bones Flashcards
how long does it take for all bone in the body to be replaced
10 years
what part of the body do bones NOT protect
the gut
what is haematopoiesis
the process of blood cell formation in bone marrow
what are the 2 main components of bone
collagen (gives the bone tensile strength
calcium phosphate crystals (mineral) to harden the bone and give it compressional strength
what is cartilage
similar to bone but no calcified
3 things bone is made from
osteoblasts, osteocytes and osteoclasts
what is bone supplied by
blood vessels and nerves
what is the head of a long bone called
epiphysis (head) spongy bone, covered by hyaline cartilage
what is the shaft of a long bone called
diaphysis- hollow cylinder which contains bone marrow in marrow cavity
what is the periosteum
fibrous connective tissue sheath covering external surfaces.
contains fibroblasts, mesenchymal cells and osteoclasts
fibroblast
in the periosteum of long bone that can synthesize collagen
what can mesenchymal cells differentiate into
osteoblasts and chondroblasts
2 different kinds of bone
trabecular/ cancellous (spongy- in areas of stress)
cortical (solid- stiffness and strength)
how are trabecular bones good for areas of stress
high surface area for metabolism
goes horizontal and vertical for more strength
haversian canal
carry blood along the axis of the bone in cancellous bones
volkmans canal
carries blood perpendicularly across the bone in cancellous bones
what is cortical bone
arranged in concentric circles (onion).
each layer contains collagen fibres which are flexible and orientated differently
haversian canals
carry blood along cortical bones
what is the organic matrix composed of
mostly protein fibres but also crystalllised mineral salts and water
what is rickets
Vit D deficiency, failure of Ca2+ absorption
what is scurvy
Vit C deficiency- lack of collagen
osteoblast
bone forming cell, covering surface of bone
when stimulated to form bone it will deposit collagen and hydroxyapatite
osteoclast
form seal on bone, reabsorb bone matrix by demineralization if there is mechanical stress or physiological demands
suck on bone and dissolve structure
osteocyte
mature bone cell. maintain bone matrix by cell to cell communication (finger like structures
osteoprogenitor cells
stem cell population
hypertrophy
less bone formation than bone reabsorption so osteoclasts are more active
atrophy
more bone formation that bone reabsorption so osteoblasts are more active
4 steps of bone remodelling cycle
- osteoprogenators differentiate into osteoblasts
- osteoblasts lay down new bone
- cells become deactive
- reabsorption by osteoclasts
wolff’s law
bone adapts to the load under which it is placed, ‘use it or lose it’ (ex. astronauts)
what is ossification
when the original cartilage is coverted into bone in the fetus
what is the epiphyseal plate
plate of cartilage in between the head (epiphysis) and the shaft (diaphysis) of the long bone to allow the bone to grow. this gets smaller until the bone is at full length and it dissapears
