CBSE Class 11 Biology Body Fluids And Circulation Notes

Body Fluids and Circulation Class 11 Notes

POINTS TO REMEMBER :
• Blood: A special connective tissue that circulates in principal vascular system of man and other vertebrates consisting of fluid matrix, plasma and formed elements.

Plasma :
• The liquid part of blood or lymph which is straw coloured, viscous fluid constituting nearly 55 per cent of blood.
• 90-92 percent of plasma is water and 6-8% proteins.
• Fibrinogen, globulin and albumins are the major protein found in plasma.
• Fibrinogen is required in blood clotting or coagulation of blood.
• Globulins involved in defense mechanism of the body.
• Albumin helps in osmotic balance of blood.
• Plasma also contains small amounts of minerals, glucose, amino acids, lipids etc.
• Plasma without the clotting factors is called serum.

Formed elements :

Erythrocytes :
• Also known as RBC (red blood cells) is the most abundant of all the cells of blood.
• 5 – 5.5 million RBC found per mm-3 of the blood.
• Produced from the red bone marrow in the adult.
• RBCs devoid of nucleus in most of mammals.
• Biconcave in shape
• Red in color due presence of complex conjugated protein called haemoglobin.
• 12-16 gm of haemoglobin present per 100 ml of blood in a healthy adult.
• RBCs have average life span of 120 days after which is destroyed in the spleen.
• Spleen is commonly known as the graveyard of RBCs.

Leukocytes :
• Also known as white blood cells (WBC).
• They are colorless due to lack of haemoglobin.
• They are nucleated and relatively lesser in number which averages 6000-8000 mm-3 of blood.
• We have two main category of WBC;

• Granulocytes
o Neutrophils
o Basophils
o Eosinophils

• Agranulocytes.
o Lymphocytes
o Monocytes.

• Neutrophils (60-65%) of the total WBCs are phogocytic in nature.
• Basophils (0.5-1 %), secretes histamine, serotonin and heparin and also involved in inflammatory reactions.
• Eosinophils (2-3 %) resist infection and also associated with allergic reaction.
• Lymphocytes (T cells and B cells) constitute 20-25 percent and involved in the immune response of the body.
• Monocytes (10-15%), becomes macrophages.

Thrombocytes :
• Also known as blood platelets.
• Produced from fragmentation of megakaryocytes.
• Blood normally contain 1, 500, 00 – 3, 500, 00 platelets mm-3.
• Involved in releasing thromboplastin required to initiate blood coagulation.

BLOOD GROUPS :
• Two blood grouping mechanisms ABO and Rh system.

ABO grouping :
• ABO grouping is based on the presence or absence of two surface antigens on the RBCs namely A and B.
• Plasma of different individuals contains two natural antibodies, anti ‘A’ and ‘B’.

Blood Groups

• In a mismatched transfusion the antigen of the donor reacts with antibody of the recipient to cause a reaction calledclumping of agglutination.
• Person with blood group ‘O’ has no antigen hence can donate blood anybody, called universal donor.
• Person with blood group ‘AB’ has no antibody in his plasma hence can receive blood from anybody, called universal recipient.

Rh grouping :
• Another antigen, the Rh antigen similar to one present in Rhesus monkeys (hence Rh), is also observed on the surface of RBCs on majority (nearly 80 %).
• Person with Rh antigen is said to be Rh positive (Rh+).
• Person without Rh antigen is said to be Rh negative (Rh-).
• Person with Rh- blood transfused with Rh+ blood, forms anti Rh antibody and destroy the Rh+ RBCs.
• A special case of Rh incompatibility (mismatching) has been observed between the Rh- bloods of pregnant mother with the Rh+ blood of the foetus.
• During parturition the Rh+ foetal blood mixed with the Rh- maternal blood, hence anti Rh antibody formed in mothers blood.
• In successive pregnancy the anti Rh antibody from mother’s blood leaks into the foetal blood and destroy the Rh+ RBCs.
• This caused HDN (haemolytic disease in new born) or Erythroblastosis foetalis.
• This can be prevented by administering anti-Rh antibody to the mother immediately after the delivery of the first child.

