NEET Biology Body Fluids and Circulation MCQs Set 20

Answer: (a) 8000

Explanation:
1. A healthy adult has roughly 6000 to 8000 leucocytes per cubic mm of blood, so 8000 is the best match.

Teacher's Note:
1. Compare: RBCs are about 5 million and platelets 1.5 to 3.5 lakh per cubic mm.

Answer: (d) Frog

Explanation:
1. Mammalian RBCs lose the nucleus at maturity, while RBCs of frogs and other non-mammalian vertebrates keep it.

Teacher's Note:
1. Camel and llama RBCs are oval but still non-nucleated like other mammals.

Answer: (d) All of the above

Explanation:
1. Heparin acts with antithrombin, hirudin of leech saliva blocks thrombin, and EDTA binds calcium ions needed for clotting.

Teacher's Note:
1. Citrate and oxalate also act as anticoagulants by removing Ca2+ ions.

Answer: (a) Basophil

Explanation:
1. Basophils form only about 0.5 to 1 percent of the WBCs.

Teacher's Note:
1. Memory aid: Never Let Monkeys Eat Bananas, in decreasing order of abundance.

Answer: (a) 7.4

Explanation:
1. Blood is slightly alkaline, and buffers keep its pH near 7.35 to 7.45.

Teacher's Note:
1. A fall of pH below 7 or a rise above 7.8 is not compatible with life.

Answer: (c) Circular, biconcave and non-nucleated

Explanation:
1. Human erythrocytes are biconcave discs that have no nucleus, which gives more room for haemoglobin and a large surface area.

Teacher's Note:
1. Absence of mitochondria means they respire anaerobically.

Answer: (b) Haem

Explanation:
1. The haem part of haemoglobin from worn-out RBCs is broken down in the liver and spleen to the bile pigments.

Teacher's Note:
1. The globin is digested to amino acids and the iron is stored and reused.

Answer: (c) Fibrinogen

Explanation:
1. Thrombin converts soluble fibrinogen to insoluble fibrin threads that form the clot.

Teacher's Note:
1. Albumin maintains osmotic pressure and globulins carry antibodies.

Answer: (a) Plasma proteins

Explanation:
1. Globulins are plasma proteins, and the gamma globulins include the antibodies.

Teacher's Note:
1. Plasma proteins are fibrinogen, globulins and albumins.

Answer: (d) Platelets

Explanation:
1. Plasma is the fluid part left after cells are removed, so it has proteins like immunoglobulins and albumin but no platelets.

Teacher's Note:
1. Platelets are cell fragments and belong to the formed elements.

Answer: (c) Heparin

Explanation:
1. Heparin is an anticoagulant. Sodium glycocholate and taurocholate are bile salts and sodium hydroxide would damage the blood.

Teacher's Note:
1. Sodium citrate is the other common anticoagulant used for stored blood.

Answer: (c) Vitamin K

Explanation:
1. Vitamin K is needed by the liver to make prothrombin and other clotting factors.

Teacher's Note:
1. Vitamin K is partly made by intestinal bacteria.

Answer: (b) Polycythemia

Explanation:
1. Polycythemia means too many red cells, as at high altitude or in a bone marrow disorder.

Teacher's Note:
1. Leukaemia is excess of WBCs and anaemia is a shortage of haemoglobin or RBCs.

Answer: (a) Serum

Explanation:
1. Serum is plasma without fibrinogen and other clotting factors, which are used up in the clot.

Teacher's Note:
1. Plasma still has the clotting proteins, serum does not.

Answer: (a) Thromboplastin

Explanation:
1. Thromboplastin (thrombokinase) starts the cascade that converts prothrombin to thrombin, which then forms fibrin from fibrinogen.

Teacher's Note:
1. Heparin prevents clotting, whereas fibrinogen and prothrombin are inactive precursors.

Answer: (a) Right auricle

Explanation:
1. In fishes and amphibians the sinus venosus is a separate chamber, but in mammals it is reduced and forms part of the right atrium that carries the SA node.

Teacher's Note:
1. This is why the pacemaker lies in the right atrial wall.

Answer: (b) Tadpole or fish

Explanation:
1. In a closed system the blood stays inside vessels, as in all vertebrates and annelids. Insects have an open system.

Teacher's Note:
1. Open system: the haemocoel is filled with haemolymph that bathes the organs.

Answer: (b) The left auricle and left ventricle in higher vertebrates

Explanation:
1. The left half of the heart receives oxygenated blood and pumps it to the body, so it is called the systemic heart, while the right half is the pulmonary heart.

Teacher's Note:
1. In fishes the heart receives only deoxygenated blood and is called a branchial heart.

Answer: (b) The right auricle near the opening of the superior vena cava

Explanation:
1. The sino-atrial node lies in the upper right wall of the right atrium close to the opening of the superior vena cava.

Teacher's Note:
1. The SAN generates about 70 to 75 impulses a minute.

Answer: (c) The ventricles of the heart

Explanation:
1. Papillary muscles project from the ventricular walls and hold the chordae tendineae that anchor the AV valves.

Teacher's Note:
1. They keep the valve flaps from turning back into the atria during ventricular systole.

Answer: (c) Ligamentum arteriosum

Explanation:
1. After birth the ductus arteriosus closes and its remnant is a fibrous cord called the ligamentum arteriosum.

Teacher's Note:
1. Fossa ovalis is the remnant of the foramen ovale between the atria.

Answer: (d) Lungs

Explanation:
1. Blood returns to the left atrium from the lungs through the pulmonary veins.

Teacher's Note:
1. This is the pulmonary circuit: right ventricle, lungs, left atrium.

Answer: (b) Quick contraction without fatigue

Explanation:
1. Cardiac muscle contracts rapidly and rhythmically through life without fatigue, as it has many mitochondria and a rich blood supply.

Teacher's Note:
1. Its long refractory period prevents tetanus.

Answer: (d) Right auricle of the heart

Explanation:
1. The valve of the inferior vena cava, called the Eustachian valve, guards the opening of the IVC into the right atrium in the foetus and is a rudiment in the adult.

Teacher's Note:
1. Do not confuse it with the Eustachian tube of the ear.

Answer: (c) Left auricle and left ventricle

Explanation:
1. The bicuspid (mitral) valve guards the opening between the left atrium and left ventricle.

Teacher's Note:
1. The tricuspid valve is on the right side.