MH 038-039 Epiglottis

Elastic Cartilage
(H&E)

The epiglottis is a cartilaginous structure at the root of the tongue that folds over the glottis to prevent food or liquid from entering the trachea during swallowing.

Elastic cartilage is similar to hyaline cartilage except that the matrix also contains a dense network of branching and anastomosing elastic fibers. It provides flexible support and is present in the outer ear and epiglottis.

Elastic and hyaline cartilage have similar appearances when stained by H&E because elastic fibers are unstained. Compare with the next specimen stained with Verhoeff.

Elastic cartilage forms the core of the epiglottis:

• Perichondrium - a layer of dense irregular connective tissue that surrounds cartilage. It is divided into two layers:
  • Outer Fibrous Layer - fibroblasts that produce the type I collagen on the outer surface of the perichondrium.
  • Inner Chondrogenic Layer - contains mesenchymal cells that differentiate into chondroblasts, initiate matrix production (elastin and type II collagen) and become immature chondrocytes.
• Chondrocytes - cells within lacunae inside the cartilage that occur singularly or in clusters called isogenous groups.
• Matrix - composed mostly of elastic fibers, type II collagen and a ground substance of proteoglycans. The streaks of pink within the matrix are due to the presence of elastic fibers.

Elastic cartilage contains no blood vessels or nerves.

Elastic Cartilage
(Verhoeff Stain)

This is the same specimen but stained with Verhoeff to show the elastic fibers, stained black, within the cartilage matrix.

Elastic cartilage forms the core of the epiglottis:

• Perichondrium - a layer of dense irregular connective tissue that surrounds cartilage. It is divided into two layers:
  • Outer Fibrous Layer - the type I collagen on the outer surface of the perichondrium is stained light pink/red.
  • Inner Chondrogenic Layer - contains unstained fibroblast-like cells, chondroblasts, and immature chondrocytes.
• Chondrocytes - cells within lacunae inside the cartilage that occur singularly or in clusters called isogenous groups.
• Matrix - composed mostly of elastic fibers, type II collagen and a ground substance of proteoglycans. The elastic fibers are intensely stained black.

Elastic cartilage contains no blood vessels or nerves.