NEET Biology: Human Physiology · Chapter 2

Body Fluids and Circulation

What to remember

Blood is a fluid connective tissue: plasma (about 55%) plus formed elements (RBCs, WBCs, platelets). Plasma proteins are fibrinogen (clotting), globulins (defence) and albumins (osmotic balance). Plasma without clotting factors is serum.
ABO blood groups depend on antigens on the RBCs and antibodies in the plasma: group O has no antigen and is the universal donor; group AB has no antibody and is the universal recipient. Rh incompatibility between an Rh-negative mother and an Rh-positive foetus causes erythroblastosis foetalis.
The human heart is four-chambered and the circulation is double: the SAN is the pacemaker; a cardiac cycle lasts about 0.8 s; cardiac output is about 5 L per minute (stroke volume about 70 mL × heart rate about 72 per minute). In the ECG, the P wave is atrial depolarisation, the QRS complex is ventricular depolarisation and the T wave is ventricular repolarisation.
Normal blood pressure is 120/80 mm Hg; 140/90 mm Hg or above is hypertension. Cardiac arrest (heart stops beating) is different from a heart attack (heart muscle damaged by poor blood supply).

Blood

Blood is a special connective tissue consisting of a fluid matrix, plasma, and formed elements.

Plasma is a straw-coloured, viscous fluid and constitutes about 55% of the blood.

About 90–92% of plasma is water and 6–8% is proteins.
The main proteins are fibrinogen, globulins and albumins. Fibrinogen is needed for clotting or coagulation of blood. Globulins are primarily involved in the defence mechanism of the body. Albumins help in osmotic balance.
Plasma also contains small amounts of glucose, amino acids, lipids and minerals such as Na⁺, Ca²⁺, Mg²⁺, HCO₃⁻ and Cl⁻.
Factors for coagulation or clotting are present in plasma in an inactive form. Plasma without the clotting factors is called serum.

Formed elements constitute about 45% of the blood.

Formed element	Standard count	Key features and functions
Erythrocytes (RBCs)	About 5 to 5.5 million per mm³ of blood	Formed in the red bone marrow; no nucleus in most mammals; contain haemoglobin (about 12–16 g per 100 mL of blood); carry O₂; life span about 120 days; destroyed mainly in the spleen
Leucocytes (WBCs)	About 6000–8000 per mm³ of blood	Colourless, nucleated, fewer in number; defence
Platelets (thrombocytes)	About 150,000 to 350,000 per mm³ (1.5 to 3.5 lakh)	Cell fragments from megakaryocytes of bone marrow; release substances for clotting; a reduction can cause clotting disorders and blood loss

Types of WBCs. Leucocytes are of two main groups: granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).

WBC type	Share of total WBCs	Function
Neutrophils	About 60–65% (the most abundant)	Phagocytic cells
Lymphocytes	About 20–25%	B and T forms; responsible for immune responses
Monocytes	About 6–8%	Phagocytic cells
Eosinophils	About 2–3%	Resist infections; associated with allergic reactions
Basophils	About 0.5–1% (the least abundant)	Secrete histamine, serotonin and heparin; involved in inflammatory reactions

Blood groups

ABO grouping. It is based on the presence or absence of two surface antigens, A and B, on the RBCs. The plasma has natural antibodies against the antigen that is absent.

Blood group	Antigen on RBCs	Antibodies in plasma	Can donate to	Can receive from
A	A	Anti-B	A, AB	A, O
B	B	Anti-A	B, AB	B, O
AB	A and B	None	AB only	A, B, AB, O
O	None	Anti-A and anti-B	A, B, AB, O	O only

Group O is the universal donor. Group AB is the universal recipient.
A donor's blood must be matched with the recipient's before transfusion, to avoid clumping (agglutination) of the RBCs that can be fatal.

Rh grouping. Another antigen, the Rh antigen, is present on the surface of RBCs of about 80% of humans. Such persons are Rh positive (Rh⁺). Those lacking it are Rh negative (Rh⁻). An Rh⁻ person should not be given Rh⁺ blood, because antibodies against the Rh factor will form.

Erythroblastosis foetalis. It occurs when an Rh⁻ mother carries an Rh⁺ foetus.

