skeletal system Flashcards
Skeletal Cartilages
Contain no blood vessels or nerves
Dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage
Hyaline cartilages
imperceptable, nose joints, chondroblasts, supports, reinforces, resists repetetive stress
Fibrocartilages
thick collagen fibers, tensile strength and shock absorber, discs
elastic cartilage
more elastic fibers, big lacunae
articular surface
where things go together and touch
growth of cartilage appositional
Cells secrete matrix against the external face of existing cartilage
growth of cartilage interstitial
Chondrocytes divide and secrete new matrix, expanding cartilage from within
growth of cartilage calcification occurs during
normal bone growth, old age
two main groups of bones (by location)
Axial skeleton (brown) Appendicular skeleton (yellow)
Axial skeleton (brown)
straight down axis. skull, vertebrae, ribs
Appendicular skeleton (yellow
appendages. arms, legs
Long bones
Longer than they are wide
Short bones
Cube-shaped bones (in wrist and ankle) Sesamoid bones (within tendons, e.g., patella)
flat bones
Thin, flat, slightly curved
skull sternum
irregular bones
complicated bones
vertebrae
functions of bones
support (For the body and soft organs)
protection (For brain, spinal cord, and vital organs)
movement (Levers for muscle action)
storage (calcium, phorphorous, growth factors, triglyceride energy)
blood cell formation in marrow cavities
bone Bulges, depressions, and holes serve as
Sites of attachment for muscles, ligaments, and tendons
Joint surfaces
Conduits for blood vessels and nerves
Tuberosity
rounded projection
Crest
narrow, prominent ridge
Trochanter
large, blunt, irregular surface
Line
narrow ridge of bone
Tubercle
small rounded projection
Epicondyle
raised area above a condyle
Spine
sharp, slender projection
Process
any bony prominence
projections that help form joints
head
facet
condyle
ramus
head
Bony expansion carried on a narrow neck
facet
Smooth, nearly flat articular surface
condyle
Rounded articular projection
ramus
armlike bar
meatus
canal like passageway
sinus
Cavity within a bone
fossa
Shallow, basinlike depression
groove, furrow
narrow depression
fissure
Narrow, slitlike opening
foramen
Round or oval opening through a bone
Compact bone
Dense outer layer
spongy bone
Honeycomb of trabeculae
structure of long bone
Diaphysis
Epiphyses
Diaphysis
shaft)
Compact bone collar surrounds medullary (marrow) cavity
Medullary cavity in adults contains fat (yellow marrow)
Epiphyses
Expanded ends Spongy bone interior Epiphyseal line (remnant of growth plate) Articular (hyaline) cartilage on joint surfaces
Periosteum
Outer fibrous layer
Inner osteogenic layer
Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina
Secured to underlying bone by Sharpey’s fibers
what cells are in inner osteogenic layer
Osteoblasts (bone-forming cells)
Osteoclasts (bone-destroying cells)
Osteogenic cells (stem cells)
endosteum
Delicate membrane on internal surfaces of bone
Also contains osteoblasts and osteoclasts
Structure of Short, Irregular, and Flat Bones
no epiphysis no diaphysis Periosteum-covered compact bone on the outside Endosteum-covered spongy bone within Spongy bone called diploë in flat bones Bone marrow between the trabeculae
Red marrow cavities of adults
Trabecular cavities of the heads of the femur and humerus
Trabecular cavities of the diploë of flat bones
Red marrow of newborn infants
Medullary cavities and all spaces in spongy bone
Osteogenic (osteoprogenitor) cells
Stem cells in periosteum and endosteum that give rise to osteoblasts
Osteoblasts
Bone-forming cells
Osteocytes
mature bone cells in senescence (not dividing) until break bone
Osteoclasts
Cells that break down (resorb) bone matrix
Involved in bone repair
osteon
haverisian system contain lamellae (made of collagen fibers) central canal (blood vessels, nerves) perforating canals lacunae canaliculi
