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NEET MDS Synopsis - Lecture Notes
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📖 Anatomy

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Extrinsic Muscles of the Tongue
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.
The Temporomandibular Joint
Anatomy

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
The Soft Palate
Anatomy

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 Occipital Bone
Anatomy

-> 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.