Anatomy of the Human Skull: Bones, Sutures, and Foramina

Skull Lab: Overview

Introduction to Skull Anatomy

The human skull is a complex structure composed of multiple bones, sutures, and foramina. It serves to protect the brain, support facial structures, and provide passageways for nerves and blood vessels. Understanding the anatomy of the skull is essential for students of Anatomy & Physiology, particularly in the study of the skeletal system.

Major Bones of the Skull

Cranial and Facial Bones

The skull is divided into cranial bones, which encase the brain, and facial bones, which form the structure of the face.

• Frontal Bone: Forms the forehead and the upper part of the eye sockets (orbits).

• Parietal Bone: Paired bones forming the sides and roof of the cranial cavity.

• Temporal Bone: Located at the sides and base of the skull; houses structures of the ear.

• Occipital Bone: Forms the back and base of the skull.

• Sphenoid Bone: Butterfly-shaped bone at the base of the skull, contributing to the floor of the cranial cavity and the sides of the orbits.

• Ethmoid Bone: Located between the eyes, forms part of the nasal cavity and the orbits.

• Nasal Bone: Small bones forming the bridge of the nose.

• Lacrimal Bone: Small bone forming part of the medial wall of each orbit.

• Zygomatic Bone: Cheekbone; forms the prominence of the cheeks and part of the orbit.

• Maxilla: Upper jawbone; forms the upper dental arch and part of the orbit and nasal cavity.

• Mandible: Lower jawbone; the only movable bone of the skull.

• Vomer: Forms part of the nasal septum.

Sutures of the Skull

Major Cranial Sutures

Sutures are immovable joints where cranial bones are fused together. They are important anatomical landmarks.

• Coronal Suture: Separates the frontal bone from the parietal bones.

• Squamous Suture: Separates the parietal bone from the temporal bone.

• Lambdoid Suture: Separates the occipital bone from the parietal bones.

Key Foramina of the Skull

Definition and Examples

A foramen is a natural opening or hole in a bone that allows the passage of nerves, arteries, or veins. Foramina are named according to their location.

• Supraorbital Foramen: Located above the orbit (eye socket); passage for the supraorbital nerve and vessels.

• Infraorbital Foramen: Located below the orbit; passage for the infraorbital nerve and vessels.

• Mental Foramen: Located on the anterior surface of the mandible; passage for the mental nerve and vessels.

• Foramen Magnum: Large opening at the base of the skull; allows the spinal cord to connect to the brain.

Internal Structures of the Skull

Base of the Skull

• Sphenoid Bone: Prominent internally, forming part of the cranial floor; its shape resembles a butterfly.

• Ethmoid Bone: Located between the eye sockets; forms part of the nasal cavity and the medial wall of the orbits.

• Foramen Magnum: The largest foramen at the base of the skull, crucial for the passage of the spinal cord.

Summary Table: Major Skull Structures

Structure	Location	Function/Notes
Frontal Bone	Forehead, upper orbit	Protects frontal lobe, forms forehead
Parietal Bone	Top and sides of skull	Protects parietal lobes
Temporal Bone	Side/base of skull	Houses ear structures
Occipital Bone	Back/base of skull	Contains foramen magnum
Sphenoid Bone	Base of skull, orbits	Butterfly-shaped, supports cranial floor
Ethmoid Bone	Between orbits	Forms nasal cavity, orbit walls
Nasal Bone	Bridge of nose	Supports nose structure
Lacrimal Bone	Medial orbit wall	Contains lacrimal fossa
Zygomatic Bone	Cheek, orbit	Forms cheek prominence
Maxilla	Upper jaw	Holds upper teeth
Mandible	Lower jaw	Movable, holds lower teeth
Vomer	Nasal septum	Divides nasal cavity
Coronal Suture	Frontal/parietal bones	Immovable joint
Squamous Suture	Parietal/temporal bones	Immovable joint
Lambdoid Suture	Occipital/parietal bones	Immovable joint
Supraorbital Foramen	Above orbit	Nerve/vessel passage
Infraorbital Foramen	Below orbit	Nerve/vessel passage
Mental Foramen	Mandible	Nerve/vessel passage
Foramen Magnum	Base of skull	Spinal cord passage

Additional info:

• In clinical practice, knowledge of skull foramina is essential for understanding nerve blocks and the spread of infections.

• Developmental anatomy: Sutures allow for growth of the skull during childhood and fuse in adulthood.