Chapter 6 Section 6-8: Bone Remodeling

How often does the skeleton get replaced?

About every ten years

Does bone resorption happen in the periosteum or endosteum?

Endosteum

Does bone deposition happen in the periosteum or endosteum?

Periosteum

How do osteoclasts break down bones?

By secreting acid out of one side of their membrane that dissolves the bone matrix and released out of the back side of the osteoclast into the interstitial fluid

What acid do osteoclasts secrete to digest the bone matrix?

Lysosomal enzymes

What happens to the osteoclast when reabsorption is finished?

It undergoes apoptosis

What hormone and proteins does osteoclasts activation involve?

Parathyroid hormone and immune T cell proteins

What is an osteoid seam?

Unmineralized band of gauzy bone about 10-12 micrometers wide

What two control loops regulate bone remodeling?

Hormonal controls and response to mechanical stress?

What does parathyroid hormone do?

Stimulates the osteoclasts to resorb bone to increase calcium in blood

What does calcitonin do?

Stimulate the osteoblasts to produce matrix to lower calcium in blood

Is the release of parathyroid and calcitonin negative or positive control loop?

Negative

What functions does calcium serve in the body?

Nerve transmission, muscle contraction, blood coagulation, nerve secretions, and cell divisionq

What vitamin does intestinal absorption of calcium require?

Vitamin D

What is Wolff’s Law?

Bones will grow features in areas where the muscles are pulling on the bones; “Bone adapts to the load it experiences”

What does hypocalcemia cause?

Hyperexcitability

What does hypercalcemia cause?

Non-responsiveness

Where are curved bones thickest at?

Where they are most likely to buckle

Give an example of a cranial projection that is not present on infants but is present on normal adults

Mastoid process

What are the three fracture classifications?

Position of bone ends after fracture

Completeness of break

Penetration of skin

What is displaced and non-displaced fracture?

Displaced: Bone ends are out of normal alignment

Nondisplaced: Bone ends retain normal position

What is a complete or incomplete break?

Complete: Broken all the way through

Incomplete: Not broken through

What is compound or simple fracture?

Compound: Skin is penetrated 

Simple: Skin is not penetrated

What is a closed and open reduction?

Closed reduction: Physician manipulates bone to correct position

Open reduction: Surgical pins or wires secure ends

What are the three major bone diseases?

Osteomalacia, osteoporosis, and Paget’s Disease

What is osteomalacia?

When your bones are poorly mineralized, and osteoid is produced but calcium salts are not adequately deposited

Results in soft bones

What is osteomalacia in children called?

Ricket’s Disease

What are the four stages of bones repair?

Hematoma formation

Fibrocartilaginous callus formation

Bony callus formation

Bone remodeling

What is osteoporosis?

A group of diseases where bone resorption exceeds deposit. Matrix is normal but bone mass declines

What bones are most susceptible to osteoporosis?

Spongy spinal and femoral bone

What age group is osteoporosis most common in?

Postmenopausal women

What is Paget’s Disease?

Excessive and haphazard bone deposit and resorption that causes the bones to be made quickly but poorly

What bones are most affected by Paget’s Disease?

Spine, femur, pelvis, and skull

Is the more spongy or compact bone present in Paget’s Disease?

More spongy