Layers of the Skin — Hypodermis, Dermis, Epidermis

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Hypodermis/subcutaneous layer

Deepest layer of the skin; composed of insulating connective and adipose tissue (fat).

Reticular Layer

Involved in metabolic processes (temperature regulation through vasoconstriction/vasodilation) and production hair, nails, sweat, and sebum. Contains sensory nerves and made up of collagen protein fibers.

Papillary Layer

Also composed of collagen protein fibers and little bumps called papillae. Papillae push into the basement layer and secure the epi and dermis together. Sensory nerves located here.

Dermoepidermal Junction/Basement membrane

Glue that holds the dermis and epidermis together.

Stratum Basale

Basale as in BASE. Attached to the dermis and has keratinocytes and melanocytes. Keratin is important for skin structure and strength, and melanin for dark pigments and UV protection.

Stratum spinosum

Where cells go from the stratum basale. 8-10 layers of cells that are arranged into a “spine.” They have Langerhans cells; they are like the immune system in the integumentary system.

Stratum granulosum

2-5 layers of dying cells, with two types: keratohyalin and lamellate. Keratohyalin helps the keratinocytes in the upper layers, and lamellate assist in waterproofing the skin.

Stratum lucidum

In those with thicker skin and has thick, dead squamous cells with eleidin (component of keratin.)

Stratum corneum

20-30 cell layers where the waterproof and stretch qualities are made, defense for stimuli.

Epidermis

Contains interstitial fluid (outer cell) that provides important substances. Contains sweat and sebaceous glands,

Desquamation

Outer layer of epidermis is rubbed and replaced by cells in the inferior layer.

Surface Film

Layer of dead skin cells, sweat, sebum that form a protective layer.

Nails

Nail root lies in a bed and nail originates from nail bulb near the epidermis’ blood supply.

Hair

Comprised of hair follicles (where it originates), bulb (multiplies to grow the hair), shaft (hair on skin exterior), and root (hair under the skin).

Sudoriferous (Sweat) Glands

Eccrine sweat glands are located all around the body. Apocrine sweat glands connect to hair follicles in genitals and axillary regions.

Sebaceous Glands

Epithelial cells that are similar to hair follicles. Secretion of sebum.

Arrector Pili

Smooth muscle fibers that contract in response to stimuli of the sympathetic nervous system. Causes goosebumps.