Condensed Notes - Chapter 6 THE SKELETAL SYSTEM II: The Axial Skeleton DR. YARD IUPUI

206 bones

How many bones form the axial and appendicular skeleton?

The Axial Skeleton

forms the long axis of the body; supports the head, neck and trunk; and protects the brain, spinal cord, and thoracic organs

The Skull, Vertebral Column, and Bony Thorax

What are the 3 major regions of the axial skeleton?

The Skull

Most complex bony structure of the skeleton, formed by cranial (cranium) and facial bones

The Skull

Mostly FLAT bones connected by sutures....all but one bone (mandible) in this are joined by sutures.

1) Cranial Vault

2) Cranial Base

What are the 2 major areas that the Cranium (Braincase) may be divided into?

Cranial Vault (calvarium)

skull cap or roof of the skull

Cranial Base or cranial floor (inferior part)

anterior, middle, and posterior cranial fossae (a depression, singular = fossa)

85 named openings

how many named openings are there that are commonly called foramina (foramen), canals, or fissures, and occassionally lacerum?

22

how many bones comprise the skull?

8

how many of the 22 bones that comprise the skull are cranial bones?

14

how many of the 22 bones that comprise the skull are facial bones?

Frontal Bone (1)

Bone that forms the forehead and the roofs of the orbits

Glabella

smooth part in the midline of frontal bone between the superciliary arches, which support the eyebrows

Frontal Squama

vertical anterior-most part of the frontal bone (forehead)

supraorbital margins

mark the superior limits of the orbits, the bony recesses that support and protect the eyeballs in the Frontal Bone

supraorbital foramen (notch)

opening above each orbit, which transmits the supraorbital artery and nerve in the frontal bone

lacrimal fossa

marks the location of the lacrimal (tear) gland that lubricates the surface of the eye in the frontal bone

parietal bones (2)

pair of curved rectangular bones

parietal bones (2)

located posterolateral to the frontal bone, forming the sides of the cranium

Superior and inferior temporal lines

low ridges on the external surface of each bone, marking the attachment of the temporalis muscle (closes the mouth) (parietal bone)

parietal eminence

the smooth parietal surface superior to the temporal lines on the parietal bones

parietal

4 of the major sutures are associated with the _______ bones, at which they articulate with other cranial bones

Occipital bone (1)

Most posterior of the cranial bones, forms the floor and back wall of the skull

Foramen Magnum

hole in the base of occipital bone through which spinal cord passes and is connected to the brain

Occipital Condyles

facets on the base of the skull, which articulate with the superior facets of the C1 (ATLAS) vertebra on the occipital bone

Hypoglossal canals

passageway for hypoglossal cranial nerve XII; begin at the lateral base of each occipital condyle on the occipital bone

basioccipital

a band of bone anterior to the foramen magnum, which is the point of articulation between the occipital bone and the sphenoid

External occipital crest and protuberance

midline prominences posterior to foramen magnum; the crest extends posteriorly from the foramen magnum, ending in the protuberance (a small midline bump)

Superior and inferior nuchal lines

horizontal ridges that intersect the external occipital crest; these lines mark the attachment of muscles and ligaments that stabilize the articulation between the first verebra, C1, and the occipital condyles

temporal bones (2)

inferior to parietal bones on lateral skull

Squamous, tympanic, mastoid, petrous

4 major regions of the temporal bones

Squamous region or part

the lateral surface bordering the squamous suture on the temporal bones

Squama

the convex external surface of the region on the temporal bones

Cerebral surface

The concave internal surface, whose curvature parallels the surface of the brain on temporal bones

zygomatic process

the inferior margin of the region, which curves laterally and anteriorly to meet the temporal process of the zygomatic bone; together, they form the zygomatic arch, (or cheekbone) which defines the projection of the cheek

parietal

the squamous region abuts the ____ bone on each side

Tympanic region or part on Temporal bones

surrounds the external acoustic meatus (or external auditory canal) immediately posterior and lateral to the mandibular fossa

Tympanic Region or part

contains the styloid process, a needlelike projection inferior to the external auditory meatus on temporal bones

styloid process

the _______ marks the attachment site for ligaments that support the hyoid bone and for muscles of the tongue, pharynx, and larynx on temporal bones

Mastoid region or part

breast-shaped area posterior to the ear on temporal bones

Mastoid region or part

contains the mastoid process, a rough projection, which anchors some neck muscles that rotate and extend the head on temporal bones

Petrous region or part

the most massive portion of the temporal bone -- contributes to the cranial base and forms the lateral region of the skull on temporal bones

petrous region

contains the jugular foramen, passageway through which the internal jugular vein (largest vein of the head) and cranial nerves IX, X, and XI pass on temporal bones

Carotid Canal

opens in the petrous region on the skulls inferior aspect, just anterior to the jugular foramen; passageway for internal carotid artery on temporal bones

Foramen Lacerum

jagged opening between the medial tip of the petrous portion of the temporal bone and the sphenoid bone; almost completely closed by cartilage in a living person, but conspicuous in a dried skull

