Bone Tissue

Osteocytes

mature bone cells trapped in matrix that sit in a lacuna

Canaliculi

Hairlike canals that connect lacunae to each other and the central canal

Lacunae

small cavities in bone that contain osteocytes

Osteoblasts

Bone building cells

Osteoclasts

large cells that resorb or break down bone matrix

osteomalacia

disease marked by softening of the bone caused by calcium and vitamin D deficiency

osteporosis

loss of bone density caused by excessive absorption of calcium from bone

Hydroxyapatite

Hardy crystals consisting of calcium and phosphate that form the bone matrix.

Osteoid

unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

osteogenic cells

stem cells that differentiate into osteoblasts

Osteon

structural unit of compact bone

Lamellae

Concentric rings made up of groups of hollow tubes of bone matrix

Haversian (central) canal

central channel containing blood vessels and nerves

Volkmann's canals

channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal

interstital lamellae

fill gaps between forming osteons

concentric lamellae

layers of bony matrix around a central canal

circumferential lamellae

located deep to periosteum and superficial to endosteum and extend around entire circumference of the diaphysis and resist twisting of long bone

Periosteum

A dense fibrous membrane covering the surface of bones (except at their extremities) and serving as an attachment for tendons and muscles.

Endosteum

lines the medullary cavity

medullary cavity

cavity within the shaft of the long bones filled with bone marrow

Diaphysis

shaft of a long bone

Epiphysis

End of a long bone

hyaline cartilage

Most common type of cartilage; it is found on the ends of long bones

Epihyseal plate

Growth plate located at the ends of long bones.

spongy bone

composed of small needle-like pieces of bone and lots of open space. irregularly spaced lamella and no osteons

axial bones

Skull, rib cage, and spine

appendicular skeleton

Bones of the limbs and limb girdles that are attached to the axial skeleton

long bones

longer than they are wide

short bones

carpals and tarsals

sesamoid bones

round bones found near joints

irregular bones

bones of the vertebrae and face

flat bones

thin, flattened, and usually curved

pneumatic bones

sinus-containing bones (i.e., frontal bone)

trabeculae

supporting bundles of bony fibers in cancellous (spongy) bone

yellow marrow

soft, fatty material found in the medullary cavity of long bones

red marrow

produces blood cells

Ossification

process of bone formation

Calcification

process that hardens bones by adding calcium phosphate and collagen

intramembranous ossification

process by which bone forms directly from mesenchymal tissue (flat bones of skull, and clavicle)

endochondral ossification

Process of transforming cartilage into bone.

primary ossification center

region, deep in the periosteal collar, where bone development starts during endochondral ossification

secondary ossification center

this develops in the epiphyses of bone during endochondral ossification

ossification center

cluster of osteoblasts found in the early stages of intramembranous ossification

mesenchymal cells

stem cells that differentiate into osteoblasts

Fontanels

Gaps between a baby's skull that slowly close up during the first 18 months of life

zone of proliferation

Within the epiphyseal plate, which zone houses actively dividing cartilage cells on the epiphyseal plate side

zone of ossification

ossification at diaphyseal side of plate

appositional growth

increase in bone thickness

metaphyseal vessels

-supply the epiphyseal cartilage

epiphyseal vessels

Supply nutrients to the cavities of the epiphysis

periosteal vessels

blood to superficial osteons

secondary ossification centers

parathyroid hormone

increases blood calcium levels by activating osteoclasts

thyroid gland

secretes calcitonin to decrease calcium levels by activating osteoblasts

comminuted fracture

fracture in which the bone is splintered or crushed

compression fracture

bone is crushed

spiral fracture

a fracture in which the bone has been twisted apart

epiphyseal fracture

a break at the location of the growth plate, which can affect growth of the bone

depressed fracture

broken bone portion is pressed inward

greenstick fracture

bending and incomplete break of a bone; most often seen in children

fracture hematoma

blood clot that forms at the site of a broken bone

internal callus formation

blood vessels grow into clot in hematoma

external callus

collar of hyaline cartilage and bone that forms around the outside of a fracture and will be eventually replaced by bone

bony callus

this forms during fracture repair when the fibrocartilage is converted to spongy bone; lasts 3-4 months