Blood and Immunity Practice Questions

Q: A 45-year-old patient with chronic anemia presents with fatigue, dyspnea, and visible cyanosis. Recent blood tests show hemoglobin of 7 g/dL. Which of the following best explains the presence of cyanosis in this patient?

Increased deoxyhemoglobin concentration. ***Increased deoxyhemoglobin concentration*** - Cyanosis is defined as visible bluish discoloration of skin and mucous membranes that occurs when **≥5 g/dL of deoxygenated hemoglobin** is present in capillary blood. - By definition, cyanosis requires a sufficient **absolute amount of deoxyhemoglobin**, not just a low total hemoglobin. - In this patient with Hb 7 g/dL, if cyanosis is indeed present, it indicates that despite the anemia, there is still sufficient deoxyhemoglobin concentration to cross the threshold for visible cyanosis, likely due to severe hypoxemia or additional cardiopulmonary pathology. - **Important note:** Severe anemia alone typically does NOT cause cyanosis (patients appear pale); the presence of cyanosis here suggests a coexisting condition causing increased deoxyhemoglobin. *Decreased oxygen-carrying capacity of blood* - While this accurately describes the pathophysiology of anemia (reduced total hemoglobin), it does **not explain cyanosis**. - In fact, decreased oxygen-carrying capacity in severe anemia typically **prevents cyanosis** because there is insufficient total hemoglobin to generate the 5 g/dL deoxyhemoglobin threshold needed for visible cyanosis. - Classic teaching: "Anemic patients do not become cyanotic; they become pale." *Methemoglobinemia* - This condition involves hemoglobin oxidized to the ferric state (Fe³⁺), which cannot bind oxygen and causes a characteristic slate-gray or brownish cyanosis. - While methemoglobinemia can coexist with anemia, there is no indication in the clinical scenario (no exposure history, no "chocolate-brown" blood description) to suggest this diagnosis. *Peripheral vasoconstriction* - Peripheral vasoconstriction reduces blood flow to the skin, causing **pallor or a mottled appearance**, not true cyanosis. - Cyanosis is specifically due to increased deoxyhemoglobin in capillary blood, not reduced perfusion alone.

Q: What role do lymphocytes have in the body?

Immune response. ***Immune response*** - Lymphocytes, including **T cells** and **B cells**, are central to the **adaptive immune system**, recognizing and targeting specific pathogens and abnormal cells. - They produce **antibodies** (B cells) and mount **cell-mediated responses** (T cells) to protect the body from infections and cancer. *Blood clotting* - **Platelets** and **coagulation factors** are primarily responsible for blood clotting (hemostasis). - Lymphocytes do not directly participate in the formation of blood clots. *Oxygen transport* - **Red blood cells (erythrocytes)**, specifically their **hemoglobin** content, are responsible for transporting oxygen throughout the body. - Lymphocytes play no role in oxygen carriage. *Nutrient absorption* - **Enterocytes** in the small intestine are the primary cells responsible for nutrient absorption. - The lymphatic system (which includes lymphocytes) plays a role in absorbing **dietary fats**, but lymphocytes themselves are not directly involved in the absorption process.

Q: Which of the following is the earliest change to occur in response to chronic hypoxia?

