Functions of Larynx

1. Air passage
2. Phonation
3. Protective sphincter
4. Deglutition

One speaks during the expiratory phase of respiration.

• Larynx lies in the anterior midline of the neck.
• It extends from the root of the tongue to the trachea.
• In the adult male → lies in front of C3–C6 vertebrae.
• In children and adult females → lies at a little higher level, at C1–C4 level.

• At puberty, the male larynx grows rapidly and becomes larger.
• This is seen as the prominent angle of thyroid cartilage → Adam’s apple.
• This makes the male voice:

• Louder
• Low pitched

• Pubertal growth of the female larynx is negligible.
• Female voice → high pitched.

Internal Diameter

• Larynx is made up of a skeletal framework of cartilages.
• Cartilages are connected by:

• Joints
• Ligaments
• Membranes

• Cartilages are moved by a number of muscles.
• Cavity of larynx is lined by mucous membrane.

Larynx contains 9 cartilages:

• 3 unpaired
• 3 paired

A. Unpaired Cartilages

B. Paired Cartilages

1. General Features

• V-shaped in cross-section.
• Consists of:

• Right lamina
• Left lamina

• Each lamina is roughly quadrilateral.
• The laminae are placed obliquely relative to the midline.
• Posterior borders → far apart.
• Anterior borders → approach each other:

2. Laryngeal Prominence / Adam’s Apple

• Lower parts of the anterior borders of right and left laminae fuse.
• They form a median projection called:

• Laryngeal prominence
• Adam’s apple

Upper parts of anterior borders are separated by the thyroid notch.

3. Cornua / Horns

• Posterior borders are free.
• They are prolonged upwards and downwards as:

• Superior cornua
• Inferior cornua

• Inferior cornua articulates with the cricoid cartilage.
• This forms the cricothyroid joint.

4. Oblique Line

Outer surface of each lamina is marked by an oblique line.

5. Attachments

Oblique line on outer surface gives attachment to:

1. Thyrohyoid
2. Sternothyroid
3. Thyropharyngeus part of inferior constrictor of pharynx.

Lower Border and Inferior Cornua

Give insertion to the triangular cricothyroid.

Posterior Border

Along the posterior border connecting superior and inferior cornua, insertion is given to:

1. Palatopharyngeus
2. Salpingopharyngeus
3. Stylopharyngeus

Inner Aspect

Attachments include:

1. Thyroepiglottic ligament
2. Thyroepiglottic muscle on each side
3. Vestibular ligament/fold on each side
4. Vocal ligament/fold on each side
5. Thyroarytenoid muscle
6. Vocalis muscle on each side

Superior Cornua

• Connected with the greater cornua of hyoid bone by the lateral thyrohyoid ligament.
• Thyrohyoid ligament contains 2 nodules of elastic cartilage, called cartilage triticea.
• These may strengthen this connection.

Inferior Cornua

In the median plane, inferior cornua is connected to the cricoid cartilage by the conus elasticus.

1. General Features

• Cricoid cartilage is ring-shaped.
• The ring has:

• Narrow anterior part → arch
• Broad posterior part → lamina

• Lamina projects upwards behind the thyroid cartilage.
• It articulates superiorly with the arytenoid cartilages.
• Inferior cornua of thyroid cartilage articulates with the side of cricoid cartilage at the junction of:

• Arch
• Lamina

2. Attachments

Anterior Part of Arch

• Gives origin to triangular cricothyroid muscle.
• Cricothyroid is a tensor of vocal cord.

Anterolateral Aspect of Arch

• Gives origin to lateral cricoarytenoid muscle.
• Lateral cricoarytenoid is an adductor of vocal cord.

Lamina

• Its outer aspects give origin to the posterior cricoarytenoid muscle.
• Posterior cricoarytenoid is a very important “safety muscle”.
• Cricothyroid and quadrate membranes are also attached.

1. General Features

• Leaf-shaped cartilage.
• Placed in the anterior wall of the upper part of larynx.

Upper End

• Broad
• Free
• Projects upwards behind the hyoid bone and tongue.

Lower End

• Pointed
• Attached to the upper part of the angle between the two laminae of thyroid cartilage by the thyroepiglottic ligament.

2. Attachments

Margins

Right and left margins provide attachment to the aryepiglottic folds.

Anterior Surface

Connected:

1. To tongue → by median glossoepiglottic fold
2. To hyoid bone → by hyoepiglottic ligament

Posterior Surface

• Covered with mucous membrane.
• Presents a tubercle in the lower part.

Muscles

1. Thyroepiglottic Muscle

• Attached between thyroid cartilage and margins of epiglottis.
• Keeps the inlet of larynx patent for breathing.

2. Aryepiglottic Muscle

• Closes the inlet during swallowing.

1. General Features

• Two small pyramid-shaped cartilages.
• Lie on the upper border of the lamina of cricoid cartilage.
• Apex is:

• Curved
• Directed posteromedially

Apex articulates with the corniculate cartilage.

2. Base

• Base is concave.
• Articulates with the lateral part of the upper border of cricoid lamina.
• Base is prolonged:

• Anteriorly → vocal process
• Laterally → muscular process

3. Surfaces

The cartilage has:

1. Anterolateral surface
2. Medial surface
3. Posterior surface

4. Attachments

Vocal Process

• Vocal fold
• Vocalis muscle

Above Vocal Process

• Vestibular fold

Muscular Process

• Posterior aspect → insertion of posterior cricoarytenoid
• Anterior aspect → insertion of lateral cricoarytenoid

Posterior Surface

Transverse arytenoid passes across the two cartilages.

