The integumentary system is an organ device consisting the the skin, hair, nails, and also exocrine glands. The skin is only a couple of millimeters thick however is by far the largest organ in the body. The median person’s skin weighs 10 pounds and also has a surface ar area of almost 20 square feet. Skin forms the body’s outer covering and also forms a barrier to defend the human body from chemicals, disease, UV light, and also physical damage. Hair and also nails extend from the skin to reinforce the skin and also protect it from environmental continue Scrolling come Read an ext Below...

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continued From Above... damage. The exocrine glands that the integumentary system develop sweat, oil, and also wax to cool, protect, and also moisturize the skin’s surface.

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Anatomy the the Integumentary System


The epidermis is the many superficial class of the skin that covers virtually the whole body surface. The epidermis rests upon and also protects the deeper and also thicker dermis great of the skin. Structurally, the epidermis is only around a tenth that a millimeter thick but is make of 40 come 50 rows of stack squamous epithelial cells. The epidermis is an avascular region of the body, definition that that does no contain any type of blood or blood vessels. The cell of the epidermis receive every one of their nutrients via diffusion that fluids native the dermis.

The epidermis is make of several devoted types of cells. Almost 90% that the epidermis is do of cells well-known as keratinocytes. Keratinocytes construct from stem cells at the basic of the epidermis and begin come produce and store the protein keratin. Keratin provides the keratinocytes really tough, scaly and water-resistant. At about 8% that epidermal cells, melanocytes form the 2nd most plenty of cell kind in the epidermis. Melanocytes produce the colours melanin to defend the skin indigenous ultraviolet radiation and sunburn. Langerhans cells room the third most common cells in the epidermis and make up just over 1% of every epidermal cells. Langerhans cells’ function is to detect and also fight pathogens that attempt to get in the body through the skin. Finally, Merkel cells comprise less than 1% of all epidermal cells yet have the important role of sensing touch. Merkel cells type a disk along the deepest edge of the epidermis wherein they connect to nerve end in the dermis to sense light touch.

In most of the body, the epidermis is arranged into 4 distinctive layers. In the palmar surface of the hands and plantar surface ar of the feet, the skin is thicker than in the rest of the body and there is a 5th layer of epidermis. The deepest region of the epidermis is the stratum basale, which consists of the stem cells that reproduce to form all that the various other cells of the epidermis. The cells of the stratum basale incorporate cuboidal keratinocytes, melanocytes, and also Merkel cells. Superficial to stratum basale is the stratum spinosum layer where Langerhans cells room found along with many rows of spiny keratinocytes. The spines found here room cellular projections called desmosomes that kind between keratinocytes to organize them together and also resist friction. Just superficial come the stratum spinosum is the stratum granulosum, wherein keratinocytes start to create waxy lamellar granules come waterproof the skin. The keratinocytes in the stratum granulosum are so far removed from the dermis the they begin to dice from absence of nutrients. In the special skin that the hands and feet, there is a great of skin superficial come the stratum granulosum well-known as the stratum lucidum. The stratum lucidum is made of several rows of clear, dead keratinocytes that safeguard the basic layers. The outermost class of skin is the stratum corneum. The stratum corneum is made of countless rows the flattened, dead keratinocytes that defend the underlying layers. Dead keratinocytes are constantly being shed from the surface of the stratum corneum and being replaced by cells arriving from the deeper layers.


The dermis is the deep class of the skin uncovered under the epidermis. The dermis is greatly made of thick irregular connective tissue along with nervous tissue, blood, and blood vessels. The dermis is lot thicker 보다 the epidermis and gives the skin its strength and also elasticity. In ~ the dermis there room two distinct regions: the papillary layer and the reticular layer.

The papillary great is the superficial layer of the dermis that boundaries on the epidermis. The papillary layer has many finger-like extensions referred to as dermal papillae the protrude superficially towards the epidermis. The dermal papillae rise the surface ar area that the dermis and contain numerous nerves and blood ship that space projected toward the surface ar of the skin. Blood flowing v the dermal papillae provide nutrients and also oxygen because that the cells of the epidermis. The nerves the the dermal papillae are used to feeling touch, pain, and also temperature through the cell of the epidermis.

