7.4 – Physiology of osseous tissue

Question 1

mineral resorption is the process of…

Answer 1

dissolving bone

Question 2

resorption is carried out by ___

Answer 2

osteoclasts

Question 3

hypocalcemia is…

Answer 3

calcium deficiency

Question 4

hypercalcemia is…

Answer 4

calcium excess

Question 5

calcium homeostasis depends on balance b/n…

Answer 5

1) dietary intake
2) urinary and fecal losses
3) exchanges w/ the osseous tissue

Question 6

calcium homeostasis is regulated by ___ hormones

the hormones are…

Answer 6

3

calciferol, calcitonin, and parathyroid hormone

Question 7

calciferol is a form of ___ produced by the sequential action of the ___, ___, and ___

Answer 7

vitamin D

skin, liver, and kidneys

Question 8

calcitriol behaves as a ___, a blood-borne chemical messenger from one organ to another.

It is called a ___ only because it is added to the ___ as a safeguard for people who don’t get enough sunlight to initiate adequate synthesis in the skin.

Answer 8

hormone

vitamin
diet

Question 9

the principal function of calcitriol is to ___ the blood calcium concentration.

it does this in ___ ways

Answer 9

raise

3

Question 10

3 ways that calcitriol raises blood calcium concentration:

(1)

Answer 10

increases calcium absorption by the small intestine

Question 11

3 ways that calcitriol raises blood calcium concentration:

(2)

Answer 11

increases calcium resorption from the skeleton

calcitriol binds to osteoblasts, which then stimulate stem cells to differentiate into osteoclasts

the new osteoclasts liberate calcium and phosphate ions from bone

Question 12

3 ways that calcitriol raises blood calcium concentration:

(3)

Answer 12

it weakly promotes the reabsorption of calcium ions by the kidneys, so less calcium is lost in the urine

Question 13

calcitonin is produced in the ___ ___

Answer 13

thryoid gland

Question 14

calcitonin is secreted when the blood calcium concentration…

Answer 14

rises too high

Question 15

calcitonin ___ the blood calcium concentration by ___ principal mechanisms

Answer 15

lowers

2

Question 16

calcitonin lowers the blood calcium concentration by 2 principal mechanisms:

(1)

Answer 16

osteoclast inhibition:

calcitonin firstly reduces osteoclast activity –> osteoclasts liberate less calcium from the skeleton

Question 17

calcitonin lowers the blood calcium concentration by 2 principal mechanisms:

(2)

Answer 17

osteoblast stimulation:

calcitonin secondly increases the number and activity of osteoblasts, which deposit calcium into the skeleton

Question 18

mineral deposition (mineralization) is a…

Answer 18

crystallization process in which calcium, phosphate, and other ions are taken from the blood plasma and deposited in bone tissue

Question 19

parathyroid hormone (PTH) is secreted by the ___ ___

Answer 19

parathyroid glands

Question 20

parathyroid glands release PTH when blood calcium is ___

Answer 20

low

Question 21

PTH ___ the calcium level by ___ mechanisms

Answer 21

raises

4

Question 22

PTH raises the calcium level by 4 mechanisms:

(1)

Answer 22

it binds to receptors on the osteoblasts, which in turn stimulate the osteoclast population and promote bone resorption

Question 23

PTH raises the calcium level by 4 mechanisms:

(2)

Answer 23

it promotes calcium reabsorption by the kidneys, so less calcium is lost in the urine

Question 24

PTH raises the calcium level by 4 mechanisms:

(3)

Answer 24

it promotes the final step of calcitriol synthesis in the kidneys, thus enhancing the calcium-raising effect of calcitriol

Question 25

PTH raises the calcium level by 4 mechanisms: (4)

Answer 25

it inhibits collagen synthesis by osteoblasts, thus inhibiting bone deposition

Question 26

phosphate homeostasis is ___ regulated as calcium levels

Answer 26

not as tightly regulated

Question 27

phosphate is required for...

