NEET MDS Lessons
Anatomy
The Auditory Tube
- This is a funnel-shaped tube connecting the nasopharynx to the tympanic cavity.
- Its wide end is towards the nasopharynx, where it opens posterior to the inferior meatus of the nasal cavity.
- The auditory tube is 3.5 to 4 cm long; its posterior 1/3 is bony and the other 2/3 is cartilaginous.
- It bony part lies in a groove on the inferior aspect of the base of the skull, between the petrous part of the temporal bone and the greater wing of the sphenoid bone.
- The function of the auditory tube is to equalise pressure of the middle ear with atmospheric pressure.
- The palate has a rich blood supply from branches of the maxillary artery.
The Ear
- The ear contains the vestibulocochlear organ and consists of three main parts: external, middle, and internal.
- It has two functions, balance and hearing.
- The tympanic membrane (eardrum) separates the external ear from the middle ear.
- The auditory tube joins the middle ear or tympanic cavity to the nasopharynx.
The Walls of the Orbit
- Each orbit has four walls: superior (roof), medial, inferior (floor) and lateral.
- The medial walls of the orbit are almost parallel with each other and with the superior part of the nasal cavities separating them.
- The lateral walls are approximately at right angles to each other
Mylohyoid Muscle
- Origin: Mylohyoid line of the mandible.
- Insertion: Median raphe and body of the hyoid bone.
- Nerve Supply: Nerve to mylohyoid (branch of the trigeminal nerve, CN V3).
- Arterial Supply: Sublingual branch of the lingual artery and submental branch of the facial artery.
- Action: Elevates the hyoid bone, base of the tongue, and floor of the mouth; depresses the mandible.
The Soft Palate
- This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
- The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
- It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).
- The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.
- During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.
- Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.
- The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
- This aponeurosis attaches to the posterior margin of the hard palate.
The Frontalis Muscle
- The frontalis muscle is part of the scalp muscle called the occipitalfrontalis.
- The frontalis elevates the forehead, giving the face a surprised look, and produces transverse wrinkles in the forehead when one frowns.