anatomy and physiology of heart, lung ,
DESCRIPTION
anatomy and physiologyTRANSCRIPT
ANATOMY AND PHYSIOLOGY OF HEART, LUNG ,THORACIC CAVITY, BLOODVESSELS
LOCATION OF THE HEART
It is about 12 cm long, 9 cm wide at its broadest point, and 6 cm thick, with an average mass of 250 g (8 oz) in adult females and 300 g (10 oz) in adult males. The heart rests on the diaphragm, near the midline of the thoracic cavity. It lies in the mediastinum. About two-thirds of the mass of the heart lies to the left of the body’s midline . The pointed apex is directed anteriorly, inferiorly, and to the left. The broad base is directed posteriorly, superiorly, and to the right.
PERICARDIUM
The membrane that surrounds and protects the heart is the peri cardium . It confines the heart to its position in the mediastinum, while allowing sufficient freedom of move ment for vigorous and rapid contraction. The pericardium con sists of two main parts: the fibrous pericardium and the serous pericardium.
LAYERS OF THE HEART WALL
The wall of the heart consists of three layers: the epicardium , the myocardium, and the endocardium . The epicardium, the thin, transparent outer layer of the heart wall, is also called the visceral layer of the serous pericardium. It Is composed of mesothelium and delicate connective tissue .The middle myocardium , which is cardiac muscle tissue, makes up the bulk of the heart and is re sponsible for its pumping action.
The innermost endocardium is a thin layer of endothelium overlying a thin layer of connective tissue. It provides a smooth lining for the chambers of the heart and covers the valves of the heart. The endocardium is continuous with the endothelial lining of the large blood vessels attached to the heart
CHAMBERS OF THE HEART
The heart has four chambers. The two superior chambers are the atria , and the two inferior chambers are the ventricles . On the anterior surface of each atrium is a wrinkled pouchlike structure called an auricle. Also on the surface of the heart are a series of grooves, called sulci, that contain coronary blood vessels and a vari able amount of fat. Each sulcus marks the external boundary between two chambers of the heart. The deep coro nary sulcus encircles most of the heart and marks the boundary between the superior atria and
inferior ventricles. The anterior interventricular sulcus is a shallow groove on the anterior surface of the heart that marks boundary between the right and left ventricles. This sulcus continues around to the posterior surface of the heart as the posterior interventricular sulcus, which marks the boundary between the ventricles on the posterior aspect of the heart
RIGHT ATRIUM
The right atrium receives blood from three veins: the superior vena cava, inferior vena cava, and coronary sinus. The anterior and posterior walls of the right atrium are very different. The posterior wall is smooth; the anterior wall is rough due to the presence of muscular ridges called pectinate muscles which also extend into the auricle . Between the right atrium and left atrium is a thin partition called the interatrial septum . A prominent feature of this septum is an oval depression called the fossa ovalis, the remnant of the foramen ovale, an opening in the in- tera-trial septum of the fetal heart that normally closes soon after birth . Blood passes from the right atrium into the right ventricle through a valve that is called the tricuspid valve because it consists of three leaflets or cusps . It is also called the right atrioventricular valve. The valves of the heart are composed of dense connective tissue covered by endo cardium.
RIGHT VENTRICLE
The right ventricle forms most of the anterior surface of the heart. The inside of the right ventricle contains a series of ridges formed by raised bundles of cardiac muscle fibers called trabeculae carneae . The cusps of the tricuspid valve are connected to tendon like cords, the chordae tendineae, which in turn are connected to cone- shaped trabeculae carneae called papillary muscles. The right ventricle is separated from the left ventricle by a partition called the interventricular septum. Blood passes from the right ventricle through the pulmonary valve into a large_artery called the pulmonary trunk, which divides into right and left pulmonaryarteries.
LEFT ATRIUM
Left atrium forms the most of the base of the heart. It receives blood from the lungs through four pulmonary veins. Like tghe right atrium, the inside of the left atrium has smooth posterior wall.anterior wall also smooth. Blood passes from the left atrium to the left ventricle through the bicuspid valve.it is also called as the left atrioventricular valve.
LEFT VENTRICLE
The left ventricle forms the apex of the heart.like the right ventricle, the left ventricle contain trabeculae carnae and has cordae tendinae that anchor the cusps of the bicuspid valve to the papillary muscles.
Blood passes from the left ventricle through the aortic valve into the ascending aorta.
Some of the blood in the aorta flows into the coronary arteries, which branch from the ascending aorta and carry blood to the heart wall. The remainder of the blood passes into the arch of the aorta and descending aorta (thoracic aorta and abdominal aorta). Branches of the arch of the aorta and de scending aorta carry blood throughout the body.
HEART VALVES
As each chamber of the heart contracts, it pushes a volume of blood into a ventricle or out of the heart into an artery. Valves open and close in response to pressure changes as the heart con tracts and relaxes. Each of the four valves helps ensure the one way flow of blood by opening to let blood through and then closing to prevent its backflow.