Between Base and Apex

• Oblique arytenoid is present.
• It continues as aryepiglottic muscle into the two sides of the epiglottis.

Quadrangular / Quadrate Membrane

Attached between:

• Arytenoid
• Epiglottis
• Thyroid cartilages

Corniculate / Santorini Cartilages

• Two small conical nodules.
• Articulate with the apex of arytenoid cartilages.
• Directed posteromedially.
• Lie in the posterior parts of the aryepiglottic folds.

Cuneiform / Wrisberg Cartilages

• Two small rod-shaped pieces of cartilage.
• Placed in the aryepiglottic folds.
• Located just ventral to the corniculate cartilages.

Hyaline Cartilage

The following are made up of hyaline cartilage:

1. Thyroid cartilage
2. Cricoid cartilage
3. Basal parts of arytenoid cartilages

They may ossify after the age of 25 years.

Elastic Cartilage

The following are made up of elastic cartilage:

1. Epiglottis
2. Corniculate cartilages
3. Cuneiform cartilages
4. Processes of arytenoid cartilages

They do not ossify.

1. Laryngitis

2. Laryngeal Oedema

• May occur due to a variety of causes.
• It can obstruct breathing.
• Inflammation of the upper larynx may cause oedema of the supraglottis.
• It does not extend below the vocal cords because the mucosa is adherent to the vocal ligament.

3. Singer’s / Teacher’s Nodules

• Misuse of the vocal cords may produce nodules on the vocal cords.
• They occur mostly at the junction of:

• Anterior 1/3
• Posterior 2/3

These are called:

• Singer’s nodules
• Teacher’s nodules

4. Fibreoptic Flexible Laryngoscopy

• Performed under local anaesthesia.
• A flexible laryngoscope is passed.
• Larynx is well visualised.

5. Microlaryngoscopy

• Performed under an operating microscope.
• Vocal cord tumours and diseases are excised by this method.

6. Foreign Body in Larynx

• Larynx or glottis is the narrowest part of the respiratory passages.
• Therefore, foreign bodies are usually lodged here.
• Large foreign bodies may block the laryngeal inlet, leading to suffocation.
• Fish bones may sometimes become impacted in:

• Vallecula
• Piriform fossa

• Often these bones only scratch the mucosa on their way down.
• The person then gets a foreign body sensation due to a dull visceral pain caused by the scratch.

7. Piriform Fossa

• Lies between:

• Quadrate membrane
• Medial side of thyroid cartilage

• It is traversed by the internal laryngeal nerve.
• The source states that the piriform fossa is used to smuggle out precious stones, diamonds, etc.
• Therefore, it is called “smuggler’s fossa.”

8. Referred Pain in Ear

• Mucous membrane of the larynx is supplied by X nerve through:

• Superior laryngeal nerve
• Recurrent laryngeal nerve

• Therefore, laryngeal tumours may also cause referred pain in the ear.
• The ear is partly supplied by the auricular branch of X nerve.

The muscles of the larynx are grouped into:

1. Extrinsic muscles
2. Intrinsic muscles

Extrinsic Muscles

• These are paired muscles.
• They move the larynx as a whole.
• They are attached to one of the laryngeal cartilages and adjacent bones.

Muscles

1. Palatopharyngeus
2. Salpingopharyngeus
3. Stylopharyngeus
4. Thyrohyoid
5. Sternothyroid

Intrinsic Muscles

• These muscles extend between laryngeal cartilages.

Muscles

1. Cricothyroid
2. Posterior cricoarytenoid
3. Lateral cricoarytenoid
4. Transverse arytenoid
5. Oblique arytenoid
6. Aryepiglotticus
7. Thyroarytenoid
8. Thyroepiglotticus
9. Vocalis

Functions of Intrinsic Muscles

They:

1. Open or close the laryngeal inlet.
2. Adduct or abduct the vocal cords.
3. Lengthen or shorten the vocal cords.
4. Increase or decrease the tension in vocal cords.

The vocal and muscular processes move in opposite directions.

Abduction of Vocal Cords

• Any muscle that pulls the muscular process medially pushes the vocal process laterally.
• This results in abduction of vocal cords.
• This is done by only one pair of muscles:

• Posterior cricoarytenoids

Adduction of Vocal Cords

• Muscles that pull the muscular process forward and laterally push the vocal process medially.
• This causes adduction of vocal cords.
• This is done by:

1. Lateral cricoarytenoid
2. Transverse arytenoid

Cricothyroid

• Causes a rocking movement of thyroid forwards and downwards at the cricothyroid joints.
• This results in tensing and lengthening of the vocal cords.

Muscle Abducting Vocal Cords

Movements of Vocal Folds

Movements of the vocal folds affect the shape and size of the rima glottidis.

During Quiet Breathing / Rest

• The intermembranous part of the rima is triangular.
• The intercartilaginous part is quadrangular.

1. Cricothyroid

2. Posterior Cricoarytenoid

3. Lateral Cricoarytenoid

4. Transverse Arytenoid

5. Oblique Arytenoid and Aryepiglottic

6. Thyroarytenoid and Thyroepiglotticus

7. Vocalis