Rochelle Collins, DO, is a board-certified family members medicine doctor at this time practicing in Bloomfield, Connecticut." data-inline-tooltip="true">Rochelle Collins, DO
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Verywell / Alexandra Gordon

Anatomy

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


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


The three significant layers of the skin every contain dedicated cells, tissues, and appendages, and also each performs distinct functions because that the body.

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Epidermis

The epidermis is the outermost class of the skin, the great of skin which is visible. The epidermis is additionally the thinnest that the three skin layers. The is an avascular skin layer, so that does no contain blood vessels.


This tough layer is chiefly comprised of keratin and also epithelial cells, stacked in tightly-packed sheets. That is in a state of consistent renewal, as brand-new skin cells are continuously created while larger cells are sloughed far in a process called desquamation.


Keratinocytes: The vast majority of the epidermis is comprised of keratinocytes. Keratinocytes space cells the manufacture keratin, the structural protein that provides up skin, hair, and also nails. Keratin is what forms the protective, water-resistant obstacle of the skin.Langerhans cells: this account for just a small number of cells in ~ the epidermis, yet have an essential function. Langerhan"s cell are dedicated cells that work with the immune system to protect the skin from international pathogens.Merkel cells: this touch receptor cells space most many in high tactile areas such together the fingertips, lips, and around the hair shaft. These cells secrete a chemical that relays information directly to the brain, allowing the skin to sense even the lightest touch.

The epidermis chin is consisted of of 4 layers, v some areas having a specialized fifth epidermal layer.


Keratinocytes go v radical alters as they travel from the deepest great of the epidermis whereby they space "born," to the top layer whereby they at some point slough away. The entire cell turnover process from cell birth to sloughing away takes, on average, about 28 days to complete.


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

Dermis

The dermis is the center layer the the skin. The dermis is the class that gives skin it's structure and elasticity.


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


The reticular layer is the more thickness of the 2 dermal layers. It is primarily made up of yarn of collagen and also elastin. This offers the dermis strength and allows it come stretch.


Sudoriferous glands: this are additionally known together sweat glands, of i beg your pardon there room two types—eccrine and apocrine. Eccrine glands space coiled glands which develop sweat and also are key in helping regulate body temperature. These glands additionally excrete small amounts of rubbish product such as urea, lactic and uric acid, ammonia. Apocrine are countless in the armpit and also groin area and aren"t active until puberty. The apocrine glands produce a kind of sweat the 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. When it contracts, it create a goosebump and also makes the hair was standing on end.Ceruminous glands: These devoted glands, only found in the dermis within the ear canal, create earwax.Lymph vesselsBlood vesselsSensory receptors

Subcutaneous great

The upper two layers that the skin sit atop the subcutaneous tissue. This layer is sometimes referred to as the hypodermis or panniculus.


This class is primarily made up of fat tissue called adipose tissue. This is whereby the human body reserves that is fat stores.


The subcutaneous great is likewise made up of loose connective tissue, bigger blood vessels, and nerves. This layer help connects the top skin to the musculature below.


This layer varies in thickness relying on where it's discovered on the human body (it's thickest top top the buttocks, palms, and feet) and age, sex, and also health of an individual.


Anatomical variations

Skin thickness different by age. The skin becomes progressively thicker until about age 40, as soon as it reverses that is course and slowly thins. These changes occur mainly in the dermis.


There is part indication the men, biologically, have overall thicker skin than women. some studies, though, have found no far-ranging difference in between the thickness of male versus woman skin.


Skin pigmentation likewise varies from individual to individual. Skin pigmentation is chiefly the result of melanin. While most human being have around the same variety of melanocytes, the lot of melanin produced by those melanocytes varies greatly. The an ext melanin the skin has, the darker the skin color. Carotene and hemoglobin also play a component in skin pigmentation, however to a lesser degree.


protection

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 create a kind of armor, a physical barrier to prevent pathogens from entering the body. In addition, sebum is contempt acidic, developing an environment that isn't best for harmful microbes.


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


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


The skin additionally protects the human body from UV rays. As discussed before, melanin acts as a kind of shield, prevent UV irradiate so it cannot penetrate farther than the top skin tissues. Sun exposure root cause the melanocytes come create more melanin, as the skin do the efforts to protect itself indigenous further damages (in various other words, the skin tries to create a more powerful shield). The creation of melanin is what causes the skin to tan, and also is one indication of sun damage.


The skin is also key to preventing excess water loss. The epidermis creates a obstacle that helps slow down the evaporation the water, as well as prevents excess water from being absorbed into the skin while bathing or swimming.


emotion

The plethora that nerve endings uncovered in the skin allows the person body come detect sensations of pressure, temperature, and pain. Sensory receptors are uncovered throughout the skin, space especially countless throughout the dermis.


When the human body is acquiring too cool (hypothermia) the arrector pili muscles reason the hair to was standing up, offering you goosebumps. The thin layer of waiting trapped between the hair and the human body acts as an insulator helping to warm the body.


