bone tissue and the skeletal system

hematopoiesis

• blood cell formation

• happens in marrow

adult

yellow marrow (long bones)

kids

red marrow

axial

• core, everything down the center

• skull, vertebral column, sternum, ribs

appendicular

• shoulder, girdle, upper limbs, pelvic girdle, lower limbs

osteogenic cells

undifferentiated cells that develop into osteoblasts.

osteoblasts

• blasts, build, bone

• deposit mineral into bone (pulled from blood)

• maintain bone

osteoclasts

breakdown bone, puts minerals back into blood (resorption)

periosteum

outer surface of bone

endosteum

lines medullary cavity

osteon

unit of compact bone

spongy bone

• composed of trabeculae that contains osteocytes

• red marrow fills space

• located in the epiphyses of long bones, ribs, vertebra, + skull bones

red marrow

flat bones, epiphyses of femur + humerus

yellow bone marrow

medullary cavity of long bones

sesamoid

patella (knee cap) bone that grows in a tissue (stress response)

short bones

carpals + tarsals

flat bones

protection

intramembranous

bone develops from mesenchyme

• flat bones (skull, clavicles)

• fontanels (soft spots on a baby’s skull)

endochondral

bone replacing hyaline cartilage

• all other bones

thyroid gland

calcitonin hormone “tones it down”

• stimulates blasts + decreases blood Ca+ levels

parathyroid gland

PT hormone

• works with kidneys + calcitonin

osteoporosis

decreased bone density can lead to bone fractures

epiphyseal plates

visible in growing bone

epiphyseal line

remnants of epiphyseal plates in mature bone