Internal acoustic meatus

lies in the cranial cavity on the posterior face of the petrous region; transmits cranial nerves VII and VIII (temporal bones)

sphenoid (1)

forms the anterior plateau of the middle cranial fossa

sphenoid (1)

spans the width of the cranial floor

Greater wings

visible exteriorly anterior to temporal; form a portion of the orbits of the eyes on sphenoid bone

lesser wings

bat-shaped portions located anterior to the sella turcica on sphenoid bone

Pterygoid Processes

vertical projections that begin at the boundary between the greater and lesser wings of sphenoid bone

pterygoid processes

contain attachment sites for pterygoid muscles that move the lower jaw and soft palate

Sella turcica

contains the hypophyseal fossa, which holds the pituitary gland (hypophysis) on sphenoid

Anterior Clinoid Processes

located on either side of the sella turcica are these posterior projections of the lesser wings of the sphenoid

Tuberculum Sellae

forms the anterior border of the sella turcica

Dorsum sellae

forms the posterior border of the sella turcica

posterior clinoid processes

extend laterally on either side of the dorsum sellae

sella turcica

the inferior part of the ____ form part of the orbit and the superior part of the superior orbital fissure

optic groove

transverse groove that crosses to the front of the saddle, above the seat (sella turcica)

optic canal

openings at either end of the optic groove

Optic foramen

opening of the sphenoid, anterior to sella turcica, CN II passes through from the orbit into the cranial cavity

Superior orbital fissure

opening of the sphenoid, long slit between the greater and lesser wings, transmits CN III, IV, and VI (control eye movement)

Foramen Rotundum

opening of the sphenoid, lateral to sella turcica, passage for a branch of CN V

Foramen Ovale

opening of the sphenoid, posterior to sella turcica, passage for a branch of CN V

Foramen Spinosum

opening of the sphenoid, inferior aspect, transmits the middle meningeal artery, which supplies the broad inner surfaces of the parietal and temporal bones

Ethmoid bone (1)

the most deeply situated bone located anterior to the sphenoid

ethmoid bone (1)

forms most of the medial bony area between the nasal cavity and the orbits

ethmoid bone (1)

forms part of the orbital wall, the anteromedial floor of the cranium, the roof of the nasal cavity, and part of the nasal septum

Cribriform plates, ethmoidal labyrinth, and perpendicular plate

3 major parts of ethmoid bone

cribriform plates

contributes to the roof of nasal cavities and floor of anterior cranial fossa

cribriform plates

contain olfactory foramina (or cribriform foramina) which transmit olfactory fibers of CN I (provide the sense of smell)

crista galli

superior projection between the 2 cribriform plates; attached to falx cerebri (a membraneous ligament) which helps secure the brain within the cranial cavity

ethmoidal labyrinth

an interconnected network of ethmoidal air cells

ethmoidal labyrinth

dominated by the superior and middle nasal conchae, which are thin scrolls of bony structures that contribute to the conchae of nasal cavity, on either side of the perpendicular plate

ethmoidal labyrinth

best viewed from the anterior and posterior surfaces of the ethmoid

perpendicular plate

forms superior part of nasal septum, ethmoid

perpendicular plate

projects inferiorly in the median plate, ethmoid

perpendicular plate

superior portion is covered by olfactory epithelium, ethmoid

Lateral masses

irregularly shaped, thin-walled bony regions flanking the perpendicular plate laterally; also riddled with sinuses, ethmoid

coronal suture

where the parietal bones articulate with the frontal bone

squamous suture

where the parietal bones articulate with the temporal bones inferiorly

sagittal suture

where right and left parietal bones meet

lambdoid suture

where the parietal bones articulate with the occipital bone

frontonasal suture

boundary between the superior aspects of the two nasal bones and the frontal bone

occipitomastoid suture

where the occipital bone articulates with the temporal bones

mandible ( 1 bone )

lower jaw bone

mandibular body

horizontal portion that supports the teeth

Rami of the mandible (singular = ramus)

ascending portions from each side of the body of the mandible

mandibular angles

where each ramus of the mandible meets the body

alveolar margin or part

thickened area that contains the alveoli and the roots of the teeth

condylar processes

posterior processes that enlarge superiorly to form the mandibular condyles (or heads of the mandible), which articulate with mandibular fossae of the temporal bones to form the temporomandibular joint

coronoid processes

jutting anterior portion of each ramus; site of temporalis muscle attachment

mandibular notch

the depression that lies between the condylar and coronoid processes

mental foramina

prominent openings lateral to the midline, penetrating the body of the mandible on each side; passageway for mental blood vessels and nerve that serve the lower jaw

mylohyoid line of mandible

lies on the medial aspect of the body of the mandible, marking the origin of the mylohyoid muscle

submandibular fossa

a depression inferior to the mylohyoid line, in which the submandibular salivary gland is located

mandibular foramina

openings on the medial aspect of both rami; passageway for mandibular branch of CN V (for tooth sensation)

Maxillary bones or Maxillai

the largest facial bones that form the upper jaw and central part of the facial skeleton

orbital surface

on each maxilla, the ______ provides protection for the eye and other orbital structures