Blood and Immunity Practice Questions

Q: In which stage of erythropoiesis does hemoglobin first appear?

Basophil erythroblast. **Explanation:** The correct answer is **Basophil erythroblast** (also known as the Early Normoblast). **1. Why Basophil Erythroblast is correct:** During erythropoiesis, the synthesis of hemoglobin begins early in the lineage. While the genetic machinery for hemoglobin production is activated in the proerythroblast stage, the **first visible appearance** of hemoglobin (at the microscopic/biochemical level) occurs in the **Basophil erythroblast**. Although the cell appears intensely blue (basophilic) due to an abundance of RNA and ribosomes, small amounts of hemoglobin are being actively synthesized within the cytoplasm. **2. Analysis of Incorrect Options:** * **Proerythroblast:** This is the first committed precursor. It contains no hemoglobin yet; it is characterized by a large nucleus and nucleoli, focusing on cellular division and organelle synthesis. * **Polychromatophil erythroblast:** In this stage, hemoglobin levels increase significantly. The "polychromatic" appearance (pinkish-grey) is due to the mixture of pink hemoglobin and blue ribosomal RNA. It is the stage where hemoglobin becomes **prominent**, but not where it first appears. * **Orthochromatic erythroblast:** Also known as the Late Normoblast. Here, the cytoplasm is increasingly eosinophilic (pink) because it is saturated with hemoglobin, and the nucleus becomes pyknotic before extrusion. **3. NEET-PG High-Yield Pearls:** * **First appearance of Hb:** Basophil erythroblast. * **Hemoglobin becomes visible/prominent:** Polychromatophil erythroblast. * **Nucleus is extruded at:** Orthochromatic erythroblast stage (to form a Reticulocyte). * **Reticulocyte:** Contains remnants of the Golgi apparatus and mitochondria (detected by supra-vital stains like New Methylene Blue). * **Total duration of Erythropoiesis:** Approximately 7 days (5 days to reticulocyte + 2 days to mature RBC).

Q: Which of the following changes occurs in RBCs of stored blood?

Increase in Na+ and decrease in K+ content. **Explanation:** The correct answer is **C: Increase in Na+ and decrease in K+ content.** **Underlying Concept:** In living red blood cells (RBCs), the **Na⁺-K⁺ ATPase pump** actively maintains high intracellular potassium (K⁺) and low intracellular sodium (Na⁺) levels against their respective concentration gradients. This process is energy-dependent, requiring ATP. When blood is stored (typically at 1–6°C), the metabolic rate of RBCs slows down significantly, leading to a depletion of ATP. Without ATP, the Na⁺-K⁺ ATPase pump fails. Consequently, Na⁺ leaks into the cell and K⁺ leaks out of the cell along their concentration gradients. This results in an **increase in intracellular Na⁺** and a **decrease in intracellular K⁺**. **Analysis of Incorrect Options:** * **Option A & B:** These are incorrect because Na⁺ and K⁺ move in opposite directions due to the failure of the active transport mechanism. * **Option D:** This is incorrect because Na⁺-K⁺ ATPase activity **decreases** (it does not increase) due to low temperatures and the lack of available ATP in stored blood. **NEET-PG High-Yield Pearls:** * **Hyperkalemia Risk:** The leakage of K⁺ out of the RBCs leads to high potassium levels in the plasma of stored blood. This is why massive blood transfusions can lead to **transfusion-associated hyperkalemia**, a critical concern in pediatric and renal patients. * **Storage Lesion:** Other changes in stored blood include a **decrease in 2,3-BPG** (shifting the oxygen dissociation curve to the left, increasing O₂ affinity), a **decrease in pH** (acidosis), and a **decrease in ATP**. * **Spherocytosis:** As Na⁺ enters the cell, water follows osmotically, causing the RBCs to swell and become more spherical (increasing osmotic fragility).

Q: Which of the following findings would best explain a prolonged bleeding time test?

