Week 1 Bioscience Flashcards
five functions of bone
- Support: Bones provide a framework that supports the entire body
- Protection: Bones surround and enclose body tissues and organs
- Storage of minerals and triglycerides: Bones store minerals (e.g., calcium & phosphate) and triglycerides (fat)
- Blood cell production: Bones produce red blood cells, white blood cells and platelets (haematopoiesis)
- Movement: Bones act as levers to move body parts
THE AXIAL SKELETON
Forms the longitudinal axis of the body and includes the bones of the:
* skull
- cranial and facial bones
* vertebral column
- cervical, thoracic, lumbar, sacral and coccyx vertebrae
* rib cage
- sternum and ribs
THE APPENDICULAR SKELETON
Includes the the bones of the:
* upper limbs - arms, forearms and hands
* lower limbs - thighs, legs and feet
* shoulder (pectoral) girdles
* pelvic girdle
BONE SHAPES
According to their shape bones are classified as:
* long bones
* short bones
* flat bones
* irregular bones
OSSEOUS TISSUE
Is a connective tissue - contains specialised cells and an extracellular matrix (a.k.a. matrix).
The Matrix
* Consists of ground substance, collagen fibres, and calcium phosphate crystals
* Makes bones hard, slightly flexible and strong
- collagen fibres:
→ provide flexibility & tensile strength
- calcium phosphate crystals:
→ make our bones hard & provide compressive strength
Specialised Cells
Osteoprogenitor cells
- stem cells that differentiate into osteoblasts
Osteoblasts
- bone “building” cells - produce & secrete collagen fibres & ground substance (matrix)
Osteoclasts
- bone “resorbing” cells that break down the matrix and release stored minerals
Osteocytes
- mature bone cells that maintain the matrix
Compact Bone
- Osseous tissue is arranged into osteons
- Each osteon:
- runs parallel to the long axis of a bone (e.g., shaft of long bones)
- consists of:
→ a central canal - contains blood vessels & nerves
→ concentric circles (hollow cylinders) of matrix
→ osteocytes - lie in-between each layer of matrix - acts as a tiny weight-bearing pillar → resist forces applied to the ends of a bone
Spongy Bone
- Osseous tissue is arranged into an irregular lattice of thin needle-like structures called trabeculae - trabeculae are precisely orientated to resist forces from all directions and transfer weight without breaking
- Is lighter than compact bone - reduces the weight of the skeleton
In long bones, mainly found the proximal & distal epiphysis
INTERSTITIAL GROWTH
- Occurs at the epiphyseal plates of long bones
APPOSITIONAL GROWTH
Occurs at the outer surface of all bones
REGULATION OF BONE GROWTH
- During childhood bone growth is mainly controlled by growth hormone (GH) and thyroid hormone (TH)
- During adolescence bone growth requires GH, TH, testosterone (males) & estrogen (females)
These hormones:
1. Promote the adolescent growth spurt
2. End growth → induce epiphyseal plate closure
→ the rate of bone formation exceeds the rate of cartilage formation
→ cartilage eventually replaced entirely by bone
→ epiphyseal plate becomes epiphyseal line
BONE REMODELLING
- Occurs throughout life
- Maintains bone mass and strength
- Replaces old matrix with new matrix
- Involves bone resorption and bone deposition
- In healthy young adults the rate of bone deposition equals the rate of resorption → bone mass remains constant
- With age, a decline in sex hormones results in a loss of bone mass as the rate of bone resorption exceeds the rate of bone deposition
- Loss of calcium phosphate crystals & collagen fibres = thin, weak, brittle bones
comminuted fracture
bone fragments into three or more pieces
compression fracture
bone is crushed
greenstick fracture
bone bends and cracks - incomplete break
