The circulatory system by T@NV!R

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Biology--- The circulatory system T@NV!R

The circulatory system ---The circulatory system of mammals consists of the heart, which pumps blood into vessels called arteries, which divide inside body tissues and organs into extremely fine vessels called capillaries, which in turn empty into veins that carry blood back to the heart.

Blood

Blood – blood is a viscous fluid which flows through closed circuits called blood vessels.Or, blood is a fluid tissue. It consists of blood cells which are suspended in liquid called plasma.Or, blood is a fluid tissue that acts as a transport medium within an animal.

Plasma – plasma is a pale yellowish liquid. It is the liquid part of blood [i.e. excluding the blood cells].it consists of water containing a large number of dissolved substances.

Composition of plasma--- plasma is composed mainly of water with dissolved substances like:

Digested foods – glucose, amino acids etc.Plasma proteins – albumin, globulin, fibrinogen, prothrombin.Enzyme – thrombokinase etcIons – sodium ions, chloride ions etcHormones – growth hormone, adrenaline etcAntibodies – opsonin, lysin etc.

Blood cellsRed blood cells/ erythrocytes:

Q: Where formed?

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Red blood cells are formed or made in the red bone marrow of short bones such as the sternum, ribs and vertebrae. Average life span: their average life-span is four months or 120 days. Average number: their approximate size is 7micro meters in diameter. Structure: they have no nucleus but the cytoplasm contains the red iron containing protein called hemoglobin.Function: its main function is to carry oxygen in the form of oxyheamoglobin from the lungs to all parts of the body.

Adaptations of RBC---They contain haemoglobin which picks up oxygen from lungs.They have no nucleus leaving more space for haemoglobinRed blood cells are small and flexible so they can squeeze through narrow capillaries.The biconcave disc shape gives them a large surface area, so they can absorb more oxygen. Q: What makes it possible for RBC to pass through the capillaries which are smaller than itself in diameter?---- Because they are flexible [have spongy cytoplasm], so they can squeeze/pass through the capillaries.Q: Where RBCs are destroyed?---They are destroyed in the liver and the spleen. The red haemoglobin changes to a yellow pigment, bilirubin, which is excreted in the bile. The iron from the haemoglobin is stored in the liver.

Figure 1: red blood cellQ: Why does man have more RBC than woman?

Woman experiences menstruation.Men need more oxygen to make more energyMan have more energy e.g. muscle cells hence are able to perform heavy activitiesMen are taller than women.Q: Why does RBC have a life span of 120 days?They lack nucleusHence there is no control over the cell.Repairing of damages on the surfaces of RBC is not possibleHence they wear off quickly i.e. within 120 daysHence they are unable to carry oxygen efficientlyThis is why they are destroyed at the end of 120 days and are replaced with new RBC to ensure efficient oxygen carrying ability by blood.

Why does man have more RBC than woman?

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Women experiences menstruation [a periodic monthly blood loss]Men need more oxygen to make energy.Men have more cells e.g. like muscle cells and fats, hence are able to perform heavy activities.Men are taller than women.

Q: How the structure of RBC suited to its function? Diameter of RBC is 7 micrometer which is equal to the diameter of the lumen of a capillary.Flexible membrane and spongy cytoplasm helps them to squeeze through the one cell thick capillary.This makes the cell membrane come in contact with the walls of the capillary making diffusion of oxygen easier.The shape being bi-concave increases the surface area of the RBCThe middle of the RBC is thin which also ensures the better diffusion Has a red pigment called haemoglobinHaemoglobin tends to grow affinity oxygen when the surrounding tissues are high in oxygen concentration and the reverse. This makes RBC efficient in carrying oxygen.

