BIO 201: Lab 2

Cranial Bones (8 bones)

encase and protect the brain and help form the structure of the skull.

calvaria

(also known as the cranial vault or skullcap), which is the dome-like upper portion of the skull.

cranial base

supports the brain and contains three major depressions called cranial fossae (Note: “fossa” is singular)

The three major depressions (cranial fossae)

- Anterior cranial fossa
- Middle cranial fossa
- Posterior cranial fossa

Cranial fossae

support, cradle, and protect the different regions of the brain. They also contain important foramina (openings) for nerves and blood vessels to pass through the skull.

sutures

immovable fibrous joints that join cranial bones together

Facial Bones (14 bones)

• Do not directly protect the brain

• Support structures such as the eyes, nose, and mouth

• Help form the oral and nasal cavities

• Serve as attachment sites for muscles involved in facial expression and chewing

Paranasal Sinuses

air-filled cavities lined with mucous membranes and connected to the nasal cavity

Paranasal Sinuses functions include:

• Filtering, warming, and humidifying inhaled air

• Reducing skull weight

• Enhancing vocal resonance

Paranasal sinuses are found in the following bones:

• Frontal bones

• Maxillae bones

• Ethmoid bones

• Sphenoid bones

• Temporal bones (specifically the mastoid sinuses)

• Air enters these sinuses through small openings from the nasal cavity.

Orbit

the eye socket

Nasal cavity

supports breathing and olfaction

Oral cavity

essential for speech, breathing, and eating

Zygomatic arch

contributes to the prominence of the cheek

Hard palate

forms the roof of the mouth

Bony nasal septum

divides the nasal cavity into left and right sides

Sutures

fibrous, immovable joints between skull bones (primarily cranial).

Synovial joints

freely movable joints, such as the temporomandibular joint (TMJ), which connects the mandible to the temporal bone and allows movement of the jaw.

Frontal Bone

An unpaired bone that forms the anterior portion of the cranium and the superior part of the orbit (eye sockets) and the anterior cranial fossa

Glabella

smooth area between the eyes

Supraorbital foramina

two small holes located over the anterior ridge (brow area) of the orbit

Supraorbital margin

the anterior ridge (brow area) of the orbit

Frontal sinuses

paranasal sinus

Parietal Bones

Large dome shaped pair of bones that form the superior and lateral walls of the cranium.

Sagittal suture

located at the midline, the left and right parietal bones meet at this joint

Coronal suture

located anterior to the parietal bones, meets the frontal bone at this joint

Lambdoid suture

located posterior to the parietal bones, they meet the occipital bone at this joint

Squamous suture

located lateral to the parietal bones, they meet the temporal bones at this joint

Pterion

• Location: Anterolateral side of the skull

• Bones Involved: Frontal, Temporal, Parietal, Sphenoid (4 bones)

• Meaning: Pterion means "wing"

• Anagram: SPF-T

Asterion

• Location: Posterolateral side of the skull

• Bones Involved: Temporal, Occipital, Parietal (3 bones)

• Meaning: Asterion means "star"

• Anagram: TOP (Think of it this way: TOP students get a star)

Bregma

• Location: Superior anterior aspect of the skull

• Bones Involved: Frontal bone and Parietal bones (3 bones)

Lambda

• Location: Superior posterior aspect of the skull

• Bones Involved: Parietal bones and Occipital bone (3 bones)

Temporal Bones

Paired bones that form the lateral walls of the cranium (temple) and part of the middle cranial fossa

Squamous region

This flat region is the temporal bone’s most lateral portion. It is largely flat in appearance

Zygomatic process

a projection that forms the posterior part of the zygomatic arch or cheekbone. It is named after the zygomatic bone which it is connected to.

Mandibular fossa

just inferior to the zygomatic process is an indentation/depression which forms the temporomandibular joint (TMJ) or the jaw joint, with the mandible bone.

Tympanic region

refers to a drumhead

External acoustic meatus

an opening to the external auditory canal, a tubular passageway that leads to the middle and inner ear

Styloid process

a needle-like projection, serves as an attachment point for a neck muscle

Mastoid region

refers to a portion that resembles a round or breast-like section. It is located posterior to the tympanic region

Mastoid process

a prominent, round bony projection that serves as an attachment site for several neck muscles.

Mastoid air cells

1. inside the mastoid process are numerous tiny, interconnected, air-filled spaces (paranasal sinus), it is also called mastoid sinuses. 

   1. These structures help regulate ear pressure and communicate with the middle ear.

   2. Inflammation and infection of these sinuses is called mastoiditis, which could damage the bone and spread to the brain. 

Mastoid notch

a shallow groove located medial to the mastoid process. It serves as an insertion point for one of the neck muscles. The notch is perforated by a hole called the stylomastoid foramen, which is an exit point for one of the cranial nerves that serves the face.

Petrous region

Internally, the temporal bone is shaped like a mountain ridge

Foramen lacerum

medial and anterior gash-like opening. It is formed by the junction of three bones - the temporal, occipital, and sphenoid bones. Nerves and blood vessels pass through this.

Carotid canal

middle tubular passage, described as large and circular. It is a passageway for a major artery. That's why you can hear your blood pulsing, since it is so close to the internal ear.

Jugular foramen

posterior irregularly-shaped and large hole. Its large size serves as a passageway for a major vein and an exit point for three cranial nerves

Internal acoustic meatus

1. an opening on its posteromedial surface. allows passage of a nerve that carries signals for hearing and balance form the inner ear to the brain.

Occipital Bone

A large singular cranial bone located posteriorly, it contains the posterior cranial fossa

Foramen magnum

its most conspicuous feature is found in its base, described as a large hole through which the spinal cord passes

Occipital condyles

• It forms the atlanto-occipital (AO) joint with the first cervical vertebra (atlas vertebra). 

