Skeletal System Flashcards
seven functions of the skeletal system
support, protection, assist body movements, mineral homeostasis, hormone secretion
osteocalcin
a hormone secreted in the skeletal system that regulates bone formation and protects against obesity, glucose intolerance, and diabetes mellitus
where are blood cells produced
bone marrow
hematopoiesis
process in which blood cells are formed
RBS, WBS, platelets
Red marrow
develops RBC, WBC, fibroblasts and adipocytes
where is red bone marrow present
all marrow of newborns, adult hip bones, breast bone, vertebrae, skull, and ends of arm and thigh bones
Yellow marrow
primary function is storage of energy
yellow marrow percentage increases in with age
some can be converted back to red marrow if necessary
what cells primarily make up yellow marrow
adipose cells for the storage of triglycerides
tendons connect what
muscle to bone
ligaments connect what
bone to bone
tissue types found in the skeletal system
nervous, osseous, cartilage, fibrous connective tissue, muscle, and epithelial
two main skeletal tissues
cartilage, bone tissue (osseous)
skeletal cartilage
chondroblasts secrete cartilage matrix, chondrocytes maintain the matrix
holds water which lends resiliency,
no nerves or blood vessels
perichondrium
dense connective tissue girdle that contains blood vessels for nutrient delivery and waste removal
resists outward expansion
where is perichondrium not found
on cartilaginous articular surfaces and fibrocartilage
why do injuries to the cartilage take longer to heal
there is no direct blood supply
what makes up cartilage
chondroitin sulfate and various fibers
what do the fibers in cartilage do
distinguish the types of cartilage
three types of cartilage
hyaline, fibrocartilage, elastic
hyaline cartilage
support, flexibility, resilience
predominantly collagen fibers and chondroitin sulfate
which type of cartilage is the most abundant
hyaline cartilage
where is hyaline cartilage found
articular, costal, respiratory, and nasal cartilage
covers the tip of bones
elastic cartilage
similar to hyaline cartilage but contains elastic fibers
where is elastic cartilage found
external ear and epiglottis
fibrocartilage
dense matrix of fibrous bundles of collagen
great tensile strength and shock absorption
usually sandwiched between hyaline cartilage
where is fibrocartilage found
menisci of knee, intervertebral discs, pubic symphysis
articular cartilage
thin layer of hyaline cartilage that covers the epiphysis of long bones and joint surfaces of other bones
where is articular cartilage found
where the bone forms an articular joint surface
-bone moves against another bone
where is articular cartilage not found
in immovable joints
bone tissue
highly vascularized
hard, mineralized, extracellular matrix
two arrangements of bone tissue
compact bone, spongy bone
compact bone
strongest form of bone tissue
function of compact bone
protection and support
where is compact bone located
diaphysis of long bones, external layer of all bones
where is compact bone located
diaphysis of long bones, external layer of all bones
spongy bone
spongy appearance, less organized tissue
function of spongy bone
lightweight, provides tissue support
where is spongy bone located
epiphysis and internal cavity of long bones
trabeculae
honeycomb structure of bones, webbing of spongy bones
support and protect the red bone marrow
how are trabeculae oriented
along lines of stress to avoid breaking
what process occurs in the red marrow of spongy bone
hematopoiesis
what chemically makes up bone tissue
water, organic proteins (collagen main one), mineral salts
what organic chemical constituent is the most abundant in bone tissue
collagen fibers for flexibility and tensile strength
inorganic hydroxyapatite crystals
mineral salts, provide hardness
types of mineral salts
calcium phosphate, calcium carbonate, magnesium, fluoride, sulfate
two major groups of the skeletal system
axial and appendicular
based on location
axial skeleton
long axis of body, skull, vertebral column, rib cage
appendicular skeleton
bones of upper and lower limbs
girdles attach limbs to axial skeleton
how many bones are in the human skeleton
206
five classifications of bones
long, short, flat, irregular, sesamoid
long bones
longer than they are wide
examples of long bones