COAGULATION OF BLOOD :
• Injury to the blood vessel leads to loss of blood called haemorrhage.
• There is an intrinsic mechanism to stop haemorrhage is called haemostasis or coagulation of blood or blood clotting.

• Clot or coagulum is formed mainly of a network of threads called fibrins in which dead and damaged formed elements of blood are trapped or entangled.
• Fibrin is formed by the conversion of inactive fibrinogens in the plasma by an enzyme called thrombin.
• Thrombin formed from inactive prothrombin of the plasma due to presence of enzyme thrombokinase.
• All these activation required the initial clotting factor called thromboplastin either released from the injured tissue or platelets.
• Calcium ions play a very important role in the coagulation of blood.

Lymph
• The colorless mobile fluid connective tissue drains into the lymphatic capillaries from the intercellular spaces.

Composition :
o It is composed of fluid matrix, plasma, white blood corpuscles or leucocytes.
o Contains less amount of protein than plasma.
o Devoid of RBCs.

Functions :
o It drains excess tissue fluid from extra cellular spaces back into the blood.
o It contains lymphocytes and antibodies.
o It transport digested fats.

CIRCULATORY PATHWAYS :

Open circulatory system :
• Found in arthropods and mollusks.
• Blood from the heart pumped into the open spaces in the body cavity called sinuses.
• The body cavity remained filled with blood (haemolymph) called haemocoel.

Closed circulatory system :
• Found in annelids, echinoderms and all chordates.
• Blood from the heart pumped into definite blood vessels.
• Blood circulated in a wide network of blood vessel throughout the body.
• Blood circulated in a regulated manner.

Heart and circulation in vertebrates :
• Fishes: have 2 chambered hearts with one atrium and one ventricle.
• Amphibian and reptilian (except crocodile) has three chambered heart with two atria and one ventricle.
• Crocodiles, birds and mammals possesses a 4-chambered heart with two atria and two ventricles
• In fishes the two chambered heart pumped deoxygenated blood to the gills for oxygenation and then circulated to the body. (singlecirculation)
• In amphibians and reptilians the left atrium receives oxygenated blood from the lungs and right atrium receives deoxygenated blood from the body. Blood from the atria pumped into the ventricle from which the mixed blood pumped into the body. (Incomplete double circulation).
• In birds and mammals oxygenated and deoxygenated blood received by left and right atria respectively passed into ventricle of their side. The ventricles pump it out without any mixing up. (double circulation)

HUMAN CIRCULATORY SYSTEM :

Heart :
• Originated from embryonic mesoderm.
• Situated in the thoracic cavity, in between two lungs, slightly tilted towards left.
• It has the size of the clenched fist.
• Heart is covered by a double walled bag, pericardium.
• Our heat is four chambered, two relatively smaller upper chamber called atria and two lower larger chamber calledventricles.
• Two atria are separated by thin muscular wall called inter-atrial septum.
• A thick walled inter-ventricular septum separates two ventricles.
• Atrium and ventricle of same side is separated by a thick fibrous tissue called the atrio-ventricular septum.
• Each of atrio-ventricular septa is provided with an opening through which the atrium and ventricle of same side are connected, called atrio-ventricular opening.
• Right atrio-ventricular opening is guarded by tricuspid valve.
• Left atrio-ventricular opening is guarded by bicuspid or mitral valve.
• The right ventricle opens into systemic aorta and left ventricle opens into pulmonary aorta.
• Both the aorta is guarded by semilunar valves.
• The valves in the heart allow unidirectional flow of blood i.e. from atria to ventricles and from ventricles to their respective aorta.

Conducting system of human heart :
• The entire heart is made of cardiac muscles.
• The wall of the ventricle is much thicker than the atria.
• A patch of nodal tissue is present in the right upper corner of the right atrium called the Sino-atrial node(S A Node).
• Another nodal tissue present in the posterior to the inter-ventricular septum called A V Node (Atrio-ventricular node).
• A bundle of nodal fibres , atrio-ventricular bundle ( AV bundle) continued as A V bundle through the inter-ventricular septum and divided into right and left A V bundle, also called bundle of His.
• The bundle of His gives rise to profuse branches to the wall of the ventricles called perkinji fibres.
• S A node generates the force of contraction for auto rhythmicity of heart, hence called pace maker of the heart.
• Our heart normally beats 70-75 times in minutes (average of 72 beats per minutes).

