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8.5: Functions of the Integumentary System - Biology

8.5: Functions of the Integumentary System - Biology


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Learning Objectives

  • Describe the different functions of the skin and the structures that enable them
  • Explain how the skin helps maintain body temperature

The skin and accessory structures perform a variety of essential functions, such as protecting the body from invasion by microorganisms, chemicals, and other environmental factors; preventing dehydration; acting as a sensory organ; modulating body temperature and electrolyte balance; and synthesizing vitamin D. The underlying hypodermis has important roles in storing fats, forming a “cushion” over underlying structures, and providing insulation from cold temperatures.

Protection

The skin protects the rest of the body from the basic elements of nature such as wind, water, and UV sunlight. It acts as a protective barrier against water loss, due to the presence of layers of keratin and glycolipids in the stratum corneum. It also is the first line of defense against abrasive activity due to contact with grit, microbes, or harmful chemicals. Sweat excreted from sweat glands deters microbes from over-colonizing the skin surface by generating dermicidin, which has antibiotic properties.

Try It

The word “armor” evokes several images. You might think of a Roman centurion or a medieval knight in a suit of armor. The skin, in its own way, functions as a form of armor—body armor. It provides a barrier between your vital, life-sustaining organs and the influence of outside elements that could potentially damage them.

For any form of armor, a breach in the protective barrier poses a danger. The skin can be breached when a child skins a knee or an adult has blood drawn—one is accidental and the other medically necessary. However, you also breach this barrier when you choose to “accessorize” your skin with a tattoo or body piercing. Because the needles involved in producing body art and piercings must penetrate the skin, there are dangers associated with the practice. These include allergic reactions; skin infections; blood-borne diseases, such as tetanus, hepatitis C, and hepatitis D; and the growth of scar tissue. Despite the risk, the practice of piercing the skin for decorative purposes has become increasingly popular. According to the American Academy of Dermatology, 24 percent of people from ages 18 to 50 have a tattoo.

Tattooing has a long history, dating back thousands of years ago. The dyes used in tattooing typically derive from metals. A person with tattoos should be cautious when having a magnetic resonance imaging (MRI) scan because an MRI machine uses powerful magnets to create images of the soft tissues of the body, which could react with the metals contained in the tattoo dyes. Read this article to learn more about tattooing.

Sensory Function

The fact that you can feel an ant crawling on your skin, allowing you to flick it off before it bites, is because the skin, and especially the hairs projecting from hair follicles in the skin, can sense changes in the environment. The hair root plexus surrounding the base of the hair follicle senses a disturbance, and then transmits the information to the central nervous system (brain and spinal cord), which can then respond by activating the skeletal muscles of your eyes to see the ant and the skeletal muscles of the body to act against the ant.

The skin acts as a sense organ because the epidermis, dermis, and the hypodermis contain specialized sensory nerve structures that detect touch, surface temperature, and pain. These receptors are more concentrated on the tips of the fingers, which are most sensitive to touch, especially the Meissner corpuscle (tactile corpuscle) (Figure 1), which responds to light touch, and the Pacinian corpuscle (lamellated corpuscle), which responds to vibration. Merkel cells, seen scattered in the stratum basale, are also touch receptors. In addition to these specialized receptors, there are sensory nerves connected to each hair follicle, pain and temperature receptors scattered throughout the skin, and motor nerves innervate the arrector pili muscles and glands. This rich innervation helps us sense our environment and react accordingly.

Thermoregulation

The integumentary system helps regulate body temperature through its tight association with the sympathetic nervous system, the division of the nervous system involved in our fight-or-flight responses. The sympathetic nervous system is continuously monitoring body temperature and initiating appropriate motor responses. Recall that sweat glands, accessory structures to the skin, secrete water, salt, and other substances to cool the body when it becomes warm. Even when the body does not appear to be noticeably sweating, approximately 500 mL of sweat (insensible perspiration) are secreted a day. If the body becomes excessively warm due to high temperatures, vigorous activity (Figure 2), or a combination of the two, sweat glands will be stimulated by the sympathetic nervous system to produce large amounts of sweat, as much as 0.7 to 1.5 L per hour for an active person. When the sweat evaporates from the skin surface, the body is cooled as body heat is dissipated.

In addition to sweating, arterioles in the dermis dilate so that excess heat carried by the blood can dissipate through the skin and into the surrounding environment (Figure 2). This accounts for the skin redness that many people experience when exercising.

When body temperatures drop, the arterioles constrict to minimize heat loss, particularly in the ends of the digits and tip of the nose. This reduced circulation can result in the skin taking on a whitish hue. Although the temperature of the skin drops as a result, passive heat loss is prevented, and internal organs and structures remain warm. If the temperature of the skin drops too much (such as environmental temperatures below freezing), the conservation of body core heat can result in the skin actually freezing, a condition called frostbite.

Try It

All systems in the body accumulate subtle and some not-so-subtle changes as a person ages. Among these changes are reductions in cell division, metabolic activity, blood circulation, hormonal levels, and muscle strength (Figure 3). In the skin, these changes are reflected in decreased mitosis in the stratum basale, leading to a thinner epidermis. The dermis, which is responsible for the elasticity and resilience of the skin, exhibits a reduced ability to regenerate, which leads to slower wound healing. The hypodermis, with its fat stores, loses structure due to the reduction and redistribution of fat, which in turn contributes to the thinning and sagging of skin.

The accessory structures also have lowered activity, generating thinner hair and nails, and reduced amounts of sebum and sweat. A reduced sweating ability can cause some elderly to be intolerant to extreme heat. Other cells in the skin, such as melanocytes and dendritic cells, also become less active, leading to a paler skin tone and lowered immunity. Wrinkling of the skin occurs due to breakdown of its structure, which results from decreased collagen and elastin production in the dermis, weakening of muscles lying under the skin, and the inability of the skin to retain adequate moisture.

Many anti-aging products can be found in stores today. In general, these products try to rehydrate the skin and thereby fill out the wrinkles, and some stimulate skin growth using hormones and growth factors. Additionally, invasive techniques include collagen injections to plump the tissue and injections of BOTOX® (the name brand of the botulinum neurotoxin) that paralyze the muscles that crease the skin and cause wrinkling.

Vitamin D Synthesis

The epidermal layer of human skin synthesizes vitamin D when exposed to UV radiation. In the presence of sunlight, a form of vitamin D3 called cholecalciferol is synthesized from a derivative of the steroid cholesterol in the skin. The liver converts cholecalciferol to calcidiol, which is then converted to calcitriol (the active chemical form of the vitamin) in the kidneys. Vitamin D is essential for normal absorption of calcium and phosphorous, which are required for healthy bones. The absence of sun exposure can lead to a lack of vitamin D in the body, leading to a condition called rickets, a painful condition in children where the bones are misshapen due to a lack of calcium, causing bowleggedness. Elderly individuals who suffer from vitamin D deficiency can develop a condition called osteomalacia, a softening of the bones. In present day society, vitamin D is added as a supplement to many foods, including milk and orange juice, compensating for the need for sun exposure.

In addition to its essential role in bone health, vitamin D is essential for general immunity against bacterial, viral, and fungal infections. Recent studies are also finding a link between insufficient vitamin D and cancer.


