Anatomy of larynx

1. LARYNX
Roll no. 20073

2. ANATOMY
•The larynx lies in front of the hypopharynx
opposite the third to sixth cervical vertebrae.
•It moves vertically and in anteroposterior
direction during swallowing and phonation.
• It can also be passively moved from side to
side producing a characteristic grating
sensation called laryngeal crepitus.
•In an adult, the larynx ends at the lower
border of C 6 vertebra.

3. INFANTS LARYNX
• positioned high in the neck level of glottis being opposite to C3 or C4 at rest
and reaches C1 or C2 during swallowing.
• This high position allows the epiglottis to meet soft palate and make a
nasopharyngeal channel for nasal breathing during suckling. The milk feed
passes separately over the dorsum of tongue and the sides of epiglottis, thus
allowing breathing and feeding to go on simultaneously.
• Thyroid cartilage in an infant is flat. It also overlaps the cricoid cartilage and is in
turn overlapped by the hyoid bone. Thus cricothyroid and thyrohyoid spaces are
narrow and not easily discernible as landmarks when performing tracheostomy.

4. LARYNGEAL CARTILAGES
Larynx has three unpaired and three paired cartilages.
Unpaired:
• Thyroid,
• cricoid
• epiglottis.
Paired:
•
•
•
Arytenoid,
corniculate
cuneiform.

5. 1. Thyroid
• It is the largest of all. It’s two alae meet anteriorly forming an angle of 90° in
males and 120° in females. Vocal cords are attached to the middle of
thyroid angle.
• Most of laryngeal foreign bodies are arrested above the vocal cords, i.e.
above the middle of thyroid cartilage and an effective airway can be
provided by piercing the cricothyroid membrane- a procedure called
cricothyrotomy.
2. Cricoid. It is the only cartilage forming a complete ring. Its posterior part is
expanded to form a lamina while anteriorly it is narrow forming an arch.

6. 3. Epiglottis
• It is a leaf-like, yellow, elastic cartilage forming anterior wall of laryngeal inlet. It
is attached to the body of hyoid bone by hyoepiglottic ligament, which divides it
into suprahyoid and infrahyoid epiglottis.
• A stalk-like process of epiglottis (petiole) attaches the epiglottis to the thyroid
angle just above the attachment of vocal cords.
• Anterior surface of epiglottis is separated from thyrohyoid membrane and
upper part of thyroid cartilage by a potential space filled with fatthe pre-
epiglottic space
• Posterior surface of epiglottis is concavoconvex-concave above but convex
below forming a bulge called tubercle of epiglottis, which obstructs view of
anterior commissure when examining larynx by indirect laryngoscopy

7. 4. Arytenoid cartilages.
They are paired. Each arytenoid cartilage is pyramidal in shape. It has a base which
articulates with cricoid cartilage; a muscular process directed laterally to give
attachment to intrinsic laryngeal muscles; a vocal process directed anteriorly, giving
attachment to vocal cord; and an apex which supports the corniculate cartilage.
5. Corniculate cartilages (of Santorini) (Corn = horn)
• They are paired.
• Each articulates with the apex of arytenoid cartilage as if forming its horn.
6. Cuneiform cartilages (of Wrisberg).
They are rod shaped. Each is situated in aryepiglottic fold in front of corniculate
cartilage and provides passive supports to the fold.

8. LARYNGEAL JOINTS
1. Cricoarytenoid joint
It is a synovial joint surrounded by capsular ligament. It is formed
between the base of arytenoid and a facet on the upper border of cricoid
lamina. Two types of movements occur in this joint:
(i)rotatory, in which arytenoid cartilage moves around a vertical axis,
thus abducting or adducting the vocal cord;
(ii)gliding movement, in which one arytenoid glides towards the other
cartilage or away from it, thus closing or opening the posterior part of
glottis.

9. 2. cricothyroid joint.
• It is also a synovial joint.
• Each is formed by the inferior cornua of thyroid cartilage with a facet on the
cricoid cartilage.
• Cricoid cartilage rotates at these joints on a transverse axis which passes
transversely through these joints.

