Connection lost. Please refresh the page.
Get help How to study Login Register
Ready to learn?
Pick your favorite study tool


Recommended video: Skin [38:23]
General histology of the skin.

The keratinocytes are the primary cell of the epidermis. They originate in the deepest layer of the epidermis- stratum basale and continue to the outer most layer - stratum corneum.

In the basal layer, the keratinocytes contain a number of cells including : free ribosomes, small golgi apparatus, mitochondria, intermediate filaments and the rough endoplasmic reticulum. 

In histologic sections, the cytoplasm of immature keratinocytes appears basophilic due to the abundance of free ribosomes, most of which are involved in synthesizing keratins that will later form keratin filaments. These keratin filaments are known as intermediate filaments but are commonly referred to as tonofilaments.

As keratinocytes progress through the stratum spinosum, the synthesis of keratin filaments continues, and they start grouping together into bundles called tonofibrils. These bundles are thick enough to be visible under a light microscope. As a result, the cytoplasm becomes eosinophilic due to the staining reaction of the tonofibrils that occupy an increasing portion of the cytoplasm.

As the keratinocytes start entering the stratum granulosum, they synthesise keratohyalin granules. These granules are a characteristic feature of cells in the stratum granulosum. They contain two essential intermediate filament-associated proteins: filaggrin, and trichohyalin

Keratinocytes are also known for an important process called keratinization. During keratinization, the number of keratohyalin granules increases in the keratinocytes and their contents are released into the cytoplasm. Filaggrin and trichohyalin, play a crucial role in this process. They act as promoters, facilitating the aggregation of keratin filaments into structures called tonofibrils. This aggregation initiates the transformation of granular cells into cornified cells

Keratinization is a time-consuming process, taking about 2 to 6 hours for cells to move from the stratum granulosum to the outermost layer of the skin, known as the stratum corneum. The keratin fibril formed during this process is called soft keratin, which is different from the hard keratin found in hair and nails. This transformation results in the formation of a protective and durable outer layer for the skin. 

The keratohyaline granules also produce lamellar bodies. These lamellar bodies contribute to the formation of the intercellular epidermal water barrier. This the e barrier is crucial for preserving body homeostasis and maintaining a vital role in mammalian "dry" epithelia,

Terminology:  Keratinocyte
Location:  Found in the epidermis - from the stratum basale to the stratum corneum
Function: Essential for protecting the organism from the external environment. 

Learn more about Keratinocytes in this study unit: 

Keratinocytes: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

What do you prefer to learn with?

“I would honestly say that Kenhub cut my study time in half.” – Read more.

Kim Bengochea Kim Bengochea, Regis University, Denver
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Register now and grab your free ultimate anatomy study guide!