The Skeletal System

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the skeletal system includes
bones, joints, cartilages, and ligaments
the 2 subdivisions of the skeleton are
axial and appendicular
the axial skeleton includes
the bones of the longitudinal axis: the skull, vertebral column, and the bony thorax
the appendicular skeleton includes
the bones of the appendages and girdles: limbs and the pectoral and pelvic girdle
5 functions of the bones
support, protection, framework for movement, storage, hematopoiesis
what bones serve the function to protect?
skull, ribs, vertebrae
explain the function of storage
calcium (nerve impulses, muscle contraction, and blood clotting), phosphorus, and fat (yellow marrow) are stored
what is hematopoiesis?
blood cell formation by red marrow
the adult skeleton has how many bones?
206
2 basic types of bone tissue
compact bone and spongy bone
compact bone is
homogeneous
spongy bone is made up of
small needle-like pieces of bone and many open spaces
what is the benefit that spongy bone has over compact bone?
it's lighter
how are bones classified?
shape (long, flat, short, and irregular) and what they do
long bones
typically longer than they are wide; shaft with heads at both ends; contain mostly compact bones; examples: femur and humerus
short bones
generally cube-shaped; contain mostly spongy bone; examples: carpals and tarsals
flat bones
thin, flattened, and usually curved; 2 thin layers of compact bone surrounded with a layer of spongy bone; examples: skull, ribs, sternum
irregular bones
irregular shape; don't fit into other bone classification categories; examples: vertebrae and hip bones
2 sets of bones in the skull
cranium and facial bones
what are skull bones are jointed by?
sutures
only skull bone attached by a freely movable joint
mandible
cranial bones
frontal bone (1), parietal bones (2), occipital bone (1), temporal bones (2), sphenoid bone (1), ethmoid bone (1), auditory ossicles (6)
facial bones
nasal bones (2), palatine bones (2), maxillary bones (2), zygomatic bones (2), lacrimal bones (2), nasal conchae (2), vomer bone (1), mandible (1)
what are orbits?
cavities that enclose and protect the eyes
two nasal cavities
surrounded by the nose framework
what are foramina?
passageways for blood vessels and nerves
what is the foramen magnum?
the spinal cord passage
the fetal skull
fontanelles (fibrous membranes connecting the cranial bones; fontanelles allow the brain to grow and convert to bone within 24 months after birth
paranasal sinuses
hollow portions of bones surrounding the nasal cavity; functions: lighten the skull and give resonance/amplification to the voice
hyoid bone
the only bone that does not articulate (connect with/attach to) another bone; serves as a movable base for the tongue and aids in swallowing and speech
diaphysis
shaft composed of compact bone
epiphysis
ends of the bone composed mostly of spongy bone
periosteum
outside covering of the diaphysis made up of fibrous connective tissue membrane
sharpey's fibers
secure the periosteum to the underlying bone
arteries
supply bone cells with nutrients
articular cartilage
covers the external surface of the epiphysis; made of hyaline cartilage; decreases friction at joint surfaces
epiphyseal plate
flat plate of hyaline cartilage seen in young, growing bones
epiphyseal line
remnant of the epiphyseal plate; seen in adult bones
medullary cavity
cavity inside of the shaft; contains yellow marrow (mostly fat) in adults and red marrow (for blood cell formation) in infants and young adults
what are bone markings?
surface features of bones; sites of attachments for muscles, tendons, and ligaments; passages for nerves and blood vessels
2 categories of bone markings
projections/processes and depressions/cavities
projections/processes
grow out from the bone surface
depressions/cavities
indentations in the bone surface
osteon (Haversian system)
a unit of bone containing central canal and matrix rings
central (Haversian) canal
opening in the center of an osteon that carries blood vessels and nerves
perforating (Volksman's) canal
canal perpendicular to the central canal that carries blood vessels and nerves
lacunae
cavities containing bone cells (osteocytes) that are arranged in concentric rings
lamellae
rings around the central canal; sites of lacunae
canaliculi
tiny canals that radiate from the central canal to lacunae; form a transport system that connects all bone cells to a nutrient supply
how many vertebral bones are there?
