Lecture 3

Question 1

Mechanobiology

Answer 1

Where biology meets physics. Our biological response to physical forces. Multi-scale from organism level to subcellular molecular signalling. Strain can be sensed through cell. Mechano-sensores, fluid flow, compression of extracellular matrix and excitation signals. Determines shapes of bones

Question 2

Long bone structure

Answer 2

Epiphyses ossify in post-natal development. Post natal limbs grow until cessation of growth at 13-18yrs though growth plates close at puberty.

Question 3

Aticular joint cartilage

Answer 3

Articular/hyaline cartilage in joints is permanent cartilage and remains to adulthood. Thickens as bone grow in response to hormones. Post natal changes in the joint lead to it increasing thickness and aquiring distinct zonal organisation. Thickness which increases with chondrocyte volume and accumulation of extracellular matrix. 30% population has MSK condition.

Question 4

Post-natal muscle development

Answer 4

embryonic development determines number of muscle fibres in each muscle. Post natal muscle growth primarily involves increasing volume muscle fibres (hypertrophy). involves increasing nuclei to growing muscle cells to keep the nuclei/cytoplasmic volume ratio balanced. New nuclei are incorporated with muscle satellite cells

Question 5

How loada are dealt with

Answer 5

1. Bone matrix is designed to withstand load
2. Articular joint cartilage is mostly extracellular matrix. Collagen and proteoglycan aggregates in ECM and interstitual fluid provides resiliance to load. Moderate physical loading is required for cartilage maintainence, atrophy if unloaded chronically. Exercise increases chondrocyte production of ECM glycosaminoglycans and decrease matrix degrading enzymes. Excessive loadong (trauma) or aging can cause long term joint damage
3. Muscles are mostly muscle fibres. They grow in volume, new nuclei are recruited prolonged disuse can lead to sarcopenia

Question 6

MSK lifespan

Answer 6

muscle mass increases through development and peaks at 25-30yrs. 40-70 yrs 8% muscle loss a year increases to 15% after 70

Question 7

testosterone

Answer 7

promotes muscle protein sunthesis and decreases muscle protein breakdown, increases bone mass

Question 8

Estrogen

Answer 8

in women, increase bone formation and mass, anti-inflammatory properties to protect joints increase muscle mass

Question 9

Progesterone

Answer 9

in women, works synergistically with estrogen to promote bone formation and mass

Question 10

Growth hormone

Answer 10

Stimulates muscle growth by increasing protein synthesis and insulin-like growth factor I release

Question 11

IGF-1

Answer 11

Works with GH to promote muscle cell growht and differentiation, enhances protein synthesis

Question 12

Cortisol

Answer 12

In excess/prolonged secretion, degrades muscle proteins to a.a, decreasing bone mass, drives inflammation in joints

Question 13

progesterone

Answer 13

can counteract estrogen’s effect. Not clear

Question 14

menopause

Answer 14

Decrease in estrogen can cause changes in bone mass and joints. Females experience a steeper decline in bone mass around/after age of menopause (hence, prevalence of bone disease in 50yr women) and steep increase in incidence of joint arthritis around/at age of menopause. Females also have lower peak in muscle strength than males which declines faster too. Increases joint pain.