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BODY MEMBRANES AND SKIN Body Membranes Function of body membranes ◦ Line or cover body surface ◦ Protects body surfaces ◦ Lubricate body surfaces Classification of Body Membranes Epithelial membranes (3 types) 1. Cutaneous membrane (skin) • A dry membrane • Outermost protective boundary • Primary organ of the integumentary 2. Mucous membrane • Lines and protects organs that open to the exterior of the body • Found lining ducts and passageway of the respiratory and digestive tracts • Adapted for absorption or secretion Classification of Body Membranes 3. Serous membrane- lines body cavities and some organs that are not open to the external environment. • Parietal membrane- lines body cavities (wall paper) • Visceral membrane- covers the viscera(organs) • Important Serous Membranes • Pleura- surrounds a lung and lines the thoracic cavity • Peritonium- covers the abdominal viscera and lines the abdominal cavity • Pericardium- covers the heart Classification of Body Membranes Connective membranes • Do not contain epithelial components • Synovial membranes- lines the spaces between bone in joints • Have smooth and slick membranes that secret synovial fluid. • Reduces friction It’s Skin Deep: THE INTEGUMENTARY SYSTEM Dermatology Down Deep Dermotology: the branch of medicine dealing with the skin and its diseases,a unique specialty with both medical and surgical aspects. A dermatologist takes care of diseases, in the widest sense, and some cosmetic problems of the skin, scalp, hair, and nails. Integumentary System Skin (cutaneous membrane) Skin derivatives Sweat glands Oil glands Hairs Nails © Matt Dillard 2012 Layers of the skin Two main Layers Epidermis – outer layer Stratified squamous epithelium Often keratinized (hardened by keratin) Dermis Dense connective tissue Other Layers Dermoepidermal junction - connects the epidermis and dermis Deep to dermis is the hypodermis Not part of the skin Anchors skin to underlying organs Composed mostly of adipose tissue Also called the subcutaneous layer or superficial fascia Thick and Thin Skin Cells and Layers of Epidermis: Don’t judge this book by its cover. Cells in the Epidermis • Keratinocytes– produce the fibrous protein keratin. • Constitute more than 90% of cells present; principal structural element of the outer skin; • Undergo keratinization (cells lose their nucleus) • Keratin hardens and flattens the cells as they move outward and it waterproofs the skin. Photograph by Andrew Syred/Science Photo Library Cells in the Epidermis Melanocytes- pigment-producing cells (melanin) (5% of the total); contribute to skin color and filter ultraviolet (UV) light Cells in the Epidermis Epidermal dendritic cells- branched antigen presenting cells; play a role in activating immune response; also called Langerhans cells. Merkel cells – function as touch/tactile cells attach to sensory nerve endings to form “light touch” receptors Layers of the Epidermis Stratum corneum (horny) ◦ Most superficial layer, dead cells filled with keratin ◦ Barrier area Stratum lucidum (clear layer) ◦ cells filled with keratin precursors called eleidin; absent in thin skin. Stratum granulosum (granular layer) ◦ Cells arranged in two to four layers and filled with keratohyalin ◦ Contains high levels of lysosomal enzymes Layers of the Epidermis Stratum germinativum (growth layer) ◦ Stratum spinosum (spiny layer) Cells arranged in 8-10 layers made of desmosomes Rich in RNA ◦ Stratum basale (base layer) Single layer of columnar cells. Only cells undergo mitosis Migrate to the top and shed Dermoepidermal junction A basement membrane with unique fibrous elements and a polysaccharide gel “glue” the epidermis to the dermis below The junction is a partial barrier to the passage of some cells and large molecules Dermis: More Than Skin Deep Sometimes called “true skin”—much thicker than the epidermis and lies beneath it. Gives strength to the skin Serves as a reservoir storage area for water and electrolytes Contains various structures ◦ Arrector pili muscles and hair follicles (Figure 6-5) ◦ Sensory receptors (Figure 6-6) ◦ Sweat and sebaceous glands ◦ Blood vessels Rich vascular supply plays a critical role in temperature regulation Dermis: More Than Skin Deep Two layers Papillary layer o Projections called dermal papillae o Pain receptors o Capillary loops o Joins with the dermoepidermal junction to form finger prints. Reticular layer ( 80%) o Blood vessels o Glands o Nerve receptors o White collagenous fibers in this layer combine with elastics making skin tough yet stretchable (leather) Dermal Growth and Repair The dermis does not continually shed and regenerate itself as does the epidermis. Fibroblast form new connective fiber Scaring occurs Normal Skin Color Determinants Melanin o Yellow, brown or black pigments caused by melanin. o Amount of melanin produced depends upon genetic and exposure to sunlight Carotene o Orange-yellow pigment from some vegetables o usually hidden by the effects of melanin. Asians have little melanin which allows the yellow to show more than other nationalities. Hemoglobin o Red coloring from blood cells in dermis capillaries o Oxygen content determines the extent of red coloring Other Pigments in Skin Pinkish color o seen in fair-skinned persons because the vascular dermis is visible. Cyanosis blue look to skin due to poorly oxygenated blood Blushing o caused by dilation of blood vessels Pale by fright o caused by restriction of vessels Your turn to research Harry can have any type of skin cancer. Study the structures of the skin to best determine if Harry has developed skin cancer. Malfunctioning Melanocytes Albinism – melanocytes completely fail to secrete melanin. Hair, skin, and iris are white. Vitiligo – loss of pigment in certain areas of the skin producing