BIOLOGY LESSON = CIRCULATORY SYSTEM COMPLETE NOTES AND IMPORTANT POINTS

 Blood, tissue fluid and lymph are the three main fluids in our body. 

 Blood transports absorbed digested food, respiratory gases (oxygen and carbon dioxide), excretory materials (urea, excess salt, etc.), hormones, etc. 

 Blood distributes heat and forms a clot at any cut to prevent loss of blood. 

 Plasma is the liquid part and the RBCs, WBCs and platelets are the cellular elements. 

 RBCs (when mature) are biconcave and enucleated. 

(i) Their average life is 120 days; old and dead ones get destroyed in the liver and the spleen, their iron part is retained in the liver and the rest is excreted as bile pigments in the gut. 

(ii) Carry oxygen as oxyhaemoglobin (unstable) which readily dissociates to deliver oxygen to tissues.

 WBCs (leucocytes) protect from disease by 

(i) engulfing bacteria (phagocytosis) and 

(ii) producing antitoxins and antibodies to neutralise poisonous substances. Can squeeze out through capillary walls (diapedesis) to fight germs. 

Are produced in bone marrow and lymph nodes with an average life of about two weeks. 

Two major categories of WBCs : –

– Granular WBCs are of three types – Neutrophils, Eosinophils, Basophils. –

– Non-granular WBCs are of two types – Lymphocytes, Monocytes. 

 Blood platelets (thrombocytes) are produced in bone marrow. Their average life is 3-4 days. They get destroyed in the spleen. They initiate clotting (coagulation) at the site of bleeding. They produce thromboplastin, which in the presence of calcium, converts prothrombin of plasma into thrombin. This in turn, converts soluble fibrinogen of plasma into threads of fibrin that entangle corpuscles to form a clot. The remainder, clear liquid, is serum. 

 Blood groups are important to know for blood transfusion. Blood group "0" is universal donor and blood group "AB" is universal recipient. Blood group Rh (positive or negative) is, in addition, particularly important in pregnancy cases. 

 Heart beat occurs in two main phases – systole (contraction) and diastole (relaxation). 

 There are three valves in the heart to regulate the unidirectional flow of blood. Sharp closing of these valves produces the "Lub" and "Dub" sounds. 
(i) Bicuspid (Mitral) between the left atrium and the left ventricle 
(ii) Tricuspid between the right atrium and the right ventricle 

(iii) Semilunar valves between ventricles and aorta and between ventricles and pulmonary artery 

 There is a double circulation of blood in our heart – pulmonary (lungs) circulation and systemic (body) circulation. 

 Arteries have thick muscular walls and a narrow lumen, and the blood in them flows with jerks (pulse). 

–– Major arteries include : (i) pulmonary (to lungs), aorta giving branches to the head (carotid), the arms (subclavian), the chest (intercostal), the liver (hepatic), stomach, etc. (mesenteric), and the kidneys (renal) 

 Veins have thin muscular walls with valves and a wider lumen, and the blood in them flows continuously. 

–– Major veins include veins from the head and the upper body (superior vena cava), 

–– the arms (subclavian) and the lower body (inferior vena cava)

–– Hepatic portal veins collect blood from the stomach and the intestine and pour it into the liver by means of capillaries which reunite to form the hepatic vein.

 Capillaries are very narrow tubes with no muscles and allow diffusion of substances into and from the tissues. 

 Lymphatic system includes lymph vessels, lymph nodes, lymph glands such as tonsils and lymph organs like the spleen. 

 Spleen is the largest lymphatic organ – it acts as blood reservoir, produces lymphocytes, destroys worn out RBCs and produces RBCs (in embryo). 

 The main function of lymph is defence (by lymphocytes) against germs.

QUESTIONS : 

Q.1. What is circulatory System? 

Ans. Blood is the circulating fluid, the blood flow is powered by a muscular pump called the heart, which together with the vast network of blood vessels constitutes the circular system or cardio - vascular system 

Q.2. Name the components of circulatory system? 

Ans. Blood, Lymph, Blood vessels, and heart.

 

Q.3. What is Blood? 
Ans. Blood is a fluid connective tissue that performs a number of critical functions. 

Q.4. State the function of the blood? OR Function of the circulatory system. 
Ans. Blood is a liquid connective tissue and thus performs functions such as 
        1. Transportation of respiratory gases, hormones, nutrients. 
        2. Regulation of body temperature (thermoregulation). 
        3. Prevention against blood loss (through the clotting process). 
        4. Protection against invasion of foreign microbes through antibody and anti - toxin production (immunity) 

Q.5. What is blood composed of? 
Ans. The blood is composed of two main components 
         a) Plasma and 
         b) Blood corpuscles 

Q.6. What are blood corpuscles. 
Ans. They consist of the cellular part of the blood, about 42 - 45% of blood is made up of blood corpuscles, they are Erythrocytes (RBC’s), Leucocytes (WBC’s) and Thrombocytes (platelets). 

