CLASS 11 TH Body fluids and circulation

DETAILED CHAPTER OF BODY FLUIDS AND CIRCULATION.
WELL EXPLAINED WITH DIAGRAM. WELL ORGANISED POWER[POINT TEMPLATES. SHORT AND PRECISE NOTES. WELL DEFINED TOPICS FOR EACH SUBJECTS.

1. BODY FLUIDS AND CIRCULATION SUBMITTED BY : D.C.DHARUN MUGHILAN SUBMITTED TO : MRS. BHANUMATHI (PGT BIOLOGY)

2. CIRCULATORY SYSTEM This system is concerned with the circulation of body fluids to distribute various substances to various body parts.  The circulatory system is also known as the cardiovascular system. It is an organ system that allows blood to circulate and transport nutrients (such as electrolytes and amino acids), oxygen, carbon dioxide, hormones, and blood cells. These are circulated to and from cells in the body to nourish it.  The components of the human circulatory system include the heart, blood, red and white blood cells, platelets, and the lymphatic system.

3. CIRCULATORY SYSTEM

4. Functions of Circulatory System It transports nutrients from their sites of absorption to different tissues and organs for storage, oxidation or synthesis of tissue components. It also carries waste products of metabolism from different tissues to the organs meant for their excretion from the body. It transports respiratory gases between the respiratory organs and the tissues. It carries metabolic intermediates from one tissue to another for their further metabolism; for example, blood carries lactic acid from muscles to the liver for its oxidation. It also transports informational molecules such as hormones, from their sites of origin to the tissue It uniformly distributes water, H+, chemical substances to all over the body.

5. Types of Blood Circulation in Human The physiology of blood circulation was first described by Sir William Harvey in 1628. The blood circulation in our body is divisible into 3 circuits – (i) Coronary circulation:  It involves blood supply to the heart wall and also drainage of the heart wall. (a) Coronary arteries:  One pair, arising from the aortic arch just above the semilunar valves. They break up into capillaries to supply oxygenated blood to the heart wall. (b) Coronary veins:  Numerous, collecting deoxygenated blood from the heart wall and drains it into right auricle through coronary sinus which is formed by joining of most of the coronary veins. (ii) Pulmonary circulation:  It includes circulation between heart and lungs. The right ventricle pumps deoxygenated blood into a single, thick vessel called pulmonary aorta which ascends upward and outside heart gets divided into longer, right and shorter, left pulmonary arteries running to the respective lungs where oxygenation of blood takes place. (iii)   Systemic circulation:  In this, circulation of blood occurs between heart and body organs. The left ventricle pumps the oxygenated blood into systemic arch which supplies it to the body organs other than lungs through a number of arteries.

6. BLOOD Blood is a connective tissue which is composed of a fluid matrix (plasma) and formed elements.

7. Plasma Plasma is a  straw-coloured  and viscous fluid. Plasma constitutes about 55% of the blood. About 90% of plasma is water and about 6-8% is composed of proteins. The major plasma proteins are; fibrinogen, globulins and albumins. Fibrinogen  play important role in blood coagulation. Globulins  are mainly involved in defense mechanism and  albumins  help in osmotic balance. Small amounts of minerals; like Na+, Ca+ +, Mg+ +, HCO3– and Cl–; are also present in plasma. Plasma also contains glucose, amino acids, lipids, etc.  Factors for clotting of blood are present in the plasma in an inactive form. Plasma without the clotting factors is called  serum .

8. Formed Elements The formed elements constitute about 45% of the blood.  Erythrocytes, leucocytes  and  platelets  are collectively called formed elements.

9. Erythrocytes or Red Blood Cells (RBCs) The RBCs are the most abundant cells in blood. In a healthy adult, about 5 million to 5.5 million RBCs are present per cubic mm of blood. RBCs are formed in the read bone marrow.  In most of the mammals, nucleus is absent in the RBCs. RBCs are biconcave in shape. The red colour is because of an iron containing protein complex; called haemoglobin. In a healthy adult, each 100ml of blood contains 12-16 gm Hb. The average lifespan of RBCs is 120 days. RBCs are finally destroyed in the spleen and hence, spleen isthe graveyard of RBCs.  RBCs play a significant role in transport of respiratory gases.

