Unit 7 - Hematopoiesis

hematopoiesis

blood cell formation

where does hematopoiesis occur

occurs in red bone marrow of skull, pelvis, ribs, sternum, and epiphysis of long bones

where is red bone marrow found

in spongey bone

where do blood cells come from

all blood cells are derived from a common stem cell called hemocytoblasts

what does hemocytoblast differentiation lead to

the formation of all other formed elements in a series of steps

what are erythrocytes unable to do

divide, grow, or synthesize proteins as adult cells

how long does it take for erythrocytes to wear out

100-120 days

what happens when erythrocytes are worn out

red blood cells are eliminated by phagocytes in the spleen or liver

how are lost erythrocytes replaced

by a division of hemocytoblasts in the red bone marrow

how is the rate of hemocytoblasts being created controlled

a hormone called erythropoietin

why do kidneys produce erythropoietin

as a response to reduced oxygen levels in the blood

how is homeostasis maintained

by a negative feedback loop from blood oxygen levels

negative feedback

a stimulus is released by the action of an effector

first step in negative feedback

the stimulus occurs due to a decreased red blood cell count, decreased availability of oxygen to blood, or increased tissue demands for oxygen

second step in negative feedback

there are reduced oxygen levels in blood

third step in negative feedback

the kidneys release erythropoietin

fourth step in negative feedback

erythropoietin stimulates red blood cell production in the red bone marrow

fifth step in negative feedback

there is an enhanced amount of erythropoietin

sixth step in negative feedback

there are more red blood cells

seventh step in negative feedback

there is an increased mount of oxygen, so carrying ability of blood increases

how does the number of RBC decrease

donate blood or blood cells wear out

what causes an increased tissue demands for oxygen

exercise