skull

Anatomy:

8 cranial bones

14 facial bones

Cranium is divided in two parts: skull cap (calvarium) and floor of the cranium

Skull cap consists of: frontal bone, right and left parietal bone, and occipital bone

Floor of cranium consists of : right and left temporal, sphenoid, and ethmoid bone

4 main sutures:

Coronal suture is between the frontal and parietal bones

Sagittal suture is located on top of the head, between the right and left parietal bone

Lambdoidal suture is between the parietal bone and the occipital bone

Squamosal suture is between temporal and parietal bone

Fontanels:

“Soft spot/depression” on babies is called the anterior fontanel. As an adult, the area between the frontal and parietal bones is closed and it forms the bregma. 

Posterior of the sagittal suture for the baby is called posterior fontanel. As an adult, when it is fused together it is called lambda.

Pterion- the junction where the parietal bone and squasmosal suture and the greater wing of the sphenoid meets. 

Asterion- the junction where the occipital bone and parietal bone and the posterior portion of the temporal bone. 

Frontal bone (forehead) features include the supraorbital margin. The superior rim of each orbit. The superciliary ridge corresponds to the eyebrow. 

Glabella is between the superciliary ridge. Smooth area above the eyebrows. 

Parietal bones are squared in shape. Form majority of the skull and concaved laterally. The widest portion is located between the parietal eminences of the skull. Parietal eminence is from one end from the parietal to the other. 

Parietal bone articulates with the frontal, occipital, the right and left temporal, sphenoid bones.

Ethmoids lie primarily below the floor of the cranium. The horizontal portion of the ethmoid is called the cribiform plate. Off  the cribriform plate is a thick process that projects superiorly called the crista galli. The vertical portion of the ethmoid bone is called the perpendicular plate. The perpendicular plate is a part of the nasal septum. The ethmoid articulates with the frontal, sphenoid and 11 facial bones. 

Occipital bone is the posterior and inferior portion of the skull. Has a large opening at the base called the foramen magnum. Allows the medulla oblongata and spinal cord to pass through. External occipital protuberance is the prominence at the back of the skull and referred to as the inion. Gonion is the angle in the mandible, at the level C2-C3. The occipital bone articulates with the right/left parietal and right/left temporal and sphenoid and C1 (atlas). 

Temporal bone is located on the inferior lateral margin. There are two parts and a zygomatic process. Mandibular fossa is where the condyle of the mandible sits. TMJ specifically sits there. 

What forms the zygomatic arch: zygomatic portion of the temporal bone and the temporal portion of the zygoma. 

The petrous pyramid is a very dense portion of the bone. It is triangular in shape and contains the organs of hearing. Above it is the petrous ridge. TEA - top of ear attachment is at the level of the top of the petrous ridge.

Mastoid portion contains the mastoid air cells. The mastoid process is located behind the ear and is at the level of C1.

Temporal bone articulates with the right and left parietal bone, occipital bone and sphenoid bone. 

Sphenoid bone articulates with all cranial bones.Wedged shape and resembles a bat.

Forms the anchor of all the other cranial bones. 

The body is the central portion and houses the sphenoid sinus. 

The central depression of the sphenoid is known as the sella turcica. 

The pituitary gland sits at the sella turcica. The posterior wall of the sella turcica is formed by the dorsum sellae. 

The top portion is the posterior clinoid process. The anterior portion is the anterior clinoid process. Both form the saddle. 

There is a lesser and greater wing of the sphenoid. The greater wing includes the foramen ovale, foramen spinosum, and foramen rotundum. Nerves and vessels transmit. Demonstrated on certain projections. 

Sella turcica's centering point is ¾ of an inch anterior, ¾ of inch superior of the EAM