Larynx

Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai

LARYNX

Hi..Friends….I have kept diagrams drawn with pen and some simple sketch diagrams for movements of vocal cords which can be used for exam. Other photos are for understanding the topic.

Introduction: Larynx is the part of respiratory passage located in the neck and also an organ of phonation.

Situation and Extent: In the anterior part of the neck in midline in front of 3rd to 6th cervical vertebra (in adult male) extending from the root of tongue to the trachea.

Size: 44 mm in Male and 36 mm in female (Adult)

Larynx is formed by Cartilages, Membranes and Muscles. Cavity of larynx continues as trachea.


CARTILAGES OF LARYNX: (Short Note)

Skeleton of larynx is formed by 9 cartilages.

Cartilages of Larynx are:

3 Unpaired Cartilages:

1. Thyroid cartilage

2. Cricoid cartilage

3. Epiglottis

3 paired cartilages:

1. Arytenoid cartilages

2. Corniculate cartilages

3. Cuneiform cartilages


1. Thyroid Cartilage:

Type: Hyaline cartilage

It is midline cartilage formed by two laminae fused in the midline anteriorly but separated posteriorly.

The fusion of two laminae in the male is acute at the angle of 90 degrees. Hence the anterior part of cartilage is prominently seen in front of the neck in male known as Laryngeal Prominence (Adam’s Apple). In the female the fusion is obtuse at the angle of 120 degrees and hence the prominence is not well seen.

Lamina of thyroid cartilage has oblique line giving attachment to sternothyroid, thyrohyoid and inferior constrictor of pharynx muscles.

Posterior free borders of the thyroid laminae are projecting upwards and downwards to be known as superior and inferior cornu of thyroid cartilage.

Upper border of Thyroid cartilage gives attachment to Thyrohyoid membrane and lower border gives attachment to Cricothyroid membrane.

This cartilage can ossify in old age and can be seen in x-ray.


2. Cricoid Cartilage:

Type: Hyaline cartilage

It is signet ring shape cartilage.

It forms complete ring in the larynx.

Anterior narrow part of the cricoid cartilage is known as ARCH and posterior wider part of the cartilage is known as LAMINA.

Arch gives attachment to cricothyroid and lateral cricoarytenoid muscles and inferior constrictor of pharynx muscles.

Lamina gives attachment to Posterior cricoarytenoid muscle.

Lamina articulates with Base of the arytenoids cartilages.

Upper border of crioid cartilage gives attachment to cricothyroid membrane and lower border gives attachment to cricotracheal membrane.

3. Epiglottis

Type: Elastic cartilage

It is leaf shape cartilage.

Its narrow lower part is attached to thyroid cartilage at epiglottic tubercle.

Its wider upper part is having free border and with aryepiglottic fold forms the inlet of larynx.


4. Arytenoid Cartilages:

Paired cartilages

Type: Base of the cartilage is Hyaline cartilage and Apex of the cartilage is Elastic cartilage.

It is Pyramidal shape cartilage.

Its base articulates with lamina of cricoids cartilage. Base contains two processes. One process is facing anteriorly and gives attachment to vocal cord known as Vocal process and another process is facing laterally and gives attachment to muscles known as Muscular process.

Apex is pointing upwards.


5. Corniculate cartilages:

Paired cartilages


It is small rod shape cartilages.

Present in the aryepiglottic fold.

6. Corniculate cartilages:

Paired cartilages


It is small wedge shape cartilages.

Present in the aryepiglottic fold.


Anterior View of Larynx Posterior View of Larynx

MEMBRANES OF LARYNX:

Membranous skeleton of larynx is formed by following membranes.

Membranes of Larynx are:

1. Quadrate Membrane

2. Cricovocal Membrane (Conus Elasticus)

3. Thyrohyoid Membrane

4. Cricothyroid Membrane

5. Cricotracheal Membrane


1. Quadrate Membrane:

It is quladrilateral membrane inner to thyroid cartilage.