10. LARYNGEAL MEMBRANES
membrane and ligaments of larynx
• The term extrinsic is used when membrane or ligament attaches to the
structures outside the larynx, i.e. to the hyoid bone or trachea. The term intrinsic
is used for membranes joining within the larynx but not extending to hyoid bone
or trachea.
1. Extrinsic membranes and ligaments
• (a) Thyrohyoid membrane : It connects thyroid cartilage to hyoid bone. It
is pierced by superior laryngeal vessels and internal laryngeal nerve.
• (b) Cricotracheal membrane : It connects cricoid cartilage to the first
tracheal ring.
• (c) Hyoepiglottic ligament :It attaches epiglottis to hyoid bone

11. 2. Intrinsic membranes and ligaments
(a) Cricovocal membrane :
• It is a triangular fibroelastic membrane. Its
upper border is free and stretches between
middle of thyroid angle to the vocal process of
arytenoid and forms the vocal ligament.
• Its lower border attaches to the arch of cricoid
cartilage. From its lower attachment the
membrane proceeds upwards and medially
and thus, with its fellow on the opposite side,
forms conus elasticus (Figure 56.3) where
subglottic foreign bodies sometimes get
impacted.

12. B.Quadrangular membrane.
It lies deep to mucosa of a yepiglottic folds and is not well-defined. It stretches
between the epiglottic and arytenoid cartilages. Its lower border forms the
vestibular ligament which lies in the false cord
C.Cricothyroid ligament.
The anterior part of c roid membrane is thickened to form the ligament and its
lateral part forms the cricovocal membrane.
D).Thyroepiglottic ligament.
It attaches epiglottis to thyroid cartilage.

13. MUSCLES OF LARYNX
• They are of two types:
• intrinsic, which attach laryngeal cartilages to each other and extrinsic, which
attach larynx to the surrounding structures.
• 1. Intrinsic muscles. They may act on vocal cords or laryngeal inlet.
• (a) ACTING ON VOCAL CORDS
•

14. (b) Acting on laryngeal inlet

15. Extrinsic muscles.
They connect the larynx to the neighbouring structures and are divided into elevators or depressors of larynx.
• (a) Elevators : Primary elevators act directly as they are attached to the
cartilage and include stylopharyngeus, salpingopharyngeus,
palatopharyngeus and thyrohyoid.
• Secondary elevators act indirectly as they are attached to the hyoid bone and
include mylohyoid (main), digastric, stylohyoid and geniohyoid.
• (b) Depressors. They include sternohyoid, sternothyroid and omohyoid.

16. CAVITY OF THE LARYNX
Laryngeal cavity starts at the laryngeal inlet where it communicates with the pharynx and ends at the lower border of
cricoid cartilage where it is continuous with the lumen of trachea. Two pairs of folds, vestibular and vocal, divide the
cavity into three parts, namely the vestibule, the ventricle and the subglottic space.
• 1.Inlet of larynx. It is an oblique opening bounded anteriorly by free margin
of epiglottis; on the sides, by aryepiglottic folds and posteriorly by
interarytenoid fold.
• 2.Vestibule. It extends from laryngeal inlet to vestibular folds. Its anterior
wall is formed by posterior surface of epiglottis; sides by the aryepiglottic
folds and posterior wall by mucous membrane over the anterior surface of
arytenoids.

17. • 3. Ventricle (sinus of larynx). It is a deep elliptical space between vestibular
and vocal folds, also extending a short distance above and lateral to
vestibular fold.
• The saccule is a diverticulum of mucous membrane which starts from the
anterior part of ventricular cavity and extends upwards between vestibular
folds and lamina of thyroid cartilage.
• When abnormally enlarged and distended, it may form a laryngocele—an air
containing sac which may present in the neck.
• There are many mucous glands in the saccule, which help to lubricate the
vocal cords.

18. • 3. Subglottic space (infraglottic larynx). It extends from vocal cords to
lower border of cricoid cartilage.
• Vestibular Folds (False Vocal cords). Two in number; each is a fold of
mucous membrane extending anteroposteriorly across the laryngeal cavity. It
contains vestibular ligament, a few fibres of thyroarytenoideus muscle and
mucous glands.
• Vocal Folds (true Vocal cords). They are two pearly white sharp bands
extending from the middle of thyroid angle to the vocal processes of
arytenoids. Each vocal cord consists of a vocal ligament which is the true
upper edge of cricovocal membrane covered by closely bound mucous
membrane with scanty subepithelial connective tissue.

