Embryology ,Anatomy and physiology of Larynx. Prepaired by: Dr. Hiwa As’ad Abdulkareem. Sources : Scott-browns of otolaryngology , head and neck surgery . Synopsis of otolaryngology . www.drtbalu.com www.wekipedia.com. Embryology of larynx. Development of larynx :
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Dr. Hiwa As’ad Abdulkareem
Development of larynx :
Any congenital malformation of the pharynx and oesophagus is always
associated with certain degree of malformation of larynx and trachea.
The infantile larynx:
By the falls and
true vocal cords.
epiglottis and aryepiglottic folds as they sweep down to
the arytenoids. Its lower border is the ventricular bands
(false cords) which form the upper border of the glottis .
commissure and posterior commissure.
Consists of :
the action of the two groups of muscles.
that is continuous above with the pharynx
and below with that of the trachea .
HYOID BONE :
It consists of:
(thyroid, cricoid , epiglottis)
(arytenoid , corniculate ,cuneiform)
processes known as the superior and inferior cornua.
1. Thyrohyoid muscle .
2. Sternohyoid muscle .
3. Inferior constrictor muscle .
Tow movements occur :
Tow movements occur :
Extrinsic and Intrinsic ligaments .
Extrinsic ligaments: connect the laryngeal cartilages to the hyoid bone above
and trachea below.
Divided into :
upper and lower part by the presence of laryngeal ventricle.
The lower part is a thicker membrane, containing many elastic fibers. It is also known as cricovocal ligamentorcricothryoid ligament or conuselasticus.
Hyoid bone above and trachea below .
and maintain the position of the
larynx in the neck .
Divided Into :
( Thyrohyoid , Sternothyroid ,
Sternohyoid , omohyoid ) .
( Mylohyoid , Geniohyoid, Stylohyoid ,
Digastric, Stylopharyngeus ,
Palatopharyngeus , Salpingopharyngeus (
Fig. show strap muscles of the neck
All of the infrahyoid muscles are innervated by the ansa cervicalis from the cervicalplexus (c1-c3 ) except the thyrohyoid muscle, which is innervated by fibres only from the 1st cervical signal nerve travelling with the hypoglosal nerve .
folds and control the elasticity and viscosity of each layer .
Divided into :
Except transverse arytenoid, all these muscles are paired.
Adducts the vocal ligaments by rotating the arytenoids medially.
Opener of laryngeal inlet :
Fibers of thyro-epiglottic muscle is apart of the thyro-arytenoid muscle widens the inlet of the larynx by pulling the ary-epiglottic folds slightly apart .
in to the ary- epiglotic fold .
All intrinsic muscles of the larynx are supplied by recurren laryngeal nerve except
Crico-thyroid m. which is supplied by external laryngeal nerve ..
The laryngeal cavity extends from the level of 3rd cervical vertebra to the lower border of the cricoid cartilage (c6) level. At the level of cricoid cartilage it becomes continuous with that of the trachea.
Laryngeal cavity is divided by the presence of vestibular and vocal folds into:
lie at a lower level. The covering epithelium is closely bound down to the underlying vocal ligament. The blood supply is poor, hence the pearly white appearance of the vocal cords.
Histologically the vocal fold:
contains 5 layers:
Along with the intermediate layer constitute the vocal ligament.
The pyriform recesses (pyriform sinuses) are present on either side of the anterolateral wall of the laryngopharynx. They are bounded medially by the aryepiglottic folds and laterally by the thyroid cartilage and thyrohyoid membrane. They are a common place for food to become trapped.
The superior thyroid artery arises from the external carotid artery, and the inferior thyroid artery arises from the thyrocervical trunk.
The veins leaving the larynx accompany the arteries;
way of the superior thyroid or facial veins ,
into the brachiocephalic veins.
through the middle thyroid vein into the internal jugular vein.
Separated by the vocal folds into an upper and lower group:
The larynx is supplied by branches of vagus nerve .
Internal branch . Entirly sensory . It pierces the thyrohyoid membrane with the
superior laryngeal artery and vien . It supplies the cavity of the larynxas far down
the level of the vocal cords .
External branch . Travels down on the inferior constrictor muscleof the pharynx . It supplies the cricothyroid muscle and part of the ant. Subglottis .
It has much longer course on the left side than on the right side .
On the lt. side it Turns round the arch of aorta .
On the rt. Side it Turns round the subclavian artery.
In the neck it lies between the trachea and oesophagus as it approach the larynx .
Its terminal part pass upwards , under cover of ala of the thyroid cartilage , immidiately behind the cricothyroid joint.
Devided In to :
Physiology of Larynx
1. Airway protection
Aryepiglottic fold, ventricular band and vocal cords.
from the airway.
The larynx acts as a transducer during phonation converting the aerodynamic forces generated by the lungs, diaphragm, chest and abdominal muscles into acoustic energy.
The requirements of normal phonation are as follows:
1. Active respiratory support
2. Adequate glottic closure
3. Normal mucosal covering of the vocal cord
4. Adequate control of vocal fold length and tension.