NEET MDS Lessons
Anatomy
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 Layers of the Pharyngeal Wall
- The pharyngeal wall is composed of 5 layers. From internal to external, they are as follows.
- Mucous membrane: this lines the pharynx and is continuous with all chambers with which it communicates.
- Submucosa
- Pharyngobasilar fascia: this is a fibrous layer that is attached to the skull.
- Muscular layer: this is composed of inner longitudinal and outer circular parts.
- Buccopharyngeal fascia: this is a loose connective tissue layer.
- This fascia is continuous with the fascia covering the buccinator and pharyngeal muscle.
- It contains the pharyngeal plexus of nerves and veins.
Intrinsic muscles
all innervated by recurrent laryngeal nerve except cricothyroid: external laryngeal nerve
adductors of vocal folds: bring folds together at midline
Transverse and oblique arytenoids: pull arytenoids together
Lateral cricoartenoids: spin and slide arytenoids up
only one abductor of vocal folds
Posterior cricoarytenoids—down and up
adjustors of shape and tension of vocal folds
Cricothyroid muscle
o superficial to lateral cricoarytenoid
o tenses vocal folds by tilting thyroid cartilage forward and sliding forward
Thyroartenoid and vocalis muscles
o vocalis: sometimes treated as medial most fibers of thyroartenoid muscle
o different fiber directions
lateral: adduct
medial: change shape of folds
control voice by bring bringing together different parts of folds
o as move from epithelium to vocalis muscle, fold becomes stiffer
o near connections, vocal folds are stiffer
o vocal fold: complex, multilayered vibrator
Structure of the Nasal Septum
- This part bony, part cartilaginous septum divides the chamber of the nose into two narrow nasal cavities.
- The bony part of the septum is usually located in the median plane until age 7; thereafter, it often deviates to one side, usually the right.
- The nasal septum has three main components: (1) the perpendicular plate of the ethmoid bone; (2) the vomer, and (3) the septal cartilage.
- The perpendicular plate, which forms the superior part of the septum, is very thin and descends from the cribiform plate of the ethmoid bone.
- The vomer, which forms the posteroinferior part of the septum, is a thin, flat bone. It articulates with the sphenoid, maxilla and palatine bones.
- 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.
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Part of the axial skeleton; strong, flexible rod
Supports the head
Gives base to the ribs
Encloses the spinal cord
o Vertebrae
Consists of 34 bones composing the spinal column
• Cervical-7 bones
• Thoracic-12 bones
• Lumbar-5 bones
• Sacral- 5 bones.
• Coccygeal-4 to 5 bonesIn the adult the vertebrae of the sacral and coccygeal regions are united into two bones, the sacrum and me coccyx
o Curvatures-from a lateraI view there are four curves, alternately convex and concave ventrally
Two convex curves are the cervical and lumbar
Two concave curves are the thoracic and sacralo Vertebra morphology
Each vertebra differs in size and shape hut has similar components
Body-central mass of bone
• Weight bearing
• Fonns anterior part of the vertebra
• Encloses the vertebral foramen
Pedicles of the arch-two thick columns that extend backward from the body to meet with the laminae of the neural arch -
Process (7)
• One spinous, two transverse, two superior articular, and two inferior articular
o Spinous process extends backward from the point of the union of thetwo laminae
o Transverse processes project laterally at either side from the junction of the lamina and the pedicle
o Articular processes arise near the junction of the pedicle and the lamina- superior processes project upward:inferior processes project downward
• Surfaces of the processes are smootho Inferior articular processes of the vertebra fit into the superior articular processes below
o Form true joints, but the contacts established serve to restrict movementDistinguishing features
Cervical region- triangular shape
• All have foramina in the transverse process upper six transmit the vertebral artery
• Spinous processes are short
o C3 to C5 are bifurcated
o C7 is long-prominence felt at the back of the neck
• Have small bodies (except for C1 vertebra)
• C1 vertebra (atlas)
o No body
o Anterior and posterior arch and two lateral masses
o Superiorarticular processes articulate with the condyles of the occipital bone
• C2 vertebra (axis)-process on the upper surface of the body (dens) forms a pivot about which the axis rotatesThoracic region
• Presence of facets for articulation with the ribs (distinguishing feature)
• Processes are larger and heavier than those of the cervical region
• Spinous process is directed downward at a sharp angle
• Circular vertebral foramenLumbar region
• Large and heavy bodies
• Four transverse lines separate the bodies of the vertebrae on the pelvic surface
• Triangular shape-fitted between the halves of the pelvis
• Four pairs of dorsal sacral foramina communicate with four pairs of pelvic sacral foraminaSacral vertebrae
• Five (sometimes six) vertebrae are fused in the adult to form the sacrum
• The sacrum articulates above with L5, laterally with the hip bones, and inferiorly with the coccyx.
• It has a roughly triangular appearance with a pelvic and dorsal surface, a lateral mass on each side, and a base and apex.
• An anesthetic for the spinal nerves may be injected extradurally through the sacral hiatus (caudal analgesia)
• The sacral canal (which contains the dura, cauda equina, and filum terminale) extends from the base to the sacral hiatus.
• The apex of the sacrum may be fused with the coccyx.
Coccygeal vertebrae• Four to five modular pieces fused together
• Triangular shape with the base above and the apex belowF Defects
• Lordosis-exaggerated lumbar concavity
• Scoliosis-lateral curvature of any region
• Kyphosis-exaggerated convexity in the thoracic region
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.