SYSTEMIC AND PULMONARY CIRCULATIONS
The left side of the heart is the pump for the systemic circulation.it receives oxygenated blood from the lungs.the left ventricle ejects blood into the aorta. From the aorta, the blood devides into separate small streams, entering progressively smaller systemic arteries that carry it to all organs throughout the body- except for the air sacs of the lung , which is supplied by the pulmonary circulation
In systemic tissues , arteries give rise to smaller- diameter arterioles, which finally lead in to the extensive beds of systemic capillaries. Exchange of nutrients and gases occurs across the thin capillary walls. Blood unloads o2 and picks up co2 . In most cases blood flows through only one capillary and then enters systemic venule. Venules carry deoxygenated blood away from tissues and merge to form larger systemic veins. Ultimately the blood flows back to the right atrium
The right side of the heart is the pump for the pulmonary circulation; it receives all the dark red, deoxygenated blood returning from the systemic circulation. Blood ejected from the right ventricle flows into the pulmonary trunk, which branches into pulmonary arteries that carry blood to the right and left lungs. In pulmonary capillaries, blood unloads CO,, which is exhaled, and picks up inhaled 02. The freshly oxygenated blood then flows into pulmonary veins and returns to the left atrium
CORONARY CIRCULATION Nutrients are not able to diffuse quickly enough
front blood in the chambers of the heart to supply all the layers of cells that make up the heart wall. For this reason, the myocardium has its own network of blood vessels, the coronary or cardiac circulation. The coronary arteries branch from the ascending aorta and encircle the heart like a crown encircles the head . While the heart is contracting, little blood flows in the coronary arteries because they are squeezed shut. When the heart relaxes, however, the high pressure of blood in the aorta propels blood through the coronary arteries, into capil laries, and then into coronary veins .
CORONARY CIRCULATION
Heart is supplied by TWO CORONARY arteries:
1- Right coronary artery---(RCA) 2- Left coronary artery---(LCA) These coronary arteries arise at the root of
the aorta.
19
Coronary artery & their branches
LCA---- -Lt Anterior Descending (LAD) -Marginal Artery -Circumflex Artery RCA ---- -Marginal Artery -Posterior descending
branch
20
Left coronary artery (LCA) –Divides inAnterior Descending (LAD)
Circumflex artery LAD--- Supplies anterior and apical parts of
heart ,and Anterior 2/3rd of interventricular septum.
Circumflex branch-- supplies the lateral and posterior surface of heart.
21
Right coronary artery(RCA) supplies: Right ventricle Part of interventricular septum (posterior
1/3rd) Inferior part of left ventricle AV Node
22
Coronary circulation
23
After blood passes through the arteries of the coronary circula tion, it flows into capillaries, where it delivers oxygen and nutri ents to the heart muscle and collects carbon dioxide and waste, and then moves into coronary veins. Most of the deoxygenated blood from the myocardium drains into a large vascular sinus in the coronary sulcus on the posterior surface of the heart, called the coronary sinus . The deoxygenated blood in the coronary sinus empties into the right atrium.
Blood flow to Heart during Systole & Diastole
During systole when heart muscle contracts it compresses the coronary arteries therefore blood flow is less to the left ventricle during systole and more during diastole.
To the subendocardial portion of Left ventricle it occurs only during diastole
25
Blood flow to subendocardial surface of left ventricle during systole is not there, therefore, this region is prone to ischemic damage and most common site of Myocardial infarction.
26
Venous return of Heart
Most of the venous blood return to heart occurs through the coronary sinus and anterior cardiac veins, which drain into the right atrium
27
CORONARY VEINS
After blood passes through the arteries of the coronary circula tion, it flows into capillaries, where it delivers oxygen and nutri ents to the heart muscle and collects carbon dioxide and waste, and then moves into coronary veins. Most of the deoxygenated blood from the myocardium drains into a large vascular sinus in the coronary sulcus on the posterior surface of the heart, called the coronary sinus . The deoxygenated blood in the coronary sinus empties into the right atrium. The principal tributaries carrying blood into the coronary sinus are the following:
Great cardiac vein in the anterior interventricular sulcus, which drains the areas of the heart supplied by the left coro nary artery (left and right ventricles and left atrium)
Middle cardiac vein in the posterior interventricular sulcus, which drains the areas supplied by the posterior interventric ular branch of the right coronary artery (left and right ventri cles)
Small cardiac vein in the coronary sulcus, which drains the right atrium and right ventricle
Anterior cardiac veins, which drain the right ventricle and open directly into the right atrium
When blockage of a coronary artery deprives the heart mus cle of oxygen, reperfusion, the reestablishment of blood flow, may d
CORONARY BLOOD FLOW Coronary blood flow in Humans at rest is
about 225-250 ml/minute, about 5% of cardiac output.
At rest, the heart extracts 60-70% of oxygen from each unit of blood delivered to heart [other tissue extract only 25% of O2.
30
CORONARY BLOOD FLOWWhy heart is extracting 60-70% of O2? Because heart muscle has more
mitochondria, up to 40% of cell is occupied by mitochondria, which generate energy for contraction by aerobic metabolism, therefore, heart needs O2.
When more oxygen is needed e.g. exercise, O2 can be increased to heart only by increasing blood flow.
31
Factors Affecting Blood Flow to CORONARY ARTERIES
-Pressure in aorta -Chemical factors -Neural factors
Coronary blood flow shows considerable Autoregulation.
32
Chemical factors affecting Coronary blood flow
Chemical factors causing Coronary vasodilatation (Increased coronary blood flow) -Lack of oxygen -Increased local concentration of Co2
-Increased local concentration of H+ ion -Increased local concentration of k + ion -Increased local concentration of Lactate,
Prostaglandin, Adenosine, Adenine nucleotides.
