bone classifications and histology

sesamoid bone

bone encased in a tendon (patella, pisiform)

long bone

almost all limb bones

short bones

carpals, tarsals, sesamoids

flat bone

scapulae, ribs, cranial bones

irregular bones

vertebrae, os coxa

bone functions

protection, support, movement, blood cell formation (hematopoiesis), mineral storage (calcium and phosphate)

skeleton tissue types

spongy, compact, cartilage, periosteum, yellow marrow, red marrow

spongy tissue

internal

compact tissue

external

cartilage

hyaline/elastic/fibro

periosteum

lots of nerve fibers, dense irregular CT

yellow marrow

adults → fat, kids → starts as red, energy storage

red marrow

makes RBCs

how does bone bend?

collagen protein fibers woven throughout bone to give flexibility, bonds holding collagen fibers can break then reform for extra flexibility

organic components

1/3 of total matrix cells and osteoid

osteoid

ground substance, proteoglycans and glycoproteins to increase water content, collagen for tensile strength, comes from osteoblast

inorganic components

2/3 of total matrix, calcium phosphate salts, provide stiffness and durability, balance between organic and inorganic

cell responsible for making the matrix

osteoblast

cell maintains the bone matrix

osteocyte

cell reabsorbs the bone matrix

osteoclast

cells found in membranes and produce new cells

osteogenic

compact bone

dense layered bone, found on outside of all bone

osteon (haversian system)

structural unit of compact bone

osteon components

central canal (for blood vessels and nerves, lined with endosteum), lamellae (collagen and calcium phosphate), osteocytes (in lacunae between lamella, connected via canaliculi, gap junctions, no diffusion in matrix, pass nutrients and waste)

spongy bone functions

lighter than compact, carefully aligned trabeculae to support bone in exact lines of stress

trabeculae

interconnecting rods or plates of bone, only in spongy bone

in spongy bone there is no central blood vessels, so nutrients are passed through ___

canaliculi

long bone parts

diaphysis, epiphysis, epiphyseal line, periosteum, endosteum, articular cartilage, hematopoietic tissue

diaphysis

“shaft”, collar of compact bone, medullary cavity with yellow marrow

epiphyses

“ends”, shell of compact bone, interior spongy bone

epiphyseal line

growth plate, separates diaphysis/epiphyses, hyaline cartilage while growing, replaced with bone → line

periosteum

outer lining of bone, outer layer = connective tissue, inner layer = cells, osteoblasts/clasts/genic cells, tensile strength, entry for blood vessels/nerves, connections for tendons/ligaments

endosteum

CT inside of bone, blasts and clasts

articular cartilage

cap on end of bone for joint

hematopoietic tissue

bone cell formation tissue, in spongy bone of flat/irregular bones, medullary cavity of epiphyses long bones, babies: medullary cavity of diaphysis in long bones

anatomy of flat/short/irregular bone

peri → compact → endo → spongy → endo → compact → peri