Skin and Structures

Skin

The largest organ of the body, weighing 8 lbs and covering 22 sq. ft., part of the integumentary system that serves to protect.

Integumentary System

The system that includes the skin and its accessory structures, primarily serving protective functions.

Epidermis

The outermost layer of skin, avascular, composed of keratinized stratified squamous epithelial cells.

Dermis

The middle layer of skin, vascular, containing the papillary and reticular layers made of connective tissue.

Hypodermis

Also known as the subcutaneous layer, it connects the skin to underlying fascia and is composed of loose, vascularized areolar and adipose tissue.

Melanin

A pigment that influences skin color, transferred into skin layers via vesicles, and increases with UV exposure for DNA protection.

Hair

Composed of dead, keratinized cells, serving functions such as protection, sensory input, thermoregulation, and communication.

Hair Follicle

The structure from which hair grows, penetrating the dermis.

Nails

Composed of densely packed keratin, formed at the nail root, appearing pink due to rich blood vessels.

Lunula

The white crescent-shaped region of the nail, a visible part of the matrix.

Sweat Glands

Also known as sudoriferous glands, they are responsible for producing sweat and are classified into eccrine and apocrine types.

Eccrine Sweat Glands

Glands that release hypotonic sweat for thermoregulation, found in areas like palms and soles.

Apocrine Sweat Glands

Larger glands associated with hair follicles in dense hair regions, producing sweat that can decompose and smell.

Protection (Function)

The skin's role in defending against elements like wind, water, UV rays, and preventing water loss.

Sensory (Function)

The ability of skin to detect touch, temperature, and pain through specialized nervous structures in all three layers.

Thermoregulation (Function)

The process by which the skin helps regulate body temperature through sweating and blood vessel dilation or constriction.

Vitamin D

A nutrient synthesized in the epidermis when exposed to UV radiation, essential for calcium and phosphorus absorption and general immunity.