NOTE – Adenosine, which is formed from ATP during cardiac metabolic activity, causes coronary vasodilatation.
33
CORONARY ARTERY HEART DISEASE
ISCHEMIC HEART DISEASE (IHD) (ANGINA PECTORIS) MYOCARDIAL INFARCTION
ANGINA PECTORIS: THERE IS REDUCED CORONARY ARTERY BLOOD FLOW DUE
TO ATHEROSCLEROSIS (CHOLESTROL DEPOSITION SUBENDOCARDIALLY -- Plaque)
34
Applied Aspect
THE C A D.
35
THE CONDUCTION SYSTEM An inherent and rhythmical electrical activity
is the reason for the heart’s lifelong beat. The source of this electrical activity is a net work of specialized cardiac muscle fibers called autorhythmic fibers because they are self-excitable. Autorhythmic fibers repeatedly generate action potentials that trigger heart contractions.
They act as a pacemaker, setting the rhythm of electrical excitation that causes contraction of the heart.
They form the conduction system, a network of specialized cardiac muscle fibers that provide a path for each cycle of car diac excitation to progress through the heart. The conduction system ensures that cardiac chambers become stimulated to con tract in a coordinated manner, which makes the heart an effec tive pump.
Cardiac action potentials propagate through the conduction system in the following sequence .
Cardiac excitation normally begins in the sinoatrial (SA) node, natural pacemaker located in the right atrial wall just inferior to the opening of the superior vena cava. SA node cells do not have a stable resting potential. Rather, they repeatedly depo larize to threshold spontaneously. The spontaneous depolar ization is a pacemaker potential. When the pacemaker po tential reaches threshold, it triggers an action potential. Each action potential from the SA node propagates throughout both atria via gap junctions in the intercalated discs of atrial muscle fibers. Following the action potential, the atria contract.
By conducting along atrial muscle fibres, the action poten tial reaches the atrioventricular (AV) node, located in the septum between the two atria, just anterior to the opening of the coronary sinus .
From the AV node, the action potential enters the atrioven tricular (AV) bundle (also known as the bundle of His). This bundle is the only site where action potentials can con duct from the atria to the ventricles. (Elsewhere, the fibrous skeleton of the heart electrically insulates the atria from the ventricles.)
After propagating along the AV bundle, the action potential enters both the right and left bundle branches. The bundle branches extend through the interventricular septum toward the apex of the heart.
Finally, the large-diameter Purkinje fibers rapidly conduct the action potential from the apex of the heart upward to the remainder of the ventricular myocardium. Then the ventri cles contract, pushing the blood upward toward the semilu nar valves
CARDIAC CYCLE
term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the next. The frequency of the cardiac cycle is described by the heart rate
THE CARDIAC CYCLE
In each cariac cycle, the atria and ventricles alternately contract and relax, forcing blood from areas of lower pressure. As a chamber of the heart contracts , blood pressure within it increases. Pressure of the right is lower than that of the left. Each ventricle , hoeever , expels the same volume of blood per beat, and the same pattern exist for both the chambers. When hart rate is 75beats /min , a cardiac cycle lasts 0.8 sec. To examine and correlate the events taking place during a cardiac cycle.
The first stage, "early diastole," is when the semilunar valves close, the atrioventricular (AV) valves are open, and the whole heart is relaxed. The second stage, "atrial systole," is when the atrium contracts, and blood flows from atrium to the ventricle. The third stage, "isovolumic contraction" is when the ventricles begin to contract, the AV and semilunar valves close, and there is no change in volume. The fourth stage, "ventricular ejection," is when the ventricles are contracting and emptying, and the semilunar valves are open.
. During the fifth stage, "isovolumic relaxation time", pressure decreases, no blood enters the ventricles, the ventricles stop contracting and begin to relax, and the semilunar valves close due to the pressure of blood in the aorta.
Throughout the cardiac cycle, blood pressure increases and decreases. The cardiac cycle is coordinated by a series of electrical impulses that are produced by specialized heart 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). Under normal circumstances, each cycle takes 0.8 seconds
. Each beat of the heart involves five major stages. The first two stages, often considered together as the "ventricular filling" stage, involve the movement of blood from the atria into the ventricles. The next three stages involve 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).
Atrial systole Systole , which lasts about 0.1 sec, the atria are
contracting. At the same time, the ventricles are relaxed. Depolarisation of the SA node causes atrial
depolarisation, marked by the P wave in the ECG. Atrial depolarisation causes atrial systole . as the atria
contracts , they exrt pressure on the blood within , which forces blood through the open AV valves into the ventricles.
Atrial systole contributes a final 25 mL of blood to the volume already in each ventricle the end of atrial systole is also end of ventricular diastole. Thus each ventricle contain about 130mLat the end of its relaxation period(diastole) .This blood volume is called the end- diastolic volume.(EDV)
Ventricular systole During ventricular systole which last about 0.3sec
the ventricles are contracting. At the same , the atria are relaxed, in atrial diastole.