Phagocytes lymphocytesLymphocytes --- produced in the lymph node of the lymphatic system Produce antibodies which act as antitoxins which neutralize the poisonous effect of the toxins produced by germs/microbes.The antibodies can also kill the bacteria/germs/microbes in the blood.Some lymphocytes persist in our blood after infection and give us immunity to specific diseases.Phagocytes --- are produced by white bone marrow of long bonesEngulf bacteria and other micro-organisms that have infected our body. Structure of lymphocytes ---Regular cell membraneClear/non-granular cytoplasmLarge spherical cytoplasmStructure of phagocytes ---Irregular cell membrane [amoeba like]Granular cytoplasmLobed nucleusPhagocytosis --- the process of engulfing and ingesting foreign particles like bacteria by the white blood cells [phagocytes] is known as Phagocytosis.Antigen— bacteria viruses or foreign substances which stimulates the production of antibodies.

White blood cells

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Immunity --- the ability of an organism to resist infection from parasites.Serum—serum is blood plasma from which fibrinogen has been removed.Platelets--- are fragments of RBC Takes part in blood clotting

Importance of clotting Prevent excess blood lossPrevent pathogens / foreign substances from entering

Platelets are cell fragments bounded off from special, very large cells in the red bone marrow and they play an important part in the clotting action of blood.Mechanism of clotting

Functions of platelets --- helps in clotting to prevent excessive loss of blood and entry of pathogens.Mechanism of clotting [description]—

One the blood vessels are damaged, the platelets burst and releases an enzyme thrombokinase.

Thrombokinase causes the conversion of plasma protein inactive prothrombin into active thrombin.

Active thrombin converts fibrinogen into fibrin in the presence of calcium ionFibrin is the clot and the size of the clot increases as blood cells [RBC] sticks to the

Damaged tissue + platelets

Thromboplastin/ thrombokinase

Prothrombin [inactive]

Thrombin [active]Soluble fibrinogenInsoluble fibrin threads +RBC

Blood clot

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The heart ----Definition--- heart is a muscular pumping organ

Heart is made up [of cardiac muscles.The heart is divided into right & left half by a middle portion called septum.The septum prevents the mixing of oxygenated & deoxygenated blood.

Heart consist of 4 chambers: 2 atrium & 2 ventriclesChambers of heart---Heart consists of 34 chambers. They are:

Right atrium—receive deoxygenated blood from the vena cavaLeft atrium--- receives oxygenated blood from the lungs via/ through pulmonary veins.Right ventricles--- pumps oxygenated blood to lungs via pulmonary artery Left ventricle--- pumps oxygenated blood to all parts of the body through aorta [biggest artery]

Q: What are atria & ventricles? Atria [plural] – upper 2 chambers of the heart ate known as atrium [singular] They are thin walled.Receives blood from the veins Ventricles ---lower 2 chambers of the heart are known as ventricles They have thick muscular walls. The left ventricles has the thickest muscular walls to pump blood to all parts of the body [to withstand the pressure while pumping blood to all parts of the body] Pump blood into the arteries.Heart is connected to four blood vessels: 2 arteries-- 1.aorta 2.pulmonary artery & 2 veins—1.vena cava 2.pulmonary vein

Types of blood vessels ---Vena cava --- large vein returning from the body to the right atrium of the heart

Left atrium

Left ventricle

Right atrium

Right ventricle ventricleventricl

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Vena cava is divided into 2:1. Superior vena cava—empties at the top of right atrium. Carries deoxygenated blood from

the head and upper limbs to the right atrium.2. Inferior vena cava--- empties at the base of the right atrium. Carries deoxygenated blood

from the lower limbs and organs to the right atrium. Veins – blood vessels which convey blood towards the heart are known as veins.Arteries --- blood vessels which carry blood away from the heart are known as arteriesPulmonary artery--- arises from the top of the right ventricle. Carry deoxygenated blood to the lungs Pulmonary vein--- it empties into the left atrium. Carry oxygenated blood from the lungs to the left atrium.Aorta [biggest artery--- largest artery of the body arising from left ventricle.Or, Main artery from the heart to the body.Carries oxygenated blood to all parts of the body.Coronary artery--- these are blood vessels that are found over the surface of the heart.Their function is to supply oxygen and nutrition to the outer two third of the heart. Coronary artery can block if a person has high level of fat in diet and that can lead to heart disease.