Thrombocytopenia. **Explanation:** The **Bleeding Time (BT)** is a clinical test that measures the time taken for a standardized skin wound to stop bleeding. It specifically assesses the **primary hemostatic plug formation**, which is entirely dependent on two factors: **platelet function** and **platelet count**. **1. Why Thrombocytopenia is correct:** Thrombocytopenia (low platelet count) directly impairs the formation of the initial platelet plug. Since the primary response to vascular injury relies on platelets adhering to the subendothelial matrix and aggregating, a deficiency in platelet numbers leads to a **prolonged Bleeding Time**. **2. Why the other options are incorrect:** * **Hemophilia A (Factor VIII deficiency) & Hemophilia B (Factor IX deficiency):** These are disorders of **secondary hemostasis** (the coagulation cascade). In these conditions, the initial platelet plug forms normally, so the Bleeding Time is **normal**. However, the fibrin meshwork cannot stabilize the plug, leading to prolonged **Clotting Time (CT)** and a high **aPTT**. * **Coumadin (Warfarin) use:** Warfarin inhibits Vitamin K-dependent clotting factors (II, VII, IX, X). This affects the extrinsic and common pathways of coagulation. It prolongs the **Prothrombin Time (PT)** and **INR**, but does not affect the initial platelet plug formation; thus, the Bleeding Time remains **normal**. **High-Yield Clinical Pearls for NEET-PG:** * **BT** = Platelet function/count (Primary Hemostasis). * **CT/PT/aPTT** = Coagulation factors (Secondary Hemostasis). * **Von Willebrand Disease (vWD):** This is a unique "bridge" condition where **BT is prolonged** (due to defective platelet adhesion) and **aPTT may be prolonged** (due to low Factor VIII levels). * **Aspirin:** Prolongs BT by irreversibly inhibiting COX-1, preventing Thromboxane A2 synthesis.

Q: Serum contains all the clotting factors, except?

Labile factor. **Explanation:** The fundamental difference between plasma and serum is the presence of clotting factors. **Serum** is defined as plasma minus the clotting factors that are consumed during the coagulation process. **Why Labile Factor (Factor V) is the correct answer:** During the formation of a blood clot, certain factors are completely consumed as they are converted into their active forms or incorporated into the fibrin meshwork. These consumed factors are **I (Fibrinogen), II (Prothrombin), V (Labile factor), VIII (Anti-hemophilic factor), and XIII (Fibrin stabilizing factor).** Since Factor V is "labile" and utilized during the conversion of prothrombin to thrombin, it is absent in serum. **Analysis of Incorrect Options:** * **A. Plasma Thromboplastin (Factor XI):** This factor is not consumed during the clotting process and remains present in the serum. * **C. Hageman Factor (Factor XII):** This factor initiates the intrinsic pathway but is not consumed; it remains in the serum. * **D. Christmas Factor (Factor IX):** Like Factor XI and XII, Factor IX is a stable factor that is not consumed during clot formation and is therefore found in serum. **High-Yield Facts for NEET-PG:** * **Formula:** Serum = Plasma – (Fibrinogen + Factors II, V, VIII, XIII). * **Factors present in Serum:** VII, IX, X, XI, and XII (Stable factors). * **Prothrombin Time (PT)** measures Factors I, II, V, VII, and X. * **Clinical Pearl:** If a patient has a bleeding disorder, we test plasma, not serum, because serum lacks the essential clotting proteins required for diagnostic assays.

Q: What is the lifespan of neutrophils?

6 hours. **Explanation:** **Correct Answer: A. 6 hours** Neutrophils (Polymorphonuclear leukocytes) have the shortest lifespan among the white blood cells once they enter the circulation. The physiological lifespan of a neutrophil in the peripheral blood is approximately **6 to 10 hours**. After this brief period, they migrate into the tissues (diapedesis), where they survive for another 2 to 5 days before undergoing apoptosis or being consumed during phagocytosis. In the context of NEET-PG, "6 hours" is the standard textbook value for their half-life in the bloodstream. **Analysis of Incorrect Options:** * **B. 6 days:** This duration more closely reflects the total lifespan of a neutrophil including its time spent in the tissues, but it does not represent its circulating time in the blood. * **C. 10 days:** This is the approximate lifespan of **Platelets** (8–12 days). * **D. 15 days:** This does not correspond to any specific leukocyte lifespan; however, it is worth noting that the maturation process of a neutrophil in the bone marrow takes about 10–14 days. **High-Yield Clinical Pearls for NEET-PG:** * **Granulopoiesis:** The bone marrow maintains a large "storage pool" of neutrophils, containing about 5–10 times more cells than the circulating pool. * **Left Shift:** An increase in immature neutrophils (band cells) in the blood indicates an acute bacterial infection. * **Hypersegmented Neutrophils:** Seen in Megaloblastic anemia (Vitamin B12/Folate deficiency); defined as presence of neutrophils with >5 lobes. * **Lifespan Comparison:** * **Lymphocytes:** Can live for months to years (memory cells). * **Erythrocytes (RBCs):** 120 days. * **Monocytes:** 10–20 hours in blood (before becoming tissue macrophages).

