NEET MDS Lessons
Anatomy
Extrinsic Muscles of the Tongue (p. 746)
The Genioglossus Muscle
- This is a bulky, fan-shaped muscle that contributes to most of the bulk of the tongue.
- It arises from a short tendon from the genial tubercle (mental spine) of the mandible.
- It fans out as it enters the tongue inferiorly and its fibres attach to the entire dorsum of the tongue.
- Its most inferior fibres insert into the body of the hyoid bone.
- The genioglossus muscle depresses the tongue and its posterior part protrudes it.
The Hyoglossus Muscle
- This is a thin, quadrilateral muscle.
- It arises from the body and greater horn of the hyoid bone and passes superoanteriorly to insert into the side and inferior aspect of the tongue.
- It depresses the tongue, pulling its sides inferiorly; it also aids in retrusion of the tongue.
The Styloglossus Muscle
- This small, short muscle arises from the anterior border of the styloid process near its tip and from the stylohyoid ligament.
- It passes inferoanteriorly to insert into the side and inferior aspect of the tongue.
- The styloglossus retrudes the tongue and curls its sides to create a trough during swallowing.
The Palatoglossus Muscle
- Superior attachment: palatine aponeurosis.
- Inferior attachment: side of tongue.
- Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
- This muscle, covered by mucous membrane, forms the palatoglossal arch.
- The palatoglossus elevates the posterior part of the tongue and draws the soft palate inferiorly onto the tongue.
Innervation of the Pharynx
- The motor and most of the sensory supply of the pharynx is derived from the pharyngeal plexus of nerves on the surface of the pharynx.
- The plexus is formed by pharyngeal branches of the vagus (CN X) and glossopharyngeal (CN IX) nerves, and by sympathetic branches for the superior cervical ganglion.
- The motor fibres in the pharyngeal plexus are derived from the cranial root of accessory nerve (CN XI), and are carried by the vagus nerve to all muscles of the pharynx and soft palate.
- The exceptions are stylopharyngeus (supplied by CN IX) and the tensor veli palatini (supplied by CN V3).
Muscles of the larynx
Extrinsic muscles
suprahyoid: raise larynx, depress mandible for swallowing
infrahyoid: lower larynx for swallowing
both stabilize hyoid for tongue movements
The Articular Capsule
- The capsule of this joint is loose.
- The thin fibrous capsule is attached to the margins of the articular area on the temporal bone and around the neck of the mandible.
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.
|
Mesodermal Origin |
Muscles |
Innervation |
|
Somitomeres 1, 2 |
Superior, medial and ventral recti |
Oculomotor (III) |
|
Somitomere 3 |
Superior oblique |
Trochlear (IV) |
|
Somitomere 4 |
Jaw-closing muscles |
Trigeminal (V) |
|
Somitomere 5 |
Lateral rectus |
Abducens (VI) |
|
Somitomere 6 |
Jaw-opening and other 2nd arch muscles |
Facial (VII) |
|
Somitomere 7 |
Stylopharyngeus |
Glossopharyngeal (IX) |
|
Somites 1, 2 |
Intrinsic laryngeals |
Vagus (X) |
|
Somites 2-5 |
Tongue muscles |
Hypoglossal (XII) |
MUSCLE
Types:
Skeletal (voluntary)
Cardiac (involuntary)
Smooth (involuntary)