Chapter 6 Anatomy

What is the axial skeleton and its jobs?

Forms the long axis of the body

supports the head, neck and trunk

and protects the brain, spinal cord and thoracic organs

Three major regions of the axial skeleton

1. The skull

2. The vertebral column

3. The bony thorax

Most complex bony structure of the skeleton made of cranial and facial bones

Skull

Immovable joints connecting most bones of the skull, made of mostly FLAT bones

Sutures

The braincase portion of the skull.

Cranium

Skull cap or roof of the skull

Cranial vault (calvarium)

Inferior portion of the cranium divided into anterior, middle and posterior cranial fossae

Cranial base

Depression in a bone

Fossa

Opening through a bone that allows nerves, blood vessels, and other vital structures to travel from one area to another

Foramen

Number of bones that comprise the skull

22 skull bones

Number of cranial bones in the skull

8 cranial bones

Number of facial bones in the skull

14 facial bones

What CRANIAL bone forms the forehead and roofs of the orbits

Frontal bone (1)

Smooth midline area of the frontal bone between the eyebrow ridges

Glabella

Vertical anterior portion of the frontal bone forming the forehead

Frontal squama

Superior limits of the eye orbits. Supports and protects the eyeballs

Supraorbital margins

Opening above each orbit transmitting the supraorbital artery and nerve

Supraorbital foramen

Depression containing the tear gland (lacrimal gland) that lubricates the eye

Lacrimal fossa

Paired bones forming much of the sides and roof of the cranium

Parietal bones (2)

Ridges on the parietal bones marking attachment of the temporalis muscle (closes the mouth)

Temporal lines

Smooth parietal surface superior to the temporal lines

Parietal eminence

Most posterior cranial bone forming the floor and back wall of the skull

Occipital bone (1)

Large opening in the occipital bone through which the spinal cord connects with the brain

Foramen magnum

Structures of the occipital bone that articulate with the atlas

Occipital condyles

Passageways for cranial nerve twelve. begins at the lateral base of each occipital condyle

Hypoglossal canals

Band of bone anterior to the foramen magnum. the point of articulation between occipital bone and sphenoid

Basioccipital (basilar part)

Midline ridge on the posterior occipital bone.

AND

Small midline bump on the posterior occipital bone

The crest extends posteriorly from foramen magnum, ending in the protuberance. (list 2)

External occipital crest

AND

External occipital protuberance

Horizontal ridges marking muscle and ligament attachment on the occipital bone (list 2)

These stabilize the articulation between first vertebra C1 and occipital condyles

Superior AND inferior Nuchal lines

Paired cranial bones located inferior to the parietal bones on the lateral skull

Temporal bones (2)

Four major regions of the temporal bone

• Squamous part: A large, flat, and translucent plate of bone that forms the anterior and superior part of the temporal bone. It assists in forming the lateral wall of the cranium and features the zygomatic process, which helps form the cheekbone.

• Tympanic part: A small, curved plate of bone located below the squamous part and anterior to the mastoid process. It forms the bony walls of the external acoustic meatus (ear canal).

• Mastoid part: The posterior portion of the temporal bone that sits behind the ear. It features the prominent, conical mastoid process (an attachment point for neck muscles) and contains hollow mastoid air cells.

• Petrous part: A dense, wedge-shaped, pyramidal mass located at the base of the skull between the sphenoid and occipital bones. It houses the internal acoustic meatus, as well as the delicate structures of the middle and inner ear (cochlea and vestibular system).

Lateral region of the temporal bone bordering the squamous suture

Squamous region

A squama in a squamous region refers to a thin, flat, scale-like plate of bone that forms part of the skull.

contains: cerebral surface, zygomatic process.

Projection of the temporal bone that joins the temporal process of the zygomatic bone

Zygomatic process

Arch formed by the temporal and zygomatic bones which forms cheekbone. also apart of zygomatic process

Zygomatic arch

Region surrounding the external acoustic meatus

Tympanic region

Contains: styloid process

Needlelike projection inferior to the external acoustic meatus

Styloid process

Rough projection behind the ear that anchors neck muscles.

Mastoid process

Most massive region of the temporal bone contributing to the cranial base

Petrous region

Contains: jugular foramen, carotid canal, foramen lacerum, internal acoustic meatus

Opening transmitting the internal jugular vein and cranial nerves nine ten and eleven

Jugular foramen

Passageway for the internal carotid artery within temporal bone

Carotid canal

Opening between the temporal and sphenoid bones that is mostly closed by cartilage in life

Foramen lacerum

Passageway transmitting cranial nerves seven and eight

Internal acoustic meatus

Bat shaped cranial bone spanning the width of the cranial floor and forming anterior plateau of middle cranial fossa

Sphenoid bone (1)

Has 3 PAIRS of PROCESSES (projections)

(greater wings, lesser wings, pterygoid processes)

Large processes of the sphenoid that contribute to the eye orbits

Greater wings

Smaller bat shaped portion located anterior to the sella turcica of the sphenoid bone

Lesser wings

Vertical sphenoid projections providing attachment for muscles that move the lower jaw and soft palate