Q.7. What is blood plasma? 
Ans. The blood plasma is the fluid part, about 55 - 58% of blood is made up of plasma which contains, 90% water, 7 - 8% Blood proteins, 1% salt and other substances like hormones, respiratory gases, nutrients and excretory products. 

Q.8. What are erythrocytes? 
Ans. They are red blood cells, devoid of nucleus. They contain respiratory pigments haemoglobin which imparts red colour to blood. 

Q.9. Where are red blood cells produced and destroyed? 
Ans. The red blood cells are produced in the marrow of long bones, while in embryonic stage they are formed in the liver and spleenThe worn out RBCs are destroyed in the spleen, liver and bone marrow.

 
Q.10. Give functions of erythrocytes. 
Ans. The functions of erythrocytes are as follows.

1. To transport oxygen to the cells and tissue of the body, with the help of haemoglobin, in the form of oxyhaemoglobin. 

2. It also carries away carbon dioxide to the lungs for elimination. 

3. They impart red colour to the blood. 

Q.11. What are Leucocytes? 

Ans. Leucocytes are WBCs are nucleated cells, ranging from 8 to 20 (microns). The main types are agranulocytes and granulocytes. They are the defence cells of the body. 

Q.12. Explain the types of Leucocytes (WBCs). 

Ans. There are two types of WBCs : 

         A] Agranulocytes : These have clear cytoplasm. They develop from lymph nodes and red bone marrow. They are of two types lymphocytes and monocytes. 

         (i) Lymphocytes : Round nucleus, phagocytosis, antigen - antibody reaction (immunity) 

         (ii) Monocytes : Kidney shaped nucleus, phagocytosis. 

         B] Granulocytes : These develop from red bone marrow, have granules in the cytoplasm and possess lobed nuclei. Three kinds of granulocytes are present, they are Eosinophils, Basophils and Neutrophils. 

        (i) Eosinophils : The nucleus is bilobed and the lobes are connected by strands. The cytoplasmic granules get stain with red acidic dyes like Eosin. 

        (ii) Basophils : The nucleus is large, irregular in shape. They stain with basic dyes like methylene blue. 

        (iii) Neutrophils : They are multilobed i.e., have 2 to 6 lobes. The granules stain with neutral dyes.

Q.13. Enlist the functions of leucocytes Functions of leucocytes 

Ans a) Phagocytosis : Neutrophils and monocytes engulf and destroys the foreign bodies entering the blood. 

b) Diapedesis: They move in amoeboid fashion and engulf microbes by squeezing out of blood capillaries. 

c) Production of antibodies and antitoxins : Lymphocytes are involved in the production of antibodies while basophils and eosinophils produce anti-toxins. 

d) Immunity: Immunity is the ability of an organism to resist infections. 

Q.14. What is diapedesis? 

Ans. Most of the WBCs are amoeboid and can produced pseudopodia with which they can squeeze through the walls of the capillaries into the tissues . This is called diapedesis. 

Q.15. What are platelets (Thrombocytes)? 

Ans. Blood platelets are oval or special cells numbering between 2,50,000 and 4,00,000 / mm3 , lifespan is 2 – 3 days. They are produced in Red bone marrow from giant cells like Megakaryocytes. Human and mammalian platelets do not have nuclei. 

Q.16. Enlist the functions of blood platelets. 

Ans. (a) Clotting of blood 

(b) Phagocytosis

 (c) Prevent undue loss of blood

 (d) Healing of wounds 

Q.17. What are anticoagulants?

 Ans. Anticoagulants like heparin are present in blood which prevents blood clot. 

Q.18. What is blood blister? 

Ans. Some times an injury or a sharp pinch can cause the blood to clot inside blood vessels. This is called blood blister and is visible on the skin surface as a bluish mark. 

Q.19. Enlist the step in clotting of blood? 

Ans. Blood clotting prevents blood loss when blood vessels are damaged. This clotting is achieved in 3 steps. 

        (i) The platelets release a chemical compound thromboplastin at the site of injury. 

        (ii) Thromboplastin converts the inactive prothrombin present in plasma into active thrombin in the presence of Vit.K and calcium. 

        (iii) The thrombin converts the soluble fibrinogen into insoluble fibrin fibres.  

        These fibrin fibres form a mesh in which dead cells of the blood are entrapped and a thrombus (clot) is formed, which prevents the further loss of blood and helps in healing of wounds. 

Q.20. Mention the abnormalities of Blood cells. 

Ans. a) If the number of RBC’s increase to a high level condition is called Polycythemia. 

b) If the number of WBC’s increase above the number of RBCs the condition is called Leukemia. 

c) If RBC number decreases the condition is called Erythropenia 

d) If the number of WBC’s fall the condition is called Leucopenia. 

