The Skin (Human Anatomy): Picture, Definition, Function, and Skin Conditions The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone. The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands. The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue. The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis. Skin Conditions Rash : Nearly any change in the skin’s appearance can be called a rash. Most rashes are from simple skin irritation; others result from medical conditions. Dermatitis : A general term for inflammation of the skin. Atopic dermatitis (a type of eczema) is the most common form. Eczema : Skin inflammation (dermatitis) causing an itchy rash. Most often, it’s due to an overactive immune system. Psoriasis : An autoimmune condition that can cause a variety of skin rashes. Silver, scaly plaques on the skin are the most common form.

Dandruff : A scaly condition of the scalp may be caused by seborrheic dermatitis, psoriasis, or eczema. Acne : The most common skin condition, acne affects over 85% of people at some time in life. Cellulitis : Inflammation of the dermis and subcutaneous tissues, usually due to an infection. A red, warm, often painful skin rash generally results. Skin abscess (boil or furuncle): A localized skin infection creates a collection of pus under the skin. Some abscesses must be opened and drained by a doctor in order to be cured. Rosacea : A chronic skin condition causing a red rash on the face. Rosacea may look like acne, and is poorly understood. Warts : A virus infects the skin and causes the skin to grow excessively, creating a wart. Warts may be treated at home with chemicals, duct tape, or freezing, or removed by a physician. Melanoma : The most dangerous type of skin cancer, melanoma results from sun damage and other causes. A skin biopsy can identify melanoma. Basal cell carcinoma : The most common type of skin cancer.

Basal cell carcinoma is less dangerous than melanoma because it grows and spreads more slowly. Seborrheic keratosis : A benign, often itchy growth that appears like a “stuck-on” wart. Seborrheic keratoses may be removed by a physician, if bothersome. Actinic keratosis : A crusty or scaly bump that forms on sun-exposed skin. Actinic keratoses can sometimes progress to cancer. Squamous cell carcinoma : A common form of skin cancer, squamous cell carcinoma may begin as an ulcer that won’t heal, or an abnormal growth. It usually develops in sun-exposed areas. Herpes : The herpes viruses HSV-1 and HSV-2 can cause periodic blisters or skin irritation around the lips or the genitals. Hives : Raised, red, itchy patches on the skin that arise suddenly. Hives usually result from an allergic reaction. Tinea versicolor : A benign fungal skin infection creates pale areas of low pigmentation on the skin. Viral exantham : Many viral infections can cause a red rash affecting large areas of the skin. This is especially common in children.

Shingles (herpes zoster): Caused by the chickenpox virus, shingles is a painful rash on one side of the body. A new adult vaccine can prevent shingles in most people. Scabies : Tiny mites that burrow into the skin cause scabies. An intensely itchy rash in the webs of fingers, wrists, elbows, and buttocks is typical of scabies. Ringworm : A fungal skin infection (also called tinea). The characteristic rings it creates are not due to worms. Continued Skin Tests Skin biopsy : A piece of skin is removed and examined under a microscope to identify a skin condition. Skin testing (allergy testing): Extracts of common substances (such as pollen) are applied to the skin, and any allergic reactions are observed. Tuberculosis skin test (purified protein derivative or PPD): Proteins from the tuberculosis (TB) bacteria are injected under the skin. In someone who’s had TB, the skin becomes firm. Skin Treatments Corticosteroids (steroids): Medicines that reduce immune system activity may improve dermatitis. Topical steroids are most often used. Antibiotics : Medicines that can kill the bacteria causing cellulitis and other skin infections.

Antiviral drugs : Medicines can suppress the activity of the herpes virus, reducing symptoms. Antifungal drugs : Topical creams can cure most fungal skin infections. Occasionally, oral medicines may be needed. Antihistamines : Oral or topical medicines can block histamine, a substance that causes itching. Skin surgery : Most skin cancers must be removed by surgery. Immune modulators : Various drugs can modify the activity of the immune system, improving psoriasis or other forms of dermatitis. Skin moisturizers (emollients): Dry skin is more likely to become irritated and itchy. Moisturizers can reduce symptoms of many skin conditions. WebMD Image Collection Reviewed by Varnada Karriem-Norwood, MD on November 16, 2014 Sources BBC Science & Nature - Human Body and Mind - Organ Layer Location: All over your body Physical description: Flat, pliable and tough, between 0.5 and 4mm thick Function: To protect your body from damage, infection and drying out Largest organ Your skin is your largest organ. It covers your entire body and has a surface area of around 2 square metres.

Its thickness varies from 0.5mm on your eyelids to 4mm or more on the palms of your hands and the soles of your feet. In total, it accounts for around 16 percent of your body weight. Tough physical barrier Your skin consists of two main layers: the outer epidermis and the inner dermis. Cells in the deepest layer of your epidermis divide constantly to make new cells. The new cells are pushed towards the surface of your skin. They eventually die and become filled with keratin, an exceptionally tough protein. Keratin provides your body with a durable overcoat, which protects deeper cells from damage, infection and drying out. Cells on the surface of your skin rub and flake off steadily and are continuously replaced with new ones. About every 30 days, your body produces a totally new epidermis. Your inner dermis consists of strong collagen and elastic fibres pierced by blood vessels. It also contains touch, pressure and pain sensors and is packed with hair follicles, sweat and oil glands. The oil glands produce a lubricant that keeps your skin soft and prevents your hair from becoming brittle.

Temperature control Your skin's blood vessels, sweat glands and hairs play a crucial role in regulating your body temperature. When you need to cool down Your blood vessels widen and allow heat to escape through your skin You start sweating, and as your sweat dries, it uses heat from your skin and cools you down Your hairs lie flat to make sure little warm air doesn't get trapped between your skin and your hairs When you need to retain heat, the opposite happens â€“ your blood vessels narrow, you produce less sweat and your hairs stand up on end to trap warm air around your body. Skin colour Your skin contains specialised cells called melanocytes. They produce melanin, a brown substance, which absorbs some of the Sun's harmful ultraviolet rays. Fair-skinned people only have melanin in the lower layers of their epidermis. People with dark skin have larger amounts of melanin in all layers. Freckles and moles are nothing else but small patches of skin with more melanin than in the surrounding area. Wrinkles As you age, the number of collagen and elastic fibres in your dermis decreases. Additionally, you lose fat from the tissue under your skin. As a result, your skin becomes less elastic and begins to sag and wrinkle.