5. Ventricular depolarisation causes ventricular systole. As ventricular systole begins , pressure rise inside the ventricles and pushes blood up against the AV valves , forcing them shut for about 0.05 seconds , both the SL and AV valves are closed this is the period of isometric contraction . During this interval cardiac musclefibres are contracting and exerting force but are not shortening. Thus the muscle contraction is uiso metric . moreover , because all four valves are closed, the ventricular volume remains the same( isovolumic)
. Continued contraction of the ventricles cause pressure inside the chambers to rise sharply. when left ventricular pressure surpasses the aortic pressure at about 80 mmHg and the right ventricular pressure rises above the pressure in the pulmonary trunk(about 20 mmHg), both SLs are open is ventricular ejection and lasts for about 0.24 sec. The pressure in the left ventricle continues to rise to about 120mmHg, where as pressure in the the right ventricle climbs to about 25-30mmHg.
The left ventricle ejects about 70mLof blood into the aorta and right ventricle and ejects the same volume of blood into the pulmonary trunk. The voume remaining in each ventricle at the end of the systole, about 60mL, is the end systolic volume(ESV). Stroke volume , the volume ejectedper beat fro each ventricle, equals end- diastolic volume minus end systolic volume.SV=EDV-ESV. At rest, the stroke volume is about 130mL-60mL=70 mL
The T wave in the ECG marks the onset of ventricular repolarisation
CARDIAC OUTPUT
Cardiac output (CO) is the volume of blood ejected from the left ventricle (or the right ventricle) into the aorta (or pul monary trunk) each minute. Cardiac output equals the stroke volume (SV), the volume of blood ejected by the ventricle dur ing each contraction, multiplied by the heart rate (HR), the number of heartbeats per minute:
CO = SV X HR
REGULATION OF STROKE VOLUME
A healthy heart will pump out the blood that entered its chambers during the previous diastole. In other words, if more blood re turns to the heart during diastole, then more blood is ejected dur ing the next systole. At rest, the stroke volume is 50-60% of the end-diastolic volume because 40-50% of the blood remains in the ventricles after each contraction (end-systolic volume). Three factors regulate stroke volume and ensure that the left and right ventricles pump equal volumes of blood: (1) preload, the degree of stretch on the heart before it contracts; (2) contractility, the forcefulness of contraction of individual ventricular muscle fibers; and (3) afterload, the pressure that must be exceeded before ejection of blood from the ventricles can occur.
Preload: Effect of Stretching A greater preload (stretch) on cardiac muscle
fibers prior to con traction increases their force of contraction. Preload can be com pared to the stretching of a rubber band. The more the rubber band is stretched, the more forcefully it will snap back. Within limits, the more the heart fills with blood during diastole, the greater the force of contraction during systole. This relationship is known as the Frank-Starling law of the heart. The preload is proportional to the end-diastolic volume
Contractility The second factor that influences stroke volume is myocardial
contractility, the strength of contraction at any given preload. Substances that increase contractility are positive inotropic agents; those that decrease contractility are negative inotropic agents.Thus, for a constant preload, the stroke volume increases when a positive inotropic substance is present. Positive inotropic agents often promote Ca2+ inflow during cardiac action potentials, which strengthens the force of the next contraction. Stimulation of the sympathetic division of the autonomic nervous system (ANS), hormones such as epinephrine and norepinephrine, increased Ca2+ level in the interstitial fluid, and the drug digitalis all have positive inotropic effects. In contrast, inhibition of the sympathetic divi sion of the ANS, anoxia, acidosis, some anesthetics, and increased K+ level in the interstitial fluid have negative inotropic effects. Calcium channel blockers are drugs that can have a negative in otropic effect by reducing Ca2+ inflow, thereby decreasing the strength of the heartbeat.
AFTER LOAD Ejection of blood from the heart begins when
pressure in the right ventricle exceeds the pressure in the pulmonary trunk (about 20 mmHg), and when the pressure in the left ventricle ex ceeds the pressure in the aorta (about 80 mmHg). At that point, the higher pressure in the ventricles causes blood to push the semilunar valves open. The pressure that must be overcome be fore a semilunar valve can open is termed the afterload. An in crease in afteiload causes stroke volume to decrease, so ^ more blood remains in the ventricles at the end of systol^ Conditions that can increase afterload include hypertension (eie vated blood pressure) and narrowing of arteries by atherosclerosis
REGULATION OF HEART RATE
Cardiac output depends on both heart rate and stroke volume. Adjustments in heart rate are important in the short-term control of cardiac output and blood pressure. The sinoatrial (SA) node initiates contraction and, if left to itself, would set a constant heart rate of about 100 beats/min. However, tissues require different volumes of blood flow under different conditions. During exercise, for example, cardiac output rises to supply working tissues with increased amounts of oxygen and nutrients. Stroke volume may fall if the ventricular myocardium is damaged or if blood volume is reduced by bleeding. In these cases, homeostatic mechanisms maintain adequate cardiac output by increasing the heart rate and contractility. Among the several factors that contribute to regulation of heart rate, the most impor tant are the autonomic nervous system and hormones released by the adrenal medullae (epinephrine and norepinephrine).
AUTONOMIC REGULATION OF HEART RATE
Nervous system regulation of the heart originates in the cardio vascular centre in the medulla oblongata. This region of the brain stem receives input from a variety of sensory receptors and from higher brain centres, such as the limbic system and cere bral cortex. The cardiovascular centre then directs appropriate output by increasing or decreasing the frequency of nerve im pulses in both the sympathetic and parasympathetic branches of the ANS .
