lab #4 quiz - axial skeleton

vertebral column

consists of irregular bones; more spongy bone than compact bone

separated by pads of fibrocartilage called intervertebral discs

divided into three regions

bone count of vertebral column

26 bones in all

24 single bones (vertebrae) plus 2 fused bones; the sacrum (5 fused into 1) and the coccyx (4 fused into 1)

vertebral column three regions

cervical, thoracic, lumbar

cervical region

7 vertebrae of the neck (C1-C7)

thoracic region

12 vertebrae of the upper and mid-back (T1-T12)

lumbar region

5 vertebrae of lower back (L1-L5)

anatomy of a generic vertebra

vertebral body, vertebral arch, vertebral foramen

vertebral body

anterior aspect of the bone with a dense medial portion

tends to be disc-shaped and is weight-bearing

vertebral arch

consists of up to 7 projections

spinous process

transverse processes

superior articular processes

interior articular processes

spinous process

1, posteromedial projection; site of muscle attachment

transverse processes

2, two lateral projections, sites of muscle attachment

superior articular processes

2, protrude superiorly from pedicle-lamina junction

interior articular processes

2, protrude inferiorly from pedicle-lamina junction

smooth joint surfaces are called facets and are covered with hyaline cartilage

inferior articular processes of each vertebra for moveable joints with the superior articular processes of the vertebrae immediately below

vertebral foramen

central hole of the vertebral located posterior to the vertebral body; formed by the enclosure of the body and the vertebral arch

pedicles

part of the vertebral foramen

short bony pillars that project posteriorly from the body; connect the body to the vertebral arch; allows passage of the spinal cord

cervical vertebrae

total of 7; C1-C7

first two cervical vertebrae are modified to perform special functions like movements of the head

referred to as atlas (C1) and axis (C2)

atlas C1

has no body; densest parts are the lateral masses; has no spinous process; has no laminae, but has posterior tubercle, has anterior and posterior arches

lateral masses and interior facets

lateral masses

2, superior facets are concave and receive the occipital condyles of the skull

articulation between skull and C1 results in a nodding motion “yes”int

interior facets

form joint with axis (C2) below

fovea dentis

part of interior facets

articulates with the dens of C2; located on the posterior border of the anterior arch

axis (C2)

has body; has spinous process

pivot joint allows for rotation of the skull

dens

there are no fibrocartilage discs between the skull and C1 and between C1 and C2

dens

also known as odontoid process, a vertical process that articulates with the fovea dentis of C1 and allows for rotation of the head from side to side “no”

remaining cervical vertebrae (C3-C7)

smallest and lightest of all the vertebrae; have triangular vertebral foramen

short spinous process which is bifurcated (two branches)

wide transverse processes which contain holes called transverse foramina that allow for passage of vertebral arteries

easily palpable and forms visible bump, useful for counting vertebrae, and transition of the curvature of the spine

C7

modified spinous process

longer than normal and NOT bifurcated

known as vertebrae prominens

thoracic vertebrae

total of 12; T1-T12

larger, heart-shaped vertebral body than cervical vertebrae

have round and oval vertebral foramen

costal demifacets

articular facets on transverse processes articulate with the tubercules of the ribs; also serve as sites of muscle attachment

long spinous process hooks downward (similar to C7)

only vertebrae that articulate with the ribs

costal demifacets

are two sets of articulated surfaces (superior and inferior) on the body allows for articulation with the heads of ribs

lumbar vertebrae

total of 5, L1 through L5

largest vertebrae with notably large block-like vertebral body

short, thick, hatchet-shaped spinous process that extends directly posterior

thin transverse process (site for muscle attachment) with triangular vertebral foramen (like cervical vertebrae)

articular processes are locked to prevent rotation (reduces overall mobility in this area

sacrum

formed from the fusion of 5 vertebrae; medial sacral crest are the remnants of spinous processes of these 5 vertebrae

articulate with L5 superiorly and with the coccyx inferiorly

alae

alae

wing like projections that articulate with the os coxae

coccyx

formed by the fusion of 4 small vertebrae; colloquially referred to as as the “tail bone” attached to the sacrum by ligaments; gives some support to the pelvic organs (reproductive organs)

rib cage

the thoracic cage is composed of the sternum, ribs and thoracic vertebrae

all ribs articulate posteriorly with the vertebral column via their heads and tuberclesr

ribs

four parts = head, back, tubercle and shaft

almost all ribs articulate posteriorly with the vertebral column via their heads and tubercles

all heads articulate with the demifacets of the adjacent vertebrae

tubercles 1-10 articulate with the facets in the transverse processt

types of ribs

vertebrosternal (true ribs)

false ribs

floating ribs

vertebrosternal ribs

true ribs

ribs 1-7

attach directly to the sternum via their own costal cartilage

false ribs

ribs 8-12 attach indirectly to sternum through the cartilage of rib 7

floating ribs

11 and 12

no sternal attachment

help protect organs

skull

divided into into 2 sets of bones

the cranial bones which enclose and protect the brain, and the facial bones which construct the face

cranial floor

anterior cranial fossa

middle cranial fossa

posterior cranial fossa

anterior cranial fossa

which supports frontal lobe of brain

middle cranial fossa

which supports temporal lobe of brain

posterior cranial fossa

supports the cerebellum

cranium

is composed of 8 large, flat bones

four of these eight bones exist as bilateral pairs

the left and right parietal and temporal bones

remaining four bones, the frontal, occipital, sphenoid, and ethmoid bones, are single or unpaired