Human Skin Anatomy – Structure of Epidermis and Dermis Layers | Healthhype.com Home » Current Health Articles » Human Skin Anatomy – Structure of Epidermis and Dermis Layers Human Skin Anatomy – Structure of Epidermis and Dermis Layers Tweet The human skin and its related structures are known as the integumentary system. It is the largest organ in the body measuring 2 square meters in the average adult. Being the outermost structure, it is often the focus of much attention with a poor understanding of its anatomy and physiology. It can be considered as the most resilient organ in the human body as it is bombarded on a daily basis with a number of insults yet is able to withstand these attacks and continue functioning throughout life. Layers of the Human Skin The skin is composed of two layers, the outer epidermis and deeper dermis. There are two other layers worth noting, namely the basement membrane between the epidermis and dermis, and the hypodermis / subcutis beneath the dermis. These layers are often considered as part of the epidermis and dermis.

Picture from Wikimedia Commons The Epidermis The epidermis is the outermost layer of skin about 0.1 to 0.2 millimeters thick. It is made up of four types of cells : the keratinocytes which make up 90% of the epidermis, the Langerhans cells, melanocytes and Merkel cells which constitute the remaining 10% of the epidermis. Ask a Doctor Online Now! The keratinocytes, apart from being the most abundant of the epidermal cells, are also the most important in that it allows the skin to conduct its most basic function – protecting the internal environment of the body. It does this by manufacturing a number of proteins, mainly the different types of keratin, as well as lipids. As these cells emanate from the deepest layer of the epidermis known as the stratum basale (or stratum germinativum), it undergoes various stages of rearrangement and apoptosis (cell death).

By the time this process is complete, the outermost layer of the epidermis (stratum corneum) is made up of these dead highly-keratinized cells sealed by a layer of lipid and arranged in a manner that creates a firm, waterproof barrier. These gradual changes between the stratum basale and straum corneum contributes to the different arrangements seen as the five layers of the epidermis. This includes : Stratum basale (innermost) Stratum lucidum Stratum corneum (outermost) The epidermis has no blood supply of its own but receives oxygen and nutrients from the highly vascularized dermis. This travels across the basement membrane that anchors the stratum basale of the epidermis to the underlying dermis. The other types of epidermal cells also play important roles in the functioning of skin. Langerhan cells play an important role immune activity by exposing foreign antigens to lymphocytes. Melanocytes synthesize the pigment melanin which protects the skin against ultraviolet light. Merkel cells may play a role in the sense of touch although this has not been conclusively substantiated.

The Dermis The dermis is the deeper layer of the skin separated from the epidermis by the basement membrance. It is about 1 to 4 millimeters thick and contains a variety of cells which carry out many different functions. The dermis contains a vast network of nerve endings, blood vessels and connective tissue. The main type of cell found in the dermis is the fibroblast which produces various fibers like collagen and elastin. A number of different types of immune cells are also abundant in the dermis. Broadly, the dermis can be divided into two layers : the papillary dermis which lies superficially, the recticular dermis which lies deeper. The papillary dermis is so named because of the number of dermal papillae that extend into the epidermis. It is composed of loose connective tissue. The deeper and coarser reticular dermis is abundant in collagen, elastin and fibrin which gives skin its elasticity, firmness and strength.Various appendages of the integumentary system, like the hair, sweat glands and nails, are either rooted in the dermis or emanate from the dermis.

The hypodermis is not part of the skin but is often discussed in conjunction with the dermis. This layer anchors the dermis to underlying tissue and it contains a layer of fat (subcutaneous) to insulate the body. Skin Anatomy: Overview, Epidermis, Dermis Skin Anatomy Author: Bardia Amirlak, MD; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS more... Share Overview Overview The skin covers the entire external surface of the human body and is the principal site of interaction with the surrounding world. It serves as a protective barrier that prevents internal tissues from exposure to trauma, ultraviolet (UV) radiation, temperature extremes, toxins, and bacteria. Other important functions include sensory perception, immunologic surveillance, thermoregulation, and control of insensible fluid loss. The integument consists of 2 mutually dependent layers, the epidermis and dermis, which rest on a fatty subcutaneous layer, the panniculus adiposus.

(See the image below.) The epidermis is derived primarily from surface ectoderm but is colonized by pigment-containing melanocytes of neural crest origin, antigen-processing Langerhans cells of bone marrow origin, and pressure-sensing Merkel cells of neural crest origin. The dermis is derived primarily from mesoderm and contains collagen, elastic fibers, blood vessels, sensory structures, and fibroblasts. [ 1 ] Anatomy of the skin. View Media Gallery During the fourth week of embryologic development, the single cell thick ectoderm and underlying mesoderm begin to proliferate and differentiate. The specialized structures formed by the skin, including teeth, hair, hair follicles, fingernails, toenails, sebaceous glands, sweat glands, apocrine glands, and mammary glands also begin to appear during this period in development. Teeth, hair, and hair follicles are formed by the epidermis and dermis in concert, while fingernails and toenails are formed by the epidermis alone.

Hair follicles, sebaceous glands, sweat glands, apocrine glands, and mammary glands are considered epidermal glands or epidermal appendages, because they develop as downgrowths or diverticula of the epidermis into the dermis. [ 1 , 2 ] The definitive multi-layered skin is present at birth, but skin is a dynamic organ that undergoes continuous changes throughout life as outer layers are shed and replaced by inner layers. Skin also varies in thickness among anatomic location, sex, and age of the individual. This varying thickness primarily represents a difference in dermal thickness, as epidermal thickness is rather constant throughout life and from one anatomic location to another. Skin is thickest on the palms and soles of the feet (1.5 mm thick), while the thinnest skin is found on the eyelids and in the postauricular region (0.05 mm thick). Male skin is characteristically thicker than female skin in all anatomic locations. Children have relatively thin skin, which progressively thickens until the fourth or fifth decade of life when it begins to thin.

This thinning is also primarily a dermal change, with loss of elastic fibers, epithelial appendages, and ground substance. [ 3 ] Next: Epidermis The epidermis contains no blood vessels and is entirely dependent on the underlying dermis for nutrient delivery and waste disposal via diffusion through the dermoepidermal junction. The epidermis is a stratified, squamous epithelium that consists primarily of keratinocytes in progressive stages of differentiation from deeper to more superficial layers. The named layers of the epidermis include the stratum germinativum, stratum spinosum, stratum granulosum, and stratum corneum. Keratinocytes The stratum germinativum, or the basal layer, is immediately superficial to the dermoepidermal junction. This single cell layer of keratinocytes is attached to the basement membrane via hemidesmosomes. As keratinocytes divide and differentiate, they move from this deeper layer to the more superficial layers. Once they reach the stratum corneum, they are fully differentiated keratinocytes devoid of nuclei and are subsequently shed in the process of epidermal turnover.

