BSC2085 Feb 13

Connective tissue originates from mesenchymal cells, which are embryonic stem cells.
Bone formation occurs via two key processes:
- Intramembranous ossification: Involves direct transformation of mesenchyme into bone.
- Endochondral ossification: Involves the formation of cartilage that is later replaced by bone.
Regardless of the method, all bones originate from mesenchyme during embryonic development.

Bone Growth:
- Bones grow from embryonic stages into adulthood through endochondral ossification.
Structure of Bone:
- Compact bone: Dense outer layer.
- Trabecular bone: Lattice structure inside compact bone, important for strength and support.
Remodeling: Like other somatic tissues, bone undergoes constant remodeling throughout life.

Diaphysis: The shaft of the long bone that calcifies during growth.
Epiphysis: The end part of a long bone, separated by the epiphyseal plate.
Metaphysis: The area between the diaphysis and epiphysis containing the epiphyseal plate.
- The epiphyseal plate is a crucial zone for ossification, leading to bone lengthening.
Chondrocytes: Cells responsible for cartilage formation that multiply and contribute to growth.
Growth occurs from the epiphysis towards the diaphysis, contrasting with skin growth that occurs outward.

Long bones and vertebrae are principal components of the axial skeleton.
Osteopenia and osteoporosis are conditions related to decreased bone density, leading to an increased risk of fractures.

Estrogen Replacement Therapy: Used for managing osteoporosis but carries risks like cancer and heart disease (including stroke).
Increase in osteoblast activity can be stimulated through weight-bearing exercises, which is encouraged for bone health.

Impacted Fractures: Commonly occur in elderly individuals with osteoporosis, frequently resulting from falls.
- Example: Elderly women with small pets may get impacted fractures when tripping.
Low calcium levels trigger parathyroid hormone (PTH), leading to bone breakdown and increased calcium levels in the blood.
Greenstick Fractures: Incomplete fractures mostly seen in children, characterized by bending without complete breakage.
- Common sites: Clavicle and radius are among the most frequently fractured.

Compression Fractures: Often occur in the vertebrae and can lead to a wedge-shaped appearance on X-ray.
- Burst Fractures: A severe type of compression fracture usually resulting from significant trauma.
Hangman's Fracture: A specific injury to the cervical spine, resulting from hyperextension of the neck, requiring careful assessment.