Chapter 6: Skeletal System

cartilage

embryonic precursor of most bones and covers many joint surfaces

ligaments

hold bone to bone at joint

tendons

attach muscle to bones

functions of the skeleton

support, movement, protect delicate organs, blood formation in marrow, electrolyte balance, acid-base balance, detoxification

the study of bone

osteology

calcification

the process of hardening

tissues present in the bone

blood, bone marrow, cartilage, adipose tissue, nervous tissue, fibrous CT

bone shapes

flat, long, short, irregular, sesamoid

osteogenic cells

stem cells

osteoblasts

bone-forming cells

osteocytes

mature bone cells, contribute to bone maintenance

osteoclasts

bone-dissolving macrophages

lacunae

cavities that house osteocytes

canaliculi

small canals that connect lacunae

bone matrix

one-third organic, two-thirds inorganic

what travels in the canals of compact bone?

blood vessels and nerves

concentric lamellae of an osteon

onion layer surrounding the central canal of an osteon

circumferential lamellae

layer of the bone matrix just surrounding the border

spongy bone

porous appearance, lightweight but strong

spicules

rods and spines of bone

trabeculae

thin plates of bones

red marrow

bone marrow that produces red blood cells, white blood cells, and platelets - axial and pelvic bones

yellow marrow

mainly fat - long bones of limbs

ossification

bone formation

intramembranous ossification

produces flat bones of skull and most of clavicle - develops in a fibrous sheet resembling the dermis

endochondral ossification

bone develops from hyaline cartilage model - most bones form this way

how do bones grow long?

bones grow longer at the epiphysial plates made of hyaline cartilage

appositional growth

growth in diameter and thickness

bone remodeling

Wolff’s Law states that bone adapts to the loads under which it is placed, leading to changes in bone structure.

calcium and phosphate

raw materials for calcified ground subtance

vitamin A

promotes formation of glycosaminoglycans

vitamin C

promotes collagen cross-linking adding stiffness

vitamin D

necessary for calcium absorption by small intestine and reduces urinary calcium loss

calcitonin

secreted by thyroid gland, stimulates osteoblasts in children and pregnant women

growth hormone

promotes intestinal absorption of calcium, stimulates growth plates and bone elongation

estrogen and testosterone

stimulate ling bone growth during adolescence

parathyroid hormone

secreted by parathyroid glands, stimulates bone reabsorption to boost levels of calcium in the blood

osteopenia

loss of bone, fractures are more common and heal slower

stress fracture

caused by adding abnormal stress of trauma to a normal healthy bone

pathological fracture

occurs when putting a normal amount of stress on a weakened or abnormal bone

how are fractures classified?

breaking of skin, direction of fracture, separation of bone pieces

closed

skin is not broken

open

skin is broke, bone protruding through skin

complete

bone is broken in two or more pieces

incomplete

partial fracture; some pieces remain joined

nondisplaced

portions of bone are still in correct anatomical alignment

displaced

portions of bones are out of anatomical alignment

comminuted

bone is broken into three or more pieces

greenstick

bone is bent toward one side and has an incomplete fracture on the opposite side

what are the 4 stages of bone healing?

hematoma formation, soft callus formation, hard callus formation, bone remodeling

osteoperosis

bone loss mass and become subject to pathological fractures

how is osteoperosis treated and prevented?

treated with parathyroid hormones, prevented with weight-bearing exercises, adequate calcium and protein

osteosarcoma

bone cancer affecting especially the limb bones of adolescents and young adults.