Superior attachment: Margin of epiglottis and aryepiglottic fold.

Inferiorly the membrane has free margin which is thickened to form the VESTIBULAR FOLDS.

2. Cricovocal Membrane (Conus Elasticus):

It is triangular membrane.

Superiorly the membrane has free margin which is thickened to form the VOCAL FOLDS.

Inferior attachment: Margin of upper border of arch of cricoid cartilage.


3. Thyrohyoid Membrane:

This membrane is between the thyroid cartilage and hyoid bone.

It is pierced by Internal laryngeal nerve and superior laryngeal vessels.

4. Cricothyroid Membrane:

This membrane is between cricoid cartilage and thyroid cartilage.

5. Cricotracheal Membrane:

This membrane is between cricoid cartilage and first tracheal ring.

CAVITY OF LARYNX: (INTERIOR OF LARYNX) - (Dissection viva)

INLET OF LARYNX:

It is entry point to the larynx.

It is bounded by:

Anteriorly upper border of epiglottis

On Each side: Aryepiglottic fold

Posteriorly: Interarytenoid fold

INTERIOR OF LARYNX SHOW FOLLOWING FEATURES:

1. Tubercle of Epiglottis: the rot of epiglottis is slightly elevated.

2. Vestibular folds: These are upper folds in the cavity of larynx. They are formed by lower thickened free margin of the quadrate membrane. The ‘V” shape gap between two vestibular folds is known as RIMA VESTIBULI. They are also known as false folds and appear pink in colour in living.

3. Vocal folds: These are lower folds in the cavity of larynx. They are formed by upper thickened free margin of the Conus elasticus. The ‘V” shape gap between two vocal folds is known as RIMA GLOTIDIS. They are also known as True folds and appear early white in colour in living as they are covered by stratified squamous epithelium.

4. Supraglottic Larynx: It is the part of larynx above the vocal folds. It is divided into two parts by vetibular folds.

Vestibule: It is the part of larynx above the vestibular folds.

Ventricle (Sinus): It is the part of larynx between the vestibular and vocal folds. Small pocket from the sinus is known as saccule which contains the glands which keeps the vocal folds wet.


5. Infraglottic larynx: It is the part of larynx below the vocal folds which continues as trachea at the lower border of cricoids cartilage.

INTEROR OF LARYNX (CORONAL SECTION) INTEROR OF LARYNX (SAGITTAL SECTION)

Supraglottic Larynx

Vestibular fold

Vocal fold Ventricle

Infraglottic larynx


MUSCLES OF LARYNX:

1. Cricothyroid: (Short Note)

This is triangular shape muscle. This is the only muscle located on outer aspect of larynx.

Origin: Outer surface of the arch of cricoids cartilage.

Insertion: Inferior cornu of thyroid cartilage.

Nerve supply: External Laryngeal Nerve.

Action: Tenses the vocal cords by either tilting the cricoids cartilage or pulling the thyroid cartilage forwards.

CRICOTHYROID ACTION OF CRICOTHYROID

Applied Anatomy: Damage to external laryngeal nerve during ligation of superior thyroid artery in thyroidectomy leads to paralysis of this muscle causing hoarseness of voice.


2. Lateral Cricoarytenoid:

This is triangular shape muscle.

Origin: Cricoid cartilage.

Insertion: Muscular process of arytenoid cartilage.

Action: Adduction of vocal cords.

3. Posterior Cricoarytenoid:

Origin: Lamina of Cricoids cartilage.

Insertion: Muscular process of arytenoid cartilage.

Action: Abduction of vocal cords.

4. Transverse arytenoid:

Transversely placed muscle between two arytenoids cartilages.

Action: Adduction of vocal cords.


5. Oblique arytenoids and Aryepigloticus:

Oblique arytenoids pass from base of one arytenoids cartilage to apex of another arytenoids cartilage.

Continuation of the same muscle in the aryepiglotic fold is known as aryepigloticus.