During the first pregnancy, the maternal and foetal blood are kept separate by the placenta, so the first child is normally unaffected.
At the time of the delivery, some foetal blood can mix with the mother's blood. The mother then forms anti-Rh antibodies in her blood.
In a later pregnancy with an Rh⁺ foetus, these antibodies can leak into the foetal blood and destroy the foetal RBCs. This can cause severe anaemia and jaundice in the baby, and can be fatal.
It can be avoided by giving the mother anti-Rh antibodies immediately after the delivery of the first child.

Coagulation of blood

Blood clotting prevents loss of blood after an injury. A clot (coagulum) is formed mainly of a network of fibrin threads in which dead and damaged formed elements are trapped.

Outline of the cascade:

1. An injury or trauma stimulates the platelets in the blood to release certain factors that activate the mechanism of coagulation.
2. A complex enzyme called thrombokinase (also called thromboplastin) is formed through a cascade of linked reactions involving a number of factors present in the plasma in inactive form.
3. Thrombokinase converts inactive prothrombin of the plasma into active thrombin, with the help of Ca²⁺ ions.
4. Thrombin converts fibrinogen of the plasma into fibrin, which forms a network of fine threads.
5. The fibrin threads trap blood cells, and a clot forms.

Lymph (tissue fluid)

As blood passes through the capillaries in the tissues, some water along with small water-soluble substances moves out into the spaces between the cells. This fluid is called interstitial fluid or tissue fluid. It has the same mineral distribution as plasma.
An elaborate network of vessels called the lymphatic system collects this fluid and drains it back to the major veins. The fluid present in the lymphatic system is the lymph.
Lymph is a colourless fluid containing specialised lymphocytes, which are responsible for the immune responses of the body. It is also an important carrier of nutrients, hormones and other substances.
Fats are absorbed through lymph in the lacteals present in the intestinal villi.

Circulatory pathways

Open and closed systems. In an open circulatory system (found in arthropods and molluscs), blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses. In a closed circulatory system (found in annelids and chordates), the blood pumped by the heart is always circulated through a closed network of blood vessels.

Heart in vertebrates.

Group	Heart chambers	Circulation
Fishes	Two chambers: one atrium and one ventricle; the heart pumps deoxygenated blood to the gills	Single circulation
Amphibians	Three chambers: two atria and one ventricle	Incomplete double circulation (mixing of blood)
Reptiles (except crocodiles)	Three chambers: two atria and one incompletely divided ventricle	Incomplete double circulation
Crocodiles, birds, mammals	Four chambers: two atria and two ventricles	Complete double circulation (oxygenated and deoxygenated blood do not mix)

Human circulatory system

Structure of the heart. The heart is mesodermally derived. It is situated in the thoracic cavity, between the two lungs, slightly tilted to the left. It is about the size of a clenched fist. It is protected by a double-walled membrane, the pericardium, enclosing the pericardial fluid.

The heart has four chambers: two relatively small upper chambers called atria and two larger lower chambers called ventricles.
A thin muscular wall, the interatrial septum, separates the right and left atria. A thick-walled interventricular septum separates the ventricles.
The atrium and the ventricle of the same side are separated by the atrio-ventricular septum. Each opening in this septum is guarded by a valve: the tricuspid valve (three flaps) on the right and the bicuspid or mitral valve (two flaps) on the left.
The openings of the right ventricle into the pulmonary artery and of the left ventricle into the aorta are guarded by semilunar valves. The valves allow the flow of blood in only one direction.
The walls of the ventricles are much thicker than those of the atria.

Nodal tissue. A special cardiac muscle tissue, the nodal tissue, is distributed in the heart.

Part	Location	Function
Sino-atrial node (SAN)	Upper right corner of the right atrium	Pacemaker; generates the highest number of action potentials, about 70–75 per minute
Atrio-ventricular node (AVN)	Lower left corner of the right atrium, close to the atrio-ventricular septum	Receives the impulse from the SAN and passes it on
Atrio-ventricular bundle (bundle of His)	Passes from the AVN through the atrio-ventricular septum	Divides into right and left bundles along the interventricular septum
Purkinje fibres	Minute fibres from the bundles spread in the ventricular walls	Carry the impulse to the ventricular muscle

Blood vessels. Arteries carry blood away from the heart and have thick, elastic walls. Veins carry blood towards the heart and have thinner walls and valves. Capillaries are the smallest vessels; their walls have a single layer of endothelial cells, and exchange occurs through them.

