Histology of the larynx

Topography and anatomical segments

Superiorly, the larynx communicates with the pharynx, and inferiorly it continues into the trachea. The internal cavity of the organ is narrowed in the center (like an hourglass), due to which the larynx is topographically and functionally divided into three parts:

1. Upper part (laryngeal vestibule). An expanded portion leading from the laryngeal inlet to the constriction.
2. Middle part. A narrowed region where the vocal apparatus is located.
3. Lower part (infraglotis / infraglottic cavity). An expanded portion of the organ that smoothly transitions into the trachea.

General Plan of Wall Structure

By analogy with the nasal cavity, the submucosa is absent in the wall of the larynx. The wall is formed by three layers:

• Mucous membrane (Mucosa). Characterized by a heterogeneous structure in different areas. This heterogeneity is directly related to the varying functional load on different zones of the larynx.
• Fibromuscular-cartilaginous layer. The middle layer, the thickness and histological composition of which vary depending on the specific region.
• Adventitia. The outer layer formed by loose fibrous connective tissue. A distinctive feature is that it contains more collagen fibers than the lamina propria of the mucosa. Vascular and nerve plexuses run here.

Fibromuscular-cartilaginous layer: the framework of the organ

This layer determines the shape and strength of the larynx. It consists of three interrelated tissue components:

• Cartilaginous component. Represented by two types of cartilage tissue. Hyaline cartilage tissue forms the large cartilages (thyroid and cricoid). Elastic cartilage tissue forms the epiglottis and smaller cartilages (cuneiform, corniculate).
• Fibrous component. The cartilages are united into a single framework by means of ligaments and membranes. They are built from dense regular fibrous connective tissue.
• Muscular component. Represented by both smooth and striated muscle tissue. Smooth myocytes lie within the thickness of the false vocal cords. Skeletal (striated) musculature forms the vocal muscle (within the thickness of the true vocal cords) and seven extrinsic muscles of the larynx, which ensure the acts of swallowing and speech.

Vocal apparatus

The vocal apparatus is located in the narrowed middle part of the larynx. Its basis is formed by two pairs of folds and the depressions between them:

1. Vestibular folds (false vocal cords). The upper pair of folds. They are called "false" because they lack skeletal muscle tissue in their base (contain only smooth myocytes). Because of this, they cannot change the lumen of the rima glottidis and do not participate in phonation.
2. Vocal folds (true vocal cords). The lower pair of folds. Within their thickness are the vocal ligaments and vocal muscles, formed by striated skeletal musculature. They actively participate in phonation.
3. Laryngeal ventricles. Recesses located between the false and true folds. Sometimes they extend upward, forming blind appendices of varying lengths.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Cellular structure of the laryngeal mucosal epithelium in different regions
• Correlation of the functional load on the mucosa with its histological structure
• Features of laryngeal innervation (vascular and nerve plexuses of the adventitia)
• Microscopic structure of the blind appendices of the laryngeal ventricles

Other topics in the "Respiratory Organs" section

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