10. Leucocytes or White Blood Cells (WBCs): The WBCs are nucleated and are relatively lesser in number than RBCs. In a healthy adult about 6000-8000 WBCs are present per cubic mm of blood. Leucocytes are generally short lived. There are two main categories of WBCs: Granulocytes  , e.g., neutrophils, eosinophils and basophils Agranulocytes . e.g., Lymphocytes and monocytes. Neutrophils : Neutrophils are the most abundant cells among WBCs and comprise about 60-65%. Monocytes : Monocytes comprise about 6-8% of WBCs. Neutrophils and monocytes are phagocytic cells. Basophils : Basophils secrete histamine, serotonin, heparin, etc. They are involved in inflammatory reactions. Eosinophils : Eosinophils comprise 2-3% of WBCs. These resist infections and are also associated with allergic reactions. Lymphocytes : Lymphocytes comprise about 20-25% of WBCs. There are two major types of lymphocytes, viz. B and T types. Both the types are responsible for immune responses of the body.

11. Platelets Platelets are also known as thrombocytes. They are cell fragments produced from megakaryocytes. Megakaryocytes are special cells in the bone marrow. Usually, one cubic mm of blood contains 150,000-350,000 platelets. Platelets can release a variety of substances. Most of these substances are involved in blood coagulation.

12. BLOOD GROUPS Two such groupings – the  ABO  and  Rh  – are widely used all over the world. Importance of Blood Group:  During blood transfusion, the donor blood needs to be carefully matched with the blood of a recipient. Transfusion of unmatched blood can lead to severe problems of clumping, i.e. destruction of RBC. The blood group O can be donated to persons with any other blood group and hence, an individual with O group is called  universal donor.  A person with AB blood group can accept blood from all blood groups and hence, such an individual is called  universal recipient.

13. ABO Grouping ABO grouping is based on the presence or absence of two surface antigens on the RBCs, viz. A and B. Antigens are chemicals which can induce immune response. The plasma also contains two natural antibodies. Antibodies are proteins produced in response to antigens.

14. Rh Grouping The Rh antigen is similar to one present in  Rhesus monkeys.  It is also observed on the surface of RBCs of majority (nearly 80%) humans. Such individuals are called Rh positive (Rh +ve). A person without Rh antigen is called Rh negative (Rh –ve). Significance of Rh Group:  An Rh -ve person, if exposed to Rh +ve blood, will form specific antibodies against the Rh antigens. Hence, Rh group should also be matched before transfusions.

15. Coagulation of Blood Blood coagulates in response to an injury or trauma. Coagulation is a mechanism to prevent excessive loss of blood in case of injury. Clot is a dark reddish brown scum which is formed at the site of an injury over a period of time. This is formed by a network of threads called fibrins in which dead and damaged formed elements of blood are trapped.

16. Process of Blood Clotting    Inactive fibrinogen is present in the plasma. It is converted by the enzyme thrombin into active fibrin. Thrombin is formed from the inactive prothrombin. An enzyme complex, thrombokinase, is responsible for this conversion. This complex is formed by a series of linked enzymatic reactions . The process involves a number of factors present in the plasma in an inactive state. An injury stimulates the platelets to release certain factors which activate the mechanism of coagulation.   

17. BLOOD VASCULAR SYSTEM Higher animals have a well-developed circulatory system so that transport of substances in the body can be done very effectively.  In them, the circulatory system consists of a central pumping organ called as heart and various blood vessels (arteries, veins and capillaries).  Arteries conduct the blood from the heart to other tissues; veins bring blood from other tissues to the heart.  Some of the invertebrates and all vertebrates possess this system.  The circulatory system was first discovered and demonstrated by  William Harvey.   The blood vascular system may be of two types, the open and the closed circulatory systems. 