Increased 2,3-BPG levels. ***Increased 2,3-BPG levels*** - Increased **2,3-bisphosphoglycerate** (2,3-BPG) levels in red blood cells is the **earliest compensatory mechanism** to improve tissue oxygen delivery in chronic hypoxia. - It begins to increase within **hours** and shifts the **oxygen-hemoglobin dissociation curve to the right**, reducing hemoglobin's affinity for oxygen and facilitating oxygen release to tissues. - This represents the first **metabolic adaptation** specifically targeting oxygen unloading at the tissue level. *Increased hematocrit* - An increased hematocrit, or **polycythemia**, is a **later compensatory response** to chronic hypoxia, mediated by erythropoietin. - It takes **several days to weeks** to develop as it requires new red blood cell production from the bone marrow. *Increased blood pH* - **Chronic hypoxia** leads to **hyperventilation** and **respiratory alkalosis**, which increases blood pH **immediately** (within minutes). - However, this is a **ventilatory response** to hypoxia, not a specific adaptation for improved oxygen delivery to tissues. - In fact, alkalosis **increases** hemoglobin's oxygen affinity (left shift), which is counterproductive for tissue oxygen delivery. *Increased erythropoietin production* - **Erythropoietin (EPO)** production in the kidneys is stimulated by hypoxia within hours, leading to increased red blood cell production. - While EPO levels rise relatively early, the **actual increase in red blood cell mass** (increased hematocrit) takes days to weeks, making this a delayed compensatory mechanism. - 2,3-BPG acts faster than the erythropoietic response can produce functional changes in oxygen-carrying capacity.

Q: A rightward shift in the oxygen-hemoglobin dissociation curve is caused by which of the following factors?

Increased 2,3-BPG levels. ***Increased 2,3-BPG levels*** - **2,3-Bisphosphoglycerate (2,3-BPG)** binds to the deoxyhemoglobin allosterically, stabilizing the **T (tense) state**, which has a lower affinity for oxygen. - This stabilization favors the release of oxygen to the tissues, thus shifting the oxygen-hemoglobin dissociation curve to the **right**. *Decreased temperature* - A **decrease in temperature** stabilizes the **R (relaxed) state** of hemoglobin, increasing its affinity for oxygen. - This effect shifts the oxygen-hemoglobin dissociation curve to the **left**, promoting oxygen uptake in the lungs. *Increased pH* - An **increase in pH** (alkalosis) also stabilizes the **R state** of hemoglobin, enhancing its affinity for oxygen. - This is known as the **Bohr effect**, and it results in a **leftward shift** of the curve. *Decreased CO2 levels* - **Decreased CO2 levels** lead to a decrease in H+ concentration, increasing pH and stabilizing the **R state** of hemoglobin. - This results in an **increased affinity for oxygen** and a **leftward shift** in the oxygen-hemoglobin dissociation curve.

Q: What is the primary function of erythrocytes in the human body?

Transport of oxygen. ***Transport of oxygen*** - Erythrocytes, also known as **red blood cells**, contain **hemoglobin**, a protein specialized in **binding and transporting oxygen** from the lungs to the body's tissues. - This function is vital for **cellular respiration** and the overall metabolic processes of the body. *Blood clotting* - **Platelets** (thrombocytes) are primarily responsible for **blood coagulation** and stopping bleeding by forming a clot at the site of injury. - Erythrocytes do not play a direct role in the **clotting cascade**. *Defense against pathogens* - **Leukocytes** (white blood cells), such as neutrophils, macrophages, and lymphocytes, are the primary cells involved in the **immune response** and defense against pathogens. - While essential for survival, erythrocytes are not part of the **immune system**. *Nutrient transport* - While blood plasma transports nutrients, erythrocytes themselves are **not directly responsible** for their transport. - **Plasma** carries dissolved nutrients like glucose, amino acids, vitamins, and minerals throughout the body.

Q: Which of the following best describes the function of hemoglobin in the blood?

Transport of oxygen. ***Transport of oxygen*** - **Hemoglobin** is a **metalloprotein** in red blood cells crucial for binding and transporting **oxygen** from the lungs to tissues. - Its structure, containing **heme groups** with iron, allows for efficient reversible binding of oxygen molecules. *Buffering blood pH* - While hemoglobin does have some minor buffering capacity, contributing to a stable **blood pH**, it is not its primary function. - The main systems for pH regulation are the **bicarbonate buffer system** and renal mechanisms. *Clot formation* - **Clot formation** is primarily mediated by **platelets** and a complex cascade of **coagulation factors** in the plasma. - Hemoglobin is not directly involved in the process of hemostasis or clot formation. *Immune response* - The **immune response** is primarily carried out by **white blood cells (leukocytes)**, antibodies, and the complement system. - Hemoglobin does not play a role in recognizing or fighting pathogens.

