Ossification/ fractures/ osteoporosis

Endochondral Ossification

Uses hyaline cartilage as a model for bone formation

Forms all bones inferior to the skull except for the collarbone.

Steps of endochondral ossification

1. Blood vessels invade the perichondrium covering hyaline cartilage model, turning it to periosteum.

2. Osteoblasts at inner surface from periosteum secretes bone matrix around, forming a bone collar.

3. Cartilage in shaft center calcifies and hollows out, forming internal cavity.

4. Periosteal bud invades the cavity and forms spongy bone, which gets removed from osteoclasts, making the medullary cavity. 

Periosteal Bud

Blood vessels, nerves, red marrow elements, osteoblasts, osteoclasts.

Osteoporosis

Gradual loss of bone mass results in weakening of the bone, causing bone to break and fracture more easily.

Causes: hormone deficiency, calcium + vitamin deficiency, physical inactivity.

Comminuted Fractures 

Shatters area into a multitude of bony fragments. 

Transverse Fractures

Breaks a shaft from across its long axis

Spiral Fractures

Produced by twisting stresses that spread along the length of the bone.

Displaced Fractures

Produce new/abnormal bone arrangements. Undisplaced retain normal alignment.

Colles’ fractures

A break in the distal portion of the radius, typically result of reaching out to cushion a fall.

Greenstick fracture

One side of shaft is broken, while other side is bent.

Epiphyseal fractures

Occurs where bone matrix is undergoing calcification and chondrocytes are dying. Fractures can permanently stop growing of the site if not treated correctly.

Compression Fracture 

Occurs in vertebrae subjected to extreme stress; landing on seat in a fall.