Chapter 18 - Lecture notes 18 PDF

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Chapter 18 lecture notes for EHS 115...

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Chapter 18

● Functions Integumentary System ○ Integumentary system → is made up of the skin and its related structures ○ Functions of the Skin ■ Skin = forms the protective outer layer covering the external surfaces of the entire body. ○ Functions of Related Structures ■ Sebaceous glands = secrete sebum (oil) that lubricates the skin and discourages the growth of bacteria on the skin. ■ Sweat glands = help regulate body temperature and water content by secreting sweat; a small amount of metabolic waste is also excreted. ■ Hair = helps control the loss of body heat ■ Nails = protect the dorsal surface of the last bone of each toe and finger ● The Structures Of The Skin And Its Related Structures ○ The Skin ■ Cutaneous = pertaining to the skin (cutane → skin) ■ Epidermis = the outermost layer of the skin; made up of several specialized epithelial tissues; does not contain any blood vessels or connective tissue. ● Epithelial tissues = form a protective covering for all of the internal and external surfaces of the body. ● Squamous epithelial tissue = forms the upper layer of the epidermis; consists of flat, scaly cells that are continuously shed (squamous → scale-like)

● Basal layer = lowest layer of the epidermis; new cells are produced here and then pushed upward; when these cells reach the surface, they die and become filled with keratin. ● Keratin = a fibrous, water-repellent protein; soft keratin is a primary component of the epidermis while hard keratin is found in the hair and nails. ● Melanocytes = special cells that are also found in the basal cell layer; they produce and contain a dark brown to black pigment known as melanin. ● Melanin = the pigment that determines the color of the skin, which depends upon the type and amount of this pigment that is present; also produces spots of color such as freckles and age spots. ■ Dermis (corium) = the thick layer o living tissue directly below the epidermis; contains connective tissue, blood and lymph vessels, and nerve fibers; hair follicles, sebaceous glands, and sweat glands are also found in the dermis. ■ Sensory nerve endings = the sensory receptors for stimuli such as touch, temperature, pain, and pressure. ■ Collagen = tough yet flexible fibrous protein material found in the skin and also in the bones, cartilage, tendons, and ligaments. ■ Mast cells = found in the connective tissue of the dermis; respond to injury, infection, or allergy by producing and releasing substances, including heparin and histamine.

■ Heparin = released in response to an injury; is an anticoagulant (anticoagulant → prevents blood clotting) ■ Histamine = released in response to allergens; causes the signs of an allergic response, including itching and increased mucus secretion. ■ Subcutaneous layer = located just below the layers of the skin and connects the skin to the surface muscles. ● Adipose tissue = tissue that is made up of fat ● Lipocytes (fat cells) = predominant in the subcutaneous layer where they manufacture and store large quantities of fat. ○ The Sebaceous Glands ■ Sebaceous glands = located in the dermis layer of the skin and are closely associated with hair follicles. ● Sebum = an oily substance that is released through ducts opening into the hair follicles; from the sebaceous glands, the sebum moves onto the surface and lubricates the skin. ○ The Sweat Glands ■ Sweat glands (sudoriferous glands) = tiny, coiled glands found on almost all body surfaces; two types: apocrine glands, which are found at hair follicles, and eccrine glands which open onto the skin and are most numerous in the palms of thehands, the soles of the feet, and forehead. ● Pores = openings on the surface of the skin that act as the ducts of the sweat glands. ● Perspiration (sweat) = secreted by sweat glands and is made up of 99% water plus some salt and metabolic waste products. ● Hidrosis = the production and excretion of perspiration

● Mammary glands = modified sweat glands which produces milk; also part of the reproductive system. ○ The Hair ■ Hair = rod-like structures composed of tightly fused, dead protein cells filled with hard keratin; darkness and color of the hair is determined by the amount and type of melanin produced by the melanocytes that surround the core of the hair shaft. ● Hair follicles = sacs that hold the root of the hair fibers; shape of the follicle determines whether the hair is straight or curly. ● Arrector pili = tiny muscle fibers attached to the hair follicles that cause the hair to stand erect; in response to cold or fright, these muscles contract, causing raised areas of skin known as goose bumps. ○ The Nails ■ Unguis (fingernail/toenail) = the keratin plate that protects the dorsal surface of the last bone of each finger and toe. ● Lunula = pale half-moon shaped region at every nail root; it is the active area of the nail, where new keratin cells form (lun → moon) ● Cuticle = a narrow band of epidermis attached to the surface of the nail just in front of the root, protecting the new keratin cells as they form. ● Nail root = fastens the nail to the finger or toe by fitting into a groove in the skin. ● Medical Specialties Related To The Integumentary System ○ Dermatologist = physician who specializes in diagnosing and treating disorders of the skin.

