Bones 💘

Question 1

Types of joints and examples

Answer 1

Pivot eg atlantoaxial
Hinge eg humerounlar 
Saddle eg first carpometacarpal 
Plane eg intertarsal
Condyloid eg radiocarpal
Ball and socket eg hip

Question 2

Muscles on back

Answer 2

Llicostalis
Longissimus
Spinalis

Question 3

Development of skeleton

Answer 3

Around 21-25 days there’s a zipping up of embryo creating an enclosed neural tube
Paired somites at each side of zip
Near ectoderm and neural tube there is neural crest cells which migrate from origin and spread out across entire body to form a diversity of different tissues
Rest of bones formed from mesoderm which becomes somites HOX genes specify identity of the vertebra

Question 4

Limb development

Answer 4

Limb bud develops at 4-5 weeks
Most distal part of limb bud is apical ectodermal ridge which it cells release signals which help with patterning and interacting with signals from some of polarising activity
Zones determine segments and appropriate cartilaginous precursors for the bones

Question 5

Osssification from cartilaginous precursor

Answer 5

Endochondral ossification
Cartilage grows and expands in all directions esp in young cartilage older ones only on outside
Chondrocytes need nutrients when cartilage gets to certain size so blood cells invade
Calcification of cartilage which ossifies and becomes bone

Question 6

Ossification centres in long bone

Answer 6

Shaft/diaphysis
Epiphysis (near joint)
Separated by a layer of cartilage epiphysial growth plate where lengthening occurs

Question 7

Cartilage supply and growth

Answer 7

No blood supply
Nourished by diffusion
Interstitial growth when young and apostotial growth when older

Question 8

Epiphysis

Answer 8

Part of bone nearest to the joint

Question 9

Physis

Answer 9

Epiphysial growth plate cartilaginous region between bones separates epiphysis from shaft of the bone

Question 10

Metaphysis

Answer 10

Part of shaft where epiphysis is ossifying (wide part)

Question 11

Diaphysis

Answer 11

Narrow central core of shaft

Question 12

Long bone morphology

Answer 12

Compact and cancellous (trabecular) have outside rings called circumferential lamellar and smaller rings called osteon which have blood vessels in its central canal
Primary bone is woven and collagen fibres random then replaced by lamellar bone so fibres more parallel and in layers

Question 13

Bone cells

Answer 13

Osteocytes maintain
Osteoblasts which build
Osteoclasts remove and clear bone
Cartilage is chondrocytes/blasts

Question 14

Osteoblasts

Answer 14

Derived from mesenchyme and secrete organic matrix (osteoid) of bone and mineralise
Have processes which lay down ground substances and connect and communicate with other cells
once they become entombed by the processes they become osteocytes

Question 15

Osteoclasts

Answer 15

Derived from precursor cells in blood
Dissolve bone with HCL
Pack organic and mineral debris into vesicles which pass through osteoclasts cell body into space above

Question 16

Osteoporosis

Answer 16

Due to desorption and resorption being out of balance causing bone thinning and loss of mechanical integrity
Trabeculae

Question 17

Types of joint material

Answer 17

Fibrous joints syanthroses
Synovial joints diathroses
Cartilaginous joints ampiarthrosis
Synovial membrane is thin sheet of connective tissue which secretes synovial fluid for lubrication. Only joint with a cavity

Question 18

Rheumatoid arthritis

Answer 18

Synovial membrane being inflamed due to autoimmune disease

Osteoarthritis is articulate cartilage breaking down due to injury disease or age most common in highly used joints

Question 19

Fracture healing

Answer 19

Haemotoma
Superiosteal and endosteal cell proliferation
Ossifies to form woven bone called callus
Consolidation-woven to lamellar bone
Remodelling
Marrow cavity reforms

Question 20

Come remodelling functions and components

Answer 20

Mechanical support blood cell production calcium storage

Components are collagen matrix and organic cells

Question 21

Remodelling

Answer 21

Osteoclasts excavate a cavity within the bone

Osteoblasts produce osteoid and osteoclasts enter programmed cell death

Question 22

Calcium

Answer 22

Used for muscle contraction nerve conduction and blood clotting
Stored in hydroxyapatite crystals
Promoted by vitamin d
Resorbed In kidneys in response to PTH

Question 23

Phosphorous

Answer 23

Used in metabolic processes as ATP
85% in bone as hydroxyapatite crystals Absorbed in gut in response to vitamin d
excreted by kidneys in response to PTH

Question 24

Vitamin d

Answer 24

Vitamin D3 synthesised from skin or absorbed in gut along with d2 D3 and D2 undergo hydroxylation in liver producing 25 hydroxyvitamind the final hydroxylation and activation occur in kidneys catalysed by PTH resulting in formation of 125 hydroxyvitamin d

Question 25

1,25 hydroxyvitamin d

Answer 25

Increases serum calcium and phosphate and the absorption from intestine mobilises calcium and phosphate from bone induces bone marrow monocytes to become osteoclast causing Resorption

Question 26

Parathyroid hormone PTH

Answer 26

Secreted by PT glands in neck in response to low calcium levels in Serum stimulates osteoclastic bone resorption and mobilising CA from bone activates inactive vitamin D via hydroxylation in kidneys decreases renal calcium excretion increases renal production of 1250H2 vitamin D3 increases calcium and phosphate absorption in intestine via 1250H2 vitamin d3

Question 27

Calcitonin

Answer 27

Lowers calcium and phosphate levels release from parafollicular cells of thyroid in response to high calcium levels activates calcitonin receptors expressed by osteoclasts

Question 28

Oestrogen

Answer 28

Maintains bone mass reduces bone resorption by inhibiting osteoclasts lowers serum calcium and phosphate high oestrogen can have anabolic affects

Question 29

Androgens

Answer 29

Sex hormones such as testosterone decrease androgen link to lower bone density in man decreases bone resorption by targeting osteoclasts androgen supplements increase bone density

Question 30

Osteoporosis

Answer 30

Reduced bone density increasing risk of fracture postmenopausal women most affected risk factors include age female early menopause hypothyroidism low BMI asymptomatic or routine DEXA scan do weight bearing exercise to prevent

Question 31

Osteomalacia

Answer 31

Due to failure of bone mineralisation cause structural change in bone matrix affects 50% in adults due to inadequate diet lack of sunlight malabsorption liver and kidney problems causes bone and muscle pain paraesthesia weakness or a symptomatic can be prevented by supplement sun and education treated with vitamin d supplements and a blood test is used to diagnose

Question 32

124oh2 formation

Answer 32

``` Sunlight UVB Vitamin d3 Liver makes it 25OHd3 25ohd1 alpha hydroxylase Kidneys make it 125oh2d3 ```