24
what are the vertebral bones separated by?
intervertebral discs
cervical vertebrae
7 vertebrae in the neck
thoractic vertebrae
12 vertebrae in the chest region
lumbar vertebrae
5 vertebrae associated with the lower back
9 vertebrae fuse to form what 2 composite bones?
the sacrum and the coccyx
curvature of the spine
primary curvatures are the spinal curvatures of the thoracic and sacral regions (present from birth); secondary curvatures are the spinal curvatures of the cervical and lumbar regions (develop after birth)
sacrum
formed by the fusion of 5 vertebrae
coccyx
formed by the fusion of 4 vertebrae; "tailbone"
bony thorax
forms a cage to protect major organs; made up of 3 parts (sternum, ribs, and thoractic vertebrae)
ribs
true ribs (pairs 1-7)
false ribs (pairs 8-12)
floating ribs (pairs 11-12)
in the fetus the skeleton is primarily made of what?
hyaline cartilage
buring development, what replaces cartilage?
bone
where does cartilage remain?
the bridge of the nose, parts of the ribs, and in joints
what is bone growth called?
ossification
what allows for lengthwise growth of long bones during childhood?
the epiphyseal plate
what happens during ossification?
new cartilage is continuously formed, older cartilage becomes ossified (turns into bone); cartilage is broken down, enclosed cartilage is digested away, opening up a medullary cavity, bone replaces cartilage through the action of osteoblasts; bones are remodeled and lengthened until growth stops; bones grow in width (appositional growth)
what are the 2 factors that cause bone to be remodeled?
blood calcium levels and the pull of gravity and muscles on the skeleton
osteoporosis
bone thinning disease that makes bones fragile and easily fractured; vertebral collapse results in kyphosis (also known as Dowager's hump)
fracture
break in a bone
difference between a break and a fracture
none
types of fractures
closed (simple)
open (compound)
closed (simple) fracture
break that does not penetrate the skin
open (compound) fracture
break where the bone penetrates through the skin
how are bone fractures treated?
reduction and immobilization
what is the repair process for bone fractures?
1) hematoma (blood-filled swelling) is formed
2) break is splinted by fibrocartilage to form a callus
3) fibrocartilage callus is replaced by a bony callus
4) bony callus is remodeled to form a permanent patch
what are the stages of recovery?
Stage 1) Acute (3-5 days)
Stage 2) Repair (several weeks)
Stage 3) Remodeling the repair (1+ years)
Stage 1 of fracture recovery
bleeding
osteoclasts break down injured bone and remove debris
osteoblasts begin to add new layers of bone around the fracture site
Stage 2 of fracture recovery
osteoblasts and osteoclasts form a callus to temporarily hold the bone together
Stage 3 of fracture recovery
bone continues to develop around fracture site making it stronger
what are joints?
articulations of bones
what are the functions of joints?
hold bones together and allow for mobility
how are joints classified?
functionally and structurally
synarthroses
immovable joints; examples: skull sutures
amphiorthroses
slightly movable joints
diarthroses
freely movable joints
structural classification of joints
fibrous joints (generally immovable)
cartilaginous joints (immovable or slightly movable)
synovial joints (freely movable)
fibrous joints
bones united by fibrous tissue; examples: sutures and syndesmoses (allows more movement than sutures; found at the distal end of the tibia and fibula)
cartilaginous joints
bones connected by cartilage; examples: pubic symphysis and intervertebral joints)
synovial joints
articular cartilage (hyaline cartilage) covers the ends of bones; a fibrous articular capsule encloses joint surfaces; a joint cavity is filled with synovial fluid; ligaments reinforce the joint
structures associated with the synovial joints
bursae and tendon sheaths
bursae
flattened fibrous sacs; lined with synovial membranes and filled with synovial fluid; not actually part of the joint
tendon sheath
elongated bursa that wraps around tendon
inflammatory conditions associated with joints
bursitis, tendonitis, and arthritis
bursitis
inflammation of a bursa usually caused by a blow or friction
tendonitis
inflammation of tendon sheaths
arthritis
inflammatory or degenerative diseases of joints; over 100 different types; most widespread crippling disease in the United States