frontal bone

forms the forehead and the roof of the orbits

includes supraorbital foramina (small openings above the orbits that allow for the passage of blood vessels and nerves)

parietal bone

2, form the sides and the top and some of the back of the cranium

temporal bones

2, lateral bones of the cranium located inferiorly to the parietal bones

each one has four anatomical regions

squamous region, tympanic region, mastoid region, petrous region

squamous region

which borders the parietal bones

tympanic region

which surrounds the ear opening

mastoid region

which is located posteriorly to the ear

petrous region

which forms the lateral portion of the skull base

zygomatic process

bridge-like projections on the side of the skull which articulate the zygomatic bone

for the zygomatic arches along the temporal processes of the zygomatic bones which contribute to the lateral border of the eye orbits

external auditory

acoustic meatus, canal leading to the ear drum and middle ears

styloid process

needle-like projections inferior to the auditory meatus which serves as an attachment site for muscles and ligaments of neck

mastoid process

projections located infraposteriorly to the auditory meatus and serve as an attachment site for muscles

jugular foramina

can be seen from the inferior view, they form a large kidney bean shaped opening medial to the styloid processes and serve to allow passage of blood vessels and some cranial nerves

carotid canals

can be seen from inferior view, they form medium sized openings located medial to the styloid process and anterior to the jugular foramen and serve to allow passage of carotid arteries

occipital bone

posterior most cranial bone that forms the majority of the cranial floor

includes foramen magnum, occipital condyles, hypoglossal canals, and external occipital protuberance (EOP)

foramen magnum

prominent occipital base opening that passes the spinal cord

occiopital condyle

smooth, rounded projections located lateral to foramen magnum which articulate with the atlas C1

hypoglossal canals

located lateral to the foramen magnum, allow passage of the hypoglossal nerves (CN XII)

EOP

midline prominence on the outer posterior surface of the occipital bone and serves as a site for muscle attachment

sphenoid bone

bat-shaped bone located in space between each temple, posteriorly to the eye orbits, forms part of the orbit and the middle cranial fossafea

features of the sphenoid bone

externally visible greater wings located anterior to the temporal bones and form the temple

superior orbital fissure, seen anteriorly, allow for passage of several cranial nerves which innervate the eyes

sella turcica (turkish saddle) resembles a horse saddle, cradles the pituitary gland can be seen from the superior view

openings that serve to allow passage of cranial nerves and or blood vessels

optic foramina, foramen rotundum, foramen ovale, foramen spinosum, and foramen lacerum

ethmoid bone

anterior to the sphenoid bone, forms medial border of the orbit and roof of nasal cavitysut

sutures of the cranium

they do not move, are immoveable fibrous joints formed by the interlocking of adjacent cranial bones, 4 types

sagittal suture

connects the two parietal bones

coronal suture

connects each parietal bone to the frontal bone

squamous sutures

connect each parietal bone to its ipsilateral temporal bone

lamboid suture

connects each parietal bone to the occipital bone

facial bones

group of 14 bones forming the face

12/14 exist as bilateral pairs (6 pairs of 2)

maxillae, palatine, zygomatic, lacrimal and nasal bones, inferior nasal conchae

mandible and vomer are single or unpaired

mandible

jawbone, only facial bone that freely articulates with the skull

mandibular body, mandibular rami, coronoid processes, mandibular foramina, mental foramina, alveolar margin

mandibular body

horizontal portion of this mandible which helps form the chin

mandibular rami

vertical extensions located superior to the mandibular angle that form the sides of the jaw

coronoid processes

bony processes on the anterior aspect of each ramus which serves as muscle attachment sitema

mental foramina

bilaterally located on the anterior-most aspect of the mandible, near the chin

allow passage of the mental nerve, sub-branch of inferior alveolar nerve

mandibular foramina

located on the medial surfaces (the inside) of the mandibular rami and pass the mandibular branch of the trigeminal nerve (CN V)

alveolar margin

forms the superior border of the mandible and contains the sockets for the teeth of the lower jaw

maxilla

formed by the fusion of the left and right maxilla bones, the fusion of the maxillae is known as the median suture

the fused maxillae form the upper jaw as well as the inferior aspect of the eye orbits

alveolar margin, palatine process and infraorbital foramina

alveolar margin

forms the inferior border of the maxilla and similar to the maxillary alveolar margin, contains tooth sockets

palatine process

forms the anterior portion of the hard palate, two bony outward projections fuse with each other to form the medial palatine suture

infraoribital foramina

located inferior to the eye orbit and permits passage of the infraorbital nerves as well as blood vessels to the nasal region

vomer

blade-shaped bone in median plane of nasal cavity

nasal septum

formed by the ethmoid bone superiorly and the vomer inferiorly

hyoid bone

not considered a bone of the skull

located in the throat above the pharynx

horse-shoe shaped, only bone in the body that does not articulate with another bone

attached to surrounding tissues by ligaments alone, and serves as attachment site for several muscles of the tongue and the neck

paranasal sinuses

air filled cavities within some facial bones which are lined with mucous membranes that help warm and humidify inhaled air

lighten the skull and enhance voice resonance

frontal, ethmoid, maxillary and sphenoid sinus