8.5: Functions of the Integumentary System - Biology

The skin and accessory structures perform a variety of essential functions, such as protecting the body from invasion by microorganisms, chemicals, and other environmental factors preventing dehydration acting as a sensory organ modulating body temperature and electrolyte balance and synthesizing vitamin D. The underlying hypodermis has important roles in storing fats, forming a “cushion” over underlying structures, and providing insulation from cold temperatures.


Protection

The skin protects the rest of the body from the basic elements of nature such as wind, water, and UV sunlight. It acts as a protective barrier against water loss, due to the presence of layers of keratin and glycolipids in the stratum corneum. It also is the first line of defense against abrasive activity due to contact with grit, microbes, or harmful chemicals. Sweat excreted from sweat glands deters microbes from over-colonizing the skin surface by generating dermicidin, which has antibiotic properties.

Everyday Connection: Tattoos and Piercings

The word “armor” evokes several images. You might think of a Roman centurion or a medieval knight in a suit of armor. The skin, in its own way, functions as a form of armor—body armor. It provides a barrier between your vital, life-sustaining organs and the influence of outside elements that could potentially damage them.

For any form of armor, a breach in the protective barrier poses a danger. The skin can be breached when a child skins a knee or an adult has blood drawn—one is accidental and the other medically necessary. However, you also breach this barrier when you choose to “accessorize” your skin with a tattoo or body piercing. Because the needles involved in producing body art and piercings must penetrate the skin, there are dangers associated with the practice. These include allergic reactions skin infections blood-borne diseases, such as tetanus, hepatitis C, and hepatitis D and the growth of scar tissue. Despite the risk, the practice of piercing the skin for decorative purposes has become increasingly popular. According to the American Academy of Dermatology, 24 percent of people from ages 18 to 50 have a tattoo.


Thermoregulation

The integumentary system helps regulate body temperature through its tight association with the sympathetic nervous system, the division of the nervous system involved in our fight-or-flight responses. The sympathetic nervous system is continuously monitoring body temperature and initiating appropriate motor responses. Recall that sweat glands, accessory structures to the skin, secrete water, salt, and other substances to cool the body when it becomes warm. Even when the body does not appear to be noticeably sweating, approximately 500 mL of sweat (insensible perspiration) are secreted a day. If the body becomes excessively warm due to high temperatures, vigorous activity (Figure 4.16ac), or a combination of the two, sweat glands will be stimulated by the sympathetic nervous system to produce large amounts of sweat, as much as 0.7 to 1.5 L per hour for an active person. When the sweat evaporates from the skin surface, the body is cooled as body heat is dissipated.

In addition to sweating, arterioles in the dermis dilate so that excess heat carried by the blood can dissipate through the skin and into the surrounding environment (Figure 4.16b). This accounts for the skin redness that many people experience when exercising.

When body temperatures drop, the arterioles constrict to minimize heat loss, particularly in the ends of the digits and tip of the nose. This reduced circulation can result in the skin taking on a whitish hue. Although the temperature of the skin drops as a result, passive heat loss is prevented, and internal organs and structures remain warm. If the temperature of the skin drops too much (such as environmental temperatures below freezing), the conservation of body core heat can result in the skin actually freezing, a condition called frostbite.


5.3 Functions of the Integumentary System

The skin and accessory structures perform a variety of essential functions, such as protecting the body from invasion by microorganisms, chemicals, and other environmental factors preventing dehydration acting as a sensory organ modulating body temperature and electrolyte balance and synthesizing vitamin D. The underlying hypodermis has important roles in storing fats, forming a “cushion” over underlying structures, and providing insulation from cold temperatures.

Protection

The skin protects the rest of the body from the basic elements of nature such as wind, water, and UV sunlight. It acts as a protective barrier against water loss, due to the presence of layers of keratin and glycolipids in the stratum corneum. It also is the first line of defense against abrasive activity due to contact with grit, microbes, or harmful chemicals. Sweat excreted from sweat glands deters microbes from over-colonizing the skin surface by generating dermicidin, which has antibiotic properties.

Everyday Connection

Tattoos and Piercings

The word “armor” evokes several images. You might think of a Roman centurion or a medieval knight in a suit of armor. The skin, in its own way, functions as a form of armor—body armor. It provides a barrier between your vital, life-sustaining organs and the influence of outside elements that could potentially damage them.

For any form of armor, a breach in the protective barrier poses a danger. The skin can be breached when a child skins a knee or an adult has blood drawn—one is accidental and the other medically necessary. However, you also breach this barrier when you choose to “accessorize” your skin with a tattoo or body piercing. Because the needles involved in producing body art and piercings must penetrate the skin, there are dangers associated with the practice. These include allergic reactions skin infections blood-borne diseases, such as tetanus, hepatitis C, and hepatitis D and the growth of scar tissue. Despite the risk, the practice of piercing the skin for decorative purposes has become increasingly popular. According to the American Academy of Dermatology, 24 percent of people from ages 18 to 50 have a tattoo.

Interactive Link

Tattooing has a long history, dating back thousands of years ago. The dyes used in tattooing typically derive from metals. A person with tattoos should be cautious when having a magnetic resonance imaging (MRI) scan because an MRI machine uses powerful magnets to create images of the soft tissues of the body, which could react with the metals contained in the tattoo dyes. Watch this video to learn more about tattooing.

Sensory Function

The fact that you can feel an ant crawling on your skin, allowing you to flick it off before it bites, is because the skin, and especially the hairs projecting from hair follicles in the skin, can sense changes in the environment. The hair root plexus surrounding the base of the hair follicle senses a disturbance, and then transmits the information to the central nervous system (brain and spinal cord), which can then respond by activating the skeletal muscles of your eyes to see the ant and the skeletal muscles of the body to act against the ant.

The skin acts as a sense organ because the epidermis, dermis, and the hypodermis contain specialized sensory nerve structures that detect touch, surface temperature, and pain. These receptors are more concentrated on the tips of the fingers, which are most sensitive to touch, especially the Meissner corpuscle (tactile corpuscle) (Figure 5.15), which responds to light touch, and the Pacinian corpuscle (lamellated corpuscle), which responds to vibration. Merkel cells, seen scattered in the stratum basale, are also touch receptors. In addition to these specialized receptors, there are sensory nerves connected to each hair follicle, pain and temperature receptors scattered throughout the skin, and motor nerves innervate the arrector pili muscles and glands. This rich innervation helps us sense our environment and react accordingly.

Thermoregulation

The integumentary system helps regulate body temperature through its tight association with the sympathetic nervous system, the division of the nervous system involved in our fight-or-flight responses. The sympathetic nervous system is continuously monitoring body temperature and initiating appropriate motor responses. Recall that sweat glands, accessory structures to the skin, secrete water, salt, and other substances to cool the body when it becomes warm. Even when the body does not appear to be noticeably sweating, approximately 500 mL of sweat (insensible perspiration) are secreted a day. If the body becomes excessively warm due to high temperatures, vigorous activity (Figure 5.16ac), or a combination of the two, sweat glands will be stimulated by the sympathetic nervous system to produce large amounts of sweat, as much as 0.7 to 1.5 L per hour for an active person. When the sweat evaporates from the skin surface, the body is cooled as body heat is dissipated.

In addition to sweating, arterioles in the dermis dilate so that excess heat carried by the blood can dissipate through the skin and into the surrounding environment (Figure 5.16b). This accounts for the skin redness that many people experience when exercising.