DETERMINANTS OF BP AND REGULATION
These are the fundamental factors which determine the value of BP. They are 1. Cardiac output2.peripheral vascular resistance these are also called as factors controlling BP.
BP= cardiac outputperipheral resistance Regulation of BP means physiological
mechanism by which BP homeostasis is maintained. Two types of regulatory mechanisms are there.
1) Short term: Short term regulations are achieved by neural regulations where as long term regulations are achieved by controlling blood volume and Na retension via renal mechanisms.
Nervous SystemControl :BP by changing blood distribution in the body and by changing blood vessel diameter. Sympathetic & Parasympathetic activity will affects veins, arteries & heart to control HR and force of contraction .The vasomotor center cluster of sympathetic neurons found in the medulla.It sends efferent motor fibers that innervate smooth muscle of blood vessels.
.
SHORT-TERM REGULATION OF RISING BLOOD
Pressure :Rising blood pressure Stretching of arterial walls .Stimulation of baroreceptors in carotid sinus, aortic arch, and other large arteries of the neck and thorax Increased impulses to the brain
Baroreceptors :The best known of nervous mechanisms for arterial pressure control (baroreceptor reflex)Baroreceptors are stretch receptors found in the carotid body, aortic body and the wall of all large arteries of the neck and thorax. Respond progressively at 60-180 mm Hg.Respond more to a rapidly changing pressure than stationary pressure.
.
Effect of Baroreceptors :Baroreceptors entered the medulla (tractussolitarius)Secondary signals inhibit the vasoconstrictor center of medulla and excite the vagal parasympathetic center effect vasodilatation of the veins and arterioles decreased heart rate and strength of heart contractiontherefore, excitation of baroreceptors by high pressure in the arteries reflexly causes arterial pressure to decrease (as decrease in PR and CO) Conversely, low pressure has opposite effects,reflexly causing the pressure rise back to normal
Increased Parasympathetic Activity: Effect of increased parasympathetic and decreased sympathetic activity on heart and blood pressure: Increased activity of vagus (parasympathetic) nerve .Decreased activity of sympathetic cardiac Nerves Reduction of heart rate .Lower cardiac output .Lower blood pressure
Decreased Sympathetic Activity Effect of decreased sympathetic activity on arteries and blood pressure: Decreased activity of vasomotor fibers (sympathetic nerve fibers)Relaxation of vascular smooth muscle.Increased arterial diameterLower blood pressure
2)
Long term:long term control is achieved by adjusting the blood volume and lowering Ca concentration in the VSM.
Hormones :1)ADH reduces water excreation and causes water conservation.2) Renin ultimately cause production of angiotensin II causes aldosterone production which leads to the water and sodium retension.
ANP:released when atria are stretched . it causes dieresis and reduce blood volume and BP.
Role of Ca ions in the VSM : Its accumulation causes rise in the vascular tone and increases the vascular tone
ANATOMY & PHYSIOLOGY OF LUNG
STRUCTURE OF THE RESPIRATORY SYSTEM
The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, and lungs. Structurally, the respiratory system consists of two portions [1] the term upper respiratory system refers to the nose, pharynx, and associated structures. [2] The lower respiratory system refers to the larynx, trachea, bronchi, and lungs.
. Functionally, the respiratory system also consists of two portions. [1] The conducting portion consists of a series of interconnecting cavities and tubes-nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles-that conduct air in to the lungs.[2] the respiratory portion consists of those portions of the respiratory system where the exchange of gases occurs-respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli
RESPIRATORY SYSTEM
upper respiratory system -nose, pharynx & associated structures.
lower respiratory system – larynx,trachea,bronchi & lungs.
TRACHEA/WIND PIPE
12 cm long, 2.5 cm in diameter. Located anterior to esophagus and extends from the larynx to the superior border of the 5th thoracic vertebra, where it divides into right & left primary bronchi.
layers of trachea [ deep to superficial]- mucosa, submucosa, hyaline cartilage and adventitia[composed of areolar connective tissue].
supported by 16-20, C-shaped rings of hyaline cartliage.
The open part of ‘C’ faces posteriorly, where it is spanned by a smooth muscle- trachealis.
The gap in the ‘C’ allows room for the esophagus to expand as swallowed food passes by.
At the point where the trachea divides into right & left primary bronchi, there is an internal ridge called carina, it is the most sensitive part for triggering a cough reflex.
BRONCHI
At superior border of thoracic vertebra, trachea divides into right & left primary bronchi.
Right bronchus is more vertical, shorter and wider than the left. As a result aspirated object is more likely to enter & lodge in the right primary bronchus than left.
On entering the lungs, primary bronchi divide to form secondary [lobar ] bronchi, one for each lobe of the lung. [right has 3 & left has 2 lobes].
BRONCHIAL TREE
secondary bronchi
tertiary[ segmental] bronchi
bronchioles
terminal bronchioles
respiratory bronchioles
CONTD..
alveolar ducts alveolar sacs[ grape like clusters of
alveoli]
TERMINAL BRONCHIOLES
LUNGS
essential organs of respiration, two in number, placed on either side within the thorax, separated by mediastinum
conical organ, with broad concave base resting on the diaphragm& a blunt peak called the apex, projecting slightly superior to the clavicle.
