Bones 💘 Flashcards
Types of joints and examples
Pivot eg atlantoaxial Hinge eg humerounlar Saddle eg first carpometacarpal Plane eg intertarsal Condyloid eg radiocarpal Ball and socket eg hip
Muscles on back
Llicostalis
Longissimus
Spinalis
Development of skeleton
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
Limb development
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
Osssification from cartilaginous precursor
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
Ossification centres in long bone
Shaft/diaphysis
Epiphysis (near joint)
Separated by a layer of cartilage epiphysial growth plate where lengthening occurs
Cartilage supply and growth
No blood supply
Nourished by diffusion
Interstitial growth when young and apostotial growth when older
Epiphysis
Part of bone nearest to the joint
Physis
Epiphysial growth plate cartilaginous region between bones separates epiphysis from shaft of the bone
Metaphysis
Part of shaft where epiphysis is ossifying (wide part)
Diaphysis
Narrow central core of shaft
Long bone morphology
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
Bone cells
Osteocytes maintain
Osteoblasts which build
Osteoclasts remove and clear bone
Cartilage is chondrocytes/blasts
Osteoblasts
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
Osteoclasts
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
Osteoporosis
Due to desorption and resorption being out of balance causing bone thinning and loss of mechanical integrity
Trabeculae
Types of joint material
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
Rheumatoid arthritis
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
Fracture healing
Haemotoma
Superiosteal and endosteal cell proliferation
Ossifies to form woven bone called callus
Consolidation-woven to lamellar bone
Remodelling
Marrow cavity reforms
Come remodelling functions and components
Mechanical support blood cell production calcium storage
Components are collagen matrix and organic cells
Remodelling
Osteoclasts excavate a cavity within the bone
Osteoblasts produce osteoid and osteoclasts enter programmed cell death
Calcium
Used for muscle contraction nerve conduction and blood clotting
Stored in hydroxyapatite crystals
Promoted by vitamin d
Resorbed In kidneys in response to PTH
Phosphorous
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
Vitamin d
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
1,25 hydroxyvitamin d
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
Parathyroid hormone PTH
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
Calcitonin
Lowers calcium and phosphate levels release from parafollicular cells of thyroid in response to high calcium levels activates calcitonin receptors expressed by osteoclasts
Oestrogen
Maintains bone mass reduces bone resorption by inhibiting osteoclasts lowers serum calcium and phosphate high oestrogen can have anabolic affects
Androgens
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
Osteoporosis
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
Osteomalacia
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
124oh2 formation
Sunlight UVB Vitamin d3 Liver makes it 25OHd3 25ohd1 alpha hydroxylase Kidneys make it 125oh2d3
