Bone Tissue Flashcards
Osteogenic cells
(aka osteoprogenitor) cells mitotically active stem cells in perio/endo-steum
- differentiate into osteoblasts
osteoblasts
secrete bone matrix (osteocalcin and osteopontin), mineralizes bone
- responsible for bone growth
osteocytes
mature bone cells (lie in lacunae)
- monitors and maintains bone matrix
- stress/strain sensors communicate to osteo-blasts/clasts
Osteoclasts
responsible for bone resorption
- reabsorbs and breaks down bone
- ruffled border inc. surface area for enzyme degradation
-phagocytic
osteoid cells
bone lining cells; help maintain unmineralized bone matrix
-secreted by osteoblast
Bone surfaces
external: periosteum
internal: endosteum
Bone Shape Classifications
long bones (humerus/femur)
short bones (carpals/tarsals)
flat bones (skull/rib)
irregular bones (vertebrae/coccyx)
Two bone groups
axial skeleton: skull, vertebral column, rib cage
appendicular skeletons: upper and lower limbs (includes girdle attachments)
Functions of bone
1) support
2) protect
3) movement
4) mineral/growth factor storage
5) hematopoiesis
6) triglyceride (fat storage)
7) hormone production (osteocalcin)
Bone Textures
Compact bone (cortical)
- Dense outer layer
Spongy (trabecular)
- Trabecula- structural units (honeycomb)
Medullary Cavity
contains yellow marrow
Anatomy of Long bones
- diaphysis is the shaft of the long bone.
- epiphyses are the ends of the bone, that articulate with adjacent bones.
- metaphyses are the areas between the epiphysis and diaphysis.
- Hyaline cartilage (articular cartilage) at the ends of the bones
Periosteum
- double layer membrane
- Covers external surfaces except joint surfaces
- dense irregular CT
- Many nerve fibers and blood vessels
- Anchoring points for tendons and ligaments
Endosteum
Delicate connective tissue membrane covering internal bone surface
- Covers trabeculae of spongy bone
- Lines canals that pass through compact bone
Contains osteogenic cells
Perforating (Sharpey’s) fibers
secure periosteum to bone matrix
Osteogenic layer
inner layer of the periosteum
- Contains primitive stem cells- osteogenic cells
Red marrow
Hematopoietic tissue (adults have less centers than children)
- Found in:
Diploë of spongy bone, head of long bone, trabecular cavities
Spongy bone of newborns/infants/children
Compact bone
interstitial lamellae fills gaps between forming (incomplete) osteons
- bony matrix is solidly filled
- Resist twisting of long bone
Spongy bone
Trabeculae (structural unit)
- Align along lines of stress to help resist it
- No osteons
- Contain irregularly arranged lamellae and osteocytes interconnected by canaliculi
- Capillaries in endosteum supply nutrients
Osteomalacia
Bones poorly mineralized
- Calcium salts not adequate (Vit.D deficiency)
- Soft, weak bones
- adults
Rickets
- Bowed legs and other bone deformities
- Bones ends enlarged and abnormally long
- children
Cause: Vitamin D deficiency or insufficient dietary calcium
Osteoporosis
Group of diseases
- Bone resorption outpaces deposit
- Sex hormones maintain normal bone health and density; secretion wanes with age
Paget’s disease
Excessive and haphazard bone deposit and resorption
- Bone made fast and poorly – called pagetic bone
- Very high ratio of spongy to compact bone and reduced mineralization
circumferential laminae
layers of bone matrix that extend around entire surface of diaphysis
