Skeletal System Continued

What releases calcitonin

thyroid

What happens when Ca2+ levels are too high

increased calcitonin > kidneys decrease Ca2+ reabsorption, decreased vitamin D synthesis > small intestine decreased Ca2+ absorption, bones increase osteoblast activity

What happens when Ca2+ levels are too low?

increased PTH > kidneys increase Ca2+ reabsorption, increased vitamin D > small intestine increased Ca2+ absorption, bones increase osteoclast activity

What releases PTH

parathyroid gland

What does PTH do?

opens Ca2+ channels in the distal tubule (reabsorbing transcellularly)

Why is osteoclast activity increased when Ca2+ levels are low?

want to increase Ca2+ so break down bone to release Ca2+

RBC formation (erythropoiesis) at altitutude

body adapts by increasing EPO and making more RBC since there is less O2

RBC formation after giving blood

increased EPO to make more RBC to replace the ones lost

What enzymes does the kidney release?

renin and erithropoitin

Cascade of events when imbalance of blood oxygen levels (stimulus: hypoxia, decreased O2 availability, increased tissue demands for O2)

kidneys releases erythropoietin > stimulates red bone marrow > enhanced erythropoiesis increases RBC count > increases O2 carrying ability of blood

EPO

hormone released by kidneys that stimulates hematopoitic stem cells to become RBC

RBC shelf life

120 days, no nucleus, always dying so need to replace them

Macrophage

immune cells, destroy RBC

RBC death (eryptosis) liver/spleen

Hb > Heme + Globin + Iron

What does Heme become

bilirubin > bile and urochrome

Globin

broken down into amino acids

urochrome

released into circulation, filtered by kidneys and excreted, yellow color

What does iron become?

transferrin and ferritin

transferrin

transporting iron back to bone in the form of transferrin

ferritin

iron storage in the form of ferritin