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Term Paper on Larynx

Term Paper Contents:

  1. Term Paper on the Anatomical Structure of Larynx
  2. Term Paper on the Functions and Applied Anatomy of Larynx
  3. Term Paper on the Cartilages of Larynx
  4. Term Paper on the Muscles of Larynx
  5. Term Paper on the Membranes and Ligaments of Larynx
  6. Term Paper on the Blood Supply and Nerve Supply of Larynx

Term Paper # 1. Anatomical Structure of Larynx:

ADVERTISEMENTS:

It is the chamber concerned with respiration and phonation.

Constitution:

It is formed by:

1. Cartilages

ADVERTISEMENTS:

2. Muscles

3. Membranes.

Average Dimensions:

Situation:

ADVERTISEMENTS:

Anterior part of the neck at the level of 3rd, 4th, 5th and 6th cervical vertebrae.

Superiorly it opens into laryngo pharynx.

Inferiorly it is continuous with the trachea.

ADVERTISEMENTS:

Term Paper # 2. Functions and Applied Anatomy of Larynx:

1. Closure of Laryngeal Inlet:

During swallowing, cough reflex expels any foreign body-entering trachea.

2. Phonation:

ADVERTISEMENTS:

Exhaled air forces the adducted vocal cords apart and vibrates them – to produce voice. Pitch depends on number of vibration per second, changes in the length and tension of vocal cord.

Quality of Voice is due to resonators like nose, pharynx, oral cavity and para nasal air sinuses. Volume of voice is controlled by intensity of air pressure generated by the lung.

3. Respiratory function.

4. Fixation of Chest:

ADVERTISEMENTS:

During strenuous work, larynx closes and thoracic cage becomes fixed, which helps in the performance like climbing, straining for stools, parturition etc.

Applied Anatomy of Larynx:

1. Laryngitis.

2. Laryngeal diphtheria.

3. Congenital laryngeal web.

4. Singer’s nodes (vocal nodule) – develops due to misuse or overuse of voice.

5. Laryngocele is a bulbs air containing prolongation of the ventricle and saccule – it may herniate outside or inside of larynx.

6. Laryngoscopy – examination of larynx by laryngoscope.

Term Paper # 3. Cartilages of Larynx:

Paired and unpaired.

(a) Unpaired cartilages are:

(i) Thyroid cartilage.

(ii) Cricoid cartilage.

(iii) Epiglottis.

(b) Paired cartilages are:

(i) Arytenoid cartilage.

(ii) Corniculate cartilage.

(iii) Cuneiform cartilage.

(i) Thyroid Cartilage:

It is the largest cartilage of the larynx.

Histologically – It is hyaline cartilage.

Parts:

It has a pair of laminae.

Lamina has four borders:

i. Superior border.

ii. Inferior border.

iii. Anterior border.

iv. Posterior border.

Two laminae meet along the anterior border.

Upper part of line of fusion is “V” shaped and is called median thyroid notch.

Posterior border of lamina is continued superiorly as superior horn and inferiorly as inferior horn.

Superior border gives attachment to thyrohyoid membrane.

Each lamina has two surfaces – external and internal surfaces.

External surface has oblique line. It gives insertion to sternothyroid muscle and origin to thyrohyoid muscle.

Posterior end of oblique line gives origin to inferior constrictor of pharynx.

Near the lower border cricothyroid muscle is inserted.

Inner surface of laminae of thyroid cartilage bounds the larynx – in the midline epiglottis is attached.

Inner surface gives attachment to cricothyroid membrane – upper border of this membrane forms the vocal cord.

Laterally inner surface is related to Piriform fossa – in the floor of the fossa internal laryngeal nerve is situated.

(ii) Cricoid Cartilage:

It is a variety of hyaline cartilage.

It is the only cartilage of larynx that forms a complete ring (signet ring shaped).

Parts of the Cricoid Cartilage:

1. Narrow arch is present anteriorly.

2. Broad lamina is present posteriorly.

Upper border of lamina articulates with arytenoid cartilages.

Upper border of arch gives attachment for the cricothyroid membrane. The lower border of arch is connected to trachea by cricotracheal ligament.

Midline of the posterior surface of lamina gives attachment for the tendon of oesophagus. On either side of the midline, posterior surface of lamina gives origin for the posterior crico arytenoids muscle. Lateral aspect of lamina has a facet for articulation with the inferior horn of thyroid cartilage.

(iii) Epiglottis:

It is made up of elastic cartilage and is leaf shaped, broader above and narrows below.

Situated posterior to the tongue and connected anteriorly to it by a median and lateral glossoepiglottic folds.

It is connected to the hyoid bone by hyoepiglottic ligament.

Lower end is pointed and attached to angle between two laminae of thyroid cartilage by thyroepiglottic ligament.

Right and left margins give attachment to aryepiglottic folds.

Posterior surface is covered with mucous membrane and present a tubercle in the lower part.

(iv) Arytenoid Cartilage:

Arytenoid cartilage is pyramidal shaped, lying on the upper border of lamina of cricoid cartilage.

Parts:

1. Apex – Situated above.

2. Base – Situated below.

3. Vocal process – Directed forwards from the base, gives attachment to vocal ligament.

4. Muscular process – Projects laterally from the base and gives attachment to muscles of larynx.

Joint Formed:

Apex articulates with the corniculate cartilage.

