|Lecture: 14 Head and neck Dr. Omar Riadh
Formed from a complete ring of hyaline cartilage, it is like a signet ring and lies below the thyroid cartilage. It has a narrow anterior arch and a broad posterior lamina.
Is a leaf-shaped elastic cartilage situated behind the root of the tongue. It is connected in front to the body of hyoid bone, and by its stalk to the back of thyroid cartilage, the sides of the epiglottis are connected to arytenoid cartilages by aryepiglottic folds. The upper edge of epiglottis is free and the covering of mucous membrane is reflected forward on the posterior surface of the tongue, here a median glossoepiglottic fold and lateral glossoepiglottic folds are present. The vallecula are depressions of mucous membrane on either side of glossoepiglottic fold.
The arytenoid cartilages:-
Are small, and two in number, and pyramidal. They are situated in the back of larynx on the upper border of the lamina of the cricoid cartilage. They contain the vocal process and the muscular process.
The corniculate cartilage:-
Are two small nodules that articulate with the apices of the arytenoid cartilages and give attachment to aryepiglottic folds.
The cuneiform cartilages:-
Are two small rod-shaped pieces of cartilage each one placed on aryepiglottic folds they serve as support for the fold.
Inlet of the larynx:-
It looks backward and upward into the laryngeal part of pharynx. The opening is bounded in front by the upper margin of epiglottis, laterally by aryepiglottic folds of mucous membrane that connect the epiglottis to the arytenoid cartilage, and posteriorly and below by the mucous membrane stretching between the arytenoid cartilages. The corniculate cartilage and the cuneiform cartilages produce a small elevation on the upper border of each aryepiglottic fold.
Cavity of the larynx:-
Extends from the inlet to the lower border of cricoid cartilage. It is divided into three parts:-
The upper part (vestibule of the larynx):- extends from the inlet to the vestibular folds.
The vestibular fold (false vocal cord):- a fold of mucous membrane cover the underlying vestibular ligament.
Rima vestibuli:- is the gap between the vestibular folds.
The middle part of the larynx:- extends from the level of vestibular folds to the level of vocal folds.
The vocal fold (true vocal cord):- fold of mucous membrane covers the underlying vocal ligament.
Rima glottidis:- is the gap between the vocal folds.
Ventricle of the larynx (sinus):- is a narrow groove between the vestibular and vocal folds, and is partly undermines the vestibular fold.
Saccule of the larynx:- narrow blind diverticulum which passes posterosuperiorly between the vestibular fold and the thyroid cartilage.
The lower part of the larynx:- extends from the vocal fold to the lower border of cricoid cartilage.
Thin layer of fibro-elastic tissue separated from the laryngeal cavity by mucous membrane. It attached inferiorly to the upper border of cricoid cartilage and extends superomedially to ends in the free edge of the vocal fold as vocal ligament.
Muscles of the larynx:-
The muscles can divided into two groups:-
Extrinsic:- divided into two opposing groups:-
Elevators:- (digastric, stylohyoid, mylohyoid and geniohyoid).
Depressors:- (sternohyoid, sternothyroid and omohyoid).
Nerve supply of the larynx:-
1-sensory:- to the mucous membrane of the larynx above the vocal fold is from the internal laryngeal branch of superior laryngeal branch of the vagus nerve. Below the level of the vocal fold the mucous membrane is supplied by the recurrent laryngeal nerve.
2-motor:- to intrinsic muscles of the larynx is the recurrent laryngeal nerve except cricothyroid muscle which is supplied by external laryngeal branch of superior laryngeal branch of the vagus nerve.
Blood supply of the larynx:-
The arterial supply to the upper half of the larynx is from the superior laryngeal artery which is branch of superior thyroid artery, the lower half of the larynx is supplied by the inferior laryngeal artery which is branch of inferior thyroid artery.
Lymphatic drainage of the larynx:-
To the deep cervical lymph nodes.
Superomadially:- rectus capitis posterior major.
Below:- obliquus inferior.
Superolaterally:- obliquus superior.
It is crossed by greater occipital nerve which hooks around the lower border of obliquus inferior under cover of semispinalis capitis.
In the depth of the triangle are the posterior atlanto-occipital membrane and the posterior arch of atlas with the vertebral artery and the first cervical nerve on its superior aspect. Also the triangle contains the suboccipital plexus of vein which draining to the vertebral and deep cervical vein.
The greater occipital nerve is the medial branch of the dorsal rami of C2, is the thickest cutaneous nerve in the body, it emerges below the middle of the obliquus inferior muscle curves superomedially across the suboccipital triangle and pierces semispinalis capitis, it ascends on that muscle pierces trapezius muscle 2-3 cm lateral to external occipital protuberance. It is mainly cutaneous but supplies semispinalis capitis.