Larynx

The Larynx

• Anatomy & Physiology

Larynx

‎ Lies in front of the laryngo- pharynx from the level of the third to the sixth cervical vertebrae.
Consists of a framework of cartilages, connected by ligaments and membranes, lined by a mucous membrane and moved by muscles.

Infantile larynx

Absolutely and relatively smaller.
Funnel-shaped.
‎Much softer therefore collapse more easily in forced inspiration.
Lies high up under the tongue.
The plane of its inlet is less oblique.

Laryngeal cartilages

‎Unpaired crtilages
‎ Thyroid cartilage

‎The largest, each half consists of:
‎ 1. Ala (lamina)
‎The two alae meet in the midline, forming an angle of about 90ْ in men, about 120ْ in women.
‎ 2. Superior cornu.
‎ 3. Inferior cornu.
‎Cricoid cartilage
‎Thicker and stronger , a signet ring, narrow in front, broad behind.

‎ Cartilage of epiglottis
Rises up behind the tongue. It is a thin leaf-like sheet of elastic fibrocartilage.
‎


Paired cartilages
‎1. Arytenoid cartilages
‎Largest. pyramidal in shape.
‎Posterior surface is triangular and concave. It extends laterally into a
‎muscular process.
‎Anterolateral surface is convex. It extends forward into a vocal process.
‎Medial surface is narrow, smooth
‎Inferior surface or base, is concave. It articulates with the cricoid cartilage.
‎Apex curves backwards to articulate with the corniculate cartilage
‎2. Corniculate cartilages‎
3. Cuneiform cartilages

Laryngeal ligaments and membranes

‎ ‎1. Intrinsic

‎ ‎2. Extrinsic‎

‎ Thyrohyoid membrane.
Cricotracheal membrane.
Hyo-epiglottic ligament.
Cricothyroid membrane

Laryngeal muscles

‎ ‎1. Intrinsic
‎ A. ‎Abductors of the vocal cords
Posterior crico-arytenoid muscle. Opens the glottis.
Origin - from the depression on the posterior surface of the cricoid lamina.
Direction - upwards and outwards.
Insertion - into the
back of the muscular
process of the
arytenoid cartilage.

B.Adductors of the vocal

‎Lateral crico-arytenoid muscle:
Origin - from the upper border of the
arch of the cricoid cartilage.
Direction - upwards and backwards.
Insertion ­into the front of the
muscular process of the arytenoid
cartilage.




Transverse portion of interarytenoid muscle.
‎External portion of thyro-arytenoid muscle.

C.Tensors of the vocal cords

There are two on each side:
1.Cricothyroid muscle.
2.Internal portion of thyro-arytenoid (vocalis) muscle .

D.Opener of the laryngeal inlet

‎Thyro-epiglottic muscle is a part of the thyro-arytenoid muscles

E.Closers of the laryngeal inlet

‎Oblique portion of interarytenoid muscle
‎Aryepiglottic muscle

2. Extrinsic

‎ ‎'Strap' muscles of the neck

1. Sternothyroid muscle

2. Thyrohyoid muscle
3.Sternohyoid m


Cavity of the Larynx
‎Extends from the inlet into the laryngopharynx, to the lower border of the cricoid cartilage.It is divided into three parts by two folds of mucous membrane:
‎1. False vocal cords ‎
‎2. True vocal cords
‎
‎The mucosal folds divide the cavity into the following parts:
‎a. Vestibule
‎Lies between the inlet and the edges of the false cords
‎b. Ventricle of larynx
‎A recess between the false and true vocal cords.
c. Subglottic space
‎Lies between the true vocal cords and the lower border of the cricoid cartilage .

Mucous membrane of the larynx ‎ ‎

‎
‎All is Ciliated columnar epithelium except that covers vocal cords & upper part of vestibule of larynx is Stratified squamous epithelium

Blood supply of the larynx

‎The larynx is supplied by:
‎1. Laryngeal branches of superior thyroid artery.
‎2. Laryngeal branches of inferior thyroid artery.
‎3. Cricothyroid branches of superior thyroid artery.
Anastomose freely with one another. Veins accompany the arteries.

Nerve supply of the larynx

‎The larynx is supplied by branches of the vagus nerve.
‎Superior laryngeal nerve has two,laryngeal branches:
‎1. Internal branch. Entirely sensory supplies the cavity of the larynx the above the vocal cords.
‎2. External branch motor supplies the cricothyroid muscle
‎Recurrenr (inferior) laryngeal nerve divides into:
‎1. An anterolateral (motor) branch which supplies all the intrinsic muscles of the larynx except the cricothyroid muscle
‎2. Posteromedial (sensory) branch which supplies 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:
‎1. Supraglottic above the vocal cords. The vessels drain into:
‎Pre-epiglottic nodes.
‎Upper deep cervical nodes
‎2. Subglottic below the vocal cords. The vessels drain to:
‎Prelaryngeal and pretracheal nodes.
‎Lower deep cervical nodes
‎The vocal cords themselves have practically no lymphatic vessels.


Applied physiology of the larynx

‎FUNCTIONS OF THE LARYNX

1.Protection of the lower air passages

‎‎1. Closure of the laryngeal inlet

‎ The aryepiglottic folds move towards one another and close the inlet
‎2. Closure of the glottis
‎3. Cessation of respiration
‎4. Cough reflex …'watchdog of the lungs'

2.Phonation

‎ Voice is produced by vibration or the vocal cords
‎ 1. Pitch
‎The vibrations of the cords cut the air column into puffs and the frequency of the puffs determines the pitch produced. The-larynx is therefore a wind instrument. The average individual human voice can produce a frequency range of two octaves in singing.
‎2. 'Volume'
‎The intensity of sound produced by the larynx depends on the air pressure generated in the lungs by contraction of the abdominal and thoracic muscles.

3.Respiration

‎The larynx plays a part in the mechanism of respiration by reflex adjustments of the glottic aperture.

‎4.Fixation of the chest
‎When the larynx is closed the thoracic cage becomes fixed permitting climbing or digging. Since the ribs cannot rise freely , a fixed support is given to the pectoral muscles.