When body temperatures drop, the arterioles constrict to minimize heat loss, particularly in the ends of the digits and tip of the nose. This reduced circulation can result in the skin taking on a whitish hue. Although the temperature of the skin drops as a result, passive heat loss is prevented, and internal organs and structures remain warm. If the temperature of the skin drops too much (such as environmental temperatures below freezing), the conservation of body core heat can result in the skin actually freezing, a condition called frostbite.

Aging and the.

Integumentary System

All systems in the body accumulate subtle and some not-so-subtle changes as a person ages. Among these changes are reductions in cell division, metabolic activity, blood circulation, hormonal levels, and muscle strength (Figure 5.17). In the skin, these changes are reflected in decreased mitosis in the stratum basale, leading to a thinner epidermis. The dermis, which is responsible for the elasticity and resilience of the skin, exhibits a reduced ability to regenerate, which leads to slower wound healing. The hypodermis, with its fat stores, loses structure due to the reduction and redistribution of fat, which in turn contributes to the thinning and sagging of skin.

The accessory structures also have lowered activity, generating thinner hair and nails, and reduced amounts of sebum and sweat. A reduced sweating ability can cause some elderly to be intolerant to extreme heat. Other cells in the skin, such as melanocytes and dendritic cells, also become less active, leading to a paler skin tone and lowered immunity. Wrinkling of the skin occurs due to breakdown of its structure, which results from decreased collagen and elastin production in the dermis, weakening of muscles lying under the skin, and the inability of the skin to retain adequate moisture.

Many anti-aging products can be found in stores today. In general, these products try to rehydrate the skin and thereby fill out the wrinkles, and some stimulate skin growth using hormones and growth factors. Additionally, invasive techniques include collagen injections to plump the tissue and injections of BOTOX ® (the name brand of the botulinum neurotoxin) that paralyze the muscles that crease the skin and cause wrinkling.

Vitamin D Synthesis

The epidermal layer of human skin synthesizes vitamin D when exposed to UV radiation. In the presence of sunlight, a form of vitamin D3 called cholecalciferol is synthesized from a derivative of the steroid cholesterol in the skin. The liver converts cholecalciferol to calcidiol, which is then converted to calcitriol (the active chemical form of the vitamin) in the kidneys. Vitamin D is essential for normal absorption of calcium and phosphorous, which are required for healthy bones. The absence of sun exposure can lead to a lack of vitamin D in the body, leading to a condition called rickets , a painful condition in children where the bones are misshapen due to a lack of calcium, causing bowleggedness. Elderly individuals who suffer from vitamin D deficiency can develop a condition called osteomalacia, a softening of the bones. In present day society, vitamin D is added as a supplement to many foods, including milk and orange juice, compensating for the need for sun exposure.

In addition to its essential role in bone health, vitamin D is essential for general immunity against bacterial, viral, and fungal infections. Recent studies are also finding a link between insufficient vitamin D and cancer.


8.5: Functions of the Integumentary System - Biology

The integument as an organ: The integument as an organ, and is an alternative name for skin. The integumentary system includes the skin and the skin derivatives hair, nails, and glands. The integument is the body’s largest organ and accounts for 15% of body weight.

The derivatives of the integument:

Hair: functions include protection & sensing light touch.
Hair is composed of columns of dead, keratinized cells bound together by extracellular proteins. Hair has two main sections: The shaft- superficial portion that extends out of the skin and the root- portion that penetrates into the dermis. Surrounding the root of the hair is the hair follicle. At the base of the hair follicle is an onion-shaped structure called the bulb Papilla of the hair and the matrix within the bulb produce new hair.

Nails: participate in the grasp & handling of small things.
Nails are plates of tightly packed, hard, keratinized epidermal cells.

  • nail root: -the portion of the nail under the skin,
  • nail body: -the visible pink portion of the nail, the white crescent at the base of the nail is the lunula, the hyponychium secures the nail to the finger, the cuticle or eponychium is a narrow band around the proximal edge of the nail and
  • free edge: -the white end that may extend past the finger.
  • Sebaceous - Oil glands. Located in the dermis, and secrete sebum.
  • Sudoriferous - Sweat glands. Divided into two main types:
    • Eccrine - Most common, main function is regulation of body temperature by evaporation, and
    • Apocrine - Responsible for “cold sweat” associated with stress.
    • Thermoregulation - Evaporation of sweat & Regulation of blood flow to the dermis.
      Cutaneous sensation - Sensations like touch, pressure, vibration, pain, warmth or coolness.
    • Vitamin D production - UV sunlight & precursor molecule in skin make vitamin D.
    • Protection – The sin acts as a physical barrier.
    • Absorption & secretion – The skin is involved in the absorption of water-soluble molecules and excretion of water and sweat.
    • Wound healing - When a minor burn or abrasion occurs basal cells of the epidermis break away from the basement membrane and migrate across the wound. They migrate as a sheet, when the sides meet the growth stops and this is called ‘contact inhibition’.
    • In deep wound healing - A clot forms in the wound, blood flow increases and many cells move to the wound. The clot becomes a scab granulation tissue fills the wound and intense growth of epithelial cells beneath the scab. The scab falls off and the skin returns to normal thickness.

    Epidermis – The Epidermis is the thinner more superficial layer of the skin.
    The epidermis is made up of 4 cell types:

    • (A) Keratinocytes – Produce keratin protein a fibrous protein that helps protect the epidermis
    • (B) Melanocytes - produces the brown pigment melanin
    • (C) Langerhan Cells – participate in immune response and
    • (D) Merkel cells - participates in the sense of touch.
    1. Stratum corneum: the outermost layer, made of 25-30 layers of dead flat keratinocytes. Lamellar granules provide water repellent action and are continuously shed & replaced.
    2. Stratum lucidum: Only found in the fingertips, palms of hands, & soles of feet. This layer is made up of 3-5 layers of flat dead keratinocytes.
    3. Stratum granulosum: made up of 3-5 layers of keratinocytes, site of keratin formation, keratohyalin gives the granular appearance.
    4. Stratum spinosum: appears covered in thornlike spikes, provide strength & flexibility to the skin.
    5. Stratum basale: The deepest layer, made up of a single layer of cuboidal or columnar cells. Cells produced here are constantly divide & move up to apical surface.

    Dermis: is the deeper, thicker layer composed of connective tissue, blood vessels, nerves, glands and hair follicles.

    • The epidermis contains 3 cell types:
      • Adipocytes,
      • Macrophages and
      • Fibroblasts.
      • Papillary region - The superficial layer of the dermis, made up of loose areolar connective tissue with elastic fibers.
      • Dermal papillae - Fingerlike structures invade the epidermis, contain capillaries or Meissner corpuscles which respond to touch.

      This tutorial describes the integumentary system including the skin, hair, nails and glands. The two layers of the skin and their functions are also discussed.

      The integument is an organ that is involved in protection and barrier function. The integument is also involved in regulating body heat and blood pressure.

      Specific Tutorial Features:

      • Step by step description of the various layers of the epidermis and the dermis.
      • The relationship between the various layers of skin and the hair, nails and glands are discussed.
      • Concept map showing inter-connections of new concepts in this tutorial and those previously introduced.
      • Definition slides introduce terms as they are needed.
      • Visual representation of concepts
      • Examples given throughout to illustrate how the concepts apply.
      • A concise summary is given at the conclusion of the tutorial.

