quiz nov 4

parathyroid hormone

responsible for bone resorption; emulsify bone, take Ca2+ out of bone and put it in the bloodstream

how does PTH influence blood Ca2+?

It elevates blood Ca2+ at the expensive of bone density (on a sinusoidal curve)

osteoblasts

make bone by taking Ca2+ out of the blood and putting it into bone, reduces blood Ca2+

osteoclasts

resorb bone, take away bone Ca2+ and put it into the blood, can elevate blood Ca2+; elevated rate by PTH

Are osteoblasts and osteoclasts always active? If so, what does this affect?

Yes; bone density is constant (constantly broken down and rebuilt)

If calcium is low in the blood, what happens to PTH?

PTH increases

If calcium is high in the blood, what happens to PTH?

PTH decreases

tumor in PT gland →

hypercalcemia; degrade bone too much

possible causes of low Ca2+ in the blood

• increased osteoblast activity

• not taking in dietary Ca2+ (milk)

• no vitamin D because no channels/receptors for Ca2+ to enter the cell (vitamin D upregulates channels)

  • can’t absorb Ca2+ (stays in GI tract for evacuation)

high PTH →

• Ca2+ resorbed into blood, less urinary excretion of Ca2+

• activated vitamin D finds intranucleic receptors of the epithelial cells in the intestine, upregulated calcium channels, more Ca2+ in blood

• elevate osteoclast activity, take more bone tissue and Ca2+ out of bone, emulsify bone matrix that is packed with Ca2+, release Ca2+ in blood

  • overall: restore blood Ca2+ concentrations

how does PTH work?

It has receptors on osteoclasts, making them more active, and on kidney hydroxylase, which activates Vitamin D by adding a hydroxyl, increases Ca2+ and Vitamin D in the blood

How to get Vitamin D?

Dietary supplements & exposure to sunlight

Why could Vitamin D be low?

• not going outside or not enough Vitamin D in the diet

  • Rickets: vitamin D deficiency

  • 516 nm sunlight activates Vitamin D

  • less melanin (lighter skin) less protected from radiation → easier to make Vitamin D

Calcitonin

peptide hormone; activates osteoblasts and inhibits osteoclasts; causes bone growth and Ca2+ absorption into the bone

where is calcitonin made?

parafollicular cells of the thyroid gland; weak polypeptide

PTH vs Calcitonin

PTH increases blood Ca2+ concentration, Calcitonin decreases blood Ca2+ concentration

top of sinusoidal curve

Z: zenith

bottom of sinusoidal curve

N: nadir

how long does it take to change blood Ca2+ levels?

7-8 hours; takes a while for things to happen

rickets

epiphyseal plates haven’t closed in children → lack of vitamin D → soft bones → crooked bones due to not fully mineralized bones (lack of Ca2+)

osteomalcia

adult lack of vitamin D; get frail and brittle bones but NOT soft

osteoporosis

imbalance between osteoblasts and osteoclasts; common in women after losing ovaries (no estrogen; estrogen inhibits osteoclastic activity→ osteoclasts break down bone)

you need vitamin D, calcitonin, PTH, and _?

EXERCISE; need to stress bones

what do we want the bone loss vs bone gain rate to be?

bone loss=bone gain

hypercalcemia

caused by tumor; high levels of Ca2+ in blood; not common because the kidney is good at excreting Ca2+

hypocalcemia

low levels of Ca2+ in the blood; overactive PTH → hypothyroidism

SRY

male gene on Y chromosome; signals development of sertoli cells → AMH → regression of the Mullerian duct & wolffian duct differentiates

SRY gene causes development of which cells?

sertoli cells & leydig cells

how many carbons do androgens have?

19

how many carbons do estrogens have?

18

which enzyme turns testosterone into estrogen?

aromatase

which parts of the penis are responsible for erections?

corpus cavernosum and corpus spongiosum

where is sperm made?

testes

which parts of the male reproductive tract add fluid/nutrients to sperm & make semen?

seminal vesicle, prostate gland, and bulbourethral gland; sperm start flagellating here

how do sperm travel?

testes/epididymis → vas deferens → seminal vesicle → prostate gland → bulbourethral gland → urethra

parts of testis

seminiferous tubule: makes sperm, has sertoli and leydig cells

myoid cell: contractile tissue that contracts and forces sperm into rete testis which store sperm → gets too crowded so they go to the efferent ductules→ epididymis

vas deferens: full of nonswimming sperm

where does spermatogenesis occur?

seminiferous tubules

parts of sperm

head: contains nucleus; only part that enters the egg

midpiece: mitochondria lined up

flagellum: tail

acrosome: helmet of sperm