white patches. Freckles and moles are formed when melanin becomes concentrated in local areas. Malignant melanoma – a cancerous change in a mole that may metastasize (spread) rapidly and is most difficult to treat. Exposure to sunlight increases risk. Response to Disease Jaundice – caused when bilirubin is deposited in skin because a diseased liver is unable to excrete this pigment Skin may appear bronzed due to the deposit of excess melanin when a person’s adrenal gland is functioning poorly. A bruise indicates that blood has escaped from the blood vessels and has clotted under the skin. Over eating carotene-rich vegetables such as carrots may cause skin to have a yellow tint. Skin Physiology Protects deeper tissues from: Mechanical damage Chemical damage Bacterial damage Thermal damage Ultraviolet radiation Desiccation Skin Function Aids in heat regulation Acts as a somatic sensory receptors Movement with out injury Aids in excretion of urea and uric acid Synthesizes vitamin D Homeostasis of body temperature Heat loss: approximately 80% of heat loss occurs through the skin; remaining 20% occurs through the mucosa of the respiratory, digestive, and urinary tracts (Figure 6-15) ◦ Evaporation: to evaporate any fluid, heat energy must be expended; this method of heat loss is especially important at high environmental temperatures when it is the only method heat can be lost from the skin ◦ Radiation: transfer of heat from one object to another without actual contact; important method of heat loss in cool environmental temperatures ◦ Conduction: transfer of heat to any substance in contact with the body; accounts for relatively small amounts of heat loss ◦ Convection: transfer of heat away from a surface by movement of air; usually accounts for a small amount of heat loss Skin Homeostatic Imbalance Infections Athletes foot Caused by fungal infection Boils and carbuncles Caused by bacterial infection Cold sores Caused by virus Skin Homeostatic Imbalance • Infections and allergies • Contact dermatitis • Exposures cause allergic reaction • Impetigo • Caused by bacterial infection • Psoriasis • Cause is unknown • Triggered by trauma, infection, stress Athlete’s Foot Boils Cold Sores Impetigo Psoriasis Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Dehydration Electrolyte imbalance Circulatory shock Severity of Burn Determined depth of lesion and percent of body surface “Rule of Palm”- Palm size of burnt victim is 1% “Rule of Nine”- body is divided into areas of 9% First-degree burns Only epidermis is damaged Skin is red and swollen Second degree burns Epidermis and upper dermis are damaged Skin is red with blisters Third-degree burns Destroys entire skin layer Burn is gray-white or black Critical burns Burns are considered critical if: Over 25% of body has second degree burns Over 10% of the body has third degree burns There are third degree burns of the face, hands, or feet Skin Cancer Cancer – abnormal cell mass Two types Benign Does not spread (encapsulated) Malignant Metastasized (moves) to other parts of the body Skin cancer is the most common type of cancer Skin Cancer Types Basal cell carcinoma Least malignant Most common type Arises from statum basale Squamous cell carcinoma Arises from stratum spinosum Metastasizes to lymph nodes Early removal allows a good chance of cure Skin Cancer Types Malignant melanoma Most deadly of skin cancers Cancer of melanocytes Metastasizes rapidly to lymph and blood vessels Detection uses ABCD rule ABCD Rule A = Asymmetry Two sides of pigmented mole do not match B = Border irregularity Borders of mole are not smooth C = Color Different colors in pigmented area D = Diameter Spot is larger then 6 mm in diameter Skin Structures Appendage of the Skin: Glands Sebaceous glands (all over except palms and soles of feet) Produce oil Lubricant for skin Kills bacteria Most with ducts that empty into hair follicles Glands are activated at puberty Acne – active infection of sebaceous glands Appendages of the Skin: Glands Sweat glands- Widely distributed in skin ◦ Eccrine- Open via duct to pore on skin surface ◦ Apocrine- Ducts empty into hair follicles Ceraminous- secrets cerumen (wax) and protects against dehydration Sweat and its Function Composition ◦ Mostly water ◦ Some metabolic waste ◦ Fatty acids and proteins (apocrine only) Function ◦ Helps dissipate excess heat ◦ Excretes waste products ◦ Acidic nature inhibits bacteria growth Odor is from associated bacteria Appendages of the Skin: Hair Dead keratinized cells Types ◦ Vellus – pale, fine body hair found in children and the adult female ◦ Terminal – coarse, long hair of eyebrows, scalp, axillary, and pubic regions Produced in the epidermis Hair Function and Distribution Functions ◦ Helping to maintain warmth ◦ Alerting the body to presence of insects on the skin ◦ Guarding the scalp against physical trauma, heat loss, and sunlight Hair is distributed over the entire skin surface except ◦ Palms, soles, and lips ◦ Nipples and portions of the external genitalia Hair structure Papillae- cluster of capillaries Root part of the hair embedded in dermis Shaft- visible part of hair ◦ Round – straight hair ◦ Oval- wavy hair ◦ Flat- curly or kinky hair Core ◦ Medulla- inner core ◦ Cortex outer portion Root hair plexus- knot of sensory nerve endings Hair Follicle Hair Thinning and Baldness Alopecia – hair thinning in both sexes True, or frank, baldness ◦ Genetically determined and sex-influenced condition ◦ Male pattern baldness – caused by follicular response to DHT Appendages of the Skin: Nails Consist of epidermal cells converted to hard keratin. Lack of pigment makes them colorless Nail Structures Free edge Body- visible part Root of nail- part of nail hidden by the fold of skin (cuticle) Lunula- moon shaped root area near root Nail bed- epithelium under nail Figure 4.9