Integument

Epidermis

The outermost layer of skin, primarily composed of keratinocytes, it serves as a barrier against environmental factors and aids in regulating moisture and temperature.

Dermis

The layer of skin located beneath the epidermis, consisting of connective tissue, blood vessels, and nerves.

Hypodermis

The deepest layer of the integument, consisting of areolar tissue and adipose tissue, which provides insulation and cushioning.

Keratinocyte

The primary cell type found in the epidermis, responsible for producing keratin, which helps protect the skin from damage and water loss.

Melanocyte

A cell located in the basal layer of the epidermis that produces melanin, the pigment responsible for skin color.

Stratum basale

The deepest layer of the epidermis, consisting mainly of a single row of keratinocytes and melanocytes, where active cell division occurs.

Stratum spinosum

The layer of the epidermis above the stratum basale, characterized by spiny appearance due to desmosomal connections and where keratinocytes begin to flatten and mature.

Stratum granulosum

The layer of the epidermis situated above the stratum spinosum, characterized by the presence of keratinocytes that contain granules of keratohyalin. It plays a crucial role in the process of keratinization.

Stratum lucidum

The thin, transparent layer of the epidermis found only in thick skin areas such as the palms and soles. It consists of several rows of dead keratinocytes and provides an additional barrier to water loss.

Stratum corneum

The outermost layer of the epidermis, consisting of dead keratinized cells that provide a barrier to protect underlying tissues and prevent water loss.

Hair follicle

Tube-like structure that encases the root of a hair, extending into the dermis. It is responsible for hair growth and housing sebaceous glands that produce oil, aiding in the health of hair.

Sebaceous gland

A small oil-producing gland associated with hair follicles, responsible for secreting sebum that lubricates the hair and skin. A holocrine gland.

Sweat gland

A coiled tubular gland located in the dermis that secretes sweat to help regulate body temperature and eliminate waste. There are two types: merocrine and apocrine glands.

Arrector pili muscle

A small muscle attached to hair follicles that causes hair to stand upright when contracted, usually in response to cold or emotional stimuli, contributing to heat retention and piloerection.

Papillary layer

The upper layer of the dermis situated just beneath the epidermis, composed of loose connective tissue and containing capillaries, lymphatics, and nerve endings.

Reticular layer

The deeper layer of the dermis, composed of dense connective tissue, which provides strength and elasticity to the skin. It contains larger blood vessels, lymphatic vessels, and nerve endings.

Thick skin vs. Thin skin

Thick skin refers to skin that has a thicker epidermis, typically found on the palms of the hands and soles of the feet, while thin skin has a thinner epidermis and covers most of the body. Thick skin contains no hair follicles but has more sweat glands compared to thin skin.

Vasoconstriction

The process by which blood vessels constrict to reduce blood flow and conserve body heat, often in response to cold temperatures.

Vasodilation

The process where blood vessels widen to increase blood flow, often resulting in decreased blood pressure and increased heat loss from the body.

Transdermal absorption

The method by which substances are absorbed into the body through the skin, allowing for the delivery of medications directly into systemic circulation.