Principles Of Skeletal System

Question 1

When does Bone Development start in Embryo, and when does it end after being born?

What is the process called? (3)

Answer 1

Start - 8 weeks; Ends - 20 years

Process is Ossification

Question 2

What 2 ways can Ossification occur?

Answer 2

• Intramembranous

- Endochondral

Question 3

How does Intramembranous Ossification Occur? (4)

What bones are formed this way?

Answer 3

• Mineralisation of Mesenchyme (embryonic connective tissue)
• Cells divide and condense around capillary network. This starts at Primary ossification centre, grows rapidly and fuse together to form connective tissue.
• Undifferentiated mesenchyme becomes bone marrow
• Skull, mandible and clavicle

Question 4

How does Endochondral Ossification occur? (4)

Answer 4

In order of events in growth:

• Through Osteogenesis (using cartilaginous template from mesenchyme) from Hyaline Cartilage.
• Primary ossification centre develops inside bone where cells grow around capillary bed.
• Blood vessels penetrate and grow inside bone. This forms Periosteum (outside layer) and Medullary cavity (vascularised inside of bone)
• The Secondary ossification develops in Spongy bone layer and is pierced by blood vessels.

Question 5

What happens to Parts of child’s bone as growth occurs? (2)

Answer 5

• Long bones lengthen

- Growth plates (epiphyseal plate) shorten and eventually disappear when fully grown

Question 6

What are the 4 cells Bone is comprised of? (4)

Answer 6

• Osteoprogenitor cells
• Osteoblasts
• Osteocytes
• Osteoclasts

Question 7

What 2 cells are involved in bone remodelling? (1)

Answer 7

Osteoblasts and osteoclasts

Question 8

What nutrients are necessary for bone development and maintenance? (5)

Answer 8

• Calcium
• Phosphorus
• Vitamin A - for bone remodelling
• Vitamin C - for connective tissue
• Vitamin D - for Calcium reabsorption

Question 9

What hormones regulates is Bone development. If it goes wrong what happens?

Answer 9

Controlled by Endocrine activity.
- Parathyroid hormone (calcium regulation)

If too much produced leads to Hyperparathyroidism.

• Growth Hormone

If too much causes Gigantism/Acremagly
/too little produced can cause Restricted growth

Question 10

What is connective tissue surrounding bones?

What is connective tissue covering articulation points?

Answer 10

• Periosteum

- Perichondrium

Question 11

What are parts of the Compact bone when viewed transversely? (4)

Answer 11

• The lamellae concentric rings laid down by osteoblasts
• Osteocytes (differentiated osteoblasts)
• HAVERSIAN CANAL - contains neurovascular supply
• Canaliculi - paths in lamallae rings for nutrients to travel to osteocytes

Question 12

Describe the Spongy bone (aka Trabecular bone, Cancellous bone) (3)

Answer 12

• They are highly vascularised
• Surrounded by Red Marrow
• Have irregular bony plates called TRABECULAE

Question 13

What are the classifications of bones? (5)

Answer 13

Long bones
Short bones
Flat bones
Sesamoid bones
Irregular bones

Question 14

What are the types of joints in the body with 2 examples each (3)

Answer 14

1. Synovial Joints - they permit movement as have joint capsule and synovial cavity e.g Knee, Hip
2. Fibrous Joints - They are connected by collagen and do not permit movement e.g Sutures of skull
3. Cartilaginous joints - Connected by cartilage to allow movement e.g Intervertebral disc, growth playes