18. The Open and the Closed circulatory systems.  Open circulatory system  :  In many advanced invertebrates such as prawns, insects and molluscs, the blood does not remain confined to blood vessels but it flows freely through the body cavity and channels called lacunae and sinuses in the tissues.  The body cavity is known as hemocoele and the blood is hemolymph.  In insects, the tissues are in direct contact with the blood.  Hemolymph circulates in the whole body due to the contractile activity of heart. 

19. Closed circulatory system  : In closed circulatory system the blood flows through proper blood vessels named arteries, veins and blood capillaries.  Arteries within the tissues divide into arterioles, which then branch further to form capillaries.  Capillaries then unite to form venules, which come out of the tissues and veins.  Arteries have thick, elastic and muscular walls which are made up of three concentric layers viz., tunica externa, tunica media and tunica interna.  All these layers have got smooth or involuntary muscles. Capillaries are extremely fine, thin blood vessels the walls of which are made of a single layer of endothelial cells.  The muscles and elastic fibers are absent in them.  These capillaries are highly permeable to water and small macromolecules.  Various nutrients, respiratory gases, metabolites and other substances are exchanged between the blood and tissues through these capillaries.

20. DIFFERENCES BETWEEN OPEN AND CLOSED CIRCULARY SYSTEMS Open circulatory system In open circulatory system blood flows through large open spaces and channels called lacunae and sinuses among the tissues. Tissues are in direct contact with the blood.  Blood flow is very slow and blood has very low pressure. Exchange of gases and nutrients takes place directly between blood and tissues Closed circulatory system In closed circulatory system blood flows through a closed system of chambers called heart and blood vessels.  Blood does not come in direct contact with tissue.   Blood flow is quite rapid and blood has a high pressure Nutrients and gases pass through the capillary wall to the tissue fluid from where they are passed on to the tissues.

21. Open circulatory system (5) Less efficient as volume of blood flowing through a tissue cannot be controlled as blood flows out in open space. (6) Open circulatory system is found in higher invertebrates like most arthropods such as prawn, insects, etc., and in some molluscs (7) Respiratory pigment, if present, is dissolved in plasma; RBCs are not present. Closed circulatory system (5) More efficient as volume of blood can be regulated by the contraction and relaxation of the smooth muscles of the blood vessels. (6) closed circulatory system is found in echinoderms, some molluscs, annelids and all vertebrates. (7) Respiratory pigment is present and may be dissolved in plasma but is usually held in RBCs.

22. ARTERIES AND VEINS Structurally veins resemble arteries except that the three layers are very thin and more elastic.  In the veins the muscles and elastic connective tissues are poorly developed.  But the collagen fibers of the outer layer are very well developed.  In most of the veins the middle coat is extremely thin with practically no muscles.  In many veins semilunar valves are present in their lumen.  These valves allow the flow of the blood only in one direction i.e., towards the heart.

23. THE HEART The heart is the central pumping organ of the blood vascular system.  It is a hollow muscular structure and is made up of cardiac muscles.  It works throughout life rhythmically without getting tired.  It is enclosed in a double membraneous sac called pericardium that is filled with pericardial fluid.  Mainly there are two chambers in a heart – auricle or atrium that receives the deoxygenated blood from various parts of the body; and a ventricle that distributes the oxygenated blood to the body.  The number of these chambers varies in different animals. 

24. PISCES Branchial heart,Thick, muscular, made of cardiac muscles, has two chambers (i) auricle and (ii) ventricle. The heart is called venous heart since it pumps deoxygenated blood to gills for oxygenation. This blood goes directly from gills to visceral organs (single circuit circulation). A sinus venosus and conus arteriosus is present. Lung fishes have 2 auricles and 1 ventricle.  For example : Labeo, Scoliodon, Neoceratodus,etc.

25. AMPHIBIANS Heart consists of (a) Two auricles (b) Undivided ventricle (c) Sinus venosus (d) Truncus arteriosus (conus + proximal part of aorta) Right auricle receives blood from all the visceral organs (deoxygenated) via precaval and post caval. Pulmonary artery carries deoxygenated blood to lungs for oxygenation. This blood returns to left auricle via pulmonary vein (Double circuit circulation) FOR EXAMPLE :Frog,Toad,etc.

