23 topics with concise reviews: definitions, key facts, and class questions.
This section covers the morphology and functions of the unified system responsible for blood cell renewal and body defense. Here, we thoroughly examine the structure of central (red bone marrow, thymus) and peripheral organs of hematopoiesis and immunogenesis, including the spleen, lymph nodes, tonsils, appendix, and mucosa-associated lymphoid tissue.
Special attention is given to the cellular conveyor. You will study all stages of postnatal hemopoiesis: erythropoiesis, granulocytopoiesis, thrombocytopoiesis, and lymphopoiesis, along with their regulation mechanisms. The immunology section covers the fundamentals of cellular and humoral immunity, the nature of antigens, the structure of immunoglobulins, and the major histocompatibility complex.
During practical classes and exams, instructors most frequently require identifying the microscopic structure of the spleen without errors, describing the histophysiology of the lymph node, and outlining the morphology of lymphoid follicles. Understanding the difference between T- and B-dependent zones is your key to successfully diagnosing histological slides.
They originate in the mesenchyme of the yolk sac wall strictly inside primary blood vessels (intravascularly) via the megaloblastic pathway.
What is the difference between a child's and an adult's bone marrow?
In children under 12–18 years of age, red bone marrow is found even in the diaphyses of tubular bones. In adults, hematopoietic tissue there is replaced by adipose tissue, turning into yellow bone marrow.
How does an HSC differ from a progenitor cell?
The HSC is pluripotent (can give rise to all blood cells) and indefinitely maintains its population. The progenitor cell is partially determined (oligopotent) and has a limited capacity for self-maintenance.
Which cell of the erythroid series divides last?
Polychromatophilic erythroblast. This is the final stage that retains mitotic activity; thereafter, the capacity for division is lost.
At what stage do specific granules appear in granulocytes?
Secondary (specific) granules first appear at the myelocyte stage. It is from this moment that cells can be divided into neutrophilic, eosinophilic, and basophilic lineages.
How does a megakaryoblast differ from other blasts?
Externally, with standard staining, the megakaryoblast is practically indistinguishable from blast cells of other hematopoietic lineages.
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