Head and Neck: Skull Bones, Cranial Nerves, and Associated Structures

Head and Neck Anatomy

Overview of Topics

This unit covers the anatomical structures of the head and neck, focusing on the skull bones, cranial nerves, special sense organs, glands, muscles, pharynx, larynx, and neurovasculature. Understanding these components is essential for comprehending the functional organization and clinical relevance of the head and neck region.

• Skull bones: Roofing, cranial base, and facial bones

• Cranial nerves and brain

• Face, oral cavity, nasal cavity

• Organs of special senses

• Glands

• Neck muscles

• Pharynx and larynx

• Neurovasculature of head and neck

Skull Bones

Classification of Skull Bones

The skull is composed of several bones that protect the brain and form the structure of the face. These bones are classified into three main groups:

• Roofing bones: Frontal, Parietal (2)

• Cranial base bones: Ethmoid, Sphenoid, Temporal (2), Occipital

• Facial bones: Maxilla, Zygomatic, Nasal, Lacrimal, Inferior nasal concha, Vomer, Mandible, Palatine

Major Sutures and Fontanelles

Sutures are immovable joints between skull bones, while fontanelles are soft spots in the fetal and infant skull that allow for growth.

• Sutures: Sagittal, Coronal, Squamosal, Lambdoidal

• Fontanelles: Anterior (closes 18–24 months), Posterior (2–3 months), Sphenoidal (6 months), Mastoid (6–18 months)

Cranial Base Bones

Ethmoid Bone

The ethmoid bone forms part of the anterior cranial base and the nasal cavity. It contains the crista galli, perpendicular plate, cribriform plate, and nasal conchae.

• Crista galli: Attachment for the falx cerebri

• Cribriform plate: Passage for olfactory nerves (CN I)

• Superior and middle nasal conchae: Increase surface area in the nasal cavity

Sphenoid Bone

The sphenoid bone is a central bone of the cranial base, contributing to the floor of the cranium and the orbits. It contains the body, lesser and greater wings, pterygoid processes, and several foramina for cranial nerves.

• Optic canal: Passage for optic nerve (CN II)

• Superior orbital fissure: Passage for CN III, IV, V1, VI

• Foramen rotundum: Passage for maxillary nerve (CN V2)

• Foramen ovale: Passage for mandibular nerve (CN V3)

• Hypophyseal fossa: Houses the pituitary gland

Temporal Bone

The temporal bone houses structures for hearing and balance and forms part of the cranial base and lateral skull.

• Regions: Squamous, tympanic, mastoid, petrous

• Key features: External and internal acoustic meatus, zygomatic process, styloid process

• Foramina: Passage for facial (CN VII) and vestibulocochlear (CN VIII) nerves

Occipital Bone

The occipital bone forms the posterior part of the cranial base and contains the foramen magnum for the spinal cord.

• Regions: Squamous, basilar

• Foramen magnum: Passage for medulla oblongata and vertebral arteries

• Hypoglossal canal: Passage for hypoglossal nerve (CN XII)

• Jugular foramen: Passage for CN IX, X, XI and internal jugular vein

• Carotid canal: Passage for internal carotid artery

Cranial Nerves and Foramina

Overview of Cranial Nerves

The cranial nerves exit the cranium through foramina in the cranial base bones. Each nerve has a specific function, including sensory, motor, or both.

• CN I: Olfactory (smell)

• CN II: Optic (vision)

• CN III: Oculomotor (eye movement)

• CN IV: Trochlear (eye movement)

• CN V: Trigeminal (facial sensation, mastication)

• CN VI: Abducens (eye movement)

• CN VII: Facial (facial expression, taste)

• CN VIII: Vestibulocochlear (hearing, balance)

• CN IX: Glossopharyngeal (taste, swallowing)

• CN X: Vagus (parasympathetic control)

• CN XI: Spinal accessory (neck muscles)

• CN XII: Hypoglossal (tongue movement)

Key Foramina and Their Contents

Foramen	Bone	Contents
Cribriform plate	Ethmoid	Olfactory nerves (CN I)
Optic canal	Sphenoid	Optic nerve (CN II)
Superior orbital fissure	Sphenoid	CN III, IV, V1, VI
Foramen rotundum	Sphenoid	Maxillary nerve (CN V2)
Foramen ovale	Sphenoid	Mandibular nerve (CN V3)
Internal acoustic meatus	Temporal	CN VII, VIII
Jugular foramen	Occipital/Temporal	CN IX, X, XI; Internal jugular vein
Hypoglossal canal	Occipital	Hypoglossal nerve (CN XII)
Carotid canal	Temporal	Internal carotid artery

Facial Bones

Major Facial Bones and Their Functions

The facial bones form the structure of the face, support the teeth, and contribute to the orbits and nasal cavity.

• Maxilla: Upper jaw, forms part of the hard palate

• Zygomatic: Cheekbone

• Nasal: Bridge of the nose

• Lacrimal: Medial wall of orbit

• Inferior nasal concha: Lateral wall of nasal cavity

• Vomer: Inferior part of nasal septum

• Mandible: Lower jaw, only movable skull bone

• Palatine: Posterior part of hard palate

Additional Info

• The skull bones are joined by sutures, which ossify with age.

• Fontanelles allow for brain growth and facilitate childbirth.

• Special sense organs (smell, vision, hearing, balance) are closely associated with cranial base bones and their foramina.