Cardiac cycle

The sequential events in the heart that are cyclically repeated are called the cardiac cycle.

A normal heart beats about 72 times per minute. One cycle therefore lasts about 0.8 second.
The events are: atrial systole (about 0.1 s), ventricular systole (about 0.3 s) and joint diastole (about 0.4 s).
During joint diastole, the blood from the pulmonary veins and vena cava flows into the atria and then to the ventricles through the open atrio-ventricular valves. The atrial systole then forces the remaining blood into the ventricles.
Ventricular systole closes the atrio-ventricular valves, and the semilunar valves open, so the blood enters the pulmonary artery and the aorta.
The volume of blood pumped by each ventricle per beat is the stroke volume, about 70 mL.
Cardiac output = stroke volume × heart rate = about 70 mL × 72 per minute, which is about 5000 mL (5 litres) per minute.

Heart sounds. Two sounds are heard with a stethoscope. The first sound, "lub", is associated with the closure of the tricuspid and bicuspid valves at the start of ventricular systole. The second sound, "dub", is associated with the closure of the semilunar valves at the end of ventricular systole.

Electrocardiograph (ECG)

The ECG is a graphical record of the electrical activity of the heart during a cardiac cycle. The patient is connected to the machine with three electrical leads (one to each wrist and one to the left ankle) and continuous monitoring is possible.

Wave	Represents
P wave	Electrical excitation (depolarisation) of the atria, leading to atrial contraction
QRS complex	Depolarisation of the ventricles, which starts ventricular contraction
T wave	Repolarisation of the ventricles; return of the ventricles from the excited to the normal state

The end of the T wave marks the end of ventricular systole. Counting the number of QRS complexes in a given time period gives the heart beat rate.

Double circulation

Blood flows through the heart twice in one complete circuit.

Pulmonary circulation: right ventricle → pulmonary artery → lungs → pulmonary veins → left atrium.
Systemic circulation: left ventricle → aorta → arteries → tissues → veins → vena cava → right atrium.
Hepatic portal system: a special vein, the hepatic portal vein, carries blood from the intestine to the liver before it goes to the heart. The path is: digestive tract → hepatic portal vein → liver → hepatic vein → vena cava.
Coronary circulation: the heart muscle has its own blood supply. Aorta → coronary arteries → cardiac muscle → coronary veins → coronary sinus → right atrium.

Regulation of cardiac activity

Normal activity of the heart is regulated intrinsically, that is, it is auto-regulated by nodal tissue (hence the heart is myogenic). The activity can also be modified by neural and hormonal mechanisms.

Neural regulation: a special neural centre in the medulla oblongata moderates the cardiac function through the autonomic nervous system. Sympathetic nerves increase the rate of heart beat, the strength of ventricular contraction and the cardiac output. Parasympathetic nerves (the vagus) decrease the rate of heart beat, the speed of conduction of the action potential and the cardiac output.
Hormonal regulation: adrenal medullary hormones (adrenaline and noradrenaline) increase the cardiac output.

Disorders of the circulatory system

Hypertension (high blood pressure): blood pressure higher than normal. Normal blood pressure is 120 mm Hg (systolic) over 80 mm Hg (diastolic). A reading of 140/90 or higher indicates hypertension.
Coronary artery disease (CAD), atherosclerosis: it affects the vessels that supply blood to the heart muscle. It is caused by deposits of calcium, fat, cholesterol and fibrous tissue, which make the lumen of the arteries narrower.
Angina (angina pectoris): a symptom of acute chest pain that appears when not enough oxygen is reaching the heart muscle. It is more common in middle-aged and elderly people and occurs due to conditions that affect the blood flow.
Heart failure: the state of the heart when it is not pumping blood effectively enough to meet the needs of the body. It is sometimes called congestive heart failure because congestion of the lungs is one of the main symptoms.
Cardiac arrest and heart attack: cardiac arrest is when the heart stops beating. A heart attack is when the heart muscle is suddenly damaged by an inadequate blood supply.

