A&P Axial Skeleton

musculoskeletal system

An integrated body system consisting of bones, joints, and muscles.

orthopedics

The branch of medicine that deals with the preservation and restoration of the skeletal system, articulations, and associated structures.

axial skeleton

80 bones; consists of the skull bones, auditory ossicles, hyoid bone, ribs, sternum, vertebrae  and sacrum

appendicular skeleton

126 bones; consists of the bones of the upper and lower extremities and the bones forming the girdles

girdles

bones connecting the limbs to the axial skeleton

long bones

greater length than width, consist of diaphysis and epiphyses, slightly curved for strength. mostly compact bone tissue with spongy bone tissue in the epiphyses

short bones

somewhat cube-shaped and nearly equal in length and width. mostly spongy bone tissue with a thin surface of compact bone tissue

flat bones

thin, composed of two compact bone plates enclosing a layer of spongy bone. provide protection and extensive areas for muscle attachment

irregular bones

complex shapes and do not fit into any other categories

sesamoid bones

Small bone usually found in tendons that develops where there is considerable friction, tension, and physical stress; numbers vary from person to person. protection of tendons from excessive wear and tear.

long bone examples

femur, tibia, fibula, humerus, ulna, radius, phalanges

short bone examples

carpal and tarsal bones

flat bone examples

cranial cavity bones, sternum, ribs

irregular bone examples

vertebrae, hip bones, certain facial bones, calcaneus

sesamoid bone examples

kneecaps

sutural bones

classified by location, small flat bones in joints between certain cranial cavity bones. number varies by individual

surface markings

structural features adapted for specific functions

depressions and openings

allows the passage of soft tissues (blood vessels, nerves, ligaments, tendons) or form joints

processes

projections or outgrowths that either help form joints or serve as attachment points for connective tissue

Fissure

Narrow slit between adjacent parts of bones through which blood vessels or nerves pass.

ex. Superior orbital fissure of sphenoid bone

Foramen

Opening through which blood vessels, nerves, or ligaments pass.

ex. Optic canal of sphenoid bone

Fossa

shallow depression.

ex. coronoid fossa of humerus

sulcus

furrow along the bone surface that accomodates blood vessel, nerve, or tendon

ex. intertubercular sulcus of humerus

meatus

tubelike opening

ex. external acoustic meatus of temporal bone

condyle

large, round protuberance with a smooth articular surface at end of bone

ex. lateral condyle of femur

facet

smooth, flat, slightly concave or convex articular surface

ex. superior articular facet of vertebra

head

usually rounded articular projection supported on neck (constricted portion) of bone

ex. head of femur

crest

prominent ridge or elongated projection

ex. iliac crest of hip bone

epicondyle

typically roughened projection above condyle

ex. medial epicondyle of femur

line (linea)

long, narrow ridge or border (less prominent than crest)

ex. linea aspera of femur

spinous process

sharp, slender projection

ex. spinous process of vertebra

trochanter

very large projection

ex. greater trochanter of femur

tubercle

variably-sized rounded projection

ex. greater tubercle of humerus

tuberosity

variably-sized projection that has a rough, bumpy surface

ex. ischial tuberosity of hip bone

skull

The skeleton of the head consisting of the cranial cavity bones and facial bones. contains 22 bones

cranial cavity bones

frontal bone, two parietal bones, two temporal bones, occipital bone, sphenoid bone, and ethmoid bone

facial bones

forms anterior part of the skull, 14 bones. two nasal bones, two maxillae, two zygomatic bones, mandible, two lacrimal bones, two palatine bones, two inferior nasal concha bones, and vomer.

frontal bone

forms the forehead, roofs of the orbits, and most of the anterior part of the cranial base.

partietal bones

forms the greater portion of the sides and roof of the cranial cavity.

temporal bones

forms the inferior lateral aspects of the cranial cavity and part of the cranial base.

mastoiditis

infection of the mastoid bone behind the ear. painful inflammation

occipital bone

forms the posterior part of the cranial cavity and most of the cranial base

sphenoid bone

lies at the middle part of the cranial base. “keystone” of the cranial base, resembles a butterfly

ethmoid bone

delicate bone located in the anterior part of the cranial base medial to the orbits and is spongelike in appearance. anterior to the sphenoid and posterior to the nasal bones. major supporting structure of the nasal cavity

