Circulatory System — Set 4

Correct Answer: A. William Harvey

• **William Harvey** = English physician who first correctly described that blood circulates continuously, pumped by the heart, in his landmark work 'Exercitatio Anatomica de Motu Cordis' published in 1628. • **1628** — Harvey proved through experiments on live animals that arteries carry blood away from the heart and veins return it, overthrowing the ancient Galenic theory. • Harvey's discovery is considered one of the most important in the history of medicine, forming the foundation of modern cardiovascular science. • 💡 Option B (Louis Pasteur) is wrong because he discovered germ theory and pasteurization, not blood circulation; Option C (Edward Jenner) is wrong because he developed the smallpox vaccine; Option D (Andreas Vesalius) is wrong because he made contributions to human anatomy but did not explain circulation.

Correct Answer: D. Aorta

• **Aorta** = the largest and main artery of the body, originating from the left ventricle of the heart and distributing oxygenated blood to all organs and tissues through its branches. • **Diameter ~2.5 cm** — the aorta arches over the heart (aortic arch) and descends through the chest and abdomen, branching into the iliac arteries at the lower end. • It withstands the highest blood pressure in the body and its walls are thick with elastic tissue to absorb the force of each heartbeat. • 💡 Option A (Carotid artery) is wrong because it supplies blood to the head and neck, not the whole body; Option B (Femoral artery) is wrong because it is the major artery only of the thigh; Option C (Pulmonary artery) is wrong because it carries deoxygenated blood to the lungs, not oxygenated blood to the body.

Correct Answer: A. Platelet

• **Platelet** = also called thrombocyte (from Greek 'thrombos' meaning clot), these are small, colorless, anucleate cell fragments produced from megakaryocytes in the bone marrow that play a critical role in blood clotting. • **Normal count: 1.5–4 lakh per mm³** — when a blood vessel is injured, platelets aggregate at the site and release chemicals that initiate the clotting cascade, stopping blood loss. • A low platelet count (thrombocytopenia) causes excessive bleeding; a high count (thrombocytosis) can lead to dangerous clots. • 💡 Option B (Lymphocyte) is wrong because it is a white blood cell involved in immune responses, not clotting; Option C (WBC) is wrong because white blood cells fight infection and are not called thrombocytes; Option D (RBC) is wrong because red blood cells carry oxygen using hemoglobin and have no role in clotting.

Correct Answer: B. Hematology

• **Hematology** = the branch of medicine that studies blood, blood-forming organs (bone marrow, spleen, lymph nodes), and blood disorders, covering both diagnosis and treatment. • **Key diseases** — hematology deals with conditions such as anemia (low hemoglobin), leukemia (blood cancer), hemophilia (clotting deficiency), sickle cell disease, and thalassemia. • A doctor specializing in this field is called a hematologist, and common tests include CBC (Complete Blood Count) and bone marrow biopsy. • 💡 Option A (Neurology) is wrong because it is the study of the nervous system and its disorders; Option C (Dermatology) is wrong because it deals with skin diseases; Option D (Cardiology) is wrong because it is the study of the heart and cardiovascular diseases.

Correct Answer: D. Spleen

• **Spleen** = called the 'graveyard of RBCs' because it filters old, damaged, or abnormally shaped red blood cells (erythrocytes) from circulation and breaks them down after their ~120-day lifespan. • **Dual role** — the spleen also acts as a reservoir of blood (stores about 200 mL), produces lymphocytes for immunity, and recycles iron from destroyed hemoglobin back to the bone marrow. • The spleen is the largest lymphoid organ in the body; its removal (splenectomy) increases vulnerability to certain bacterial infections. • 💡 Option A (Pancreas) is wrong because it produces digestive enzymes and hormones like insulin; Option B (Liver) is wrong because it performs detoxification and bile production, though it does break down some hemoglobin products; Option C (Kidney) is wrong because it filters blood plasma to produce urine, not destroy RBCs.

