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					Date: Sept. 14, 2009 Source: Details:  Integumentary System: o Skin:         o    Covers your body Known as the cutaneous membrane (cutaneous layer) A vulnerable barrier to the outside world Subjected to trauma, harmful chemicals, pollutants, microbes, and damaging sunlight Remains strong and pliable, is easily cleaned, is self-renewing, and serves as a visual indicator of our physiology and health Changes in the color of the skin may reflect body disorders or anomalies Skin changes or lesions sometimes indicate systemic infections or diseases Scientific study and treatment of the Integumentary system is called dermatology “Integumentary System” – Chapter 5

Integumentary system: Consists of the skin and its derivatives (nails, hair, sweat glands, and sebaceous glands) Most conscious of this highly visible Over-examined body system, because it characterizes our self-image and reflects our emotions

 Structure and Function of the Integument o Integument or skin        o Body’s largest organ Not as complex as most other organs Does consist of different tissue types that collectively perform specific activities Covered by an epithelium that protects underlying body layers Connective tissues that underlie the epithelium contain blood vessels, which provide nutrients to the epithelial cells and give strength and resilience to the skin Smooth muscle controls blood vessel diameter and hair position for these Integumentary structures Nervous tissue supports and monitors sensory receptors in the skin, which provide information about touch, pressure, temperature, and pain Integument structure:    Covers the entire body surface Area that ranges between about 1.5 and 2.0 square meters Accounts for 7% to 8% of the body weight

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Thickness ranges between 1.5 and 4 mm or more, depending on body location Consists of two distinct layers:   Layer of stratified squamous epithelium (epidermis) Deeper layer of dense irregular connective tissue (dermis) o Deep to the dermis is a layer of:   Areolar and adipose connective tissue called the subcutaneous layer (hypodermis) Subcutaneous layer:  Not part of the Integumentary system

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Integument meets the mucous membranes within the:       Nostrils Lips Anus Urethral opening Vaginal opening These sites, the transition is seamless, and the epithelial defenses remain intact and functional

o

Integument functions:   More than just a wrapping around the body Serves many varied functions:  Protection o o o o Acts as a physical barrier that protects the entire body from physical injury, trauma, bumps, and scrapes Offers protection against harmful chemicals, toxins, microbes, and excessive heat or cold Absorb certain chemicals and drugs Selectively permeable:  o o o o  Materials are able to pass through it while others are effectively blocked Epidermis is designed to withstand stresses and regenerate itself continuously throughout a person’s lifetime Protects deeper tissues from solar radiation, especially ultraviolet rays Exposed to sun, the melanocytes become more active and produce more melanin, thus giving the skin darker, tanned look Sunburn, the deeper tissues (muscles and internal organs) remain unaffected Prevention of water loss 2

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Water resistant Helps prevent unnecessary water loss Water cannot easily enter or exit the skin, unless it is specifically secreted by the sweat glands Prevents the water within the body cells and in the extracellular (the fluid outside of cells) from “leaking out” Skin is severely burned, a primary danger is dehydration, because the individual has lost the protective skin barrier, and water can escape from body tissues

o o

Water resistant, it is not entirely waterproof Interstitial fluids slowly escape through the epidermis to the surface, where they evaporate into the surrounding air (transepidermal water loss “TEWL”)

o o

Approx. 500 milliliters of water is lost daily by evaporation of moisture from the skin or from respiratory passageways during breathing Insensible perspiration:  Release of water vapor from sweat glands under “normal” circumstances when we are not sweating

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Sensible perspiration:  sweating

Temperature regulation o o Body temperature is influenced by vast capillary networks and sweat glands in the dermis Body is too warm:   Needs to dissipate heat Diameter of the blood vessels in the dermis enlarges to permit more blood flow through the dermis and sweat glands release fluid onto the skin surface o More blood flows through these dermal vessels, the warmth from the blood dissipates through the skin, and the body cools off by evaporation of the sweat o Body is cold:   o Needs to conserve heat Blood vessels in the dermis constrict to reduce blood flow

Effort to conserve heat, more blood is shunted to deeper body tissues, and relatively less blood flows in the dermal blood vessels

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Metabolic regulation

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Vitamin D3  A cholesterol derivative synthesized from cholecalciferol which is produced by some epidermal cells when they are exposed to ultraviolet radiation