Temporomandibular Joint Dysfunction (TMJ)

characterized by dull pain around ear, tender jaw muscles, clicking noise when opening/closing mouth. caused by improperly aligned teeth, grinding teeth, trauma to the head, arthritis, etc. treatment involves moist heat or ice, soft foods and pain relievers

Deviated septum

occurs when the septum does not run along the midline of nasal cavity. caused by trauma to the nose or developmental abnormality. may lead to infection, inflammation, congestion, headaches and nosebleeds. may require surgery to fix

nasal bones

small, flattened, rectangular-shaped bones that form the bridge of the nose. protects the upper entry to the nasal cavity and provides attachment for a couple thin muscles of facial expression. the bones that form the resting place for the bridge of glasses

lacrimal bones

thin and roughly resemble a fingernail in size and shape. posterior and lateral to the nasal bones and form a part of the medial wall of each orbit. each contain a lacrimal fossa, a vertical tunnel formed with the maxilla that houses the lacrimal sac, a structure that gathers tears and passes them into the nasal cavity

palatine bones

L-shaped, form the posterior portion of the hard plate, part of the floor and poserolateral wall of the nasal cavity, and a small portion of the floors of the orbits.

inferior nasal concha bones

inferior to the middle nasal conchae of the ethmoid bone. scroll-like bones that form a part of the inferior lateral walls of the nasal cavity and project into the nasal cavity. increases the surface area of the nasal cavity and help swirl and filter before it passes into the lungs.

cleft palate

incomplete fusion of the horizontal plates of the palatine bones

Vomer

roughly triangular bone that forms the inferior part of the nasal septum.

maxillae

unites to form the upper jawbone. form part of the floors of the orbits, part of the lateral walls and floor of the nasal cavity, and most of the hard palate. contains a large maxillary sinus that empties into the nasal cavity

hard palate

the bony roof of the mouth, formed by the palatine processes of the maxillae and horizontal plates of the palatine bones. separates the nasal cavity from the oral cavity

zygomatic bones

commonly called cheekbones. form the prominences of the cheeks and part of the lateral wall and floor of each orbit. The temporal process of the zygomatic bone projects posteriorly and articulates with the zygomatic process of the temporal bone to form the zygomatic arch

mandible

lower jawbone; is the largest, strongest facial bone. the only movable skull bone other than the auditory ossicles. consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami.

mental foramen

inferior to the second premolar tooth

mandibular foramen

on the medial surface of each ramus

mandibular canal

runs obliquely to the ramus and anteriorly to the body. inferior alveolar nerves and blood vessels pass here and are distributed to the mandibular teeth

nasal septum

A vertical partition composed of bone (perpendicular plate of ethmoid and vomer) and septal nasal cartilage (hyaline cartilage), covered with a mucous membrane, separating the nasal cavity into left and right sides.

orbits

The bony, pyramidal‐shaped cavity of the skull that holds the eyeball

foramen/foramina

openings for blood vessels, nerves, ligaments

coronal suture

unites the frontal bone and both parietal bones

sagittal suture

unites the two parietal bones on the superior midline of the skull

lambdoid suture

unites the two parietal bones to the occipital bone.

squamous sutures

unites the parietal and temporal bones on the lateral aspects of hte skull

carotid canal

Petrous portion of temporal bone

Internal carotid artery, sympathetic nerves for eyes.

hypoglossal canal

Superior to base of occipital condyles

Hypoglossal (XII) nerve, branch of ascending pharyngeal blood vessel.

infraorbital foramen

Inferior to orbit in maxilla

Infraorbital nerve and blood vessels, branch of maxillary branch of trigeminal (V) nerve.

jugular foramen

Posterior to carotid canal between petrous portion of temporal bone and occipital bone

Internal jugular vein; glossopharyngeal (IX), vagus (X), and accessory (XI) nerves.

lacerum foramen

Bounded anteriorly by sphenoid bone, posteriorly by petrous portion of temporal bone, medially by sphenoid and occipital bones

Branch of ascending pharyngeal artery.

