Rochelle Collins, DO, is board-certified in family members medicine. She is an assistant clinical professor of family members medicine at Quinnipiac University and works in private practice in Hartford, Connecticut." data-inline-tooltip="true">Rochelle Collins, DO

Verywell / Alexandra Gordon


The skin is part of the integumentary system, which also includes the nails, hair, and also exocrine glands. That is an incredibly large organ, bookkeeping for 15% of one adult's complete body weight.

Total skin thickness varies relying on where it is discovered on the body. The thickest skin is found on the back, the palms of the hands, and also the bottom of the feet, whereby it can be up to 3 millimeter (mm) thick. The thinnest skin is uncovered on the eyelid, wherein the epidermis measures simply 0.05 mm with very small dermis and subcutaneous fat.

The three significant layers the the skin every contain committed cells, tissues, and also appendages, and also each performs unique functions for the body.

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The epidermis is the outermost great of the skin, the layer of skin i m sorry is visible. The epidermis is additionally the thinnest that the three skin layers. The is an avascular skin layer, so it does not contain blood vessels.

Important cell types of the epidermis include:

Keratinocytes: The vast bulk of the epidermis is made up of keratinocytes. Keratinocytes room cells the manufacture keratin, the structure protein that makes up skin, hair, and also nails. Keratin is what creates the protective, water-resistant obstacle of the skin.Langerhans cells: this account for just a small number of cells in ~ the epidermis, however have crucial function. Langerhan"s cell are devoted cells that work-related with the immune device to defend the skin from international pathogens.Merkel cells: these touch receptor cells are most countless in high tactile locations such together the fingertips, lips, and also around the hair shaft. This cells secrete a chemical that relays information directly to the brain, allowing the skin to sense even the lightest touch.

The epidermis chin is made up of four layers, through some locations having a committed fifth epidermal layer.

The four layers that the epidermis are:

Stratum basale: This is the deepest class of the epidermis, and also is made up of a solitary layer the basal cells. The is from this column-shaped cells that keratinocytes room created. Melanocytes and also Merkel cells are likewise found in this layer. The stratum basale is likewise called the basal layer or stratum germinativum.Stratum spinosum: This is the thickest great of the epidermis. Together cells undergo mitosis (cell division) in the great below, the newly-formed keratinocytes are thrust up into the stratum spinosum. Also found in this layer space Langerhan's cells.Stratum granulosum: As brand-new keratinocytes are moved up right into this layer they proceed to readjust in size and also shape, coming to be harder and flatter, creating a class that has actually a granular appearance. The cabinet nucleus and also organelles begin to dice in this layer, leaving behind tough keratin.Stratum lucidum: This is the dedicated fifth class of the epidermis, and it is discovered only top top the palms that the hands and soles the the feet. That adds one extra layer of protection to these areas. The class is consisted of of dead, planarization cells.Stratum corneum: likewise called the horny layer, this is the uppermost layer of the epidermis. The is comprised of tightly-packed, keratinized cells. When they've reached this layer, keratinocytes have actually died, flattened, hardened, and also are now called corneocytes. These cells produce the waterproof, protective barrier of the skin surface. As new corneocytes are created and pushed to the surface, old corneocytes are shed.

The dermis has two layers: the papillary layer and the reticular layer.

The papillary layer is the layer closest come the epidermis. The dermis and also epidermis are connected by finger-like projections dubbed dermal papillae. The dermal papillae send nutrient to the epidermis with a process called diffusion. In ~ the papillary class are wealth of tiny blood vessels, phagocytes (protective cells that ingest pathogens), nerve fibers, and tactile receptors called corpuscles.

Within the reticular great of the dermis space found:

Sudoriferous glands: these are also known together sweat glands, of i beg your pardon there space two types—eccrine and also apocrine. Eccrine glands are coiled glands which produce sweat and also are an essential in helping manage body temperature. These glands likewise excrete small amounts of garbage product such as urea, lactic and also uric acid, ammonia. Apocrine are plenty of in the armpit and also groin area and aren"t active until puberty. The apocrine glands create a type of sweat that is conveniently digested by bacteria and is responsible for leading to body odor.Arrector pili muscle: The arrector pili muscle is a small muscle that is attached come the basic of a hair. As soon as it contracts, it creates a goosebump and also makes the hair was standing on end.Ceruminous glands: These dedicated glands, only discovered in the dermis within the ear canal, develop earwax.Lymph vesselsBlood vesselsSensory receptors

Subcutaneous layer

The upper 2 layers the the skin sit atop the subcutaneous tissue. This class is sometimes called the hypodermis or panniculus.

This layer is primarily made up of fatty tissue dubbed adipose tissue. This is whereby the human body reserves that fat stores.

The subcutaneous class is likewise made increase of loose connective tissue, larger blood vessels, and also nerves. This layer helps connects the top skin to the musculature below.

This layer different in thickness relying on where it's uncovered on the body (it's thickest ~ above the buttocks, palms, and also feet) and also age, sex, and health of one individual.