      The integument as an organ:

      • The two layers of the integument (skin)
      • The derivatives of the integument
        • Hair
        • Nails
        • Glands
        • Thermoregulation
        • Cutaneous sensation
        • Vitamin D production
        • Protection
        • Absorption & secretion
          Wound healing

        See all 24 lessons in Anatomy and Physiology, including concept tutorials, problem drills and cheat sheets: Teach Yourself Anatomy and Physiology Visually in 24 Hours


        8.5: Functions of the Integumentary System - Biology

        This article covers the medical terminology of the integumentary system. These terms will help with your study of conditions and diseases related to the skin, hair, and nails. You can use this list in your studies.

        You will find a list of word roots, and a few additional suffixes and prefixes related to the integumentary system. There will be terms related to those medical specialties that deal with the skin.

        There is also a list of integumentary structures, and procedures. Finally, there is a list of some diseases and conditions related to the integumentary system.

        If you need a background on how medical terms are formed, read the article on Medical Terminology Basics . Also, the article 11 Rules for Changing Singular Terms to Plural Terms is a good article for the use of singular and plural endings. And, as always, there is a review of suffixes and prefixes that can be used with any system.

        Review of Prefixes

        This section contains prefixes that are used for the medical terminology of most systems.

        Prefixes are used at the beginning of a word to modify or vary the meaning of the word. When the prefixes are detached from a term, it is followed by a hyphen (-).

        PrefixesDefinition
        a-, an-no, not, without, away
        aut-self
        brady- slow
        dia-apart, through
        end-, endo-within, inside
        exo-outside of, without
        epi- above
        hyper- excessive
        hypo- insufficient
        inter- between
        intra- middle
        media-medium
        medial-situated or pertaining to the middle
        medi-middle
        medio-within
        normo- normal
        per- through
        peri- around
        physio-, physi-related to nature or physiology
        poly- many
        pro-before, for, in front of, from, in behalf of, on account of
        re-back, again
        retro-behind, back, backward
        sub-under, below, beneath, in small quantity, less than normal
        syn-, sy-, syl-, sym-union or association
        tachy- fast
        trans- across, through, beyond, over
        ultra- excess

        Review of Suffixes

        Below are some suffixes that can be used for the medical terminology of most systems. Suffixes are placed at the end of a word root or word part to modify or vary the meaning.

        Suffixes can indicate a condition, disease or a procedure. When a suffix is written detached it is preceded by a hyphen (-).

        SuffixesDefinition
        -ac. -al, -ar, -aryPertaining to
        -icPertaining to, characteristics
        -ose, -ousPertaining to
        -tic Pertaining to
        -centesissurgical puncture as to aspirate or remove fluid
        -cision process of cutting
        -ectomyexcision (surgical removal or cutting out)
        -grama drawing or a written record
        -graphproduct of a drawing, writing or recording
        -graphythe process of recording
        -ia condition
        -ism condition process, theory of, principle, method
        -itis inflammation
        -ologist one who studies
        -ologystudy of
        -lysisprocess of loosening, freeing, or destroying
        -opsyto view
        -osiscondition, status process
        -otomycutting into
        -ostomyformation of an opening
        -plasty surgical repair
        -pathy disease
        -sclerosis hardening
        -scope instrument for viewing
        -scopyvisual examination with a lighted instrument
        -sisstate of, condition
        -stasis to stand, place, stop, control
        -stenosisnarrowing
        -tension pressure
        -therapytreatment
        -thoracicchest
        -ule small

        Word Root and Combining Vowel for the Integumentary System

        This is a list of word roots with their combining vowel used for the integumentary system.

        Word RootDefinition
        Carcin(o)cancer
        Cutane(o)skin
        Cyan(o)blue
        Dermat(o)skin
        Derm(o)skin
        Erythr(o)red
        Kerat(o)horny
        Lip(o)fat
        Melan(o)black or melanin
        Onych(o)nail
        Seb(o)sebum, oil
        Sud(o)sweat
        Trich(o)hair
        Ungu(o)nail
        Vesic(o)bladder or blister

        Integumentary Specific Suffixes and Prefixes

        Term Definition
        Carcin-cancer
        Cryo-, cry-cold
        Cut- skin
        Cyan-blue
        Cyst-pouch or bladder
        -cytecell
        -dermskin
        Dermat, dermaskin
        Epi-on or upon
        Epiderm-, epidermo-epidermis
        Fiss-cleft or split
        Kerat-horny
        Melan-,mel-black
        -omatumor
        Photo-light
        -rrheafluid discharge or flow
        Seb-sebum
        Strati-layer

        Integumentary Specialties

        This is a list of the specialists that diagnose and treat conditions related to the integumentary system.

        Term Definition
        DermatologyDerm(o) means skin
        -logy means the study of.
        A division of medicine that diagnoses and treat conditions of the skin, hair, and nails.
        DermatologistDerm(o) means skin
        -logist means one who studies.
        A physician specializing in the treatment of the skin and accessory structures.
        Plastic SurgeryA branch of medicine that treats conditions of the integumentary system
        Plastic SurgeonA physician that repairs, improves and reconstructs damaged body structures.

        The Structure and Functions of the Integumentary System

        The integumentary system protects the body against pathogens, regulates body temperature, provides sensory input and synthesizes vitamin D.

        The components of the integumentary system consist of the skin, hair, and nails. Below is a list of structures and functions of the integumentary system.

        Term Definition
        Apocrine sweat glandThe apocrine glands are a dermal sudoriferous (sweat) gland that secretes at the groin, armpits and anal region.
        CuticleCuticula means little skin.
        The cuticle is the sheath of the hair follicle.
        Also, the fold of tissue that covers the nail root.
        DermisDerm- means skin.
        The dermis is the layer of skin directly below the epidermis. This layer contains blood vessels (capillaries), nerve endings, sebaceous glands, hair follicles, elastic fibers, collagenous fibers, involuntary muscles, lymph vessels, and sweat glands.
        Eccrine sweat glandsThe eccrine glands are sudoriferous (sweat) glands that secrete at the palms of the hand, feet, forehead and upper lip.
        EpidermisEpi- means on or upon.
        The epidermis is the top layer of the skin. The epidermis layer does not have blood vessels and does not contain nerve endings.
        HairHair is a filament of keratin that grows from a follicle root and covers most of the body.
        Hair follicleA hair follicle is an opening into the dermis which the hair shaft develops.
        HyponychiumHyponychial means subungual
        Subungual
        Sub- means below or beneath.
        Ungual means pertaining to the fingernail.
        The hyponychium is the area where the nail body is attached just below the free edge.
        KeratinKerat- means horny.
        Keratin is a fibrous protein that is the primary component of the epidermis, hair, and nails.
        LunulaLuna- means moon.
        The lunula is the opaque moon-shaped area at the base of the nail.
        MelaninMelan- means black or melanin
        Melanin is the black or dark brown pigment of skin or hair.
        MelanocytesMelan(o) means black or melanin
        -cyte mean cell.
        A melanocytes is a cell that produces the dark pigment melanin.
        Sebaceous glandsSebaceous pertains to sebum.
        Sebaceous glands are oil glands. The sebaceous glands secrete oil called sebum.
        SebumSeb- means sebum.
        Sebum is an oily secretion from the sebaceous gland that keeps the skin and hair from drying out.
        Stratum corneumStrati- means layer.
        Stratum is a uniformly thick layer.
        Corneus means horny or keratic.
        The stratum corneum is the outer layer of the epidermis composed of dead skin cells that flake away.
        Subcutaneous fasciaSub- means below or beneath
        Cut- means skin.
        Cutaneous means pertaining to the skin.
        Subcutaneous means beneath the skin
        Fascia is a fibrous connective membrane.
        The subcutaneous fascia is the bottom layer of the skin. This layer is composed of connective and fatty tissue.
        Sudoriferous glandSudo- means sweat
        Sudoriferous glands are the sweat glands.