The deeper great of the dermis, the reticular layer, is the thicker and also tougher component of the dermis. The reticular great is made of dense irregular connective tissue that includes many tough collagen and also stretchy elastin fibers running in all directions to provide strength and also elasticity to the skin. The reticular layer likewise contains blood ship to assistance the skin cells and nerve organization to feeling pressure and pain in the skin.


Deep to the dermis is a class of loose connective tissues recognized as the hypodermis, subcutis, or subcutaneous tissue. The hypodermis serves together the versatile connection in between the skin and the basic muscles and also bones and a fat storage area. Areolar connective organization in the hypodermis consists of elastin and also collagen yarn loosely i ordered it to enable the skin come stretch and also move separately of its basic structures. Fat adipose tissue in the hypodermis stores power in the form of triglycerides. Adipose additionally helps come insulate the body by trapping body heat developed by the underlying muscles.


Hair is an accessory organ of the skin made of columns of tightly pack dead keratinocytes discovered in many regions that the body. The few hairless components of the body include the palmar surface of the hands, plantar surface of the feet, lips, labia minora, and also glans penis. Hair help to defend the body from UV radiation by avoiding sunlight native striking the skin. Hair likewise insulates the human body by trapping heat air around the skin.

The structure of hair have the right to be damaged down into 3 major parts: the follicle, root, and also shaft. The hair follicle is a depression of epidermal cell deep into the dermis. Stem cell in the follicle blee to form the keratinocytes the eventually form the hair when melanocytes produce pigment that provides the hair the color. In ~ the follicle is the hair root, the section of the hair below the skin’s surface. Together the follicle produces brand-new hair, the cells in the root press up come the surface until they exit the skin. The hair shaft is composed of the part of the hair that is discovered outside of the skin.

The hair shaft and also root are made the 3 distinct layers the cells: the cuticle, cortex, and medulla. The cuticle is the outermost layer make of keratinocytes. The keratinocytes the the cuticle space stacked on height of each various other like shingles so the the external tip of each cell points away from the body. Under the cuticle space the cell of the cortex that type the majority of the hair’s width. The spindle-shaped and tightly packed cortex cell contain pigments that provide the hair that color. The innermost great of the hair, the medulla, is not existing in all hairs. Once present, the medulla usually contains highly pigmented cells full of keratin. As soon as the medulla is absent, the cortex proceeds through the middle of the hair.

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Nails are accessory offal of the skin do of sheets that hardened keratinocytes and also found top top the distal ends of the fingers and toes. Fingernails and toenails reinforce and protect the end of the digits and are offered for scraping and manipulating little objects. There space 3 main parts of a nail: the root, body, and complimentary edge. The nail root is the section of the nail uncovered under the surface ar of the skin. The nail body is the visible external part of the nail. The free edge is the distal end portion of the pond that has grown past the end of the finger or toe.

Nails thrive from a deep class of epidermal tissue well-known as the nail matrix, which surrounding the nail root. The stem cells of the nail matrix give birth to kind keratinocytes, which in turn develop keratin protein and pack into challenging sheets of hardened cells. The sheets of keratinocytes kind the hard nail source that progressively grows the end of the skin and forms the pond body as it will the skin’s surface. The cells of the nail root and also nail body are propelled toward the distal end of the finger or toe by new cells being created in the nail matrix. Under the nail body is a great of epidermis and also dermis known as the nail bed. The nail bed is pink in color due come the existence of capillaries that assistance the cell of the pond body. The proximal end of the nail near the root creates a whitish crescent shape well-known as the lunula where a little amount of pond matrix is visible v the pond body. Roughly the proximal and also lateral edge of the pond is the eponychium, a class of epithelium that overlaps and covers the leaf of the pond body. The eponychium help to seal the edges of the pond to stop infection that the underlying tissues.

