Muscles of the Pharynx

• This consists of three constrictor muscles and three muscles that descend from the styloid process, the cartilaginous part of the auditory tube and the soft palate.

External Muscles of the Pharynx 

• The paired superior, middle, and inferior constrictor muscles form the external circular part of the muscular layer of the wall.
• These muscles overlap each other and are arranged so that the superior one is innermost and the inferior one is outermost.

• These muscles contract involuntarily in a way that results in contraction taking place sequentially from the superior to inferior end of the pharynx.
• This action propels food into the oesophagus.

• All three constrictors of the pharynx are supplied by the pharyngeal plexus of nerves, which lies on the lateral wall of the pharynx, mainly on the middle constrictor of the pharynx.
• This plexus is formed by pharyngeal branches of the glossopharyngeal (CN IX) and vagus (CN X) nerves.

The Superior Constrictor Muscle

• Origin: pterygoid hamulus, pterygomandibular raphe, posterior end of the mylohyoid line of the mandible, and side of tongue.
• Insertion: median raphe of pharynx and pharyngeal tubercle.
• Innervation: though the pharyngeal plexus of nerves.

• The pterygomandibular raphe is the fibrous line of junction between the buccinator and superior constrictor muscles.

The Middle Constrictor Muscle

• Origin: stylohyoid ligament and greater and lesser horns of hyoid bone.
• Insertion: median raphe of pharynx.
• Innervation: through the pharyngeal plexus of nerves.

The Inferior Constrictor Muscle

• Origin: oblique line of thyroid cartilage and side of cricoid cartilage.
• Insertion: median raphe of pharynx.
• Innervation: through the pharyngeal plexus of nerves.

• The fibres arising from the cricoid cartilage are believed to act as a sphincter, preventing air from entering the oesophagus. 

Gaps in the Pharyngeal Musculature

• The overlapping arrangement of the three constrictor muscles leaves 4 deficiencies or gaps in the pharyngeal musculature.
• Various structures enter and leave the pharynx through these gaps.

• Superior to the superior constrictor muscle, the levator veli palatini muscle, the auditory tube, and the ascending palatine artery pass through a gap between the superior constrictor muscle and the skull.
• Superior to the superior border of the superior constrictor, the pharyngobasilar fascia blends with the buccopharyngeal fascia to form, with the mucous membrane, the thin wall of the pharyngeal recess.

• Between the superior and middle constrictor muscles, the gateway to the mouth, though which pass the stylopharyngeus muscle, the glossopharyngeal nerve (CN IX), and the stylohyoid ligament.

• Between the middle and inferior constrictor muscles, the internal laryngeal nerve and the superior laryngeal artery and vein pass to the larynx.

• Inferior to the inferior constrictor muscles, the recurrent laryngeal nerve and inferior laryngeal artery pass superiorly into the larynx.

Structure of the Nasal Septum

• This part bony, part cartilaginous septum divides the chamber of the nose into two narrow nasal cavities.
• The bony part of the septum is usually located in the median plane until age 7; thereafter, it often deviates to one side, usually the right.

• The nasal septum has three main components: (1) the perpendicular plate of the ethmoid bone; (2) the vomer, and (3) the septal cartilage.

• The perpendicular plate, which forms the superior part of the septum, is very thin and descends from the cribiform plate of the ethmoid bone.
• The vomer, which forms the posteroinferior part of the septum, is a thin, flat bone. It articulates with the sphenoid, maxilla and palatine bones.

Nerves of the Palate

• The sensory nerves of the palate, which are branches of the pterygopalatine ganglion, are the greater and lesser palatine nerves.
• They accompany the arteries through the greater and lesser palatine foramina, respectively.

• The greater palatine nerve supplies the gingivae, mucous membrane, and glands of the hard palate.

• The lesser palatine nerve supplies the soft palate.

• Another branch of the pterygopalatine ganglion, the nasopalatine nerve, emerges from the incisive foramen and supplies the mucous membrane of the anterior part of the hard palate.

Vessels of the Palate

• The palate has a rich blood supply from branches of the maxillary artery.

-> This bone forms much of the base and posterior aspect of the skull.
-> It has a large opening called the foramen magnum, through which the cranial cavity communicates with the vertebral canal.
-> It is also where the spinal cord becomes continuous with the medulla (oblongata) of the brain stem.
-> The occipital bone is saucer-shaped and can be divided into four parts: a squamous part (squama), a basilar part (basioccipital part), and two lateral parts (condylar parts).
-> These four parts develop separately around the foramen magnum and unite at about the age of 6 years to form one bone.
-> On the inferior surfaces of the lateral parts of the occipital bone are occipital condyles, where the skull articulates with C1 vertebra (the atlas) at the atlanto-occipital joints.
-> The internal aspect of the squamous part of the occipital bone is divided into four fossae: the superior two for the occipital poles of the cerebral hemispheres, and the inferior two, called cerebellar fossae, for the cerebellar hemispheres.

The Auditory Ossicles

The Malleus

• Its superior part, the head, lies in the epitympanic recess.
• The head articulates with the incus.

• The neck, lies against the flaccid part of the tympanic membrane.
• The chorda tympani nerve crosses the medial surface of the neck of the malleus.

• The handle of the malleus (L. hammer) is embedded in the tympanic membrane and moves with it.
• The tendon of the tensor tympani muscle inserts into the handle.

The Incus

• Its large body lies in the epitympanic recess where it articulates with the head of the malleus.
• The long process of the incus (L. an anvil) articulates with the stapes.
• The short process is connected by a ligament to the posterior wall of the tympanic cavity.

The Stapes

• The base (footplate) of the stapes (L. a stirrup), the smallest ossicle, fits into the fenestra vestibuli or oval window on the medial wall of the tympanic cavity.

Functions of the Auditory Ossicles

• The auditory ossicles increase the force but decrease the amplitude of the vibrations transmitted from the tympanic membrane.

Veins of the Face

The Supratrochlear Vein

• This vessel begins on the forehead from a network of veins connected to the frontal tributaries of the superficial temporal vein.
• It descends near the medial plane with its fellow on the other side.
• These veins diverge near the orbits, each joining a supraorbital vein to form the facial vein near the medial canthus (angle of the eye).

The Supraorbital Vein

• This vessel begins near the zygomatic process of the temporal bone.
• It joins the tributaries of the superficial and middle temporal veins.
• It passes medially and joins the supratrochlear vein to form the facial vein near the medial canthus.

The Facial Vein

• This vein provides the major venous drainage of the face.

• It begins at the medial canthus of the eye by the union of the supraorbital and supratrochlear veins.
• It runs inferoposteriorly through the face, posterior to the facial artery, but takes a more superficial and straighter course than the artery.
• Inferior to the margin of the mandible, the facial vein is joined by the anterior branch of the retromandibular vein.
• The facial veins ends by draining into the internal jugular vein.

The Superficial Temporal Vein

• This vein drains the forehead and scalp and receives tributaries from the veins of the temple and face.
• In the region of the temporomandibular joint, this vein enters the parotid gland.

The Retromandibular Vein

• The union of the superficial temporal and maxillary veins forms this vessel, posterior to the neck of the mandible.
• It descends within the parotid gland, superficial to the external carotid artery but deep to the facial nerve.
• It divides into an anterior branch that unites with the facial vein, and a posterior branch that joins the posterior auricular vein to form the external jugular vein.