        Procedures of the Integumentary System

        Term Definition
        CryosurgeryCryo- means cold.
        Cryosurgery is a surgery that uses subfreezing temperatures to destroy tissue. This procedure can be used to treat cancers or lesion of the skin.
        CurettageCurette means to scoop.
        Curettage is the scraping of tissue from a surface for microscopic examination.
        ElectrodesiccationElectro- means electricity.
        Desiccare means to dry up.
        Electrodesiccation is a technique which destroys tissue by burning it with an electric spark.
        FaceliftA surgery in which the skin of the face is tightened and wrinkles and other signs of aging of the skin are eliminated.
        A facelift is also known as a rhytidoplasty.
        Rhytid- means wrinkle.
        Plasty- means surgical repair.
        LiposuctionLipo- means fat or adipose.
        Suction means to draw or aspirate a liquid or semi-liquid.
        Liposuction is the removal of adipose tissue with the use of a suction device.
        PhototherapyPhoto- means light.
        Therapy is the treatment of any disease.
        Phototherapy is the treatment of a disorder using light. Phototherapy can be used to treat skin conditions.
        Punch biopsyA punch biopsy is the removal of living tissue for examination.
        Skin graftA skin graft is when a portion of the skin is implanted to cover another area where the skin has been lost.

        Skin Lesions, Diseases, and Conditions of the Integumentary System

        Term Definition
        AcneAcne is a disorder of the sebaceous glands and hair follicles in which pimples, cysts that are infected or abscesses occur.
        AlopeciaAlopecia is the lack of hair due to conditions such as normal aging, skin disorders, anticancer medications, or endocrine disorders.
        Beau’s lineBeau’s line is named for a French physician named Joseph Beau.
        Beau’s line is a white line that occurs across the nails due to a transverse impression that is caused by illnesses such as malnutrition or thyroid dysfunctions.
        Birthmarks Birthmarks are flat areas of discoloration on the skin that are usually brown or tan.
        CarbuncleA carbuncle is a large area of staphylococcal infection appearing as clusters of deep abscesses.
        CarcinomaCarcin- means cancer.
        -oma means tumor.
        -carcinoma means malignant tumor.
        A carcinoma is a malignant neoplasm composed of epithelial cells that invade surrounding tissue and metastasize to different areas of the body.
        CellulitisCellular is consisting of cells.
        -itis means inflammation.
        Cellulitis is a bacterial infection of the skin that is localized and characterized by heat, swelling, pain and other signs of inflammation.
        ClubbingClubbing is an abnormal enlargement of the distal end of the fingers and the angle of the nail is greater than 160 degrees where it meets the cuticle.
        CrustA crust is a hard layer that is formed by the drying of body fluids.
        CyanosisCyan(o) means blue.
        -osis means condition.
        Cyanosis is a bluish tone to the skin. This is due to a decrease in the oxygenation to the tissue.
        CystCyst- means pouch or bladder
        A cyst is a closed pouch under the skin that contains a fluid or a semisolid substance.
        DermatitisDermato- means skin.
        -itis means inflammation.
        Dermatitis is inflammation of the skin.
        EcchymosisEcchymosis is an area of bluish discoloration on the skin caused by the spilling of blood into the subcutaneous tissue caused by some type of trauma to the area. Ecchymosis is also known as a bruise.
        EczemaEczema is dermatitis of unknown cause.
        ErythemaErythem(o) means red
        Erythema is a reddish color to the skin. This occurs when there is a rush of blood to the surface of the skin. Erythema is usually associated with a fever or some type of localized inflammation.
        FissureFiss- means cleft or split.
        A fissure is a cleft or a groove of the skin.
        FolliculitisFolliculitis is the inflammation of the hair follicle.
        FreckleFreckles are patches of melanin pigmentation that occur normally or when the skin is exposed to the sun in some patients.
        FuruncleA furuncle is a staphylococcal infection that originates from the hair follicle.
        HemangiomaHemangi- means a condition of the blood vessel or a collection of blood vessels.
        -oma means tumor.
        A hemangioma is a benign tumor that is a collection of blood vessels.
        HematomaHemat(o) means blood or blood vessel.
        -oma means tumor.
        A hematoma is a collection of blood that is trapped in the skin tissue that is a result of trauma.
        Herpes SimplexHerpes Simplex is an infection that is caused by the herpes simplex virus that affects the skin and nervous system.
        JaundiceJaundice is a yellow tint to the skin, mucous membranes or the sclera of the eye. This is due to increased levels of serum bilirubin in the blood.
        KeloidKel- is a tumor or fibrous growth.
        A keloid is an overgrowth of scar tissue after an injury or surgery.
        Keratosis (Actinic)Actinic means ray or radiation.
        Keratosis is an area of the skin that is overgrown or thickened.
        Actinic keratosis is thickening of the outer layer of the skin caused by prolonged exposure to sunlight.
        MaculeA macule is a discoloration of the skin that is flat and level with the skin.
        MelanomaMelan(o) pertains to melanocytes.
        -oma means tumor.
        A melanoma is a malignant neoplasm of the skin that is composed of melanocytes.
        MoleMoles are an excessive growth of melanocytes. They are usually small, smooth and symmetrical.
        NoduleNod- means knot.
        A nodule is a small node-like structure that is solid and elevated.
        OnycholysisOnych(o) means the nail.
        -lysis is the process of loosening.
        Onycholysis is the loosening or separation of a nail from its bed.
        PallorPallor is when there is a loss of the pinkish tones of the skin due to the lack of blood flow to the surface of the skin or a decrease in blood cells. The skin takes on a whitish color.
        PapuleA papule is a skin lesion that is small, solid and raised caused by thickening of the epidermis.
        PetechiaePetechiae are tiny red or purple spots on the skin that are due to numerous tiny hemorrhages in the dermal layer.
        PruritusPruritus is itchy skin.
        PsoriasisPsoriasis is a skin disorder that is chronic and is characterized by red patchy areas that is also covered by a dry silvery scale.
        PurpuraPrupur- means purple.
        Purpura is a bleeding disorder that is due to hemorrhage into the tissue of the skin which causes ecchymosis or petechiae.
        PustuleA pustule is a small elevation on the skin that contains pus, a creamy viscous fluid.
        ScaleA scale is a thin flake of epithelium that has keratinized.
        Scar tissueScar tissue is skin that is replaced by collagen fibers that do not contain any accessory organs that the layers of the skin normally contain.
        SeborrheaSeb- means sebum.
        -rrhea means fluid discharge or flow.
        Seborrhea is an overproduction of sebum which causes excessive oiliness.
        UlcerAn ulcer is a crater in the skin as a result of necrosis. An ulcer can be shallow or deep and can be accompanied by an infection or inflammation.
        UrticariaUrticaria is a skin eruption that has wheals of various shapes that have red margins and a pale center.
        VesicleVesic(o) means bladder or blister.
        A vesicle is a small bladder or blister that contains a clear fluid.
        VitiligoVitiligo is a skin disease of unknown caused that is benign and characterized by irregular patches of skin that lack pigment.
        WhealA wheal is an area of the skin that is slightly raised and appears either redder or paler than the surrounding skin.