Cardiac cycle :
• The cyclic events takes place in each heart beat is called one cardiac cycle.
• Lets starts with all the four chambers of heart are in a relaxed state i.e. in joint diastole.
• As the tricuspid and bicuspid valves are open, blood from the pulmonary veins and vena cava flows into the left and right ventricles respectively through left and right atria.
• Semilunar valves are closed at this stage.
• SAN generates the action potential which stimulates contraction of both atria, called atrial systole.
• This increases the blood flow from atria to their respective ventricles by 30 %.
• The action potential from SAN passed to AVN and then to perkinji fibres through AV bundles. This initiates ventricular systole. The atria undergo relaxation (diastole).
• During ventricular systole the intra-ventricular blood pressure increases that lead to closing of tricuspid and bicuspid valves leads to production of first heart sound called lub sound.
• Further increase in pressure leads to opening of semilunar valves.
• Oxygenated blood from the left atrium pumped into systemic aorta and deoxygenated blood from the right atrium pumped into the pulmonary aorta.
• Ventricular systole followed by ventricular diastole.
• Intra-ventricular blood pressure decreases leads to closing of semilunar valves causing second heart sound (dub).
• As the ventricular pressure declines further there is opening of bicuspid and tricuspid valves, blood from the atria flows into the ventricles freely.
• The ventricle and atria relaxed simultaneously called joint diastole.
• This sequential event in the heart which cyclically repeated called cardiac cycle.
• The heart beats 72 times per minutes.
• Each cardiac cycle takes 0.8 sec to complete.
• During a cardiac cycle the ventricles pumped 70 ml blood to the aorta called stroke volume.
• Stoke volume multiplied by heart rate (heart beat per min.) gives the cardiac output.
• Cardiac out put for human heart is 5000 ml.

Electrocardiograph (ECG) :
• ECG is a graphical representation of the electrical activity of the heart during a cardiac cycle.
• Each peak in the ECG is identified with a letter from P to T that corresponds to a specific electrical activity of the heart.
• The P-wave represents the electrical excitation (or depolarization) of the atria.
• The QRS complex represents the depolarization of the ventricles.
• The ventricular contraction starts shortly after the Q and marks the beginning of the ventricular systole.
• T-wave represents the ventricular diastole (repolarisation).

DOUBLE CIRCULATION :
• Pulmonary circulation: Right ventricle (deoxygenated blood) → pulmonary artery → lungs (oxygenation) → pulmonary vein (oxygenated blood) → left atrium.
• Systemic circulation: left ventricle (oxygenated blood) → systemic aorta → body (deoxygenated) →vena cava (deoxygenated blood) → right atrium.
• Portal system: the deoxygenated blood collected from one organ by means of a vein (portal vein) entered into another organ before it is delivered to the systemic circulation.
• Hepatic portal system: the hepatic portal vein carries deoxygenated blood from the intestine to the liver before it is delivered to the systemic circulation by means of hepatic vein.
• Coronary circulation: A special blood vessel (coronary vessel) is present in our body exclusively for the circulation of blood to and from the cardiac musculature.

REGUALTION OF CARDIAC ACTIVITY :
• Rhythmicity of human heart is regulated by specialized (nodal tissues), hence the heart is called myogenic.
• A special neural centre in the medulla oblongata can regulate cardiac function moderately.
• Neural signal through sympathetic nerve can increase the heart rate and cardiac output.
• Neural signal through parasympathetic nerve can decrease the heart rate and cardiac output.
• Hormones of adrenal medulla (adrenaline) also increase the cardiac output.

DISORDERS OF CIRCULATORY SYSTEM :

Hypertension :
• Hypertension is the term for blood pressure that is higher than normal (120/80).
• 120 mm Hg is the systolic pressure and 80 mm Hg is the diastolic pressure.
• Sustained blood pressure of 140/90 or higher is said to be hypertension.
• Blood pressure is measured by sphygmomanometer.
• High blood pressure leads to heart disease and also affects vital organ like brain and kidney.

