MHS Module 4 - supporting ct p5

what does supportive connective tissue include:

include cartilage and bone

explain cartilage:

provides shock absorption and protection

contains matrix of firm gel

what does the matrix of cartilage contain;

contains polysaccharide derivatives called chondrotin sulphates

what are the cells in cartilage matrix called:

are chondrocytes found in chambers called lacunae

what are the 2 structures in cartilage:

avascular and perichondrium

explain the avascular part of cartilage:

all exchange of nutrients and waste products must take place by diffusion through the matrix

chondrocytes produce antiangiogenesis factor that discourages formation of blood vessels

explain the perichondrium part of cartilage:

outer layer, fibrous region of dense irregular connective tissue:

• for mechanical support and protection

inner, cellular layer:

• for growth and maintenance of the cartilage

name the types of cartilage:

hyaline cartilage

elastic cartilage

fibrocartilage

explain hyaline cartilage:

most common type

tough and flexible - reduces friction between bones

found in synovial joints, rib tips, sternum and trachea

explain elastic cartilage:

supportive but bends easily

found in external ear and epiglottis

explain fibrocartilage:

very durable and tough

limits movement and prevents bone to bone contact

found around joints, between pubic bones, and between spinal vertebrae

what is bone:

for weight support

calcified (made rigid by calcium salts)

resists shattering (flexible collagen fibres)

where are osteocytes found:

lie in lacunae

arranged around central canals within matrix

small channels through matrix (canaliculi) allow for exchange of materials with blood

explain the periosteum:

fibrous (outer) and cellular (inner) layers

what are the 4 principal types of bone cells:

osteogenic cells

osteoblasts

osteocytes

osteoclasts

explain osteogenic cells:

stem cells that arise from embryonic mesenchyme

multiply continuously and give rise to most other bone cell types

explain osteoblasts:

bone-forming cells

form single layer of endosperm and periosteum - are non-mitotic

synthesise soft organic matter of matrix

what does stress stimulate:

stress stimulates osteogenic cells to multiply and increase number of osteoblasts - reinforces bone

what do osteoblasts secrete

osteocalcin

what are osteocytes:

former osteoblasts

reside in small cavities in lacunae

cytoplasmic processes extend into canalculi and contact processes of other osteocytes

what do osteocytes act as:

strain sensors - bone produces biochemical signals that regulate bone remodelling (shape and density changes that are adaptive)

explain osteoclasts:

cells that absorb and remove bone matrix

large cells formed by fusion of several stem cells - multiple nuclei in each cell

ruffled border (increase the surface area of cell) in contact with bone matrix

often reside in resorption bays (pits in bone surface)

dissolving bone is part of bone remodelling

what is bone structure composed of:

1/3 organic & 2/3 inorganic matter

explain the organic matter:

synthesised by osteoblasts

collagen, carbohydrate-protein complexes:

• glycosaminoglycans, proteoglycans and glycoproteins

inorganic matter:

• 85% hydroxyapatite

• 10% calcium carbonate

what type of material is bone

composite

what does the collagen portion of bone ensure:

gives flexibility what does the

what does the hydroxyapatite portion of bone ensure:

allows bone to support body weight without sagging

what is spongy bone:

lattice of bone covered with endosteum

slivers of bone called spicules

meshwork of supporting bundles of fibres called trabeculae - thin plates of bone

few osteons and no central canals

provides strength with minimal weight

explain the spaces in between the meshwork in spongy bone:

spaces filled with bone marrow: forms blood cells

where Is trabeculae formed:

developed along stress lines

define ossification/osteogenesis:

the formation of bone

what are 2 bone development methods:

intramembraneous ossification

endochondral ossification

explain intermembraneous ossification:

occurs within membrane

produces flat bones of skull and clavicle in foetus

thickens long bones throughout life

explain endochodral ossification:

occurs within cartilage

produces all other bones

name the processes of bone remodelling;

absorption and deposition

occurs throughout life

what does bone remodelling do?

repairs microfractures, releases minerals into blood, reshapes bones in response to use and diffuse

what is Wolffs law of bone:

architecture of bone determined by mechanical stresses placed on it

which bone cells do remodelling?

osteoblasts and osteoclasts

what is a mature bone?

a metabolically active organ

what is mature bone function?

involved in own maintenance of growth and remodelling

exerts influence over body by exchanging materials with tissue fluid