Q: What is the primary function of neutrophils in the immune response?

Phagocytosis of pathogens. ***Phagocytosis of pathogens*** - Neutrophils are the **most abundant type of white blood cell** and are rapid responders to sites of infection. - Their primary role is to **engulf and digest (phagocytose)** bacteria, fungi, and other foreign particles using powerful enzymes and reactive oxygen species. *Antibody production* - **B lymphocytes (plasma cells)** are responsible for producing antibodies, which are proteins that recognize and neutralize specific pathogens. - Neutrophils do not produce antibodies; they are part of the **innate, non-specific immune system**. *Killing infected host cells* - **Cytotoxic T lymphocytes (CTLs)** and **Natural Killer (NK) cells** are primarily responsible for identifying and killing host cells that have been infected by viruses or have become cancerous. - While neutrophils can kill certain pathogens, their role is not to directly eliminate infected host cells. *Presenting antigens* - **Antigen-presenting cells (APCs)**, such as macrophages, dendritic cells, and B cells, are specialized to process and present antigens to T lymphocytes. - Neutrophils are not considered primary APCs and have a limited role in initiating adaptive immune responses.

Question 1

Which factor has the most significant influence on the oxygen dissociation curve?

Accepted Answer

2,3-BPG

Answer

pH

Answer

Temperature

Answer

All of these

Question 2

Which factor predominantly influences the rightward shift of the oxygen dissociation curve?

Accepted Answer

2,3-Bisphosphoglycerate (2,3-BPG)

Answer

pH (Bohr effect)

Answer

Temperature increase

Answer

Carbon monoxide levels

Question 3

What is the mechanism by which hemolysis causes jaundice?

Accepted Answer

Increased production of unconjugated bilirubin due to hemolysis

Answer

Increased production of conjugated bilirubin due to liver dysfunction

Answer

Decreased conjugation of bilirubin in the liver

Answer

Increased reabsorption of bilirubin in the intestines

Question 4

A 45-year-old patient with chronic anemia presents with fatigue, dyspnea, and visible cyanosis. Recent blood tests show hemoglobin of 7 g/dL. Which of the following best explains the presence of cyanosis in this patient?

Accepted Answer

Increased deoxyhemoglobin concentration

Answer

Methemoglobinemia

Answer

Peripheral vasoconstriction

Answer

Decreased oxygen-carrying capacity of blood

Question 5

What role do lymphocytes have in the body?

Accepted Answer

Immune response

Answer

Blood clotting

Answer

Oxygen transport

Answer

Nutrient absorption

Question 6

Which of the following is the earliest change to occur in response to chronic hypoxia?

Accepted Answer

Increased 2,3-BPG levels

Answer

Increased blood pH

Answer

Increased hematocrit

Answer

Increased erythropoietin production

Question 7

A rightward shift in the oxygen-hemoglobin dissociation curve is caused by which of the following factors?

Accepted Answer

Increased 2,3-BPG levels

Answer

Decreased temperature

Answer

Increased pH

Answer

Decreased CO2 levels

Question 8

What is the primary function of erythrocytes in the human body?

Accepted Answer

Transport of oxygen

Answer

Blood clotting

Answer

Defense against pathogens

Answer

Nutrient transport

Question 9

Which of the following best describes the function of hemoglobin in the blood?

Accepted Answer

Transport of oxygen

Answer

Buffering blood pH

Answer

Clot formation

Answer

Immune response

Question 10

What is the primary function of neutrophils in the immune response?

Accepted Answer

Phagocytosis of pathogens

Answer

Antibody production

Answer

Killing infected host cells

Answer

Presenting antigens

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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