Cells of the stratum corneum are the largest and most abundant of the epidermis. This layer ranges in thickness from 15-100 or more cells depending on anatomic location and is the primary protective barrier from the external environment. Melanocytes Melanocytes, derived from neural crest cells, primarily function to produce a pigment, melanin, which absorbs radiant energy from the sun and protects the skin from the harmful effects of UV radiation. Melanin accumulates in organelles termed melanosomes that are incorporated into dendrites anchoring the melanosome to the surrounding keratinocytes. Ultimately, the melanosomes are transferred via phagocytosis to the adjacent keratinocytes where they remain as granules. Melanocytes are found in the basal layer of the epidermis as well as in hair follicles, the retina, uveal tract, and leptomeninges. These cells are the sites of origin of melanoma . In areas exposed to the sun, the ratio of melanocytes to keratinocytes is approximately 1:4. In areas not exposed to solar radiation, the ratio may be as small as 1:30.

Absolute numbers of melanosomes are the same among the sexes and various races. Differing pigmentation among individuals is related to melanosome size rather than cell number. Sun exposure, melanocyte-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), estrogens, and progesterones stimulate melanin production. With aging, a decline is observed in the number of melanocytes populating the skin of an individual. Since these cells are of neural crest origin, they have no ability to reproduce. Langerhans cells Langerhans cells originate from the bone marrow and are found in the basal, spinous, and granular layers of the epidermis. They serve as antigen-presenting cells. They are capable of ingesting foreign antigens, processing them into small peptide fragments, binding them with major histocompatibility complexes, and subsequently presenting them to lymphocytes for activation of the immune system. An example of activation of this component of the immune system is contact hypersensitivity. Merkel cells Merkel cells, also derived from neural crest cells, are found on the volar aspect of digits, in nail beds, on the genitalia, and in other areas of the skin.

These cells are specialized in the perception of light touch. [ 1 , 3 ] Previous Next: Dermis The primary function of the dermis is to sustain and support the epidermis. The dermis is a more complex structure and is composed of 2 layers, the more superficial papillary dermis and the deeper reticular dermis. The papillary dermis is thinner, consisting of loose connective tissue containing capillaries, elastic fibers, reticular fibers, and some collagen. The reticular dermis consists of a thicker layer of dense connective tissue containing larger blood vessels, closely interlaced elastic fibers, and coarse bundles of collagen fibers arranged in layers parallel to the surface. The reticular layer also contains fibroblasts, mast cells, nerve endings, lymphatics, and epidermal appendages. Surrounding the components of the dermis is the gel-like ground substance, composed of mucopolysaccharides (primarily hyaluronic acid), chondroitin sulfates, and glycoproteins. The deep surface of the dermis is highly irregular and borders the subcutaneous layer, the panniculus adiposus, which additionally cushions the skin.

Fibroblasts The fibroblast is the major cell type of the dermis. These cells produce and secrete procollagen and elastic fibers. Procollagen is terminally cleaved by proteolytic enzymes into collagen that aggregates and becomes cross-linked. These tightly cross-linked collagen fibers provide tensile strength and resistance to shear and other mechanical forces. Collagen makes up 70% of the weight of the dermis, primarily Type I (85% of the total collagen) and Type III (15% of the total collagen). Elastic fibers constitute less than 1% of the weight of the dermis, but they play an enormous functional role by resisting deformational forces and returning the skin to its resting shape. [ 1 ] Previous Next: Dermoepidermal Junction The dermoepidermal junction is an undulating basement membrane that adheres the epidermis to the dermis. It is composed of 2 layers, the lamina lucida and lamina densa. The lamina lucida is thinner and lies directly beneath the basal layer of epidermal keratinocytes. The thicker lamina densa is in direct contact with the underlying dermis.

These structures are the target of immunologic injury in bullous pemphigoid and epidermolysis bullosa. Dermal papillae from the papillary dermis contain a plexus of capillaries and lymphatics oriented perpendicular to the skin surface. These fingerlike projections are surrounded by similar projections of the epidermis. This highly irregular junction greatly increases the surface area over which oxygen, nutrients, and waste products are exchanged between the dermis and the avascular epidermis. [ 1 ] Previous Next: Epidermal Appendages Epidermal appendages are intradermal epithelial structures lined with epithelial cells with the potential for division and differentiation. These are important as a source of epithelial cells, which accomplish reepithelialization should the overlying epidermis be removed or destroyed in situations such as partial thickness burns , abrasions, or split-thickness skin graft harvesting. Epidermal appendages include the following: Sebaceous glands Next: Cutaneous Blood Supply Cutaneous vessels ultimately arise from underlying named source vessels. Each source vessel supplies a 3-dimensional vascular territory from bone to skin termed an angiosome.

Adjacent angiosomes have vascular connections via reduced caliber (choke) vessels or similar caliber (true) anastomotic vessels. The cutaneous vessels originate either directly from the source arteries (septocutaneous or fasciocutaneous perforators) or as terminal branches of muscular vessels (musculocutaneous perforators). During their course to the skin, the cutaneous vessels travel within or adjacent to the connective tissue framework and supply branches to each tissue with which they come into close contact (bone, muscle, fascia, nerve, fat). They emerge from the deep fascia in the vicinity of the intermuscular or intramuscular septa or near tendons and travel toward the skin, where they form extensive subdermal and dermal plexuses. The dermis contains horizontally arranged superficial and deep plexuses, which are interconnected via communicating vessels oriented perpendicular to the skin surface. Cutaneous vessels ultimately anastomose with other cutaneous vessels to form a continuous vascular network within the skin. Clinically, this extensive horizontal network of vessels allows for random skin flap survival.

[ 6 , 7 , 8 ] Thermoregulation In addition to the skin's natural heat conductivity and loss of heat from the evaporation of sweat, convection from cutaneous vessels is a vital component of thermoregulation. Cutaneous blood flow is 10-20 times that required for essential oxygenation and metabolism, and large amounts of heat can be exchanged through the regulation of cutaneous blood flow. The thermoregulatory center in the hypothalamus controls vasoconstriction and vasodilatation of cutaneous vessels through the sympathetic nervous system. Previous Next: Lymphatics Skin lymphatics parallel the blood supply and function to conserve plasma proteins and scavenge foreign material, antigenic substances, and bacteria. Blind-ended lymphatic capillaries arise within the interstitial spaces of the dermal papillae. These unvalved, superficial dermal vessels drain into valved deep dermal and subdermal plexuses. These then coalesce to form larger lymphatic channels, which course through numerous filtering lymph nodes on their way to join the venous circulation near the subclavian vein – internal jugular vein junction bilaterally.

