The site's 3D body has little skin detail, so this page is built from open diagrams, microscope slides and short descriptions. Each description is copied word for word from its source, which is linked. Not reviewed by a clinician; for education, not clinical use.
The three layers
Basically, the skin is comprised of two layers that cover a third fatty layer. These three layers differ in function, thickness, and strength. The outer layer is called the epidermis; it is a tough protective layer that contains the melanin-producing melanocytes. The second layer (located under the epidermis) is called the dermis; it contains nerve endings, sweat glands, oil glands, and hair follicles. Under these two skin layers is a fatty layer of subcutaneous tissue, known as the subcutis or hypodermis.
Source: "SEER Training Modules" by National Cancer Institute · Public domain (US government work) · copied unchanged; not reviewed by a clinician · Report a mistake
Epidermis
The epidermis is the outermost of the three major layers that constitute the skin, the inner layers being the dermis and hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss. The epidermis is composed of multiple layers of flattened cells that overlie a base layer (stratum basale) composed of perpendicular columnar cells. The human epidermis is an example of epithelium, particularly a stratified squamous epithelium.
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Layers of the epidermis
The basal layer is the innermost layer of the epidermis, and contains small round cells called basal cells. The squamous cell layer is located above the basal layer, and is also known as the stratum spinosum or "spiny layer" due to the fact that the cells are held together with spiny projections. The stratum corneum is the outermost layer of the epidermis, and is made up of 10 to 30 thin layers of continually shedding, dead keratinocytes.
Source: "SEER Training Modules" by National Cancer Institute · Public domain (US government work) · copied unchanged; not reviewed by a clinician · Report a mistake
Stratum corneum
The stratum corneum (Latin for 'horned/horny layer') is the outermost layer of the epidermis of the tetrapod skin. In human skin, it consists of a stratified squamous epithelium made of 15 to 20 layers of corneocytes, flattened, terminally differentiated keratinocytes that have lost their nuclei or organelles.
Source: "Stratum corneum" by Wikipedia contributors · CC BY-SA 4.0 · copied unchanged; not reviewed by a clinician · Report a mistake
Dermis
The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided into two layers, the superficial area adjacent to the epidermis called the papillary region and a deep thicker area known as the reticular dermis. The dermis is tightly connected to the epidermis through a basement membrane.
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Papillary and reticular dermis
The upper, papillary layer, contains a thin arrangement of collagen fibers. The lower, reticular layer, is thicker and made of thick collagen fibers that are arranged in parallel to the surface of the skin. The reticular layer is denser than the papillary dermis, and it strengthens the skin, providing structure and elasticity.
Source: "SEER Training Modules" by National Cancer Institute · Public domain (US government work) · copied unchanged; not reviewed by a clinician · Report a mistake
Hypodermis (subcutaneous tissue)
The subcutaneous tissue (from Latin subcutaneous 'beneath the skin'), also called the hypodermis, hypoderm (from Greek 'beneath the skin'), subcutis, or superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and macrophages. The subcutaneous tissue is derived from the mesoderm, but unlike the dermis, it is not derived from the mesoderm's dermatome region. It consists primarily of loose connective tissue and contains larger blood vessels and nerves than those found in the dermis.
Source: "Subcutaneous tissue" by Wikipedia contributors · CC BY-SA 4.0 · copied unchanged; not reviewed by a clinician · Report a mistake
Thick and thin skin
The color, thickness and texture of skin vary over the body. There are two general types of skin; thin and hairy, which is more prevalent on the body, and thick and hairless, which is found on parts of the body that are used heavily and endure a large amount of friction, like the palms of the hands or the soles of the feet.
Source: "SEER Training Modules" by National Cancer Institute · Public domain (US government work) · copied unchanged; not reviewed by a clinician · Report a mistake
Hair follicle
The hair follicle is an organ found in mammalian skin. Residing in the dermal layer of the skin, each hair follicle is made up of 20 different types of mammalian cells, each with distinct functions.
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Arrector pili muscle
The arrector pili muscles, also known as hair erector muscles, are small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end, known colloquially as goose bumps (piloerection).
Source: "Arrector pili muscle" by Wikipedia contributors · CC BY-SA 4.0 · copied unchanged; not reviewed by a clinician · Report a mistake
Sebaceous gland
A sebaceous gland or oil gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest number on the face and scalp, but also on all parts of the skin except the palms of the hands and soles of the feet.
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Sweat glands
Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial surface by way of a duct.
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Eccrine sweat gland
Eccrine sweat glands are found in virtually all skin, with the highest density in the palms of the hands, and soles of the feet, and on the head, but much less on the torso and the extremities.
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Apocrine sweat gland
In humans, apocrine sweat glands are found only in certain locations of the body: the axillae (armpits), areola and nipples of the breast, ear canal, eyelids, wings of the nostril, perineal region, and some parts of the external genitalia. They are distinct from eccrine sweat glands, which cover the whole body.
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Nail
A nail is a protective plate characteristically found at the tip of the digits (fingers and toes) of almost all primates (except for marmosets), homologous to the claws in other tetrapod animals. Fingernails and toenails are made of a tough rigid protein called alpha-keratin, a polymer also found in the claws, hooves, and horns of vertebrates.
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Melanocytes
Melanocytes are melanin-producing neural crest-derived cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), the inner ear, vaginal epithelium, meninges, bones, and heart found in many mammals and birds. Melanin is a dark pigment primarily responsible for skin color. Once synthesized, melanin is contained in special organelles called melanosomes which can be transported to nearby keratinocytes to induce pigmentation. Thus darker skin tones have more melanosomes present than lighter skin tones.
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Langerhans cells
A Langerhans cell (LC) is a tissue-resident macrophage of the skin once thought to be a resident dendritic cell. These cells contain organelles called Birbeck granules. They are present in all layers of the epidermis and are most prominent in the stratum spinosum.
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Merkel cell
Merkel cells, also known as Merkel–Ranvier cells or tactile epithelial cells, are oval-shaped mechanoreceptors essential for light touch sensation and found in the skin of vertebrates. They are abundant in highly sensitive skin like that of the fingertips in humans, and make synaptic contacts with somatosensory afferent nerve fibers.
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Meissner corpuscle
The tactile corpuscle, or Meissner's corpuscle, is a type of mechanoreceptor discovered by anatomist Georg Meissner (1829–1905) and Rudolf Wagner. This corpuscle is a type of nerve ending in the skin that is responsible for sensitivity to pressure. In particular, it has its highest sensitivity (lowest threshold) when sensing vibrations between 10 and 50 hertz. It is a rapidly adaptive receptor. They are most concentrated in thick hairless skin, especially at the finger pads.
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Pacinian corpuscle
The Pacinian corpuscle (also lamellar corpuscle, or Vater–Pacini corpuscle) is a low-threshold mechanoreceptor, responsive to deep pressure, stretch, tickle and vibration, found in the skin and other internal organs. In the skin it is one of the four main types of cutaneous receptors. Pacinian corpuscles are rapidly adapting mechanoreceptors.
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Free nerve endings
A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. They function as cutaneous nociceptors and are essentially used by vertebrates to detect noxious stimuli that often result in pain.
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Blood supply
The blood vessels supply nutrients and oxygen to the skin and take away cell waste and cell products. The papillary layer supplies nutrients to select layers of the epidermis and regulates temperature. Constriction and expansion control the amount of blood that flows through the skin and dictate whether body heat is dispelled when the skin is hot or conserved when it is cold.
Source: "SEER Training Modules" by National Cancer Institute · Public domain (US government work) · copied unchanged; not reviewed by a clinician · Report a mistake