Biology 6.4 - Bone Development

made by me, September 25th, 2026

What processes does bone formation in fetuses follow?

Intramembranous Ossification & Endochondral Ossification

What does intramembranous ossification start within?

Embryonic connective tissue membranes

What does Endochondral Ossification start with?

A cartilage model

What bones develop via intramembranous ossification?

The diaphyses of the clavicles, parts of the mandible, & many of the skull bones

What are the centers where intramembranous ossification begin at called?

Centers of Ossification

In intramembranous ossification, which parts have the oldest bone?

The centers

In intramembranous ossification, which parts have the youngest bone?

The expanding edges

What are the soft spots, aka, the large membrane-covered spaces in between developing skull bones (not yet ossified)?

Fontanels

At what age do the fontanels close up by?

2 years old

What is the end formation of intramembranous bone formation?

Bones with outside compact bone and inside spongy bone centers

What is Endochondral Ossification?

The ossification of cartilage

What bones develop via Endochondral Ossification?

Base of the skull bones, parts of the mandible, epiphyses of clavicles, and most of the skeletal system

Cartilage model

Cartilage that has the shape of the bone, a template