NEET traps

Plasma contains clotting factors; serum does not. Do not interchange them.
Group O has no antigens but both antibodies (universal donor). Group AB has both antigens but no antibodies (universal recipient).
The first Rh⁺ child of an Rh⁻ mother is usually unaffected; the risk arises in a later pregnancy.
Neutrophils are the most abundant WBCs; basophils are the least abundant. Basophils secrete histamine, serotonin and heparin; eosinophils are linked to allergy.
Thrombokinase converts prothrombin to thrombin; thrombin (not thrombokinase) converts fibrinogen to fibrin. Ca²⁺ is needed.
The SAN is in the right atrium (upper right corner); the AVN is in the lower left corner of the right atrium. Both are in the right atrium.
The tricuspid valve is on the right side; the bicuspid (mitral) valve is on the left side.
"Lub" is closure of the atrio-ventricular valves; "dub" is closure of the semilunar valves.
In the ECG, the T wave is repolarisation of the ventricles, not of the atria. The P wave is atrial depolarisation.
Cardiac arrest is not the same as a heart attack. Sympathetic nerves increase heart rate; parasympathetic (vagus) nerves decrease it.

One-liners

Plasma is about 55% of blood; about 90–92% of plasma is water.
Fibrinogen helps in clotting, globulins in defence, albumins in osmotic balance.
RBC count is about 5–5.5 million per mm³; WBC count about 6000–8000 per mm³.
Platelet count is about 1.5 to 3.5 lakh per mm³.
RBCs live about 120 days and are mainly destroyed in the spleen.
Neutrophils are about 60–65% of WBCs; lymphocytes about 20–25%.
Group O is the universal donor; group AB is the universal recipient.
Anti-Rh antibody is given to an Rh⁻ mother after the delivery of an Rh⁺ child.
Prothrombin is changed to thrombin by thrombokinase and Ca²⁺.
Fishes have a two-chambered heart; amphibians and most reptiles have a three-chambered heart.
Crocodiles, birds and mammals have a four-chambered heart.
The SAN is the pacemaker, generating about 70–75 action potentials per minute.
One cardiac cycle lasts about 0.8 s; stroke volume is about 70 mL and cardiac output about 5 L per minute.
The QRS complex represents ventricular depolarisation.
Normal blood pressure is 120/80 mm Hg.