Q: In erythropoiesis, which of the following statements is true?

Folic acid acts as a maturation factor.. ### Explanation **1. Why Option D is Correct:** Erythropoiesis requires specific nutrients for the maturation of red blood cells. **Folic acid and Vitamin B12** are essential cofactors for DNA synthesis (specifically the synthesis of thymidine triphosphate). A deficiency in these "maturation factors" leads to impaired cell division while cytoplasmic growth continues, resulting in **Megaloblastic anemia** (large, immature nucleated cells). **2. Why the Other Options are Incorrect:** * **Option A:** In erythropoiesis, the **cell size decreases** as the cell matures (from Proerythroblast to Mature RBC). This is accompanied by a decrease in the nuclear-cytoplasmic ratio. * **Option B:** Hemoglobin first begins to appear at the **Intermediate Normoblast** (Polychromatic erythroblast) stage. It is not visible at the Early Normoblast stage. * **Option C:** The **Late Normoblast** (Orthochromatic erythroblast) is characterized by a pyknotic (condensed) nucleus. At this stage, **mitosis stops** completely, and the nucleus is eventually extruded to form a reticulocyte. **3. High-Yield Clinical Pearls for NEET-PG:** * **First stage of Hemoglobin synthesis:** Proerythroblast (though not visible until later). * **Stage of Nucleus Extrusion:** Late Normoblast. * **Reticulocyte:** The last immature stage; it contains remnants of Golgi apparatus and RNA (ribosomes), which gives it a "reticular" appearance with supravital stains like **New Methylene Blue**. * **Erythropoietin (EPO):** The primary regulator, produced by the **peritubular interstitial cells** of the kidney in response to hypoxia.

Question 1

In which stage of erythropoiesis does hemoglobin first appear?

Accepted Answer

Basophil erythroblast

Answer

Proerythroblast

Answer

Orthochromatic erythroblast

Answer

Polychromatophil erythroblast

Question 2

Which of the following changes occurs in RBCs of stored blood?

Accepted Answer

Increase in Na+ and decrease in K+ content

Answer

Increase in Na+ and K+ content

Answer

Decrease in Na+ and K+ content

Answer

Increased activity of Na+-K+ ATPase

Question 3

A mechanic, after cutting his finger, presents with bleeding. Which endogenous molecule initiates the process of hemostasis?

Accepted Answer

Endothelin

Answer

Calcium

Answer

Thromboxane A2

Answer

Nitrous oxide

Question 4

Which of the following findings would best explain a prolonged bleeding time test?

Accepted Answer

Thrombocytopenia

Answer

Hemophilia A

Answer

Hemophilia B

Answer

Coumadin use

Question 5

Serum contains all the clotting factors, except?

Accepted Answer

Labile factor

Answer

Plasma thromboplastin

Answer

Hageman factor

Answer

Christmas factor

Question 6

Increased iron absorption is seen in which of the following conditions?

Accepted Answer

Iron deficiency anemia

Answer

Hypoxia

Answer

Inflammation

Answer

Antacids

Question 7

Regarding the immune response to bacterial infections, which of the following statements about neutrophils and macrophages is false?

Accepted Answer

Lysosomes of both neutrophils and macrophages contain large amounts of lipases.

Answer

Lysosomes of neutrophils and macrophages contain abundant proteolytic enzymes.

Answer

After phagocytosis, a neutrophil usually becomes inactivated and dies, while a macrophage can survive and function for a few months.

Answer

A single neutrophil can usually phagocytize up to 20 bacteria, while a single macrophage can phagocytize as many as 100 bacteria.

Question 8

What is the lifespan of neutrophils?

Accepted Answer

6 hours

Answer

6 days

Answer

10 days

Answer

15 days

Question 9

What is the first step in the initiation of primary hemostasis for clot formation?

Accepted Answer

Vasoconstriction

Answer

Fibrin deposition

Answer

Platelet adhesion

Answer

Thrombosis

Question 10

In erythropoiesis, which of the following statements is true?

Accepted Answer

Folic acid acts as a maturation factor.

Answer

The size of the cells increases in subsequent stages.

Answer

Hemoglobin appears at the early normoblast stage.

Answer

Mitosis occurs in the late normoblast at the fastest rate.

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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