Question

Answers in complete sentences!

-Describe endochondral ossification from Mesenchyme to complete formation of bone, make sure to first discuss the formation of the hyaline cartilage model.

- Describe intramembraneous ossification from Mesenchyme to complete formation of bone.

- Differences between male and female skeleton; include characteristic and a description of how the characteristics are different (this could be about the general skeleton or about the pelvis since we went into lots of detail there)

-Differences between the adult skull and the fetal skull

Answer 1

There are two methods of bone formation in mammals

• Endochondral bone formation
• Intramembranous bone formation

1. Endochondral bone formation- initially a cartilaginous structure is laid down by numerous multiplying chondrocytes. A rudimentary hyaline cartilage structure is formed and the primary center of ossification is activated. All the bones have different primary center of ossification. For long bones it lies at the middle of diaphysis.

The perichondrium of cartilage converts into periosteum. And it's osteoprogenitor cells differentiate into osteoblasts and lay down bone matrix(osteoid) against the cartilage. Later, the cartilage model also ossifies.

2. Intramembranous bone formation- it is an essential process involving the formation of rudimentary head and neck skeleton.

The mesenchymal stem cells from the medullary cavity replicate in a small area in dense number and form a nidus. After this the MSC stop replicating and differentiate into osteoprogenitor cells. The number of rough endoplasmic reticulum and golgi bura increase and they convert into osteoclasts.

Osteoblast lay down the woven bone and get trapped in the bone laid by them. The inter trabecular network is laid down. And the woven bone later ossifies

3.

• The skull and jaws are larger in males
• Female thorax is narrower.
• Female pelvis is broader
• Oblique slant of femur is more pronounced in females.
• Arms are longer in males
• Male shoulders are wider and higher

4. Facial bones form a larger portion of face in fetal life because the brain is not completely developed.

The para asal sinuses in fetus are not developed at all.

Fetal skull does not have mastoid or styloid process

Fetal skull has fontenalles which ossify later in life