Anatomy of Larynx

Larynx

Larynx is the voice box & it also serves as an air passage

Extends from root of the tongue at the inlet of the larynx to the commencement of trachea at the level of 6th cervical vertebra

The cavity of the larynx is continuous below with the trachea, and above opens into the laryngopharynx.

SKELETON OF THE LARYNX

The skeletal framework of the larynx is formed

by a series of cartilages interconnected by

ligaments and fibrous membranes.

Cartilages of Larynx

The cartilages of the larynx are nine in number, three single and three paired.

Three single are thyroid, cricoid and epiglottis.

Three paired are arytenoid ,corniculate and cuneiform .

Thyroid cartilage

It is the Largest cartilage

Made of 2 quadrangular plates

Each plate has 2 surfaces :Inner &outer

4 Borders : Upper,Lower,anterior,posterior

Anterior border

Anterior borders unites at an angle : Laryngeal prominence (Adams apple)

separated by Thyroid notch

Posterior border

Posterior borders : Prolonged upwards & downwards called Sup. &Inf. horns

Superior horn: Lateral thyrohyoid ligament

Inferior horn: Facet at the medial surface for cricoid arch

Cricoid cartilage

Signet ring shaped

Having posterior quadrilateral lamina & an anterior narrow arch

Cricoid Lamina:

Posterior surface:

Median ridge to which the tendinous bands from Longitudnal muscles of oesophagous are attached

Each side:

2 depressions for attatchment of posterior crico-arytenoid muscle

Upper border - 2 facets for articulation with the base of arytenoids

Cricoid arch

Rough external surface having circular facet on each side for articulation with the inferior horn of the thyroid cartilage

Lower border of cartilage:Attachment to Cricotracheal membrane

Epiglottis

Oblong leaf shaped

2ends, upper & Lower

2 surfaces, Anterior &Posterior

2Lateral borders

The lower end attachs to inner surface of thyroid cartilage below thyroid notch by the thyroepiglottic ligament

Arytenoid cartilage

These are placed on the upper border of the lamina of the cricoid

Pyramidal in shape

It has an apex ,base, 3 surfaces-Medial , Lateral & anterolateral

Base-a facet which articulates with the upper border of the cricoid lamina

Apex articulates with corniculate cartilage

Medial surfaces faces each other

Anterolateralsurface-------------- 2 depressions,seperated by a ridge , for muscle (vocalis) &

Ligament(vestibular ligament)

Lateral angle of the base projects laterally as muscular process

Anterior angle of the base projects forwards as the vocal processto which the vocal ligament is attached.

Ligaments of larynx

Extrinsic ligaments

These ligaments lie external to the larynx and connect the larynx with the hyoid bone and trachea.

Thyrohyoid membrane

It spans between the superior margin of the thyroid cartilage below and the hyoid bone above.

Its poserior borders thickened to form the lateral thyroid ligaments.

It thickens anteriorly in the the midline to form the median thyrohyoid ligament.

Hyo-epiglottic ligament

The hyo-epiglottic ligament extends from the midline of the epiglottis to the body of the hyoid bone.

It connects the epiglottis with the hyoid bone.

Cricotracheal ligament

The cricotracheal ligament runs from the lower border of the cricoid cartilage to the upper border of the first tracheal cartilage.

The larynx is attached to the trachea by this ligament.

Intrinsic ligaments

They lie within the cartilaginous skeleton of the larynx and connect the thyroid, cricoid and arytenoid cartilages .

Quadrangular membrane

It passes between lateral margin of the epiglottis and the arytenoid cartilage on the same side.

The upper border slopes posteriorly to form the aryepiglottic ligament which constitute the central component of aryepiglottic fold

The lower border forms the the vestibular fold (false vocal cord).

Cricovocal membrane

It is attached to the arch of cricoid cartilage and extends superiorly to end in a free upper margin.

The free upper margin attaches anteriorly to the thyroid cartilage and posteriorly to the vocal processes of the arytenoid cartilages

The upper free margin is thickened to form the vocal ligament, which is under the vocal fold (true 'vocal cord') of the larynx.

The cricothyroid ligament is also thickened anteriorly in the midline to form the median cricothyroid ligament.

Laryngeal joints

Cricothyroid joint

This joint happens between the inferior horns of the thyroid cartilage and lateral surface of the lamina of cricoid cartilage.

It is a synovial joint.

The cricothyroid joints enable the thyroid cartilage to move forward and tilt downwards on the cricoid cartilage and effectively lengthens and puts tension on the vocal ligaments.

Crico-arytenoid joints

It is between the articular facets on the superolateral surfaces of the cricoid cartilage and the bases of the arytenoid cartilages.

It is a synovial joint.

It enables the arytenoid cartilages to slide away or towards each other and to rotate.

These movements abduct and adduct the vocal ligaments .

Cavity of the larynx

The laryngeal cavity extends from the laryngeal inlet down to the lower border of the cricoid cartilage, where it continues into the trachea.

It is divided into three parts by the vestibular and vocal folds ：the Vestibule, Sinus and Infraglottic space

Vestible

It is the part situated between the laryngeal inlet and the vestibular fold.

Sinus

Sinus is the middle part between the vestibular folds above and the vocal folds below.

Infraglottic space

The infraglottic space is the most inferior chamber of the laryngeal cavity and is between the vocal folds and the inferior opening of the larynx.

Named parts of parietal pleura

The names given to the parietal pleura correspond to the parts of the wall with which they are associated

pleura related to the ribs and intercostal spaces is termed the costal part;

pleura covering the diaphragm is the diaphragmatic part;

pleura covering the mediastinum is the mediastinal part;

the dome-shaped layer of parietal pleura lining the cervical extension of the pleural cavity is dome of pleura

Pleuracentesis

through the 7th or 8th intercostal space，on the posterior axillary line, along the superior border of the lower rib