Transportation in Humans

Systole: Contraction of cardiac muscles is called systole.

Diastole: Relaxation of cardiac muscles is called diastole.

Fig: Human HeartArteries: These are thick-walled blood vessels which carry oxygenated blood from the heart to different organs. Pulmonary arteries are exceptions because they carry deoxygenated blood from the heart to lungs; where oxygenation of blood takes place.

Veins: These are thin-walled blood vessels which carry deoxygenated blood from different organs to the heart. Pulmonary veins are exceptions because they carry oxygenated blood from lungs to the heart. Valves are present in veins to prevent backflow of blood.

Capillaries: These are the blood vessels which have single-celled walls.

Blood: Blood is a connective tissue which plays the role of the carrier for various substances in the body. Blood is composed of plasma, blood cells and platelets.

Blood Plasma: Blood plasma is a pale coloured liquid which is mostly composed of water. Blood plasma forms the matrix of blood.

Blood Cells: There are two types of blood cells, viz. Red Blood Cells (RBCs) and White Blood Cells (WBCs).

Red Blood Corpuscles (RBCs): These are of red colour because of the presence of haemoglobin which is a pigment. Haemoglobin readily combines with oxygen and carbon dioxide. The transport of oxygen happens through haemoglobin. Some part of carbon dioxide is also transported through haemoglobin.

White Blood Corpuscles (WBCs): These are of pale white colour. They play important role in the immunity.

Platelets: Platelets are responsible for blood coagulation. Blood coagulation is a defense mechanism which prevents excess loss of blood; in case of an injury.

Lymph: Lymph is similar to blood but RBCs are absent in lymph. Lymph is formed from the fluid which leaks from blood capillaries and goes to the intercellular spaces in the tissues. This fluid is collected through lymph vessels and finally returns to the blood capillaries. Lymph also plays an important role in the immune system.

Double Circulation: In the human heart, blood passes through the heart twice in one cardiac cycle. This type of circulation is called double circulation. One complete heart beat in which all the chambers of the heart contract and relax once is called cardiac cycle. The heart beats about 72 times per minute in a normal adult. In one cardiac cycle, the heart pumps out 70 mL blood and thus about 4900 mL blood in a minute. Double circulation ensures complete segregation of oxygenated and deoxygenated blood which is necessary for optimum energy production in warm-blooded animals.

Circulation of Blood through the heart:

Systemic Vein ⇨ Sinus Venosus ⇨ Right Auricle ⇨ Right Ventricle ⇨ Pulmonary Artery ⇨ Lungs ⇨ Pulmonary Vein ⇨ Left Auricle ⇨ Left Ventricle ⇨ Trunchus Arteriosus ⇨ Systemic Circulation

The Human Circulatory System

The circulatory system is the system that transports materials around the body to andfrom the cells.Question? Why do humans need a circulatory system whereas bacteria and simpleorganisms do not?Answer: Because the cells of a complex organism such as a human have many

cells that are far from the outside environment where nutrients wouldcome from. The system brings the materials to the cells that would notnormally receive them.Humans have a closed circulatory system: This means that the blood is alwayscontained in tubes and vessels.The human circulatory system is composed of the following:1. Blood Vessels2. Heart3. Blood

BLOOD VESSELS

Humans have three types of blood vessels. They are:a. ArteriesStructure:o Thick, elastico Contain layers of connective, and smooth muscle tissueso DO NOT CONTAIN VALVESFunction: Carry Blood AWAY from the heart.Arteries divide to form very small arteries called arterioles.Biology 2201 Unit 3 – Maintaining Dynamic Equilibrium INotes Human Circulatory SystemPage 2 of 15Page 2b. VeinsStructure:o Thin and slightly elastic.o Contain VALVES for one way flow of blood.Function: return blood TO the heartVeins divide to become venules.Medical Alert: Varicose VeinsThis is a condition where the valves in the veins of a personare not working properly and blood seeps back into the veincausing the vein to become stretched and lose their elasticity.Result: Sagging veins and lack of blood flow to the heart.c. CapillariesStructure:o Microscopic blood vessels that connect arterioles andvenules.o Thin walled and narrowo Blood cells pass through them in single fileFunction: Allows material and gas exchange between the body cells and theblood.