femur, tibia, fibula, humerus, ulna, radius, metacarpals, metatarsals, phalanges
short bones
cube shaped bones, vary in size and number in different individuals
examples of short bones
carpals and tarsals
flat bones
thin, flat, slightly curved
examples of flat bones
sternum, scapula, ribs, most skull bones
irregular bones
complicated shapes
examples of flat bones
vertebrae, coxal bones
sesamoid bones
within tendons, help change the angle of pull of a muscle
examples of sesamoid bones
patella, pisiform
sixth type of bone
sutural bones, wormian bones
located within the sutures of cranial bones
periosteum
tough sheath of dense, irregular connective tissue on the OUTSIDE of the bones
many nerve fibers and blood vessels
double layer membrane
assists with fracture repair and is an attachment point for tendons and ligaments
double layer of periosteum
outer fibrous layer- dense irregular connective tissue
osteogenic (inner) layer
osteogenic layer
contains primitive stem cells - osteogenic cells
what can osteogenic cells differentiate into
osteoblasts in the periosteum
osteoblasts in the osteogenic region help with what
can grow in thickness but not length (build bones)
where is periosteum found
covers external surfaces of bones except at joints
medullary cavity
space between the diaphysis of long bones that contain fatty yellow bone marrow in adults
endosteum
covers internal bone surface, covers trabeculae of spongy bone, lines canals that pass through compact bone
contains osteogenic cells that can differentiate into other bone cells
cells in osseous tissue
osteogenic cells –> osteoblasts –> osteocyte
osteoclast (different origin not from osteogenic cell)
osteogenic cells
also called osteoprogenitor cells
mitotically active stem cells in periosteum and endosteum
differentiate into osteoblasts or bone lining cells
can remain as ostegenic cells
osteoblasts
bone building cells, synthesize and secrete collagen fibers and other organic components
osteocytes
mature form of osteoblast
monitor and maintain bone matrix
act as stress or strain sensors
communicate with osteoblasts and osteoclasts so bone remodeling can occur
osteoclasts
break down cells
concentrated in endosteum
derived from the fusion of monocytes (WBC)
secrete acid and collagenase that dissolve bone
structure of long bone
diaphysis - shaft/ body
epiphysis - proximal/distal ends of long bone
metaphyses - area where epiphysis and diaphysis joint
where is the epiphyseal plate found in long bones
within the metaphyses
during childhood the epiphyseal growth plate is primarily composed of what cartilage
hyaline cartilage
in adults the epiphyseal growth plate becomes what
the epiphyseal line
cartilage becomes calcified
structure of short, irregular, sesamoid, and flat bones
thin plates of spongy bone covers sandwiched between compact bone
periosteum and endosteum
no shaft or epiphyses
bone marrow distributed throughout spongy bone (no marrow cavity)
hyaline cartilage covers movable articular surfaces
compact bone contains units called what
osteons
osteons also called what
Haversian systems
what are osteons formed from
concentric llamelae (rings of calcified matrix)
interstitial llamelae
between osteons, left over fragments of older osteons
outer circumferential llamelae
encircle the bone beneath periosteum
inner circumferential llamelae
encircle the medullary cavity
lacunae
small spaces between the lamellae
house osteocytes
canaliculi
small channels filled with extracellular fluid and osteocyte plasma membrane extensions that connect the lacunae
central canal
central space in osteon that houses blood, nerve, and lymphatic vessels (vertical)
perforating (Volkmann’s) canals
allow transit of these vessels and nerves to inner regions of the bone (across)
spongy bone lacks what
osteons
instead lamellae are arrange in thin columns called trabeculae
trabeculae of spongy bone contain what
lacunae which contains osteocytes that nourish the mature bone tissue from the blood
interior of ends of long bones contain what type of bone
spongy bone, to contribute to strength but lessen overall weight
blood and nerve supply of bone
bone is richly supplied with blood
nerves accompany blood vessels
periosteum rich in sensory nerves sensitive to tearing or tension
another name for ossification
osteogenesis
ossification
process of forming new bone
occurs in four situations
four situations of ossification