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Calcitriol   Synthesized from the cholecalciferol by some endocrine cells in the kidney Active form of vitamin d3 (a hormone that promotes calcium and phosphorus absorption from ingested materials across the wall of the small intestine   Important in regulating the levels of calcium and phosphate in the blood 15 minutes of sunlight a day will provide your body with its daily vitamin d requirement

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Immune defense o o Epidermis contains a small population of immune cells Immune cells is epidermal dendritic cells (langerhans cells)  Play an important role in initiating an immune response by phagocytizing pathogens that have penetrated the epidermis and also against epidermal cancer cells

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Sensory reception o o Numerous sensory receptors Associated with nerve endings that detect:       o  Heat Cold Touch Pressure Texture Vibration

Example: Tactile cells (merkel cells)   Large Specialized epithelial cells that stimulate specific sensory nerve endings when they are distorted by fine touch or pressure

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Skin is responsible for perceiving many stimuli, needs different sensory receptor types to detect, distinguish, and interpret these stimuli 4

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Excretion by means of secretion o o o o Exhibits an excretory function when it secretes substances from the body during sweating Sweating or sensible perspiration, occurs when the body needs to cool itself off Sweat sometimes feels “gritty” because of the waste products being secreted onto the skin surface Substances include:     o o Water Salts Urea (a nitrogen-containing A nitrogen-containing waste product of body cells

Skin contains sebaceous glands that secrets an oily material called sebum Sebum:  Lubricates the skin surface and hair

 Epidermis o o Epithelium of the integument Epidermis:     o  Keratinized Stratified squamous epithelium Avascular (no blood vessels) Acquires its nutrients through diffusion from the underlying dermis

Epidermal strata: Deep to superficial:  Stratum basale o o o o o Deepest epidermal layer Known as stratum germinativum or basal layer Single layer of cells ranges from cuboidal to low columnar in appearace Tightly attached to an underlying basement membrane that separates the epidermis from the connective tissue of the adjacent dermis Three types of cells occupy the stratum basale:  Keratinocytes    Most abundant cell type in the epidermis Found throughout all epidermal strata Dominated by large keratinocyte stem cells o 5 Divide to provide both replacement stem cells

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New keratinocytes that replace the dead keratinocytes shed from the surface

Keratin: o o o Name is derived from their role in the synthesis of the protein keratin in the epidermal cells of the skin A family of fibrous structural proteins that are both tough and insoluble Fibrous keratin molecules can twist and intertwine around each other to form helical intermediate filaments of the cytoskeleton o o Found in epidermal cells of the skin are called cytokeratins Structure in these cells gives skin its strength and makes the epidermis almost waterproof

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Melanocytes    Long branching cytoplasmic processes Scattered among the keratinocytes of the stratum basale Processes transfer pigment granules called melanosomes, into the keratinocytes within the basal layer and sometimes within more superficial layers  Pigment (black, brown, or yellow-brown) o o o Accumulates around the nucleus of the keratinocyte Shields the DNA within the nucleus from ultraviolet radiation Darker tones of the skin result from melanin being produced by the melanocytes and from the darkening of melanin already present upon exposure to ultraviolet light

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Tactile cells     Few in number Found scattered among the cells within the stratum basale Sensitive to touch, and when compressed Release chemical that stimulate sensory nerve endings, providing information about objects touching the skin

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Stratum spinosum o Several layers of polygonal keratinocytes (spiny layer) 6

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Each time a keratinocyte stem cell in the stratum basale divides, the daughter cell that will differentiate into the new epidermal cell is pushed toward the external surface from the stratum basale

o o

Deepest cell in this layer still undergo mitosis to help replace epidermal cells that exfoliate from the epidermal surface Desmosomes:  Nondividing keratinocytes in the stratum spinosum attach to their neighbors by many intercellular junctions

o

Contains the fourth epidermal cell type, the epidermal dendritic cells   Immune cells that help fight infection in the epidermis Often present but not easily identifiable in both the stratum spinosum and the more superficial stratum granulosum  Phagocytic activity initiates an immune response to protect the body against pathogens that have penetrated the superficial layers of the epidermis as well as against epidermal cancer cells

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Stratum granulosum o o o Known as granular layer Consists of three to five layers of keratinocytes superficial to the stratum spinosum Within this stratum begins a process called keratinization       o o Keratinocytes fill up with the protein keratin Several significant events occur during this process Cells pass through the stratum granulosum and true keratin filaments begin to develop Cells become thinner and flatter Membranes thicken and become less permeable Nucleus and all organelles disintegrate, and the cells start to die