Previous Next: Skin Innervation Sensory perception is critically important in the avoidance of pressure, mechanical or traumatic forces, and extremes of temperature. Numerous specialized structures are present in the skin to detect various stimuli. As previously mentioned, Merkel cells of the epidermis detect light touch. Meissner corpuscles also detect light touch. These are found in the dermal papillae and are most concentrated in the fingertips. Pacini corpuscles are found deep within the dermis or even in the subcutaneous tissue. These structures are specialized to detect pressure. Pain is transmitted through naked nerve endings located in the basal layer of the epidermis. Krause bulbs detect cold, whereas Ruffini corpuscles detect heat. Heat, cold, and proprioception also are located in the superficial dermis. Cutaneous nerves follow the route of blood vessels to the skin. The area supplied by a single spinal nerve, or a single segment of the spinal cord, is termed a dermatome. Adjacent dermatomes may overlap considerably, which is important to note when performing field blocks with local anesthesia. [ 1 , 9 ] Previous Next: Surface Anatomy Lines and creases are evident over major and minor joints.

Skin contraction produces wrinkles and creases that lie perpendicular to the underlying muscular vector force. Relaxed skin tension lines (RSTL), however, are formed during relaxation and often follow a different direction than age and contracting wrinkles. (See the image below.) Relaxed skin tension lines are created by the natural tension on the skin from underlying structures. [ 10 ] Four main facial lines show the direction of relaxed skin tension lines. Contributor Information and Disclosures Author Bardia Amirlak, MD Assistant Professor of Plastic Surgery, Director of Residency Cosmetic Clinic, Director of Plastic Surgery Global Health Program, University of Texas Southwestern Medical Center at Dallas; Chief of Hand and Peripheral Nerve Surgery, Dallas Veterans Affairs Medical Center Bardia Amirlak, MD is a member of the following medical societies: American College of Surgeons , American Society of Plastic Surgeons , American Society of Reconstructive Transplantation , Kleinert Society Disclosure: Nothing to disclose. Coauthor(s) Ladan Shahabi, MD Clinical Assistant Professor, Department of Dermatology, New York University Ladan Shahabi, MD is a member of the following medical societies: American Academy of Dermatology , American Society for Dermatologic Surgery Disclosure: Nothing to disclose.

Specialty Editor Board Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference Disclosure: Received salary from Medscape for employment. for: Medscape. Wayne Karl Stadelmann, MD Stadelmann Plastic Surgery, PC Chief Editor Gregory Gary Caputy, MD, PhD, FICS Chief Surgeon, Aesthetica Gregory Gary Caputy, MD, PhD, FICS is a member of the following medical societies: American Society for Laser Medicine and Surgery , International College of Surgeons , International College of Surgeons US Section , Pan-Pacific Surgical Association, Wound Healing Society Disclosure: Nothing to disclose. Additional Contributors Shahin Javaheri, MD Chief, Department of Plastic Surgery, Martinez Veterans Affairs Outpatient Clinic; Consulting Staff, Advanced Aesthetic Plastic & Reconstructive Surgery Shahin Javaheri, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery , American Society of Plastic Surgeons Disclosure: Nothing to disclose.

Acknowledgements The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors Don R Revis Jr, MD, Michael Brent Seagle, MD, David J Rowe, MD, MS, Ashley C Campbell, Ali S Totonchi, MD, and Hooman Soltanian, MD, FACS, to the development and writing of this article. Integumentary System Integumentary System Home > Integumentary System Integumentary System The integumentary system is an organ system consisting of the skin, hair, nails, and exocrine glands. The skin is only a few millimeters thick yet is by far the largest organ in the body. The average person’s skin weighs 10 pounds and has a surface area of almost 20 square feet. Skin forms the body’s outer covering and forms a barrier to protect the body from chemicals, disease, UV light, and physical damage. Hair and nails extend from the skin to reinforce the skin and protect it from environmental...

Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Female Full Integumentary System Description [Continued from above] . . . damage. The exocrine glands of the integumentary system produce sweat, oil, and wax to cool, protect, and moisturize the skin’s surface. Anatomy of the Integumentary System Epidermis The epidermis is the most superficial layer of the skin that covers almost the entire body surface. The epidermis rests upon and protects the deeper and thicker dermis layer of the skin. Structurally, the epidermis is only about a tenth of a millimeter thick but is made of 40 to 50 rows of stacked squamous epithelial cells. The epidermis is an avascular region of the body, meaning that it does not contain any blood or blood vessels. The cells of the epidermis receive all of their nutrients via diffusion of fluids from the dermis . The epidermis is made of several specialized types of cells.

Almost 90% of the epidermis is made of cells known as keratinocytes. Keratinocytes develop from stem cells at the base of the epidermis and begin to produce and store the protein keratin. Keratin makes the keratinocytes very tough, scaly and water-resistant. At about 8% of epidermal cells, melanocytes form the second most numerous cell type in the epidermis. Melanocytes produce the pigment melanin to protect the skin from ultraviolet radiation and sunburn. Langerhans cells are the third most common cells in the epidermis and make up just over 1% of all epidermal cells. Langerhans cells’ role is to detect and fight pathogens that attempt to enter the body through the skin. Finally, Merkel cells make up less than 1% of all epidermal cells but have the important function of sensing touch. Merkel cells form a disk along the deepest edge of the epidermis where they connect to nerve endings in the dermis to sense light touch. The epidermis in most of the body is arranged into 4 distinct layers.

In the palmar surface of the hands and plantar surface of the feet, the skin is thicker than in the rest of the body and there is a fifth layer of epidermis. The deepest region of the epidermis is the stratum basale, which contains the stem cells that reproduce to form all of the other cells of the epidermis. The cells of the stratum basale include cuboidal keratinocytes, melanocytes, and Merkel cells. Superficial to stratum basale is the stratum spinosum layer where Langerhans cells are found along with many rows of spiny keratinocytes. The spines found here are cellular projections called desmosomes that form between keratinocytes to hold them together and resist friction. Just superficial to the stratum spinosum is the stratum granulosum, where keratinocytes begin to produce waxy lamellar granules to waterproof the skin. The keratinocytes in the stratum granulosum are so far removed from the dermis that they begin to die from lack of nutrients. In the thick skin of the hands and feet, there is a layer of skin superficial to the stratum granulosum known as the stratum lucidum.

