TLDR;
This lecture provides a comprehensive review of the anatomy of the head, face, and neck, focusing on key areas such as venous drainage, sensory and motor nerve supply, triangles of the neck, and specific structures like the parotid gland, pharynx, middle ear, and tongue. It covers clinical applications, including the dangerous area of the face, nerve injuries, and muscle function.
- Venous drainage of the face and the dangerous area.
- Sensory and motor nerve supply of the face, including the trigeminal and facial nerves.
- Triangles of the neck and their contents, with emphasis on the posterior triangle and the spinal accessory nerve.
- Anatomy of the parotid gland, pharynx, middle ear, and tongue, including nerve supply and clinical considerations.
Venus Drainage and Dangerous Area of the Face [1:11]
The facial venous system begins with the supraorbital and supratrochlear veins merging into the angular vein at the medial angle of the eye. The angular vein continues as the facial vein. The superficial temporal and maxillary veins join to form the retromandibular vein, which divides into anterior and posterior divisions. The anterior division joins the facial vein to form the common facial vein, draining into the internal jugular vein. The posterior division joins the posterior auricular vein to form the external jugular vein, which drains into the subclavian vein. The dangerous area of the face, comprising the lower part of the nose and upper lip, is significant because infections from this area can spread directly to the cavernous sinus via the facial vein, angular vein, and superior ophthalmic vein, or via the deep facial vein, pterygoid venous plexus, and emissary vein.
Sensory Nerve Supply of the Face [8:03]
The sensory nerve supply of the face is primarily from the trigeminal nerve, except for the skin over the angle of the mandible, which is supplied by the greater auricular nerve from the cervical plexus. The ophthalmic division supplies the forehead via the supraorbital and supratrochlear nerves, as well as the infratrochlear, external nasal, and lacrimal nerves. The maxillary division supplies the infraorbital, zygomaticofacial, and zygomaticotemporal areas. The mandibular division provides sensory innervation via the mental nerve, auriculotemporal nerve, and buccal nerve. The buccal nerve, a branch of the trigeminal nerve, supplies the skin over the buccinator muscle, while the buccal branch of the facial nerve provides motor innervation to the buccinator muscle.
Motor Nerve Supply of the Face [12:39]
The motor nerve supply of the face is primarily the facial nerve, which exits the parotid gland via five branches: temporal, zygomatic, buccal, marginal mandibular, and cervical. The cervical branch of the facial nerve supplies the platysma muscle.
Triangles of the Neck [13:38]
The neck is divided into anterior and posterior triangles by the sternocleidomastoid muscle. The posterior triangle is further divided into occipital and supraclavicular triangles by the inferior belly of the omohyoid muscle. The anterior triangle is bordered by the midline of the neck, the sternocleidomastoid, and the mandible. The digastric muscle divides the anterior triangle into digastric and carotid triangles. The muscular triangle is bordered by the midline of the neck, the superior belly of the omohyoid, and the sternocleidomastoid. The anterior belly of the digastric is supplied by the mandibular nerve, while the posterior belly is supplied by the facial nerve, reflecting their origins from the first and second pharyngeal arches, respectively.
Posterior Triangle of the Neck [36:11]
The posterior triangle of the neck is bounded by the sternocleidomastoid, trapezius, and clavicle. The floor is formed by the semispinalis capitis, splenius capitis, levator scapulae, scalenus posterior, and scalenus medius muscles, covered by the prevertebral fascia. The contents include the subclavian artery, the brachial plexus (specifically the supraclavicular part), the spinal accessory nerve, and branches of the cervical plexus. The spinal accessory nerve supplies the sternocleidomastoid and trapezius muscles. Damage to this nerve during lymph node excision can cause winging of the scapula and difficulty in overhead abduction. The cervical plexus branches include the lesser occipital, greater auricular, transverse cervical cutaneous, and supraclavicular nerves. The roof of the posterior triangle consists of skin, superficial fascia, and the investing layer of the deep cervical fascia.
Muscular Triangle and Ansa Cervicalis [49:30]
The muscular triangle contains the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles. The ansa cervicalis, formed by the superior root (C1) and inferior root (C2-C3), innervates the sternohyoid, sternothyroid, and omohyoid muscles, but not the thyrohyoid, which is supplied by C1 directly. The ansa cervicalis lies on the anterior wall of the carotid sheath.
Parotid Gland Anatomy [54:49]
The parotid gland has three surfaces: superficial, anteromedial, and posteromedial. The anteromedial surface is related to the ramus of the mandible, masseter, and medial pterygoid muscles. The posteromedial surface is related to the sternocleidomastoid and posterior belly of the digastric. The gland has a true capsule (condensation of connective tissue) and a false capsule (investing layer of deep cervical fascia). Contents include the facial nerve, retromandibular vein, and external carotid artery. The nerve supply is via the glossopharyngeal nerve, originating from the inferior salivatory nucleus. The tympanic branch of the glossopharyngeal nerve (Jacobson's nerve) forms the tympanic plexus on the promontory of the middle ear, giving rise to the lesser petrosal nerve, which synapses in the otic ganglion. Postganglionic fibers are carried to the parotid gland via the auriculotemporal nerve. Frey's syndrome involves sweating of the skin over the parotid gland during salivation due to mixing of auriculotemporal and greater auricular nerve fibers.