Practice questions

Which plasma protein is primarily involved in the defence mechanism of the body?
1. Albumin
2. Globulin
3. Prothrombin
4. Fibrinogen
Answer
B. Globulin
Globulins are primarily involved in defence; fibrinogen is for clotting and albumins for osmotic balance.
Which type of leucocyte is the most abundant in human blood?
1. Monocyte
2. Basophil
3. Lymphocyte
4. Neutrophil
Answer
D. Neutrophil
Neutrophils form about 60–65% of the WBCs.
Platelets are cell fragments produced from
1. Megakaryocytes
2. Lymphocytes
3. Erythroblasts
4. Monocytes
Answer
A. Megakaryocytes
Platelets are formed from megakaryocytes of the bone marrow.
Which blood group is called the universal recipient?
1. O
2. A
3. AB
4. B
Answer
C. AB
Group AB has no anti-A or anti-B antibodies, so it can receive from all ABO groups.
The heart of an amphibian has
1. Five chambers
2. Two chambers
3. Four chambers
4. Three chambers
Answer
D. Three chambers
Amphibians have two atria and one ventricle.
The pacemaker of the human heart is the
1. Sino-atrial node
2. Bundle of His
3. Purkinje fibres
4. Atrio-ventricular node
Answer
A. Sino-atrial node
The SAN generates the highest number of action potentials and sets the rhythm.
The valve between the left atrium and the left ventricle is the
1. Tricuspid valve
2. Semilunar valve of the pulmonary artery
3. Bicuspid valve
4. Semilunar valve of the aorta
Answer
C. Bicuspid valve
The left atrio-ventricular opening is guarded by the bicuspid (mitral) valve.
The approximate cardiac output of a healthy adult at rest is
1. 70 mL per minute
2. 5000 mL per minute
3. 3500 mL per minute
4. 7000 mL per minute
Answer
B. 5000 mL per minute
Cardiac output = about 70 mL × 72 beats per minute, i.e., about 5000 mL per minute.
The second heart sound, 'dub', is produced by
1. Opening of the atrio-ventricular valves
2. Closure of the semilunar valves
3. Closure of the atrio-ventricular valves
4. Contraction of the atria
Answer
B. Closure of the semilunar valves
The 'dub' sound is associated with closure of the semilunar valves.
In an ECG, the T wave represents
1. Repolarisation of the atria
2. Depolarisation of the atria
3. Repolarisation of the ventricles
4. Depolarisation of the ventricles
Answer
C. Repolarisation of the ventricles
The T wave is the return of the ventricles from the excited to the normal state.
Normal blood pressure in a healthy adult is
1. 100/60 mm Hg
2. 140/90 mm Hg
3. 160/100 mm Hg
4. 120/80 mm Hg
Answer
D. 120/80 mm Hg
Normal blood pressure is 120 mm Hg systolic over 80 mm Hg diastolic.
In one cardiac cycle of about 0.8 s, the duration of the joint diastole is about
1. 0.4 s
2. 0.1 s
3. 0.3 s
4. 0.8 s
Answer
A. 0.4 s
Atrial systole 0.1 s + ventricular systole 0.3 s + joint diastole 0.4 s = 0.8 s.
Which enzyme complex converts inactive prothrombin into thrombin in the presence of Ca²⁺?
1. Heparin
2. Haemoglobin
3. Fibrin
4. Thrombokinase
Answer
D. Thrombokinase
Thrombokinase, formed through the cascade, converts prothrombin to thrombin.
Worn-out RBCs, which live for about 120 days, are mainly destroyed in the
1. Pancreas
2. Kidney
3. Spleen
4. Bone marrow
Answer
C. Spleen
The spleen is the main site of RBC destruction.
The plasma of a person with blood group O contains
1. Only anti-A antibodies
2. Only anti-B antibodies
3. No antibodies
4. Both anti-A and anti-B antibodies
Answer
D. Both anti-A and anti-B antibodies
Group O has no antigens on the RBCs but both antibodies in the plasma.
The vessel that carries blood from the intestine to the liver is the
1. Pulmonary vein
2. Hepatic portal vein
3. Coronary sinus
4. Hepatic vein
Answer
B. Hepatic portal vein
The hepatic portal vein carries blood from the digestive tract to the liver.
Given below are two statements: Statement I: Plasma without the clotting factors is called serum. Statement II: Albumins help in the osmotic balance of blood. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
A. Both Statement I and Statement II are correct
Both statements are correct.
Given below are two statements: Statement I: The Rh antigen is present on the RBCs of about 80% of humans. Statement II: The first child of an Rh-negative mother and an Rh-positive father is usually severely affected. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
Statement I is correct. The placenta separates the blood, so the first child is normally unaffected; Statement II is incorrect.
Given below are two statements: Statement I: Eosinophils secrete histamine, serotonin and heparin. Statement II: Monocytes are phagocytic cells. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
Basophils secrete histamine, serotonin and heparin, so Statement I is incorrect. Monocytes are phagocytic.
