W10 - Skeletal System (Lecture)

Question 1

What two cell types do mesenchymal stem cells become?

Answer 1

Osteoblasts and chondrocytes

Question 2

What stem cells form osteoclasts?

Answer 2

Hematopoietic

Question 3

What do osteoblasts become?

Answer 3

Osteocytes

Question 4

What do osteoblasts/clasts do?

Answer 4

Osteoblast - build bone, osteoclast - reduce bone

Question 5

Paresthesia and muscle twitching occur when theres low calcium, what is a third symptom?

Answer 5

Numbness

Question 6

If theres too much calcium, digestive stress, bone pain + muscle weakness occur, what are 4 other symptoms?

Answer 6

Thirst, frequent urination, lethargy, fatigue and cardiac arrhythmia

Question 7

What three things are balanced during bone maintenance?

Answer 7

Bone formation, resorption and elongation

Question 8

Do osteoblast/clasts work in reduced/increased blood calcium?

Answer 8

Blast - reduced Ca, Clast - increased Ca

Question 9

Growth hormone increases length of bones, what 2 other things does it do?

Answer 9

Enhances mineralisation and improves bone density

Question 10

How does the effects of GH differ between youth and adults?

Answer 10

Youth - growth plate open so adds to length and thickness. Adults - growth plate closed so only adds to thickness

Question 11

What does thyroxine released by the thyroid do?

Answer 11

It has a +ve effect on GH released from pituitary gland

Question 12

Sex HMs promote bone formation/maintenance of bone density, what else is promoted?

Answer 12

Closure of growth plate

Question 13

Estrogen in females causes reduced bone length, how does this happen?

Answer 13

It causes earlier growth plate closure

Question 14

What happens during menopause?

Answer 14

Bone density is lost

Question 15

What two receptors are found in the growth plate of the bone?

Answer 15

Androgen and estrogen receptors

Question 16

Calcitriol is an active metabolite of vitamin D3, what is V D3 derived from?

Answer 16

Cholesterol

Question 17

What is the function of VD?

Answer 17

Facilitates intestinal absorption of calcium, phosphate and magnesium

Question 18

VD binds intracellular VDR, as well as a VD binding site there is another binding ssite on VDR, what for?

Answer 18

DNA binding site

Question 19

VD3-VDR complex stimulates calcium transporters and bone matrix proteins, what does it suppress?

Answer 19

Synthesis of type I collagen

Question 20

When there is too little calcium, PTH is produced from the parathyroid gland, what 2 things does this have a +ve effect on?

Answer 20

Osteoclast action and conversion of cholecalciferol to calcitriol in the liver

Question 21

Therefore, what is increased by having too little Ca?

Answer 21

Intestinal uptake of Ca (caused by the increase in calcitriol)

Question 22

Too much calcium leads to increased calcitonin release from the thyroid gland. What does CT act +vely and -vely on and what overall effect does this have on Ca?

Answer 22

+vely on osteoblasts, -vely on osteoclasts, reducing blood calcium

Question 23

What is Wolff’s law?

Answer 23

Form follows function

Question 24

What does mechanical strain lead to?

Answer 24

Re-distribution of Ca2+ between blood and bone tissue

Question 25

What 3 things are involved in mechanotransduction in the bone?

Answer 25

Integrins, primary cilium, piezo 1 channels

Question 26

When does a piezo 1 channel open?

Answer 26

When the membrane stretches

Question 27

Osteoporosis means porous bones and is aging related, does this mean there’s more activity of osteoblasts or osteoclasts?

Answer 27

Osteoclasts

Question 28

What is the bone-related disorder that is related to an abnormal growth plate, in what aged people is it typically found?

Answer 28

Children + adolescent

Question 29

When treating bone-related disorders, RANKL is inhibited, what is the natural inhibitor that can be used? This process increases the number of osteoclasts

Answer 29

Osteoprotegerin (OPG)

Question 30

What do semaphorins promote and inhibit?

Answer 30

Promotes diff of mesench SCs to osteoblasts, inhibits diff of haematopoietic SCs to osteoclasts