Keratinization is not complete until the cells reach the more superficial epidermal layers A fully keratinized cell is dead but it is strong because it contains keratin

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Stratum lucidum (found in thick skin only) o o o o Known as clear layer A thin Translucent region about two to three cell layers that is superficial to the stratum granulosum Found only in thick skin like:

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Palms of the hands Soles of the feet

Cells occupying this layer appear pale and featureless, and have indistinct boundaries Keratinocytes within this layer are flattened and filled with the protein eleidin Eleidin:  Intermediate product in the process of keratin maturation

Stratum corneum o o o o o Known as hornlike layer Most superficial layer of the epidermis Stratum you see when you look at your skin Consists of about 20-30 layers of dead, scaly, interlocking keratinized cells called corneocytes Anucleate:   o o Dead cells Tightly packed together

Keratinized epithelium contains large amounts of keratin The dead, keratinized cells usually remain for an additional 2 weeks in the exposed stratum corneum layer, providing a barrier for cells deeper in the epidermis before they are shed, washed away, or removed by abrasion

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First three strata listed are composed of living keratinocytes Last two strata contain dead keratinocytes

Variations in the epidermis: Among different body regions within a single individual Differences between individuals Epidermis varies in:       Thickness Coloration Skin markings

Thick skin versus thin skin: Skin ranges from 1 mm to 2 mm in thickness Classified as either thick or thin based on the number of strata in the epidermis and the relative thickness of the epidermis, rather than the thickness of the entire integument  Thick skin:

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o o o o  o o o

Found on the palms of the hands, the soles of the feet, and corresponding surfaces of the fingers and toes All five epidermal strata occur in thick skin Ranges between 400 and 600 micrometers thick Contains sweat glands, but no hair follicles or sebaceous glands

Thin skin: Covers most of the body Epidermis lacks the stratum lucidum, so it has only four layers Contains the following accessories:    o Hair follicles Sebaceous glands Sweat glands

Ranges between 75 to 150 micrometers thick

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Skin color:  Normal skin color results from a combination of: o Hemoglobin   An oxygen-binding protein present within red blood cells Upon biding oxygen, hemoglobin exhibits a bright red color, giving blood vessels in the dermis a bright reddish tint that is most easily observed in the skin of lightly pigmented individuals o Melanin  Melanocytes:     A pigment produced Stored in cells

This pigment is synthesized from the amino acid tyrosine, and its production requires the enzyme tyrosinase Two types of melanin:    Eumelanin Pheomelanin Occur in various ratios of yellow, reddish, tan, brown, and black shades

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Transferred in membrane-bound vesicles from melanocytes to keratinocytes in the stratum basale Keratinocytes that receive the melanin are displaced toward the stratum corneum and thus melanocyte activity affects the color of the entire epidermis

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All people have about the same number of melanocytes 9

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Amount of melanin in the skin is determined by both heredity and light exposure Pigment surrounds the keratinocyte nucleus, where it absorbs ultraviolet radiation in sunlight, thus preventing damage to nuclear DNA

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Carotene  A yellow-orange pigment that is acquired in the body by eating various yellow-orange vegetables:       Carrots Corn Squash

Carotene accumulates inside keratinocytes of the stratum corenum and within the subcutaneous fat Carotene is converted into vitamin A, which has an important function in normal vision Implicated in reducing the number of potentially dangerous molecules formed during normal metabolic activity and in improving immune cell number and activity

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Skin markings:  Nevus (mole, or birthmark) o Commonly called a mole   o o o  o o  Harmless Localized overgrowth of melanin-forming cells

Almost everyone is born with a few nevi, and some people have as many as 20 or more May become malignant, typically as a consequence of excessive UV light exposure Should be monitored for changes that may suggest malignancy

Freckles Yellowish or brown spots that represent localized areas of excessive melanocyte activity, not an increase in melanocyte numbers Degree of pigmentation varies and depends on both sun exposure and heredity Hemangioma o Congenital anomaly that results in skin discoloration due to blood vessels that proliferate and for a benign tumor

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Capillary hemangiomas or strawberry-colored birthmarks, appear in the skin as bright red to deep purple nodules that usually disappear in childhood