Q.21. How many blood groups are seen in a human beings? Explain it in brief. 

Ans. There are four blood groups in human beings. 

a) Blood group A : Individuals with agglutinogen A 

b) Blood group B : Individual with agglutinogen B 

c) Blood group AB : Both agglutinogen are present 

d) Blood group O : Neither of agglutinogen are present 

Q.22. What are blood groups? 

Ans. A groups of people having blood with similar agglutinogen (antigen) on its RBC’s are said to belong to the same blood group. 

Q.23. What are Rhesus factor? 

Ans. It is a substance present in the red blood cells of most people. Such people are said to be Rhesus positive (Rh positive) People who do not have this substance in their blood, are said to be Rhesus negative (Rh negative) 

Q.24. What are blood vessels ? Explain the type of blood vessels. 

Ans. Blood vessels form a network of tubes that carry blood away from the heart, transport it to the tissues of the body and then return it to the heart. 

There are three main types :

1. Arteries : Arteries carry blood from the heart to the tissues. The aorta is the largest artery in human body, they further divide to form still smaller tubes called arterioles. Arteries generally carry oxygenated blood except pulmonary artery. The wall of the arteries are thick and muscular being composed of elastic and collagen fibers. The arteries are generally deep seated and the blood flows through the arteries under pressure. 

2. Veins : Veins carry blood towards the heart. The blood flowing through them is generally deoxygenated except pulmonary vein. The walls of the veins are much thinner than the arteries. Many veins, especially those in the limbs, which bring blood against the force of gravity contain valves that prevent backflow. 

3. Capillaries : They are thin-walled microscopic blood vessels made upto single layer of epithelial tissue. Capillaries branch to form an extensive network throughout the tissue. Its branching nature helps to increase the surface area and the thin walls allow rapid exchange of materials between blood and tissue cells.

Q.25. What is Heart Sound? 

Ans. The first sound ‘LUBB’ is produced when the atrio-ventricular valves gets closed sharply at the start of ventricular systole. The second sound “DUP” is produced when at the begining of ventricular diastole, the semilunar valves at the roots of aorta and pulmonary artery get closed. 

Q.26. What is a pulse? 

Ans. Pulse is a wave of distension and recoil. It is felt in some of the superficial artery such as the radial artery of the wrist. 

Q.27. What is hepatic portal vein? 

Ans. The hepatic portal vein is formed by the union of the capillaries in the liver. The vein carries the blood which contains nutrients absorbed from the alimentary canal to the liver. The liver checks these substances before they pass into general circulation by detoxification and deamination.

Q.28. Describe the valves present in the heart. 

Ans. Valves of the Heart Valves are muscular flaps which prevent the blood which has once passed through it, to flow back through it. The opening and closing of valve is due to pressure difference across the valves. 

Two types of heart valves are distinguished - the atria-ventricular valves and the semi-lunar valves. 

1. The atrio-ventricular valves: These valves separate the atria from the ventricles. They consist of fibrous tissues that grow out of the walls of the heart. The pointed ends of the flaps (or cusps) project into the ventricles. Tendon-like fibrous cords called chordae tendinae connect the pointed ends to small conical projections called papillary muscles, located on the inner surface of the ventricles. 

a. Tricuspid valve (Right atrio-ventricular valve): The right side of the heart possess the tricuspid valve (with three cusps) which prevents the backflow of the blood into the right auricle during contraction of the left ventricle. 

b. Bicuspid valve (Mitral): Located on the left side of the heart, the bicuspid valve consisting to two flaps prevents the backflow of the blood into the left atrium during contraction of the ventricle. 

2. Semilunar valves : These have three half-moon-shaped folds (pockets). Located in the arteries leaving the heart, they prevent the blood from flowing back into the heart. 

a. Pulmonary semilunar valve: This valve lies in the opening where the pulmonary trunk leaves the right ventricle. It prevents the backflow of the blood into the right ventricle during its relaxation. 

b. Aortic semilunar valve: Located at the opening between the left ventricle and aorta, this valve prevents the flow of blood from the aorta into the left ventricle during its relaxation.

Q.29. State the two phases of cardiac cycle. 

Ans. The cardiac cycle comprises of two phases, the systole and the diastole. 

(a) The systole: This is the phase during which the heart contracts. During systole, the auricle sends blood into the ventricles. Time taken for arterial systole is 0.1 — 0.16 sec. and ventricular systole is 0.3 secs. 

(b) The diastole: This is the phase of rest or relaxation of the heart muscles. Arterial diastole lasts for 0.7 - 0.76 sec and ventricular diastole lasts for 0.5 — 0.56 sec. The entire cardiac cycle lasts for about 0.85 seconds. 

Q.30. State a point of difference between Systole and Diastole. 

