connective tissue 4

what are the functions of the skeletal system

1. support

2. storage of minerals and lipids

3. blood cell production

4. protection

5. leverage

bone

rigid supporting structure due to the calcified
matrix (made rigid by calcium salts, minerals)
◦ For weight support
◦ Dense mineralized matrix
◦ Surrounded by periosteum

function of bone structure

Strong (calcified: calcium salt deposits)
Resists shattering (flexible collagen fibers)
Combination of collagen and mineralized
matrix gives bone its hard but flexible
properties
Bone is highly vascular (well supplied with
blood vessels)

the matrix in relation to bone structure

• contains bone cells (osteocytes) within pockets
  called lacunae

• canaliculi are narrow passages through the matrix extend between the lacunae and blood vessels → exchange nutrients, waste, gases

• Except at joints, a periosteum (with an outer fibrous and
  inner cellular layer) covers the outer surfaces of bones

  
  

what are the 4 bone types

1.Osteocytes found in lacunae (depend on diffusion through
canaliculi for nutrients)
2.Osteoblasts (involved in bone growth and repair)
3.Osteoprogenitor stem cells
4.Osteoclasts (involved in bone remodeling)

matrix minerals

• two thirds of matrix is calcium phosphate Ca3(PO4)2

• ◦ Reacts with calcium hydroxide, Ca(OH)2
  ◦ To form crystals of hydroxyapatite, Ca10(PO4)6(OH)2
  ◦ Which incorporates other calcium salts and ions

matrix proteins

One third of bone matrix ( collagen)

outer bone structure - periosteum

• surrounds bone

• like perichondrium ( has fibrous and cellular layer) and attaches bone to surrounding structures tendons and ligaments.

function of bone cells

Osteocyte
◦ Mature bone cells
◦ Maintain protein & mineral content of the surrounding matrix
Osteoblast (build)
◦ Produce new bone matrix
Osteoclast (cut)
◦ Remove & recycle bone matrix
Osteoprogenitor cell
◦ Stem cells that divide and produce new osteoblasts

structure of a long bone (3)

1. diaphysis

2. epiphysis

3. metaphysis

diaphysis

◦ The shaft
◦ A heavy wall of compact bone, or dense bone
◦ A central space called medullary (marrow) cavit

epiphysis

◦ Wide part at each end
◦ Articulation with other bones
◦ Mostly spongy (cancellous) bone
◦ Covered with compact bone (cortex))

Metaphysis

where diaphysis and epiphysis meet

structure of flat bone

The parietal bone of the skull
Resembles a sandwich of spongy
bone
Between two layers of compact
bone
Within the cranium, the layer of
spongy bone between the
compact bone is called the diploë

blood supply of mature bones

1. Nutrient artery and vein:
◦ a pair of large blood vessels (maybe 2)
◦ enter the diaphysis through the nutrient
foramen
2. Metaphyseal vessels:
◦ supply the epiphyseal cartilage (for bone
formation)
3. Periosteal vessels:
◦ blood to superficial osteons
◦ secondary ossification centers

what are the 2 types of bone tissues

1.Compact bone
Compact bone found to outside of the
long bone and especially along shaft region
2.Spongy (cancellous) bone
Cancellous/spongy bone found inside,
especially at two ends of bone

1. compact bone

A solid outer layer of bone
Divided into units called Haversian
systems/osteons
Layers of matrix surround blood vessels
Cells in the matrix, occupy lacunae
Lacunae joined to each other by canaliculi
Function of compact bone is to withstand
pressure, usually in 1 direction
directions

2. spongy bone

Found in the centre of bones
A network of interconnected bone
spicules or trabeculae
Similar to Haversian systems, with
lacunae and canaliculi
Forms an open framework that is filled
with marrow
Function is to withstand
multidirectional stress and to
reduce the weight of bone

Bone formation/ossification

Skull and clavicles = intramembranous ossification
Rest of skeleton = endochondral ossification

osteoporosis

abnormal progression of osteopaenia resulting in low bone mineral mass and dysfunction

bone loss - calcium balance

Calcium stores in bones are
regulated by 2 hormones
◦ One promotes retention of bone Ca2+
(calcitonin) and the other
promotes removal of Ca2+ from bone
(Parathyroid hormone (PTH))
Imbalances may deplete Ca2+ and
lead to weakness and ease of
fracture
NB decline after age 30 and
accelerated in women after
menopause