Perforating (Volkmann’s) canals
At right angles to the central canal
Connects blood vessels and nerves of the periosteum and central canal
lacunae
small cavities that contain osteocytes
canaliculi
hairlike canals that connect lacunae to each other and the central canal
spongy bone contains
trabeculae
Align along lines of stress
No osteons
Contain irregularly arranged lamellae, osteocytes, and canaliculi
Capillaries in endosteum supply nutrients
Chemical Composition of Bone: Organic
Osteogenic cells, osteoblasts, osteocytes, osteoclasts
osteoid
Osteoid
organic bone matrix secreted by osteoblasts
Ground substance (proteoglycans, glycoproteins)
Collagen fibers
Chemical Composition of Bone: Inorganic
Hydroxyapatites (mineral salts)
65% of bone by mass
Mainly calcium phosphate crystals
Responsible for hardness and resistance to compression
Osteogenesis (ossification)
bone tissue formation
bone development stages
Bone formation—begins in the 2nd month of development
Postnatal bone growth—until early adulthood
Bone remodeling and repair—lifelong
two types of ossification
Intramembranous ossification
Endochondral ossification
Intramembranous ossification
Membrane bone develops from fibrous membrane
Forms most flat bones (cranial bones)
Endochondral ossification
Cartilage (endochondral) bone forms by replacing hyaline cartilage
Requires breakdown of hyaline cartilage prior to ossification
Forms most of the rest of the skeleton
Intramembranous ossification steps
Ossification centers appear in the fibrous connective tissue membrane.
Bone matrix (osteoid) is secreted within the fibrous membrane and calcifies
Woven bone and periosteum form
Lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears.
Endochondral ossification steps
Bone collar forms around hyaline cartilage model
Cartilage in the center of the diaphysis calcifies and then develops cavities (medullar cavity)
The periosteal bud inavades the internal cavities and spongy bone begins to form (blood vessels go into medullar cavity in order for spongy bone to form)
The diaphysis elongates and a medullary cavity (thicker) forms as ossification continues. Secondary ossification centers appear in the epiphyses in preparation for stage 5.
The epiphyses ossify. When completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages.
Postnatal Bone Growth interstitial
length of long bones
Postnatal Bone Growth appositional
thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfaces
for growth in long bones (interstitial ) Epiphyseal plate cartilage organizes into four important functional zones
Proliferation (growth, top epi plate lengthing, cells dividing) (grows toward)
Hypertrophic (big lacunae9
Calcification (break down lacunae)
Ossification (osteogenic) /bone)
Growth hormone stimulates
epiphyseal plate activity
Testosterone and estrogens (at puberty)
Promote adolescent growth spurts
End growth by inducing epiphyseal plate closure
Bone Deposit
Occurs where bone is injured or added strength is needed
Requires a diet rich in protein; vitamins C, D, and A; calcium; phosphorus; magnesium; and manganese
Sites of new matrix deposit are revealed by
Osteoid seam
calcification front
osteoid seam
Unmineralized band of matrix
Calcification front
calcification front
The abrupt transition zone between the osteoid seam and the older mineralized bone
Bone Resorption
Osteoclasts secrete
(Lysosomal enzymes (digest organic matrix)
Acids (convert calcium salts into soluble forms)
Dissolved matrix is transcytosed across osteoclast, enters interstitial fluid and then blood
Bone Remodeling
Resorption (removal) and deposit occurring together
performed by osteoclasts and osteoblasts
Bone Remodeling occurs at
surface of periosteum and endosteum
does remodeling happen equally throughout skeleton
no, Areas of high stress remodeled more frequently to prevent those areas from becoming too brittle.
What controls continual remodeling of bone?