PARTS OF THE LUNG
Each lung has an apex,base,3 borders and 2 surfaces.
has mediastinal & costal surface[ two surfaces].
costal surface- broad and pressed against the rib cage.
mediastinal surface- smaller, concave and faces medially.
Apex[apex pulmonis]-rounded & extends to the root of the neck[2.5-4cm above the level of sternal end of first rib]
The base[basis pulmonis]- is broad, concave & rest on the convex surface of diaphragm.
borders- inferior border, posterior border & anterior border.
inferior border- separates the base from the costal surface .
posterior border- is broad & rounded& is received into the deep concavity on either side of the vertebral column.
anterior border- thin& sharp, and overlaps the front of pericardium.
STRUCTURE OF THE LUNG composed of an external serous coat, a subserous
areolar tissue & the pulmonary substance[parenchyma].
serous coat- is the pulmonary pleura ; it is thin, transparent.
subserous pleura- contains a large proportion of elastic fibers.
the parenchyma- is composed of secondary lobules, which are connected by interlobular areolar tissue.
each secondary lobule – is composed of several primary lobules[ the anatomical unit of the lung].
primary lobule- consists of an alveolar duct, the air spaces connected with it & their blood vessels,lymphatics and nerves.
VESSELS AND NERVES OF THE LUNGS
Bronchial arteries- supply blood for the nutrition the lungs; they derived from the thoracic aorta or from the the upper aortic intercostal arteries.
pulmonary artery- conveys the venous blood to the lungs; it divides & redivides to form a dense capillary network in the walls of the alveoli. In the septa between the alveoli the capillary network forms a single layer.
pulmonary vein- commence in the pulmonary capillaries& enter into larger ranches.
Bronchial vein- is formed at the root of the lung and ends on the right side in the azygous vein , & on the left side in the highest intercostal or in the accessory hemiazygous vein.
LUNGS
right lung- three lobes;- superior, middle, inferior. Two fissures.[oblique and horizontal]
left lung- little smaller than right, cardiac impression, two lobes-superior& inferior, one fissure[oblique fissure].
Hilum- a roughly triangular shaped slit in the mediastinal surface through which bronchus, blood vessels, lymphatics& nerves pass. It constitutes the root of the lung
BRONCHO PULMONARY SEGMENTS
ALVEOLI
alveolus- is a pouch about 0.2-0.5 mm in diameter.
Its wall consists predominantly of squamous [type 1] alveolar cells-thin cells that allow for rapid gas diffusion between the alveolus & bloodstream; about 5% of the alveolar cells are round to cuboidal great [type 2] alveolar cells
type 2 alveolar cells- secrete a detergent-like lipoprotein called pulmonary surfactant, which form a thin film on the insides of the alveoli & bronchioles.
Alveolar macrophages[dust cells]- wander the lumen of the alveoli & the connective tissue between them.
Each alveolus is surrounded by a basket of blood capillaries supplied by the pulmonary artery. The barrier between the alveolar air and blood , called the respiratory membrane; consists only of the squamous type1 alveolar cell, the squamous endothelial cell of the capillary, and their fused basement membranes. These have a total thickness of only o.5 µm.
THE PLEURAE
visceral pleurae- serous membrane covering the surface of the lung.
parietal pleura- outer surface. pleural cavity- space b/w visceral & parietal
pleurae. functions- reduction of friction, creation of
pressure gradient, compartmentalization.
PHYSIOLOGY OF RESPIRATION
inspiration- breathing in.. principle inspiratory muscles- the diaphragm
& external intercostals. stimulation of diaphragm by the phrenic
nerve
diaphragm becomes tenses & flattens
this enlarges the thoracic cavity& reduces its internal pressure
this force air in to the lungs other muscles also help-the scalenes fix the
first pair of ribs while the external intercostal muscle lift the remaining ribs like bucket handles, making them swing up and out- this also forces air into the lungs.
deep inspiration – is aided by the pectoralis minor, sternocleidomastoid, and erector spinae muscles.
expiration- passive process . It is achieved by the elasticity of the lungs and the thoracic cage- i.e., the tendency to return to their original dimensions when released from tension.
pause- when inspiration ceases, the phrenic nerves continue to stimulate the diaphragm for a little longer; it makes the transition from inspiration to expiration smoother.
LUNG VOLUMES AND CAPACITIES
Lung volumes and lung capacities refer to the volume of air associated with different phases of the respiratory cycle. Lung volumes are directly measured; Lung capacities are inferred from lung volumes.
The healthy adult averages 12 respirations a minute and moves about 6 liters of air into and out of the lungs while at rest.
CNTD..
tidal volume- the total amount of air moves into and out of the airways with each inspiration and expiration during normal quiet breathing. [vT][500ml]
About 150 mL of it (typically 1 mL per pound of body weight) fills the conducting division of the airway. Since this air cannot exchange gases with the blood, it is called dead air, and the conducting division is called the anatomic dead space.
Physiologic (total) dead space- is the sum of anatomic dead space and any pathological alveolar dead space that may exist. In healthy people, few alveoli are nonfunctional, and the anatomic and physiologic dead spaces are identical.
The total volume of air taken in during 1 minute is called the minute volume of respiration [MVR] or minute ventilation. It is calculated by multiplying the tidal volume by the normal breathing rate per minute.[500×12= 6000ml/mt].