Which of the following statements are correct? 1. The AVN lies in the lower left corner of the right atrium. 2. Purkinje fibres spread in the walls of the ventricles. 3. The SAN lies in the left atrium.
1. 1 and 3 only
2. 2 and 3 only
3. 1 and 2 only
4. 1, 2 and 3
Answer
C. 1 and 2 only
The SAN lies in the upper right corner of the right atrium, so 3 is wrong.
Given below are two statements: Statement I: The hepatic portal vein carries blood from the liver to the intestine. Statement II: The coronary sinus opens into the right atrium. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
The hepatic portal vein carries blood from the intestine to the liver, so Statement I is incorrect. Statement II is correct.
Given below are two statements: Statement I: The heart of fishes has three chambers. Statement II: The heart of crocodiles has three chambers. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
B. Both Statement I and Statement II are incorrect
Fishes have a two-chambered heart; crocodiles have a four-chambered heart. Both statements are incorrect.
Which of the following statements are correct? 1. Thrombin converts fibrinogen into fibrin. 2. Thrombokinase converts fibrin into thrombin. 3. Platelets release factors that start coagulation after an injury.
1. 1 and 2 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3
Answer
C. 1 and 3 only
Thrombokinase converts prothrombin to thrombin, not fibrin to thrombin, so 2 is wrong.
Given below are two statements: Statement I: The QRS complex of the ECG represents depolarisation of the ventricles. Statement II: Counting the QRS complexes in a given time gives the heart beat rate. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
A. Both Statement I and Statement II are correct
Both statements are correct.
Which of the following statements are correct? 1. A blood pressure of 140/90 mm Hg or higher indicates hypertension. 2. In coronary artery disease, deposits narrow the lumen of the arteries supplying the heart. 3. Cardiac arrest means that the heart muscle is damaged by an inadequate blood supply.
1. 1 and 2 only
2. 1 and 3 only
3. 2 and 3 only
4. 1, 2 and 3
Answer
A. 1 and 2 only
Damage of heart muscle by poor blood supply is a heart attack; cardiac arrest is when the heart stops beating.
Given below are two statements: Statement I: Globulins are involved in the clotting of blood. Statement II: Fibrinogen is involved in the defence mechanism of the body. Choose the correct option.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
B. Both Statement I and Statement II are incorrect
Fibrinogen is for clotting and globulins for defence, so both statements are incorrect.
Assertion (A): Blood group O is the universal donor. Reason (R): The RBCs of group O carry neither antigen A nor antigen B. Choose the correct option.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
Without A or B antigens the RBCs do not clump in recipients of other groups.
Assertion (A): Plasma contains the protein fibrinogen. Reason (R): Platelets are cell fragments formed from megakaryocytes. Choose the correct option.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
B. Both A and R are true but R is not the correct explanation of A
Both are true, but the reason does not explain the presence of fibrinogen in plasma.
Assertion (A): Sympathetic nerves increase the cardiac output. Reason (R): Sympathetic nerves decrease the strength of ventricular contraction. Choose the correct option.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
C. A is true but R is false
Sympathetic nerves increase the rate and the strength of contraction, so R is false.
Assertion (A): The bicuspid valve is present on the right side of the heart. Reason (R): The tricuspid valve guards the right atrio-ventricular opening. Choose the correct option.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
D. A is false but R is true
The bicuspid valve is on the left side, so A is false. R is true.
Assertion (A): The first child of an Rh-negative mother and an Rh-positive father is usually normal. Reason (R): The placenta keeps the maternal and foetal blood separate during pregnancy. Choose the correct option.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
Anti-Rh antibodies form only after the mixing of blood at delivery, so the first child is generally not affected.
Assertion (A): Group AB is the universal recipient. Reason (R): The plasma of group AB contains both anti-A and anti-B antibodies. Choose the correct option.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
C. A is true but R is false
AB plasma has no antibodies, so R is false.
Match List I with List II. List I: a. Neutrophils b. Lymphocytes c. Monocytes d. Basophils. List II: i. About 60–65% ii. About 20–25% iii. About 6–8% iv. About 0.5–1%.
