Class Notes - Bones

Question 1

What is the 3rd step of intramembranous ossification?

Answer 1

(Woven)

• woven bone and periosteum form
• accumulating osteiod is laid down between embryonic blood vessels, forming a network of trabeculae (woven bone)
• vascularized mesenchyme condenses on the external face of the bone and becomes the periosteum

Question 2

What is the 4th step of intramembranous ossification?

Answer 2

(Compact)

• compact bone replaces woven bone, just deep to the periosteum. red marrow develops
• trabeculae just deep to the periosteum are remodeled and replaced with compact bone
• the woven bone in the center is remodeled into spongy bone (diploe) that is eventually filled with red marrow

Question 3

What is the 1st step of endchondral ossification?

Answer 3

(Collar)

Bone collar forms around the diaphysis of the hyaline cartilage model

Question 4

What is the 2nd step of endchondral ossification?

Answer 4

(Calcify)

Cartilage in the center of the diaphysis calcifies and then develops cavities

Question 5

What is the 3rd step of endchondral ossification?

Answer 5

(Bud)

The periostreal bu invades the internal cavities and spongy bone form

Question 6

What is the 4th step of endchondral ossification?

Answer 6

Cavity [Medullary])

The diaphysis elongates and the medullary cavity forms

Question 7

What is the 5th step of endchondral ossification?

Answer 7

(Ossify)

the epiphyses ossify. when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartialges

Question 8

when does bone remodeling occur?

Answer 8

constantly through life

Question 9

How is bone remodeled?

Answer 9

process involving bone formation and bone destruction in response to mechanical and hormonal factors

Question 10

bone resorption

Answer 10

• by osteoclasts
• dig into bone/break down tissue with HCL
• lysosomal enzymes are released to digest the organic matrix
• osteoclasts use phagocytosis to take up collagen and dead osteocytes

Question 11

bone depostition

Answer 11

• by osteoblasts

* cells lay down organic osteoid on bone surfaces

Question 12

bone remodeling disorders

Answer 12

Paget’s disease

• excessive rates of bone deposition and bone resorption
• bones are soft and weak

Question 13

osteoporosis

Answer 13

age-related condition (affects many elderly women) in which bones weaken as bone resorption outpaces

Question 14

Osteomalacia

Answer 14

• aka rickets
• bones are inadequately mineralized
• caused by inadequate amounts of vitamin D or calcium phosphate in the diet