Skull Bones and Anatomy Notes

The human skull consists of two major groups of bones: $8$ cranial bones that surround and protect the brain, and $14$ facial bones that form the underlying structure of the face and support the teeth.
With the exception of the mandible, the skull bones articulate with each other through joints called sutures.
Throughout the skull, openings called foramina serve as passageways for blood vessels and nerves.
Surface (external) skull bones encase the brain, protect sensory organs, and provide attachment sites for muscles of the head and neck.
The listed bones on the surface include the occipital bone, parietal bones, temporal bones, frontal bone, nasal bones, zygomatic bones, maxilla, and mandible.
Some bones become more visible when looking inside the skull and are described in detail below.

Eight cranial bones: occipital, two parietal bones, two temporal bones, and the frontal bone.
Fourteen facial bones: nasal bones, two zygomatic bones, two maxillae, mandible, and others implied by the general description (the transcript lists these broadly as facial bones that form the face and support teeth).
Mandible is the exception to sutural articulation pattern, as it does not articulate with other bones via cranial sutures in the same way as the others.
Foramina are scattered throughout the skull to house vessels and nerves.

The sphenoid bone makes up the anterior base of the cranium.
It is butterfly-shaped with a central body and two pairs of laterally projecting wings.
The wings form portions of the orbit (eye socket).
The sphenoid body features a depression called the sella turcica, which houses the pituitary gland.
Significance: the sphenoid anchors several other bones and contributes to the stability and complexity of the cranial base and orbits.

Located between the orbits.
Forms part of the cranial floor and the roof of the nasal cavity.
The inferior projection, the perpendicular plate of the ethmoid bone, forms part of the nasal septum.
Crista galli projects superiorly from the ethmoid bone and serves as the attachment point for the falx cerebri, a dural fold.
Extending laterally from the crista galli is the cribriform plate, a perforated area through which the olfactory nerves pass.
The cribriform plate allows olfactory nerve fibers to pass from the nasal cavity to the brain.
Clinical relevance: the ethmoid contributes to the integrity of the nasal cavity and the sense of smell; its location relates to potential pathways for infection spread from the nasal cavity to the cranial cavity.

The two L-shaped palatine bones form:
- The posterior third of the hard palate.
- Part of the nasal cavity.
- A portion of the orbit.
Significance: palatine bones contribute to the architecture of the oral-nasal-orbital complex and support dental alignment indirectly via the hard palate.

The lacrimal bones are small and thin.
They form the anterior portion of the medial wall of each orbit.
A groove called the lacrimal groove helps to form the nasolacrimal canal.
The nasolacrimal canal contains a duct that carries tears from the eye to the nasal cavity.
Significance: lacrimal bones are involved in tear drainage and eye protection functions.

The vomer is an elongated bone forming the inferior and posterior part of the nasal septum.
Significance: the vomer contributes to separating the nasal cavities and supports nasal airflow regulation.

The internal and external skull bones articulate precisely, forming an intricate structure perfectly suited to protecting the brain, supporting sensory organs, and accommodating muscular attachments.
The overall design enables protection of neural tissue, stabilization of the face and cranium, and pathways for neurovascular structures.

Relationship to sutures: sutures allow growth during development and gradually ossify with age, contributing to skull shape and strength.
Clinical relevance: knowledge of these bones and their connections is essential in neurosurgery, dentistry, ENT, and forensic anthropology.
Practical implications: understanding foramina and caniculi helps in diagnosing nerve or vessel pathologies and planning surgical approaches.

Foramina: openings for blood vessels and nerves throughout the skull.
Suture: joint between skull bones (except mandible) that allows growth and later fixation.
Sella turcica: saddle-shaped depression on the sphenoid bone that houses the pituitary gland.
Crista galli: vertical projection on the ethmoid bone; attachment for falx cerebri.
Falx cerebri: dural fold that partitions the brain.
Cribriform plate: sieve-like area of the ethmoid through which olfactory nerves pass.
Nasolacrimal canal: duct system for tear drainage from the eye to the nasal cavity.
Nasal septum: divides the nasal cavity; formed partly by the perpendicular plate of the ethmoid and the vomer.
Orbit: bony cavity containing the eye; formed partly by the sphenoid, ethmoid, lacrimal, maxilla, zygomatic, and palatine bones.
Hard palate: bony front part of the roof of the mouth; formed in part by the palatine bones and maxillae.

Cranial bones: $8$
Facial bones: $14$
Sphenoid: butterfly-shaped with a central body and two pairs of wings; sella turcica houses the pituitary gland.
Ethmoid: between orbits; perpendicular plate; crista galli; cribriform plate; olfactory nerves pass through.
Palatine bones: two, L-shaped; form posterior hard palate and parts of nasal cavity and orbit.
Lacrimal bones: anterior medial wall of orbits; lacrimal groove and nasolacrimal canal.
Vomer: inferior/posterior nasal septum.
Overall: internal and external skull bones articulate to form a protective and functional cranial structure.