Coronary Artery Disease (CAD) :
• Often referred as atherosclerosis, affects the blood supply to the heart muscles.
• It is caused by deposition of calcium, fat, cholesterol and fibrous tissue which makes the lumen of coronary artery narrower.

Angina :
• It is also known as ‘angina pectoris’.
• Causes acute chest pain due to inadequate oxygen supply to the heart.
• It occurs due to blockade to coronary artery.

Heart failure :
• It is the state of the heart when it is not pumping blood effectively
• Cardiac arrest: the heart stops beating.
• Heart attack: heart muscle damaged suddenly by an inadequate blood supply to the heart muscles.
• In a mismatched transfusion the antigen of the donor reacts with antibody of the recipient to cause a reaction calledclumping of agglutination.
• Person with blood group ‘O’ has no antigen hence can donate blood anybody, called universal donor.
• Person with blood group ‘AB’ has no antibody in his plasma hence can receive blood from anybody, called universal recipient.

MCQ Questions for NCERT Class 11 Biology Digestion and Absorption

Ques. Systemic heart refers to
(a) the heart that contracts under stimulation from nervous system
(b) left auricle and left ventricle in higher vertebrates
(c) entire heart in lower vertebrates
(d) the two ventricles together in humans. 

Answer: B

Question. Which of the following cytoplasmic granules contain histamine?
(a) Basophils
(b) Eosinophils
(c) Acidophils
(d) Neutrophils

Answer. A

Question. If one litre of blood is drawn out of 5 litres from the body of man, how much blood would be left by the next day?
(a) 5 litres
(b) 4 litres
(c) 4.5 litres
(d) 3.0 litres

Answer. A

Question. The heart sound “dub” is caused by the
(a) opening of mitral valve
(b) closing of mitral valve
(c) closing of semilunar valve
(d) opening of tricuspid valve.

Answer. C

Question. Select the correct statement about WBC.
(a) Do not have cell organelles including nucleus.
(b) Its formation is called erythropoiesis.
(c) Vitamin B12 and folic acid stimulate the maturation of WBC.
(d) Can squeeze through blood capillaries

Answer. D

Question. pH of blood
(a) is greater than 9
(b) ranges between 7-8
(c) is less than 7
(d) none of these.

Answer. B

Question. The number of which cells increase duringallergy? 
(a) Monocytes
(b) Eosinophils
(c) Erythrocytes
(d) Thrombocytes

Answer. B

Question. Both RBC and WBC are formed in the
(a) thymus
(b) adrenal
(c) thyroid
(d) bone marrow.

Answer. D

Question. Anaemia refers to
(a) lack of Hb
(b) lack of WBCs
(c) lack of blood
(d) lack of thrombocytes.

Answer. A

Question. Read the following statements and choosethe cor rect option.
A. Human heart is an ectodermal derivative.
B. Mitral valve guards the opening between
the right atrium and left ventricle.
C. SAN is located on the left upper corner of the right atrium.
D. Stroke volume × Heart rate = Cardiac output
(a) Only A is correct.
(b) A and B are correct.
(c) B and D are correct.
(d) Only D is correct.

Answer. D

Question. Select the correct statement.
(a) Capillaries are made up of three layers.
(b) The walls of the arteries are thick and muscular.
(c) In veins, flow of blood is fast.
(d) All of these

Answer. B

Question. Lymph is colourless because
(a) WBCs are absent
(b) WBCs are present
(c) RBCs are present
(d) RBCs are absent.

Answer. D

Ques. Impulse of heart beat originates from
(a) SA node
(b) AV node
(c) vagus nerve
(d) cardiac nerve.

Answer: A

Question. Select the incorrect difference between open and closed circulatory system.
Open circulatory system                         Closed circulatory system
(a) Blood flows at high pressure.           Blood flows at low pressure.
(b) Exchange of                                         Exchange of material is direct material occurs through tissue fluid.
(c) It is less efficient.                                It is more efficient
(d) Found in leech, prawns, etc.             Found in earthworm, squids, etc.

