Bones

• –Disease that occurs
• when lymphocytes produce BMP-4 protein

• •This is a protein
• that triggers bone formation

Stress/force :

• –1-physical action of
• muscles pulling on bones stimulates osteoblasts-building bone

–2- release of calcitonin which inhibits osteoclast activity

• 1. Long bones - femur
• 2. Short bones - carpals & tarsals
• 3. Irregular - vertebrae - sacrum
• 4. Flat - scapula
• 5. Sesmoid - patella

• 1. Compact bone - 80%
• 2. Spongy bone - short, flat, irregular bones - epiphysis of long bones

• 1. Sheets of messenchyme tissue - osteoblasts form and start making bone tissue, they group together to secrete bone matrix.
• 2. Ca+ is deposited into the matrix and calcification begins - forming spikes called trabiculae.
• 3. The trapped osteoblasts become osteocytes
• 4. Trabeculae fuse together to become spongy bone.

Flat bones, facial bones, sternum are made this way.

• 1. Messenchyme cells gather in shape of future bone
• 2. Chondroblasts - move into the messenchyme & begin forming cartilage in the shape of the future bone
• 3. Starts in diaphysis - chondrocytes grow and burst changing the pH of matrix - which begins to harden - forming bone.
• 4. As cartilage disintegrates bone is formed solid so osteoclasts move in to hollow out the center
• 5. At the same time the outer edge of bone model - osteoblasts are forming bone
• 6. In the epiphysis - osteoblasts invade cartilage on the end and begin forming trabeculae which forms spongy bone.

too much osteoclast activity

• Calcitonin (CTH) increases osteoblast activity and inhibits osteoclast activity - PTH is inhibited
• Ca++ is deposited into skeletal system

Thyroid secretes Parathyroid Hormone (PTH) increasing osteoclasts - ultimately increasing Ca++ in ECF

Hypothalamus-releases:

• Growth Hormone Releasing Hormone (GHRH) to the:

• anterior pituitary-which releases:

• GH-growth hormone

•The level of growth hormone can result in disease.

• Pre-growth plate closure

• –Dec GH=Dwarfism
• –Inc GH=Gigantism

• • Post growth plate closure
• Inc GH=Acromegaly