- formation of bone in late state embryo
- growth of bones until adulthood
- remodeling of bone
- repair of fractures
two methods of ossification
intra-membranous ossification
endochondral ossification
when does ossification star
about the 8th week of embryonic development
intramembranous ossification
produces spongy bone (may remodel into compact bone)
simpler method
MANY ossification centers
no cartilaginous stage
woven bone and periosteum are formed
lamellar bone replaced woven bone and red marrow appears
intramembranous ossification forms what types of bones
flat bones of the skull, mandible, and clavicle
intramembranous ossification forms bones from what type of cell
mesenchymal cells the develop into osteoblasts within the fibrous membrane
endochondral ossification
process where bone replaces cartilage
forms both spongy and compact bone
used in most bones, especially long bones
process of endochondral ossification
replacement of hyaline cartilage model by bone
begins at primary ossification center in the center of the shaft
bone collar forms around the diaphysis of cartilage model
central cartilage in diaphysis calcifies creating cavities
periosteal bud invades cavities (formation of spongy bone)
diaphysis elongates and medullary cavity forms
secondary ossification center form in the epiphyses
epiphyses ossify
blood vessel infiltration of the perichondrium converts it to what
periosteum. the underlying cells are replaced by osteoblasts
postnatal bone growth methods
interstitial (longitudinal) growth - length
appositional growth - thickness
interstitial (longitudinal) growth
requires presence of epiphyseal cartilage (maintains a constant thickness)
concurrent modeling of epiphyseal ends to maintain proportion
five zones within cartilage for interstitial growth
- resting (quiescent) zone
- proliferation (growth) zone
- hypertrophic zone
- calcification zone
- ossification (osteogenic) zone
resting (quiescent) zone
cartilage on epiphyseal side of epiphyseal plate
relatively inactive
proliferation (growth) zone
cartilage on diaphysis side of epiphyseal plate
rapidly divide pushing epiphysis away from diaphysis
lengthening
hypertrophic zone
older chondrocytes, closer to diaphysis, enlarge with their lacunae
lacunae erode - interconnecting spaces
calcification zones
surrounding cartilage matrix calcifies
chondrocytes die and deteriorate
ossification zones
chondrocyte deterioration leaves long spicules of calcified cartilage at epiphyses - diaphyses junction
spicules eroded by oseoclasts
covered with new bone by osteoblasts
replaced ultimately with spongy bone
near the end of adolescence
chondroblasts divide less often
osteoblast activity > chondroblast activity
bone lengthening ceases
epiphyseal plate closure - replaced by bone (18 in females, 21 in males)
bone of diaphysis and epiphyses fuse
fractures to epiphyseal growth plate affect what
can cause it to close sooner
may inhibit growth of bone length
appositional growth
allows for lengthening bone to widen
occurs throughout life
osteoblast contribution of appositional growth occurs where
periosteum
secretes bone matrix on external bone
osteoclast contribution of appositional growth occurs where
endosteum
removes bone on endosteal surface
is there more building or breaking of bones typically
building up - to make bones thicker and stronger but not too heavy
when there is too much osseous tissue formation
bones become abnormally thick
acromegaly
when there is not enough new bone formation
bones can become too weak and thin
osteoporosis - excessive loss of calcium
rickets/ osteomalacia - bones are too soft
factors affecting normal bone growth
minerals
calcium, phosphorous, magnesium, fluoride, manganese
what vitamins are essential for bone growth
Vit A - osteoblast acitivity
Vit C - synthesis of collagen
Vit D - promotes absorption of calcium in the gut
Vit K and B12 for synthesiss of bone protein
Vitamin D and Ca deficiency can happen where
low sun exposure or low calcium content in diet
Rickets
caused by a calcium and vitamin D deficiency
common in children
what hormone is most important for bone growth during childhood
Human growth hormone (hGH)
Growth factors (IGF) - produced by liver
-both stimulate osteoblasts, promote cell division at the epiphyseal plate, and enhance protein synthesis
Thyroid hormone - modulation of activity of growth hormone
