Chapter 7- Bone Growth + Breaks

ossification

formation of bone

intramembranous ossification

spongy bone forms between 2 sheets of fibrous connective tissue, forms bones of skull

secreted osetoid

uncalcified bone, traps osteoblasts, becomes osteocytes

endochondral ossification

most bones of body, h cartilage models are replaced by spongy bone, then compact bone, takes longer

cartilage remodeling

does not become bone, is replaced by it

endochondrial 1

mesenchymal cells differentiate into chondrocytes

chondrocytes

cartilage model of bony skeleton + perichondrium

perichondrium

envelops cartilage

endochondrial 2

capillaries penetrate cartilage, perichondrium transforms into periosteum, primary ossification center

endochondrial 3

cartilage + chondrocytes continue to grow at ends

endochondrial 4

secondary ossification center

endochondrial 5

cartilage remains at epiphyseal plate at joint surface as articular cartilage

growth at epiphyseal plate

diaphysis is separated by epiphyseal plate, cartilaginous cells form 4 layers

cartilage zones

resting cartilage, proliferating cartilage, hypertrophic cartilage, calcified cartilage

zone of resting cartiage

closest to end, anchor plate to epiphysis

zone of proliferating cartilage

rows of young cells, mitosis

zone of hypertrophic cartilage

rows of older cells, thicker epiphyseal plate, lengthens bone, matrix calcifies, cartilage cells die

zone of calcified cartilage

thin layer of dead cells + matrix

epiphyseal plate

band of h cartilage in epiphysis in long bones, grows in length until plate is ossified

epiphyseal side

cartilage formed

diaphyseal side

cartilage ossified

appositional growth

bone diameter

remodeling

bone replaced (10-20%) annually, opposing processes of deposition + resorption

hormones regulating bone growth

parathyroid, calcitonin, growth hormone

parathyroid hormone

manages calcium blood levels, stimulates osteoclasts

calcitonin

opposes parathyroid hormone

growth hormone

stimulates cartilage cell division, deficiency leads to pituitary dwarfism, excess in gigantism, acromegaly

proper levels of calcium

prevent osteoporosis

affects bone

nutrition, sunlight, hormones, exercise

vitamin D

calcium, deficiency causes rickets, oestomalacia

vitamin A

osteoblast + osteoclast activity, deficiency retards bone

vitamin C

collagen synthesis, deficiency makes slender, fragile

thyroid hormone

replacement of cartilage with bone

sex hormones (estrogen, testosterone)

bone formation

fractures

traumatic (injury), spontaneous (disease)

breaks

simple, compound, complete, incomplete, impacted, spiral

simple break

fracture protected by skin

compound break

fracture is visible through skin

complete break

bone is broken through entirely

incomplete break

not in two parts

impacted break

broken ends wedged into each other

spiral break

ragged break due to twisting bone