○ Plastic surgeon = physician who specializes in the surgical restoration and reconstruction of body structures. ● Pathology Of The Integumentary System ○ The Sebaceous Glands ■ Acne vulgaris (acne) = chronic inflammatory disease characterized by pustular eruptions of the skin caused by an overproduction of sebum around the hair shaft; triggered by hormones in puberty and adolescence, but also occurs in adults. ■ Comedo = noninfected lesion formed by the buildup of sebum and keratin in a hair follicle often associated with acne vulgaris. ● Whitehead → a comedo with an obstructed opening ● Blackhead → a sebum plug that is exposed to air often oxidizes and forms this. ■ Epidermoid cyst (sebaceous cyst) = a closed sac that is found just under the skin; sacs contain yellow, fatty material and are usually found on the face, neck, or trunk. ■ Seborrhea = overactivity of the sebaceous glands that results in the production of an excessive amount of sebum ■ Seborrheic dermatitis = inflammation sometimes resulting from seborrhea that causes scaling and itching of the upper layers of the skin or scalp. ■ Seborrheic keratosis = a benign skin growth that has a waxy or “pasted-on” look; can vary in color from light tan to black; occurs most commonly in the elderly. ○ The Sweat Glands

■ Anhidrosis = abnormal condition of lacking sweat in response to heat (hidr → sweat) ■ Diaphoresis = profuse sweating; it is a normal condition when brought on by heat or exertion but can also be the body's response to emotional or physical distress. ■ Heat rash (prickly heat) = intensely itchy rash caused by blockage of the sweat glands by bacteria and dead cells. ■ Hyperhidrosis = condition of excessive sweating in one area or over the whole body. ■ Sleep hyperhidrosis (night sweats) = occurrence of hyperhidrosis during sleep; many potential causes, including menopause, certain medications, and some infectious diseases. ○ The Hair ■ Folliculitis = inflammation of the hair follicles; especially common on arms, legs, and in the beard area of men. ■ Trichomycosis axillaris = superficial bacterial infection of the hair shafts in areas with extensive sweat glands, such as the armpits (trich/o → hair) ■ Hirsutism = the presence of excessive body and facial hair in women, usually occurring in a male pattern (hirsut → hairy); can be hereditary or caused by a hormonal imbalance. ■ Alopecia = the partial or complete loss of hair, most commonly on the scalp (alopec → baldness)

■ Alopecia areata = autoimmune disorder that attacks the hair follicles, causing well-defined bald areas on the scalp or elsewhere on the body; often begins in childhood. ■ Alopecia totalis = uncommon condition characterized by the loss of all the hair on the scalp. ■ Alopecia universalis = the total loss of hair on all parts of the body ■ Androgenic alopecia = most common type of hair loss (androgenic → referring to androgens → hormones involved in the development and maintenance of masculine characteristics) ● Men → male pattern baldness ○ Hairline recedes from the front to the back until only a horseshoe-shaped area of hair remains in the back and at the temples. ● Female → female pattern baldness ○ Hair thins in thefront and on the sides of the scalp and sometimes on the crown. ○ The Nails ■ Clubbing = abnormal curving of the nails that is often accompanied by enlargement of the fingertips; can be hereditary but is usually caused by changes associated with oxygen deficiencies related to coronary or pulmonary diseases such as lung cancer. ■ Koilonychia (spoon nail) = malformation of the nails in which the outer surface is concave or scooped out like the bowl of a spoon (koil → hollow or concave); often an indication of iron-deficiency anemia.

■ Onychia (onychitis) = inflammation of the bed of the nail that often results in the loss of the nail (onych → fingernail/toenail) ■ Onychocryptosis (ingrown toenail) = the edges of a toenail, usually on the big toe, curve inward and cut into the skin; the affected area is prone to inflammation or infection. ■ Onychomycosis = fungal infection of the nail; depending on the type of fungus involved, this condition can cause the nails to turn white, yellow, green, or black and to become thick or brittle. ■ Paronychia = an acute or chronic infection of the skin fold around a nail (par → near) ○ Skin Pigmentation ■ Acanthosis nigricans = condition where one or more areas of the skin develop dark, wart-like patches; can be a sign of a disease such as cancer or type 2 diabetes or a reaction to a medication. ■ Age spots (solar lentigines/liver spots) = discolorations caused by sun exposure; even though they are harmless, they sometimes resemble skin cancer growths. ■ Albinism = genetic condition characterized by a deficiency or the absence of pigment in the skin, hair, and irises of the eyes (albin → white); is the result of a missing enzyme that is necessary for the production of melanin; person with this condition is known as an albino. ■ Chloasma (melasma/mask of pregnancy) = pigmentation disorder characterized by brownish spots on the face; can occur

