Chapter 5-The Skeletal System; Sami Knaus


from the Greek word meaning "dried-up body"; system consists of bones, joints, cartilages, and ligaments.

axial skeleton

the bones that form the longitudinal axis of the body.

appendicular skeleton

the bones of the limbs and girdles.

compact bone

dense and looks smooth and homogeneous.

spongy bone

composed of small needlelike pieces of bone and lots of open space.


formation of blood cells

long bones

typically longer than they are wide; have a shaft with heads at both ends; mostly compact bone; all bones of the limbs except wrist and ankle bones.

short bones

generally cube-shaped and contain mostly spongy bone; bones of wrist and ankle, patella (sesamoid)

flat bones

thin, flattened, usually curved; two thin layers of compact bone sandwiching a layer of spongy bone between them; skull, ribs, sternum.

irregular bones

Do not fit into any of the other bone categories, made up of both spongy and compact bone; vertebrae and hip bones.


shaft of a long bone, makes up most of its length.


covers and protects diaphysis, fibrous connective tissue membrane.

Sharpey's fibers

secure the periosteum to the underlying bone


end of a long bone; thin layer of compact bone enclosing an area filled with spongy bone.

articular cartilage

covers external surfaces of epiphyses; glassy hyaline cartilage that provides smooth, slippery surface to decrease friction at joint surfaces.

epiphyseal line

remnant of epiphyseal (growth) plate

epiphyseal plate

growth plate; flat plate of hyaline cartilage seen in young, growing bones. lengthwise growth of a long bone, replaced by bone by end of puberty.

medullary cavity (yellow marrow)

cavity inside the shaft where adipose tissue is stored in adults; forms blood cells in infants

red marrow

confined to the cavities of spongy bone of flat bones and the epiphyses of some long bones


mature bone cells


small cavities in bone that contain osteocytes


concentric circles of lacunae

Haversian canal

one of a network of tubes running through compact bone that contains blood vessels and nerves


central canal and matrix rings consisting of Haversian canals (Haversian system)


tiny canals, radiate outward from the central canals to all lacunae; form a transport system that connects all the bone cells to the nutrient supply through the hard bone matrix.

Volkmann's canals

run into the compact bone at right angles to the shaft.


large, rounded projection; may be roughened


Narrow ridge of bone; usually prominent


very large, blunt, irregularly shaped process. (The only examples are on the femur)


Narrow ridge of bone; less prominent than a crest


small, rounded projection or process.


Raised area on or above a condyle

spine (of bone)

sharp, slender, often pointed projection


any bony prominence

head (of bone)

bony expansion carried on a narrow neck


smooth, nearly flat articular surface


rounded articular projection


armlike bar of bone


canal-like passageway


Cavity within a bone, filled with air and lined with mucous membrane


Shallow, basinlike depression in a bone, often serving as an articular surface




narrow, slitlike opening


round or oval opening through a bone


process of bone formation


bone-forming cells

articular cartilages

cover the bone ends at movable joints

appositional growth

Growth by forming new layers on the surface of pre-existing layers; process of increasing in thickness rather than length.

comminuted fracture

bone breaks into many fragments; particularly common in the aged, whose bones are more brittle

compression fracture

bone is crushed; common in porous bones (i.e., osteoporotic bones)

depressed fracture

broken bone portion is pressed inward; typical of skill fracture

impacted fracture

broken bone ends are forced into each other; commonly occurs when one attempts to break a fall with outstretched arms.

spiral fracture

ragged break occurs when excessive twisting forces are applied to a bone; common sports fracture.

greenstick fracture

bone breaks incompletely, much in the way a green twig breaks; common in children, whose bones are more flexible than those of adults.


giant bone-destroying cells


excessive calcium in the blood


(bruise) mass of clotted blood showing through skin


cartilage that contains fibrous bundles of collagen, such as that of the intervertebral disks in the spinal cord.

bony callus

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

primary curvatures of spine

spinal curvatures in the thoracic and sacral regions; present when we are born.

secondary curvatures of spine

develop after birth, cervical curvature and lumbar curvature


Areas where two or more bones join together


a cord of fibrous tissue that connects bones


an immovable joint


a slightly movable joint


a freely movable joint


The connecting fibers are longer than those of sutures; thus the joint has more "give"; joint connecting distal ends of tibia and fibula


flattened fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid; bags of lubricant that act like ball bearings to reduce friction between adjacent structures during joint activity; common where ligaments, muscles, skin, te

plane joint

the articular surfaces are essentially flat, and only short slipping or gliding movements are allowed; nonaxial movements; intercarpal joints of the wrist

hinge joint

the cylindrical end of one bone fits into a trough-shaped surface on another bone; uniaxial; elbow joint, ankle joint, joints b/w phalanges of fingers

condyloid joint

Knuckle-like"; The egg-shaped articular surface of one bone fits into an oval concavity in another; allow the bone to move from side to side and back and forth; biaxial; knuckle joints

saddle joint

each articular surface has both convex and concave areas; biaxial; carpometacarpal joints in thumb

ball-&-socket joint

head fits into socket; movement in all axes; shoulder, hip


inflammation of the joints


the most common form of arthritis; chronic degenerative condition that typically affects the aged. affects articular cartilages

rheumatoid arthritis

chronic inflammatory disorder; onset is insidious and usually occurs b/w age 40 and 50; autoimmune disease


a disease in which uric acid (a normal waste product of nucleic acid metabolism) accumulates in the blood and may be deposited as needle-shaped crystals in the soft tissues of joints.


an increased softening of the bone resulting from a gradual decrease in rate of bone formation; a common condition in older people.