Answer. A

Ques. Rate of heart beat is determined by
(a) Purkinje fibres
(b) papillary muscles
(c) AV node
(d) SA node. 

Answer: D

Ques. The correct route through which pulse-makingimpulse travels in the heart is 
(a) SA node → Purkinje fibres → bundle of His → AV node → heart muscles
(b) SA node → AV node → bundle of His → Purkinje fibres → heart muscles
(c) AV node → bundle of His → SA node → Purkinje fibres → heart muscles
(d) AV node → SA node → Purkinje fibres → bundle of His → heart muscles. 

Answer: B

Ques. The neurogenic heart is the characteristic feature of
(a) humans
(b) arthropods
(c) rabbits
(d) rats. 

Answer: B

Ques. The heart sound ‘dup’ is produced when
(a) mitral valve is closed
(b) semi-lunar valves at the base of aorta get closed
(c) tricuspid valve is opened
(d) mitral valve is opened. 

Answer: B

Ques. The pacesetter in the heart is called
(a) sino-atrial node (SAN)
(b) atrio-ventricular node (AVN)
(c) Purkinje fibres
(d) papillary muscle. 

Answer: B

Ques. Tricuspid valve is found in between
(a) sinus venosus and right auricle
(b) right auricle and right ventricle
(c) left ventricle and left auricle
(d) ventricle and aorta. 

Answer: B

Ques. The hepatic portal vein drains blood to liver from
(a) stomach
(b) kidneys
(c) intestine
(d) heart. 

Answer: A

Ques. Blood pressure in the pulmonary artery is
(a) more than that in the pulmonary vein
(b) less than that in the venae cavae
(c) same as that in the aorta
(d) more than that in the carotid. 

Answer: A

Ques. In mammals, which blood vessel would normally carry largest amount of urea?
(a) Hepatic vein
(b) Hepatic portal vein
(c) Renal vein
(d) Dorsal aorta

Answer: A

Ques. Which one of the following animals has two separate circulatory pathways?
(a) Whale
(b) Shark
(c) Frog
(d) Lizard

Answer: A

Ques. Arteries are best defined as the vessels which
(a) supply oxygenated blood to the different organs
(b) carry blood away from the heart to different organs
(c) break up into capillaries which reunite to form a vein
(d) carry blood from one visceral organ to another visceral organ. 

Answer: B

Ques. Fastest distribution of some injectible material/medicine and with no risk of any kind can be achieved by injecting it into the
(a) muscles
(b) arteries
(c) veins
(d) lymph vessels. 

Answer: C

Ques. Difference between pulmonary artery and pulmonary vein is that, the pulmonary artery has
(a) no endothelium
(b) valves
(c) thicker walls
(d) oxygenated blood. 

Answer: C

Ques. In which point, pulmonary artery is different from pulmonary vein?
(a) Its lumen is broad.
(b) Its wall is thick.
(c) It has valves.
(d) It does not possess endothelium. 

Answer: B

Ques. Which vertebrate organ receives only oxygenated blood?
(a) Spleen
(b) Liver
(c) Gill
(d) Lung 

Answer: A

Ques. In veins, valves are present to check backward flow of blood flowing at
(a) atmospheric pressure
(b) high pressure
(c) low pressure
(d) all of these. 

Answer: C

Ques. Blood capillaries are made of
(a) endothelium, connective tissue and muscle fibres
(b) endothelium and muscle fibres
(c) endothelium and connective tissue
(d) endothelium only.

Answer: D

Ques. Wall of blood capillary is formed of
(a) haemocytes
(b) parietal cells
(c) endothelial cells
(d) oxyntic cells.

Answer: C

Ques. Splenic artery arises from
(a) anterior mesenteric artery
(b) coeliac artery
(c) posterior mesenteric artery
(d) intestinal artery. 

Answer: B

Ques. A vein possesses a large lumen because
(a) tunica media and tunica externa form a single coat
(b) tunica interna and tunica media form a single coat
(c) tunica interna, tunica media and tunica externa are thin
(d) tunica media is a thin coat. 

Answer: D

Ques. Arteries carry oxygenated blood except
(a) pulmonary
(b) cardiac
(c) hepatic
(d) systemic. 