THE HEART

Structure:o A four chambered muscular organ located in the chest cavity of ahuman.o Made of Cardiac muscle.o It is Covered by a Pericardium that protects it.o Pericardium: A tough membrane that surrounds the heart.Function: Pump blood around the body supplying the cells with nutrients andremoving wastes (CO2) from the cells.Semilunar ValveSuperior Vena CavaAortaRight AtriumLeft VentricleSeptumInferior Vena CavaRight VentricleBicuspid ValveLeft AtriumPulmonary ArteryPulmonary VeinTricuspid ValveChordae Tendonae

Functions of Heart Structures1. Inferior/Superior Vena Cava: Returns deoxygenated blood to the right atriumfrom the body.2. Right Atrium: Thin walled chamber of the heart that receivesdeoxygenated blood from the body.3. Tricuspid valve: Controls the flow of blood entering the right ventricle fromthe right atrium.4. Right Ventricle: Muscular chamber that pumps blood TO the lungs.5. Semilunar Valves: Valves that control the flow of blood out of the heart.6. Pulmonary Arteries: Arteries that carry blood TO the lungs.7. Pulmonary Veins: Veins that bring blood to the heart from the lungs.8. Left Atrium: Thin walled chamber that receives oxygenated blood fromthe lungs.9. Left Ventricle: Thick walled chamber that pumps blood out of the heart andto the body.10. Aorta: Large artery that carries blood away from the heart and to allparts of the body.11. Septum: A wall of muscle that separates the left side of the heart fromthe right side. This prevents the mixing of oxygenated anddeoxygenated blood.12. Chordae Tendonae: Control the opening and closing of the Tricuspid andBicuspid (Mitral) valves.13. Bicuspid Valve: A valve that controls the flow of blood from the left atrium tothe left ventricle.

Blood Flow through the HeartDeoxygenated blood from the body enters the right Atrium via the Inferior andSuperior Vena Cava (e). Here the blood is passed through the tricuspid valve to theright ventricle. The right ventricle contracts and forces blood up through the Semilunarvalves and out through the left and right pulmonary arteries. This brings blood to thelungs to be oxygenated.Oxygenated blood from the lungs returns to the heart via the left and right pulmonaryveins to the left atrium. The blood is passed to the left ventricle through the bicuspidvalve. The left ventricle contracts and pushes blood through the Semilunar valves andout through the aorta to the body.

THE HEARTBEAT CYCLEThe human heartbeat occurs in two main stages.These two stages are: a. Diastoleb. SystoleDiastole The stage where the heart is RelaxingDuring this stage the A-V valves (bicuspid, tricuspid) are open and the semilunarvalves close. The ventricles fill with blood.Systole The stage where the heart is ContractingDuring this stage the ventricles contract. This causes the A-V valves to close and thesemilunar valves to open. Blood is forced out through the semilunar valves to the lungsand body.The “LubDub” sound of the HeartbeatThe “LubDub” sound of the heartbeat is caused by the closing of the heart’s valves.Lub Sound -- caused by the closing of the A-V valves (tricuspid, bicuspid).Dub Sound -- caused by the closing of the semilunar valves.Biology 2201 Unit 3 – Maintaining Dynamic Equilibrium INotes Human Circulatory SystemPage 6 of 15Page 6CONTROL OF THE HEARTBEATThe heart is caused to beat regularly by a structure called the Sinoatrial Node (S - Anode) or the PACEMAKER.How it happensAn electrical impulse from the brain is received by the S-A node(pacemaker) in the rightatrium. The SA node sends a signal to the A-V node (atrioventricular node) in theright ventricle. This electrical impulse causes the heart (ventricles) to contract.The pacemaker controls the heartbeat for a human from the time they are born untilthey die or the pacemaker gives out.Q. What happens if the pacemaker gives out?A. The person’s heart will stop beating because the ventricles are not receivingelectrical impulses causing them to contract.A person whose pacemaker gives out can get an artificial one inserted into their chest.