The alveolar ventilation rate [AVR] is the volume of air per minute that reaches the alveoli.
Inspiratory reserve volume (IRV)[3,000 mL]:-Amount of air in excess of tidal inspiration that can be inhaled with maximum effort.
Expiratory reserve volume (ERV)[1,200 mL]:-Amount of air in excess of tidal expiration that can be exhaled with maximum effort.
Residual volume (RV)[1,300 mL]:-Amount of air remaining in the lungs after maximum expiration; keeps alveoli inflated between breaths and mixes with fresh air on next inspiration.
Vital capacity (VC)[4,700 mL]:-Amount of air that can be exhaled with maximum effort after maximum inspiration (TV + IRV + ERV); used to assess strength of thoracic muscles as well as pulmonary function.
Inspiratory capacity (IC)[3,500 mL]:-Maximum amount of air that can be inhaled after a normal tidal expiration (TV + IRV).
Functional residual capacity (FRC)[2,500 mL]:-Amount of air remaining in the lungs after a normal tidal expiration (RV + ERV)
Total lung capacity (TLC)[6,000 mL]:-Maximum amount of air the lungs can contain (RV + VC).
PATTERNS OF BREATHING
Apnea -Temporary cessation of breathing (one or more skipped breaths).
Dyspnea-Labored, gasping breathing; shortness of breath.
Eupnoea-Normal, relaxed, quiet breathing; typically 500 mL/breath, 12 to 15 breaths/min.
Hyperpnea -Increased rate and depth of breathing in response to exercise, pain, or other conditions.
Hyperventilation-Increased pulmonary ventilation in excess of metabolic demand, frequently associated with anxiety; expels C02 faster than it is produced, thus lowering the blood C02 concentration and raising the pH.
Hypoventilation-Reduced pulmonary ventilation; leads to an increase in blood C02 concentration if ventilation is insufficient to expel C02 as fast as it is produced.
Kussmaul-Deep, rapid breathing often induced by acidosis, as in diabetes mellitus.
Orthopnea -Dyspnea that occurs when a person is lying down.
Respiratory arrest-Permanent cessation of breathing (unless there is medical intervention).
Tachypnea -Accelerated respiration .
GAS EXCHANGE & TRANSPORT
External[pulmonary] respiration-It is the exchange of O2 and CO2 between air in the alveoli of the lungs and blood in pulmonary capillaries. It results in the conversion of deoxygenated blood coming from heart to oxygenated blood.
factors that affect the efficiency of alveolar gas exchange:-
concentration gradient of gases[ie, po2 & pco2]
Solubility of the gases Membrane area Ventilation-perfusion coupling.
Internal respiration-The exchange of oxygen and carbon dioxide between tissue blood capillaries and tissue cells called internal[tissue]respiration.it results in the conversion of oxygenated blood into deoxygenated blood.
Oxygenated blood entering tissue capillaries has a pO2 of 100 mm Hg, where as tissue cells have an average Po2 of 40 mm of Hg. Because of this difference , oxygen diffuses from the oxygenated blood through interstitial fluid and into tissue cells until the pO2 in the blood decreases to 40 mm of Hg
While oxygen diffuses from the tissue blood capillaries to tissue cells, carbon dioxide diffuses in the opposite direction.
GAS TRANSPORT 1. oxygen- The concentration of oxygen in arterial blood, by volume, is
about 20 mL/dL. About 98.5% of this is bound to hemo globin and 1.5% is dissolved in the blood plasma.
2. Carbon dioxide- a] About 90% of the CO2 is hydrated (reacts with water) to
form carbonic acid, which then dissociates into bicarbonate and hydrogen ions.
B] About 5% binds to the amino groups of plasma proteins and hemoglobin to form carbamino compounds—chiefly, carbaminohemoglobin (HbCO2).
c] The remaining 5% of the CO2 is carried in the blood as dissolved gas.
CONTROL OF RESPIRATION
There are four main centers in the brain to regulate the respiration:
1. Inspiratory center 2. Expiratory center 3. Pneumotaxic center 4. Apneustic center. The first two centers are
present on the medulla oblongata whereas the last two centers on the Pons region of brain.
THORACIC CAVITY
The thoracic cavity (or chest cavity) is the chamber of the human body (and other animal bodies) that is protected by the thoracic wall (thoracic cage and associated skin, muscle, and fascia).
The heart and lungs are situated in the thorax, the walls of which afford them protection. The heart lies between the two lungs, and is enclosed within a fibrous bag, the pericardium, while each lung is invested by a serous membrane, the pleura.
