Head and Neck Anatomy: Sinuses, Nerves, and Muscles

Head and Neck Anatomy

Meninges and Sinuses

Falx Cerebri

Located between the two cerebral hemispheres.

Falx Cerebelli

Located between the two cerebellar hemispheres.

Tentorium Cerebelli

Located between the cerebrum and cerebellum.

Single Sinuses

• Superior sagittal sinus
• Inferior sagittal sinus
• Straight sinus
• Occipital sinus
• Basilar sinus

Paired Sinuses

• Sphenoparietal sinus
• Cavernous sinus
• Superior petrosal sinus
• Inferior petrosal sinus
• Transverse sinus
• Sigmoid sinus

Cavernous Sinus

Site: Sphenoid bone, extending to the superior orbital fissure.

Size: 2cm long, 1cm wide.

Structures within the Lumen:

• Internal carotid artery
• Abducent nerve

Structures in the Lateral Wall:

• Oculomotor nerve
• Trochlear nerve
• Ophthalmic nerve
• Maxillary nerve

Tributaries:

• Ophthalmic vein
• Superficial middle cerebral vein
• Pterygoid plexus vein

Clinical Importance: Infection danger from the anterior facial vein, pterygoid plexus, and cavernous sinus thrombosis.

Eye

Extraocular Muscles

• Superior rectus
• Inferior rectus
• Lateral rectus
• Medial rectus
• Superior oblique
• Inferior oblique

Nerves

• Optic nerve (CN I): Vision, passes through the optic canal.
• Ophthalmic nerve (CN V1): Sensory nerve, passes through the superior orbital fissure.
• Oculomotor nerve (CN III), Trochlear nerve (CN IV), Abducent nerve (CN VI): Motor nerves, pass through the superior orbital fissure.

Lacrimal Apparatus

• Lacrimal gland: Secretes tears.
• Lacrimal sac: Collects tears.
• Nasolacrimal duct: Drains tears into the nasal cavity.

Ear

External Ear

• Auricle (pinna)
• Auditory canal
• Eardrum (separates external and middle ear)

Middle Ear

• Located within the petrous part of the temporal bone.
• Ossicles: Malleus, incus, stapes.

Internal Ear

• Located within the petrous part of the temporal bone.
• Cochlea: Anteriorly responsible for hearing.

Nose

Lateral Wall

• Three bony elevations: Superior, middle, and inferior turbinates.

Roof

Olfactory mucosa.

Floor

Palate separating the nasal and oral cavities.

Blood Supply

• Anterior and posterior ethmoidal arteries (from the ophthalmic artery)
• Sphenopalatine artery (from the maxillary artery)
• Septal branches (from the superior labial artery)

Nerve Supply

• Smell sensation: Olfactory nerve (CN I).
• General sensation: Short and long sphenopalatine nerves.

Paranasal Air Sinuses

• Frontal sinus
• Ethmoidal sinus
• Sphenoidal sinus
• Maxillary sinus

Functions

• Diminish the weight of the skull.
• Warming and humidification of air.
• Resonance of voice.

Platysma

Origin: Fascia of the front chest covering the pectoralis major and deltoid muscles.

Insertion: Lower border of the mandible.

Nerve Supply: Cervical branch of the facial nerve (CN VII).

Action: Wrinkles neck skin and depresses the mandible.

Cutaneous Nerves of the Neck

• Great auricular nerve
• Lesser occipital nerve
• Transverse cervical nerve
• Supraclavicular nerve

Superficial Veins of the Neck

• Anterior jugular vein: From the hyoid bone, descends through the superficial fascia, and joins the external jugular vein.
• External jugular vein: Forms below the angle of the mandible and descends along the sternocleidomastoid muscle.