The stratum lucidum is made of several rows of clear, dead keratinocytes that protect the underlying layers. The outermost layer of skin is the stratum corneum. The stratum corneum is made of many rows of flattened, dead keratinocytes that protect 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. Dermis The dermis is the deep layer of the skin found under the epidermis. The dermis is mostly made of dense irregular connective tissue along with nervous tissue, blood, and blood vessels. The dermis is much thicker than the epidermis and gives the skin its strength and elasticity. Within the dermis there are two distinct regions: the papillary layer and the reticular layer. The papillary layer is the superficial layer of the dermis that borders on the epidermis. The papillary layer contains many finger-like extensions called dermal papillae that protrude superficially towards the epidermis. The dermal papillae increase the surface area of the dermis and contain many nerves and blood vessels that are projected toward the surface of the skin.

Blood flowing through the dermal papillae provide nutrients and oxygen for the cells of the epidermis. The nerves of the dermal papillae are used to feel touch, pain, and temperature through the cells of the epidermis. The deeper layer of the dermis, the reticular layer, is the thicker and tougher part of the dermis. The reticular layer is made of dense irregular connective tissue that contains many tough collagen and stretchy elastin fibers running in all directions to provide strength and elasticity to the skin. The reticular layer also contains blood vessels to support the skin cells and nerve tissue to sense pressure and pain in the skin. Hypodermis Deep to the dermis is a layer of loose connective tissues known as the hypodermis, subcutis, or subcutaneous tissue. The hypodermis serves as the flexible connection between the skin and the underlying muscles and bones as well as a fat storage area. Areolar connective tissue in the hypodermis contains elastin and collagen fibers loosely arranged to allow the skin to stretch and move independently of its underlying structures. Fatty adipose tissue in the hypodermis stores energy in the form of triglycerides.

Adipose also helps to insulate the body by trapping body heat produced by the underlying muscles. Hair Hair is an accessory organ of the skin made of columns of tightly packed dead keratinocytes found in most regions of the body. The few hairless parts of the body include the palmar surface of the hands, plantar surface of the feet, lips , labia minora , and glans penis . Hair helps to protect the body from UV radiation by preventing sunlight from striking the skin. Hair also insulates the body by trapping warm air around the skin. The structure of hair can be broken down into 3 major parts: the follicle, root, and shaft. The hair follicle is a depression of epidermal cells deep into the dermis. Stem cells in the follicle reproduce to form the keratinocytes that eventually form the hair while melanocytes produce pigment that gives the hair its color. Within the follicle is the hair root, the portion of the hair below the skin’s surface. As the follicle produces new hair, the cells in the root push up to the surface until they exit the skin. The hair shaft consists of the part of the hair that is found outside of the skin.

The hair shaft and root are made of 3 distinct layers of cells: the cuticle, cortex, and medulla. The cuticle is the outermost layer made of keratinocytes. The keratinocytes of the cuticle are stacked on top of each other like shingles so that the outer tip of each cell points away from the body. Under the cuticle are the cells of the cortex that form the majority of the hair’s width. The spindle-shaped and tightly packed cortex cells contain pigments that give the hair its color. The innermost layer of the hair, the medulla, is not present in all hairs. When present, the medulla usually contains highly pigmented cells full of keratin. When the medulla is absent, the cortex continues through the middle of the hair. Nails Nails are accessory organs of the skin made of sheets of hardened keratinocytes and found on the distal ends of the fingers and toes. Fingernails and toenails reinforce and protect the end of the digits and are used for scraping and manipulating small objects. There are 3 main parts of a nail: the root, body, and free edge. The nail root is the portion of the nail found under the surface of the skin.

The nail body is the visible external portion of the nail. The free edge is the distal end portion of the nail that has grown beyond the end of the finger or toe. Nails grow from a deep layer of epidermal tissue known as the nail matrix, which surrounds the nail root. The stem cells of the nail matrix reproduce to form keratinocytes, which in turn produce keratin protein and pack into tough sheets of hardened cells. The sheets of keratinocytes form the hard nail root that slowly grows out of the skin and forms the nail body as it reaches the skin’s surface. The cells of the nail root and nail body are pushed toward the distal end of the finger or toe by new cells being formed in the nail matrix. Under the nail body is a layer of epidermis and dermis known as the nail bed. The nail bed is pink in color due to the presence of capillaries that support the cells of the nail body. The proximal end of the nail near the root forms a whitish crescent shape known as the lunula where a small amount of nail matrix is visible through the nail body.

Around the proximal and lateral edges of the nail is the eponychium , a layer of epithelium that overlaps and covers the edge of the nail body. The eponychium helps to seal the edges of the nail to prevent infection of the underlying tissues. Sudoriferous Glands Sudoriferous glands are exocrine glands found in the dermis of the skin and commonly known as sweat glands. There are 2 major types of sudoriferous glands: eccrine sweat glands and apocrine sweat glands. Eccrine sweat glands are found in almost every region of the skin and produce a secretion of water and sodium chloride. Eccrine sweat is delivered via a duct to the surface of the skin and is used to lower the body’s temperature through evaporative cooling. Apocrine sweat glands are found in mainly in the axillary and pubic regions of the body. The ducts of apocrine sweat glands extend into the follicles of hairs so that the sweat produced by these glands exits the body along the surface of the hair shaft. Apocrine sweat glands are inactive until puberty, at which point they produce a thick, oily liquid that is consumed by bacteria living on the skin.

The digestion of apocrine sweat by bacteria produces body odor. Sebaceous Glands Sebaceous glands are exocrine glands found in the dermis of the skin that produce an oily secretion known as sebum. Sebaceous glands are found in every part of the skin except for the thick skin of the palms of the hands and soles of the feet. Sebum is produced in the sebaceous glands and carried through ducts to the surface of the skin or to hair follicles. Sebum acts to waterproof and increase the elasticity of the skin. Sebum also lubricates and protects the cuticles of hairs as they pass through the follicles to the exterior of the body. Ceruminous Glands Ceruminous glands are special exocrine glands found only in the dermis of the ear canals. Ceruminous glands produce a waxy secretion known as cerumen to protect the ear canals and lubricate the eardrum . Cerumen protects the ears by trapping foreign material such as dust and airborne pathogens that enter the ear canal . Cerumen is made continuously and slowly pushes older cerumen outward toward the exterior of the ear canal where it falls out of the ear or is manually removed.

Physiology of the Integumentary System Keratinization Keratinization, also known as cornification, is the process of keratin accumulating within keratinocytes. Keratinocytes begin their life as offspring of the stem cells of the stratum basale. Young keratinocytes have a cuboidal shape and contain almost no keratin protein at all. As the stem cells multiply, they push older keratinocytes towards the surface of the skin and into the superficial layers of the epidermis. By the time keratinocytes reach the stratum spinosum, they have begun to accumulate a significant amount of keratin and have become harder, flatter, and more water resistant. As the keratinocytes reach the stratum granulosum, they have become much flatter and are almost completely filled with keratin. At this point the cells are so far removed from the nutrients that diffuse from the blood vessels in the dermis that the cells go through the process of apoptosis. Apoptosis is programmed cell death where the cell digests its own nucleus and organelles, leaving only a tough, keratin-filled shell behind.

