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Dermatology Unit -7

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Dermatology The medical specialty that studies the anatomy and physiology of the integumentary system and uses diagnostic tests, medical and surgical procedures, and drugs to treat integumentary diseases.

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Figure 7-1 Integumentary system

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Anatomy and Physiology The integumentary system consists of the skin (epidermis and dermis), sebaceous glands, hair, and nails. Protects the body and is the first line of defense against invading microorganisms Includes the sense of touch

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Anatomy of the Integumentary System Skin consists of two different layers: The epidermis is categorized as epithelial tissue and covers the external surface of the body. The epidermis 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.

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Anatomy of the Integumentary System (con't) Epidermis This is the thin, outermost layer of the skin. It contains 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, so they are constantly being shed or sloughed off in the process known as exfoliation.

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Anatomy of the Integumentary System (con't) Epidermis (con't) The deepest part (basal layer) of the epidermis is composed of living cells that are constantly dividing and being forced to the surface (exfoliation). Does not contain any blood vessels; it receives nutrients and oxygen from the blood vessels in the dermis

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Anatomy of the Integumentary System (con't) Epidermis (con't) Contains melanocytes, pigment cells that produce melanin, a dark brown or black pigment that absorbs ultraviolet light from the sun to protect the DNA in skin cells from undergoing genetic mutations

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Figure 7-2 Epidermis and dermis

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Anatomy of the Integumentary System (con't) Dermis A thicker layer beneath the epidermis Contains collagen fibers (firm, white protein) and elastin fibers (elastic, yellow protein) Contains arteries, veins, and neurons (nerve cells), as well as hair follicles, sebaceous glands, and sweat glands A dermatome is a specific area on the skin that sends sensory information to the spinal cord.

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Anatomy of the Integumentary System (con't) Sebaceous and Sweat Glands Sebaceous glands are a type of exocrine gland in the dermis that secrete sebum through a duct into a hair follicle. Also known as oil glands. Sweat glands are also exocrine glands. Sweat contains water, sodium, and small amounts of body waste (urea, ammonia, creatinine).

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Anatomy of the Integumentary System (con't) Sebaceous and Sweat Glands (con't) Sweat glands help to regulate the body temperature. The process of sweating and the sweat itself are both known as perspiration. The sweat glands are also known as the sudoriferous glands.

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Anatomy of the Integumentary System (con't) Hair Covers most of the body Additional facial, axillary, and pubic hairs appear during puberty. Forms in a hair follicle in the dermis

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Anatomy of the Integumentary System (con't) Hair (con't) 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).

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Anatomy of the Integumentary System (con't) Nails Cover and protect the distal ends of the fingers and toes Each nail consists of a nail plate, nail bed, cuticle, lunula, and nail root.

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Figure 7-4 Nail

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Anatomy of the Integumentary System (con't) Subcutaneous Tissue A loose, connective tissue directly beneath the dermis of the skin Composed of adipose tissue or fat that contains lipocytes (fat-storing cells) Provides a layer of insulation to conserve internal body heat

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Anatomy of the Integumentary System (con't) Subcutaneous Tissue (con't) Can be thin or as thick as several inches Subcutaneous layer also acts as a cushion to protect the bones and internal organs

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Physiology of an Allergic Reaction An allergy or allergic reaction is a 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.

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Physiology of an Allergic Reaction (con't) The basis of all allergic reactions is the release of histamine from basophils in the blood and mast cells in the connective tissue. A local reaction occurs when an allergen touches the skin or mucous membranes of a hypersensitive individual Anaphylaxis is a severe systemic allergic reaction that can be life-treatening Epi-pen

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Figure 7-5 Edema

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Figure 7-6 Types of skin lesions.

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Figure 7-7 Necrosis and pallo Meyer/Custom Medical Stock Photo, Inc.

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Figure 7-9 Second-degree burn of the hand Logical Images, Inc.

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Figure 7-11 Decubitus ulcer Custom Medical Stock Photo, Inc.

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Figure 7-12 Laceration Gill/Custom Medical Stock Photo, Inc.

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Figure 7-13 Shingles Gill/Custom Medical Stock Photo, Inc.

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Figure 7-14 Tinea pedis SPL/Photo Researchers, Inc.

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Figure 7-16 Hemangioma Custom Medical Stock Photo, Inc.

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Figure 7-20 Malignant melanoma ISM/Phototake, Inc.

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Figure 7-21 Kaposis sarcoma Zeva Oelbaum/Peter Arnold, Inc.

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Figure 7-22 Psoriasis NMSB/Custom Medical Stock Photo, Inc.

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Table 7-1 Comparison of Acne Vulgaris and Acne Rosacea

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Figure 7-26 Allergy skin testing SIU/Photo Researchers, Inc.

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Figure 7-27 Botox injection Suzanne Dunn/The Image Works

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Figure 7-30 Liposuction James King-Holmes/D. Mercer/Photo Researchers, Inc.

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Figure 7-31 Skin grafts Courtesy Martin R. Eichelberger, M.D., Childrens National Medical Center, Washington, DC

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Figure 7-32 Subcutaneous injection