        Reference

        Mosby’s Medical Dictionary (2017). 10th ed. St Louis, MO. Elsevier Inc.

        Disclaimer: The information contained on this site is not intended or implied to be a substitution for professional medical advice, diagnosis or treatment. All content, including text, graphics, images, and information, contained is provided for educational purposes only. You assume full responsibility for how you chose to use this information.


        Some Recent Findings

        • Dermal Condensate Niche Fate Specification Occurs Prior to Formation and Is Placode Progenitor DependentΏ] "Cell fate transitions are essential for specification of stem cells and their niches, but the precise timing and sequence of molecular events during embryonic development are largely unknown. Here, we identify, with 3D and 4D microscopy, unclustered precursors of dermal condensates (DC), signaling niches for epithelial progenitors in hair placodes. With population-based and single-cell transcriptomics, we define a molecular time-lapse from pre-DC fate specification through DC niche formation and establish the developmental trajectory as the DC lineage emerges from fibroblasts. Co-expression of downregulated fibroblast and upregulated DC genes in niche precursors reveals a transitory molecular state following a proliferation shutdown. Waves of transcription factor and signaling molecule expression then coincide with DC formation. Finally, ablation of epidermal Wnt signaling and placode-derived FGF20 demonstrates their requirement for pre-DC specification."
        • Mutations in TSPEAR, Encoding a Regulator of Notch Signaling, Affect Tooth and Hair Follicle Morphogenesisΐ] "In the present study, we aimed at elucidating the genetic basis of a new form of ED featuring facial dysmorphism, scalp hypotrichosis and hypodontia. Using whole exome sequencing, we identified 2 frameshift and 2 missense mutations in TSPEAR segregating with the disease phenotype in 3 families. TSPEAR encodes the thrombospondin-type laminin G domain and EAR repeats (TSPEAR) protein, whose function is poorly understood. TSPEAR knock-down resulted in altered expression of genes known to be regulated by NOTCH and to be involved in murine hair and tooth development. Pathway analysis confirmed that down-regulation of TSPEAR in keratinocytes is likely to affect Notch signaling. Accordingly, using a luciferase-based reporter assay, we showed that TSPEAR knock-down is associated with decreased Notch signaling. In addition, NOTCH1 protein expression was reduced in patient scalp skin. Moreover, TSPEAR silencing in mouse hair follicle organ cultures was found to induce apoptosis in follicular epithelial cells, resulting in decreased hair bulb diameter."

        This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.

        • This search now requires a manual link as the original PubMed extension has been disabled.
        • The displayed list of references do not reflect any editorial selection of material based on content or relevance.
        • References also appear on this list based upon the date of the actual page viewing.


        References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

        See also the Discussion Page for other references listed by year and References on this current page.


        BIO 140 - Human Biology I - Textbook

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        Chapter 14

        Layers of the Skin

        • Identify the components of the integumentary system
        • Describe the layers of the skin and the functions of each layer
        • Identify and describe the hypodermis and deep fascia
        • Describe the role of keratinocytes and their life cycle
        • Describe the role of melanocytes in skin pigmentation

        Although you may not typically think of the skin as an organ, it is in fact made of tissues that work together as a single structure to perform unique and critical functions. The skin and its accessory structures make up the integumentary system , which provides the body with overall protection. The skin is made of multiple layers of cells and tissues, which are held to underlying structures by connective tissue (Figure 1). The deeper layer of skin is well vascularized (has numerous blood vessels). It also has numerous sensory, and autonomic and sympathetic nerve fibers ensuring communication to and from the brain.

        Figure 1: The skin is composed of two main layers: the epidermis, made of closely packed epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures. Beneath the dermis lies the hypodermis, which is composed mainly of loose connective and fatty tissues.

        Click on the link below to view an animation about the layers of the skin. The skin consists of two main layers and a closely associated layer. What are the basic functions of each of these layers?

        The Epidermis

        The epidermis is composed of keratinized, stratified squamous epithelium. It is made of four or five layers of epithelial cells, depending on its location in the body. It does not have any blood vessels within it (i.e., it is avascular). Skin that has four layers of cells is referred to as &ldquothin skin.&rdquo From deep to superficial, these layers are the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. Most of the skin can be classified as thin skin. &ldquoThick skin&rdquo is found only on the palms of the hands and the soles of the feet. It has a fifth layer, called the stratum lucidum, located between the stratum corneum and the stratum granulosum (Figure 2).

        Figure 2: These slides show cross-sections of the epidermis and dermis of (a) thin and (b) thick skin. Note the significant difference in the thickness of the epithelial layer of the thick skin. From top, LM × 40, LM × 40. (Micrographs provided by the Regents of University of Michigan Medical School © 2012)

        The cells in all of the layers except the stratum basale are called keratinocytes. A keratinocyte is a cell that manufactures and stores the protein keratin. Keratin is an intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from the deeper layers (Figure 3).

        Figure 3: The epidermis is epithelium composed of multiple layers of cells. The basal layer consists of cuboidal cells, whereas the outer layers are squamous, keratinized cells, so the whole epithelium is often described as being keratinized stratified squamous epithelium. LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

        Click on the link below to view the University of Michigan WebScope to explore the tissue sample in greater detail. (Note: requires that you have Flash Player installed on your computer). If you zoom on the cells at the outermost layer of this section of skin, what do you notice about the cells?

        Stratum Basale

        The stratum basale (also called the stratum germinativum) is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. The cells in the stratum basale bond to the dermis via intertwining collagen fibers, referred to as the basement membrane. A finger-like projection, or fold, known as the dermal papilla (plural = dermal papillae) is found in the superficial portion of the dermis. Dermal papillae increase the strength of the connection between the epidermis and dermis the greater the folding, the stronger the connections made (Figure 4).

        Figure 4: The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

        The stratum basale is a single layer of cells primarily made of basal cells. A basal cell is a cuboidal-shaped stem cell that is a precursor of the keratinocytes of the epidermis. All of the keratinocytes are produced from this single layer of cells, which are constantly going through mitosis to produce new cells. As new cells are formed, the existing cells are pushed superficially away from the stratum basale. Two other cell types are found dispersed among the basal cells in the stratum basale. The first is a Merkel cell , which functions as a receptor and is responsible for stimulating sensory nerves that the brain perceives as touch. These cells are especially abundant on the surfaces of the hands and feet. The second is a melanocyte , a cell that produces the pigment melanin. Melanin gives hair and skin its color, and also helps protect the living cells of the epidermis from ultraviolet (UV) radiation damage.

        In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying dermal layer (papillary layer), resulting in the formation of the ridges on your fingers that you recognize as fingerprints. Fingerprints are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes.

        Stratum Spinosum

        As the name suggests, the stratum spinosum is spiny in appearance due to the protruding cell processes that join the cells via a structure called a desmosome . The desmosomes interlock with each other and strengthen the bond between the cells. It is interesting to note that the &ldquospiny&rdquo nature of this layer is an artifact of the staining process. Unstained epidermis samples do not exhibit this characteristic appearance. The stratum spinosum is composed of eight to 10 layers of keratinocytes, formed as a result of cell division in the stratum basale (Figure 5). Interspersed among the keratinocytes of this layer is a type of dendritic cell called the Langerhans cell , which functions as a macrophage by engulfing bacteria, foreign particles, and damaged cells that occur in this layer.

