Functions and Layers of the Skin

Study Notes

The epidermis is the outermost layer of the skin and consists of five layers: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale.
The stratum basale is the deepest layer of the epidermis and is responsible for cell division.
The stratum corneum is the outermost layer of the epidermis and consists of dead, keratinized cells.
The stratum lucidum is a thin layer found only in thick skin and is composed of clear cells filled with a gel-like substance called eleidin.

The dermis is the layer beneath the epidermis and is composed of connective tissue.
It contains blood vessels, nerves, hair follicles, and sweat glands.
The hypodermis, or subcutaneous layer, is located beneath the dermis and connects it to underlying tissues.
The stratum corneum is thickest on the palms and soles of the feet.
Fingerprints are formed by the dermal papillae, which are projections of the dermis into the epidermis.
The arrector pili are smooth muscles that attach to hair follicles and cause goose pimples when they contract.
Prolonged exposure to the sun causes melanocytes to increase melanin production.

The hair follicle is an invagination of the epidermis that extends into the dermis.
Fingernails grow because cells in the stratum germanitivum undergo mitosis.
Each hair shaft has multiple parts: cortex, root, medulla, shaft, papilla, and follicle.

Sweat glands are responsible for producing sweat, which is a fluid secreted through the skin to regulate temperature.
Eccrine sweat glands are the most numerous and widespread type of sweat gland in the body.

Ceruminous glands are located in the external ear canal and produce cerumen (earwax).

A second-degree burn involves damage to the epidermis and upper dermis, causing pain, swelling, and blisters.
A third-degree burn involves destruction of the epidermis and dermis, causing insensitivity to pain.

The dermis is connective tissue, and the epidermis is epithelial tissue.
The stratum corneum is the barrier area of the skin.
The stratum spinosum contains cells that look prickly because of the desmosomes that join them together.
The stratum lucidum contains closely packed, clear cells that contain a gel-like substance called eleidin.

Burns can be caused by ultraviolet light, corrosive chemicals, and electrical current.

The epidermis is constantly being replaced as cells are shed from the surface and new cells are produced in the stratum basale.
Prolonged exposure to the sun causes increased melanin production.
Only the epidermis continually undergoes shedding and regeneration.

Smooth muscles in the skin cause goose pimples, elevation of the testes, and erection of the nipples when they contract.

Melanin is the primary determinant of skin color.
Albinism results from a lack of tyrosinase, which is an enzyme involved in melanin production.

The shedding of epithelial elements from the skin surface is called desquamation.

The Rule of Nines is a method for estimating the percentage of body surface area affected by a burn.
The body is divided into 11 regions and each region is assigned a percentage of the total body surface area:
- Head: 4.5%
- Arm: 4.5%
- Trunk: 18%
- Leg: 9%
- Pubic: 1%

Stratum Corneum: the most superficial layer of the epidermis, composed of very thin squamous cells.
Stratum Lucidum: cells are filled with a gel-like substance called eleidin.
Stratum Basale: cells undergo mitosis.
Stratum Granulosum: cells are filled with keratohyalin.
Stratum Spinosum: contains prominent intercellular bridges or desmosomes.