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Endocrinology > Calcium and bone > Flashcards

Calcium and bone Flashcards

1
Q

What is the overall effect of parathyroid hormone on calcium?

A

It increases calcium (and phosphate) in the blood

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2
Q

What is the overall effect of calcitonin on calcium?

A

It decreases calcium (and phosphate) in the blood

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3
Q

What is the overall effect of calcitriol on calcium?

A

It increases calcium (and phosphate) in the blood

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4
Q

Impact of calcitonin/calcitriol/PTH on osteoclasts/osteoblasts and GIT absorption of calcium

A

Calcitonin increases osteoblast activity, increases osteoblast activity and reduces GIT absorpiton, whereas PTH and calcitriol do the opposite. i.e. calcitonin reduces calcium (and phosphate in the blood and PTH and calcitriol increases calcium (and phosphate) in the blood

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5
Q

What is the function of red bone marrow?

A

The primary site of haematopoesis

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6
Q

Where is red bone marrow found?

A

Flat bones (pelvis, skull, ribs) and epiphysis of long bones

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7
Q

Function of yellow bone marrow + location?

A

Found in the diaphyses of long bones and primarily site of fat storage (adipocytes)

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8
Q

What substances compose bone matrix?

A

Organic - Type 1 collagen and protein make up the organic osteoid portion which gives the bone tensile strength

Inorganic- Phosphate calcium crystals (hydroxyapatite) give bone it’s density and rigid strength

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9
Q

What makes bone rigid and dense?

A

The inorganic portion of the bone matrix - hydroxyapatite (calcium phosphate crystals)

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10
Q

Wha tis the function of osteoblasts?

A

Forming bone matrix by 1) creating proteins and type 1 collagen to form the osteoid (organic bone matrix for tensile strength) and by 2) creating alkaline phosphate, which aids the synthesis of hydoxyapatite (calcium and phsophate crystals) - the inorganic portion of bone that makes it dense and rigid

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11
Q

What are osteocytes and what are their function?

A

Osteocytes are mature bone cells and make up the majority of cells in mature bone. they live in lacunae and are derived from osteoprogenitor/osteoblast cells. Their primary function is communicating messages to osteoclast and osteoblasts to control their activity

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12
Q

What cells are osteoclasts derived from?

A

monocytes

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13
Q

Where are osteoclasts found?

A

In Howship’s lacunae

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14
Q

What cells are osteoblasts derived from?

A

Osteoprogenitor cells

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15
Q

Where is hyaline cartilage found and what is it’s function?

A

Larynx and articulating surfaces i.e. shoulder, hip, elbow, it reduces friction and absorbs shock

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16
Q

What is cartilage composed of and what cell forms cartilage?

A

Cartilage is composed of collagen and elastin, formed by chondroblasts (derived from fibroblasts)

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17
Q

Where is elastic cartilage found and what is it’s function?

A

Outer ear, epiglottis - to shape and support

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18
Q

Where is fibrous cartilage found and what is it’s function?

A

Pubic symphysis and intervertabral discs - to provide rigidity and absorb shock

19
Q

What do tendons connect?

A

muscle to bone

20
Q

What do ligaments connect?

A

Bone to bone

21
Q

What are synarthroses?

A

Immobile joints - skull bones

22
Q

What are amphiarthroses?

A

Slightly movable joints - vertebral joints and pubic symphysis

23
Q

What are diarthroses?

A

Synovial joints - movable joints - ball and socket (hip/shoulder), hinge joint (elbow/knee)

24
Q

What kind of cartilage is found in synovial joints?

A

Hyaline cartilage

25
Q

What kind of joint is the pubic symphysis?

A

An amphiarthrosis (slightly movable) composed of both fibrous cartilage and hyaline cartilage

26
Q

What hormone causes laxity of the pubic symphysis?

A

Relaxin

27
Q

How much do the pubic bones typically separate during pregnancy

A

2-3mm (9mm)

28
Q

What causes pelvic girdle pain post-partum?

A

Diastasis of the pubic symphysis during labour (the pubic bones separate)

29
Q

Where is parthyroid hormone derived from and what stimulates PTH release?

A

The parathyroid glands - released in response to decreased calcium

30
Q

What are the functions of PTH?

A

Overall function is to increase calcium in the blood
Bone - increases osteoclast activity, decreases osteoblast activity
Kidney - activates 1apha hydroxalase to convert vit D to it’s active form in the kidney, stimulates calcium re-absorption (in distal convoluted tubules)
GIT - stimulates calcium absorption

31
Q

What type of joint is a sacroiliac joint?

A

Synovial

32
Q

What is the function of 1alpha hydroxyalase?

A

Converts vitamin D to its active form (calcitriol)

33
Q

What is calcitriol?

A

1,25 (OH)2D3 - active vitamin D

34
Q

Where in the nephron is the majority of calcium and phosphate reabsorbed?

A

Proximal convoluted tubule

35
Q

How is calcitrol made?

A

Cholestrol converted to cholecalciferol (vit D3) by UV light, converted by the liver by 25 hydroxylase to 25 (OH)D3 = the store for vitD 1.5 month half life and then converted by the kidney by 1alphahydroxlase to 1,24(OH)2D3 (calcitrol) the active form which has a half life of 0.25 days

36
Q

Where is calcitonin derived from?

A

The parafollicular cells of the thyroid in response to high calcium or parathyroid hormone

37
Q

Daily requirement of calcium in pregnancy

A

1.5g/day

38
Q

Interpreting bone mineral density T scores

A

T score more than -1 = normal BMD, T score between -1.1 and -2.5 is low bone mineral density (osteopenia), T score greater than -2.5 is osteoporosis

39
Q

When does ossification occur in the fetus?

A

3rd trimester

40
Q

Why is pregnancy a hypocalcaemic state?

A

Calcium is transferred to the fetus, GFr is increased in the kidney (more calcium is excreted), there is decreased serum albumin

41
Q

Where is calcitonin produced?

A

In thyroid C cells

42
Q

Where is PTH produced?

A

In parathyroid chief cells

43
Q

How do you diagnose primary hyperparathyroidism?

A

High calcium, high PTH, low phosphate, high or normal ALP

44
Q

What is the most common cause of hypercalcaemia?

A

primary hyperparathyroidism?

Endocrinology (7 decks)

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