Chapter 6 Key Terms 1 CallusDermis EpidermisHypodermis CortexMelanin Sebaceous GlandsSebum KeratinizationAlbinism Stratum GranulosumStratum Basale Stratum CorneumMelanocytes Stratum GerminativumDesmosomes

ANATOMY & PHYSIOLOGY CHAPTER 6: INTEGUMENTARY SYSTEM 2

Integumentary System  Integument means covering  Consists of the skin and its accessory structures  Hair, nails, glands in skin  Replaces itself about every 40 days  Has a rich blood supply  Almost completely waterproof and an effective barrier against most chemicals  Helps maintain homeostasis (water and temp)  Every square inch of skin contains app. 15 ft of blood vessels, 12 ft of nerves, 100 oil glands, 650 sweat glands, 1500 nerve endings 3

Integumentary System  Function  Senses environment  Regulates temperature  Protection  Excretion 4

Layers of Skin  Epidermis  Layer of epithelial tissue which can be further divided into sublayers  Outer layer of skin that lacks blood vessels  Made of stratified, squamous, keratinized epithelial cells  Cells are held together by desmosomes  These desmosomes are responsible for the flexibility, entirety, and continuous structure of skin 5

Epidermis  Keratinization  Cells become filled with keratin because the cells change shape and chemical composition and lose most of their water  The dead outer cells are constantly being shed  The process of keratinization produces distinct layers in the epidermis called strata or stratum  Composed of 5 layers 6

Epidermis  Stratum Corneum  Outermost layer  Cells have died and converted to protein  Keratin gives this layer the strength it needs to function properly  Functions as a physical barrier to light, heat, microorganisms, and most chemicals  Number of layers is determined by the stimulation on the surface  Excessive abrasion produces an area called a callus 7

Epidermis  Stratum Lucidum  Lies just below the stratum corneum  Only one or two cell layers thick  Cells are transparent and flat  Layers are sometimes so thin they can hardly be seen 8

Epidermis  Stratum Granulosum (granular layer)  A few layers of flattened cells  Cells lose their nuclei and become brittle  Granules in these cells do not contribute to skin color  Keratinization begins in this layer 9

Epidermis  Stratum Spinosum  Several layers of spiny shaped cells  The desmosomes are very prevalent in this layer  The cells have a spiny appearance 10

Epidermis  Stratum Germinativum  Deepest and most important layer  Contains the cells that are dividing by mitosis  Rests on the basement membrane  Sometimes also called stratum basale  As cells divide, the older cells are pushed up the different layers until they are eventually shed 11

Epidermis  Stratum Germinativum (cont’d)  Contains melanocytes which are responsible for producing the skins color (melanin)  Amount of melanin determines how dark someone’s skin will be  More melanin = darker skin  Exposure to the sun will cause melanocytes to produce more melanin  Moles and freckles are areas of larger melanin production  All races have the same number of melanocytes, but genes determines how active those melanocytes are 12

Epidermis  Certain regions of the skin do not have as many melanocytes  Many genes are responsible for skin color, yet one mutation can cause albinism  The absence of skin color because melanin is not produced by melanocytes  Skin is very white, hair is white, eyes pink 13

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Dermis  Also called corium  Dense connective tissue that connects skin to tissues beneath it  Contains blood vessels, nerves, sweat glands, sebaceous glands, hair follicles, and smooth muscles  2 parts of the dermis 15

Dermis  Papillary  Area adjacent to the epidermis  Contains papillae which extend up toward the epidermis  Reticular  Between papillary and subcutaneous layers  Subcutaneous (hypodermis)  Below dermis and compose of fat and muscle 16

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Hair  One of the main characteristics of mammals  Hair covers most of the body  The amount of hair a person develops is related to certain genetic factors  The hair follicle contains an outer sheath and an inner epithelial membrane that is continuous with the stratum germinativum  Root is found inside the hair follicle  Hair shaft is the visible portion of the hair 18

Hair  Purpose of the hair  Insulates  Filters  Shades  Prevents abrasion 19

Hair  Connected to the hair shaft is a bundle of smooth muscles  These muscles make the arrector pili muscle  This muscle causes the “goose bumps” on our skin when we get chills  Involuntary muscle that pulls on the hair follicle and causes the hair to stand on end 20

Hair  Growth  Cells near base of hair follicle divide by mitosis and push the older cells up to the surface  As the cells move upward, they are keratinized and form the layers of the hair shaft  Eventually the hair will fall out because a new hair is growing in the hair follicle  Baldness is a result of the hair follicles falling out as well 21

Hair  Color  Determined by genetic factors  These genetic factors determines not only the pigments in the hair shaft, but also when the hair will turn gray  Hair becomes gray/white when there is an absence of pigment in the cortex of the hair 22

Nails  Made of epidermal cells composed of very hard keratin  Lunula  White portion and the proximal edge of the nail  Size will vary with each individual (genetics)  Nail Bed  part of the nail where the nail grows  Nail grows approximately 1 mm per week 23

Sebaceous Glands  Located along the walls of hair follicles  Secrete sebum onto the root of the hair  Sebum is the oily substance that lubricates the surface of the skin  Under control of the endocrine system 24

Sweat Glands  Tubular glands found in the dermis of the skin  Consists of two portions  Secretory portion – located deep in the dermis  Excretory duct – opens to the surface of the skin  2 types of sweat glands  Eccrine  Apocrine 25

Sweat  Main component is sodium chloride  Other components include urea, uric acid, amino acids, ammonia, sugar…  Practically odorless  Aids in temperature control  Lips and genitalia lack sweat glands 26

Nerves  Corpuscles  Nerve endings  About 20 different types (heat, pain, pressure…)  Corpuscles sense those specific stimuli 27

Functions of Integumentary System  Sensation  Receptors (corpuscles) detect changes in external environment  These receptors connect to sensory neurons that transmit the impulse to the spinal cord and brain for interpretation  Allow us to react to the environment  Protection  Protects body from outside agents  Melanin protects body from harmful rays  “Acid Mantle” acts as a self-sterilizing area of the skin 28

Functions of Integumentary System  Thermoregulation  Blood vessels react to external temperatures (dilate or constrict)  Sweat takes heat away from body  Secretion  Sebum  Antifungal, antibacterial, moisturizes  Sweat  Cooling process, wastes  Aids in Vitamin D production 29