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.
Thyroxine’s role in the formation of bone
Stimulates cellular metabolism and increases osteoblast activity.
Testosterone’s role in the formation of bone
Promotes bone disposition (bone growth)
Estrogen’s role in the formation of bone
Inhibits osteoclast
Calcium Ion Homeostasis
regulated by the parathyroid and calcitonin
Parathyroid Hormone
*Stimulates osteoclast (breakdown of bone, releasing calcium)
*Increases intestinal absorption of calcium (via increased calcitriol production by the kidney)
*Decreases calcium loss from the body in urine.
*The overall effect is to increase blood levels of calcium.
Calcitonin
Increases osteoblast activity and decreases osteoclast.
Targets the kidney, which leads to the production of calcium-rich urine
The overall effect is to decrease the blood levels of calcium.
Closed (simple) fraction
Open (compound) fraction
Closed- the bone does not penetrate the skin
Open- the bone penetrates the skin
Comminuted Fraction
Bone fragment into three or more pieces.
Common in aged, whose bones are more brittle.
Compression Fraction
Bone is crushed
Common in porous bone subjected to extreme trauma.
Spiral Fraction
Excessive twisting forces are applied to a a bone
Common in sports fraction
Epiphyseal Fraction
Epiphysis and diaphysis separate along the epiphyseal plate.
Occurs when cartilage cells are dying and calcification of the matrix is occurring.
Depressed Fraction
Broken bone portion inward
Occurs on the skull fraction
Greenstick Fraction
The bone breaks incompletely. One side breaks and the other bends.
Commonly occurs in children whose bones are relatively more organic matrix and more flexible.
What are the treatments for fraction?
Reduction which is the restoration to normal position and immobilization.
Realignment of the bone
What is the order or steps of bone fracture repair?
Hematoma
Soft callus formation
Spongy Bone replaces the cartilage of the external callus forming a bony callus
Bony Callus is remodeled to form a permanent patch of compact bone