Sudoriferous Glands

Sudoriferous glands are exocrine glands uncovered in the dermis the the skin and also commonly recognized as sweat glands. There are 2 major types the sudoriferous glands: eccrine sweat glands and apocrine sweat glands. Eccrine sweat glands are discovered in virtually every an ar of the skin and produce a cheap of water and sodium chloride. Eccrine sweat is ceded via a duct to the surface ar of the skin and is supplied to reduced the body’s temperature with evaporative cooling.

Apocrine sweat glands are found in mainly in the axillary and also pubic areas of the body. The ducts that apocrine sweat glands expand into the follicles of hair so that the sweat produced by these glands exit the body follow me the surface ar of the hair shaft. Apocrine sweat glands are inactive till puberty, at which point they produce a thick, oily liquid that is spend by bacteria life on the skin. The cradle of apocrine sweat by bacteria produces body odor.

Sebaceous Glands

Sebaceous glands space exocrine glands found in the dermis the the skin that create an oily secretion known as sebum. Sebaceous glands are uncovered in every component of the skin other than for the special skin of the palms of the hands and also soles that the feet. Sebum is produced in the sebaceous glands and carried v ducts come the surface of the skin or to hair follicles. Sebum acts to waterproof and increase the elasticity of the skin. Sebum likewise lubricates and also protects the cuticles that hairs as they pass with the follicles come the exterior the the body.

Ceruminous Glands

Ceruminous glands room special exocrine glands discovered only in the dermis that the ear canals. Ceruminous glands create a waxy secretion recognized as cerumen to safeguard the ear canals and lubricate the eardrum. Cerumen protects the ears by trapping foreign material such as dust and airborne pathogens that get in the ear canal. Cerumen is make continuously and slowly pushes larger cerumen outside toward the exterior the the ear canal wherein it drops out of the ear or is manually removed.

Physiology that the Integumentary System


Keratinization, also known as cornification, is the process of keratin accumulating within keratinocytes. Keratinocytes start their life together offspring the the stem cells of the stratum basale. Young keratinocytes have actually a cuboidal shape and also contain almost no keratin protein at all. As the stem cell multiply, they push older keratinocytes in the direction of the surface of the skin and also into the superficial layers of the epidermis. By the moment keratinocytes with the stratum spinosum, lock have begun to accumulate a significant amount that keratin and also have come to be harder, flatter, and much more water resistant. As the keratinocytes reach the stratum granulosum, lock have come to be much flatter and are almost completely filled v keratin. In ~ this suggest the cells space so far removed from the nutrient that diffuse indigenous the blood vessels in the dermis that the cell go with the procedure of apoptosis. Apoptosis is programmed cell fatality where the cell digests its own nucleus and organelles, leaving just a tough, keratin-filled shell behind. Dead keratinocytes moving right into the stratum lucidum and also stratum corneum are an extremely flat, hard, and tightly packed so as to kind a keratin obstacle to protect the underlying tissues.

Temperature Homeostasis

Being the body outermost organ, the skin is may be to regulate the body temperature by regulating how the human body interacts with its environment. In the instance of the human body entering a state the hyperthermia, the skin is may be to alleviate body temperature with sweating and vasodilation. Sweat developed by sudoriferous glands delivers water to the surface ar of the body whereby it starts to evaporate. The evaporation of sweat absorbs heat and also cools the body’s surface. Vasodilation is the procedure through i beg your pardon smooth muscle lining the blood ship in the dermis relax and also allow more blood to go into the skin. Blood transports warmth through the body, pulling heat away indigenous the body’s core and depositing it in the skin wherein it can radiate the end of the body and into the external environment.

In the case of the human body entering a state the hypothermia, the skin is able to raise human body temperature with the contraction of arrector chili muscles and through vasoconstriction. The follicles of hairs have tiny bundles that smooth muscle fastened to your base dubbed arrector pili muscles. The arrector pili form goose bump by contracting to relocate the hair follicle and also lifting the hair shaft upright from the surface ar of the skin. This movement results in an ext air gift trapped under the hairs to insulate the surface ar of the body. Vasoconstriction is the process of smooth muscle in the walls of blood ship in the dermis contracting to reduce the overwhelming of blood come the skin. Vasoconstriction patent the skin come cool when blood remains in the body’s core to maintain heat and also circulation in the an important organs.