Answer: A

Ques. How do parasympathetic neural signals affect the working of the heart?
(a) Reduce both heart rate and cardiac output.
(b) Heart rate is increased without affecting the cardiac output.
(c) Both heart rate and cardiac output increase.
(d) Heart rate decreases but cardiac output increases. 

Answer: A

Ques. Which one of the following statements is correct regarding blood pressure?
(a) 130/90 mm Hg is considered high and requires treatment.
(b) 100/55 mm Hg is considered an ideal blood pressure.
(c) 105/50 mm Hg makes one very active.
(d) 190/110 mm Hg may harm vital organs like brain and kidney.

Answer: D

Ques. Given below are four statements (i-iv) regarding human blood circulatory system.
(i) Arteries are thick-walled and have narrow lumen as compared to veins.
(ii) Angina is acute chest pain when the blood circulation to the brain is reduced.
(iii) Persons with blood group AB can donate blood to any person with any blood group under ABO system.
(iv) Calcium ions play a very important role in blood clotting.
Which two of the above statements are correct?
(a) (i) and (iv)
(b) (i) and (ii)
(c) (ii) and (iii)
(d) (iii) and (iv) 

Answer: A

Ques. The thickening of walls of arteries is called
(a) arteriosclerosis
(b) arthritis
(c) aneurysm
(d) both (b) and (c). 

Answer: A

Ques. An adult human with average health has systolic and diastolic pressures as
(a) 120 mm Hg and 80 mm Hg
(b) 50 mm Hg and 80 mm Hg
(c) 80 mm Hg and 80 mm Hg
(d) 70 mm Hg and 120 mm Hg.

Answer: A

Important Questions for NCERT Class 11 Biology Digestion and Absorption

Short Answer Type Questions

Question. What is meant by double circulation? What is its significance?
Answer. The type of blood circulation in which oxygenated blood and deoxygenated blood do not get mixed is termed double circulation. It includes systemic circulation and pulmonary circulation. The circulatory pathway of double circulation is given in the following flow chart. (IMG 131) Significance of double circulation : Double circulation or separation of systemic and pulmonary circulations provides a higher metabolic rate to the body and also allows the two circulations to have different blood pressures according to the need of the organs they supply.

Question. What is the role of hormones in regulating the cardiac activity?
Answer. Hormones play an important role in regulating the cardiac activity. The substance secreted at the end of the vasoconstrictor nerves is called norepinephrine (noradrenaline). It regulates the blood pressure under normal conditions. Norepinephrine causes constriction of essentially all the blood vessels of the body and thus increases the heart rate. Another hormone called epinephrine (adrenaline) is also secreted by the medulla of the adrenal endocrine gland. It also acts directly on the blood vessels, usually to cause vasoconstriction. Epinephrine has a greater effect on heart activity than norepinephrine. It also causes weak constriction of the blood vessels of the muscles in comparison with a much stronger constriction that results from norepinephrine. Thus adrenal medullary hormones increase the heart beat.

Question. What is the effect of the following on the heart rate?
(a) Sympathetic nervous system
(b) Noradrenaline
(c) Fever
Answer. (a) Sympathetic nervous system accelerates the heart beat. It constricts arteries that raise blood pressure. (b) Refer to answer  29. (c) Fever causes an increase in heart rate as an increase of a single degree of temperature increases heart rate of about 10 beats per minute.

Question. Differentiate between arteriosclerosis and atherosclerosis.
Answer. Differences between arteriosclerosis and atherosclerosis are as follows: 

Question. Differentiate between arteries and veins.
Answer. Differences between arteries and veins are as follows: 

Question. What are the factors that affect pulse rate?
Answer. The factors that affect the pulse rate are as follows: (i) The pulse rate in children is more rapid than in adults. (ii) The pulse rate is more rapid in the females than in the males. (iii) When the person is in standing position the pulse rate is more rapid than when he/she is lying down. (iv) When any strong emotion is experienced the pulse rate is increased, for example, anger, excitement, fear, etc. (v) Any exercise increases the rate of the pulse. (vi) A temperature increase of just 1°C raises the heart rate by about 10 beats per minute. This is why pulse increases substantially in a person suffering from fever.

