The use of CFCs or HCFCs as the carrier gas was banned because of concerns of ozone depletion.[24] These halogenated hydrocarbons are being replaced by systems using 100% ethylene oxide because of regulations and the high cost of the blends. In hospitals, most ethylene oxide sterilizers use single use cartridges because of the convenience and ease of use compared to the former plumbed gas cylinders of ethylene oxide blends.

It is important to adhere to patient and healthcare personnel government specified limits of ethylene oxide residues in and/or on processed products, operator exposure after processing, during storage and handling of ethylene oxide gas cylinders, and environmental emissions produced when using ethylene oxide.

The U.S. Occupational Safety and Health Administration (OSHA) has set the permissible exposure limit (PEL) at 1 ppm calculated as an eight-hour time weighted average (TWA) [29 CFR 1910.1047] and 5 ppm as a 15-minute excursion limit (EL). The National Institute for

Occupational Safety and Health (NIOSH) immediately dangerous to life and health limit (IDLH) for ethylene oxide is 800 ppm.[25] The odor threshold is around 500 ppm,[26] so ethylene oxide is imperceptible until concentrations well above the OSHA PEL. Therefore, OSHA recommends that continuous gas monitoring systems be used to protect workers using ethylene oxide for processing.[27] Employees' health records must be maintained during employment and after termination of employment for 30 years.

Nitrogen dioxide[edit]

Nitrogen dioxide (NO2) gas is a rapid and effective sterilant for use against a wide range of microorganisms, including common bacteria, viruses, and spores. The unique physical properties of NO2 gas allow for sterilant dispersion in an enclosed environment at room temperature and ambient pressure. The mechanism for lethality is the degradation of DNA in the spore core through nitration of the phosphate backbone, which kills the exposed organism as it absorbs NO2. This degradation occurs at even very low concentrations of the gas.[28] NO2 has a boiling point of 21 °C at sea level, which results in a relatively high saturated vapor pressure at ambient temperature. Because of this, liquid NO2 may be used as a convenient source for the sterilant gas. Liquid NO2 is often referred to by the name of its dimer, dinitrogen tetroxide (N2O4). Additionally, the low levels of concentration required, coupled with the high vapor pressure, assures that no condensation occurs on the devices being sterilized. This means that no aeration of the devices is required immediately following the sterilization cycle.[29] NO2 is also less corrosive than other sterilant gases, and is compatible with most medical materials and adhesives.[29]

The most-resistant organism (MRO) to sterilization with NO2 gas is the spore of Geobacillus stearothermophilus, which is the same MRO for both steam and hydrogen peroxide sterilization processes. The spore form of G. stearothermophilus has been well characterized over the years as a biological indicator in sterilization applications. Microbial inactivation of G. stearothermophilus with NO2 gas proceeds rapidly in a log-linear fashion, as is typical of other sterilization processes. Noxilizer, Inc. has commercialized this technology to offer contract sterilization services for medical devices at its Baltimore, Maryland (U.S.) facility.[30] This has been demonstrated in Noxilizer’s lab in multiple studies and is supported by published reports from other labs. These same properties also allow for quicker removal of the sterilant and residuals through aeration of the enclosed environment. The combination of rapid lethality and easy removal of the gas allows for shorter overall cycle times during the sterilization (or decontamination) process and a lower level of sterilant residuals than are found with other sterilization methods.[29]

Ozone[edit]

Ozone is used in industrial settings to sterilize water and air, as well as a disinfectant for surfaces. It has the benefit of being able to oxidize most organic matter. On the other hand, it is a toxic and unstable gas that must be produced on-site, so it is not practical to use in many settings.

Ozone offers many advantages as a sterilant gas; ozone is a very efficient sterilant because of its strong oxidizing properties (E = 2.076 vs SHE[31]) capable of destroying a wide range of pathogens, including prions without the need for handling hazardous chemicals since the ozone is generated within the sterilizer from medical grade oxygen. The high reactivity of ozone means that waste ozone can be destroyed by passing over a simple catalyst that reverts it to oxygen and ensures that the cycle time is relatively short. The disadvantage of using ozone is that the gas is very reactive and very hazardous. The NIOSH immediately dangerous to life and health limit for ozone is 5 ppm, 160 times smaller than the 800 ppm IDLH for

ethylene oxide. Documentation for Immediately Dangerous to Life or Health Concentrations (IDLH): NIOSH Chemical Listing and Documentation of Revised IDLH Values (as of 3/1/95)[32] and OSHA has set the PEL for ozone at 0.1 ppm calculated as an 8 hour time weighted average (29 CFR 1910.1000, Table Z-1). The Canadian Center for Occupation Health and Safety provides an excellent summary of the health effects of exposure to ozone. The sterilant gas manufacturers include many safety features in their products but prudent practice is to provide continuous monitoring to below the OSHA PEL to provide a rapid warning in the event of a leak. Monitors for determining workplace exposure to ozone are commercially available.