Base articulates with cricoid cartilage and forms crico arytenoid joint – synovial variety.

Surfaces are antero lateral, medial and posterior.

(v) Corniculate Cartilages:

Corniculate cartilages are small pea shaped, paired cartilage.

Situated along the apex of arytenoids cartilage, found within the aryepiglottic fold.

Elastic in nature.

(vi) Cuneiform Cartilage:

Two small rods shaped pieces of cartilage placed in aryepiglottic folds.

Elastic in nature.

Term Paper # 4. Muscles of Larynx:

Classified into extrinsic and intrinsic muscles.

A. Extrinsic Muscles:

Moves the larynx up and down during swallowing.

(a) Muscles that elevate the larynx are:

(i) Stylohyoid

(ii) Digastric

(iii) Mylohyoid

(iv) Middle constrictor and thyropharyngeus part of inferior constrictor of pharynx.

(v) Thyrohyoid.

(b) Muscles that depress the larynx are:

(i) Sternothyroid

(ii) Sternohyoid

(iii) Omohyoid.

B. Intrinsic Muscles:

Intrinsic muscles are of two varieties:

1. Muscles of controlling the inlet of larynx.

2. Muscles controlling the vocal cord.

1. Muscles Acting on Inlet of Larynx:

(a) Oblique Arytenoid Muscle:

Origin:

From muscular process of arytenoid cartilage of one side.

Insertion:

Apex of opposite arytenoid cartilage.

(b) Ary Epiglottic Muscle:

Some fibres of obique arytenoids enter the aryepiglottic fold and form this muscle.

Action:

Contraction of both sides of muscles reduces the size of laryngeal inlet (closing).

Nerve Supply:

Recurrent laryngeal nerve.

(c) Thyro Epiglotticus:

Arises from thyroid angle, fibres run backwards and upwards for insertion into the aryepiglottic fold to reach the edge of epiglottis.

Action:

Opening of laryngeal inlet.

Nerve Supply:

Recurrent laryngeal nerve.

2. Muscles Controlling the Movement of Vocal Cords:

(a) Cricothyroid is tensor of vocal cords.

(b) Posterior cricoarytenoid is abductor of vocal cords.

(c) Transverse arytenoids.

(d) Thyro arytenoids.

(e) Lateral cricoarytenoids.

Term Paper # 5. Membranes and Ligaments of Larynx:

1. Thyrohyoid membrane

2. Cricothyroid ligament

3. Cricotracheal ligament

4. Hyoepiglottic ligament

5. Thyroepiglottic ligament

6. Vestibular ligament

7. Vocal ligament

8. Quadrate membrane.

Interior of the Larynx:

There are two mucosal folds present within the larynx. Vestibular folds and vocal folds.

These folds divide the cavity of larynx into three parts:

1. Vestibule:

Lies between laryngeal inlet and vestibular fold (false vocal cords).

2. Ventricle of the Larynx:

It is a space between vestibular folds and vocal folds. The sinus is a recess situated between these folds. Saccule is the anterior ascending part of the sinus. Saccule contains numerous mucous glands, secretion of these glands lubricate the vocal folds.

3. The Infra Glottic Portion:

It extends from vocal cord to the lower border of cricoid cartilage.

Rima Vestibuli:

It is the space between two vestibular folds.

Rima Glottids:

It is the space between two vocal folds (true vocal cords). It has an anterior intramembranous portion and posterior intra cartilaginous portion. It is the narrowest part of the larynx.

Mucous Membrane of the Larynx:

Upto vocal folds – larynx is lined by stratified squamous epithelium.

Below to vocal folds – it is lined by ciliated columnar epithelium.

Mucous glands – are absent over vocal cords and scattered over the rest of the larynx.

Inlet of Larynx:

Directed upwards and backwards.

Communicated superiorly with laryngo pharynx and inferiorly with laryngeal cavity.

Boundaries:

Antero superiorly – upper border of epiglottis.

Laterally – Aryepiglottic folds.

Postero-inferiorly – inter arytenoids fold.

Joints of the larynx – are synovial variety – cricothyroid joint and cricoarytenoids joint.

Term Paper # 6. Blood Supply and Nerve Supply of Larynx:

1. Superior laryngeal branch of superior thyroid artery.

2. Inferior laryngeal branch of inferior thyroid artery.

3. Cricothyroid artery.

Lymphatic Drainage:

Above vocal cords – drained into pre-epiglottic and upper deep cervical lymph nodes.

Below vocal cords – drained into pre-laryngeal lymph nodes.

Pre and para-tracheal group of lymph nodes.

Lower deep cervical group of lymph nodes.

In the glottis lymphatics are absent practically; hence lymphatic spread of carcinoma of vocal cord is late.

Nerve Supply of Larynx:

1. Sensory Supply:

Sensory supply is by vagus nerve.

Above Vocal Cords:

Internal laryngeal branch of superior laryngeal nerve (X).

Below Vocal Cords:

Recurrent laryngeal nerve (X).

2. Motor Supply:

All the muscles of the larynx are supplied by recurrent laryngeal nerve (X) except cricothyroid – supplied by external laryngeal nerve (X).