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Cavernous hemangiomas is port-win stains involve larger dermal blood vessels and may last a lifetime

Friction ridges o o Contours of the skin surface follow ridge patterns, varying from small, conical pegs to complex arches and whorls Found on the:     o o o Fingers Palms Soles Toes

Formed from large folds and valleys of both the dermis and epidermis Increase friction so that objects do not slip easily from our hands and our feet do not slip on the floor when we walk Can leave noticeable prints on touched surfaces, commonly called fingerprints   Each individual has a unique pattern of friction ridges Fingerprints have become a valuable identification tool for law enforcement, and medical applications

 Dermis o o o Lies deep to the epidermis Ranges in thickness from 0.5 to 3.0 micrometers Connective tissue layer of the integument is composed:   o        o  Cells of the connective tissue proper Primarily of collagen fibers, although both elastic and reticular fibers are also present

Other components of the dermis: Blood vessels Sweat glands Sebaceous glands Hair follicles Nail roots Sensory nerve endings Smooth muscle tissue

Two major regions of the dermis: A superficial papillary layer

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Superficial region of the dermis directly adjacent to the epidermis Composed of areolar connective tissue Derives its name from the projections of the dermis toward the epidermis called dermal papillae o Interlock with deep projections of epidermis called epidermal ridges

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Together, the epidermal ridges and dermal papillae increase the area of contact between the epidermis and dermis and connect these layers Each dermal papilla contains the: o o Capillaries that supply nutrients to the cells of the epidermis Houses sensory receptors

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A deeper reticular layer      Forms the deeper Major portion of the dermis Extends from the thin Overlying papillary layer to the underlying subcutaneous layer Consists primarily of: o  Dense irregular connective tissue through which large bundles of collagen fibers project in all directions Fibers are interwoven into a meshwork that surrounds the structures in the dermis such as: o o o o o    Hair follicles Sebaceous glands Sweat glands Nerves Blood vessels

Word reticular in the name of this layer means “network” and refers to the meshwork of collagen fibers Interwoven collagen fiber bundles obscure any distinct boundary between the papillary and reticular layers Collagen fibers extend internally from the reticular layer of the dermis into the underlying subcutaneous layer

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Stretch marks, wrinkles, and lines of cleavage     Collagen fibers and elastic fibers in the dermis contribute to the observed physical characteristics of the skin Collagen fibers impart tensile strength Elastic fibers allow some stretch and contraction in the dermis during normal movement Stretching of the skin: 12

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May occur as a result of excessive weight gain or pregnancy often exceeds the skin’s elastic capabilities Stretched beyond its capacity, some collagen fibers are torn and result in stretch marks called “striae,” (Furrow) Both the flexibility and thickness of the dermis are diminished by the effects of exposure to UV light and by aging Result in either sagging skin or increased wrinkles

Specific body locations, the majority of the collagen and elastic fibers in the skin are oriented in parallel bundles  Specific orientation of dermal fiber bundles is a result of the direction of applied stress during routine movement o  o o Alignment of the bundles functions to resist stress

Lines of cleavage Skin identify the predominant orientation of collagen fiber bundles Clinically and surgically significant because any procedure resulting in a cut at right angles to a cleavage line is usually pulled open due to the recoil from cut elastic fibers

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Innervation and blood supply  Innervations:          Nerve fibers are extensively dispersed throughout the dermis Nerve fibers in the skin monitor sensory receptors in the dermis and epidermis and they also control both blood flow and gland secretion rates Tactile corpuscles and tactile cells perceive touch sensations and work with a variety of other sensory nerve endings in the skin All epithelia, including the epidermis are avascular Blood vessels within the dermis must supply nutrients to the living cells in the epidermis as well as to all structures in the dermis Largest of these blood vessels lie along the border between the reticular layer of the dermis and the subcutaneous layer Smaller vessels branch into the dermis to supply the hair follicles, sweat glands, sensory receptors, and other structures housed there The smallest arterial vessels connect to capillary loops within the dermal papillae Dermal blood vessels     Regulating body temperature Blood pressure

Vasocontstriction Diameters of the vessels narrow, so relatively less blood can travel through them 13

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Relatively more blood must travel in blood vessels that are deeper internal to the skin Shunting of blood away from the periphery of the body

Vasodilation Diameter of the vessels increases, so relatively more blood can travel through them