Glutaraldehyde and formaldehyde[edit]

Glutaraldehyde and formaldehyde solutions (also used as fixatives) are accepted liquid sterilizing agents, provided that the immersion time is sufficiently long. To kill all spores in a clear liquid can take up to 22 hours with glutaraldehyde and even longer with formaldehyde. The presence of solid particles may lengthen the required period or render the treatment ineffective. Sterilization of blocks of tissue can take much longer, due to the time required for the fixative to penetrate. Glutaraldehyde and formaldehyde are volatile, and toxic by both skin contact and inhalation. Glutaraldehyde has a short shelf life (<2 weeks), and is expensive. Formaldehyde is less expensive and has a much longer shelf life if some methanol is added to inhibit polymerization to paraformaldehyde, but is much more volatile. Formaldehyde is also used as a gaseous sterilizing agent; in this case, it is prepared on-site by depolymerization of solid paraformaldehyde. Many vaccines, such as the original Salk polio vaccine, are sterilized with formaldehyde.

Hydrogen peroxide[edit]

Hydrogen peroxide, in both liquid and as vaporized hydrogen peroxide (VHP), is another chemical sterilizing agent. Hydrogen peroxide is strong oxidant, which allows it to destroy a wide range of pathogens. Hydrogen peroxide is used to sterilize heat or temperature sensitive articles such as rigid endoscopes. In medical sterilization hydrogen peroxide is used at higher concentrations, ranging from around 35% up to 90%. The biggest advantage of hydrogen peroxide as a sterilant is the short cycle time. Whereas the cycle time for ethylene oxide may be 10 to 15 hours, some modern hydrogen peroxide sterilizers have a cycle time as short as 28 minutes.[33]

Drawbacks of hydrogen peroxide include material compatibility, a lower capability for penetration and operator health risks. Products containing cellulose, such as paper, cannot be sterilized using VHP and products containing nylon may become brittle.[34] The penetrating ability of hydrogen peroxide is not as good as ethylene oxide[citation needed] and so there are limitations on the length and diameter of lumens that can be effectively sterilized and guidance is available from the sterilizer manufacturers. Hydrogen peroxide is primary irritant and the contact of the liquid solution with skin will cause bleaching or ulceration depending on the concentration and contact time. It is relatively non-toxic when diluted to low concentrations, but is a dangerous oxidizer at high concentrations (> 10% w/w). The vapor is also hazardous, primarily affecting the eyes and respiratory system. Even short term exposures can be hazardous and NIOSH has set the Immediately Dangerous to Life and Health Level (IDLH) at 75 ppm,[25] less than one tenth the IDLH for ethylene oxide (800 ppm). Prolonged exposure to lower concentrations can cause permanent lung damage and consequently OSHA has set the permissible exposure limit to 1.0 ppm, calculated as an 8-hour time weighted average.[35] Sterilizer manufacturers go to great lengths to make their products safe through careful design and incorporation of many safety features, though there are still workplace exposures of hydrogen peroxide from gas sterilizers are documented in the

FDA MAUDE database.[36] When using any type of gas sterilizer, prudent work practices will include good ventilation, a continuous gas monitor for hydrogen peroxide and good work practices and training.[37][38]

Vaporized hydrogen peroxide (VHP) is used to sterilize large enclosed and sealed areas such as entire rooms and aircraft interiors.

Peracetic acid[edit]

Peracetic acid (0.2%) is a recognized sterilant by the FDA[39] for use in sterilizing medical devices such as endoscopes.

Potential for chemical sterilization of prions[edit]

Prions are highly resistant to chemical sterilization. Treatment with aldehydes such as formaldehyde have actually been shown to increase prion resistance. Hydrogen peroxide (3%) for one hour was shown to be ineffective, providing less than 3 logs (10−3) reduction in contamination. Iodine, formaldehyde, glutaraldehyde and peracetic acid also fail this test (one hour treatment). Only chlorine, phenolic compounds, guanidinium thiocyanate, and sodium hydroxide (NaOH) reduce prion levels by more than 4 logs; chlorine (too corrosive to use on certain objects) and NaOH are the most consistent. Many studies have shown the effectiveness of sodium hydroxide.[40]

Radiation sterilization[edit]

Sterilization can be achieved using electromagnetic radiation such as electron beams, X-rays, gamma rays, or irradiation by subatomic particles.[41] Electromagnetic or particulate radiation can be energetic enough to ionize atoms or molecules (ionizing radiation), or less energetic (non-ionizing radiation).

