BIO Lecture Notes - Bone Marrow, Yolk Sac, Erythropoiesis
20 Oct 2022
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Erythropoiesis is the process of origin, development and maturation of erythrocytes. In adults, after the age of 20 years, r. b. c. are produced by red bone marrow of all membranous bones like skull bones, vertebra, ribs, scapula and pelvic bones and from the ends of long bones like humerus and femur. Proerythroblast: high nuclear to cytoplasmic ratio, immature nuclear chromatin,1-2 nucleoli, basophilic cytoplasm. Basophilic erythroblast (early): high nuclear to cytoplasmic ratio, Polychromatophilic erythroblast: round nucleus with mature (clumped chromatin), no nucleoli, cytoplasm is grayish in colour due to hemoglobin synthesis occurring at this stage. Orthochromic erythroblast: densly pyknotic nucleus with well hemoglobinized cytoplasm (reddish). Reticulocyte: late erythroblasts extrude nuclei to become reticulocyte. Intermediate position between nucleated rbcs and mature red blood cells. Mature rbcs: size of a mature lymphocyte nucleus. Has central pallor 1/3rd the diameter of the cell. Erythropoietin is a hormone secreted by juxtaglomerular apparatus of kidney. Renal hypoxia is the stimulant for secretion of erythropoietin.
