Ch. 6

 What is a tissue?  The integumentary system is a cutaneous membrane together with certain accessory organs

Four Major Types of Membranes 1. Serous membrane – line body cavities not open to outside  Consists of – simple squamous epithelium and thing layer of loose connective tissue  Secrete serous fluid (water, lubricates membrane surfaces

2. Mucous membranes – line cavities and tubes that open to outside  Made of epithelium over a layer of loose connective tissue  Includes goblet cells which secrete mucus

3. Synovial membrane – inner linings of joint cavities between ends of bones  Dense connective tissue over loose connective tissue and adipose tissue  Cells secrete thick, colorless synovial fluid which lubricates the end of bones

4. Cutaneous membrane – skin  One of the largest most versatile organs  Vital in maintaining homeostasis  Function – protective covering, helps regulate body temperature, retards water loss from deeper tissues, houses sensory receptors, synthesizes biochemicals, excretes wastes

Skin:

2 Layers  Epidermis – outer layer, stratified squamous epithelium w/ basement membrane  Dermis – inner layer, thicker, connective tissue (collagenous and elasitc fibers, epithelial tissue, smooth muscle tissue, nervous tissue, blood)

 Beneath - Subcutaneous layer - loose connective and adipose tissues *** skin of a 150 lb person spread flat would cover about 20 square ft ***

EPIDERMIS  Lacks blood vessels  Stratum basale – deepest layer, close to dermis, nourished by dermal blood vessels  When it divides it pushes older cells toward skin surface (farther away, less nutrients  die)

Keratinization  Keratinization – older cells (keratinocytes) harden, cytoplasm fill with tough, fibrous, waterproof keratin protein  Forms outer layer stratum corneum which is eventually shed

thickness varies from region to region  most areas have just 4 layers  stratum basale  stratum spinosum  stratum granulosum – missing where epidermis is thin  stratum lucidum – palms and soles  Stratum corneum

Stratum Corneum

 Stratum lucidum  Stratum granulosum

 Stratum spinosum  Stratum basale  Skin cell production is balanced with the loss of dead cells  Calluses and corns are the result of increased cell division where skin is rubbed or pressed regularly

Epidermis continued  Functions  Protection  Shields from excessive water loss, mechanical injury, and harmful chemicals  Unbroken it protects against microorganisms

Skin Color  Skin Color is caused by: Skin Color is caused by:  Melanin – a dark pigment that provides skin color – is produced by melanocytes in the epidermis  Protects from ultraviolet radiation, preventing mutations and other damage

Skin color cont.  All people have the same number of melanocytes  How do we have different skin colors?  Differences in melanin production  Size of pigment granules

Environmental Effects on Color  Sunlight, UV light from sun lamps, and X-rays stimulate production of melanin  Blood can affect skin color  Diet and chemicals can effect skin color

Dermis  The boundary between the dermis & epidermis is uneven  Fingerprints are formed from these and determine by genes

Dermis continued  Composed of dense connective tissue  collagenous & elastic fibers w/ a gel-like matrix  Dermal blood vessels supply nutrients to all skin cells  Pressure ulcer  Nerve cells processes (endings) found throughout  Contains hair follicles, sebaceous glands, and sweat glands

Subcutaneous Layer  Also called the hypodermis  Consists of loose connective and adipose tissues, and major blood vessels  Connective tissue is continuous with the dermis so there is no sharp boundary  Adipose tissue insulates

Skin Quiz 1. List 4 of the possible 5 layers of the epidermis. 2. Keratinization is the process in which: 3. Melanin is: 4. True or False, dermal blood vessels can effect the color of your skin. 5. What are 5 things (tissues or organs) that you would find in the dermis?

Accessory Organs of the Skin Hair Follicles Every hair develops from a group of epidermal cells at the base of a hair follicle As the cells divide they push older cells away that become keratinized and make up the shaft Genes determine hair color trichosiderin – red hair

Hair Follicles cont…  Each hair has a muscle (arrector pili) attached to it that when it contract causes the hair to stand on end

Sebaceous Glands  Contain groups of specialized epithelial cells and are usually associated with hair follicles  Holocrine gland – secrete oily mix of fatty material and cellular debris (sebum)  Keeps hair and skin soft, pliable and waterproof

Nails  Protective coverings on the ends of fingers and toes  Parts – nail plate and nail bed, lunula  Epithelial cells  Continuous with skin divide and become keratinize

Sweat Glands (sudoriferous)  Sweat glands Sweat glands  Exocrine glands that form a ball shaped coil deep in the dermis  Coiled portion is made of epithelial cells which secrete sweat (water, salt and wastes)  Eccrine gland – most numerous; respond to elevated body temperature  Common in the forehead, neck, and back

Sweat Glands cont…  Apocrine glands – activated by emotional upset, fear, or pain; most numerous in axillary regions and groin; similar to eccrine gland  Modified sweat glands  Ceruminous gland – secrete ear wax  Mammary gland – secrete milk

Accessory Organs Quiz 1. Explain how the hair that leaves the hair follicle is dead. 2. Sebaceous glands secrete an oily mixture called ____________. 3. Which type of cells divide to give rise to the nail plate? 4. Sebaceous gland are usually associated with ______ __________. 5. Sweat glands secret ____, _____, and _____.

Regulation of Body Temperature  The skin plays a key role in the homeostatic mechanism that regulates body temperature.  Releasing heat  By blood – vasodilation stimulated by hypothalamus  Eccrine sweat glands are activated

 Conserving heat  Vasoconstriction of dermal blood vessels  Inactive sweat glands  Skeletal muscles contract slightly and cell respiration produces heat  Shivering  Most of the bodies heat is lost through the head.

Healing of Wounds  Wounds Heal Wounds Heal  Inflammation  Blood vessels dilate and become more permeable  The healing process depends of the extent of the injury  Epidermis – epithelial cells divide more rapidly and fill in the gap  Dermis/hypodermis – blood clots form and make a scab  Fibroblasts migrate and produce collageneous fibers  Blood vessels extend into the area  Phagocytic cells remove dead cells and debris

 Large, open wounds  Granulations form  New branch of a blood vessel and a cluster of fibroblasts  Blood vessels and fibroblasts eventually migrate away and a scar is left

 Acne – Disease of the sebaceous glands that produces blackheads and pimples(acne)acne  Athlete’s foot – Fungus infection usually in the skin of the toes and soles  Birthmark – congenital blemish or spot on the skin, visible at birth or soon after  Dermatitis – inflammation of the skin  Erythema – reddening of the skin due to dilation of dermal blood vessels in response to injury or inflammation

 Herpes – infectious disease of the skin, usually caused by the herpes simplex virus and characterized by recurring formations of small clusters of vesicles  Mole – fleshy skin tumor (nevus) that is usually pigmented; colors range from brown to black  Scabies – disease resulting from an infestation of mites

 Skin Biopsy Skin Biopsy  Pressure Ulcer Pressure Ulcer

 Eczema – noncontagious skin rash that produces itching, blistering, and scaling ( Eczema) Eczema  HowStuffWorks Videos "DNA Damage from UV Rays“ HowStuffWorks Videos "DNA Damage from UV Rays“  HowStuffWorks Videos "Targeting Cancer Cells with New Drugs“ HowStuffWorks Videos "Targeting Cancer Cells with New Drugs“  Wart – flesh-colored, raised area caused by a viral infection