Bones

Where are axial bones located?

These are unpaired bones. For example, skull, vertebral column, and sacrum.

Where are appendicular bones located?

These are paired bones that make up the limbs and their associated girdles.

Compact bone

Lines the outside of all bones and is fairly thick in long bones (in the medullary cavity)

Trabecular bone

Spongy or cancellous bone

Lines the inside of medullary cavities. Forms the metaphyses/epiphyses and inside of other bones.

Shock absorbers

Subchondral bone

Thin layer of bone just at the joint articular surfaces that lies under the hyaline cartilage of a joint

Highly vascularized

Diaphysis

The shaft

Epiphyses

The ends of the bones that have the joint

Metaphysis

The flared end of the diaphysis where the growth plate lies

Epiphyseal plate

Growth plate between metaphysis and epiphysis

Medullary cavity

The hollow cylinder in long bones that contains marrow

Articular surface

Joint surface that is covered by hyaline cartilage

Periosteum

Thin vascular connective tissue layer that envelops the external surface of the bone

Endosteum

Similar to the periosteum but lines the internal surface of the bone

Osteon

Basic microscopic unit of bone

Lamellae

Concentric rings of bone

Haversian canal

Central canal running vertically in the center of osteon. Has blood supply.

Vokmann’s canal

Horizontal blood vessels connecting the Haversian canals

Sharpey’s fibers

Fibers that connect the periosteum to the bony surface

Osteoblasts

Bone builders

Osteocytes

Bone maintenance cells

Osteoclasts

Bone resorbers. Large. Multinucleate

Forms of ossification

1. Intramembranous ossification

2. Endochondral ossification

Intramembranous ossification

Bone forms directly from mesenchymal cells between the two layers of membranes

Bones that form: cranial vault, facial skeleton, clavicles

Endochondral ossification

There is a hyaline cartilage model of the bone first, which is then replaced by bone

Longitudinal growth

Growth in length, makes you taller

Appositional growth

Growth in diameter (required as bones get longer to keep relative strength)

Phases of fracture healing

Reactive phase

Reparative phase

Remodeling phase

What occurs in the reactive phase of fracture healing?

Fracture and inflammatory phase

Blood is brought to area, creating a hematoma

Get some granular tissue formation

What occurs in the reparative phase of fracture healing?

Cartilaginous callus is formed to stabilize the fractured ends, then begin to be replaced by bone

What occurs in the remodeling phase of fracture healing?

Lamellar bony callus is remodeled bringing the bone closer to its original shape

Process of endochondral ossification

1. Cartilaginous model

2. Osteoblasts create bony collar

3. Blood vessels invade, bringing in more osteoblasts. Ossification centers begin.

4. Cartilage is replaced. Growth plate is retained during longitudinal growth.

5. Eventually bone cells outpace the cartilage cells and epiphyses fuse.