Larynx

Question 1

Extent, Cartilages, Joints, Ligaments, Muscles of Larynx?

Answer 1

Extent: From upper border of epiglottis to lower border of cricoid cartilage (C6 level)

Cartilages: 6 (3 in pairs, 3 unpaired)— Arytenoid, Cuneiform, Corniculate are in pairs. Thyroid, cricoid and epiglottis are unpaired.

Joints: Cricothyroid & Cricoarytenoid (both synovial)

Ligaments:
Extrinsic- Thyrohyoid, Hyoepiglottic ligament, Cricotracheal ligament.
Intrinsic - A broad fibroblastic membrane of larynx, consists of two parts, separated by the sinus of larynx. Part above the sinus - quadrate membrane. Part below the sinus is called cricovocal membrane.
The lower free margin of Quadrate memb thickened to form Vestibular lig.and upper margin forms Aryepiglottic fold.
Upper margin of cricovocal membrane thickened to form Vocal lig.

Question 2

Muscles of Larynx?

Answer 2

2 types- Intrinsic (9) and Extrinsic (5)

Intrinsic -

1) Cricothyroid 2) Lat. Cricoarytenoid 3) Post. Cricoarytenoid
4) Thyroepiglotticus 5)Aryepiglotticus 6) Thyroarytenoid
7) Transverse arytenoid 8) Oblique arytenoid
9) Vocalis

Extrinsic - Palatopharyngeus, Salpingopharyngeus, Stylopharyngeus, Thyrohyoid, Sternothyroid

Question 3

Actions of the Intrinsic muscles of Larynx?

Answer 3

1) Abduction of vocal cord - Post. Cricoarytenoid muscle
2) Adduction of vocal cord - Lat. Cricoarytenoid & Transverse arytenoid, Cricothyroid, Thyroarytenoid
3) Tensor of vocal cord - Cricothyroid
4) Relaxor of vocal cord - Thyroarytenoid, Vocalis
5) Opening inlet - Thyroepiglotticus
6) Closing inlet - Aryepiglotticus , Oblique arytenoid

Question 4

Extrinsic muscles of larynx and their action?

Answer 4

Stylopharyngeus ,Palatopharyngeus ,Salpingopharyngeus and Thyrohyoid elevate the larynx.

Sternothyroid depresses the larynx.

Question 5

Mechanism of phonation.

Answer 5

6 steps:

1) Vocal cords adducted
2) Infraglottic air pressure increased by air exhaled from lungs, by contraction of abdominal, intercostal and other exploratory muscles.
3) Force of air (Resonator) pushes the vocal cords to open, and air is released in small puffs.
4) Air passing between the vocal cords (Vibrator) causes them to vibrate, producing sound.
5) Sound amplified by mouth, pharynx, nose, esophagus
6) Speech is produced by articulators ie., tongue, palate, lips, teeth, pharynx

Vowels produced by vibration of vocal cords. Consonants by intrinsic muscles of tongue.

Question 6

Clinical aspect of nerve supply of muscles of larynx.

Answer 6

All intrinsic muscles get motor supply by RLN except Cricothyroid which is supplied by Ext Laryngeal nerve.

Damage to RLN on one side occurs commonly during partial Thyroidectomy— paralysis of the affected half of Rima glottidis. Affected sides’ vocal cord remains in paramedian position. The other vocal cord compensates for this, thus phonation is possible with slight hoarseness. No Respiratory difficulty.

Damage to RLN of both sides —> aphonic with respiratory difficulty on exertion

Bilateral damage of both RLN and Ext LN —> complete paralysis of all intrinsic muscles of larynx. The Rima glottidis is further ABDUCTED in position and both vocal cords are fixed. This is called cadaveric position of vocal cords.

Question 7

Short Note: Rima Glottidis.

Answer 7

Def: It is the narrow anteroposterior cleft in the cavity of larynx b/w the vocal folds.

Boundaries: 
Anterior- Angle of thyroid 
Posterior- Interarytenoid mucous fold
Laterally- 
anterior 3/5th :Vocal cords 
posterior 2/5th: Vocal process of Arytenoid cartilage 

Structure: Mucous memb lined by non keratinised stratified squamous epithelium. Devoid of submucosa.

Shape and movement:

1) Normal breathing- Pentagonal
2) Full inspirn. - diamond (PCA contracts)
3) High pitched voice- Slit like (Oblique and Transverse arytenoids contract)
4) Whispering - inverted funnel (Lateral CA contracts)

Question 8

Subdivisions of laryngeal cavity?

Answer 8

1) Vestibule - Funnel shaped- B/w Aryepiglottic fold and Vestibular fold.
2) Sinus of Larynx - B/w vestibular and vocal folds- Presents a mucous recess of either side. On the ant aspect of the recess, a diverticulum called Saccule of larynx opens. Contains mucous glands for lubrication of Rima and vocal cords (oil can of larynx)
3) Infraglottic part - below the vocal cords - truncated cone shaped.