26. REPTILES Heart consists of : (a) Left and right auricle (b) Incompletely divided ventricle (Ventricle in crocodiles gavialis and alligator is completely divided) (c) Sinus venosus (d) Conus arteriosus divided into right systemic, left systemic and pulmonary arch. FOR EXAMPLE: Lizards ,Snakes , Turtles,etc.

27. AVES Heart consists of (a) Left and right auricle (b) Left and right ventricle (c) Complete separation of arterial and venous circulation (d) Only right systemic arch is present (e) Sinus venosus and truncus arterisious absent FOR EXAMPLE:Pigeon,etc.  

28. MAMMAL S Heart consists of (a) Left and right auricle (b) Left and right ventricle (c) Complete separation of arterial and venous circulation (d)They have left systemic arch.    (e) Sinus venosus and truncus arterisious absent FOR EXAMPLE: Human,Rabbit,etc.  

29. HUMAN HEART

30. The mammalian heart including man is a hollow, cone-shaped, muscular structure that lies in the thoracic cavity above the diaphragm and in between the two lungs.  It is about the size of a fist measuring about 12 cm in length and 9 cm in breadth.  It weighs about 300 grams.  It is a four chambered organ-two atria or auricles and two ventricles.  Deoxygenated blood is received into right auricle by superior vena cava (from anterior region) and inferior vena cava (from posterior region) of the body.  These vena cavae open directly into right auricle as there is no sinus venosus.   Right auricle also gets blood from coronary veins (from the heart muscles itself).  The right and left auricles are separated by interauricular septum.  Similarly, right and left ventricles are also separated by interventricular septum.  Deoxygenated blood is then passed from the right auricle to the right ventricle through the atrioventricular aperture guarded by tricuspid valve (having three flaps).

31. The blood is then pumped into lungs for oxygenation via pulmonary artery.  After oxygenation, the blood is brought back into left auricle via four pulmonary veins.  From left auricle, blood (now oxygenated) goes to left ventricle through atrio-ventricular aperture and this opening is regulated by bicuspid (having two flaps) or mitral valve.  The left ventricle has also got chordae tendinae and papillary muscles which prevent the valves (both bicuspid and tricuspid) from being pushed into auricles at the time of ventricular contraction.  Thus the walls of left ventricle are thicker than the walls of right ventricle. The oxygenated blood from left ventricle is then distributed to all parts of the body with the help of aorta.  The openings of the aorta and other major arteries are guarded by semilunar valves that prevent the back flow of blood.  

32. Differences between first and seconds heart sounds First heart sound (Lubb) Second heart sound (Dup) (1) It is produced by closure of bicuspid and tricuspid valves at the start of ventricular systole. (1) It is produced by closure of semilunar valves at the start of ventricular diastole. (2) It is low pitched, less loud and of long duration. (2) It is higher pitched, louder, sharper and of short duration. (3) It lasts for 0.15 seconds. (3) It lasts for 0.1 second. (4) Its principal frequencies are 25 to 45 cycles per second. (4) Its principal frequency is 50 cycles per second.

33. CIRCULATION OF BLOOD THROUGH HEART (1) The heart pumps blood to all parts of the body. (2) The deoxygenated blood is drained into right auricle through superior and inferior vena cava and coronary sinus whereas the pulmonary veins carry oxygenated blood from lungs to the left auricle. This is called as Auricular circulation. (3) About 70% of the auricular blood passes into the ventricles during diastole. This phase is called diastasis. (4) The rest of 30% of blood passes into the ventricles due to auricular systole (contraction). (5) In this way, blood reaches the ventricles and is called ventricular filling. (6) During ventricular systole (which starts first in left ventricle than in right ventricle), the pressure increases in the ventricles, thus, forcing the oxygenated blood from left ventricle into systemic aorta and deoxygenated blood from right ventricle into pulmonary aorta. (7) The systemic arch distributes the oxygenated blood to all the body parts except lungs while pulmonary aorta carries the deoxygenated blood to lungs for oxygenation.

