MED TERM Chapter 7 - Lecture notes dermatology PDF

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full lecture notes on dermatology (chapter 7)...

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MEDICAL TERMINOLOGY: Chapter 7 Dermatology

Objectives of Chapter 7: 1. Identify structures of the integumentary system. 2. b v b j∆˚vkjDescribe the process of an allergic reaction. 3. Describe common integumentary diseases, laboratory and diagnostic procedures, medical and surgical procedures, and drugs. 4. Form the plural and adjective forms of nouns related to dermatology. 5. Give the meanings of word parts and abbreviations related to dermatology. 6. Divide dermatology words and build dermatology words. 7. Spell and pronounce dermatology words. 8. Research sound-alike and other dermatology words. 9. Analyze the medical content and meaning of a dermatology report.

Anatomy and Physiology The integumentary system is an extremely large, flat, flexible body system that covers the entire surface of the body. The integumentary system includes the skin (epidermis and dermis), sebaceous glands, sweat glands, hair, and nails. In addition, this chapter discusses the subcutaneous tissue, a layer of connective tissue that is beneath the skin. The purpose of the integumentary system is to protect the body; it is the body’s first line of defense against invading microorganisms. The sense of touch is also part of the integumentary system.

Anatomy of the Integumentary System Skin The skin or integument consists of two different layers: the epidermis and the dermis. The epidermis is categorized as epithelium or epithelial tissue. The epithelium covers the external surface of the body. Besides the skin, the epithelium also includes the mucous membranes that line the walls of internal cavities that connect to the outside of the body. The dermis is categorized as connective tissue. Epidermis The epidermis is the thin, outermost layer of the skin. The most superficial part of the epidermis contains dead cells that have no nuclei and are filled with keratin , a hard, fibrous protein. These cells form a protective layer, but they are dead cells, and so they are constantly being shed or sloughed off. This process is known as exfoliation . In contrast, the deepest part or basal layer of the epidermis is composed of living cells that are constantly dividing and moving to the surface. The epidermis does not contain any blood vessels. It receives nutrients and oxygen from the blood vessels in the dermis.

The epidermis also contains melanocytes, pigment cells that produce melanin, a dark brown or black pigment. Melanin in the epidermis absorbs ultraviolet light from the sun to protect the DNA in skin cells from undergoing genetic mutations. Dermis The dermis is a thicker layer beneath the epidermis. It is both firm and elastic because it contains collagen fibers (firm, white protein) and -elastin fibers (elastic, yellow protein). The dermis contains arteries, veins, and nerves, as well as hair follicles, sebaceous glands, and sweat glands. A dermatome is a specific area on the skin that sends sensory information through a nerve to the spinal cord. Sebaceous Glands The sebaceous glands in the dermis are a type of exocrine gland . They secrete sebum through a duct that goes into a hair follicle. Sebum consists of oil that coats and protects the hair shaft to keep it from becoming brittle. Sebaceous glands are also known as oil glands. Sweat Glands The sweat glands in the dermis are also exocrine glands. The sweat gland duct opens onto the surface of the skin through a pore. Sweat contains water, sodium, and small amounts of body waste (ammonia, creatinine, urea). It is sodium that gives sweat its salty taste. Sweating helps to regulate the body temperature. When the body is hot, temperature receptors in the skin send impulses to the hypothalamus in the brain, which then signals the sweat glands to secrete sweat. Water in the sweat evaporates from the skin and cools the body. Also, blood vessels in the dermis dilate, and heat from the blood radiates out from the body. Although sweat is odorless, bacteria on the surface of the skin digest sebum and sweat, and their waste products cause the odor associated with sweat. The process of sweating and the sweat itself are both known as perspiration . The sweat glands are also known as the sudoriferous glands. Hair Hair covers most of the body, although its consistency and color vary from one part of the body to another and from one person to the next. Additional facial, axillary, and pubic hairs appear during puberty. Each hair forms in a hair follicle in the dermis. Melanocytes give color to the hair. Hair cells are filled with keratin, which makes the hair shaft strong. Usually, the hair lies flat on the surface of the skin, but when the skin is cold, a tiny erector muscle at the base of the hair follicle contracts and causes the hair to stand up (piloerection ). The contracted muscle forms a goosebump. In furry animals, the erect hairs create an insulating layer and trap heat near the skin, but this effect is insignificant in humans. Nails The nails cover and protect the distal ends of the fingers and toes because these areas are easily traumatized. Each nail consists of several parts. The outer layer—the hard, opaque nail plate—is composed of dead cells that contain keratin. The nail plate rests on the nail bed, a layer of living tissue that contains nerves and blood vessels. Blood vessels in the nail bed give the nail plate its color—

