Epidermis — Detailed Notes
1. Definition
The epidermis is the outermost layer of the skin. It is mainly composed of keratinized stratified
squamous epithelium.
It forms a protective barrier between the body and the external environment.
Main functions
Protects the body from mechanical injury.
Prevents excessive loss of water.
Protects against microorganisms.
Provides protection against ultraviolet (UV) radiation.
Participates in immune defense.
Contributes to touch sensation.
Important: The epidermis is avascular, meaning it does not contain blood vessels. It receives
nutrients by diffusion from the underlying dermis.
2. Cells of the Epidermis
There are four major types of cells in the epidermis:
1. Keratinocytes
They are the most abundant cells of the epidermis.
They produce keratin.
They form the major protective barrier of the skin.
They originate mainly from cells in the stratum basale.
, 2. Melanocytes
Present mainly in the stratum basale.
Produce the pigment melanin.
Melanin helps protect skin cells from UV radiation.
Melanin is transferred to surrounding keratinocytes.
3. Langerhans Cells
They are immune cells of the epidermis.
They help recognize and process foreign antigens.
They contribute to the immune defense of the skin.
4. Merkel Cells
Associated with sensory nerve endings.
Important for light-touch sensation.
Mainly found in the stratum basale.
3. Layers of the Epidermis
From deep to superficial, the layers are:
Stratum basale → Stratum spinosum → Stratum granulosum → Stratum lucidum → Stratum
corneum
Mnemonic:
“Before Signing Get Legal Counsel”
B = Basale
S = Spinosum
G = Granulosum
L = Lucidum
1. Definition
The epidermis is the outermost layer of the skin. It is mainly composed of keratinized stratified
squamous epithelium.
It forms a protective barrier between the body and the external environment.
Main functions
Protects the body from mechanical injury.
Prevents excessive loss of water.
Protects against microorganisms.
Provides protection against ultraviolet (UV) radiation.
Participates in immune defense.
Contributes to touch sensation.
Important: The epidermis is avascular, meaning it does not contain blood vessels. It receives
nutrients by diffusion from the underlying dermis.
2. Cells of the Epidermis
There are four major types of cells in the epidermis:
1. Keratinocytes
They are the most abundant cells of the epidermis.
They produce keratin.
They form the major protective barrier of the skin.
They originate mainly from cells in the stratum basale.
, 2. Melanocytes
Present mainly in the stratum basale.
Produce the pigment melanin.
Melanin helps protect skin cells from UV radiation.
Melanin is transferred to surrounding keratinocytes.
3. Langerhans Cells
They are immune cells of the epidermis.
They help recognize and process foreign antigens.
They contribute to the immune defense of the skin.
4. Merkel Cells
Associated with sensory nerve endings.
Important for light-touch sensation.
Mainly found in the stratum basale.
3. Layers of the Epidermis
From deep to superficial, the layers are:
Stratum basale → Stratum spinosum → Stratum granulosum → Stratum lucidum → Stratum
corneum
Mnemonic:
“Before Signing Get Legal Counsel”
B = Basale
S = Spinosum
G = Granulosum
L = Lucidum