34. HEART RATE AND PULSE In the resting condition, human heart beats at the rate of about 70 times per minute. But, the heart beat rate increases during exercise, fever, and emotions like anger and fear. During each heart beat, the blood is pumped from the ventricles of the heart into the aorta to be distributed to all parts of the body.  This happens during the ventricular systole and is repeated every 0.8 seconds.  The blood from aorta then goes to other arteries of the parts.  This causes a rhythmic contraction in the aorta and its main arteries.  It  can be felt as regular jerks or pulse  in the regions where arteries are present superficially like wrist , neck and temples.  This is known as arterial pulse.   The pulse rate is, therefore, same as that of heart beat rate.  This heart beat rate differs from species to species.  In general, the smaller the animal, the greater the heart beat.  Hence, larger animals have lower heart rates.  For example, an elephant has a normal heart beat rate of about 25 times per minute, where as mouse has a normal heart beat rate of several hundreds per minutes.  

35. Automatic rhythmicity of the heart: The mammalian heart is a myogenic heart i.e., the heart beat originate from a muscle (but it is regulated by nerves).  In the right atrium near the region where superior vena cava opens, a specialised muscle called sinu-auricular node (SA-node) is present from where the heart beat originates.  It is also called as pace maker and is richly supplied with blood capillaries.  A wave of contraction (systole) originates from it and spreads over to the whole heart. At the junction of right atrium and right ventricle, a tissue called auriculo-ventricular node (AV-node) is present that picks up the wave of contraction propagated by SA-node.  This is also known as bundle of His.  Branches of this spread over the ventricle forming the Purkinje system.  The wave of contraction spreads over the ventricle through AV-node and its Purkinje system.   The heart is supplied with vagus (parasympathetic) and sympathetic nerve fibers. The vagus nerve is inhibitory and so when stimulated slows down the heart beat; while the sympathetic nerve is acceleratory and so when stimulated fastens the heart beat.  This happens because these nerves release chemicals (hormones) when stimulated. 

36. Fractions of cardiac output : Amount of pure blood going to an organ per minute is called as fraction of the organ. (i) Cardiac fraction – 200 ml/min. (ii) Hepatic fraction – 1500 ml/min. (28% of blood as liver is the busiest organ of body and has maximum power of regeneration). (iii) Renal fraction – 1300 ml/min (25% of blood) (iv) Myofraction – 600-900 ml/min. (v) Cephalic organs – 700-800 ml/min.

37. Arterial Blood Pressure:             The pumping action of the heart maintains a pressure of blood in the arteries.  This is called Arterial blood pressure.  It helps to pump blood at a high velocity along the arteries in the closed circulatory system.  The blood pressure is far lower in the open circulatory system.  

38. Blood Flow in Veins:      The blood pressure is low in veins, because the blood flows through narrow arterioles and capillaries to enter wider veins.  At many places in the body, this blood pressure is not sufficient to drive the blood through the veins back to the heart.  Veins have thinner walls than arteries and are more easily compressed.  There are also many valves inside the veins. These valves permit the flow of blood in the veins towards the heart and prevent blood flow in the reverse direction.  Contraction of muscles and changes of body posture compresses the veins to move the blood inside them.  During this both cases, blood moves towards the heart only, because the venous valves prevent the blood flow in the opposite direction.  This is a major process for venous blood flow.  

39. Electrocardiogram (ECG) (i) Depolarisation waves:  They represent the generation of the potential difference. These waves appear only when both electrodes of galvanometer are in different fields. When both the electrodes are in same field, there are no deflection and wave drops down to base line. (ii)   Repolarisation waves:  They appear when depolarisation is over and the muscle fibre is returning to its original polarity. When both electrodes are in same polarity (means 100% repolarisation and 100% depolarisation), there is no deflection. (a)  P  wave:  Indicates impulse of contraction generated by S.A. node and its spread in atria causing atrial depolarisation. The interval  PQ  represents atrial contraction and takes 0.1 second. b) QRS complex:  Indicates spread of impulse of contraction from A.V node to the wall of ventricles through bundle of His and pukinje fibres causing ventricular depolarisation. This complex also represents repolarization of S.A. node. The RS of  QRS  wave and  ST  interval show ventricular contraction (0.3 seconds). QRS is related to ventricular systole. (c) T  wave:  Indicates repolarisation during ventricular relaxation.