Anatomical sport

Skin thickness varies by age. The skin becomes progressively thicker until about age 40, when it reverses its course and also slowly thins. These transforms occur greatly in the dermis.

There is part indication that men, biologically, have in its entirety thicker skin 보다 women. part studies, though, have discovered no far-reaching difference between the thickness of masculine versus mrs skin.


The skin carries the end several an essential functions.


The main purpose that the skin is to serve as an body organ of protection⁠—from injury, infection, UV radiation, and also moisture loss.

The skin creates a form of armor, a physical barrier to avoid pathogens native entering the body. In addition, sebum is slightly acidic, creating an setting that isn't best for harmful microbes.

But, if the skin is damaged (by a cut, scrape, burn, etc.) it create a chink in the armor permitting those pathogens access to the body. This can permit an epidemic to take it hold.

The subcutaneous layer particularly acts together a cushion to protect the more delicate bones and also musculature beneath.

The skin also protects the body from UV rays. As pointed out before, melanin acts as a kind of shield, blocking UV light so the cannot permeate farther than the top skin tissues. Sun exposure triggers the melanocytes to create more melanin, together the skin tries to protect itself indigenous further damage (in various other words, the skin tries to create a stronger shield). The creation of melanin is what reasons the skin come tan, and is one indication of sunlight damage.

The skin is also an essential to preventing excess water loss. The epidermis create a barrier that helps slow-moving down the evaporation that water, as well as prevents overfill water indigenous being absorbed into the skin while bathing or swimming.


The skin helps to maintain the body temperature within a very particular range.

When the body is obtaining too cool (hypothermia) the arrector chili muscles reason the hair to stand up, providing you goosebumps. The slim layer of wait trapped in between the hair and also the body acts together an insulator help to warmth the body.

The blood vessels in ~ the dermis also constrict, a procedure called vasoconstriction. Constricting the vessels at the skin's surface permits the skin to cool while preserving the warmed blood because that the body's core and an important organs.

When the human body is becoming too warm, the sudoriferous glands release sweat. Together the sweat evaporates, it cools the skin.

The blood vessels additionally play a role here in cooling the human body by dilating (vasodilation). The ship relax, allowing more blood to flow from the body's core, bringing warm with it. The warm then dissipates with the skin.

synthesis of Vitamin D

The skin is responsible for producing the majority of vitamin D that is required by the body. The skin has molecules referred to as 7-dehydrocholesterol. As soon as these molecules room hit by UVB beam of sunlight, they room converted into vitamin D3. Vitamin D3 is then converted into the active type of vitamin D with the kidneys.

Vitamin D additional are additionally an option.

connected Conditions

There space hundreds of problems that influence the skin, and also they have actually a wide variety of causes.

Birthmarks such together port-wine stains or hemangiomasMoles


Freckles and "age spots"

If you have a sore the doesn't heal or keeps recurring, a new skin mole or lesion, or a adjust in size, shape, or shade of an currently mole, girlfriend should have actually it evaluated by a health care provider.

Genetic conditions

Certain genetic conditions can reason the skin to not duty as the should. Most are fairly rare. They include:

Pidermolysis bullosa - A team of problems that causes extremely breakable skin which conveniently blisters or erodesHereditary ichthyosis - A condition that reasons an overgrowth of exceptionally dry, scaly skin


There are numerous tests that space performed on the skin to assist diagnose various conditions that can influence this organ.

There space three key techniques supplied to carry out a skin biopsy: punch, shave, and also excision.

Punch biopsy: A one cookie-cutter like tool is used to eliminate a tiny piece of skinShave biopsy: A blade or lance is used to shave off a piece of the skin surfaceExcisional biopsy: The whole lesion is removed

Patch test

Patch exam are typical done to help identify possible causes of call dermatitis. Adhesive spot with small pads impregnated with usual allergens are placed on the back and left for a duration of 48 hours. After the patches space removed, the skin is confirm for signs of irritation, redness, or swelling. This permits one to recognize the building materials that cause contact dermatitis.

Woods Lamp examination

A Woods lamp is a type of black light that allows a medical professional to detect points that aren't quickly seen through the naked eye.

During one exam, you will certainly sit in a dark room. The medical care provider stop a Woods desk lamp close to your skin come look for color changes. The presence of particular fungi or bacteria will appear in certain colors. The borders of hyperpigmentation or hypopigmentation are more easily viewed under a Woods lamp as well.

Skin Prick check

The skin prick test is a test the is perform on the skin, however isn"t offered to diagnose a skin condition. Instead, skin prick exam are used to recognize which substances a person may be allergy to. This consists of things that cause allergic rhinitis and also food allergies.

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Skin prick test are typically done top top the back or top top the arm. A device with small points, which have been dipped in allergen extracts, is used to prick or scrape the skin's surface. After ~ 15 come 20 minutes, the skin is examined. Any inflamed bump or wheals indicated a optimistic reaction.