Pterygoid processes

Turkish saddle shaped structure on the superior sphenoid

Sella turcica

Contains: anterior clinoid processes, tuberculum sellae, posterior clinoid processes, optic groove (foramen), optic canal

Depression within the sella turcica holding the pituitary gland

Hypophyseal fossa

Anterior border of the sella turcica

Tuberculum sellae

Posterior border of the sella turcica

Dorsum sellae

Groove located anterior to the sella turcica in the sphenoid bone

Optic groove

Openings at either end of the optic groove

Optic canals

Opening transmitting cranial nerve two in the sphenoid bone

Optic foramen

Long slit between the greater and lesser sphenoid wings transmitting cranial nerves three four and six

Superior orbital fissure (cleft in bone)

Opening transmitting a branch of cranial nerve five

Foramen rotundum

Opening posterior to the sella turcica transmitting a branch of cranial nerve five

Foramen ovale

Opening transmitting the middle meningeal artery within the sphenoid bone

Foramen spinosum

Deeply situated cranial bone anterior to the sphenoid

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

Ethmoid bone (1)

Three major parts of the ethmoid bone

1. Cribriform plates

2. ethmoidal labyrinth

3. perpendicular plate

Within ethmoid bone. Structures forming part of the roof of the nasal cavities and floor of the anterior cranial fossa

Cribriform plates

Contain: Olfactory Foramina, Crista Galli

Apart of Cribriform plates, Small openings transmitting olfactory fibers of cranial nerve one

Transmits sense of smell

Olfactory foramina

Apart of Cribriform plates. Superior projection between the cribriform plates in the ethmoid bone that helps secure the brain

Crista galli

Within ethmoid bone. Network of interconnected ethmoidal air cells. Dominated by superior and middle nasal conchae

Ethmoidal labyrinth

Scroll shaped structures of the ethmoid (labyrinth) extending into the nasal cavity

Superior and middle nasal conchae

Within ethmoid bone. Structure forming the superior part of the nasal septum

projects inferiorly in the medial plane and superior portion is covered by olfactory epithelium

Perpendicular plate

Suture between the frontal and parietal bones

Coronal suture

Suture between the parietal and temporal bones

Squamous suture

Suture where the right and left parietal bones meet

Sagittal suture

Suture between the parietal and occipital bones

Lambdoid suture

Suture between the frontal bone and nasal bones

Frontonasal suture

Suture between the occipital and temporal bones

Occipitomastoid suture

Lower jawbone and only movable skull bone

Mandible

Horizontal portion of the mandible supporting the teeth

Mandibular body

Ascending portions on each side of the mandibular body

Rami

Areas where the mandibular rami meet the body

Mandibular angles

Thickened mandibular area containing the sockets and roots of the teeth

Alveolar margin

Posterior processes forming the heads of the mandible

Condylar processes

Heads of the mandible articulating with the temporal bones

Mandibular condyles

Anterior projections of the mandibular rami serving as attachment sites for the temporalis muscle

Coronoid processes

Depression between the condylar and coronoid processes

Mandibular notch

Openings on the anterior mandible transmitting mental nerves and blood vessels

Mental foramina

Line on the medial mandible marking the origin of the mylohyoid muscle

Mylohyoid line

Depression containing the submandibular salivary gland

Submandibular fossa

Openings on the medial mandibular rami transmitting branches of cranial nerve five

Mandibular foramina

Paired bones forming the upper jaw and central facial skeleton

Maxillae (2)

Processes of the maxillae forming the anterior hard palate

Palatine processes

Processes of the maxillae forming part of the bridge of the nose

Frontal processes

Processes of the maxillae articulating with the zygomatic bones

Zygomatic processes

Opening beneath each orbit transmitting infraorbital nerves and vessels

Infraorbital foramen

Margins of the maxillae containing the upper teeth

Alveolar margins

Bones forming the cheekbones and part of the lateral orbital rims

lateral to maxillae, contributes to orbital wall

Zygomatic bones (2)

Process of the zygomatic bone that joins the temporal bone

Temporal process

Opening transmitting a sensory nerve supplying the cheek

Zygomaticofacial foramen

Small rectangular bones forming the bridge of the nose

Articulates with the frontal bone at the frontonasal suture

Nasal bones (2)

Delicate fingernail shaped bones in the medial portions of the orbits

Articulates with the frontal bone at the frontonasal suture

Lacrimal bones (2)

Groove in the lacrimal bone leading toward the nasolacrimal canal

Lacrimal groove

Canal enclosing the tear duct as it passes toward the nasal cavity

Nasolacrimal canal

Small L shaped bones forming the posterior portion of the hard palate

Palatine bones (2)

Horizontal portions of the palatine bones forming the posterior hard palate

Horizontal plates

Slender plow shaped bone forming the posterior and inferior nasal septum

Articulates with both the maxillae and palatine bones along the midline

Vomer (1)

Thin curved scroll shaped bones projecting into the nasal cavity

Perform same functions as the conchae of the ethmoid

Inferior nasal conchae (2)