magnum foramen

Occipital bone

Medulla oblongata and its membranes (meninges), accessory (XI) nerve, vertebral and spinal arteries.

mandibular foramen

Medial surface of ramus of mandible

Inferior alveolar nerve and blood vessels.

mastoid foramen

Posterior border of mastoid process of temporal bone

Emissary vein to transverse sinus, branch of occipital artery to dura mater.

mental foramen

Inferior to second premolar tooth in mandible

Mental nerve and vessels.

cribriform foramen

Cribriform plate of ethmoid bone

Olfactory (I) nerve.

optic canal

Between superior and inferior portions of small wing of sphenoid bone

Optic (II) nerve, ophthalmic blood vessels.

ovale foramen

Greater wing of sphenoid bone

Mandibular division of trigeminal (V) nerve.

rotundum foramen

Junction of anterior and medial parts of sphenoid bone

Maxillary division of trigeminal (V) nerve.

stylomastoid foramen

Between styloid and mastoid processes of temporal bone

Facial (VII) nerve, stylomastoid blood vessels.

supraorbital foramen

Supraorbital margin of orbit in frontal bone

Supraorbital nerve and blood vessels.

paranasal sinuses

A mucus‐lined air cavity in a skull bone that communicates with the nasal cavity; located in the frontal, maxillary, ethmoid, and sphenoid bones.

sinusitis

inflammation of the mucous membrane of one or more paranasal sinuses. may be caused by microbial infection, allergic reactions, nasal polyps, or a severely deviated septum.

fontanels or “soft spots”

A mesenchyme-filled space where bone formation is not yet complete, especially between the cranial cavity bones of an infant’s skull.

anterior fontanel

largest fontanel, located at the midline among the two parietal bones and the frontal bone, and is roughly diamond-shaped. It usually closes 18 to 24 months after birth.

posterior fontanel

located at the midline among the two parietal bones and the occipital bone. Because it is much smaller than the anterior fontanel, it generally closes about 2 months after birth.

anterolateral fontanels

located laterally among the frontal, parietal, temporal, and sphenoid bones, are small and irregular in shape. Normally, they close about 3 months after birth.

posterolateral fontanels

located laterally among the parietal, occipital, and temporal bones, are irregularly shaped. They begin to close 1 to 2 months after birth, but closure is generally not complete until 12 months.

hyoid bone

unique component of the axial skeleton; does not articulate with any other bone. it is suspended from the styloid processes of the temporal bones by ligaments and muscle. supports the tongue and provides attachment sites for some tongue muscles and those of the neck and pharynx. consists of lesser horns and greater horns

vertebral column

The 26 vertebrae of an adult and 33 vertebrae of a child; encloses and protects the spinal cord and serves as a point of attachment for the ribs and back muscles. Also called the backbone, spine, or spinal column.

number of vertebrae

7 cervical (neck) 12 thoracic, 5 lumbar, 1 sacrum, 1 coccyx

coccyx

four fused bones at the inferior end of the vertebral column in a triangular shape. fuse between the ages of 20 and 30. the tailbone

sacrum

consists of 5 fused vertebrae. triangular bone. begins to fuse age 16-18 and is complete by 30. serves as strong foundation for the pelvic girdle. female is shorter, wider, and more curved than male

primary curves

curves of the spine, the thoracic and sacral curves. these retain the original curvature of the embryonic vertebral column

secondary curves

the cervical and lumbar curves; these begin to form later, several months after birth, and finish forming by age 10. may be progressively lost in old age

abnormal curves

kephosis, lordosis, and scoliosis

intervertebral discs

A pad of fibrous cartilage located between the bodies of two vertebrae. accounts for 25% of the height of the vertebral column

vertebral body

the thick, disc shaped anterior portion of the vertebra; the weight bearing portion. superior and inferior surfaces are roughened for the attachment of cartilaginous intervertebral discs. The anterior and lateral surfaces contain nutrient foramina

vertebral arch

two short, thick processes, the pedicles, project posteriorly from the vertebral body and then unite with the flat laminae to form this.

vertebral foramen

vertebral body and vertebral arch surround the spinal cord to form this. contains the spinal cord, adipose tissue, areolar connective tissue, and blood vessels