Oxygenated blood Deoxygenated bloodAorta & pulmonary vein Vena cava & pulmonary artery

The heart has valves.Valves are of 3 types: tricuspid valve, bicuspid valve & semi lunar valveFunctions of valve---They act as one way door/gate, i.e. it allows blood to flow in one direction.It prevents backflow of blood. There are 3 types of valves—

Tricuspid valveBicuspid valveSemi lunar valve

Q: Why are the walls of the left ventricle thicker than the right?Left ventricle need to pump blood through the aorta to all parts of the body [i.e. a greater distance] except the lungs.

Hence forth require a higher pressureRight ventricle pumps blood only to the lungs [i.e. a shorter distance] this means that pulmonary circulation requires higher pressure

So the walls of the left ventricles are much thicker than right ventricles to withstand the high pressure created while pumping blood through the aorta.

The heart experiences / performs 2 circulation at a timePulmonary circulation

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Systematic circulationPulmonary circulation --- the system of blood vessels that conveys blood form the right ventricle to the lungs and back to the left atrium of the heart.Systematic circulation --- the series of blood vessels which carries blood from the left ventricle around the body and back to the heart at the right atrium.

Blood is supplied to the cardiac muscles by coronary artery.Cardiac cycle --- [0.8 seconds]Atrial systole Ventricular systoleAtria contracts Ventricles contractThe bicuspid & tricuspid valves open The bicuspid & tricuspid valves closeVentricles relax Atria relaxSemi lunar valves closes Semi lunar valves openThis makes blood to move from the atria to the ventricles

Blood is pumped out of the heart through the pulmonary artery & aorta

Cardiac output --- quantity of blood pumped out of the left ventricle within a minute.During exercise, the oxygen demand to the respiring tissue increase. The rate & depth of breathing increase. The extra oxygen taken in is supplied to the respiring tissue by an increase in the beat rate.

Heart rate is controlled by: Nervous response

Arteries have the following features:– Rich in elastic fibres so can stretch.– Tough and thick walls to withstand pressure.– Arterioles are very muscular, so can constrict or dilate to control blood flow.

Veins have the following features:– Relatively thin walls, as blood is at a low pressure.– Contains valves to prevent the backflow of blood.

Blood is kept moving through the veins due to:– The small residual pressure of blood from the capillaries.– The reduced pressure in the atria during diastole.– Leg muscles act as a secondary heart to contract and force blood upwards.

Capillaries consist of a single layer of endothelial cells. They are therefore thin and permeable toallow rapid diffusion and exchange.

monal response --- adrenaline produced by the adrenal glands controls heart rate.

Water is exchanged between the blood and the tissue fluid due to two forces:

1 contraction [systole]

1 relaxation [diastole]

1 cardiac cycle

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– Hydrostatic pressure – pressure due to the heart tends to push water out of the capillaries.

This occurs at the arterial end of the capillaries– Water potential – low water potential in capillaries due to plasma proteins draws water

into the vessels. This occurs at the venous end of the capillaries.Small lymph vessels are located near to the capillaries and body cells. The lymphatic system is thedrainage system of the body, and keeps tissue fluid consistent. There are lymph nodes at variousplaces in the body, and these filter the lymph, and also produce lymphocytes. Lymph re-enters theblood just beneath the right subclavian vein.

The medulla oblongata is located in the hindbrain, and is responsible for controlling the heart rateand the breathing rate.

At the start of a period of exercise, anaerobic respiration takes place, whilst he level oxygen buildsup for aerobic respiration to take place. This lack of oxygen to begin with is the oxygen deficit,and must be taken up at the end of the exercise period to oxidise all the lactate that was produced.This is the oxygen debt.For short periods of exercise, the person doesn’t have long to breathe, and so most of the respiration will be anaerobic. For longer periods of exercise, more of the respiration taking place

will be aerobic.

The circulatory system by T@NV!R

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