Ans. Systole : It is phase of contraction of a chamber of the heart. 

Diastole : It is the phase of relaxation of a chamber of the heart.

Q.31. What is Cardiac Cycle? 

Ans. (a) Blood flows through the heart with a definite pattern of systoles and diastoles. The whole sequence of events in the heart beat constitute a cardiac cycle. 

(b) It lasts for about 0.8 secs. 

Q.32. How many times per day does the human heart beat ? 

Ans. 72 beats per minute. 

72 × 60 mins x 24 hours = 1,03,680 (more than one lakh times per day)

Q.33. What is Double Circulation? 

Ans. Heart is said to have double circulation because the blood passes through the heart twice. 

1. It first leaves throught the right ventricle, goes to the lungs, and then returns to the heart (left artium) 

2. Leaves through the left ventricle, circulates through the body, and again returns to the heart (right atrium) 

Q.34. What is Pulmonary Circulation? 

Ans. Pulmonary Circulation: The pulmonary circulation is maintained by the right side of the heart. It begins in the right ventricle which expels the blood into the pulmonary trunk. The blood flows into the vascular system of the lungs, becomes oxygenated and returns to the left atrium through the pulmonary veins.

Q.35. What is Systemic Circulation? 

Ans. This circulation is maintained by the left ventricle which sends the blood into the aorta. Two of the several sub-division of the systemic circulation are coronary (cardiac) circulation and hepatic portal circulation. 

Q.36. Give Chambers of the Heart? 

Ans. Chambers of the Heart The interior of the heart is divided into four chambers which receive the circulating blood. 

1. The Atria (auricles): The two superior chambers are called the right and left atria. The atria are seperated by a partition called the inter-atrial septum. Located in the upper wall of the right atrium is the sino-atrial node (SAN) or the pacemaker. The pacemaker is a specialized tissue which regulates the contraction and relaxation of the heart muscles. 

2. The Ventricles : The two inferior chambers of the heart are the right and left ventricles. They are seperated from each other by an interventricular septum. The atria and ventricles are separated by connective tissue that also form the valves. 

Q.37. What is Lymph ? Give its functions. 

Ans. Lymph 

1. Lymph is a colourless fluid derived from the blood. 

2. It is similar in composition to plasma and contains lymphocytes, blood proteins, waste matters but no erythrocytes. 

Function of Lymph 

1. Lymph provides a free exchange of substances between the blood and protoplasm of the cells. 

2. It collects waste materials from the cells and brings them to the blood. 

3. It transports nutrients to the tissues. 

4. Lymphocytes of lymph play an important role in fighting against infection. 

5. Lymph maintains the body temperature distributing the body heat. 

6. It absorbs fats from the villi of small intestine and supplies it to the venous blood. 

Q.38. Describe the internal structure of the Heart / Its conducting system. 

Ans. Conducting System Human heart is an autonomous organ controlled by autonomic nervous system and flow of blood into it. It is a highly rhythmic organ controlled by a precise conducting system. 

The system consists of the following components : 

A) Sinu-Auricular node (SAN) : It is a highly sensitive node situated in the right auricle attached to the posterior wall of the auricle. It lies below the opening of superior vena cava. It generates a wave of contraction after receiving adequatic amount of blood (70ml.) 

B) Auriculo-Ventricular node (AVN) : It is another sensitive node present in the right auricle attached with auricule ventricular septum. It receives the wave of contraction and transfer the same to Bundle of His. 

C) Bundle of His : It is bundle of conducting fibres originating from AVN. It lies in the inter ventricular septum. It divides into 2 lateral branches right and left. Both the branches reach to the heart apex and travels into the lateral wall of the ventricle. 

D) Purkinje System : It is an anstomosing (dense) network of conducting fibres arising from the Bundle of His. It lies in the lateral wall of ventricles. The conducting system controls the flow of blood through various chambers of the heart. It regulates the flow of blood and generates adequate blood pressure. It controls the heart beat. 

Q.39. Describe the Heart Beat in Humans ? 

Ans. Heart Beat It is also known as cardiac cycle. It is completed in 0.8sec. It is completed in the following 3 Phases: 

Phase - I : Also known as auricular systole, it is completed in 0.1sec. In this phase the auricle contract and push the blood into respective ventricles. 

Phase- II : Also known as vertricular systole. It is completed in 0.3sec. The ventricles contract and push the blood into pulmonary artey and aorta. The right ventricle pushes the blood in pulmonary artey whereas the left ventricle pushes the blood in aorta. 

Phase - III : Also known as general pause. It is completed in 0.4sec. In this phase the auricle and ventricle relax to allow the blood to be collected in the auricles. 

Q.40. What is Heart Rate ? 

Ans. It is the total number of beats per minute. In a normal healthy human it is found to be 72 times per minute.