Dermatology

Unit -7

DermatologyThe 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.

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

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.

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.

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

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

Figure 7-2 Epidermis and dermis

Anatomy of the Integumentary System (con't)• Dermis

A thicker layer beneath the epidermisContains 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.

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).

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.

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

Covers most of the bodyAdditional facial, axillary, and pubic hairs

appear during puberty.Forms in a hair follicle in the dermis

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).

Xie QiupingHair Length = 18’ 5.54”

Tran Van HayHair Length = 20’ 3.6”

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.

Figure 7-4 Nail

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

Anatomy of the Integumentary System (con't)• Subcutaneous Tissue (con't)

Can be thin or as thick as several inchesSubcutaneous layer also acts as a cushion to

protect the bones and internal organs

Physiology of an Allergic ReactionAn 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.

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-treateningEpi-pen

Figure 7-5 Edema

Figure 7-6 Types of skin lesions.

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

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

Figure 7-11 Decubitus ulcerCustom Medical Stock Photo, Inc.

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

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

Figure 7-14 Tinea pedisSPL/Photo Researchers, Inc.

Figure 7-16 HemangiomaCustom Medical Stock Photo, Inc.

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

Figure 7-21 Kaposi’s sarcomaZeva Oelbaum/Peter Arnold, Inc.

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

Table 7-1 Comparison of Acne Vulgaris and Acne Rosacea

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

Figure 7-27 Botox injectionSuzanne Dunn/The Image Works

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

Figure 7-31 Skin graftsCourtesy Martin R. Eichelberger, M.D., Children’s National Medical Center, Washington, DC

Figure 7-32 Subcutaneous injection