**   The larynx **
 د.حسين جاسم 
                                              
L.1 Surgical anatomy of the larynx
 
The larynx is situated in the midline from the level of the third to the sixth cervical vertebrae.
It consists of a framework of cartilages connected by ligaments and lined by a mucous membrane; in male the projection of the thyroid cartilage produces the Adam's apple.
Laryngeal cartilages:
Unpaired cartilages: These are three:
1. Thyroid cartilage:
     Is the largest one and each half consists of:
- Ala (lamina) which meet in the midline forming an angle of about 90 degree in  men and about 120 degree in women.
-  Superior cornu: arises from the posterosuperior angle of the ala.
- Inferior cornu: arises from the posteroinferior angle of the ala and articulate with the cricoid cartilage.
2. Cricoid cartilage:
Thicker and stronger than the thyroid cartilage, resembles a signet ring (narrow in front and broad. behind), articulate with the arytenoids cartilages on the upper border of the cricoid lamina.
3. Cartilage of epiglottis:
Rises up behind  the tongue, it is leaf like sheet of elastic fibro cartilage the stem directed downwards & is attached to the posterior surface of the thyroid ala at their junction -while the upper free border directed upwards.
    Paired cartilages: these are three pairs:
1. A rytenoid cartilages:
They are the largest, pyramidal-in shape, have the muscular process postero-laterally & the vocal process anterolaterally, articulate inferiorly with the cricoid cartilage -while the apex, curves backwards to articulate with the corniculate cartilage.
2. Corniculate cartilages (the cartilages of Santorini): 
        These are small articulate with the apices of the arytenoid cartilages and prolong them backward and medially.	 
3. Cuneiform cartilages (the cartilages of Wrisberg):
These are small bars of yellow elastic cartilages in each ary-epiglottic fold.
Laryngeal joints:
There are two important joints in the larynx on each side.
1. Crico-thyroid joint:
               It is between the inferior cornu of the thyroid cartilage and cricoid cartilage. It is a synovial joint with two movements (rotation and gliding).
2. Crico-arytenoid joint:
      It is also a synovial joint with the same two movements.
Laryngeal muscles:
These are two types:
I. Intrinsic (between the laryngeal cartilages):
                  - Abductors of the vocal cords:
         There is only one on each side named the posterior crico-arytenoid muscles which opens the glottis.
               - Adductors of the vocal cords:   There are three on each side:
1. Lateral crico-arytenoid muscle.
2. Interarytenoid muscle.
3. Thyroarytenoid muscle.
                  - Tensors of the vocal cords: these are two on each side:
1.  Cricothyroid muscle (external tensor).
2. Internal portion of the thyro-arytenoid (Vocalis, internal tensor).
II. Extrinsic (Between the larynx and the neighboring structures): There are two main groups:
1.  Strap muscles of the neck: sternothyroid & thyrohyoid muscles.
 2.  Pharyngeal muscles: stylopharyngeus, palatopharyngeus & inferior constrictor muscles.
Membranes of the larynx
           The elastic membrane is the fibrous framework of the larynx it lies beneath the laryngeal mucosa and is divided into upper & lower parts by the ventricle of the larynx. Ventricular ligament is a thickening of the free edge.  The vocal ligament is the -free upper edge of this elastic membrane.
Cavity of the larynx
It is divided into three parts by two folds of the mucous membrane:
1.False vocal cords:
                   These are the ventricular bands which are formed by the mucous membrane covering the ventricular ligament.
2. True vocal cords:
These lies at a lower level than false vocal cords, the epithelium is closely bound down to the underlying vocal ligament & their blood supply is poor hence the white appearance of the vocal cords in life.
    These mucosal folds divide the cavity into:
A. The vestibule: lies between the inlet of the larynx & the edges of the false cords.
       B. Ventricle of the larynx:  a recess between the false and the true vocal cords.
C. Subglottic space: lies between the true vocal cords and the lower border of the cricoid cartilage.
* Saccule: is a conical pouch which ascends from the anterior part of the ventricle.
* The glottis (rima glottides) is the interval between:
1.   The true vocal cords in its anterior 3/5.
2.  The vocal processes of the arytenoid cartilages in its posterior 2/5.
           Its average length in the adult male is about 2.5 cm while in the adult female is about 1.6 cm.
* The lining mucous membrane of the larynx is ciliated columnar epithelium except at:
1. The true vocal cords.
2. The upper part of the vestibule of larynx.  These are lined by stratified squamous epithelium.
Blood supply of the larynx
1. Laryngeal branches of the superior thyroid artery. 
2. Laryngeal Branches of the inferior thyroid artery.
Nerve Supply of the larynx
  The larynx is supplied   by branches of the vagus nerves:
1.  Superior laryngeal nerve which has two branches:
-   Internal branch: entirely sensory, it supplies the cavity of the larynx as far down as the level of the vocal cord.
-   External branch: entirely motor, it supplies the cricothyroid muscle.
2. Recurrent laryngeal nerve:
It has a much longer course on the left side than on the right. On the left side it turns round the arch of the aorta, while on the right side it turns round the subclavian artery, both of them runs upward on both sides between the trachea and esophagus, as they approach the larynx they supply all the muscles of the larynx except the cricothyroid muscle, also they give sensation to the cavity of the larynx below the level of the vocal cords.
Lymphatic drainage of the larynx
           The edges of the vocal cords divide the lymphatic system of the larynx into two parts:
L Supraglottic above the vocal cords: the vessels drain into:
- Preglottic nodes.
- Upper deep cervical nodes.
2. Subglottic below the vocal cords: the vessels drain into:
- Prelaryngeal and pretracheal nodes.
- Lower deep cervical nodes.
3. The vocal cords themselves have no lymphatic vessels.
Functions of the larynx
1. Protection of air passages.
2.  Phonation.
3. Aspiration.
4. Fixation of the chest.
**********************************************************************