Test: Hematologic System - 1 - MCAT MCQ

Blood is composed of nearly 50% water by volume. The plasma fraction typically occupies a much larger volume than the red cell fraction.
In whole blood, the components are suspended equally within the fluid. Centrifugation displaces the components by applying a rotational force to the suspension.
Centrifugation separates particles in a suspension on the basis of their density. Red blood cells (iron) is much more dense than other blood components.
The red cell fraction has a greater density than the plasma fraction.

Hemoglobin is the protein responsible for transporting oxygen in the blood. It binds to oxygen in the lungs and releases it to tissues throughout the body. Hemoglobin is primarily found in red blood cells.

Hematocrit refers to the percentage of the total blood volume occupied by red blood cells. It is a measure of the concentration of red blood cells in the blood. A relative increase in hematocrit means there is a higher proportion of red blood cells compared to the total blood volume.

Dehydration is a condition characterized by inadequate fluid intake or excessive fluid loss, leading to a decrease in the overall blood volume. In this state, the concentration of red blood cells in the blood remains relatively constant, but the plasma volume decreases. As a result, the proportion of red blood cells in the blood increases, leading to a higher hematocrit value.

An increase in bicarbonate (HCO₃^-) in the blood is typically associated with a decrease in blood pH (acidosis). In an acidic environment, the affinity of hemoglobin for oxygen decreases, causing a rightward shift of the oxygen-hemoglobin dissociation curve. This shift promotes the release of oxygen from hemoglobin, allowing it to be delivered to the tissues.

The increase in bicarbonate indirectly affects the oxygen affinity of hemoglobin by binding with free protons (H⁺). When bicarbonate combines with protons, it forms carbonic acid (H₂CO₃), which can then dissociate into carbon dioxide (CO₂) and water (H₂O). This reaction helps regulate blood pH and maintain acid-base balance.

The binding of free protons by bicarbonate leads to a decrease in the concentration of protons in the blood. This reduction in proton concentration helps to stabilize the deoxygenated form of hemoglobin (T-state), which has a higher affinity for oxygen. As a result, the oxygen affinity of hemoglobin increases, allowing it to bind more readily with oxygen in the lungs and release it to the tissues.

Therefore, the correct answer is D. An increase in bicarbonate relative to all other molecules in the blood would increase the oxygen affinity of hemoglobin by binding with free protons.

An individual with blood type O- could potentially have which blood antibodies present in their plasma?
A.Both A and B antibodies
B.Neither A or B antibodies
C.B antibodies only
D.A antibodies only

The coagulation cascade involves a series of enzymatic reactions that lead to the formation of a fibrin clot, which helps in the process of blood coagulation. There are two primary pathways involved: the intrinsic pathway and the extrinsic pathway.

The intrinsic pathway is initiated by factors present within the blood, while the extrinsic pathway is triggered by factors outside the blood. These pathways eventually converge to a common pathway, which leads to the final formation of a fibrin clot.

Factor X, also known as Stuart-Prower factor, is a coagulation factor that plays a crucial role in both the intrinsic and extrinsic pathways. It is activated in each pathway and acts as a common link between them. Once activated, Factor X converts prothrombin to thrombin, which in turn converts fibrinogen to fibrin, resulting in clot formation.

The extrinsic pathway of the coagulation cascade is primarily triggered by an endothelial cell insult or tissue factor (TF) exposure. Endothelial cells are the cells that line the blood vessels, and when they are damaged or injured, they release tissue factor (TF), also known as factor III. Tissue factor is a protein that plays a crucial role in initiating the extrinsic pathway.

When endothelial cells are insulted, tissue factor comes into contact with circulating factor VII, which then binds to tissue factor and becomes activated. The activated factor VII, together with tissue factor, forms a complex known as the extrinsic tenase complex. This complex subsequently activates factor X, which is a key step in the coagulation cascade.

• The bone marrow is the major site of hematopoiesis in adults, and is the home of all precursor cells relating to both white and red blood cells.
• The spleen is most important as a filter for blood, though it also plays a key role in red cell production during infancy and in situations of disease.
• The kidney secretes erythropoietin in response to low oxygen levels. This hormone stimulates red blood cell production.
• The thymus is important for immune cell (white cell) production and maturation, but does not play an active role in the production of red blood cells.

Cell lineage refers to the developmental pathway that cells undergo to reach their mature functional state. In terms of cell lineage, red blood cells and macrophages belong to the myeloid lineage, while B cells belong to the lymphoid lineage.

The myeloid lineage gives rise to various types of blood cells involved in innate immunity, including red blood cells (erythrocytes) and macrophages. Red blood cells are responsible for oxygen transport, while macrophages play a role in phagocytosis and immune defense.

The lymphoid lineage gives rise to cells involved in adaptive immunity, including B cells. B cells are responsible for producing antibodies and are crucial in humoral immune responses.

T cells are derived from the common lymphoid progenitor (CLP). The CLP is a precursor cell in the bone marrow that gives rise to various types of lymphocytes, including T cells, B cells, and natural killer (NK) cells. T cells undergo further development and maturation in the thymus gland, hence the name "T cells." These cells play a crucial role in cell-mediated immune responses and are involved in recognizing and targeting specific pathogens.