The blood vessels in ~ the dermis also constrict, a process called vasoconstriction. Constricting the vessels at the skin's surface allows the skin come cool while maintaining the warmed blood for the body's main point and an important organs.


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


The blood vessels likewise play a duty here in cooling the human body by dilating (vasodilation). The vessels relax, allowing an ext blood to flow from the body's core, bringing heat with it. The warm then dissipates v the skin.


synthesis of Vitamin D

The skin is responsible for developing the bulk of vitamin D that is essential by the body. The skin has molecules called 7-dehydrocholesterol. Once these molecules space hit through UVB light ray of sunlight, they are converted into vitamin D3. Vitamin D3 is climate converted into the active kind of vitamin D with the kidneys.


The quantity of sun essential to get an sufficient amount the vitamin D varies widely and also is dependant top top a organize of different determinants including skin tone, season, ar (near the equator versus northern latitudes), time of day, and also the lot of skin the is exposed. It's suggested you monitor your medical care provider's recommendation for the right amount of sunlight exposure because that you.


linked Conditions

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


bright Skin Lesions

These are noncancerous growths that room common and also not harmful. (Although if you notification a brand-new growth, or alters in an currently one, friend should have actually it looked at by a practitioner.)


inflammation Rashes/Conditions

There is a huge array the inflammatory conditions that can impact the skin. Some room temporary, if others room chronic. Some may require therapy while others will heal on their own. They often resemble one another, for this reason it's constantly a great idea to obtain a diagnosis native a medical care provider.


Injuries

The skin is delicate to every sorts of injuries. In many cases, the skin is able come heal through it's remarkable, and also complex, process. Serious injuries should always be cure by a health care professional. Common skin injuries include:


Cutaneous epidemic

Infections deserve to take organize whenever there is a break in the skin barrier that enables microbes to pass through. Infection deserve to be led to by bacteria, viruses, or fungi. They include:


famous Infections

Many problems that don't originate in the skin can reason cutaneous symptoms. They include:


Pigmentation disorders

These room disorders that affect the way the skin to produce melanin. Pigmentation conditions can either cause boost in color (hyperpigmentation) or a loss of shade (hypopigmentation). Part pigmentation problems are treatable while others are not.


Cancer

Skin cancer is many often attached to too much sun exposure. Most creates of skin cancer are extremely treatable, but early detection is key.


If you have a sore that doesn't heal or keeps recurring, a new skin mole or lesion, or a change in size, shape, or color of an present mole, friend should have it evaluate by a healthcare provider.


Genetic problems

Certain genetic conditions can cause the skin to not role as the should. Most are relatively rare. Lock include:


Pidermolysis bullosa - A group of problems that causes extremely fragile skin which conveniently blisters or erodesHereditary ichthyosis - A problem that reasons an overgrowth of exceptionally dry, scaly skin

tests

There are several tests that space performed ~ above the skin to help diagnose various problems that can affect this organ.


Biopsy

A skin biopsy is a procedure in which cell or skin organization is removed for examination under a microscope. A biopsy is used to examine for skin cancer, infection, and to assist identify specific rashes.


Punch biopsy: A circular cookie-cutter favor tool is supplied to remove a small piece the skinShave biopsy: A blade or scalpel is offered to shave off a item of the skin surfaceExcisional biopsy: The whole lesion is removed

You will certainly be given a neighborhood anesthetic prior to the biopsy. Stitches might be offered to close the biopsy site in part cases.


Patch test

Patch test are common done to help identify feasible causes of contact dermatitis. Adhesive patches with small pads impregnated with typical allergens are put on the back and left because that a period of 48 hours. ~ the patches are removed, the skin is checked for indications of irritation, redness, or swelling. This enables one to understand the building material that trigger contact dermatitis.


Woods Lamp check

A Woods lamp is a kind of black light that permits a medical professional to detect points that aren't easily seen through the naked eye.


During an exam, you will sit in a dark room. The healthcare provider hold a Woods desk lamp close to your skin come look for color changes. The presence of details fungi or bacteria will appear in details colors. The borders of hyperpigmentation or hypopigmentation are more easily viewed under a Woods lamp as well.


Skin Prick check

The skin prick check is a test that is performed on the skin, however isn"t provided to diagnose a skin condition. Instead, skin prick exam are supplied to determine which substances a person may be allergic to. This has things that cause allergic rhinitis and also food allergies.


Skin prick exam are frequently done on the ago or on the arm. A maker with small points, which have been dipped in allergen extracts, is provided to prick or scratch the skin's surface. ~ 15 come 20 minutes, the skin is examined. Any inflamed bumps or wheals shown a confident reaction.


A Word native Verywell

For an body organ that is therefore visible and also familiar, the skin is how amazing complex. Together the largest organ that the human being body, the skin is responsible for plenty of important functions. There room hundreds of problems that can affect the skin; countless of them look incredibly comparable and are difficult to identify one indigenous another. If needed, view a medical care provider for help in diagnosing and treating your skin condition.

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