Dead keratinocytes moving into the stratum lucidum and stratum corneum are very flat, hard, and tightly packed so as to form a keratin barrier to protect the underlying tissues. Temperature Homeostasis Being the body’s outermost organ, the skin is able to regulate the body’s temperature by controlling how the body interacts with its environment. In the case of the body entering a state of hyperthermia, the skin is able to reduce body temperature through sweating and vasodilation. Sweat produced by sudoriferous glands delivers water to the surface of the body where it begins to evaporate. The evaporation of sweat absorbs heat and cools the body’s surface. Vasodilation is the process through which smooth muscle lining the blood vessels in the dermis relax and allow more blood to enter the skin. Blood transports heat through the body, pulling heat away from the body’s core and depositing it in the skin where it can radiate out of the body and into the external environment. In the case of the body entering a state of hypothermia, the skin is able to raise body temperature through the contraction of arrector pili muscles and through vasoconstriction.

The follicles of hairs have small bundles of smooth muscle attached to their base called arrector pili muscles. The arrector pili form goose bumps by contracting to move the hair follicle and lifting the hair shaft upright from the surface of the skin. This movement results in more air being trapped under the hairs to insulate the surface of the body. Vasoconstriction is the process of smooth muscles in the walls of blood vessels in the dermis contracting to reduce the flood of blood to the skin. Vasoconstriction permits the skin to cool while blood stays in the body’s core to maintain heat and circulation in the vital organs. Vitamin D Synthesis Vitamin D, an essential vitamin necessary for the absorption of calcium from food, is produced by ultraviolet (UV) light striking the skin. The stratum basale and stratum spinosum layers of the epidermis contain a sterol molecule known as 7-dehydrocholesterol. When UV light present in sunlight or tanning bed lights strikes the skin, it penetrates through the outer layers of the epidermis and strikes some of the molecules of 7-dehydrocholesterol, converting it into vitamin D3.

Vitamin D3 is converted in the kidneys into calcitriol, the active form of vitamin D. Protection The skin provides protection to its underlying tissues from pathogens, mechanical damage, and UV light. Pathogens, such as viruses and bacteria, are unable to enter the body through unbroken skin due to the outermost layers of epidermis containing an unending supply of tough, dead keratinocytes. This protection explains the necessity of cleaning and covering cuts and scrapes with bandages to prevent infection. Minor mechanical damage from rough or sharp objects is mostly absorbed by the skin before it can damage the underlying tissues. Epidermal cells reproduce constantly to quickly repair any damage to the skin. Melanocytes in the epidermis produce the pigment melanin, which absorbs UV light before it can pass through the skin. UV light can cause cells to become cancerous if not blocked from entering the body. Skin Color Human skin color is controlled by the interaction of 3 pigments: melanin, carotene, and hemoglobin. Melanin is a brown or black pigment produced by melanocytes to protect the skin from UV radiation. Melanin gives skin its tan or brown coloration and provides the color of brown or black hair.

Melanin production increases as the skin is exposed to higher levels of UV light resulting in tanning of the skin. Carotene is another pigment present in the skin that produces a yellow or orange cast to the skin and is most noticeable in people with low levels of melanin. Hemoglobin is another pigment most noticeable in people with little melanin. Hemoglobin is the red pigment found in red blood cells, but can be seen through the layers of the skin as a light red or pink color. Hemoglobin is most noticeable in skin coloration during times of vasodilation when the capillaries of the dermis are open to carry more blood to the skin’s surface. Cutaneous Sensation The skin allows the body to sense its external environment by picking up signals for touch, pressure, vibration, temperature, and pain. Merkel disks in the epidermis connect to nerve cells in the dermis to detect shapes and textures of objects contacting the skin. Corpuscles of touch are structures found in the dermal papillae of the dermis that also detect touch by objects contacting the skin. Lamellar corpuscles found deep in the dermis sense pressure and vibration of the skin.

Throughout the dermis there are many free nerve endings that are simply neurons with their dendrites spread throughout the dermis. Free nerve endings may be sensitive to pain, warmth, or cold. The density of these sensory receptors in the skin varies throughout the body, resulting in some regions of the body being more sensitive to touch, temperature, or pain than other regions. Excretion In addition to secreting sweat to cool the body, eccrine sudoriferous glands of the skin also excrete waste products out of the body. Sweat produced by eccrine sudoriferous glands normally contains mostly water with many electrolytes and a few other trace chemicals. The most common electrolytes found in sweat are sodium and chloride, but potassium, calcium, and magnesium ions may be excreted as well. When these electrolytes reach high levels in the blood, their presence in sweat also increases, helping to reduce their presence within the body. In addition to electrolytes, sweat contains and helps to excrete small amounts of metabolic waste products such as lactic acid, urea, uric acid, and ammonia. Finally, eccrine sudoriferous glands can help to excrete alcohol from the body of someone who has been drinking 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 cells of the sweat glands, causing it to be excreted along with the other components of sweat. Prepared by Tim Taylor, Anatomy and Physiology Instructor Skin structure Skin structure Skin - Skin Structure “Skin is the largest organ in the human body. Skin has a surface area of 1.6 m2 and comprises 16% of the total body weight.” Skin is the most important organ in human body. Basic function of skin is integument of the body that protects internal organs and also performs many other functions for body. Because it interfaces with the environment (UV, temperature, moisture, dust, air pollution and so on), skin plays key role in reading information that is essential to the survival immediately and responding appropriately to protect the body. There is an additional function that the skin protects itself from the external harm. Human skin is divided into 3 main layers: epidermis, dermis, subcutaneous tissue from the outermost layer and also it has some affiliated organs include hair, sebaceous glands, sweat glands, capillary, etc.

Epidermis is the thinnest layer of the skin. It is responsible for moisturization and protection of the skin. The epidermis organically consists of keratinocytes, the cells making protein keratin and melanocytes, the cells producing melanin which is the pigment responsible for skin tone and color. The epidermis is subdivided into several layers (from deepest to most superficial layer): stratum basale, stratum spinosum, stratum granulosum and stratum corneum. Keratinocytes undergo cell division (via mitosis). The newly formed cells move up the strata (stratum spinosum and stratum granulosum) over changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer and compose stratum corneum. This process is called keratinization. The stratum corneum is the outmost layer of the epidermis, consisting of dead cells (anucleate cells). It is comprises only 15-20 flattened cell layers. Because it consists of dead cells, its importance didn占쏙옙t be recognized in the past.