 Subcutaneous Layer (Hypodermis) o Subcutaneous layer     Deep to the integument Known as hypodermis or superficial fascia Not considered a part of the integument Layer consists of both:      Areolar connective tissue Adipose connective tissue

Subcutaneous fat: Adipose connective tissue predominates, and the subcutaneous layer Connective tissue fibers of the reticular layer are extensively interwoven with those of the subcutaneous layer to stabilize the position of the skin and bind it to the underlying tissues  Subcutaneous layer pads o o o o o o Protects the body and its parts Acts as an energy reservoir Provides thermal insulation Drugs are often injected into the subcutaneous layer because its excessive vascular network promotes rapid absorption Thicker in women than in men Regional distribution also differs between the sexes

 Epidermal Accessory Organs o Accessory organs (appendages)  Nails      Scalelike modifications of the epidermis that form on the dorsal tips of the fingers and toes Protect the exposed distal tips Prevent damage or distortion during jumping, kicking, catching, or grasping Hard derivatives from the stratum corenum layer of the epidermis Cells that form the nails are densely packed and filled with parallel fibers of hard keratin 14

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Nail body o o Pinkish which each nail has

Free edge A distal whitish

Nail body appears pink because of the blood flowing in the underlying capillaries Free edge of the nail appears white because there are no underlying capillaries Lunula o o Whitish semilunar area of the proximal end of the nail body Appears whitish because a thickened underlying stratum basale obscures the underlying blood vessels

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Nail folds o o o Lateral and proximal borders of the nail Portions of skin Overlap the nail so that the nail is recessed internal to the level of the surrounding epithelium and is bounded by a nail groove

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Eponychium (cuticle) o A narrow band of epidermis that extends from the margin of the nail wall onto the nail body

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Nail bed o o o Nail body covers a layer of epidermis Contains only the deeper Living cell layers of the epidermis

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Nail root o o The proximal part of the nail embedded in the skin Nail bed thickens to form the nail matrix  Actively growing part of the nail

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Hyponychium o A region of thickened stratum corenum over which the free nail edge projects

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Together: o o o Nail root Nail body Free edge

  Hair 

All these three makes up the nail plate

Found almost everywhere on the body except: o Palms of the hands 15

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Sides and soles of the feet Lips Sides of the fingers and toes Portions of the external genitalia

Most of the hairs on the human body are on the general body surface rather than the head Hair type and distribution: o Pilus      o Single hair Shape of a slender filament Composed of keratinized cells growing from hair follicles that extend deep into the dermis Often projecting into the underlying subcutaneous layer Differences in hair density are due primarily to differences in its texture and pigmentation Three kinds of hair:  Lanugo     Fine Unpigmented Downy hair that first appears on the fetus in the last trimester of development Vellus             At birth, most of the lanugo has been replaced by similarly fine Unpigmented Lightly pigmented hair Primary human hair Found on the upper and lower limbs

Terminal hair Usually coarser Pigmented Longer than vellus Grows on the scalp Hair of eyebrows and eyelashes Forms the: o Beard on the faces of males

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o o o  Hair structure and follicles o

Arms Legs Trunk

Three recognizable zones along the length of a hair:  Hair bulb    Consists of epithelial cells A swelling at the base where the hair originates in the dermis Epithelium at the base of the bulb surrounds a small hair papilla o     Composed of a small amount of connective tissue containing tiny blood vessels and nerves Root  Shaft    Portion of the hair that extends beyond the skin surface Hair within the follicle internal to the skin surface

Root and shaft Consists of dead epithelial cells

Hair bulb Living epithelial cells

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Medulla    Not found in all hair types A remnant of the soft core of the matrix Composed of loosely arranged cells and air spaces and contains flexible, soft kerain

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Cortex  Several layers of flattened cells closer to the outer surface of the developing hair form the relatively hard

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Cuticle     Hair stiffness is derived from the hard keratin contained within the cortex Multiple cell layers around the cortex Coast the hair Free edges of cuticle cells are directed externally

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Hair root extends from the hair bulb to the region where the hair shaft is completely mature 17

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The entire hair root lies:   Internal to the skin Hair shaft extends from the hair root to the exposed tip the hair

