MLT GlobeHematology: Hematopoiesis & general hematology – page 2
38 Hematology MCQs on Hematopoiesis & general hematology with answers and explanations.
Which interleukin, also called multi-CSF, stimulates progenitors of several myeloid lineages?
IL-3 supports early multipotent progenitors of granulocytes, monocytes, erythroid cells and megakaryocytes. IL-2 is a T-cell growth factor; IL-4 drives B-cell class switching.
Which membrane component chiefly determines red cell shape and deformability?
Spectrin, actin, ankyrin and protein 4.1 form a skeletal network under the bilayer that gives shape and flexibility. Defects cause spherocytosis or elliptocytosis.
At which stage of granulocyte maturation are azurophilic (primary) granules first produced in abundance?
Promyelocytes synthesize abundant primary granules. Myeloblasts have few or none, and specific granules first appear at the myelocyte stage.
By about what stage of fetal development does bone marrow become the main site of hematopoiesis?
Marrow hematopoiesis starts around the fourth to fifth month and becomes dominant by the end of the sixth month, overtaking the liver.
During the yolk sac (mesoblastic) phase of hematopoiesis, which cells are mainly produced?
Yolk sac blood islands generate nucleated primitive erythroblasts making embryonic hemoglobins (Gower-1, Gower-2, Portland).
Which change does NOT occur as red cell precursors mature?
Erythroid nuclei condense and shrink (pyknosis) and are then extruded; they do not lobulate. Lobulation is a feature of granulocyte maturation.
Within the bone marrow stroma, which cell acts as a local energy reserve and fills space not used for active blood formation?
Marrow adipocytes store lipid that serves as a local energy source and expand where hematopoiesis regresses. Reticular cells form the supporting meshwork but are not the energy store.
Approximately how many mature red cells normally arise from a single pronormoblast?
A pronormoblast undergoes about four mitotic divisions during maturation, giving roughly 16 red cells. Multipotent stem cells produce vastly more cells through amplification.
Besides delivering oxygen, hemoglobin helps carry carbon dioxide from tissues, mainly by forming:
CO2 binds terminal amino groups of globin as carbaminohemoglobin, and deoxyhemoglobin buffers H+ from bicarbonate formation. Carboxyhemoglobin is bound carbon monoxide.
When fully saturated, each gram of hemoglobin binds approximately how much oxygen?
The value 1.34 mL O2/g (Hüfner's constant, in practice) is used to calculate blood oxygen content together with saturation and dissolved oxygen.
In which condition is splenectomy generally contraindicated?
Splenectomy helps when the spleen destroys cells. In marrow failure the problem is production, so removing the spleen gives no benefit and adds infection risk.
Which splenic function is most important for protection against encapsulated bacteria?
Red pulp macrophages and marginal zone B cells clear poorly opsonized encapsulated organisms and aged cells. The adult spleen does not normally produce blood cells.
Which structure belongs to the splenic red pulp rather than the white pulp?
The red pulp consists of cords and venous sinusoids that filter blood. The white pulp contains T-cell PALS and B-cell follicles with germinal centres.
Which vaccine is NOT part of routine preparation for elective splenectomy?
Asplenic patients are vulnerable to encapsulated bacteria, so pneumococcal, meningococcal and Hib vaccines are given. BCG protects against tuberculosis, which is not an asplenia-related risk.
When hematopoiesis first moves into the marrow cavity during fetal development, which bone shows activity earliest?
The medullary phase begins around the fourth to fifth fetal month, with the clavicle the first bone to show marrow hematopoiesis, followed by other developing bones.
How are phospholipids distributed in the red cell membrane?
The membrane is an asymmetric bilayer: phosphatidylcholine and sphingomyelin dominate outside, phosphatidylserine and ethanolamine inside. Hydrophobic tails face each other, away from water; the hexagonal lattice is spectrin.
In normal bone marrow, where are developing red cell precursors found?
Erythroblastic islands consist of normoblasts surrounding a macrophage that supplies iron and engulfs extruded nuclei, located close to marrow sinusoids.
Why do lipids exchange between the red cell membrane and plasma lipoproteins?
Mature red cells cannot synthesize lipids, so they renew membrane cholesterol and phospholipids by exchange with plasma. Liver disease can disturb this, forming target or spur cells.