Vitamin D Synthesis

Vitamin D, critical vitamin essential for the absorb of calcium from food, is produced by ultraviolet (UV) light striking the skin. The stratum basale and stratum spinosum class of the epidermis save on computer a sterol molecule well-known as 7-dehydrocholesterol. As soon as UV light current in sunshine or tanning bed lights strikes the skin, it penetrates with the outer layers that the epidermis and also strikes some of the molecule of 7-dehydrocholesterol, convert it right into vitamin D3. Vitamin D3 is convert in the kidneys right into calcitriol, the active form of vitamin D. When our skin is no exposed come sufficient quantities of sunlight, we can develop vitamin D deficiency, potentially bring about serious health concerns. The ability to order a vitamin D home test and also check our own levels thankfully renders it easier to recognize deficiency.


The skin gives protection to its underlying tissues from pathogens, mechanical damage, and also UV light. Pathogens, such as viruses and bacteria, space unable to enter the body through unbroken skin because of the outermost layers of epidermis comprise an unending it is provided of tough, dead keratinocytes. This protection describes the need of cleaning and covering cuts and also scrapes with bandages to prevent infection. Young mechanical damage from unstable or sharp objects is mostly absorbed by the skin before it can damage the basic tissues. Epidermal cells reproduce continually to quickly repair any kind of damage to the skin. Melanocytes in the epidermis produce the colours melanin, which absorbs UV light before it have the right to pass through the skin. UV irradiate can reason cells to become cancerous if not blocked native entering the body.

Skin Color

Human skin shade is regulated by the communication of 3 pigments: melanin, carotene, and hemoglobin. Melanin is a brown or black pigment developed by melanocytes to safeguard the skin from UV radiation. Melanin offers skin its tan or brown coloration and provides the color of brown or black hair. Melanin production boosts as the skin is exposed to higher levels the UV light bring about tanning of the skin. Carotene is another pigment existing in the skin the produces a yellow or orange actors to the skin and is many noticeable in civilization with short levels of melanin. Hemoglobin is another pigment many noticeable in world with tiny melanin. Hemoglobin is the red pigment uncovered in red blood cells, yet can be seen through the class of the skin together a irradiate red or pink color. Hemoglobin is many noticeable in skin coloration throughout times the vasodilation when the capillaries of the dermis are open up to carry much more blood come the skin’s surface.

Cutaneous Sensation

The skin enables the human body to feeling its external setting by picking up signals because that touch, pressure, vibration, temperature, and also pain. Merkel disks in the epidermis affix to nerve cells in the dermis to detect shapes and textures the objects contacting the skin. Corpuscles that touch are structures discovered in the dermal papillae that the dermis that likewise detect touch through objects contacting the skin. Lamellar corpuscles discovered deep in the dermis sense pressure and also vibration the the skin. Transparent the dermis there room many complimentary nerve endings that are merely neurons through their dendrites spread throughout the dermis. Totally free nerve endings may be sensitive to pain, warmth, or cold. The thickness of these sensory receptors in the skin varies throughout the body, resulting in some areas of the body being much more sensitive come touch, temperature, or ache than various other regions.

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In addition to secreting sweat come cool the body, eccrine sudoriferous glands of the skin additionally excrete waste products out of the body. Sweat developed by eccrine sudoriferous glands normally has mostly water with countless electrolytes and also a couple of other map chemicals. The most usual electrolytes uncovered in sweat room sodium and also chloride, however potassium, calcium, and magnesium ions may be excreted together well. When these electrolytes with high levels in the blood, their visibility in sweat also increases, help to reduce their visibility within the body. In addition to electrolytes, sweat contains and helps to excrete tiny amounts the metabolic waste assets such together lactic acid, urea, uric acid, and also ammonia. Finally, eccrine sudoriferous glands can assist to excrete alcohol native the human body of who who has been drink alcoholic beverages. Alcohol causes vasodilation in the dermis, leading to increased perspiration as more blood reaches sweat glands. The alcohol in the blood is absorbed by the cell of the sweat glands, leading to it to be excreted along with the other components of sweat.