Physiology of Bones

1
Physiology of Bones

• What are the functions of bone?

• Protection- CNS, heart and lungs, urogenital
  tract
• Giving rigidity and form- without no form
  jellyfish
• Levers- muscles are attached to levers
• Storing minerals
• Providing
• site for blood formation

2
Terminology

• Diaphysis-shaft of a long bone situated between
  two epiphysis
• Epiphysial cartilage- cartilage that seperates
  diaphysis and epiphysis with metaphysis
• Metaphysis- flared area adjacent to the epiphysis
• Articular cartilage- thin layer of cartilage that
  covers articular surface

3

• Periosteum- responsible for increases in bone
  diamater. Functions in healing
• endosteum- fibrous membrane that lines marrow
  cavity.

4
Terminology contd

• Osteocytes-bone cells
• Osteoid material- cement that holds cells
  together
• Lacunae( little lake)
• Osteoblasts- form lacunae, canaliculi,
  osteocytes. Secrete phosphotase- causes ca2
  salts to be deposited forming bone

5

• Osteoblasts derived from mesenchymal cells. Only
  part cells secrete. Others held in reserve.
• Osteoclasts- involved in bone resorption.
  Secrete enzyme which degrades bone.

6
How do bones grow?

• Bones grow like trees, at the ends. A typical
  long bone ossifies (hardens to bone) at the
  center first, then towards each end. Each bone
  will ossify at different ages.
• Therefore young animals will have incomplete
  ossification of some of their long bones.
• In colts, we can x-ray their radius and determine
  whether they are suited for racing.

7

• Horses where ossification occurs to the epiphysis
  are mature (their knees are closed) whereas
  horses with incomplete ossification are not
  mature ( their knees are open).
• Sheep carcasses are aged based on this
  fact---break jointyoung lamb, no break
  jointmutton.

8
How do bones heal?

• Blood vessels are ruptured, releasing blood
  around broken ends of t he bone. Connective
  tissue forms granulation new blood capillaries.
• Osteoblasts from surface of bone, periosteum, and
  endosteum divide and produce callus which fills
  gap.
• Callus becomes mineralized.
• Reorganization into bone shaft with marrow
  cavity.
• Osteoclasts and osteocytes remove misalignment.

9
Fractures

• A break in continuity
• Simple- skin unbroken
• Compound- wound from the exterior contacts the
  bone ( broken through skin)
• Greenstick fracture- side of the bone is broken
  and the other side is bent
• Complete fracture bone broken entirely across
• Epiphysial fracture- break at junction of
  epiphysis and diaphysis-limited to young animals

10
What are types of bone?

• Short
• Long
• Flat Sesamoid
• Pneumatic
• Irregular

11
Makeup of bone

• 80 CaPO4, Ca C03, MgPO4
• Bone is dynamic, not static. Bone minerals are
  constantly being replaced by new mineral deposits
  and are being utilized for such things as nerve
  function and muscle contraction. Bones are
  storehouses for these minerals.

12
Pathologies of bone

• Tuberculosis-inflamation of bone
• Osteomyelitis-inflamation of bone marrow which is
  caused by bacteria
• Osteoma- response to irritation
• Chondroma-develop due to unabsorbed cartilage
• Osteoclastoma-giant cell tumor
• Rickets- lack of vit. D synthesis