normally pink (but bluish-purple if the oxygen level in the blood is low). The nail bed is also known as the quick. The cuticle is an edge of dead cells, arising from the epidermis along the proximal end of the nail. The cuticle is adherent to the nail plate to prevent microorganisms from entering the nail root. The lunula, the whitish half-moon, is the visible, white part of the nail root. The nail root, which is located beneath the skin of the finger, produces keratin-containing cells that form the nail plate. These cells are white at first (in the lunula), but gradually become opaque as the nail plate grows. Trauma to or infection of the nail root causes a misshapen nail plate. Subcutaneous Tissue The subcutaneous tissue is a loose, connective tissue. It is not considered to be part of the integumentary system, but because it is directly beneath the dermis of the skin, it is discussed here. It is composed of adipose tissue or fat that contains lipocytes. These cells store fat as an energy reserve. The amount of fat in adipose tissue usually far exceeds any energy needs the body might have! The subcutaneous tissue also provides a layer of insulation to conserve internal body heat. Depending on a person’s metabolism, dietary intake of sugars and fats, and the amount of fat stored in the lipocytes, the subcutaneous tissue can be thin or as thick as several inches. The subcutaneous layer also acts as a cushion to protect the bones and internal organs.

Physiology of an Allergic Reaction An allergy or allergic reaction is an individually unique hypersensitivity response to certain types of antigens known as allergens. Allergens include cells from plant and animal sources (foods, pollens, molds, animal dander), as well as dust, chemicals, and drugs. The basis of all allergic reactions is the release of histamine from basophils in the blood and from mast cells in the connective tissue. Allergic reactions anywhere in the body almost always involve the skin or mucous membranes. A local reaction occurs when an allergen touches the skin or mucous membranes of a hypersensitive individual. Histamine released in that area causes inflammation and redness (erythema), swelling (edema), irritation, and itching (pruritus). Examples: Chemicals in deodorant applied to the skin or pollen in the air that touches the mucous membranes in the nose. A systemic reaction occurs when allergens are inhaled by, ingested by, or injected into a hypersensitive person, causing symptoms in several body systems. Histamine constricts the bronchioles, dilates the blood vessels throughout the body, and causes hives on the skin. Examples: Inhaled pollens, molds, or dust trigger asthma attacks; ingested foods or drugs cause hives on the skin. Anaphylaxis is a severe systemic allergic reaction that can be life threatening. Symptoms include respiratory distress, hypotension, and shock. Examples: Eating peanuts, being stung by a bee, taking a drug that has caused a past allergic reaction, or being exposed to latex gloves are all common causes of anaphylaxis in hypersensitive individuals. This is also known as anaphylactic shock.

Diseases Word or Phrase

Description

Dermatitis

Edema

Hemorrhage

Lesion

Neoplasm

Pruritis

Rash

Wound

Any condition caused by disease or injury that results in inflammation or infection of the skin. Treatment: Correct the underlying cause Excessive amounts of fluid move from the blood into the dermis or subcutaneous tissue and cause swelling. Localized areas of edema occur with inflammation, allergic reactions, and infections. Large areas of edema occur with cardiovascular or urinary system diseases. Treatment: Correct the underlying cause. Trauma to the skin releases a small or large amount of blood. Extravasation is when the blood flows into the surrounding tissues. Petechiae are pinpoint hemorrhages in the skin from ruptured capillaries. A contusion is any size of hemorrhage under the skin that was caused by trauma. An ecchymosis is a hemorrhage under the skin that is 3 cm in diameter or larger. A contusion and an ecchymosis are both commonly known as a bruise. A hematoma is an elevated, localized collection of blood under the skin. Treatment: None. Any visible damage to or variation from normal of the skin, whether it is from disease or injury. Treatment: Correct the underlying cause. Any benign or malignant new growth that occurs on or in the skin. Treatment: Excision of a benign neoplasm; excision and chemotherapy drugs or radiation therapy for a malignant neoplasm. Itching. Pruritus is associated with many skin diseases. It is also part of an allergic reaction because of the release of histamine. A patient with pruritus is said to be pruritic. Treatment: Topical or oral antihistamine drug or corticosteroid drug. Any type of skin lesion that is pink to red, flat or raised, pruritic or nonpruritic. Certain systemic diseases (chickenpox, measles) have characteristic rashes. Treatment: Topical or oral antihistamine drug or corticosteroid drug. Any area of visible damage to the skin that is caused by physical means (such as rubbing, trauma, etc.). Treatment: Apply a protective covering and topical antibiotic drug to prevent infection