        Figure 5: The cells in the different layers of the epidermis originate from basal cells located in the stratum basale, yet the cells of each layer are distinctively different. EM × 2700. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

        Click on the link below to view the University of Michigan WebScope to explore the tissue sample in greater detail. (Note: requires that you have Flash Player installed on your computer). If you zoom on the cells at the outermost layer of this section of skin, what do you notice about the cells?

        The keratinocytes in the stratum spinosum begin the synthesis of keratin and release a water-repelling glycolipid that helps prevent water loss from the body, making the skin relatively waterproof. As new keratinocytes are produced atop the stratum basale, the keratinocytes of the stratum spinosum are pushed into the stratum granulosum.

        Stratum Granulosum

        The stratum granulosum has a grainy appearance due to further changes to the keratinocytes as they are pushed from the stratum spinosum. The cells (three to five layers deep) become flatter, their cell membranes thicken, and they generate large amounts of the proteins keratin, which is fibrous, and keratohyalin , which accumulates as lamellar granules within the cells (see Figure 4). These two proteins make up the bulk of the keratinocyte mass in the stratum granulosum and give the layer its grainy appearance. The nuclei and other cell organelles disintegrate as the cells die, leaving behind the keratin, keratohyalin, and cell membranes that will form the stratum lucidum, the stratum corneum, and the accessory structures of hair and nails.

        Stratum Lucidum

        The stratum lucidum is a smooth, seemingly translucent layer of the epidermis located just above the stratum granulosum and below the stratum corneum. This thin layer of cells is found only in the thick skin of the palms, soles, and digits. The keratinocytes that compose the stratum lucidum are dead and flattened (see Figure 4). These cells are densely packed with eleiden , a clear protein rich in lipids, derived from keratohyalin, which gives these cells their transparent (i.e., lucid) appearance and provides a barrier to water.

        Stratum Corneum

        The stratum corneum is the most superficial layer of the epidermis and is the layer exposed to the outside environment (see Figure 4). The increased keratinization (also called cornification) of the cells in this layer gives it its name. There are usually 15 to 30 layers of cells in the stratum corneum. This dry, dead layer helps prevent the penetration of microbes and the dehydration of underlying tissues, and provides a mechanical protection against abrasion for the more delicate, underlying layers. Cells in this layer are shed periodically and are replaced by cells pushed up from the stratum granulosum (or stratum lucidum in the case of the palms and soles of feet). The entire layer is replaced during a period of about 4 weeks. Cosmetic procedures, such as microdermabrasion, help remove some of the dry, upper layer and aim to keep the skin looking &ldquofresh&rdquo and healthy.

        Everyday Connection

        Skin Color

        The skin is the largest and most visible organ of the body. Variance in skin color is not only determined by the color of melanin which ranges from very light brown, red, to very dark brown, but also the position in which cells receiving melanin pigments from the melanosomes are situated in the skin strata. Cells situated closer to the outer surface of the skin will reveal more melanin pigmentation compared to cells located further away from the outer surface of the skin. Additionally, the amount of carotene and hemoglobin can contribute to skin color.

        The figures above show melanin in the upper layers of the skin are more visible compared to those housed in the cells in the lower layers of the skin stratum. Thus a fair colored person may either have a darker melanin pigment housed in the lower cell layers of the skin stratum or alternatively, may have a lighter melanin pigment housed in the top layered cells of the skin stratum.

        Watch the video in the link below to learn more about skin color.

        Dermis

        The dermis might be considered the &ldquocore&rdquo of the integumentary system (derma- = &ldquoskin&rdquo), as distinct from the epidermis (epi- = &ldquoupon&rdquo or &ldquoover&rdquo) and hypodermis (hypo- = &ldquobelow&rdquo). It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. The dermis is made of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers, produced by fibroblasts (Figure 6).

        Figure 6: This stained slide shows the two components of the dermis&mdashthe papillary layer and the reticular layer. Both are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct. The dermal papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen fiber bundles below belong to the reticular layer. LM × 10. (credit: modification of work by &ldquokilbad&rdquo/Wikimedia Commons)

        Papillary Layer

        The papillary layer is made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh. This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae (see Figure 6). Within the papillary layer are fibroblasts, a small number of fat cells (adipocytes), and an abundance of small blood vessels. In addition, the papillary layer contains phagocytes, defensive cells that help fight bacteria or other infections that have breached the skin. This layer also contains lymphatic capillaries, nerve fibers, and touch receptors called the Meissner corpuscles.

        Reticular Layer

        Underlying the papillary layer is the much thicker reticular layer , composed of dense, irregular connective tissue. This layer is well vascularized and has a rich sensory and sympathetic nerve supply. The reticular layer appears reticulated (net-like) due to a tight meshwork of fibers. Elastin fibers provide some elasticity to the skin, enabling movement. Collagen fibers provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis. In addition, collagen binds water to keep the skin hydrated. Collagen injections and Retin-A creams help restore skin turgor by either introducing collagen externally or stimulating blood flow and repair of the dermis, respectively.

        Hypodermis

        The hypodermis (also called the subcutaneous layer or superficial fascia) is a layer directly below the dermis and serves to connect the skin to the underlying fascia (fibrous tissue) of the bones and muscles. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument.

        Everyday Connection

        Lipid Storage

        The hypodermis is home to most of the fat that concerns people when they are trying to keep their weight under control. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes. This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma.

        Where the fat is deposited and accumulates within the hypodermis depends on hormones (testosterone, estrogen, insulin, glucagon, leptin, and others), as well as genetic factors. Fat distribution changes as our bodies mature and age. Men tend to accumulate fat in different areas (neck, arms, lower back, and abdomen) than do women (breasts, hips, thighs, and buttocks). The body mass index (BMI) is often used as a measure of fat, although this measure is, in fact, derived from a mathematical formula that compares body weight (mass) to height. Therefore, its accuracy as a health indicator can be called into question in individuals who are extremely physically fit.

        In many animals, there is a pattern of storing excess calories as fat to be used in times when food is not readily available. In much of the developed world, insufficient exercise coupled with the ready availability and consumption of high-calorie foods have resulted in unwanted accumulations of adipose tissue in many people. Although periodic accumulation of excess fat may have provided an evolutionary advantage to our ancestors, who experienced unpredictable bouts of famine, it is now becoming chronic and considered a major health threat. Recent studies indicate that a distressing percentage of our population is overweight and/or clinically obese. Not only is this a problem for the individuals affected, but it also has a severe impact on our healthcare system. Changes in lifestyle, specifically in diet and exercise, are the best ways to control body fat accumulation, especially when it reaches levels that increase the risk of heart disease and diabetes.

        Pigmentation

        The color of skin is influenced by a number of pigments, including melanin, carotene, and hemoglobin. Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis. The melanin is transferred into the keratinocytes via a cellular vesicle called a melanosome (Figure 7).

        Figure 7: The relative coloration of the skin depends of the amount of melanin produced by melanocytes in the stratum basale and taken up by keratinocytes.