Sex hormone (estrogen and testosterone)
why is thyroid hormone important
ensures proper bone proportions
sex hormones affect on bone growth
cause a dramatic effect on bone growth (growth spurt)
in females - widening of the pelvis
responsible for closing epiphyseal plate at end of puberty
important in bone density maintenance during adulthood
methods of bone remodeling control
- negative feedback hormonal loop for Ca homeostasis
- response to mechanical and gravitational forces
negative feedback hormonal loop for Ca homeostasis
maintaining a normal serum calcium levels > mineralizing bone
Parathyroid hormone - removes calcium from the bone regardless of bone integrity
Calcitonin - tones down calcium level in the blood temporarily
PTH function
stimulates osteoclastic activity and raises blood serum calcium level
stimulates reabsorption of calcium ions in the kidneys
calcitonin
stimulates osteoblastic activity and lowers the serum calcium level
production of vitamin D with regards to Ca
for absorption of Ca and posphate
Response to mechanical and gravitational forces
bones are stressed when bearing weight or pulled by muscle
bones reflect stresses they encounter (thickest where there is most tension)
Wolff’s Law
bones grow and remodel in response to the demands place on it
examples of Wolff’s Law
right hand dominant - thicker bones in right arm
curved bones are thickest where most likely to buckle
trabeculae of spongy bones form trusses along lines of stress
large bony projections where heavy active muscles attach
bones of fetus and bedridden are featurless
hormonal control determines what
if and when remodeling is necessary
mechanical/ gravitional stress determines what
where remodeling occurs
fractures
breaks in the bone tissue
fractures in youth primarily caused by
trauma
fractures in old age primarily caused by
bone weakness/ thinning
position of bone after fracture (fracture)
non-displaced: ends retain normal position
displaced: ends out of normal alignment
completeness of break (fracture)
complete - all the way through
incomplete- not broken all the way
penetration of skin (fracture)
open (compound) - penetrated
closed (simple) - not penetrated
fractures can be classified by
location, external, appearance, nature, Eponym (someones name)
comminuted fracture
bone fragments into three or more pieces
common for elderly
spiral fracture
ragged break occurs when excessive twisting forces are applied to a bone
common sports fracture
depressed fracture
broken bone portion is pressed inward
typical of skull fracture
compression fracture
bone is crushed
common in porous bones (osteoporotic bones) subject to extreme trauma (falling)
-vertebrae
Epiphyseal fracture
epiphysis separates from diaphysis along epiphyseal plate
Greenstick fracture
bone breaks incompletely, only one side of shaft breaks - other side bends
common in children whose bonds have relatively more organic matrix and more flexible than those of adults
fracture treatment - reduction
realignment of broken bone ends
-open reduction
-closed reduction (does not require opening)
fracture treatment - immobilizationt
by cast or traction for healing
depends on break severity, bone broken, and age
fracture repair pattern
- fracture hematoma (clot) forms as a result of blood vessels breaking in the periosteum and osteons
site is swollen, painful, and inflamed - formation of a callus
- mass of repair tissue - fibrocartilaginous callus
- within a week new trabeculae appear in fibrocartilaginous callous
- approx 2 months later firm union forms
- remodeling - takes several months
formation of callus during bone fracture
capillaries grow in hematoma, phagocytes clear debris, fibroblasts secrete collagen fibers to span break and connect broken ends
fibroblasts, chondroblasts, and osteogenic cells begin reconstruction of bone
create cartilage matrix of repair tissue
osteoblasts begin to form spongy bone within matrix
remodeling process during bone fracture repair
spongy bone is replaced with compact bone on superficial areas
fracture line disappears- little to no evidence remains once complete
exercise and bone tissue
mechanical stress makes bone tissue stronger through production of collagen fibers by osteoblasts and deposition of mineral salts
loss of bone mass (aging)
loss of calcium from bones (osteoporosis)