COMPONENTS
Structures within the thoracic cavity include: structures of the cardiovascular system,
including the heart and great vessels, which include the thoracic aorta, the pulmonary artery and all its branches, the superior and inferior vena cava, the pulmonary veins, and the azygos vein
structures of the respiratory system, including the trachea, bronchi and lungs
structures of the digestive system, including the esophagus,
endocrine glands, including the thymus gland,
structures of the nervous system including the paired vagus nerves, and the paired sympathetic chains,
lymphatics including the thoracic duct. It contains three potential spaces lined with
mesothelium: the paired pleural cavities and the pericardial cavity. The mediastinum comprises those organs which lie in the centre of the chest between the lungs
THE CAVITY OF THE THORAX
(1) the space enclosed by the lower ribs is occupied by some of the abdominal viscera; and (2) the cavity extends above the anterior parts of the first ribs into the neck. The size of the thoracic cavity is constantly varying during life with the movements of the ribs and diaphragm, and with the degree of distention of the abdominal viscera. From the collapsed state of the lungs as seen when the thorax is opened in the dead body, it would appear as if the viscera only partly filled the cavity, but during life there is no vacant space, that which is seen after death being filled up by the expanded lungs
THE UPPER OPENING OF THE THORAX The parts which pass through the upper opening of
the thorax are, from before backward, in or near the middle line, the Sternohyoideus and Sternothyreoideus muscles, the remains of the thymus, the inferior thyroid veins, the trachea, esophagus, thoracic duct, and the Longus colli muscles; at the sides, the innominate artery, the left common carotid, left subclavian and internal mammary arteries and the costocervical trunks, the innominate veins, the vagus, cardiac, phrenic, and sympathetic nerves, the greater parts of the anterior divisions of the first thoracic nerves, and the recurrent nerve of the left side. The apex of each lung, covered by the pleura, also projects through this aperture, a little above the level of the sternal end of the first rib.
THE LOWER OPENING OF THE THORAX.— The lower opening of the thorax is wider transversely
than from before backward. It slopes obliquely downward and backward, so that the thoracic cavity is much deeper behind than in front. The diaphragm closes the opening and forms the floor of the thorax. The floor is flatter at the center than at the sides, and higher on the right side than on the left; in the dead body the right side reaches the level of the upper border of the fifth costal cartilage, while the left extends only to the corresponding part of the sixth costal cartilage. From the highest point on each side the floor slopes suddenly downward to the costal and vertebral attachments of the diaphragm; this slope is more marked behind than in front, so that only a narrow space is left between the diaphragm and the posterior wall of the thorax.
BLOOD VESSELS
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart
ANATOMY The arteries and veins have three layers, but the middle
layer is thicker in the arteries than it is in the veins: Tunica intima (the thinnest layer): a single layer of
simple squamous endothelial cells glued by a polysaccharide intercellular matrix, surrounded by a thin layer of subendothelial connective tissue interlaced with a number of circularly arranged elastic bands called the internal elastic lamina.
Tunica media (the thickest layer in arteries): circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may (especially in arteries) be rich in vascular smooth muscle, which controls the caliber of the vessel.
Tunica adventitia: (the thickest layer in veins) entirely made of connective tissue. It also contains nerves that supply the vessel as well as nutrient capillaries (vasa vasorum) in the larger blood vessels.
Capillaries consist of little more than a layer of endothelium and occasional connective tissue.
When blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis (pl. anastomoses). Anastomoses provide critical alternative routes for blood to flow in case of blockages.
TYPES
Blood vessel with an erythrocyte (red blood cell, E) within its lumen, endothelial cells forming its tunica intima (inner layer), and pericytes forming its tunica adventitia (outer layer)
There are various kinds of blood vessels: Arteries
Aorta (the largest artery, carries blood out of the heart)
Branches of the aorta, such as the carotid artery, the subclavian artery, the celiac trunk, the mesenteric arteries, the renal artery and the iliac artery.
Arterioles
Capillaries (the smallest blood vessels) Venules Veins
Large collecting vessels, such as the subclavian vein, the jugular vein, the renal vein and the iliac vein.
Venae cavae (the two largest veins, carry blood into the heart).
They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from (arterial) or toward (venous) the heart. The term "arterial blood" is nevertheless used to indicate blood high in oxygen, although the pulmonary artery carries "venous blood" and blood flowing in the pulmonary vein is rich in oxygen. This is because they are carrying the blood to and from the lungs, respectively, to be oxygenated.
PHYSIOLOGY Blood vessels do not actively engage in the transport
of blood (they have no appreciable peristalsis), but arteries—and veins to a degree—can regulate their inner diameter by contraction of the muscular layer. This changes the blood flow to downstream organs, and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation.
Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95-100%) with oxygen. In all veins apart from the pulmonary vein, the hemoglobin is desaturated at about 75%. (The values are reversed in the pulmonary circulation.)
The blood pressure in blood vessels is traditionally expressed in millimetres of mercury (1 mmHg = 133 Pa). In the arterial system, this is usually around 120 mmHg systolic (high pressure wave due to contraction of the heart) and 80 mmHg diastolic (low pressure wave). In contrast, pressures in the venous system are constant and rarely exceed 10 mmHg.
Vasoconstriction is the constriction of blood vessels (narrowing, becoming smaller in cross-sectional area) by contracting the vascular smooth muscle in the vessel walls. It is regulated by vasoconstrictors (agents that cause vasoconstriction). These include paracrine factors (e.g. prostaglandins), a number of hormones (e.g. vasopressin and angiotensin) and neurotransmitters (e.g. epinephrine) from the nervous system.
Vasodilation is a similar process mediated by antagonistically acting mediators. The most prominent vasodilator is nitric oxide (termed endothelium-derived relaxing factor for this reason).
Permeability of the endothelium is pivotal in the release of nutrients to the tissue. It is also increased in inflammation in response to histamine, prostaglandins and interleukins, which leads to most of the symptoms of inflammation (swelling, redness, warmth and pain).
Thank you