The Skeletal System

Question 1

Name the classifications of bones based on their gross anatomy?

Answer 1

1) Long bones = longer than than their width, wider at the ends. All limb bones are long e.g. Humerus
2) Short bones = cube shaped and small. e.g. wrist or ankle bones
3) Flat bone = elongated and flattened, thin and curved. e.g. scapula, ribs, sternum.
4) Irregular bone = have an irregular shape, vary in shape. e.g. vertebrae, hipbones

Question 2

What are the anatomical parts of long bones?

Answer 2

• Diaphysis = is the shaft, forms the long axis of the bone
• Epiphyses = bone ends, more expanded than diaphysis. Joint side covered in articular
  hyaline cartilage.
• Membranes = external surface of entire bone covered and protected by membrane called periosteum (double layer membrane)

Question 3

Name and describe the two types of bone development?

Answer 3

1) Endochondral ossification =

• bone collar forms around a hyaline cartilage model
• cartilage begins to ossify and cavities form
• periosteal bud invades the diaphyses and spongey bone forms.
• diaphyses elongate while marrow cavity forms internally to the diaphysis. Secondary ossification centers form at the epiphyses.
• epiphyses ossify but the epiphyseal plates remain hyaline cartilage at the articular surfaces.

2) Intramembranous ossification =

• Ossification centres form from centrally located mesenchymal cells, cells differentiate into osteoblasts.
• Osteoblast secret osteoid and those trapped within the osteoid become osteoclasts.
• Osteoblast continue to secrete osteoid in and around the blood vessels in the connective tissue, forming woven like trabuculae.
• Vascularized mesenchymal cell condense at the surface, forming the periosteum
• Lamellar deep below the periosteum forms from the spongey tissue and more internally, the spongey bone remains and its vascularized tissue becomes red marrow.