Chapter 6 slide A

Skeletal cartilage

the human skeleton initially consists of just cartilage which is replaced by bone, expect in areas requiring flexibility

Appositional growth

new matrix laid down on surface of cartilage

interstitial growth

new matrix within cartilage

functions of bones

support, protection, movement, mineral and growth factor storage, blood cell formation, triglycerides (fat) storage, hormone production

hematopoiesis

occurs in red marrow cavities of certain bones

osteocalcin

secreted by bones helps to regulate insulin secretion, glucose levels, and metabolism

axial skeleton

long axis of body, skull vertebral column, rib cage

appendicular skeleton

bones of upper and lower limbs, girdles attaching limbs to axial skeleton

long bones

longer than they are wide, limb bones

short boned

cube-shaped bones (in wrist & ankle), sesamoid bones form within tendons (patella), vary in size & number in different individuals

flat bones

thin, flat slightly curved, sternum, scapulae, ribs, most skull bones

Irregular bones

complicated shapes, vertebrae and hip bones

compact bone

dense outer layer on every bone that appears smooth and solid

spongy bone

made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae

trabeculae

open spaces between trabeculae are filled with red or yellow bone marrow

diaphysis

all long bone have a shaft, consist of compact bone surrounding central medullary cavity that is filled with yellow marrow in adults

epiphyses

extended end on our long bones, consists of compact bone externally and spongy bone internally (articular cartilage covers articular joint surface)

epiphyseal line

between diaphysis and epiphysis

epiphyseal plate

where bone growth occurs

periosteum

white double-layer membrane that covers external surface except joints

fibrous layer

outer layer consisting of dense irregular connective tissue consisting of Sharpey’s fibers that secure to bone matrix

osteogenic layer

inner layer abutting bone and contains primitive osteogenic stem cells that give rise to most all bone cells

endosteum

delicate connective tissue covering internal bone surface, line canals that pass through compact bone (have some stem cells)

osteogenic cells/ osteoprogenitor cells

mitotically active stem cells in periosteum and endosteum, when stimulated, they differentiate into osteoblasts or bone-lining cells

osteoblasts

bone forming cells

osteoblasts

bone-forming cells that secrete unmineralized matrix called osteoid, osteoid is made up of collagen and calcium- binding proteins, collagen makes up 90% of bone protein

osteocytes

mature bone cells that are surviving in these little spaces called lacunae

bone remodeling

osteoblasts and osteoclasts are seesawing back & forth

osteoclasts

bone break down

the functional unit of a compact bone is called

osteon

osteon

consist of an elongated cylinder that runs parallel to long axis of bone, acts as tiny weight-bearing pillars, consist of several rings of bone matrix called lamellae (contain fibers that run in different directions in adjacent rings)

central canal

run through core of osteon (blood supply and nerve supply)

perforating cancels

occur right angles to central canal (connect blood vessels and nerves to central canal)

canaliculi

osteoblasts that secrete bone matrix maintain contact with each other and osteocytes via cell projections with gap junctions

canaliculi

provides pathway for communication between bone cells

bone is made up of both

organic and inorganic components

osteoid

is secreted by osteoblasts consists of ground substance and collagen fiber, which contribute to high tensile strength and flexibility of bone

Hydroxyapatities (mineral salts)

makeup 65% of bone by mass (most of bone is hydroxyapatities which has a lot of calcium)