Chapter 6: Bone Formation (Final Exam)

Sex hormones

(major hormone to help growth) (estrogen and testosterone) -promotes bone growth -later induces closure of epiphyseal plates

thyroid hormones

(major hormone to help growth) ensures that the skeleton retains proper proportions -the most important

Growth Hormone

(major hormone to help growth) produced by the pituitary gland -stimulates epiphyseal plates

Epiphyseal

(type of fracture) -Epiphysis separates from the diaphysis along the epiphyseal plate -tends occur where cartilage cells are dying and calcification of the matrix is occurring

Greenstick

(type of fracture) -bone breaks incompletely, much in the way a green twig breaks. Only one side of the shaft breaks, the other side bends -common in children, whose bones have relatively more organic matrix and are more flexible than those of adults

Comminuted

(type of fracture) -bone fragments into three or more pieces -particularly common in the aged, whose bone are more brittle

Compression

(type of fracture) -bone is crushed -common in porous bones (example osteoporotic bones) subjected to extreme trauma, as in a fall

Depressed

(type of fracture) -broken bone portion is pressed inward -typical of skull fracture

Spiral

(type of fracture) -ragged break occurs when excessive twisting forces are applied to a bone -common sports fracture

Ossification (osteogenesis)

- Are both names for the process or bone-tissue formation - Osteogenesis begins in the embryo, proceeds through childhood and adolescence as the skeleton grows, and then occurs at a slower rate in the adult as part of a continual remodeling of the full grown skeleton

Endochondral Ossification

-All bones from the base of the skull down, EXCEPT for the clavicles are endochondral bones -They are first modeled in hyaline cartilage, which then is gradually replaced by bones tissue -Endochondral ossification begins late in the second month of development and is not completed until the skeleton stops growing in early adulthood -Growing endochondral bones increase both in length and in width

Epiphyseal plates

-Cartilage is organized for quick, efficient growth -The cartilage cells nearest the epiphysis are relatively small and inactive this region is called the resting zone -Cartilage cells form tall stacks --Chondroblasts at the top of stacks divide quickly -Pushing the epiphysis away from the diaphysis thereby causing the entire long bone to lengthen -Lengthens entire long bone

Appositional growth

-Inner layer of the periosteum differentiates to form osteoblasts and adds bone matrix to the surface -Osteons form -Bone continues to enlarge in diameter

Factors regulating Bone Growth

-Nutrition -Calcium ions -Phosphate ions -Magnesium ions -Citrate -Carbonate ions -Sodium ions -Vitamins A, C, D (calcitriol)

Osteoporosis

-Occurs most often in the aged, particularly in women who have gone through menopause -Men develop it to a lesser degree -Estrogen deficiency is strongly implicated in osteoporosis in older women because the secretion of estrogens, which helps maintain bone density, wanes after menopause -Additional factors to osteoporosis is --Insufficient exercise to stress the bone --A diet poor in calcium and protein --Inadequate levels of vitamin d because bone deposition rates are high during adolescence and early adulthood, proper diet and exercise during these years is crucial for developing and maintaining healthy bone in later life -Bone reabsorption outpaces bone deposition -occurs most often in women after menopause

Osteosarcoma

-a form of bone cancer -Sarcoma is any cancer arising from connective tissue cell or muscle cell and osteo means bone (osteosarcoma = a form of bone cancer) -Primarily affects young people between 10-25 years old -Originates in a long bone of the upper or lower limb, with 50% cases arising near the knee -The cancer cells derive from osteoblast like cells of mesenchymal origin in the parts of the diaphysis nearest the epiphses

membrane bone

-formed directly from mesenchyme -Develop from a mesenchymal membrane through a process called intramembranous ossification -Other bones develop as hyaline cartilage which is replaced through a process called endochondral ossification -These bones are called endochondral bones or cartilage replacement bones

Osteomalacia

-occurs in adults : bones are inadequately mineralized (less mineralization;have to take calcium tablets) -Is caused by inadequate amounts of vitamin d or calcium phosphate in the diet -Cured by drinking vitamin D- fortified milk and exposing the skin to sunlight

Rickets

-occurs in children : analogous to osteomalacia -Is increasing in prevalence in children ages 6-24 months -Several factors have contributed to this increase --Breast feeding without vitamin d supplementation --Spending more time indoors --Increased used of sunscreen -Is caused by inadequate amounts of vitamin d or calcium phosphate in the diet -Cured by drinking vitamin D- fortified milk and exposing the skin to sunlight

Bone deposition

Accomplished by osteoblasts

Bone reabsorption

Accomplished by osteoclasts

Osteogenesis

Bone formation

Endochondral ossification

Example: Limbs, vertebrae, hips -means it has to do with chondral or cartilage cells

intramembranous ossification

Example: clavicle, mandible, skill, face -Came from Mesenchyme -Membrane bones from directly from mesenchyme without first being modeled in cartilage -All bones of the skill, EXCEPT a few at the base of the skull are of this category -The clavicles (collarbones) are the only bones formed by intramembranous ossification that are not in the skull

Osteoblasts

add bone tissue to the external surface of the diaphysis

Bone deposit and removal

occurs at periosteal and endosteal surfaces

osteoclasts

remove bone from the internal surface of the diaphysis

Calcification

the deposition of calcium ions into the bone tissue the build up of calcium