Non-ionizing radiation sterilization[edit]

Ultraviolet light irradiation (UV, from a germicidal lamp) is useful for sterilization of surfaces and some transparent objects. Many objects that are transparent to visible light absorb UV. UV irradiation is routinely used to sterilize the interiors of biological safety cabinets between uses, but is ineffective in shaded areas, including areas under dirt (which may become polymerized after prolonged irradiation, so that it is very difficult to remove). It also damages some plastics, such as polystyrene foam if exposed for prolonged periods of time.

Further information: Ultraviolet germicidal irradiation

Ionizing radiation sterilization[edit]

Efficiency illustration of the different radiation technologies (electron beam, X-ray, gamma rays)

The safety of irradiation facilities is regulated by the United Nations International Atomic Energy Agency and monitored by the different national Nuclear Regulatory Commissions. The incidents that have occurred in the past are documented by the agency and thoroughly

analyzed to determine root cause and improvement potential. Such improvements are then mandated to retrofit existing facilities and future design.

Gamma radiation is very penetrating, and is commonly used for sterilization of disposable medical equipment, such as syringes, needles, cannulas and IV sets, and food. It is emitted by a radioisotope, usually Cobalt-60(60Co) or caesium-137 (137Cs).

Use of a radioisotope requires shielding for the safety of the operators while in use and in storage. With most designs the radioisotope is lowered into a water-filled source storage pool, which absorbs radiation and allows maintenance personnel to enter the radiation shield. One variant keeps the radioisotope under water at all times and lowers the product to be irradiated into the water towards the source in hermetic bells; no further shielding is required for such designs. Other uncommonly used designs use dry storage, providing movable shields that reduce radiation levels in areas of the irradiation chamber. An incident in Decatur Georgia, US, where water-soluble caesium-137 leaked into the source storage pool, requiring NRC intervention[42] has led to use of this radioisotope being almost entirely discontinued in favour of the more costly, non-water-soluble cobalt-60. Cobalt-60 gamma photons have about twice the energy, and hence greater penetrating range, of Caesium-137 radiation.Electron beam processing is also commonly used for sterilization. Electron beams use an on-off technology and provide a much higher dosing rate than gamma or x-rays. Due to the higher dose rate, less exposure time is needed and thereby any potential degradation to polymers is reduced. A limitation is that electron beams are less penetrating than either gamma or x-rays. Facilities rely on substantial concrete shields to protect workers and the environment from radiation exposure.X-rays: high-energy X-rays (produced by bremsstrahlung) allow irradiation of large packages and pallet loads of medical devices. They are sufficiently penetrating to treat multiple pallet loads of low-density packages with very good dose uniformity ratios. X-ray sterilization does not require chemical or radioactive material: high-energy X-rays are generated at high intensity by an X-ray generator that does not require shielding when not in use. X-rays are generated by bombarding a dense material (target) such as tantalum or tungsten with high-energy electrons in a process known as bremsstrahlung conversion. These systems are energy-inefficient, requiring much more electrical energy than other systems for the same result.Irradiation with X-rays or gamma rays, electromagnetic radiation rather than particles, does not make materials radioactive. Irradiation with particles may make materials radioactive, depending upon the type of particles and their energy, and the type of target material: neutrons and very high-energy particles can make materials radioactive, but have good penetration, whereas lower energy particles (other than neutrons) cannot make materials radioactive, but have poorer penetration.Sterilization by irradiation with gamma rays may however in some cases affect material properties.[43]Irradiation is used by the United States Postal Service to sterilize mail in the Washington, D.C. area. Some foods (e.g. spices, ground meats) are sterilized by irradiation.

Sterile filtration

Fluids that would be damaged by heat, irradiation or chemical sterilization, such as drug products, can be sterilized by microfiltration using membrane filters. This method is commonly used for heat labile pharmaceuticals and protein solutions in medicinal drug processing. A microfilter with pore size 0.2 µm will usually effectively remove microorganisms.[44] In the processing of biologics, viruses must be removed or inactivated, requiring the use of nanofilters with a smaller pore size (20 -50 nm) are used.

Smaller pore sizes lower the flow rate, so in order to achieve higher total throughput or to avoid premature blockage, pre-filters might be used to protect small pore membrane filters.

Membrane filters used in production processes are commonly made from materials such as mixed cellulose ester or polyethersulfone (PES). The filtration equipment and the filters themselves may be purchased as pre-sterilized disposable units in sealed packaging, or must be sterilized by the user, generally by autoclaving at a temperature that does not damage the fragile filter membranes. To ensure proper functioning of the filter, the membrane filters are integrity tested post-use and sometimes before use. The non-destructive integrity test assures the filter is undamaged, and is a regulatory requirement.[45] Typically, terminal pharmaceutical sterile filtration is performed inside of a cleanroom to prevent contamination.