Chapter 7 Flashcards
functions of skeletal system
support and protect, levers for movement, hemopoiesis, storage of minerals and energy reserve.
Compact bone
dense; cortical bone. 80 percent of bone mass
spongy bone
cancellous, internal to compact bone. appears porous and is 20% of bone mass
long bones
greater in length than width
short bones
nearly equal from length to width
flat bones
flat, thin surfaces that may be slightly curved
irregular bones
elaborate, complex shapes
medullary cavity
contains red bone marrow in kids and yellow in adults. Inside of endosteum.
articular cartilage
at the end of long bones, reduces friction and absorbs shock in moveable joints
epiphyseal plate
growth plate, in adults the epiphyseal line remains after plate. in metaphysis.
periosteum
outer fibrous layer of dense irregular connective tissue that protects bone, anchors blood vessels and nerves and attachment site for ligaments and tendons. The inner cellular layer includes osteoprogenitor, osteoblasts, and osteoclasts
endosteum
contains osteoprogenitor cells, osteoblasts, and osteoclasts
nutrient foramen
small opening in bone where artery and nerves enter and vein exits.
bone marrow
2 kinds; red and yellow. is a soft connective tissue
red bone marrow
hemopoietic, located in spongy and medullary cavity in long bones in kids and located in skull, spine, ribs, sternum, and proximal epiphyses of humerus and femur in adults.
yellow bone marrow
product of red bone marrow degeneration as children mature-made out of fat/ may convert back to red in severe anemia
osteoprogenitor cells
stem cells that divide and create osteoblasts
osteoblasts
synthesize and secrete osteoid. becomes entrapped within the matrix and differentiate into osteocytes.
osteocytes
mature bone cells derived from osteoblasts. detect stress on bone and trigger new bone formation
osteoclasts
large, multinuclear, phagocytic cells involved in bone resorption
osteoid
osteoid is an organic compound produced by osteoblasts and contains collagen protein and semisolid ground substance of proteoglycans and glycoproteins. gives bones strength by resisting stretching and contributes to bone flexibility.
inorganic components of bone
salt crystals, calcium phosphate. Calcium phosphate interacts with calcium hydroxide to form crystals called hydroxyapatite. substances included in crystals are calcium carbonate, sodium, magnesium, sulfate, and fluoride. These crystals deposit around collagen fibers and make hard matrix.
bone formation
begins with secretion of osteoid and calcification occurs which is the deposition of hydroxyapatite crystals. bone formation requires vitamin d, c, calcium, and phosphate
Vitamin D is needed for what in bone formation
enhances calcium absorption from digestive tract
Vitamin C is needed for what in bone formation
required for collagen formation
Calcium and Phosphate is needed for what in bone formation
calcification
Bone resorption
bone matrix is destroyed by proteolytic enzymes released from the lysosomes of osteoclasts. freed calcium and phosphate ions enter the blood and this occurs when blood calcium levels are low
proteolytic enzymes
break down calcium and phosphate by hydrochloric acid and proteolytic enzymes released by lysosomes within osteoclasts.
osteons
basic functional and structural unit of mature compact bone; parallel to diaphysis and looks like bulls eye target.
central canal
channel at center of osteon; blood vessels and nerves extend through it.
concentric lamellae
rings of bone tissue that surround central canal
osteocytes
mature bone cells found in small spaces between concentric lamellae (lacunae) that maintain bone matrix.
canaliculi
tiny, interconnecting channels within bone that allow exchange of nutrients, minerals, gases, and wastes b/w blood vessels and osteocytes
ossification
formation and development of bone that begins in embryo and continues through childhood. Skeleton begins formation by 8-12 week of embryonic development.
Intramembranous ossification
bone growth within a membrane. Starts in dermis. Produces facial bones, skull, mandible and clavicle.
Steps of intramembranous ossification
- ossification centers form within mesenchyme. Cells become osteoprogentor or osteoblast cells.
- Osteoid undergoes calcification and entrapped cells become osteocytes.
- woven bone (primary bone) and the periosteum form.
- Lamellar bone (secondary bone) replaces woven bone. Compact and spongy bone form from trabeculae.