40. Lymph and Tissue Fluid It occurs in the spaces in between the cells of a tissue and is called as interstitial fluid or tissue fluid.  The exchange of any material (solid, liquid or a gas) that occurs between the blood and the tissue cells always takes place through this fluid.  Under the pressure of blood in the capillaries some of the water and desired solutes are filtered out from the blood plasma into the tissue spaces to form the tissue fluid.   The composition of this tissue fluid is very similar to that of plasma except that it has much less protein.  Proteins are less because some of the proteins are not filtered out from the capillary walls (impermeable). Some of the tissue fluid enters tiny channels called lymph vessels and the fluid collected in them is called lymph and this system is known as lymphatic system.  These lymph vessels unite to form larger lymph vessels which ultimately drain into two large lymph vessels called thoracic duct and the right lymphatic duct.  These open into veins returning the lymph finally into venous blood and so in the general circulatory system.  This movement of lymph is mainly due to the squeezing action of the surrounding muscles.  So the lymphatic system is slow and uncertain. Exercise increases the rate of lymph circulation.   Generally, the rate of lymph formation is equal to the rate of its return to the blood stream.  But sometimes, the formation rate of lymph exceeds the rate of its return to blood.  The increased volume of fluid around the cells then creates a swelling, called dropsy or oedema. 

41. Functions of Lymph 1.      It serves to return interstitial fluid into blood. 2.      The plasma proteins macromolecules synthesized by the liver cells, cannot pass into the blood vessels, but can diffuse into the lymph vessels through their wall and they come to the blood through lymph.   3.      It also carries absorbed fats and lipids from the small intestine to the blood in the form of chylomicron droplet

42. Lymphatic System The lymphatic system is an extension of the circulatory system. It consists of a fluid known as lymph, lymph capillaries and lymph ducts. (a)  Lymph:  It can be defined as blood minus RBC's. In addition to the blood vascular system all vertebrate possess a lymphatic system. It is colourless or yellowish fluid present in the lymph vessels. It is a mobile connective tissue like blood and is formed by the filtration of blood. (b)  Lymph capillaries:  Small, thin, lined by endothelium resting on a basement membrane and fine whose one end is blind and other end unites to form lymphatic ducts. (c)  Lymphatic ducts or vessels:  Numerous, present in various parts of body. These vessels are like veins as they have all the three layers – tunica externa, tunica media and tunica interna, and are provided with watch pocket or semilunar valves but valves are more in number than veins.

43. Differences between blood and lymph S.No. Characters Blood Lymph (1) RBC Present Absent (2) Blood platelets Present Absent (3) WBC Present , generally 7000/cu mm Present , generally 500-75000/cu mm (4) Plasma Present Present (5) Albumin : globulin Albumin > Globulin Albumin > Globulin (6) Fibrinogen More Less (7) Coagulation property                              More Less (8) Direction of flow Two way, heart to tissues and tissues to heart One way, tissues to heart (9) Rate of flow Fast Slow (10) Glucose, urea and CO2 Less More

44.  Disorders of Circulatory System:   High Blood Pressure (Hypertension):  It is the term for blood pressurethat is higher than normal of 120/80. In the instrument 120 is Systolic / pumping pressure, 80 is Diastolic, resting pressure. If repeated check which shows 140/90 and higher shows Hypertension. It may leads to heart diseases and also affect vital organs like brain and kidney. Coronary Artery Disease (CAD)  : it is also known as Atherosclerosis, due to damage in the blood vessels of heart tissues. Basically it it due to, deposition excess of Calcium, fat, cholesterol and fibrous tissues which makes the lumen of arteries narrower. Angina : It is also known as “angina pectoris”, it is symptom of acute chest pain due to less oxygen supply to heart. Heart Failure : It is the state when heart is not pumping blood effectively to other organs of the body.

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