27 Questions
Which layer of the epidermis contains cells that participate in the immune response?
Stratum spinosum
Which layer of the epidermis is responsible for the formation of protective, superficial layers of cells filled with keratin?
Stratum corneum
What is the basic structural component of hair and nails in humans?
Keratin
Which layer of the epidermis is only present in thick skin?
Stratum lucidum
Which layer of the epidermis forms epidermal ridges that extend into the dermis?
Stratum basale
Which cells dominate the epidermis and form several layers?
Keratinocytes
What is the main function of the epidermis?
Provides physical protection for the dermis
Which layer of the epidermis is responsible for the synthesis of pigment by melanocytes?
Stratum basale
What is the process of the formation of protective, superficial layers of cells filled with keratin called?
Keratinization
Which layer of the epidermis is responsible for insensible perspiration?
Stratum corneum
Which layer of the epidermis is avascular and relies on the diffusion of nutrients and oxygen from capillaries within the dermis?
Epidermis
Which layer of the epidermis contains the body's most abundant epithelial cells?
Stratum basale
Which layer of the epidermis is responsible for the synthesis of pigment by melanocytes?
Stratum basale
Which layer of the epidermis forms epidermal ridges that extend into the dermis?
Stratum basale
Which layer of the epidermis contains cells that participate in the immune response?
Stratum spinosum
Which layer of the epidermis is only present in thick skin?
Stratum lucidum
What is the process of the formation of protective, superficial layers of cells filled with keratin called?
Keratinization
Which layer of the epidermis is responsible for insensible perspiration?
Stratum corneum
Which layer of the epidermis contains tactile (Merkel) cells?
Stratum basale
What is the basic structural component of hair and nails in humans?
Keratin
What is the main function of the epidermis?
Physical protection and prevention of water loss
What is the name of the protein that is a tough, fibrous protein and the basic structural component of hair and nails in humans?
Keratin
What is the name of the protein made by keratinocytes in the stratum granulosum that promotes dehydration of the cell as well as aggregation and cross-linking of the keratin fibers?
Keratohyalin
What is the name of the growth factor that promotes the divisions of basal cells in the stratum basale and stratum spinosum, as well as accelerates the production of keratin in differentiating keratinocytes?
Epidermal Growth Factor (EGF)
Explain the process of keratinization and its role in the formation of protective layers in the epidermis.
Keratinization, or cornification, is the formation of protective, superficial layers of cells filled with keratin. This process takes place on all exposed skin surfaces except the anterior surfaces of the eyes. The dead cells in each layer of the stratum corneum remain tightly interconnected by desmosomes, creating water-resistant layers.
Describe the role of epidermal growth factor (EGF) in the epidermis and its source of production.
EGF is produced by the salivary glands and glands of the duodenum. It promotes the divisions of basal cells in the stratum basale and stratum spinosum, accelerates the production of keratinization in differentiating keratinocytes, and stimulates epidermal development and repair after injury.
Discuss the characteristics and functions of the stratum lucidum in the epidermis.
The stratum lucidum is a glassy, clear layer that covers the stratum granulosum, found only in thick skin. Its cells are flattened, densely packed, largely without organelles, and filled with keratin. It contributes to the toughness and water resistance of the skin.
Study Notes
Epidermis
- The epidermis is a stratified squamous epithelium that provides physical protection, prevents water loss, and keeps microorganisms out of the body.
Characteristics of Epidermis
- Avascular, relying on diffusion of nutrients and oxygen from dermal capillaries
- Epidermal cells with high metabolic demands are found close to the basement membrane
- Superficial cells are dead
Cells of the Epidermis
- Keratinocytes dominate the epidermis, forming multiple layers and containing keratin
- Keratin is a tough, fibrous protein also found in hair and nails
Layers of the Epidermis
- Thin skin has 4 layers, covering most of the body
- Thick skin has 5 layers, covering palms of hands and soles of feet
Stratum Basale
- The deepest layer of the epidermis
- Dominated by basal cells (stem cells) that divide to replace superficial keratinocytes
- Contains melanocytes that synthesize pigment, tactile (Merkel) cells, and hemidesmosomes that attach to the basement membrane
Stratum Spinosum
- Keratinocytes bound together by desmosomes
- Contains dendritic cells (Langerhans cells) that stimulate defense against microorganisms and superficial skin cancer
Stratum Granulosum
- Cells stop dividing and start making large amounts of keratin
- Cells grow thinner, flatter, and their plasma membranes thicken and become less permeable
- Keratohyalin promotes dehydration and aggregation of keratin fibers
Stratum Lucidum
- Only found in thick skin
- A glassy, clear layer with flattened, densely packed cells filled with keratin
Stratum Corneum
- The exposed surface of both thick and thin skin
- Contains 15-30 layers of keratinized cells
- Dead cells remain tightly interconnected by desmosomes
- Cells are shed in large groups or sheets rather than individually
Epidermal Growth Factor (EGF)
- Produced by salivary glands and duodenal glands
- Promotes divisions of basal cells, accelerates keratin production, and stimulates epidermal development and repair after injury
Test your knowledge of the epidermis with this quiz. Explore the functions and characteristics of the epidermal layer, including its role in providing protection, preventing water loss, and maintaining a barrier against microorganisms.
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