Muscles of Mastication [1:02:46]
The muscles of mastication include the temporalis, masseter, medial pterygoid, and lateral pterygoid, all supplied by the mandibular nerve. The anterior division of the mandibular nerve supplies the masseter, temporalis, and lateral pterygoid, while the trunk of the mandibular nerve supplies the medial pterygoid.
Cranial Foramina [1:07:59]
Key cranial foramina and their contents include:
- Foramen Rotundum: Maxillary nerve.
- Foramen Ovale: Mandibular nerve, accessory meningeal artery, lesser petrosal nerve, and emissary vein (MALE).
- Foramen Spinosum: Nervous spinosus and middle meningeal artery.
- Foramen Lacerum: Internal carotid artery and deep petrosal nerve.
- Internal Acoustic Meatus: Facial nerve (VII), vestibulocochlear nerve (VIII), and labyrinthine artery.
- Jugular Foramen: Divided into anterior (inferior petrosal sinus), middle (IX, X, XI cranial nerves), and posterior (sigmoid sinus) compartments.
- Hypoglossal Canal: Hypoglossal nerve.
- Superior Orbital Fissure: Oculomotor (III), trochlear (IV), abducens (VI), and ophthalmic division of trigeminal nerve (V1).
Dural Venous Sinuses and Cavernous Sinus [1:13:12]
Dural venous sinuses are formed by the splitting of the dura mater into endosteal and meningeal layers. Paired sinuses include the cavernous, sphenoparietal, superior petrosal, inferior petrosal, transverse, and sigmoid sinuses. Unpaired sinuses include the superior sagittal, inferior sagittal, straight, and occipital sinuses. The cavernous sinus is related medially to the pituitary gland and sphenoid air sinus, and laterally to the third, fourth, ophthalmic, and maxillary nerves. The sixth nerve and internal carotid artery lie in the floor, and the optic chiasm is in the roof. Tributaries include the superior ophthalmic, inferior ophthalmic, and central vein of retina from the orbit; the sphenoparietal sinus from the meninges; and the superficial middle cerebral and inferior cerebral veins from the brain.
Pharynx [1:19:18]
The pharynx consists of superior, middle, and inferior constrictor muscles. Structures passing above the superior constrictor (through the sinus of Morgagni) include the Eustachian tube, levator veli palatini muscle, ascending palatine artery, and palatine branches of the ascending pharyngeal artery. Between the superior and middle constrictors pass the glossopharyngeal nerve and stylopharyngeus muscle. Between the middle and inferior constrictors pass the internal laryngeal nerve and superior laryngeal vessels. Below the inferior constrictor pass the recurrent laryngeal nerve and inferior laryngeal vessels. All constrictor muscles are supplied by the pharyngeal plexus, except the cricopharyngeus part of the inferior constrictor, which is supplied by the external or recurrent laryngeal nerve.
Middle Ear Anatomy [1:23:20]
The middle ear is bounded laterally by the tympanic membrane. The anterior wall contains the Eustachian tube and tensor tympani muscle, and is separated from the internal carotid artery. The posterior wall features the aditus to the mastoid, pyramidal eminence (attachment of stapedius muscle), and facial nerve. The medial wall (promontory) exhibits the tympanic plexus, oval window (closed by footplate of stapes), round window (closed by secondary tympanic membrane), facial canal, and prominence of the lateral semicircular canal. The floor contains the internal jugular vein, and the roof is formed by the petrous part of the temporal bone. The nerve supply is the glossopharyngeal nerve.
Tongue Anatomy [1:27:48]
The tongue is divided into anterior two-thirds and posterior one-third. The anterior two-thirds contain foliate, fungiform, filiform, and circumvallate papillae. The posterior one-third consists of lymphoid tissue. The inferior surface features the frenulum linguae, lingual veins, and plica fimbriata. Intrinsic muscles (superior longitudinal, inferior longitudinal, vertical, and transverse) alter the shape of the tongue. Extrinsic muscles (styloglossus, palatoglossus, hyoglossus, and genioglossus) control its position. All tongue muscles are supplied by the hypoglossal nerve, except the palatoglossus, which is supplied by the pharyngeal plexus. The genioglossus is the safety muscle of the tongue, protruding it to the opposite side. In hypoglossal nerve lesions, the tongue deviates to the same side as the lesion.
Soft Palate Muscles [1:32:25]
The muscles of the soft palate include the tensor veli palatini, levator veli palatini, palatoglossus, palatopharyngeus, and musculus uvulae. All are supplied by the pharyngeal plexus, except the tensor veli palatini, which is supplied by the mandibular nerve.