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Highly variable like hair shaft’s size, shape, and color Hair follicle:     An oblique tube that surrounds the root hair Always extends into the dermis and sometimes into the subcutaneous layer Cells of the follicle walls are organized into two principal concentric layers Two principal concentric layers:  Outer o  Connective tissue root sheath  Inner o o Epithelial tissue root sheath   Originates from the epidermis Internal root sheath – produced by peripheral cells of the matrix, surrounds both the hair and the deep part of the shaft, and this layer does not extend the entire length of the follicle because its cells are quickly destroyed  External root sheath – extends between the skin surface and the hair matrix, contains the same epidermal cell layers as the skin surface, and all of the cells resemble those of the stratum basale where this sheath joins the hair matrix Originates from the dermis

Two parts of epithelial tissue root sheath:

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Arrector pili    Extending from the dermal papillae are thin ribbons of smooth muscle that are collectively Usually stimulated in response to an emotional state, such as fear or rage or exposure to cold temp. Upon stimulation, it contracts, and pulling on the follicles and elevating the hairs, and to produce goose bumps

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Functions of hair o Protection     o   o Hair on the head protects the scalp from sunburn and injury Hair within the nostrils protect the respiratory system by preventing inhalation of large foreign particles External ear canal protect the ear from insects and foreign particles Eyebrowns and eyelashes protect the eyes

Heat retention Hair on the head prevents the loss of conducted heat from the scalp to the surrounding air Scalp is the only place on the body where the hair is thick enough to retain heat Facial expression  Hairs of the eyebrows function primarily to enhance facial expression

o o

Sensory reception   Associated touch receptors that detect light touch

Visual identification Characteristics are important in determining species, age, and sex and in identifying individuals

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Chemical signal dispersal   Help disperse pheromones, which are chemical signals involved in attracting members of the opposite sex and in sex recognition Secreted by selected sweat glands, such as those in the axillary and pubic regions, they are released onto the hairs in these areas

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Hair color o o o o o o Result of the synthesis of melanin in the matrix adjacent to the papillae Variations in hair color reflect genetically determined differences in the structure of the melanin Environmental and hormonal factors may influence the color of the hair Gray hair results from the gradual reduction of melanin production within the hair follicle White hair signifies the lack of pigment entirely Hair color changes gradually

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Hair growth and replacement

Exocrine glands of the skin

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Two types of exocrine glands: o o Sweat (sudoriferous) glands    Produce a watery solution that performs several specific functions

Sebaceous glands Produce an oily material that coats hair shafts Epidermal surface

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Sweat glands o Two types of sweat glands in the skin:    Merocrine sweat glands Apocrine sweat glands Both types of sweat glands contain myoepithelial cells    Specialized cells are sandwiched between the secretory gland cells Underlying basement membrane

Sympathetic nervous system stimulation, myoepithelial cells contract to squeeze the gland, causing it to discharge its accumulated secretions into the duct

o o

Have a coiled Tubular secretory portion located either in the   Reticular layer of the dermis Subcutaneous layer

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Sweat gland duct o o o Carries the secretion to the surface of the epidermis (in a merocrine gland) Into a hair follicle (in an apocrine gland) Opening of the sweat gland duct on the epidermal surface is an indented region called a sweat pore

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Merocrine sweat glands: o o o o o Simple Coiled Tubular glands that release their secretion onto the surface of the skin Most numerous and widely distributed sweat glands in the body Locations:    o o Palms of the hands Soles of the feet Forehead (highest numbers of these glands)

Controlled by the nervous system Secretory portion of the gland is housed within the 20

  o   o o  Sweat:  

Dermis Subcutaneous layer

Conducting portion of the gland Undulating Coiled duct leading to a sweat pore on the skin surface

Sweat or sensible perspiration Clear secretion produced by merocrine glands

99% water 1% other chemicals    Electrolytes (primarily sodium and chloride) Metabolites (lactic acid) Waste products (urea and ammonia)

  o

Sodium chloride gave sweat a salty taste

Functions of merocrine sweat glands: Thermoregulation   o   o  Help regulate body temp. through evaporation of fluid from the skin Regulated by neural controls

Secretion Help rid the body of excess water and electrolytes Help eliminate some types of ingested drugs

protection protect against environmental hazards both by diluting harmful chemicals and by preventing the growth of microorganisms

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Aprocrine sweat glands: o o o Simple Coiled Tubular glands that release their secretions into hair follicles at:     o Armpits (axillae) Nipples (areola) Groin (pubic region) Anus (anal region)

