NEET MDS Lessons
Anatomy
The Nose
- The nose is the superior part of the respiratory tract and contains the peripheral organ of smell.
- It is divided into right and left nasal cavities by the nasal septum.
- The nasal cavity is divided into the olfactory area and the respiratory area.
The Temporalis Muscle
- This is an extensive fan-shaped muscle that covers the temporal region.
- It is a powerful masticatory muscle that can easily be seen and felt during closure of the mandible.
- Origin: floor of temporal fossa and deep surface of temporal fascia.
- Insertion: tip and medial surface of coronoid process and anterior border of ramus of mandible.
- Innervation: deep temporal branches of mandibular nerve (CN V3).
- The temporalis elevates the mandible, closing the jaws; and its posterior fibres retrude the mandible after protrusion.
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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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First pouch |
Auditory tube, which comes in contact with epithelial line of first pharyngeal cleft, where future external acoustic meatus will form. Distal portion will form tympanic cavity (lining will become eardrum) Proximal portion will become auditory tube |
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Second pouch |
Forms buds that penetrate surrounding mesenchyme, which together form the palatine tonsils |
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Third pouch |
Forms thymus and inferior parathyroid glands |
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Fourth pouch |
Forms superior parathyroid glands |
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Fifth pouch |
Forms utlimobranchial body |
The Masseter Muscle
- This is a quadrangular muscle that covers the lateral aspect of the ramus and the coronoid process of the mandible.
- Origin: inferior border and medial surface of zygomatic arch.
- Insertion: lateral surface of ramus of mandible and its coronoid process.
- Innervation: mandibular nerve via masseteric nerve that enters its deep surface.
- It elevates and protrudes the mandible, closes the jaws and the deep fibres retrude it.
The Lips
- These are mobile muscular folds that surround the mouth, the entrance of the oral cavity.
- The lips (L. labia) are covered externally by skin and internally by mucous membrane.
- In between these are layers of muscles, especially the orbicularis oris muscle.
- The upper and lower lips are attached to the gingivae in the median plane by raised folds of mucous membrane, called the labial frenula.
Sensory Nerves of the Lips
- The sensory nerves of the upper and lower lips are from the infraorbital and mental nerves, which are branches of the maxillary (CN V2) and mandibular (CN V3) nerves.
The Nasopharynx
- The nasal part of the pharynx has a respiratory function.
- It lies superior to the soft palate and is a posterior extension of the nasal cavity.
- The nose opens into the nasopharynx via to large posterior apertures called choanae.
- The roof and posterior wall of the nasopharynx form a continuous surface that lies inferior to the body of the sphenoid bone and the basilar part of the occipital bone.
- In the mucous membrane of the roof of the posterior wall of the nasopharynx is a collection of lymphoid tissue, known as the pharyngeal tonsil (commonly known as the adenoids).
- The pharyngeal orifice of the auditory tube is on the lateral wall of the nasopharynx, 1 to 1.5 cm posterior to the inferior concha, and level with the superior border of the palate.
- The orifice is directed inferiorly and has a hood-like tubal elevation over it called the torus of the auditory tube or the torus tubarius (L. torus, swelling).
- Extending inferiorly from the torus is a vertical fold of mucous membrane, known as the salpingopharyngeal fold.
- The collection of lymphoid tissue in the submucosa of the pharynx, posterior to the orifice of the auditory tube, is known as the tubal tonsil.
- Posterior to the torus and the salpingopharyngeal fold, there is a slit-like lateral projection of the pharynx called the pharyngeal recess.
- It extends laterally and posteriorly.