According to the recent studies, the stratum corneum is not only piled with dead cells, but also it is performing a variety of roles. The stratum corneum damage can lead to many kinds of skin problem and skin diseases. In order to maintain healthy skin, it is necessary to correctly understand about stratum corneum and recognize the importance of skin care. Keratinized layers (stratum corneum) slough off from the skin after a certain period of time, and newly created keratinized layers will come out. This process is called desquamation or turnover. This process is regarded as a defense. Through this progress, unnecessary materials are prevented to remain in the epidermis and discharged from the skin. Turnover takes repeated cycle of roughly 4-6 weeks. Our skin is not retained after once formed, but as a dynamic organ it always repeats the process of production, desquamation and production. If horny generation and shedding period abnormal, there are several kinds of problems can be occurred. Most skin diseases accompanied by abnormal stratum corneum.

The dermis comprises the matrix of typical proteins which are collagen (which plays an important role in providing skin strength) and elastin (which plays an important role in providing skin elasticity). The dermis also contains capillaries, nerves, mastocyto (which involved in allergic reactions) and many natural moisturizing factors (NMF) like Na-PCA and hyaluronic acid (what have an important feature for moisturizing). The hypodermis (Subcutaneous tissue) consists mainly of adipocytes. This layer is responsible for providing nutrition for epidermis and dermis, supporting the skin structure, absorbing shock, maintaining body temperature and protecting underlying cells from mechanical trauma. Your Skin Your Skin Tu piel Quick! What's the body's biggest organ? You might be surprised to find out it's the skin, which you might not think of as an organ. No matter how you think of it, your skin is very important. It covers and protects everything inside your body. Without skin, people's muscles, bones, and organs would be hanging out all over the place. Skin holds everything together.

It also: protects our bodies helps keep our bodies at just the right temperature allows us to have the sense of touch Don't Miss Your Epidermis The skin is made up of three layers, each with its own important parts. The layer on the outside is called the epidermis (say: eh-pih-DUR-mis). The epidermis is the part of your skin you can see. Look down at your hands for a minute. Even though you can't see anything happening, your epidermis is hard at work. At the bottom of the epidermis, new skin cells are forming. When the cells are ready, they start moving toward the top of your epidermis. This trip takes about 2 weeks to a month. As newer cells continue to move up, older cells near the top die and rise to the surface of your skin. What you see on your hands (and everywhere else on your body) are really dead skin cells. continue Bye-Bye Skin Cells These old cells are tough and strong, just right for covering your body and protecting it. But they only stick around for a little while. Soon, they'll flake off.

Though you can't see it happening, every minute of the day we lose about 30,000 to 40,000 dead skin cells off the surface of our skin. So just in the time it took you to read this far, you've probably lost about 40,000 cells. That's almost 9 pounds (4 kilograms) of cells every year! But don't think your skin might wear out someday. Your epidermis is always making new skin cells that rise to the top to replace the old ones. Most of the cells in your epidermis (95%) work to make new skin cells. And what about the other 5%? They make a substance called melanin (say: MEL-uh-nun). Melanin gives skin its color. The darker your skin is, the more melanin you have. When you go out into the sun , these cells make extra melanin to protect you from getting burned by the sun's ultraviolet, or UV, rays. That's why your skin gets tan if you spend a lot of time in the sun. But even though melanin is mighty, it can't shield you all by itself.

You'll want to wear sunscreen and protective clothing, such as a hat, to prevent painful sunburns. Protecting your skin now also can help prevent skin cancer when you get older. The Dermis Is Under the Epidermis The next layer down is the dermis (say: DUR-mis). You can't see your dermis because it's hidden under your epidermis. The dermis contains nerve endings, blood vessels, oil glands, and sweat glands. It also contains collagen and elastin, which are tough and stretchy. The nerve endings in your dermis tell you how things feel when you touch them. They work with your brain and nervous system, so that your brain gets the message about what you're touching. Is it the soft fur of a cat or the rough surface of your skateboard? Sometimes what you feel is dangerous, so the nerve endings work with your muscles to keep you from getting hurt. If you touch something hot, the nerve endings in your dermis respond right away: "Ouch! That's hot!" The nerves quickly send this message to the brain or spinal cord, which then immediately commands the muscles to take your hand away. This all happens in a split second, without you ever thinking about it.

previous continue Dermis = Lots of Blood Vessels Your dermis is also full of tiny blood vessels. These keep your skin cells healthy by bringing them the oxygen and nutrients they need and by taking away waste. These blood vessels are hard to see in kids, but you might get a better look if you check out your grandparents' skin. As the dermis gets older, it gets thinner and easier to see through. The dermis is home to the oil glands, too. These are also called sebaceous (say: sih-BAY-shus) glands, and they are always producing sebum (say: SEE-bum). Sebum is your skin's own natural oil. It rises to the surface of your epidermis to keep your skin lubricated and protected. It also makes your skin waterproof — as long as sebum's on the scene, your skin won't absorb water and get soggy. You also have sweat glands on your epidermis. Even though you can't feel it, you actually sweat a tiny bit all the time. The sweat comes up through pores, tiny holes in the skin that allow it to escape. When the sebum meets the sweat, they form a protective film that's a bit sticky.

An easy way to see this film in action is to pick up a pin with your fingers. Then wash your hands well with soap and water and dry them off completely. Now try to pick up that pin again. It won't be so easy because your sticky layer is gone! Don't worry — it will be back soon, as your sebaceous and sweat glands create more sticky stuff. The Third Layer Is Subcutaneous Fat The third and bottom layer of the skin is called the subcutaneous (say: sub-kyoo-TAY-nee-us) layer. It is made mostly of fat and helps your body stay warm and absorb shocks, like if you bang into something or fall down. The subcutaneous layer also helps hold your skin to all the tissues underneath it. This layer is where you'll find the start of hair, too. Each hair on your body grows out of a tiny tube in the skin called a follicle (say: FAHL-ih-kul). Every follicle has its roots way down in the subcutaneous layer and continues up through the dermis. You have hair follicles all over your body, except on your lips, the palms of your hands, and the soles of your feet.

And you have more hair follicles in some places than in others — there are more than 100,000 follicles on your head alone! Your hair follicles rely on your sebaceous glands to bring on the shine. Connected to each follicle in the dermis layer is a tiny sebaceous gland that releases sebum onto the hair. This lightly coats the hair with oil, giving it some shine and a little waterproofing. previous continue Skin Can Warm and Cool You Your skin can help if you're feeling too hot or too cold. Your blood vessels, hair, and sweat glands cooperate to keep your body at just the right temperature. If you were to run around in the heat, you could get overheated. If you play outside when it's cold, your inner temperature could drop. Either way, your skin can help. Your body is pretty smart. It knows how to keep your temperature right around 98.6°F (37°C) to keep you and your cells healthy. Your skin can respond to messages sent out by your hypothalamus (say: hy-po-THAL-uh-mus), the brain's inner thermometer.