19. • 4. glottis (rima glottidis)
• It is the elongated space between vocal cords
anteriorly, and vocal processes and base of arytenoids
posteriorly (Figure 56.7).
• Anteroposteriorly, glottis is about 24 mm in men and
16 mm in women. It is the narrowest part of laryngeal
cavity.
• Anterior two-thirds of glottis are formed by
membranous cords while posterior one-third by vocal
processes of arytenoids.
• Size and shape of glottis varies with the movements
of vocal cords.
• Anterior two-thirds of glottis is also called phonatory
glottis as it is concerned with phonation but posterior
one-third called respiratory glottis.

20. MUCOUS MEMBRANE OF THELARYNX
• It lines the larynx and is loosely attached except over the posterior surface of
epiglottis, true vocal cords and corniculate and cuneiform cartilages.
• Epithelium of the mucous membrane is ciliated columnar type except over the
vocal cords and upper part of the vestibule where it is stratified squamous type.
• Mucous glands are distributed all over the mucous lining and are particularly
numerous on the posterior surface of epiglottis, posterior part of the aryepiglottic
folds and in the saccules. There are no mucous glands in the vocal folds.

21. Structure of the VocalCords
Stratified squamous epithelium lines the vocal cord. It overlies lamina propria which consists of three layers:
• (a) superficial layer (or Reinke’s space),
• b) intermediate layer and
• c) deep layer.
• Intermediate and deep layers together form the vocal ligament
•

22. Spaces of the Larynx
• 1. pre-epiglottic space of BOYER
• It is bounded by upper part of thyroid cartilage and thyrohyoid membrane in front,
hyoepiglottic ligament above and infrahyoid epiglottis and quadrangular membrane
behind.
• Laterally, it is continuous with paraglottic space. It is filled with fat, areolar tissue
and some lymphatics.
•

23. • 2. Paraglottic space.
• It is bounded by the thyroid c tilage laterally, conus elasticus inferomedially,
the ventricle and quadrangular membrane medially, and mucosa of
pyriform fossa posteriorly (Figures 56.8) It is continuous with pre-epiglottic
space. Growths which invade this space can present in the neck through
cricothyroid space.

24. • 3. reinke’s space.
• Under the epithelium of vocal cords is a potential space with scanty
subepithelial connective tissues.
• It is bounded above and below by the arcuate lines, in front by anterior
commissure, and behind by vocal process of arytenoid.
• Oedema of this space causes fusiform swelling of the membranous cords
(Reinke’s oedema).

25. LYMPHATIC DRAINAGE
• Supraglottic larynx above the vocal cords is drained by lymphatics, which
pierce the thyrohyoid membrane and go to upper deep cervical nodes.
• Infraglottic larynx below the vocal cords is drained by lymphatics which pierce
cricothyroid membrane and go to prelaryngeal and pretracheal nodes and
hence to lower deep cervical and mediastinal nodes.
• There are practically no lymphatics in vocal cords, hence carcinoma of this
site rarely shows lymphatic metastases.

26. PHYSIOLOGY OF LARYNX
• The larynx performs the following important functions:
• 1. Protection of lower airways
• 2. Phonation
• 3. Respiration
• 4. Fixation of the chest.
•

27. NERVE SUPPLY OF LARYNX
• Motor. All the muscles which move the vocal cord (abductors, adductors or
tensors) are supplied by the recurrent laryngeal nerve except the cricothyroid
muscle. The latter receives its innervation from the external laryngeal nerve—a
branch of superior laryngeal nerve.
• Sensory. Above the vocal cords, larynx is supplied by internal laryngeal nerve
—a branch of superior laryngeal, and below the vocal cords by recurrent
laryngeal nerve.

28. • Recurrent laryngeal nerve
• Right recurrent laryngeal nerve arises from the vagus at the level of
subclavian artery, hooks around it, and then ascends between the trachea
and oesophagus.
• The left recurrent laryngeal nerve arises from the vagus in the mediastinum
at the level of arch of aorta, loops around it, and then ascends into the neck
in the tracheo-oesophageal groove.
• Thus, left recurrent laryngeal nerve has a much longer course which makes
it more prone to paralysis compared to the right

29. Superior laryngeal nerve
• It arises from inferior ganglion of the vagus,
descends behind internal carotid artery
and, at the level of greater cornua of hyoid
bone, divides into external and internal
branches.
• The external branch supplies cricothyroid
muscle while the internal branch pierces
the thyrohyoid membrane and supplies
sensory innervation to the larynx and
hypopharynx