Unit 5: Skeletal System Terms

long bones

greater in length than width, with long shaft

short bones

somewhat cube shaped; nearly equal in length and width

flat boens

generally thin; extensive surface for muscle attachment; provide considerable protection

irregular bones

complexly shaped bones

sesamoid bones

protect tendons from wear and tear

diaphysis

long cylindrical, main portion of the bone

epiphysis

distal and proximal ends of the bone

metaphysis

regions in mature bone where epiphysis meets the diaphysis

epiphyseal plate

layer of cartilage that is being replaced by bone allowing bone to grow in length

epiphyseal line

the bone which has replaced the cartilage found inside a bone when growth stops

articular cartilage

reduces friction/absorbs shock

spongy bone

• contains red marrow; found in hip bones, ribs, breast bones, vertebrae, and theends of long bones

• spaces within the spongy bone is filled with red bone marrow (blood cell production)

trabeculae

• irregular latticework of then columns of bone

• spaces between filled with red bone marrow → site of hematopoiesis

• contain osteocytes which lie in lacunae

• make up most flat, short, and irregularly shaped bones

• found in the epiphysis of long bones

compact bone

• contains few spaces

• external layer of all bones of the body and the bulk of the body of long bones

• provides protection/support/ resistance to stress

marrow cavity

space within the diaphysis which contains fatty yellow marrow in adults

periosteum

• tough sheath of dense irregular connective tissue; surrounds the bone surface

• protects

• assists in fracture repair

• helps nourish bone

• serves as point of attachment for ligaments/tendons

Endosteum

lines the surface of marrow cavity, contains bone forming cells that contribute to growth in width of the bone

fossa

shallow, hollow depression in a bone which serves a socket or attachment point for other boxes, muscles or organs

process

a bony outgrowth, projection, or raised area of a bone where other muscles, tendons or ligaments can attach

head

the smooth, rounded, ball-like top of a bone which forms a joint with other bones

condyle

a rounded protuberance at the end of a bone which forms a smooth surface which is articulated with another bone

foramen

a natural opening, hole, or passage within a bone which allows vital structures such as nerves, blood vessel,s or the spinal cord

protuberance

a rounded or raised projection of a bone surface which serves as a site of attachment for muscles, tendons, or ligaments

tubercle

small rounded bump of a bone, provides a small attachment point

meatus

canal-like passageway through a bone, allowing the passage of air, nerves, or other structures

osteogenic cell

unspecialized stem cells which divide into cells that develop into osteoblasts

osteoblasts

bone building cells; do not divide

• synthesize and secrete collagen

• initiate calcification

• found on the surface of the bone

• as they secrete matrix materials they become trapped in their secretions and become osteocytes

osteocytes

• principal cells of bone tissues

• no longer secrete matrix materials

• maintain cellular activities of bone tissue such as exchange of nutrients and wastes with blood

osteoclasts

• huge cells found in bone which release powerful lysosomal enzymes that function in the destruction of bone matrix (resorption)

• important during bone fractures

• matches pace of osteoblasts

bone reabsorption

• part of normal development, growth, and repair of bone

• ensures bone cells never become too old or injured

• continuous replacement of old bone tissue with new

volkmann’s canals

locations where blood/lymph vessels and nerves from periosteum penetrate transversely through width of bones (perpendicular to length of bone)

• connects aversion systems

• connects with periosteum, medullary cavity and central (haversian) canals

haversian/central canals

extend vertically, lengthwise through the bone

concentric lamellae

rings of hard calcified matrix surrounding central canals

lacunae

small spaces between lamellae that contain osteocytes

canaliculli

tony channels that project in all direction from the lacunae

• provide routes for nutrients and oxygen to reach the osteocytes and wastes to be removed

osteon/haversian system

a central canal with its surrounding lamellae, lacunae, and canaliculli

bone remodeling

rate of ossification = rate of reabsorption

thyroid gland

control center for hormonal feedback loop for bone remodeling

calcitonin

hormone released during bone remodeling feedback loop which increases ossification

parathyroid hormone

hormone released during bone remodeling feedback loop which increases bone reabsorption

compound fracture

fracture where end of bones protrudes through the skin

comminuted fracture

fracture where bone splinters/fragments between the two main fragments

greenstick fracture

partial fracture; one side breaks and the other bends

spiral fracture

fracture where a bone breaks in half by a twisting force or impact

transverse fracture

fracture where bone breaks straight across

oblique fracture

fracture where bone is broken at an angle

displaced fracture

fracture where bone breaks and moves out of alignment

nondisplaced fracture

fracture where bone breaks but does not move out of alignment

closed fracture

fracture where skin is not broken

stress fracture

a very thin crack, also called a hairline fracture

fibrous/synarthrosis joint

joint where bones are fused together and immovable

• bones held together by fibrous connective tissue rich in collagen

• ex. teeth, sutures of the skull

cartilaginous/amphiarthrosis joint

joint where cartilage is found between ends of bones (but no other space exists) →joint is semi-movable

• ex. sternum, spine

synovial/diarthrosis

freely movable joint →joint has space containing synovial capsule

• ex. knee

ligament

tough bands of connective tissue that attach bone to bone

• allows movements in proper direction and prevents movement in improper direction

tendon

tough bands of connective tissue that connect muscle to bone

• found at all synovial joints

• muscles don’t attach to bone directly

synovial fluid

• secreted by cells in the synovial membrane

• reduces friction/lubricates

bursae

saclike structures found near joints and other point of friction (where tendon crosses bone)

• filled with fluid which allows cushioning

meniscus (articular discs)

pads of fibrocartilage (cartilage that contains numerous thick bundles of collagen fibers) that lie between the articular surfaces of bone

articular capsule

a fibrous tissue envelope surrounding a synovial joint

hinge joint

angular open-closing motion joint

• ex. knee joint, elbow

pivot joint

"joint allowing rotation around a central axis

• “peg in a hole”

• ex. atlantoaxial joint (allows head to move side to side)

planar joints

joint where 2 opposed flat surfaces that glide over each other

• allows side to side and back and forth gliding

• ex. articular facets do the vertebrae; intercarpal/tarsal joints

ball and socket joint

joint where ball-like surface of one bone fits into the cup-like depression of another bone

• allows wide range of motion

• ex. hip or shoulder joint

strain

damage to muscle or tendon

sprain

twisting/wrenching of a joint that stretches or tears its ligaments but does not dislocate the bone

• may damage blood vessels, muscles, tendons, and nerves

• considerable swelling

dislocation

displacement of a bone from a joint with tearing of ligaments, tendons, and articular capsule causing:

• pain, joint instability, reduced muscle strength, difficulty moving joints/stiffness

subluxation

partial dislocation

avulsion

unattaching fragment of bone

hyperextension

movement of a joint beyond its normal, healthy range of motion