during pregnancy, especially among women with dark hair and fair skin, and usually disappears after delivery. ■ Vitiligo = skin condition resulting from the destruction of the melanocytes due to unknown causes; causes irregular patches of white skin, a process known as depigmentation; hair growing in an affected area may also turn white. ○ Bleeding into the Skin ■ Contusion = an injury to underlying tissues without breaking the skin and is characterized by discoloration and pain (contus → bruise); discoloration is caused by an accumulation of blood within the skin. ■ Ecchymosis (bruise) = a large, irregular area of purplish discoloration due to bleeding under the skin (ecchym → pouring out of juice) ■ Purpura = the appearance of multiple purple discolorations on the skin caused by bleeding underneath the skin (purpur → purple) ■ Petechiae = very small, pinpoint hemorrhages that are less than 2 mm in diameter; sometimes result from high fevers. ■ Hematoma = a swelling of clotted blood trapped in the tissues; usually caused by an injury; body eventually reabsorbs this blood. ○ Surface Lesions ■ Lesion = a pathologic change of the tissues due to disease or injury ● Crust (scab) = a collection of dried serum and cellular debris

● Erosion = the wearing away of a surface, such as the epidermis of the skin or the outer layer of a mucous membrane. ● Macule (macula) = a discolored flat spot that is less than 1 cm in diameter (example: freckles) ● Nodule = a solid, raised skin lesion that is larger than 0.5 cm in diameter and deeper than a papule. ● Papule = a small, raised red lesion that is less than 0.5 cm in diameter and does not contain pus. ● Plaque = a scaly, solid raised area of closely spaced papule ● Scales = flakes or dry patches made up of excess dead epidermal cells; excessive shedding is associated with skin disorders such as psoriasis. ● Verrucae (warts) = small, hard skin lesions caused by the human papillomavirus. ● Wheal (welt) = a small bump that itches ○ Fluid-Filled Lesions ■ Abscess = a closed pocket containing pus that is caused by a bacterial infection; can appear on the skin or within other structures of the body. ■ Purulent = producing or containing pus ■ Exudate = a fluid, such as pus, that leaks out of an infected wound

■ Cyst = an abnormal sac containing gas, fluid, or a semisolid material; most common type of skin cyst is a sebaceous cyst. ■ Pustule (pimple) = a small, circumscribed lesion containing pus; can be caused by acne vulgaris, impetigo, or other skin infections. ■ Vesicle = a small blister, less than 0.5 cm in diameter, containing watery fluid. ■ Bulla = a large blister that is usually more than 0.5 cm in diameter ○ Lesions Through the Skin ■ Abrasion = an injury in which superficial layers of skin are scraped or rubbed away. ■ Fissure = a groove or crack-like break in the skin ■ Laceration = a torn or jagged wound or an accidental cut wound ■ Pressure sore (decubitus ulcer/bedsore) = an open ulcerated wound that is caused by prolonged pressure on an area of skin; if untreated, it can be seriously infected and cause tissue death. ■ Needlestick injury = an accidental puncture wound caused by a used hypodermic needle, potentially transmitting an infection. ■ Ulcer = an open lesion of the skin or mucous membrane resulting in tissue loss around the edges. ○ Birthmarks

■ Pigmented birthmarks = include nevi, also known as moles, as well as café-au-lait spots and other irregularities in skin color. ■ Vascular birthmarks (salmon patches/red birthmarks) = caused by blood vessels close to the skin's surface; most common type of birthmark. ■ Capillary hemangioma (strawberry birthmark) = a soft, raised, pink or red vascular birthmark (hemangioma → benign tissue mass made up of newly formed small blood vessels that in ● Exanthem = a widespread rash, usually in children (rash → breaking out, or eruption, that changes the color or texture of the skin) ● Hand, foot, and mouth disease = mild viral infection common in children under 5 years of age; characterized by sores in the mouth and throat and a rash on the hands and feet. ○ General Skin Medications ■ Dermatosis = skin lesions or eruptions of any type that are not associated with inflammation. ■ Ichthyosis = group of hereditary disorders characterized by dry, thickened, and scaly skin (ichthy → dry or scaly); caused either by the slowing of the skin's natural shedding process or by a rapid increase in the production of the skin's cells. ■ Lipedema (painful fat syndrome) = chronic abnormal condition that is characterized by the accumulation of fat and fluid in the tissues just under the skin of the hips and legs; usually affects

