lecture 28-32: muscular skeletal 1 - bone

Question 1

function of skeletal system

Answer 1

• support
• protection
• movement
• calcium and phosphorus reserve
• haemopoiesis (red marror)
• fat storage (yellow marrow)

Question 2

double meaning of bone

Answer 2

• bone the organ
• bone the connective tissue

Question 3

two main skeletal regions

Answer 3

• axial : skull, rib, spinal column (support+protection+haemopoiesis))
• appendicular: everything else (movement, fat storage)

Question 4

organisation of a long bone

Answer 4

• diaphysis: shaft
• epiphysis: ends often covered with articular cartilage
• metaphysis: transitionary area between epiphysis and diaphysis, separated by epiphyseal line

Question 5

diaphysis stracture

Answer 5

• wall formed by compact bone
• medullary cavity in centre (usually yellow marrow)
• periostium: fibro-cellular sheath surroning bone containing blood vessels and nerves
• perforated (sharpey’s) fibres made of collagen hold periosteum to bone
• endostium: thin inner fibro cellular layer lining cavity

Question 6

epiphysis structure

Answer 6

• thinner compact bone
• spongey bone made of trabeculae covvered in endosteum that grow in response to direction of force
• blood vessels inside compact bone and trabeculae
• small medullary cavity (chance of red marrow)
• no periosteum rather articular cartilage

Question 7

bone as a connective tissue

Answer 7

• fibres (type I and V collagen) to resist stetch/pull tension
• ground substance (hydroxyapatite) to resist compression forces
• cells for various functions

Question 8

bone cell types

Answer 8

• osteocytes: bone maintenance (maintain ECM)
• osteogenic: cell reserve
• osteoblast: bone formation
• osteoclast: bone destruction

Question 9

osteogenic cell

Answer 9

• come from unspecialised stem cells
• located in periosteum and endosteum (also central canals)
• divide and supply developing bone with bone forming cells

Question 10

osteoblasts

Answer 10

• in layer under perio or endosteum or wherever new bone is being formed
• come from osteogenic cells
• sythesise, deposit and calcify osteoid

Question 11

osteoid

Answer 11

organic ECM, mainly collagen
- made by osteoblasts
- infiltrated with bone salts in calcification process that makes bone strong and dense that nutritive fluids don’t diffuse freely through

Question 12

osteocyte

Answer 12

• come from osteoblasts
• trapped within lacunae inside bone
• communicate with neighbouring cells via long extensions in canaliculi
• maintain bone with rapid Ca exchange and localised minor repair.

Question 13

osteoclast

Answer 13

• fusion of multiple monocyte
  WBC progenitor cells (syncytium)
• found at sites of reabsorption
• secrete acid and ezymes to to dissolve bone mineral and organic componants

Question 14

bonegrowth

Answer 14

• appositonal growth to expand bone
• bone reabsorption to expand medullary cavity

Question 15

appositional growth

Answer 15

• chemical signal causes some osteogenic cells to become divide and beocme osteoblasts
• osteoblasts secrete osteoid
• bone grows outwards until chemical tells them to stop
• osteoblasts cells either die or revert to genic

Question 16

reabsorption

Answer 16

• monocyte precursors leave BV and form osteoclasts
• dissolve bone
  -apoptosis (cell death) over time
• blood vessels grow to fill new space overtime

Question 17

endochondral ossification

Answer 17

• epiphyseal plate betwee metaphysis and epiphysis
• chondrocytes grows overtime to expand plate and gap between epi and metaphysis
• cartlage between plate and metaphysis dies and osteoblasts and osteoclasts can move in and do their thing

Question 18

mature/lamellar bone

Answer 18

• spongy or compact
• collagen put down in same direction within a layer (lamellae) but layers can alternate up to 90 degrees so bone can withstand different directional forces

Question 19

spongy bone

Answer 19

• in epiphysis
• unit = trabecula that grow outwards
• support outer crtex of compact bone in areas where there are multidirectional forces

Question 20

compact (cortical) bone

Answer 20

• unit = osteon with haversion canals in the centre fed by volkman’s canals
• found in outer shell and diaphysis of bones
• grow inwards
• prove dense strong shell, thicken in response to high stress areas

Question 21

2 ways that osteons are formed

Answer 21

• primary: osteon built around existing blood vessel
• secondary: osteo formed inside exisitng bone

Question 22

primary osteon bone formation

Answer 22

• tunnel around exterior blood vessel forms as the
• vessel encapsulated because periosteum (now endo) still forms wall.
• circumferential lamellae formed inwards towards blood vessel

Question 23

secondary osteon bone formation

Answer 23

• inside existing bone, initiated by micros-tressors or by osteocyte death from lack of nutrients
• monocyte precurses head to area and form a group of osteoclasts that bore a tunnel through bone
• blood vessel grows into space that bring in osteogenic cells that form bone in towards blood vessel.