Xeroderma

Excessive dryness of the skin. It can be caused by aging, cold weather with low humidity, vitamin A deficiency, or dehydration. The level of hydration can be assessed by testing the skin turgor. A fold of skin pinched between the thumb and fingertips should flatten out immediately when released. Dehydration causes the skin to remain elevated (tenting of the skin) or to flatten out very slowly. Treatment: Correct the underlying cause

Changes in Skin Color Word or Phrase Albinism

Cyanosis

Erythema

Jaundice

Necrosis

Description A lack of pigment in the skin, hair, and iris of the eye. This is a genetic mutation in which there is a normal number of melanocytes, but they do not produce melanin. Treatment: None. Bluish-purple discoloration of the skin and nails due to a decreased level of oxygen in the blood. It is caused by cardiac or respiratory disease. The patient is said to be cyanotic. In healthy persons, areas of skin exposed to the cold temporarily exhibit cyanosis. Treatment: Correct the underlying cause. Reddish discoloration of the skin. It can be confined to one area of local inflammation or infection, or it can affect large areas of the skin surface, as in sunburn. The area is said to be erythematous. Treatment: Correct the underlying cause. Yellowish discoloration of the skin, mucous membranes, and whites of the eyes. It is associated with liver disease. The liver cannot process bilirubin, and high levels of unconjugated bilirubin in the blood move into the tissues and color the skin yellow. It is also known as icterus. The patient is said to be jaundiced or icteric. A patient without jaundice is said to be anicteric. Treatment: Correct the underlying cause. Gray-to-black discoloration of the skin in areas where the tissue has died. Necrotic tissue can occur in a burn, decubitus ulcer, wound, or any tissue with a poor blood supply. Necrosis with subsequent bacterial invasion and decay is gangrene, and the area is said to be gangrenous.

Pallor

Vitilgo

Treatment: Correct the underlying cause. Unnatural paleness due to a lack of blood supply to the tissue. This is caused by blockage of an artery, hypotension, or severe exposure to the cold. Treatment: Correct the underlying cause. An autoimmune disorder in which the melanocytes are slowly destroyed in irregular and ever-enlarging areas. There are white patches of depigmentation interspersed with areas of normally pigmented skin. Treatment: None

Skin Injuries Word or Phrase Abrasion

Blister

Burns

FIrst-Degree Burn Second-Degree Burn

Description Sliding or scraping injury that mechanically removes the epidermis. It is also known as a brush burn. Treatment: Apply a protective covering. Repetitive rubbing injury that mechanically separates the epidermis from the dermis and releases tissue fluid. A blister is a fluid-filled sac with a thin, transparent covering of epidermis. Blisters often form on the heel from walking in poorly fitting shoes or on the hand from rubbing with constant use of a tool. Treatment: Apply a protective covering before the activity Heat (fire, hot objects, steam, boiling water), electrical current (lightning, electrical outlets or cords), chemicals, and radiation or x-rays (sunshine or prescribed radiation therapy) can cause a burn to the epidermis or dermis. Treatment: Topical anti-infective drug to prevent infection. Second-degree burns over a large area and all third-degree burns require debridement and skin grafting. This burn involves only the epidermis and causes erythema, pain, and swelling, but not blisters. This burn involves the epidermis and the upper part of the dermis. It causes erythema, pain, and swelling. There are small blisters or larger bullae that form as the epidermis detaches from the dermis and the space between fills with tissue fluid. This is also known as a partial-thickness burn.

