block 5 lecture 5 bone metabolism

Question 1

what percentage is organic bone material?

Answer 1

40%

Question 2

what percentage is inorganic bone material?

Answer 2

60%

Question 3

what is the organic materials of bone?

Answer 3

type 1 collagen and non-collagenous protein

Question 4

what is the inorganic portion of bone?

Answer 4

calcium hydroxyapatite

Question 5

what is trabecula bone?

Answer 5

cancllous and spongy bone

Question 6

what are osteoclasts?

Answer 6

multi nucleated cells formed from many monocytes

Question 7

what can increase the resorption of bone by an osteoclast?

Answer 7

bigger osteoclasts perform more aggressive resorption of bone

Question 8

how do osteoclasts adhere to the bone matrix?

Answer 8

by forming lipid like adhesions and express strong intergrin interactions

Question 9

what do osteoclasts do?

Answer 9

secrete enzymes and acids to degrade matrix

Question 10

what happens to degraded bone material by osteoclasts?

Answer 10

shoots up through apical membrane and removed from the cell

Question 11

what are the osteoclast resorption pits called?

Answer 11

howships lacuna

Question 12

what are osteoblats?

Answer 12

mononucleated stromal cells

Question 13

what do osteoblasts come from?

Answer 13

mesenchymal cells

Question 14

what do osteoblasts do?

Answer 14

mineralize bone matrix to replace removed bone

Question 15

what do osteoblasts form into?

Answer 15

osteocytes

Question 16

what do the extesions of osteocytes make connections with?

Answer 16

the bones surface and other osteocytes

Question 17

what do the processes of osteocytes act as?

Answer 17

mechnosensors

Question 18

hat stops osteoclasts resorbing?

Answer 18

reversal stage

Question 19

what is the matrix that osteoblasts lay down?

Answer 19

type 1 collagen and non colagenous protein

Question 20

what is the bone matrix called when it is initially laid down?

Answer 20

osteoid

Question 21

what are some signals involved in bone growth?

Answer 21

parathyroid hormine, vitamin D, calcitonin, growth hormone, growth factors, oestrogen, cytokines

Question 22

what is the calcuim resevoir?

Answer 22

skeleton

Question 23

what are the three fractions of calcium in serum?

Answer 23

ionised calcium, protein bound calcium and complexed calcium

Question 24

what is Ca2+ maintained by?

Answer 24

PTH, Vitamin D, cacitonin

Question 25

where do you find phsphate?

Answer 25

skeleton and extracellular fluid

Question 26

what are the three fractions of phsophate in serum/

Answer 26

ionised phosphate | protein bound phophate and complexed

Question 27

what is phsphate metabolism regulated by?

Answer 27

PTH

Question 28

where can you recieve vitamin D?

Answer 28

in the skin, digestion

Question 29

in the skin how is vitamin D procuced?

Answer 29

7-dehydrocholesterol is converted by UV light to vitamin D

Question 30

how is vitamin D activated?

Answer 30

2 rounds of hydroxylation

Question 31

where does the first hydroxylation of vitamin D occur?

Answer 31

liver

Question 32

where does the second hydroxylation of vitamin D occur?

Answer 32

kidney

Question 33

what type of vitamin D is responsible for most biological mechanisms?

Answer 33

principle hormonal form

Question 34

what is the production of vitamin D regulated by?

Answer 34

PTH

Question 35

what is the production of vitamin D inhibited by?

Answer 35

elevated serum calcium or phosphate

Question 36

what doe vitamin D do?

Answer 36

increases calcium and phosphate absorption from intestines mobilised calcium and phophate from bone induces marrow monocytes to increase production of osteoclasts to promote resorption

Question 37

what seceretes PTH?

Answer 37

parathyroid gland

Question 38

what can PTH stimulate?

Answer 38

osteoclast resroption decresases renal calcium secretion increases renal production of vitamin D

Question 39

what is parathyroid hormone related protein produced by?

Answer 39

normal and malignant cells

Question 40

what is PTHrP required for?

Answer 40

development, regulator of proliferation and mineralisation of chondrocytes

Question 41

what s calcitonin?

Answer 41

small poly peptide

Question 42

what releases calcitonin?

Answer 42

parafollicular cells of the thyroid

Question 43

what induces the release of calcitonin?

Answer 43

high plasma calcium levels

Question 44

what does calcitonin do?

Answer 44

reduces bone resorption by activating calcitonin receptors expressed by osteoclasts

Question 45

physiology of calcium metabolism to increase?

Answer 45

low calcium in circulation is detected by parathyroid gland, PTH is secreted, PTH and vitamin D increases the mobilisation of Ca into circulation

Question 46

physiology of calcium metabolism to decrease?

Answer 46

calcium is detected by thyroid C cells, which increases the secretion of calcitonin, which targets osteoclats to limit resrption and decrease calcium in circulation

Question 47

how does oestrogen affect bone metabolism?

Answer 47

reduce resorption by inhibiting osteoclastogenesis and inhibiting osteoclast function

Question 48

how does androgens affect bone metabolism?

Answer 48

low levels means low bone density in men | they target osteoclasts

Question 49

what are the causes of hypercalcium?

Answer 49

primary hyperthyroidism, malignancy, immobalisation, vitamin D toxicity

Question 50

what is primary hyperthyroidism?

Answer 50

excessive secretion of PTH

Question 51

what causes primary hyperthyroidism?

Answer 51

solitary adenoma of parathyroid glands

Question 52

what are the symptoms of primary hyperthyroidism?

Answer 52

excessive skeletal erosion, kidney stones

Question 53

causes of hypocalcemia?

Answer 53

renal failure, vitamin D defficiency, prematurity (immture vitamin D metabolism, immature parathyroid gland)

Question 54

what is osteomalacia caused by?

Answer 54

vit D defficiency, malabsorption, renal disease, lack of sunlight, anticonvulsants inhibit vitamin D synthesis

Question 55

osteomalacia symptoms?

Answer 55

bone pain around hips, muscle weakness, alavated alkaline phosphatase levels, decreased mineralisation, long bones bowing

Question 56

what is osteoporosis?

Answer 56

net loss of bone mass and decreasd bone mineral density

Question 57

in what type of person is osteoporosis common?

Answer 57

post menopausal woman, elderly, inactive

Question 58

treatment of osteoporosis?

Answer 58

calcium supplementation, hormone replacement therapy, bisphosphates, calcitonin, selective estrogen receptor modulators