CONTROL OF THE HEART RATE

The heart rate (speed) at which the heart beats is controlled by two nerves.Medulla Oblongata (Sometimes called the Cardioaccelerator nerve):Nerve in the brain that causes the heart to speed up when needed.Vagus nerve: Nerve in the brain that causes the heart to slow down whenneeded.The medulla sends a message to the SA node to cause an impulse to be sent to the AVnode causing the heart to contract more or less in an attempt to set the heart rate.

BLOOD PRESSUREBlood Pressure: A measure of the pressure blood exerts on the walls of bloodvessels.Q. How is blood pressure measured?A. Blood pressure is measured using a blood pressure cuff orSphygmomanometer.It measures the pressure in an artery while the heart is contracting (systolicpressure) and the pressure while the heart is resting (diastolic pressure). Asimple fraction is calculated using the following formula:Blood Pressure = Systolic PressureDiastolic PressureFor example: A person with a pressure 120/80 means that the person has apressure of 120 while the heart is contracting and 80 when the heart is relaxing.P.S. Normal blood pressure is different for each person but is usually around 120/80.Biology 2201 Unit 3 – Maintaining Dynamic Equilibrium INotes Human Circulatory SystemPage 8 of 15Page 8DIVISIONS OF CIRCULATION

There are two types of circulation that happen in the human organism.1. Pulmonary Circulation

2. Systemic circulation1. PULMONARY CIRCULATIONThis is circulation of blood from the heart and to the lungs and vice versa.This type of circulation adds oxygen and removes carbon dioxide from theblood.2. SYSTEMIC CIRCULATIONThis is circulation of blood between the heart and the body.This type of circulation brings blood to the cells and from the cells.Systemic circulation has three subdivisions. They are:A. Coronary CirculationB. Hepatic-portal circulationC. Renal circulationA. Coronary circulation is circulation that supplies blood and nutrients directlyto the heart muscle.B. Hepatic - portal circulation is circulation that carries nutrients and bloodfrom the digestive system to the liver to maintain glucose levels in thebody.C. Renal Circulation is circulation that carries blood to and from the kidneysso that nitrogenous wastes may be removed from the blood andexcreted by the kidneys.

THE LYMPHATIC SYSTEMThis is the part of the circulatory system that returns excess fluids to the blood from thebody.Parts of the Lymphatic System1. Lymph2. Lymph Nodes3. Intercellular Fluid4. Spleen1. LymphThis is the fluid that is found within the lymphatic system. It contains water,proteins and intercellular fluid.2. Lymph NodesThese are small glands at various locations in the body that filter foreign matterfrom the lymph. Foreign matter usually means bacteria, cancer cells and otherdisease causing organisms.The Lymph nodes also contain White Blood Cells that fight off infection._ If you have swollen lymph nodes then this is an indication that you mayhave an infection.3. Intercellular FluidThis is the fluid that is usually squeezed out of a capillary during normal cellactivities. It helps move materials between the cells and the capillaries.It usually contains salt, water, proteins and nutrients.4. SpleenAn organ near the stomach that contains lymph tissue.

Function: Filter out bacteria and worn out RBC’s from the blood.

BLOODBLOOD: Fluid found in the circulatory system of humans that carries nutrients andOxygen to the cells and carries wastes ( carbon dioxide) away from thecells.Helps to control and regulate body temperature as well.COMPONENTS OF BLOODThere are three components to blood:A. PlasmaB. Blood CellsC. PlateletsA. Plasma• The liquid part of blood.• Makes up 55% of the volume of blood.92% water and 7% proteins, 1 % dissolved solutes.Plasma has three proteins in it.i) Albumins — Keeps water from leaving the blood.ii) Fibrinogen — Used for blood clotting.iii) Globulins — Transport proteins around the body. Some are antibodies.Antibody: Proteins that binds to and helps destroy a foreign substancein the body.

