November 23, 2015
Skeletal System Physiology
Growth & Developmt
osteoprogenitor cells: unspecialized cells found in
periosteum & endosteum, give rise to osteoblasts
osteoblasts: bone-forming cells
osteocytes: bone cells
osteoclasts: bone-destroying cells, as they break down
bone, they release Ca+ and P to blood
skeleton begins as cartilaginous model
all "bones" made in hyaline cartilage
ossification: the process of making bone
begins in 3 mo. old fetus & continues throughout life
but most ossification is done by age 25
2 major parts
1-making organic matrix
2-calcification
November 23, 2015
Ossification
1-making organic matrix
osteoblasts migrate into cartilaginous model
Golgi apparatus makes carbohydrates
ER makes collagenous fibers (protein)
these are both secreted outside of cells (osteoblasts)
laid down in layers, around the cells
the organic component makes bone strong
protein and carbs
2-calcification
minerals salts are deposited into matrix (Ca+ & P)
brought from blood, diet
this is the inorganic component of bone
this makes bones rigid, hard
November 23, 2015
Ossification begins in clusters in hyaline cartilage "bone"
cartilage begins to break down in center of "bone"
osteoblasts migrate in & make spongy bone in center, make
compact bone all around outside
as compact bone thickens, osteoclasts come in & eat away
spongy bone in center (diaphysis), leave spongy bone at
ends (epiphysis)
this makes marrow cavity
at birth, skeleton is bone except for areas of cartilage near
ends of bones
this cartilage is epiphyseal disk, allows for growth
November 23, 2015
Bone growth in length
epiphyseal disk: region of cart at both ends of long bones
called growth plate
during growth, cartilage cells divide, producing wider area
of cartilage, then that new growth is ossified
as long as epiphyseal disk is present, growth in height
will occur
when finished growing in height, epiphyseal cart becomes
bone
rate of growth is controlled by hormones
Bone growth in diameter
osteoblasts make new bone on outside of bone
osteoclasts destroy bone on inside, this enlarges marrow
cavity
process keeps proper diameter of compact bone outside to
marrow cavity
November 23, 2015
Bone formation & destruction occurs throughout life
osteogenesis: process of making new bone
resorption: process of destroying old bone
in infancy, childhood, teens
osteogenesis occurs at faster rate than resorption
results in growth in height & diameter
early and middle adulthood
osteogenesis = resorption
maintain bones, we break down & rebuild
healing
40+ resorption occurs at faster rate than osteogenesis
more bone is lost on inside, less forms on outside
get hollower, more brittle bones
November 23, 2015
Bone formation & destruction occurs throughout life
osteogenesis: process of making new bone
resorption: process of destroying old bone
in infancy, childhood, teens
osteogenesis occurs at faster rate than resorption
results in growth in height & diameter
early and middle adulthood
osteogenesis = resorption
maintain bones, we break down & rebuild
healing
40+ resorption occurs at faster rate than osteogenesis
more bone is lost on inside, less forms on outside
get hollower, more brittle bones
November 23, 2015
Osteoporosis
men lose 25% bone mass over age 40
women lose 40% bone mass over age 40
the difference is in sex hormones
sex hormones help maintain bone strength
male hormone production does not decrease until age 65
female hormone production decreases at age 45
extremely impt for Ca+ to be present in diet NOW
we store Ca+ in bones and teeth
Ca+ is needed for more than bone hardness
Ca+ is needed for muscle contraction, Ca+ is needed
for every nerve impulse transmission
if you do not bring in enough in diet, the body takes
what it needs from the bones
November 23, 2015
Bone repair
complete fracture: bone breaks in 2 pieces
incomplete fracture: bone breaks but not in 2 separate piece
simple fracture: break does not pierce skin
compound fracture: bone pierces through skin
impacted fracture: broken ends of bones are wedged into
each other
spiral fracture: break is ragged due to twisting of bone
healing: hematoma formation: blood escapes from broken
blood vessels forming a hematoma between broken
bones
fibrocartilage callus: fibrocart begins dividing and filling
space between bones
bony callus: osteoblasts turn fibrocart into bone
remodeling: osteoblasts build new bone at edges, osteoclasts create new cavity or eat at bone that was not
formed correctly