If you've been running around on a hot day, your blood vessels get the signal from the hypothalamus to release some of your body's heat. They do this by bringing warm blood closer to the surface of your skin. That's why you sometimes get a red face when you run around. To cool you down, sweat glands also swing into action by making lots of sweat to release body heat into the air. The hotter you are, the more sweat your glands make! Once the sweat hits the air, it evaporates (this means that it changes from a liquid to a vapor) off your skin, and you cool down. What about when you're ice-skating or sledding? When you're cold, your blood vessels keep your body from losing heat by narrowing as much as possible and keeping the warm blood away from the skin's surface. You might notice tiny bumps on your skin. Most kids call these goosebumps , but the fancy name for them is the pilomotor (say: PY-lo-mo-ter) reflex. The reflex makes special tiny muscles called the erector pili (say: ee-REK-tur pee-LEE) muscles pull on your hairs so they stand up very straight. Keep It Clean!

Unlike other organs (like your lungs, heart, and brain), your skin likes a good washing . When you wash your skin, use water and a mild soap. And don't forget to cover scrapes and cuts with gauze or a bandage. This keeps the dirt out and helps prevent infections. It's just one way to be kind to the skin you're in! dermis | anatomy | Britannica.com anatomy ligament Dermis, also called corium, the thicker, deeper layer of the skin underlying the epidermis and made up of connective tissue . It is present in varying degrees of development among various vertebrate groups, being relatively thin and simple in aquatic animals and progressively thicker and more complex in terrestrial species. The dermis from its earliest evolutionary appearance has been a depository of bone , as expressed in dermal armour (primitive fishes), scales (fishes and certain amphibians), and plates (crocodile, lizard, turtle, armadillo). The fin rays of fishes are dermal derivatives, as are many types of pigment cells. The dermis of mammals is of greater thickness relative to the epidermis than is that of other vertebrates, partly because it contains abundant collagenous connective tissue.

When treated with tannic acid, the dermis becomes leather . In humans the dermis projects into the overlying epidermis in ridges called papillae (see video). Nerves that extend through the dermis and end in the papillae are sensitive to heat , cold, pain, and pressure. Sweat glands and oil glands lie in the deeper stratum reticulare , as do the bases of hair follicles, the nail beds, and blood and lymph vessels. Dermal anatomy. in animal development: The epidermis and its outgrowths The epidermis is only the superficial layer of the skin, which is reinforced by the dermis, a connective tissue layer of a much greater thickness. The cells of the dermis are derived from mesoderm and neural-crest cells. In particular the pigment cells found in the dermis of fishes, amphibians, and reptiles are of neural-crest origin. The pigment in the skin of birds and mammals (and also in... in prenatal development: Integumentary system ...superficial cells and downy hairs mingle with a greasy glandular secretion and smear the skin in the late fetal months; the pasty mass is called vernix caseosa.

The deep layer of the skin, or dermis, is a fibrous anchoring bed differentiated from mesoderm. In the later fetal months the plane of union between epidermis and dermis becomes wavy. The permanently ridged patterns are notable at... 7 References found in Britannica Articles Assorted References Corrections? Updates? Help us improve this article! Contact our editors with your feedback. MEDIA FOR: You have successfully emailed this. Error when sending the email. Try again later. Edit Mode Submit Tips For Editing We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind. Encyclopædia Britannica articles are written in a neutral objective tone for a general audience. You may find it helpful to search within the site to see how similar or related subjects are covered. Any text you add should be original, not copied from other sources. At the bottom of the article, feel free to list any sources that support your changes, so that we can fully understand their context. (Internet URLs are the best.) Your contribution may be further edited by our staff, and its publication is subject to our final approval.

Unfortunately, our editorial approach may not be able to accommodate all contributions. Submit Thank You for Your Contribution! Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Uh Oh There was a problem with your submission. Please try again later. Close Date Published: April 07, 1999 URL: Access Date: January 18, 2017 Share Exercise 7: The Integumentary System Flashcards | Easy Notecards _____________ granules extruded from the keratinocytes prevent water loss by diffusion through the epidermis laminated fibers in the dermis are produced by ______________. fibroblasts glands that respond to rising androgen levels are the ____________________ glands. sebaceous and apocrine glands phagocytic cells that occupy the epidermis are called _____________________________. epidermal dendritic or langerhans cells 20 a unique touch receptor formed from a stratum basale cell and a nerve fiber is a __________________.

tactile or Merkel disc What layer is present in the thick skin but not in thin skin? stratum lucidum What cell-to-cell structure holds the cells of the stratum spinosum tightly together? desmosomes 23 What substance is manufactured in the skin that plays a role in calcium absorption elsewhere in the body? vitamin D3 24 List the sensory receptors found in the dermis of the skin: free nerve endings for pain, temperature, messiners corpuscles for touch in the hairless skin, pacinian corpuscles for pressure 25 A nurse tells a doctor that a patient is cyanotic. Define cyanotic. A blue cast to the skin 26 What does cyanotic presence imply? Inadequate oxygenation of the blood 27 What is a bedsore (decubitus ulcer)? localized area of tissue necrosis and death 28 Why do ulcers occur?

pressure areas point of increased pressure over bony areas restrict the blood supply to the area 29 Produces an accumulation of oily material that is known as a blackhead sebaceous glands Tiny muscles, attached to hair folicles, that pull the hair upright during fright or cold arrector pili Perspiration glands with a role in temperature control sweat gland---eccrine Sheath formed of both epithelial and connective tissues hair follicle Less numerous type of perspiration-prouducing gland; found mainly in the pubic and axillary regions sweat gland--apocrine Found everywhere on the body except the palms of hands and soles of the feet sebaceous glands With what substance in the bond paper does the iodine painted on the skin react? The starch Based on class data, which skin area--the forearm or palm of hand--has more sweat glands? Palm 43 Which other body areas would if tested prove to have a high density of sweat glands? Face and Axillae What organ system controls the activity of the eccrine sweat glands? Nervous system 45 Why can fignerprints be used to identify individuals? The pattern of your epidermal ridges is unique and does not change during your lifetime.

Everyones fingerprint was made different, therefore this is a useful way for people to identify one another. 46 Name the three common fingerprint patterns: Loops, Arches and Whorls

Question: Which organ of the human body comprises the dermis and epidermis?
Answer: Skin