B. Blood CellsTwo types:o Red Blood Cells (RBC’s)o White Blood Cells (WBC’s)i) Red Blood Cells --- called Erythrocytes± Human blood contains about 30 trillion RBC’s.± DO NOT contain Nuclei (NONNUCLEATED)± Created by the bone marrow - stem cells.± live about 120 days± double concave shaped± Contain a protein called hemoglobin.± Worn out RBC’s are removed by the liver and spleen.Hemoglobin:A protein found in the blood that is made up of IRON. It carries oxygen to the cells andremoves CO2

Composed of an Alpha and Beta Chain with 2 Heme (Iron) groups on each chain. TheHeme groups bind to and attach Oxygen and CO2

Function of RBC’s: Transport oxygen to cells from the lungs.Transport carbon dioxide from the cells to the lungs.ii) White Blood Cells – called Leukocytes± Larger than RBC’s± have a nucleus± less numerous than RBC’s

± Can move on their ownFUNCTION OF WBC’S: Fight foreign invaders and Infections.Biology 2201 Unit 3 – Maintaining Dynamic Equilibrium INotes Human Circulatory SystemPage 12 of 15Page 12Types of White Blood Cellsa) MacrophagesPhagocytic cells that protect the body by engulfing anddigesting foreign invaders (pathogens).b) LymphocytesNon – phagocytic blood cells that produce antibodies.Two types: T Cells and B CellsC. Platelets± Small pieces of cells found in the blood.± NO Nuclei± Live about 7 days.FUNCTION OF PLATELETS: Blood Clotting Process.

THE BLOOD CLOTTING PROCESSBlood Clotting is actually a complicated chemical process. This is how it works.When a blood vessel is ruptured the following happens:Step 1:Platelets rush to the area. They release an enzyme called Thromboplastin.Step 2:Thromboplastin causes prothrombin (a protein) to be converted in thrombin(enzyme).ThromboplastinProthrombin ---------------------------------------------> ThrombinStep 3:Thrombin causes fibrinogen (found in blood plasma) to be changed into fibrin.ThrombinFibrinogen ---------------------------------------------------> FibrinStep 4:Fibrin forms a net of fibres over the cut and traps red blood cells and plateletsand forms a blood clot.

Circulatory System Disorders1. Hypertension High Blood PressureCauses: diet, stress, inactivityEffects on body: Leads to heart disease and possible failure2. Arteriosclerosis Hardening of the ArteriesCauses: Diet – High in Cholesterol (LDL) and Fats.

Effect on body: Causes arteries to become inelastic which can reduce theamount of blood flow in them. This can lead to a heart attackand/or stroke.3. Atherosclerosis Narrowing of ArteriesCauses: Fatty deposits within the artery walls from poor diet/fat intakeetc.Effect on body: Narrowing of arteries reduces blood flow to heart and brainwhich may lead to heart attack and/or stroke.4. Stroke: Loss of blood flow to brain tissue causing cell death.Causes: Any one of the above and othersEffect on Body: loss of brain function and/or motor control (paralysis), death.5. Coronary Blockage A blockage in the coronary arteries of the heart.Causes: Diet, lack of exerciseEffect on Body: Heart attack, death.Biology 2201 Unit 3 – Maintaining Dynamic Equilibrium INotes Human Circulatory SystemPage 15 of 15Page 15

Treatments for Circulatory System Disorders1. ThrombolyticsThrombolytics are a class of drugs known as “Clot busting” drugs.These drugs help to bust up blood clots that have formed. They help to clearblocked passageways etc.Ex: Streptokinase or t - PA: A Clot busting drug that converts plasminogen toplasmin. Plasmin dissolves the clot.2. AngioplastyProcedure in which a small catheter (tube) with a balloon attached is inserted intoan artery and then inflated. The inflation helps to stretch the artery in an attemptto increase blood flow to the heart.Sometimes a Stent (small mesh netting) is put in place to keep the artery openafter the balloon is removed3. Coronary Bypass SurgerySurgery in which a healthy blood vessel from another area in the body is used tocreate a new pathway around a blockage in a blood vessel near the heart,usually a coronary artery.