Correct Answer: A. Iron

• **Iron (Fe²⁺)** = the ferrous iron atom sits at the center of the heme group in hemoglobin, and it is this iron that reversibly binds one oxygen molecule, allowing hemoglobin to carry oxygen from the lungs to tissues. • **4 iron atoms per hemoglobin** — each hemoglobin molecule has 4 heme groups, each containing one Fe²⁺, so one hemoglobin can carry 4 oxygen molecules simultaneously. • Iron deficiency leads to iron-deficiency anemia, the most common nutritional deficiency worldwide, causing pale skin, fatigue, and breathlessness. • 💡 Option B (Copper) is wrong because copper is found in hemocyanin (oxygen carrier in molluscs), not hemoglobin; Option C (Magnesium) is wrong because magnesium is the central atom of chlorophyll in plants, not hemoglobin; Option D (Zinc) is wrong because zinc is important for enzyme function but is not part of the heme group.

Correct Answer: D. Hypertension

• **Hypertension** = a chronic condition where the force of blood against artery walls is persistently elevated, defined as a reading consistently above 140/90 mmHg (systolic/diastolic). • **'Silent killer'** — hypertension typically has no symptoms but over time damages arteries, the heart, kidneys, and brain, leading to heart attack, stroke, and kidney failure. • Risk factors include obesity, high salt intake, smoking, stress, sedentary lifestyle, and family history; it affects over 1 billion people globally. • 💡 Option A (Hypotension) is wrong because it means abnormally low blood pressure (below 90/60 mmHg), the opposite condition; Option B (Anemia) is wrong because it refers to a deficiency of red blood cells or hemoglobin, unrelated to blood pressure; Option C (Ischemia) is wrong because it means insufficient blood supply to a tissue or organ due to blocked vessels.

Correct Answer: A. 5-6 liters

• **5–6 liters** = a healthy adult has approximately 5 to 6 liters of blood, which constitutes about 7–8% of total body weight, so a 70 kg person has roughly 5 liters of blood. • **Composition** — about 55% of blood is plasma (liquid), and the remaining 45% consists of formed elements: red blood cells (~4.5–5.5 million/mm³), white blood cells (~4,000–11,000/mm³), and platelets (~1.5–4 lakh/mm³). • Blood volume varies slightly with body size, sex, and fitness level; athletes tend to have slightly higher blood volume. • 💡 Option B (10–12 liters) is wrong because this is roughly double the actual volume and would be incompatible with normal anatomy; Option C (8–9 liters) is wrong because it significantly overestimates the normal blood volume; Option D (2–3 liters) is wrong because this would be dangerously low, equivalent to severe hemorrhage.

Correct Answer: A. Karl Landsteiner

• **Karl Landsteiner** = Austrian immunologist who discovered the ABO blood group system in 1901 by observing that mixing blood from different people sometimes caused clumping (agglutination), identifying the A, B, and O groups; he later co-discovered the Rh factor in 1940. • **Nobel Prize 1930** — Landsteiner was awarded the Nobel Prize in Physiology or Medicine for his discovery, which made safe blood transfusions possible and saved millions of lives. • AB blood group was identified by his colleagues Decastello and Sturli in 1902, completing the ABO system. • 💡 Option B (Charles Darwin) is wrong because he proposed the theory of evolution by natural selection; Option C (Gregor Mendel) is wrong because he established the laws of heredity through pea plant experiments; Option D (Robert Hooke) is wrong because he coined the term 'cell' after observing cork under a microscope.

Correct Answer: C. Sphygmomanometer

• **Sphygmomanometer** = the instrument used to measure blood pressure, consisting of an inflatable arm cuff connected to a pressure gauge (manometer); it records two values — systolic pressure (when heart contracts) and diastolic pressure (when heart relaxes), expressed as mmHg. • **Normal reading: 120/80 mmHg** — systolic 120 mmHg and diastolic 80 mmHg is considered optimal; it is used together with a stethoscope to hear Korotkoff sounds that indicate the pressure levels. • The digital sphygmomanometer is now widely used at home, but mercury-based ones were the traditional clinical standard. • 💡 Option A (Barometer) is wrong because it measures atmospheric (air) pressure, not blood pressure; Option B (Hydrometer) is wrong because it measures the specific gravity or density of liquids; Option D (Stethoscope) is wrong because it is used to listen to heart and lung sounds, not to measure pressure directly.