Skeletal System Part 1/5

Functions of bone

support, movement, protection, anchorage, mineral and triglyceride storage, blood cell formation, hormone production

Long bones

length greater than width

Short bones

almost equal length and width

Flat bones

very thin surfaces

Irregular bones

bones with complex shapes

Compact bones

solid and dense, external surface

Spongy bone

contain trabecules (open lattice of narrow plates), internal surface, contains bone marrow

Short, irregular, flat bone anatomy

thin layers of spongy bone locked within two layers of compact bone

Long bones 2

contain a shaft, bone ends and membrane

Epiphysis

enlarged regions at proximal and distal ends, covered in hyaline cartilage

Diaphysis

cylindrical shaft with marrow cavity, yellow bone marrow is covered by the medullary cavity

Epiphyseal line

region between diaphysis and epiphysis, has growth plate

Periosteum

covers external surface of bone, anchor for blood vessels, nerves, and tendons/ligaments, posses dense irregular connective tissue, fibrous outer membrane, osteogenic inner membrane (contain osteoblasts ad osteoclasts)

Endosteum

covers internal surface of bone, also has osteogenic layer

Osteoprogenitor cell

found in both periosteum and endosteum, differentiates into osteoblasts

Osteoblasts

secrete bone matrix containing collagen and calcium binding proteins, become osteocytes with matrix

Osteocytes

mature cells, maintain bone matrix, detect mechanical stress, communicate with osteoblasts and osteoclasts to remodel bone

Osteoclasts

bone dissolver, releases calcium ions, rough membrane allows for increased surface area

Osteon

structural unit of compact bone, contains lamellae and central canal, runs parallel to bone axis, bears weight

Lamellae

looks like growth rings of tree trunk, contains collagen fibers, fibers run in different directions to withstand strain

Lamellae - Central canal

contains blood vessels and nerves

Lamellae - Perforating canal

connects central canal to medullary cavity

Lamellae - Canaliculi

tiny canals that connect lacunae together and to central canal

Organic components

resists stretch, bone cells, osteoid (collagen, calcium binding proteins), approx. 1/3 of bone

Inorganic components

resists compression, mineral salts (calcium salts), approx. 2/3 of bone

Displaced vs. nondisplaced

position of the bone ends after fracture

Complete vs. incomplete fracture

completeness of the break

Open (compound) vs. Closed (simple)

penetration of bone ends through skin

Comminuted fracture

bone fragments into three or more pieces, more common in brittle bones

Compression fracture

bone is crushed, common in porous bones, subjected to extreme trauma, as in a fall

Spiral fracture

excessive twisting force applied to bone, common in sport injuries

Epiphyseal fracture

epiphysis separates from diaphysis along the epiphyseal plate, tends to occur where cartilage cells are dying and calcification of the matrix is occuring

Depressed fracture

broken bone portion is pressed inward, typical skull fracture

Greenstick fracture

bone breaks incompletely, one side of shaft breaks and the other bends, common in children where matrix is relatively more organic and flexible

Transverse fracture

breakage occurring in straight line across bone

Stress/hairline fracture

crack in bone

Oblique fracture

diagonal across bone

Impacted fracture

broken ends of bones are driven together