Third-Degree Burn

Callus

Cicatrix

Decubitus Ulcer

Excoriation

Laceration

Skin Infections

This burn involves the epidermis and entire dermis, and sometimes the subcutaneous tissue and muscle layer beneath may be involved. The area is black where the skin is charred. If nerves in the dermis are destroyed, there is local anesthesia (no sensation of pain). This is also known as a full-thickness burn. An eschar is a thick, crusty scar of necrotic tissue that forms on a third-degree burn. Eschar is removed because it traps fluid, delays healing, and can become infected. A fourth-degree burn affects muscles and bones. Repetitive rubbing injury that causes the epidermis to gradually thicken into a wide, elevated pad. A corn is a callus with a hard central area with a pointed tip that causes pain and inflammation. Treatment: Removal Fibrous tissue composed of collagen that forms as an injury heals. It is also known as a scar. A keloid is a very firm, abnormally large scar that is bigger than the original injury. It is caused by an overproduction of collagen. Unlike a scar, a keloid does not fade or decrease in size over time. Treatment: Surgical removal of a keloid, although they often grow back. Constant pressure to a particular area of the skin restricts the blood flow to those tissues. The epidermis and then dermis break down and slough off, resulting in a shallow or deep ulcer. Decubitus ulcers most often occur at pressure points overlying bony prominences such as the hip or sacrum. They are also known as pressure sores or bed sores. Treatment: Frequent repositioning, increased protein intake to rebuild tissue, and debridement of any necrotic tissue to promote healing Superficial injury with a sharp object such as a fingernail, animal claw, or thorn that creates a linear scratch in the skin. Treatment: Topical antibiotic drug to prevent infection Deep, penetrating wound. It can have clean-cut or torn, ragged skin edges. Treatment: Layered closure with sutures.

Word or Phrase Abscess

Cellulitis

Herpes

Description Localized, pus-containing pocket under the skin caused by a bacterial infection. The infection is usually caused by Staphylococcus aureus, a common bacterium on the skin. A furuncle is a localized, elevated abscess around a hair follicle and the skin is inflamed and painful. It is also known as a boil . A carbuncle is composed of large furuncles with connecting channels through the subcutaneous tissue or to the skin surface. Treatment: Incision and drainage, oral antibiotic drug. Spreading inflammation and infection of the connective tissues of the skin and muscle. It develops from a superficial cut, scratch, insect bite, blister, or splinter that becomes infected. The infecting bacteria produce enzymes that allow the infection to spread between the tissue layers. There is erythema (often as a red streak), warmth, and pain. Treatment: Oral antibiotic drug Skin infection caused by the herpes virus. There are clustered vesicles, erythema, edema, and pain. The vesicles rupture, releasing clear fluid that forms crusts. Treatment: Topical or oral antiviral drug. Herpes simplex virus (HSV) type 1 occurs on the lips. These lesions tend to recur during illness and stress. They are also known as cold sores or fever blisters. Herpes simplex virus (HSV) type 2 is a sexually transmitted disease that causes vesicles in the genital area. These lesions tend to recur during illness and stress. This is also known as genital herpes. Herpes whitlow is a herpes simplex infection at the base of the fingernail from contact with herpes simplex type 1 of the mouth or type 2 of the genitals. The virus enters through a small tear in the cuticle. Herpes varicella-zoster causes the skin rash of chickenpox during childhood. The virus then remains dormant in the nerve roots until it is activated in later life by illness or stress. Then it forms painful vesicles and crusts along a dermatome. This is also known as shingles .

Tinea

Verruca

Skin infection caused by a fungus that feeds on epidermal cells. It multiplies quickly in the warm, moist environment of body creases and areas enclosed by clothing or shoes. There is severe itching and burning with red, scaly lesions. Because some lesions are round, it was originally thought to be caused by a worm, and was (and still is) called ringworm. Tinea is named according to where it occurs on the body. Tinea capitis occurs on the scalp and causes hair loss. Tinea corporis occurs on the trunk and extremities. Tinea cruris occurs in the groin and genital areas and is known as jock itch. Tinea pedis occurs on the feet and is known as athlete’s foot. Treatment: Topical antifungal drug. Irregular, rough skin lesion caused by the human papillomavirus. It is usually on the hand, fingers, or the sole of the foot (plantar wart). It is also known as a wart. Treatment: Topical keratolytic drug to break down the keratin in the wart. Cryosurgery or electrosurgery, if needed

Skin Infestations Word or Phrase Pediculosis

Scabies

Description Infestation of lice and their eggs (nits) in the scalp, hair, eyelashes, or genital hair. Lice are easily transmitted from one person to another by combs or hats. Treatment: Shampoo and skin lotion to kill lice. Infestation of parasitic mites that tunnel under the skin and produce vesicles that are itchy. Treatment: Shampoo and skin lotion to ki...