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46 Cards in this Set

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What is hematopoiesis?
Blood-cell production
Where does hematopoiesis occur?
First in the yolk sac, then spleen and liver, finally in the bone marrow
What is bone marrow?
gelatinous,highly vascular and cellular connective tissue located in marrow cavity of bones
What is the function of bone marrow?
Formation of blood cells, and delivery of blood cells into circulatory system
types of bone marrow
Red and yellow
Location of yellow bone marrow
in long bones of adults
Description of yellow bone marrow
inflitrated with fat, during childhood replaces red marrow in some sites, in adult not hematopoietic but has potential to do so if necessary
Location of red bone marrow
epiphyses of long bones as well as flat, irregular short bones (axial skeleton, sternum, areas of skull and vertebrae and certain regions of pelvis)
Description of red bone marrow
highly vascular, where blood cells differentiate and mature
Blood vessels of marrow compartment
nutrient artiers, central longitudinal arteries, radial arteries, sinusoids (note lacks lymphatics)
Nutrient arteries
From the periosteum pass through compact bone to enter the marrow space
Central longitudinal arteries
formed by the division of the nutrient artyer; they run parallel to the long axis of a bone
Radial arteries
spoke-like branches that arise form the longitudinal arteries to form sinusoins
enter Volkmann canals and eventually Haversian canals to supply the bone tissue
Sinusoids
-large
-highly attenuated endothelial lining
What in associated with the extravascular surface of sinusoids?
reticular fibers and adventitial reticulare cells
Where do sinusoids drain?
Central longitudinal vien which is drained by veins leavin gbone via the nutrient canal
Why don't sinusoids collapse?
Veins are smaller then arteries and therefore a high hydrostatic pressure within the sinusoids is developed
How do cells enter the sinusoidal lumen?
Transcellular. Form migration pores through the endothelial cells
What are the compartments in bone marrow?
Vascular and hematopoietic
Stromal cells in bone marrow
macrophages, reticular cells, fibroblasts, and endothelial cells
Hematopoietic growth factors
Produced and released by endothelial cells, fibroblasts, and other stromal cells
Function of macrophones near sinusoid
extend processes between endothelial cells into sinusoidal lumen and remove apoptotic cells, residual nuclei from orthochromatic erythroblasts, and particles
Function of endothelial cells
barrier that prevents immature cells from entering and allow mature one to enter
reticular fibers in bone marrow
Manufactured by the reticular cells and divide the bone marrow cavity into smaller compartments whicdh are then occupied with cords of hematopoietic cells
fat-filled reticular cells in bone marrow
recticular cells that have accumulated fat and transform red marrow into yellow marrow
glycoproteins in bone marrow
fibronectin, laminin and hemonectin
produced by reticular cells
Cell associations in red bone marrow
-erythroblasts and myelocytes
-orthochromatic erythroblasts and macrophages
-megakaryocytes and sinusoidal wall
Mesoblastic Stage of prenatal hematopoiesis
-begins at 2 weeks postconception via formation of blood islands
-mesoderm cells become primitive erythroblasts which become nucleated erythrocytes
-NO leukocytes
Hepatic and Splenic stage of prenatal hematopoiesis
-begins at 6 wks gestaation (liver) or 3 months (spleen)
-erythroblast similar to postnatal
-erythrocytes are still nucleated
-leukocytes begin to develop at 2 months in liver
Bone Marrow Stage of prenatal hematopoiesis
-Begins at 5 months
-becomes sole producer at birth
Stem Cells
-self-renewal
-differentiate into multiple cell lineages
-present in circulation and in bone marrow
Progenitor cells
-committed to single cell lineage (colony forming units)
-proliferate and differentiate into precursor cell
-affected by growth factors
-morphologically indistiguishable forom stem cells
Precursor cells
-identitable cells in specific lineages
CFU-EO
progenitor cell that gives rise to: eosinophil
CFU-Bas
progenitor cell that gives rise to: basophils
CFU-GM
progenitor cell that gives rise to: neutrophils and monocytes
CFU-Meg
progenitor cell that gives rise to: megakaryocytes
BFU-E
slow dividing progenitor cell that gives rise to: erythrocyte
CFU-E
progenitor cell that gives rise to: erythrocyte
Erythropoiesis
development of erythrocyte
Thrombopoiesis
development of platelets
Granulopoiesis
development of neutrophil, eosinophil and basophil
Monopoiesis
development of macrophage
Progenitor cells in erythropoiesis
BFU-E and CFU-E
Activity of BFU-E
-controlled by unknown regulator but when stimulated high rate of mitotic activity
-normally divides at slow rate
-makes CFU-E
Activity of CFU-E
-respond to erythropoietin (hormone made by kidney)
-gives rise to proerythroblast