Question. Explain the different steps involved in the process of blood clotting.
Answer. Blood clotting occurs in the following steps: (i) At the site of an injury, the blood platelets disintegrate and release a phospholipid, called platelet factor-3 or platelet thromboplastin. Injured tissues also release a lipoprotein factor called thromboplastin. These two factors combine with calcium ions and certain proteins of the blood plasma to form an enzyme called prothrombinase. (ii) The prothrombinase inactivates heparin or antiprothrombin- anticoagulant in the presence of calcium. Prothrombinase catalyses breakdown of prothrombin (inactive plasma protein) into an active protein called thrombin and some small peptide fragments. (iii) Thrombin acts as an enzyme and first brings about depolymerisation of fibrinogen (a soluble plasma protein) into its monomers. Later, thrombin stimulates repolymerisation of these monomers into long insoluble fibre-like polymers called fibrin. The thin, long and solid fibres of fibrin form a dense network upon the wound and trap blood corpuscles (RBCs, WBCs and platelets) to form a clot. The clot seals the wound and stops bleeding. Soon after the clot starts contracting and a pale yellow fluid, the serum, starts oozing out. This serum is blood plasma minus fibrinogen and blood corpuscles. Vitamin K is essential for blood clotting as it is necessary for the synthesis of prothrombin in the liver. The mechanism of blood clotting is explained by the given flow chart: (IMG 133)

Question. Draw a neatly labelled diagram of an artery and a vein.
Answer. The labelled diagram of an artery and a vein are as follows: 

Long Answer Type Questions

Question. Explain different types of blood groups and donor compatibility by making a table.
Answer. ABO blood groups in human beings were reported for first time by Karl Landsteiner. ABO blood groups are determined by the gene I (isoagglutinin). There are three alleles, IA, IB and IO of this gene. Proteins produced by the IA and IB alleles are called A antigen and B antigen respectively. (i) People with blood group A have the A antigen on the surface of their RBCs, and antibodies to antigen B in their plasma. (ii) Persons with blood group B have B antigen on their RBCs, and antibodies against A antigen in their plasma. (iii) Individuals with AB blood group have both antigen A and antigen B on their RBCs, and no antibodies for either of the antigens in their plasma. (iv) Type O individuals are without A and B antigens on their RBCs, but have antibodies for both antigens in their plasma. If a blood transfusion is made between an incompatible donor and recipient, reaction of antigens on the cells and antibodies in the plasma produces clots that clogs capillaries. Blood groups with donor compatibility is given in the table: 

Question. (a) What is blood pressure?
(b) How is it measured and what is it’s normal value?
Answer. (a) Blood pressure is defined as the pressure that the blood exerts on the walls of the blood vessels produced by the discharge of blood into them by contractions of the left ventricle.
(b) The blood pressure is measured from brachial artery by an instrument called sphygmomanometer in terms of height in millimeters of a column of mercury. When the left ventricle contracts pushing the blood into the aorta, the pressure produced is known as systolic blood pressure (120 mm Hg). When the complete diastole occurs and the heart is resting, the pressure within the blood vessels is called as the diastolic blood pressure (80 mm Hg). A sphygmomanometer consists of an inflatable cuff attached to a pressure gauge. The cuff is wrapped around the upper arm and rapidly inflated with a hand pump until no pulse is felt in the wrist. This shows that the blood supply to the forearm is stopped. A stethoscope is placed on the brachial artery just below the cuff, and the cuff is slowly deflated. The sound of blood flow is heard through the stethoscope. When thumping is heard, pressure on the gauge is noted. This sound is of the blood rushing through the arteries at peak pressure due to ventricular contraction. The reading on the gauge is the systolic blood pressure. The sound fades until it stops, the reading on the gauge now indicates the diastolic blood pressure. The systolic pressure shows the force with which the left ventricle pushes blood into the aortic arch. The diastolic pressure indicates the elasticity of the blood vessels, and is useful in diagnosing hardening of arteries or strain on their walls. The blood pressure is expressed as BP = 120/80 mm Hg.

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