SKELETAL SYSTEM
A. Explain the functions of the skeletal system
1. Provide support to soft tissue
2. protects tissues and organs (internal organs; CNS)
3. movement (in assoc. with skeletal muscle)
4. storage (houses more than 90% of Ca and Phosphate)
5. hematopoietic stem cell production (produces all blood cells)
B. Describe the major divisions of the skeletal system
1. Axial Skeleton
Forms central portion of skeleton (skull, thoracic cage, vert column)
2. Appendicular Skeleton
Appendages, extremities (pectoral and pelvic girdles, upper and lower limb)
C. Discuss general bone features
1. General Bone Shapes
a. long bones (greater length than width)
humerous
b. short bones (cube shape; length and width about same)
tarsus of foot
c. flat bones (thin ; consist of nearly two parallel layers compact bone surround spongy bone layer)
sternum, skull
d. irregular bones (all diff. shapes and unusual projections)
vertebral bones
e. sesmoid bones (small, found in certain tendons) ((patella))
2. Anatomy of a long bone
a. Diaphysis:
shaft of long bones (hollow)
b. Epiphysis:
ends of the long bone (2 of them; proximal is closer to body, distal farther away)
c. Metaphysis
growth plate; in between above sections
d. Epiphyseal line
e. Medullary cavity
filled with yellow bone marrow
f. Endosteum
cellular membrane lining the medullary cavity
g. Periosteum
outside cellular membrane w dense connective tissue
osteogenic cells for growth and repair
h. Articular cartilage
function with synovial joint
3. Cells of Bone
A. osteoprogenitor
stem cells that produce cells that become osteoblasts
lays down osteoid which is calcified; make new bone
osteoblasts mature into osteoctes
b. osteoblasts
lay down matrix of osteoid
c. osteocytes
mature osteoblasts that have covered themselves in their own matrix; stay in lacunae
d. osteoclast
secretes hydrochloric acid and lysosomes that dissolve calcified bone matrix to break down
bones
4. Bone Tissues
a. Compact bone
dense and solid; present on bone surface; have osteon/haversian system
b. Spongy bone
trabecular; similar to a sponge; primarily found sandwiched btwn compact bones and flat bones,
and in epiphysis of long bones
D. Discuss the formation of bone
1. Bone Ossification
a. Intramembranous ossification:
occurs when osteoblasts produce bone matrix in specific mesenchymal tissue locations
flat bones of skull (mandible, facial bones)
begins w forming of ossification centers within regions of thickened mesenchyme
commits cells to become osteoprogenitor cells
become osteoblasts; lay down matrix that gets calcified
will eventually form unorganized woven bones, replaced by lamellar bone
compact bone replaces woven bone on external edges, spongy bone will
form in between
b. Endochondral ossification:
formation of new bone from hyaline-cartilage models
present in most of body esp long bones
hyaline cartilage model forms btwn weeks 8-12
bone center forms; chondrocytes begin to hypertrophy, and cartilage matrix starts to calcify
as it calcifies, blood vessels penetrate and osteoblasts lay down periosteal bone collar
primary ossification center forms in center of future diaphysis
where calcified cartilage present, acts as a model for new osteoblasts to deposit newly formed
osteoid
sec. ossification centers then form in epiphyses in same way as primary oss. centers
cartilage then replaced by expanding bone development
hyaline remains on ends as articulating cartilage and in between primary/secondary
ossification centers
this cartilage will be epiphyseal plate and will make chondrocytes to lengthen
the bone, until it is ossified
2. Bone Growth
a Interstitial growth:
process by which bones grow longer
because of the epiphyseal plate, and the cartilage inside
b. Appositional growth:
growth or increase in bone diameter (new bone added to the surface)
osteoblasts present in periosteum add layers of new bone to layers of existing bone
bone near medullary cavity is absorbed by osteoclasts
E. Discuss the blood supply and innervation to bones
1. Nutrient artery
Pierces the diaphysis and supplies medullary cavity
2. Epiphysial artery
Supplies ends of bones
3. Metaphysial artery
Supplies connection of area btwn diaphysis and epiphysis
4. Innervation
Sensory nerves supplied to bone (bone injury)
To blood vessels to control vasomotor functions of blood vessels
5. periosteal
Supplies periosteum