Hormonal mechanisms that maintain calcium homeostasis in the blood
Mechanical and gravitational forces sensed by osteocytes
(communicate to stimulate remodeling)
removal of osteocytes causes loss of
remodeling activities
Calcium is necessary for
Transmission of nerve impulses Muscle contraction Blood coagulation Secretion by glands and nerve cells Cell division
Hormonal Control of Blood Ca2+ flow chart
Blood Ca2+ levels drop Parathyroid glands increase release PTH PTH stimulates osteoclasts to degrade bone matrix and release Ca2+ Blood Ca2+ levels increase Parathyroid glands decrease PTH
wolffs law
A bone grows or remodels in response to forces or demands placed upon it
what fractures most common
extremities
most common in what man and women ages
in men up to 45 years of age
in women over 45 years of age
before 75 years what fractures are most common
wrist
after 75 years what fractures are most common
hip
Bone fractures may be classified by four “either/or” classifications:
Position of bone ends after fracture
Completeness of the break
Orientation of the break to the long axis of the bone
Whether or not the bone ends penetrate the skin
Position of bone ends after fracture
Nondisplaced—ends retain normal position
Displaced—ends out of normal alignment
Completeness of the break
Complete—broken all the way through
Incomplete—not broken all the way through
Orientation of the break to the long axis of the bone
Linear—parallel to long axis of the bone
Transverse—perpendicular to long axis of the bone
Spiral or Oblique – on an oblique angle
Whether or not the bone ends penetrate the skin:
Compound (open)—bone ends penetrate the skin
Simple (closed)—bone ends do not penetrate the skin
All fractures can be described in terms of
Location
External appearance
Nature of the break
Comminuted fracture
Three or more bone pieces - high energy trauma
can require serious hardware to repair
Compression (crush) fractures
Fracture in spongy bone: result of compression (osteoporosis)
most common vertebrae
spiral or oblique fracture
Caused by violence transmitted through limb from a distance (twisting movements)
epiphyseal fracture
fracture at growth plate
depressed fracture
make a depression (shot in head, hammer to head)
Greenstick
Occurs in children: bones soft and bend without fracturing completely
Transverse fracture
Usually caused by directly applied force to fracture site
perpendicular to disaphysis
Functions of the X-ray
Localises fracture and number of fragments
Indicates degree of displacement
Evidence of pre-existing disease in bone
Foreign bodies or air in tissues
May show other fractures
MRI, CT or ultrasound to reveal soft tissue damage
how to handle fracturea
reduction
maipulation
traction
open reduction
– Allows very accurate reduction
risk of infection
Usually when internal fixation is Needed
Manipulation
closed reduction
usually with anesthesia
setting bone
traction
Fractures or dislocation requiring slow pulling resistance.
Closed Reduction
a procedure to set (reduce) a broken bone without surgery
holding reduction external fixation
4-12 weeks, used for fractures too unstable for cast, pins and frames
Internal fixation
Pins, nails, compression plates, screws, intramedullary rods
frame fixation
Allows correction of deformities by moving the pins in relation to the frame
Stages in the Healing of a Bone Fracture
Hematoma forms
Fibrocartilaginous callus forms
Bony callus formation
Bone remodeling
Hematoma forms
Torn blood vessels hemorrhage
Clot (hematoma) forms
INFLAMMATION - Site becomes swollen, painful, and inflamed
– lasts 6-8 hours after injury
Fibrocartilaginous callus forms
Phagocytic cells clear debris
Osteoblasts begin forming spongy bone within 1 week
Fibroblasts secrete collagen fibers to connect bone ends
Mass of repair tissue now called fibrocartilaginous callus
lasts about 3 weeks
Bony callus formation
New trabeculae form a bony (hard) callus
Bony callus formation continues until firm union is formed in ~2 months
Bone remodeling
In response to mechanical stressors over several months
Final structure resembles original
Osteoporosis
Loss of bone mass—bone resorption outpaces deposit
Spongy bone of spine and neck of femur become most susceptible to fracture
Risk factors
Osteoporosis risk factors
Lack of estrogen, calcium or vitamin D; petite body form; immobility; low levels of TSH; diabetes mellitus
Osteoporosis: Treatment and Prevention
Calcium, vitamin D, and fluoride supplements
increase Weight-bearing exercise throughout life
Hormone (estrogen) replacement therapy (HRT) slows bone loss
Some drugs (Fosamax, SERMs, statins) increase bone mineral density