  • A synovial joint that allows flexion and extension of the head.

Hypoglossal canal

located at the anterolateral edge of each condyle is this hidden passageway.  It is named after the cranial nerve that passes through it.

Superior and inferior nuchal lines

two prominent parallel horizontal ridges on the posterior side. Located at the exact midline of the superior nuchal line, we will find a large round bump called the external occipital protuberance.

Sphenoid Bone

This butterfly or wedge shaped bone is located posterior to the frontal and ethmoid bones and in the interior part of the skull. It also forms a part of the middle cranial fossa along with the temporal bone.

The sphenoid bone is often called the keystone bone of the skull because…

it articulates with more bones than any other cranial bone. It plays a central role in connecting both cranial and facial bones. It Articulates with 14 individual bones from 9 bone types:

Anagram

PEPTOZ-FMV

Cranial Bones (5 types, 7 bones)

• Frontal bone

• Parietal bones (left and right)

• Temporal bones (left and right)

• Occipital bone

• Ethmoid bone

• Facial Bones (4 types, 7 bones):

• Zygomatic bones (left and right)

• Maxillae bones (left and right)

• Palatine bones (left and right)

• Vomer bone

sphenoid body

part of the sphenoid bone

optic canals

consists of two medial, tubular passageways located on the superior surface of the sphenoid body

sphenoid sinus

one of the paranasal sinuses, which is lined with mucosa and helps lighten the skull and condition inhaled air, within the sphenoid body

sella turcica

a saddle-shaped structure/region superior to the sphenoid body

Tuberculum sellae

the thin, raised anterior margin/boundary; one of the landmarks of the sella turcica

Hypophyseal fossa

the central, inferior depression that houses the hypophysis or pituitary gland, an important endocrine organ often referred to as the “master gland” due to its regulatory role over many other glands; also a landmark of the sella turcica

Dorsum sellae

the thicker, posterior boundary/margin of the sella

lesser wings

the smaller, superior, and most anterior pair

greater wings

• the larger, inferior, and more posterior pair of the sphenoid bone

greater wings

the larger, inferior, and more posterior pair of the sphenoid bone

superior orbital fissure

sits between the lesser and greater wings; a narrow slit through which several cranial nerves for the extrinsic eye muscles pass

Foramen rotundum

anterior; It is located lateral and inferior to the optic canals within the greater wing

Foramen ovale

middle; large and oval-shaped, within the greater wing

Foramen spinosum

posterior; small and located near a small, spiny projection within the greater wing

pterygoid processes

The inferior extensions of the sphenoid

• Medial pterygoid plate and Lateral pterygoid plate

structures within the pterygoid process that form part of the posterior walls of the nasal and oral cavities. They also articulate with the vomer and palatine bones, which is best seen in inferior or midsagittal views of the skull

Ethmoid Bone

This singular cubical, complex, delicate, and porous bone, is also the most difficult to see from standard views of the skull

Complex Location and Contribution of the Ethmoid Bone

• Anterior to the sphenoid bone

• Posterior to the nasal bones

• Posterior and inferior to the frontal bone

• Superior to the vomer and inferior nasal conchae bones

• It also contributes to the:

  • medial wall of the orbit

  • roof and walls of the nasal cavity

  • superior portion of the bony nasal septum

cribriform plate

The superior surface of the ethmoid bone; forms the roof of the nasal cavity and part of the anterior floor of the cranial cavity

olfactory (cribriform) foramina

small holes that perforate the cribriform plate, through which olfactory nerves pass, giving it a porous appearance

crista galli

a vertical bony projection Rising from the midline of the cribriform plate; serves as an attachment point for part of the meninges of the brain

lateral masses

contribute to the medial wall of the orbits (via the orbital plates) and the walls of the nasal cavity

ethmoid sinuses

Internal within the lateral masses; are a network of air-filled spaces (paranasal sinuses)

Superior nasal conchae

one of the projections that extends medially from the lateral masses into the nasal cavity; hard to visualize in most skull models

Middle nasal conchae

a thin, curved bony projection that extends medially from the ethmoid bone into the nasal cavity. It is located inferior to the superior nasal concha and superior to the inferior nasal concha bones.

perpendicular plate

The inferior midline portion of the ethmoid bone which forms the superior part of the bony nasal septum.

bony nasal septum

(septa, plural) is the bony wall that divides the nasal cavity into right and left halves.

Mandible Bone

the lower jaw bone, consists of a central mandibular body and two “arms” called the mandibular rami (singular: ramus).

inferior alveolar margin

the mandibular body where the 16 lower teeth are attached

mental foramen

a small hole located on each side of the lateral mandibular body

mandibular angle

the angle in which the mandibular rami turns superiorly, lateral to the mental foramina

mandibular notch

A U-shaped notch that separates the two processes of the superior ends

coronoid process

The anterior process of one of the two processes

mandibular condyle

a posterior process

Maxillae Bones

These two fused bones are the upper jaw bones.

Maxillae Bones form the…

• inferior wall of the orbit

• part of the lateral wall of the nasal cavity

• part of the superior wall of the oral cavity.

inferior orbital fissure

a slit inside the orbit, where the maxilla meets the sphenoid bone; serves as a passageway for nerves and blood vessels

infraorbital foramen

a small hole inferior to the orbit which is where a cranial nerve passes through.

palatine processes.

process in which the maxillae bones form the anterior two-thirds of the hard palate

hard palate

the border between the nasal and oral cavities. Within their walls are cavities called the maxillary sinuses, a paranasal sinus

zygomatic processes

projections that form part of the cheekbone

frontal process of the maxilla bone

a superior projection located between the nasal and lacrimal bones