NEET MDS Lessons
Anatomy
Internal Muscles of the Pharynx
- The internal, chiefly longitudinal muscular layer, consists of 3 muscles: stylopharyngeus, palatopharyngeus, and salpingopharyngeus.
- They all elevate the larynx and pharynx during swallowing and speaking.
The Stylopharyngeus Muscle
- This is a long, thin, conical muscles that descends inferiorly between the external and internal carotid arteries.
- It enters the wall of the pharynx between the superior and middle constrictor muscles.
- Origin: styloid process of temporal bone.
- Insertion: posterior and superior borders of thyroid cartilage with palatopharyngeus muscle.
- Innervation: glossopharyngeal nerve (CN IX).
- It elevates the pharynx and larynx and expands the sides of the pharynx, thereby aiding in pulling the pharyngeal wall over a bolus of food.
The Palatopharyngeus Muscle
- This is a thin muscle and the overlying mucosa form the palatopharyngeal arch.
The Salpingopharyngeus Muscle
- This is a slender muscle that descends in the lateral wall of the pharynx.
- The over lying mucous membrane forms the salpingopharyngeal fold.
- Origin: cartilaginous part of the auditory tube.
- Insertion: blends with palatopharyngeus muscle.
- Innervation: through the pharyngeal plexus.
- It elevates the pharynx and larynx and opens the pharyngeal orifice of the auditory tube during swallowing.
The Submandibular Glands
- Each of these U-shaped salivary glands is about the size of a thumb and lies along the body of the mandible.
- It is partly superior and partly inferior to the posterior 1/2 of the base of the mandible.
- It is partly superficial and partly deep to the mylohyoid muscle.
- The submandibular duct arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscle.
- The duct passes deep and then superficial to the lingual nerve.
- It opens by one to three orifices on a small sublingual papilla beside the lingual frenulum.
- The submandibular gland is supplied by parasympathetic, secretomotor fibres from the submandibular ganglion (preganglionic fibres from the chorda tympani via the lingual nerve).
The Palate
- The palate forms the arched roof of the mouth and the floor of the nasal cavities.
- The palate consists of two regions: the anterior 2/3 or bony part, called the hard palate, and the mobile posterior 1/3 or fibromuscular part, known as the soft palate.
The Hard Palate
- The anterior bony part of the palate is formed by the palatine process of the maxillae and the horizontal plates of the palatine bones.
- Anteriorly and laterally, the hard palate is bounded by the alveolar processes and the gingivae.
- Posteriorly, the hard palate is continuous with the soft palate.
- The incisive foramen is the mouth of the incisive canal.
- This foramen is located posterior to the maxillary central incisor teeth.
- This foramen is the common opening for the right and left incisive canals.
- The incisive canal and foramen transmit the nasopalatine nerve and the terminal branches of the sphenopalatine artery.
- Medial to the third molar tooth, the greater palatine foramen pierces the lateral border of the bony palate.
- The greater palatine vessels and nerve emerge from this foramen and run anteriorly into two grooves on the palate.
- The lesser palatine foramen transmits the lesser palatine nerve and vessels.
- This runs to the soft palate and adjacent structures.
The Temporomandibular Joint
- This articulation is a modified hinge type of synovial joint.
- The articular surfaces are: (1) the head or condyle of the mandible inferiorly and (2) the articular tubercle and the mandibular fossa of the squamous part of the temporal bone.
- An oval fibrocartilaginous articular disc divides the joint cavity into superior and inferior compartments. The disc is fused to the articular capsule surrounding the joint.
- The articular disc is more firmly bound to the mandible than to the temporal bone.
- Thus, when the head of the mandible slides anterior on the articular tubercle as the mouth is opened, the articular disc slides anteriorly against the posterior surface of the articular tubercle
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| Motor Innervation | All muscles by hypoglossal nerve (CN XII) except palatoglossus muscle (by the pharyngeal plexus) | ||
| General Sensory Innervation |
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| Special Sensory Innervation |
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The Pharynx
- The pharynx is the continuation of the digestive system from the oral cavity.
- It is a funnel-shaped fibromuscular tube that is the common route for both food and air.
- The pharynx is located posterior to the nasal and oral cavities, and the larynx.
- For the convenience of description, the pharynx is divided into three parts: (1) the nasopharynx, posterior to the nose and superior to the soft palate; (2) the oropharynx, posterior to the mouth; and (3) the laryngopharynx, posterior to the larynx.
- The pharynx is about 15 cm long.
- It extends from the base of the skull to the inferior border of the cricoid cartilage anteriorly, and to the inferior border of C6 vertebra posteriorly.
- It is widest (about 5 cm) opposite the hyoid bone and narrowest (about 1.5) at its inferior end, where it is continuous with the oesophagus.
- The posterior wall of the pharynx lies against the prevertebral fascia, with the potential retropharyngeal space between them.
Movements of the Temporomandibular Joint
- The two movements that occur at this joint are anterior gliding and a hinge-like rotation.
- When the mandible is depressed during opening of the mouth, the head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the articular tubercle.
- As this anterior gliding occurs, the head of the mandible rotates on the inferior surface of the articular disc.
- This permits simple chewing or grinding movements over a small range.
- Movements that are seen in this joint are: depression, elevation, protrusion, retraction and grinding