What Are the Seven Layers of Skin?

Human skin is the largest organ and comprises seven layers.

The skin is the body’s largest organ and it is made up of seven layers, each of which has a specific function. The skin is part of the body’s innate immune system and acts as the body’s first barrier against germs, ultraviolet (UV) light, chemicals, and injury. The skin also helps maintain body temperature and prevent water loss from the body.

The first five layers of the skin are part of the epidermis, and next two layers comprise the dermis. The epidermis is the outer layer of skin that protects the body from infections, dehydration, and injury. It also renews cells in the skin. The dermis is the layer beneath the epidermis that contains blood vessels, nerve endings, hair follicles, and sweat glands. The dermis functions to provide elasticity, firmness, and strength to the skin.

Starting from the outermost layer on the surface of the skin, working the way down into the deepest layer, the layers of the skin are: 

1. Stratum corneum
   • This layer is the first line of defense against the environment
   • It is comprised of keratin and helps protect against bacteria and UV damage 
   • It prevents moisture from escaping, which helps skin stay hydrated
2. Stratum lucidum
   • A thin clear layer that is only present in skin that is commonly damaged, such as palms of the hands and soles of the feet
   • It is meant to help the body withstand friction
3. Stratum granulosum
   • This layer acts as the waterproofing layer and keeps the body from losing water
   • The types of fats in this layer keep the skin cells attached to each other
4. Stratum spinosum
   • Also called the prickle cell layer
   • This layer contains dendritic cells, which are part of the body’s immune system that helps fight against foreign invaders such as germs
   • This layer enables the epidermis (outer layer of skin) to better withstand the effects of friction and abrasion
5. Stratum basale 
   • The deepest later of the epidermis, also called the stratum germinativum
   • This is the layer of skin where cell division (mitosis) occurs and skin cells are replenished
   • The cells in this layer produce keratinocytes, which produce keratin, protein, and fats, help the body produce vitamin D when exposed to sunlight
   • This layer also contains melanocytes, which produce melanin, the pigment that colors the skin
6. Papillary Layer
   • This layer connects the dermis to the epidermis 
   • It contains capillaries that bring nutrients to the skin and increase or decrease blood flow to the skin which helps regulate temperature
   • It also contains sensory neurons that help sense heat, cold, touch, pain, and pressure
   • This is the layer of skin that is responsible for fingerprints
7. Reticular Layer
   • The deepest level of the dermis
   • A thick layer composed of composed of dense connective tissue
   • This layer contains hair follicles, sweat glands, and oil-producing glands (sebaceous glands) 
   • The main functions are strengthening the skin and providing elasticity to the skin