Chapter 6: Bones Part 2 Flashcards
What is ossification?
Physical process of bone formation and bone growth.
What two ways does ossification occur?
Endochondral
Intramembranous
Endochondral Ossification
Bone replaces existing cartilage.
Bone growth occurs through interstitial growth and appositional growth.
Intramembranous Ossification
Bone develops directly from messenchyme (loosely organized embryonic connective tissue) or fibrous connective tissue.
What is the embryonic skeleton made up?
Embryo-hyaline cartilage.
Cartilage remains in isolated areas
Bridge of the nose
Parts of ribs
Joints
Intramembranous Ossification
Some bones in the embryo= dense irregular connective tissue of the dermis.
Takes place in the deeper layers of the dermis
The bones that result are called dermal bones, such as the skull, mandible, and clavicles.
Begins about the 8th week of embryonic development.
Secondary Ossification (Endochondral)
The epiphyseal plate is made out of hyaline cartilage.
Cartilage cells close to the diaphysis divide and push toward the diaphysis.
Older cartilage became ossified,
Cartilage is broken down and bone replaces cartilage.
Interstitial Growth
Cartilage is continually growing, and it is replaced by bone.
Capillaries and osteoblasts migrate to the epiphyses creating secondary ossification centers.
Epiphysis becomes filled with spongy bone.
On the shaft side of metaphysis, osteoblasts invade cartilage and replace it with bone.
New cartilage is replaced at the same rate on the epiphyseal side.
At puberty, the rate of epiphyseal cartilage production slows down and the rate of osteoblast speeds up.
The epiphyseal plate becomes narrow and it disappears becoming the epiphyseal line.
Remodeling
Occurs as the bone is resorbed and replaced by new bone.
Occurs in reponse to stress placed on bones.
Homeostasis.
Bone tissue is broken down and resorbed by osteoclasts, liberating minerals. Osteoblast builds new bone tissue (osteoid). Osteoblast will become embedded and become osteocytes.
Appositional Growth
When a developing bone increases in diameter at the outer surface.
Typically, it increases in width.
When does remodeling occur?
In response to the stress placed on bones.
Weight-bearing exercise leads to stress on bones that generates minute electrical fields.
Weightlessness and being bedridden also cause remodeling to occur.
What minerals and vitamins are important in the formation of bone?
Protein, vitamins A, C, and D, and calcium.
What hormones are important in the formation of bone?
Growth hormone
Thyroxine
Testosterone
Estrogen
Growth Hormone in the formation of bone
Stimulates protein synthesis, cell division, and cell growth thought the body.
During infancy and childhood.