Action: Closure of inlet of larynx by purse string action.

6. Thyroarytenoid (Vocalis):

Origin: Inner aspect of thyroid cartilage.

Insertion: vocal process of arytenoid cartilage.

Action: relaxes the vocal cords.

7. Thyroepigloticus:

Origin: Inner aspect of thyroid cartilage.

Insertion: free margin of the epiglottis.

Action: Opens the inlet of larynx.

MOTOR NERVE SUPPLY OF LARYNX: All the muscles of larynx are supplied by Recurrent Laryngeal Nerve except Cricothyroid which is supplied by External Laryngeal Nerve.

ACTIONS OF THE MUSCLES OF LARYNX: (Short note)

MOVEMENTS OF VOCAL CORDS: (Short note)

1. Abduction of vocal cords: Posterior cricoarytenoid

2. Adduction of vocal cords: Lateral cricoarytenoids and transverse arytenoids.


3. Tensor of vocal cord: Cricothyroid.

4. Relaxor of vocal cord: Thyroarytenoid (Vocalis).

RIMA GLOTIDIS:

It is slit like “V” shape gap between vocal cords.

It is divided in to:

Anterior triangular inter-membranous part.

Posterior quadrangular inter-cartilaginous part.

During Normal breathing: it is triangular anteriorly and quadrangular posteriorly.

During forced breathing: it is triangular both anteriorly as well as posterioly i.e. Lozenge shape.

Inter-membranous part

Inter-cartilaginous part


During normal speech: it is narrowed down to s very small gap like a chink.

During whispering: anterior part closes but posterior part is triangular.

CLOSURE OF INLET OF LARYNX:

1. Oblique arytenoids and aryepigloticus.

OPENING OF INLET OF LARYNX:

1. Thyroepigloticus.

Nerve supply of Larynx:

Motor nerve supply: All the muscles of larynx are supplied by Recurrent Laryngeal Nerve except Cricothyroid which is supplied by External Laryngeal Nerve.

Sensory nerve supply:

Above the vocal cords: Internal Laryngeal Nerve.

Below the vocal cords: Recurrent Laryngeal Nerve.

Arterial supply:

Above the vocal cords: Superior laryngeal artery –Branch of superior thyroid artery.

Below the vocal cords: Inferior laryngeal artery –Branch of Inferior thyroid artery.


Venous drainage:

Above the vocal cords: Superior laryngeal vein –drains in to superior thyroid vein.

Below the vocal cords: Inferior laryngeal vein –drains in to Inferior thyroid vein.

Lymphatic Drainage:

Above the vocal cords: Anterosuperior group of deep cervical lymph nodes.

Below the vocal cords: Posteroinferior group of deep cervical lymph nodes.

APPLIED ANATOMY:

1. Laryngoscopy: Technique for visualization of larynx.

Direct Laryngoscopy by instrument laryngoscope.

Indirect Laryngoscopy by mirror in the pharynx.

Structures seen are Epiglottis, vestibular folds, vocal folds, tracheal rings.


2. Laryngeal spasm: It is sudden muscular spasm of muscles of larynx following foreign body in the larynx, anaphylactic reaction or aspiration of fluids in larynx. It is serious condition and air needs to be established by Tracheostomy.

3. Damage to external laryngeal nerve during superior thyroid artery ligation leads to paralysis of cricothyroid leading to hoarseness of voice.

4. Unilateral (one sided) damage to recurrent laryngeal nerve damage is compensated by overaction of opposite side muscles of larynx.

5. Bilateral (both side) damage to recurrent laryngeal nerve damage leads to no movements of vocal cords leading to hoarseness of voice and difficulty in breathing.

6. Singer’s (Teacher’s ) Nodule: It is nodule on vocal cords in singers or teachers where there is constant strain on vocal cords.

7. Carcinoma of larynx: Commonly seen in the smokers where larynx with associated structures is removed.

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Larynx