1. a-i, b-ii, c-iv, d-iii
2. a-i, b-ii, c-iii, d-iv
3. a-iii, b-ii, c-i, d-iv
4. a-ii, b-i, c-iii, d-iv
Answer
B. a-i, b-ii, c-iii, d-iv
Neutrophils 60–65%, lymphocytes 20–25%, monocytes 6–8%, basophils 0.5–1%.
Match List I with List II. List I: a. Blood group A b. Blood group B c. Blood group AB d. Blood group O. List II: i. Anti-A antibody ii. Anti-B antibody iii. No antibody iv. Anti-A and anti-B antibodies.
1. a-iii, b-i, c-ii, d-iv
2. a-ii, b-i, c-iii, d-iv
3. a-i, b-ii, c-iii, d-iv
4. a-ii, b-i, c-iv, d-iii
Answer
B. a-ii, b-i, c-iii, d-iv
Group A has anti-B, group B has anti-A, AB has none, O has both.
Match List I with List II. List I: a. SAN b. AVN c. Bundle of His d. Purkinje fibres. List II: i. Upper right corner of the right atrium ii. Lower left corner of the right atrium iii. Passes through the atrio-ventricular septum iv. Spread in the walls of the ventricles.
1. a-i, b-ii, c-iii, d-iv
2. a-ii, b-i, c-iii, d-iv
3. a-i, b-ii, c-iv, d-iii
4. a-iii, b-ii, c-i, d-iv
Answer
A. a-i, b-ii, c-iii, d-iv
SAN: upper right of right atrium; AVN: lower left of right atrium; bundle of His through the septum; Purkinje fibres in the ventricles.
Match List I with List II. List I: a. P wave b. QRS complex c. T wave d. End of the T wave. List II: i. Atrial depolarisation ii. Ventricular depolarisation iii. Ventricular repolarisation iv. End of ventricular systole.
1. a-i, b-ii, c-iv, d-iii
2. a-ii, b-i, c-iii, d-iv
3. a-iii, b-ii, c-i, d-iv
4. a-i, b-ii, c-iii, d-iv
Answer
D. a-i, b-ii, c-iii, d-iv
P: atrial depolarisation; QRS: ventricular depolarisation; T: ventricular repolarisation; end of T: end of ventricular systole.
Match List I with List II. List I: a. Fishes b. Amphibians c. Crocodiles d. Arthropods. List II: i. Two-chambered heart ii. Three-chambered heart iii. Four-chambered heart iv. Open circulatory system.
1. a-i, b-iii, c-ii, d-iv
2. a-i, b-ii, c-iii, d-iv
3. a-ii, b-i, c-iii, d-iv
4. a-i, b-ii, c-iv, d-iii
Answer
B. a-i, b-ii, c-iii, d-iv
Fishes have two chambers, amphibians three, crocodiles four, and arthropods have an open system.
Match List I with List II. List I: a. Hypertension b. Coronary artery disease c. Angina d. Heart failure. List II: i. Blood pressure of 140/90 mm Hg or higher ii. Deposits narrowing the arteries of the heart muscle iii. Chest pain when too little O₂ reaches the heart muscle iv. Heart not pumping blood enough for the body's needs.
1. a-ii, b-i, c-iii, d-iv
2. a-i, b-ii, c-iv, d-iii
3. a-i, b-iii, c-ii, d-iv
4. a-i, b-ii, c-iii, d-iv
Answer
D. a-i, b-ii, c-iii, d-iv
Each disorder is matched with its description.
A person's stroke volume is 70 mL and heart rate is 80 beats per minute. What is the cardiac output?
1. 560 mL per minute
2. 7000 mL per minute
3. 5600 mL per minute
4. 5000 mL per minute
Answer
C. 5600 mL per minute
Cardiac output = 70 mL × 80 = 5600 mL per minute.
An Rh-negative woman delivered an Rh-positive baby, and in a later pregnancy the Rh-positive foetus develops severe anaemia. What is the most likely reason?
1. Anti-Rh antibodies formed in the mother after the first delivery crossed into the foetal blood and destroyed foetal RBCs
2. The mother's RBCs have the Rh antigen
3. The foetus formed antibodies against the mother's RBCs from the first pregnancy
4. Anti-Rh antibodies were given to the mother after the first delivery
Answer
A. Anti-Rh antibodies formed in the mother after the first delivery crossed into the foetal blood and destroyed foetal RBCs
This is erythroblastosis foetalis; maternal anti-Rh antibodies destroy foetal RBCs.
If one cardiac cycle lasts 0.8 second, how many beats per minute does the heart make?
1. 72
2. 75
3. 60
4. 80
Answer
B. 75
60 s ÷ 0.8 s = 75 beats per minute (about 72 as the standard value).
A man gets chest pain on exertion because not enough O₂ reaches his heart muscle, but his heart keeps beating normally. Which condition does he have?
1. Hypertension
2. Cardiac arrest
3. Angina
4. Heart failure
Answer
C. Angina
Chest pain from too little O₂ reaching the heart muscle is angina.
An ECG record shows 12 QRS complexes in 10 seconds. What is the heart beat rate?
1. 72 per minute
2. 120 per minute
3. 84 per minute
4. 60 per minute
Answer
A. 72 per minute
12 QRS complexes in 10 s = 72 per minute.
A person's blood has neither anti-A nor anti-B antibodies in the plasma. What is the ABO blood group?
1. B
2. A
3. O
4. AB
Answer
D. AB
Absence of both antibodies is typical of group AB.
A patient with blood group A needs an emergency transfusion. Which donor groups are suitable?
1. AB and O
2. B and O
3. A and AB
4. A and O
Answer
D. A and O
Group A can receive from groups A and O, since neither has the B antigen.

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