Cells were thought to secrete their product by an apocrine mechanism (meaning that the apical portion of the cell’s cytoplasm pinches off and along with cellular components of the apical region, becomes the secretory product 21

o o

Both sweat glands produce their secretions by exocytosis Secretory portion:  Apocrine gland has a much larger lumen than that of a merocrine gland

o

Secretion they produce:       Viscous Cloudy Composed of proteins and lipids that are acted upon by bacteria Producing a distinct, noticeable odor Influenced by hormones and may function in both signaling and communication Become active and produce secretory product after puberty

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Sebaceous glands  Holocrine glands o o o Discharge an oily Sebum – waxy secretion, usually into a hair follicle Sebum       Acts as a lubricant to keep the skin Hair from becoming dry Brittle Cracked Bactericidal (bacteria-killing) properties Folliculitis   Bacteria can cause an infection within the sebaceous gland and produce a local inflammation Furuncle (boil)   Blocked duct in a sebaceous gland often develops into a distinctive abscess Treated by lancing (cutting it open) to facilitate normal drainage and healing

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Other Integumentary glands:  Two important examples: o Ceruminous gland   Modified sweat glands located only in the external acoustic meatus Cerumen

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Secretion mixes with both sebum and exfoliated keratinocytes to form waterproof earwax

Simple Coiled Tubular glands with ducts leading to the surface of the skin Coils have a very large lumen and their gland cells contain many pigment granules and liquid droplets Functions:    Helps trap foreign particles or small insects Keeps them from reaching the eardrum Lubricates the external acoustic meatus and eardrum

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Mammary gland    Breasts are modified apocrine sweat glands Both males and females have it Products are controlled by a complex interaction between gonadal and pituitary hormones

   o o o o

Glands may open onto a single follicle by means of one or more short ducts Relatively inactive during childhood Activated during puberty in both sexes, when the production of sex hormones begins to increase

Originate from the invagination of the epidermis during embryological development Located in the dermis and may project through the epidermis to the surface Both nails and hair are composed primarily of dead “keratinized cells”

 Integument Repair and Regeneration Damaged tissues are normally repaired in one of two ways:   o     o o o Regeneration Fibrosis

Stages in wound healing: Cut blood vessels bleed into the wound Blood clot forms, and leukocytes clean wound Blood vessels regrow, and granulation tissue forms Epithelium regenerates, and connective tissue fibrosis occurs

 Aging of the Integument All components of the Integumentary system are affected by age in the following ways.  Development of the Integumentary System Integument development Nail development 23

o o o Cues:

Hair development Sebaceous and sweat gland development Mammary gland development

 Figure 5.1 – Layers of the integument  Figure 5.2 – Epidermal strata  Figure 5.3 – Thick skin and thin skin  Figure 5.4 – Production of melanin by melanocytes  Table 5.1 – Abnormal skin colors  Figure 5.5 – Friction ridges of thick skin  Figure 5.6 – Layers of the dermis  Figure 5.7 – Lines of cleavage  Table 5.2 – Layers of the integument and the subcutaneous layer  Figure 5.8 – Structure of a fingernail  Figure 5.9 – Hair  Figure 5.10 – Exocrine glands of the skin  Figure 5.11 – Stages in wound healing  Table 5.4 – Skin cancer  Figure 5.12 – Integument development  Figure 5.13 – Hair and gland development  Figure 5.14 – mammary gland development Summary:  What are the two major layers of the integument and the components of each?  What is the relationship between exposure to sunlight and the body’s need for vitamin D?  Why is the stratum spinosum important in maintaining the integrity of the skin?  Briefly describe the process of keratinization. Where does it begin? Why is it important?  What normal skin accessories are not present in thick skin?  How do melanocytes help protect the skin?  Briefly describe the structure of epidermal ridges and dermal papillae. What is the importance of each, and how do they interact?  What is indicated by the lines of cleavage in the skin, and why are they medically important?  Why must the circulation to the skin be closely regulated?  What are some functions of the subcutaneous layer?  Why does the lunula of the nail have a whitish appearance?  What stimulates the arrector pili muscle to contract?

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 Compare and contrast merocrine and apocrine sweat gland secretions.  What do sebaceous glands secrete?  What is the source of new epidermal cells and new dermal cells in the repair of the integument?

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