Skin and the Integumentary System Chapter 6

Introduction An organ is two or more tissues grouped together and performing specialized functions The cutaneous membrane (skin) together with certain accessory organs make up the integumentary system

Integumentary system http://methiscool.files.wordpress.com/2012/04/cross-section.png

Types of Membranes Serous membranes – line body cavities that lack openings to the outside Form inner linings of thorax and abdomen (visceral and parietal) Cover the organs within these cavities Secretes watery serous fluid, which lubricates membrane surfaces

Serous membranes http://www.daviddarling.info/images/serous_membranes.jpg

Mucous membranes – line cavities and tubes that open to the outside of the body Include oral, nasal, and tubes of the digestive, respiratory, urinary, and reproductive systems Secrete mucous from goblet cells http://classconnection.s3.amazonaws.com/998/flashcards/60998/jpg/membranes_-_mucous21341005104874.jpg

Synovial membranes – form the inner linings of the joint cavities between the ends of bones at freely movable joints (synovial joints) Secrete a synovial fluid which lubricates the ends of bones within the joint http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Illu_synovial_joint.jpg/250px-Illu_synovial_joint.jpg

Cutaneous membrane - skin http://www.edzone.net/~fulton/high/winkler/team3/The%20Integumentary%20System_files/image003.jpg

Skin and its tissues What it does: Maintains homeostasis Protective covering Regulates body temp Prevents water loss from deeper tissues Houses sensory receptors Creates biochemicals Excretes small quantities of wastes

Has two distinct tissue layers: Epidermis – outer layers Made of stratified squamous epithelium Dermis – inner layer Thicker than the epidermis and contains all other types of tissue Beneath that is the subcutaneous layer which contains loose connective tissue and adipose tissue that connects it to organs

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Epidermis Made of stratified squamous epithelium and lacks blood vessels As the cells of the lower layer (stratum basale) divide they get pushed upward towards the surface and divide These cells harden by the protein keratin filling into the cell membrane – Keratinization This forms the outermost layer (stratum corneum)

The loss of skin cells is equal to the death in healthy skin Rate of cell division increases in skin that is rubbed or pressed a lot (causes calluses or corns-keratinized masses on toes) Functions: shields excessive water loss, mechanical injury and harmful chemicals, also keeps out disease-causing organisms when not cut

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Skin color Melanocytes are specialized cells in the epidermis which produce melanin, a dark pigment that provides skin color They also absorb UV radiation in sunlight which prevents mutations and damaging effects Located in deepest layer of epidermis

http://www.mayoclinic.com/images/image_popup/sn7_skinlayers.jpg

All people have the same # of melanocytes but the amount of melanin that they produce varies Mostly genetically determined…more melanin produced, darker the skin Sun causes additional pigment to be produced

sciencedaily.com

Dermis (fun fact) The dermal papillae is uneven which causes fingerprints This is due to genes and when the fetus presses against the uterine wall skincarebylouisa.com

Dermis Binds the epidermis to underlying tissues Made of dense connective tissue with collagenous and elastic fibers which gives skin toughness and elasticity Filled with blood vessels which supply nutrients and also regulate body temperature

Also has nerve cells throughout which send impulses to sensory receptors (like touch) It also contains hair follicles, sebaceous glands (oil producing), and sweat glands

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Subcutaneous layer Beneath dermis and consists of loose connective and adipose tissue No sharp boundary separates these two layers Adipose helps insulate the body This layer also contains the major blood vessels that supply the skin and underlying adipose tissue

health.rush.edu

Accessory organs of the skin: Hair Follicles Hair is present except on the palms, soles, lips, nipples, and parts of reproductive organs Hair follicle – tubelike depression in the skin in which hair develops Hair is composed of dead epithelial cells that develop in the dermis and get pushed toward surface and keratinized

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A bundle of smooth muscle cells (arrector pili muscle) attaches to each hair follicle and contracts which makes hair stand up (goose bumps) http://www.ivy-rose.co.uk/HumanBody-Images/Structure_of_Skin/Arrector-Pili-Muscle.jpg

Sebaceous gland Contain groups of specialized epithelial cells that secrete an oily mixture through ducts in hair follicle Sebum is the mixture and it helps keep the hair and skin soft, pliable, and waterproof http://www.umm.edu/graphics/images/en/19666.jpg

Nails Protective coverings on the ends of the fingers and toes made of keratinized epithelial cells Made of a nail plate and overlies a nail bed The lunula makes up the base of the nail plate and that is where the nail grows

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Sweat glands Exocrine glands made of a tube that starts in the subcutaneous layer and is lines with sweat-secreting epithelial cells Two types: Eccrine glands-respond to body temp, common in areas of lots of sweat (forehead) Carried by a duct out a pore in the skin Apocrine glands-active when a person is emotionally upset, frightened, or in pain (ear wax and mammary glands are modified sweat glands)

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Regulation of body Temperature If too hot: hypothalamus has muscles in the blood vessels relax and dilate (vasodilatation) which causes heat to leave blood through skin Eccrine glands release sweat (evaporation cools skin) If too cold: Muscles next to blood vessels contract which causes (vasoconstriction) and less heat loss Sweat glands are inactive If keeps getting worse, skeletal muscles are forced to contract which increases cellular respiration and produces heat (shivering)

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Healing of Wounds Inflammation – when a wound an the area surrounding it become red and painfully swollen in response to injury or stress Inflamed skin may become reddened, warm, swollen, and painful Blood vessels dilate which allows more blood to flow to that area with helpful nutrients and oxygen

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If break in skin is shallow: Epithelial cells are stimulated to divide and new cells fill the gap If injury extends into the dermis or deeper: 1.Blood vessels break and blood clots (forms scab) 2.Fibroblasts come and form new collagenous fibers that bind wound together 3.Blood vessels come back and phagocytic cells remove dead cells and other debris 4.Scab falls off and if wound is bad it forms a scar

Integumentary system review Video