women and even with weight loss this localized excess fat does not go away. ■ Systemic lupus erythematosus (lupus) = an autoimmune disorder characterized by a red, scaly rash on the face and upper trunk; in addition to the skin, this condition also attacks the connective tissue in other body systems, especially in the joints. ■ Psoriasis = common skin disorder characterized by flare-ups in which red papules covered with silvery scales occur on the elbows, knees, scalp, back, or buttocks. ■ Rosacea (adult acne) = characterized by tiny red pimples and broken blood vessels; usually develops in individuals with fair skin between 30 and 60 years of age. ■ Rhinophyma (bulbous nose) = usually occurs in older men; characterized by hyperplasia (overgrowth) of the tissues of the nose and is associated with advanced rosacea. ■ Scleroderma = an autoimmune disorder in which the connective tissues become thickened and hardened, causing the skin to become hard and swollen; can also affect the joints and internal organs. ■ Urticaria (hives) = itchy wheals caused by an allergic reaction (urtic → rash) ■ Xeroderma (xerosis) = excessively dry skin ○ Bacterial Skin Infections ■ Carbuncle = a cluster of connected furuncles (boils)

■ Cellulitis = an acute, rapidly spreading bacterial infection within the connective tissues that is characterized by malaise, swelling, warmth, and red streaks. ■ Furuncles (boils) = large, tender, swollen areas caused by a staphylococcal infection around hair follicles or sebaceous glands. ■ Gangrene = death of tissue; caused by a loss of circulation to the affected tissues; tissue death is followed by bacterial invasion that causes putrefaction, and if this infection enters the bloodstream, it can be fatal (putrefaction → decay that produces foul-smelling odors) ■ Impetigo = a highly contagious bacterial skin infection that commonly occurs in children; characterized by isolated pustules that become crusted and rupture. ■ Necrotizing fasciitis = a severe infection caused by group A strep bacteria, which are also known as flesh-eating bacteria. ■ Pyoderma = any acute, inflammatory, pus-forming bacterial skin infection such as impetigo. ○ Fungal Skin Infections ■ Mycosis = any abnormal condition or disease caused by a fungus ■ Tinea (ringworm) = fungal infection that can grow on the skin, hair, or nails. ○ Parasitic Skin Infestations ■ Infestation = the dwelling of microscopic parasites on external surface tissue; some parasites live temporarily on the skin while others lay eggs and reproduce there.

● Pediculosis (lice) = an infestation with lice (pedicul → lice) ● Scabies = a skin infection caused by an infestation of itch mites; itch mites cause small, itchy bumps and blisters by burrowing into the top layer of human skin to lay their eggs. ○ Skin Growths ■ Callus = thickening of part of the skin on the hands or feet caused by repeated rubbing. ■ Cicatrix = a normal scar resulting from the healing of a wound ■ Granulation tissue = the tissue that normally forms during the healing of a wound; this tissue eventually forms the scar. ■ Granuloma = small, knot-like swelling of granulation tissue in the epidermis; can result from inflammation, injury, or infection. ■ Keloid = an abnormally raised or thickened scar that expands beyond the boundaries of the original incision (kel → growth or tumor); often inherited and is more common among people with dark-pigmented skin. ■ Keratosis = any skin growth, such as a wart or a callus, in which there is overgrowth and thickening of the skin (kerat → hard or horny) ■ Lipoma = benign, slow-growing fatty tumor located between the skin and the muscle layer; is usually harmless, and treatment is rarely necessary unless the tumor is in a bothersome location, is painful, or is growing rapidly.

■ Nevus (mole) = small, dark skin growth that develops from melanocytes in the skin. ■ Dysplastic nevi = atypical moles that can develop into skin cancer ■ Papilloma = benign, superficial, wart-like growth on the epithelial tissue or elsewhere in the body, such as in the bladder. ■ Polyp = mushroom-like growth from the surface of a mucous membrane, such as a polyp in the nose; growths have many causes and are not necessarily malignant. ■ Skin tags = small, flesh-colored or light-brown polyps that hang from the body by fine stalks; are benign and tend to enlarge with age. ○ Skin Cancer ■ Skin cancer = malignant growth on the skin which can have many causes, including repeated severe sunburns or long-term exposure to the sun; three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma. ● Actinic keratosis (solar keratosis) = precancerous skin growth that occurs on sun-damaged skin (precancerous → a growth that is not yet malignant); often looks like a red, tan, or pink scaly patch and feels like sandpaper; if not treated, it will become malignant. ● Basal cell carcinoma = malignant tumor of the basal cell layer of the epidermis; most common and least harmful type of skin cancer because it is slow growing and rarely spreads to other parts of the body; occur mainly on the face or neck and tend to bleed easily; are usual...