What does blood consist of?The blood consists of approximately 78 percent water. The remaining portion ofblood is solid, mostly in the form of protein. Red cells, white cells and plateletsare made in the marrow of bones, especially the vertebrae, ribs, hips, skull andsternum.The main components of human blood are:• Plasma – This is the watery portion of the blood. Blood cells aresuspended here.• Red Blood Cells (Erythrocytes) – Using hemoglobin, these cells carryoxygen from the lungs throughout the entire body.• White Blood Cells (Leukocytes) – These cells aid the immune response.They help fight off infections by engulfing and destroying foreign invaders.• Platelets (Thrombocytes) – Helps the blood clot.

Cardiovascular Diseases:1. Hypertension - High blood pressure. The leading causes for hypertensioninclude stress, diet, heredity, smoking, and aging.2. Coronary Thrombosis - Heart attack. Caused due to a blockage; usually

in the arterial walls.3. Angina Pectoris - A narrowing of arteries due to the buildup of fattydeposits.4. Anemia - Due to low amounts of hemoglobin in blood. Blood cannot carryenough oxygen. Leads the patient feeling constantly tired.5. Leukemia - Makes a large number of abnormal white blood cells.

Circulatory System in human beingsThe circulatory system is also known as the cardiovascular system. The circulatory system comprises blood, blood vessels and the heart.

Blood: Blood is a fluid tissue that flows in special tubes called as blood vessels. Different functions of blood are elucidated. Blood maintains constant body temperature. Blood helps in transportation of food and water from the

digestive system in the body to all the cells in the body. Blood helps in transportation of oxygen from the respiratory

system to the cells present in all parts of the body. Blood helps in transportation of harmful and unwanted wastes

from the cells to the excretory organs. Blood is made up of plasma and formed elements.

Blood provides resistance to the body against pathogens and infections they cause in different parts of the body.

a) Plasma is the fluid part of blood which contains 90% water. It is pale yellow in colour. It carries nutrients, enzymes and waste materials in it.

b) Formed elements are made up of three different types of blood cells. These include red blood cells, white blood cells and platelets. Each of these cells performs a specific function. Red blood cells - RBCs are disc-shaped cells which transport

oxygen to different parts of the body. The presence of haemoglobin gives blood its red colour. Haemoglobin is an iron containing pigment that combines with oxygen to form oxyhaemoglobin. As the blood reaches the cells, oxyhaemoglobin dissociates to release oxygen which is supplied to cells. In the cells, carbon dioxide binds with haemoglobin to form carboxy-haemoglobin. In the lungs, carboxy-haemoglobin dissociates to release carbon dioxide which is expelled out.

White blood cells - These cells are also called as WBCs. These cells are larger than RBCs. White blood cells help in defending the body against infections. White blood cells have the capability of destroying foreign cells. WBCs can move on their own and can enter the areas of infection by passing through the membranes of blood vessels. These are of many kinds - Leucocytes, basophils, neutrophils, eosinophils etc.

Platelets - Platelets are the non nucleated irregularly shaped blood cells which bring about clotting of the blood. These are also called as thrombocytes as they release thromboplastin which brings about clotting of blood. Platelets immediately come to the place of injury and lyse themselves to release thromboplastin. The remnants aggregate in large amounts to form a plug on the injury preventing the blood loss.

Blood vessels: Blood flows through narrow pipe-like structures in the body known as blood vessels. These blood vessels transport food, oxygen and waste throughout the body. Blood vessels are of three types namely, arteries, veins and capillaries.

Arteries are the blood vessels which carry fresh oxygenated blood to all parts of the body. Arteries carry blood away from the heart.  All the arteries

except for pulmonary artery, carry fresh oxygenated blood. Oxygenated blood is pumped by the heart with a great

pressure into arteries, hence they have thick elastic walls.   Arteries transport bright red oxygen rich blood from the heart to

the other parts of the body. Arteries on reaching the tissues divide into fine vessels or

tubes known as capillaries Pulmonary artery carries impure blood to the lungs from heart.