Answer 27

bone strength component of DNA, RNA, ATP, phospholipids, and other compounds

Question 28

how does calcitriol affect phosphate levels?

Answer 28

raises phosphate blood level while raising calcium blood level

Question 29

how does parathyroid hormone affect blood phosphate levels?

Answer 29

lowers the blood phosphate level by promoting its urinary excretion

Question 30

other factors affecting bone: why do adolescent girls grow faster but for a shorter time than boys?

Answer 30

adolescent girls grow faster and attain their full height earlier adolescent girls begin puberty earlier estrogen has a stronger effect than testosterone

Question 31

other factors affecting bone: why do adolescent boys grow slower than girls?

Answer 31

adolescent boys grow slower but for a longer time --> attain full height later adolescent boys begin puberty later testosterone has a weaker effect than estrogen

Question 32

___ ___ eventually deplete the cartilage of the ___ ___, bring about closure of the ___, and put an end to one's growth in height

Answer 32

sex steroids epiphysial plates epiphyses

Question 33

mineral deposition into bones begin where?

Answer 33

in fetal ossification

Question 34

what is the process of dissolving bone and releasing minerals into the blood called?

Answer 34

resportion

Question 35

in the human body, where is 99% of the calcium found?

Answer 35

the bones

Question 36

if a patient has abnormally high blood calcium levels, they are said to have a condition called ___

Answer 36

hypercalcemia

Question 37

calcitriol acts on which organs to raise blood calcium levels?

Answer 37

bones small intestines kidneys

Question 38

where does the calcium and phosphate used to mineralize bone come from?

Answer 38

the blood (osteoblasts build new bone using calcium and phosphate from the blood)

Question 39

what does the hormone calcitonin do?

Answer 39

calcitonin repsonds to hypercalcemia there is too much calcium in the blood --> calcitonin lowers blood calcium levels calcitonin inhibits osteoclasts and stimulates osteoblasts --> prevents calcium from coming out of bone, takes calcium out of blood and puts it into bone --> lowers blood calcium levels

Question 40

in order for minerals such as calcium and phosphate to be liberated from bone, which process must occur?

Answer 40

resorption

Question 41

PTH is a hormone released by parathyroid glands in response to what?

Answer 41

low blood calcium levels

Question 42

in the human body, what percentage of calcium in the body is found in the bones?

Answer 42

99%

Question 43

which mineral is more closely regulated by the body – calcium and phosphate?

Answer 43

calcium

Question 44

which condition is characterized by excessive excitability of the nervous and muscular systems due to low blood calcium levels?

Answer 44

hypocalcemia

Question 45

do adolescent girls or boys tend to attain their full height earlier in life?

Answer 45

adolescent girls

Question 46

vitamin D, also known as ___, raises the blood calcium level

Answer 46

calcitriol

Question 47

which hormone inhibits osteoclasts and stimulates osteoblasts to lower blood calcium levels?

Answer 47

calcitonin

Question 48

a low blood calcium level stimulates the release of which hormone?

Answer 48

parathyroid hormone

Question 49

how does calcitriol affect blood phosphate levels?

Answer 49

it raises them

Question 50

which hormone has a greater effect on bone growth?

Answer 50

estrogen

Question 51

calcitriol acts on which organs to raise blood calcium levels?

Answer 51

kidneys small intestines bones

Question 52

what does the hormone calcitonin do?

Answer 52

responds to hypercalcemia --> calcitonin lowers blood calcium levels inhibit osteoclasts and stimulate osteoblasts

Question 53

which hormone inhibits osteoclasts and stimulates osteoblasts to lower blood calcium levels?

Answer 53

calcitonin

Question 54

what does the hormone calcitonin do?

Answer 54

responds to hypercalcemia --> lowers blood calcium levels inhibits osteoclasts and stimulates osteoblasts