Endochondral Ossification
begins with hyaline cartilage model. Produces most bones like long bones. Condroblasts secrete cartilage matrix
- then cartilage calcifies and periosteal bone collar forms. Chondrocytes in cartilage model produces holes in matrix and calcifes, chondrocytes die. blood vessels grow toward cartilage. and osteoblasts secrete osteoid
- primary ossification center forms in diaphysis. bone development extends in both directions towards epiphyses
- Secondary ossification centers form in epiphyses. Hyaline cartilage calcifies and degenerates. blood vessels and osteoprogenitor cells enter. bone displaces cartilage.
- bone replaces cartilage
- epiphyseal plates ossify
Interstital growth
bone growth in length. Occurs within zone 2 (proliferating cartilage) and 3 (hypertrophic cartilage) and pushes zone towards epiphysis
epiphyseal plate
maintains thickness through childhood, and at maturity the rate of cartilage production slows. Remnant is thin line of compact bone called epiphyseal line
appositional bone growth
bone growth in width. occurs in periosteum where bone matrix is deposited within layers parallel to surface. osteoclasts resorb bone matrix along medullary cavity.
bone remodeling
continues through adulthood. occurs at periosteal and endosteal bone surface. 20% of skeleton is replaced yearly.
mechanical stress on bones
occurs with exercise and weight. stress is required for normal remodeling. Osteocytes communicate to osteoblasts that increase synthesis of osteoid and increase bone mass.
Hormones
molecules released from one cell into the blood to affect things. Some alter rates of chondrocytes, osteoblasts, and osteoclast activity. affects bone composition and growth patterns.
growth hormone
somatotropin; produced by anterior pituitary gland. Stimulates liver to produce somatomedin. Both of these hormones directly stimulate growth of cartilage in epiphyseal plate.
thyroid hormone
secreted by thyroid gland. influences basal metabolic rate of bone cells and regulates normal activity at epiphyseal plates.
Sex hormones
estrogen and testosterone; secreted in large amounts at puberty; dramatically accelerates bone growth and rate of cartilage growth and bone formation in epiphyseal plate. Eventually bone formation rate is greater than cartilage growth and the cartilage is replaced with bone- halting growth.
glucocorticoids
group of steroid hormones released by adrenal cortex to regulate blood glucose levels. High amounts of this hormone increase bone loss preventing growth.
serotonin
neurotransmitter and hormone. Most bones have serotonin receptors and plays a role regulation of bone remodeling. If levels are too high, osteoprogenitor cells are prevented from differentiating into osteoblasts that could cause bone density problems.
calcium
required for muscle contraction, exocytosis, stimulation of heart, blood clotting, and neurons. regulated primarily by calcitriol and pth
steps from vitamin d to calcitriol
- uv light converts 7 dehydrocholesterol to vit. d and it is released into the blood and circulates through body.
- converted to calcitriol by kidney. Pth increases, so more calcitriol is formed
rickets
vit. d deficiency in childhood; deficient calcification of osteoid tissue. bowlegged, disturbances in growth and tetany.
parathyroid hormone
secreted by parathyroid gland in response to reduced blood calcium. Accelerates conversion to calcitriol by kidneys and to increase calcium reabsorption. calcitriol increases absorption of calcium in small intestine; and bone releases calcium into blood by increasing osteoclast activity.
Calcitonin
aids in regulating blood calcium levels. released by thyroid gland in response to high blood calcium and exercise. Inhibits osteoclast activity, stimulates kidneys to excrete calcium and has greatest effect during greatest bone turnover (growing children)
effects of aging on bones
decreased strength and loss of calcium with insufficient ossification
Osteopenia
occurs slightly in all people with age. starts 30-40’s. Osteoblast activity declines and osteoclast activity stays stable. spine, jaw and epiphyses lose a lot of mass; women lose more.
Osteoporosis
reduced bone mass that compromises normal function; occurs more often in older women. reduced hormones with age contributes to reduced bone mass.
stress fracture
thin break caused by increased physical activity
pathologic fracture
occurs in bones weakened by disease
simple fracture
broken bone not penetrating skin
compound fracture
one or both ends of bone pierce overlying skin