Veins are the blood vessels which carry deoxygenated blood from all parts of the body to tissues to the heart. Veins carry blood to the heart. They carry carbon dioxide rich

blood to the heart from different parts of the body.  Veins have valves on their inner lining that allow blood to flow

only in one direction. In the tissues, number of capillaries join together to form a

vein. Pulmonary veins carry pure blood from lungs to the heart.

Blood capillaries are the thinnest blood vesels which are in direct contact with the cells. Capillaries nourish the cells of the tissue with

oxygenated blood. They have thin membranes through which oxygen and

nutrients get into the cells.

Veins inturn receive carbon dioxide and waste products from the cells.

Later, all these capillaries of that tissue at another end combine to form a vein.

This vein carries deoxygenated blood to the heart. Deoxygenated blood is sent to lungs for purification.

Heart: The heart is the central organ for pumping the blood throughout the body. Heart is made up of strong cardiac muscles. It is located in the chest cavity with its lower part pointing

towards the left. Its size is that of the person’s fist.  It pumps blood rich in carbon dioxide to the lungs and oxygen-

rich blood to other parts of the body. The heart consists of four chambers namely auricles and

ventricles. The two upper chambers of the heart are known as the auricles.The two lower chambers of the heart are the ventricles.

Left and right parts of the heart are separated by a muscular partition called as septum.

Heart has number of valves which allow the blood to flow in one direction. These valves prevent the oxygenated blood mixing with de-oxygenated blood.

Purification of blood is a stepwise procedure happening in a sequence. Double circulation is observed in human beings. Blood passes twice through the heart. Step 1 - Pure oxygenated blood from the lungs is carried to the

left auricle through pulmonary veins. Left auricle contracts to push the pure blood into left ventricle. 

Step 2 – Blood from left ventricle is carried to all parts of the body through arteries. Blood gets purified in the lungs.

Step 3 – Deoxygenated blood from the tissues is collected by veins and transported to right auricle. Right auricle contracts to send this impure blood into right ventricle.

Step 4 - Right ventricle pumps deoxygenated blood into the lungs through pulmonary arteries.

Heart beat is the combined effect of contractions and relaxations of the cardiac muscles occurring in two batches. Two auricles contract first to force the blood into two ventricles

on either side. This produces a 'lub' sound. Later, two ventricles contract to send the blood into arteries

moving towards the body and pulmonary artery moving towards the lungs producing a 'dub' sound.

The rhythmic contraction and relaxation of the heart constitutes heartbeat.

Heartbeat can be felt by placing the palm on the left side of the chest.

Stethoscope is a device that amplifies the sound of your heartbeat.

Pulse is the throbbing sensation in the wrist region signifying the blood rushing through the arteries. It is the pressure applied by blood on the walls of an artery at a

particular part of the body. The number of times the heart beats in a minute is the same

as the pulse rate. The ideal pulse rate is 70 to 80 per minute.

Measurement techniques

Electrocardiogram —for cardiac electrophysiology Sphygmomanometer and stethoscope—for blood pressure

Pulse meter —for cardiac function (heart rate, rhythm, dropped beats)

Pulse —commonly used to determine the heart rate in absence of certain cardiac pathologies

Heart rate variability —used to measure variations of time intervals between heart beats

HemostasisHemostasis, or the clotting of blood and formation of scabs, is managed by the platelets of the blood. Platelets normally remain inactive in the blood until they reach damaged tissue or leak out of the blood vessels through a wound. Once active, platelets change into a spiny ball shape and become very sticky in order to latch on to damaged tissues. Platelets next release chemical clotting factors and begin to produce the protein fibrin to act as structure for the blood clot. Platelets also begin sticking together to form a platelet plug. The platelet plug will serve as a temporary seal to keep blood in the vessel and foreign material out of the vessel until the cells of the blood vessel can repair the damage to the vessel wall.