        Melanin occurs in two primary forms. Eumelanin exists as black and brown, whereas pheomelanin provides a red color. Dark-skinned individuals produce more melanin than those with pale skin. Exposure to the UV rays of the sun or a tanning salon causes melanin to be manufactured and built up in keratinocytes, as sun exposure stimulates keratinocytes to secrete chemicals that stimulate melanocytes. The accumulation of melanin in keratinocytes results in the darkening of the skin, or a tan. This increased melanin accumulation protects the DNA of epidermal cells from UV ray damage and the breakdown of folic acid, a nutrient necessary for our health and well-being. In contrast, too much melanin can interfere with the production of vitamin D, an important nutrient involved in calcium absorption. Thus, the amount of melanin present in our skin is dependent on a balance between available sunlight and folic acid destruction, and protection from UV radiation and vitamin D production.

        It requires about 10 days after initial sun exposure for melanin synthesis to peak, which is why pale-skinned individuals tend to suffer sunburns of the epidermis initially. Dark-skinned individuals can also get sunburns, but are more protected than are pale-skinned individuals. Melanosomes are temporary structures that are eventually destroyed by fusion with lysosomes this fact, along with melanin-filled keratinocytes in the stratum corneum sloughing off, makes tanning impermanent.

        Too much sun exposure can eventually lead to wrinkling due to the destruction of the cellular structure of the skin, and in severe cases, can cause sufficient DNA damage to result in skin cancer. When there is an irregular accumulation of melanocytes in the skin, freckles appear. Moles are larger masses of melanocytes, and although most are benign, they should be monitored for changes that might indicate the presence of cancer ( Figure 8).

        Figure 8: Moles range from benign accumulations of melanocytes to melanomas. These structures populate the landscape of our skin. (credit: the National Cancer Institute)

        Disorders of the&hellip

        Integumentary System

        The first thing a clinician sees is the skin, and so the examination of the skin should be part of any thorough physical examination. Most skin disorders are relatively benign, but a few, including melanomas, can be fatal if untreated. A couple of the more noticeable disorders, albinism and vitiligo, affect the appearance of the skin and its accessory organs. Although neither is fatal, it would be hard to claim that they are benign, at least to the individuals so afflicted.

        Albinism is a genetic disorder that affects (completely or partially) the coloring of skin, hair, and eyes. The defect is primarily due to the inability of melanocytes to produce melanin. Individuals with albinism tend to appear white or very pale due to the lack of melanin in their skin and hair. Recall that melanin helps protect the skin from the harmful effects of UV radiation. Individuals with albinism tend to need more protection from UV radiation, as they are more prone to sunburns and skin cancer. They also tend to be more sensitive to light and have vision problems due to the lack of pigmentation on the retinal wall. Treatment of this disorder usually involves addressing the symptoms, such as limiting UV light exposure to the skin and eyes. In vitiligo , the melanocytes in certain areas lose their ability to produce melanin, possibly due to an autoimmune reaction. This leads to a loss of color in patches (Figure 9). Neither albinism nor vitiligo directly affects the lifespan of an individual.

        Figure 9: Individuals with vitiligo experience depigmentation that results in lighter colored patches of skin. The condition is especially noticeable on darker skin. (credit: Klaus D. Peter)

        Other changes in the appearance of skin coloration can be indicative of diseases associated with other body systems. Liver disease or liver cancer can cause the accumulation of bile and the yellow pigment bilirubin, leading to the skin appearing yellow or jaundiced (jaune is the French word for &ldquoyellow&rdquo). Tumors of the pituitary gland can result in the secretion of large amounts of melanocyte-stimulating hormone (MSH), which results in a darkening of the skin. Similarly, Addison&rsquos disease can stimulate the release of excess amounts of adrenocorticotropic hormone (ACTH), which can give the skin a deep bronze color. A sudden drop in oxygenation can affect skin color, causing the skin to initially turn ashen (white). With a prolonged reduction in oxygen levels, dark red deoxyhemoglobin becomes dominant in the blood, making the skin appear blue, a condition referred to as cyanosis (kyanos is the Greek word for &ldquoblue&rdquo). This happens when the oxygen supply is restricted, as when someone is experiencing difficulty in breathing because of asthma or a heart attack. However, in these cases the effect on skin color has nothing do with the skin&rsquos pigmentation.

        The ABC video linked to below follows the story of a pair of fraternal African-American twins, one of whom is albino. Click on the link below to watch a video about the challenges these children and their family face. Which ethnicities do you think are exempt from the possibility of albinism?

        Chapter Review

        The skin is composed of two major layers: a superficial epidermis and a deeper dermis. The epidermis consists of several layers beginning with the innermost (deepest) stratum basale (germinatum), followed by the stratum spinosum, stratum granulosum, stratum lucidum (when present), and ending with the outermost layer, the stratum corneum. The topmost layer, the stratum corneum, consists of dead cells that shed periodically and is progressively replaced by cells formed from the basal layer. The stratum basale also contains melanocytes, cells that produce melanin, the pigment primarily responsible for giving skin its color. Melanin is transferred to keratinocytes in the stratum spinosum to protect cells from UV rays.

        The dermis connects the epidermis to the hypodermis, and provides strength and elasticity due to the presence of collagen and elastin fibers. It has only two layers: the papillary layer with papillae that extend into the epidermis and the lower, reticular layer composed of loose connective tissue. The hypodermis, deep to the dermis of skin, is the connective tissue that connects the dermis to underlying structures it also harbors adipose tissue for fat storage and protection.


        Integumentary System Functions

        Protection

        The most important function of the integumentary system is protection. The organs of the integumentary system form a water-proof layer over the body that also work as a physical barrier against microorganisms that cause integumentary system diseases.

        Homeostasis

        Would you like to write for us? Well, we're looking for good writers who want to spread the word. Get in touch with us and we'll talk.

        Environmental conditions outside the body keep changing. However, for different organs to work properly, specific environmental conditions are required. Homeostasis refers to regulating internal environment of the body to maintain stable conditions. This is achieved by the integumentary organs which ensures proper functioning of all the organs of the body.

        Sensory Organ

        The skin has a large number of nerve openings that help us in perceiving the sense of touch, pressure, pain, and changes in temperature.

        Excretion

        Toxic wastes are excreted by the skin in the form of perspiration.


        Integumentary System Overview - Anatomy & Physiology

        The integumentary system is an organ system that forms the protective covering of an animal and comprises the skin (including glands and their products), haircoat or feathers, scales, nails, hooves and horns.

        The integumentary system has a variety of functions in animals, it serves to waterproof, cushion and protect the deeper tissues, excrete waste, regulate temperature and is the location of sensory receptors for pain, pressure and temperature. Generally mammalian skin is covered with hair and is termed hirsute skin. Where hair is absent, it is termed glabrous skin.

        The integumentary system is often the largest organ system. It distinguishes, separates, protects and informs the animal with regard to its surroundings. Small-bodied invertebrates of aquatic or continually moist habitats also respire using the outer layer (integument). This gas exchange system, where gases simply diffuse into and out of the interstitial fluid, is called integumentary exchange. The skin is an organ that shows complex adaptations many of which are species specific - fish, birds, reptiles and amphibians have modifications of the integumen that are tailored to meet the survival needs of each species. Specific lifestyles such as those including hibernation require additional modifications to support the skin such as the phsiologically adapted brown adipose tissue which generates body heat from specialised subcutaneous fat cells.

        The skin can be reflective of the health status of an animal, being sensative to certain hormonal and nutritional conditions.


        Watch the video: The Integumentary System, Part 1 - Skin Deep: Crash Course Au0026P #6 (July 2022).


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