Dermatology Chapter 7

7-1 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.

Figure 7-1 Integumentary system.

Anatomy and Physiology 7-1 Anatomy and Physiology The integumentary system consists of the skin, sebaceous and sweat 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 7-1 Anatomy of the Integumentary System Skin Consists of two layers: epidermis and dermis The epidermis is categorized as epithelial tissue and covers the external surface of the body; 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 7-1 Anatomy of the Integumentary System Epidermis Thin, outermost layer of the skin 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. The deepest part (basal layer) is composed of living cells that are constantly dividing and being forced to the surface (exfoliation). Does not contain any blood vessels; receives nutrients and oxygen from the blood vessels in the dermis Contains melanocytes, pigment cells that produce melanin, a dark brown or black pigment that absorbs ultraviolet light from the sun.

Figure 7-2 Epidermis and dermis.

Anatomy of the Integumentary System 7-1 Anatomy of the Integumentary System Dermis A thicker layer beneath the epidermis Contains collagen fibers (firm, white protein) and elastin fibers (elastic, yellow protein) Contains arteries, veins, and nerves, as well as hair follicles, sebaceous glands, and sweat glands

Anatomy of the Integumentary System Sebaceous 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

Anatomy of the Integumentary System Sweat glands Also exocrine glands Sweat contains water, sodium, and small amounts of body waste (urea, ammonia, creatinine). Help to regulate the body temperature The process of sweating and the sweat itself are both known as perspiration. Also known as the sudoriferous glands

Anatomy of the Integumentary System Hair Covers most of the body; additional facial, axillary, and pubic hairs appear during puberty. 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 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).

Anatomy of the Integumentary System Nails Cover and protect the distal ends of the fingers and toes Each consists of a nail plate, nail bed, cuticle, lunula, and nail root.

Anatomy of the Integumentary System 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 Can be thin or as thick as several inches. Acts as a cushion to protect the bones and internal organs.

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. The basis of all allergic reactions is the release of histamine from basophils in the blood and mast cells in the connective tissue.

Physiology of an Allergic Reaction Histamine causes inflammation, redness (erythema), swelling (edema), irritation, and itching (pruritus). A systemic reaction occurs when allergens are inhaled or 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.

Physiology of an Allergic Reaction Anaphylaxis is a severe systemic allergic reaction that can be life threatening; it is also known as anaphylactic shock.

Diseases Pruritus- AKA itching Rash Wound Xeroderma xer/o- = dry -derma = skin General Dermatitis- inflammation of the skin Edema- swelling Lesion- any visible damage to or variation from normal of the skin

Figure 7-5 Edema.

Figure 7-6 Types of skin lesions.

Diseases Changes in Skin Color Albinism- lack of pigment Cyanosis- condition of being blue Jaundice- Necrosis-condition of dead tissue Vitiligo- autoimmune disorder where melanocytes are slowly destroyed in an irregular pattern

Figure 7-7 Necrosis and pallor.

Figure 7-8 Vitiligo.

Vitiligo (vil/i/tye/go) on the hand – it is epidermal – the melanoctyes are completely lost in depigmented areas through an autoimmune process (body attacks these cells all by itself) – gives the hand this dotted or milk-white patches. – Form of leukoderma. Autoimmune disorders such as thyroiditis, hyperthyroidism and diabetes mellitus.

Diseases Skin Injuries First-degree burn-only involves the epidermis- pain, redness- no blisters Second-degree burn- epidermis and upper part of the dermis- pain, redness, swelling- small blisters Third-degree burn- epidermis, dermis, and subcutaneous tissue- area is black from skin being charred.

Figure 7-9 Second-degree burn of the leg.

Third degree burns – if you can’t feel it… shows variable color – Requires some extensive skin graphts to help cover that – Third degree burns are a big deal…

Diseases Skin Injuries Decubitus ulcer- AKA bed sores. Constant pressure to an area of tissue causes restricted blood flow. Keloid- firm, abnormally large scar. Caused by an overproduction of collagen. Laceration- deep, penetrating wound.

Figure 7-10 Keloid.

Key/loid – scars that have overgrown – hypertrophied, thickened scar developing after trauma or surgical incision – term comes from kelis, meaning blemish

Figure 7-11 Decubitus ulcer.

Figure 7-12 Laceration.

Diseases Skin Infections Abscess- pus containing pocket under the skin Cellulitis- inflammation of the cells Herpes varicella-zoster Shingles- known as chickpox in children. In adults it forms painful vesicles.

Figure 7-13 Shingles.

Diseases Malignant Neoplasms of the Skin Cancer of the skin Basal cell carcinoma- most common type. Appears as a raised pearly bump Malignant melanoma- forms in the melanocytes in the epidermis A-asymmetry B-border or edge is irregular C-color varies form black to brown D- diameter is greater than ¼ inch Squamous cell carcinoma- begins in the flat squamous cells of the epidermis. Appears as a red bump or ulcer

Basal cell carcinoma – also needs to be excised – deep excision on this one… Basal cell carcinoma is a malignant tumor of the basal cell layer of the epidermis – most frequent type of skin cancer – usually occurs in chronically sun-exposed skin, especially on or near the nose.

Figure 7-20 Malignant melanoma.

Read the slide – they need to be excised – squamous cell carcinoma – malignant tumor of the squamous epithelial cells in the epidermis – it can grow in other places other than the skin – whereever there is squamous epithelium is found (mouth, larynx, bladder, esophagus, lungs)

Diseases Autoimmune Diseases with Skin Symptoms Psoriasis psor/o- = itching -iasis = state of; process of Scleroderma- Autoimmune disorder that causes skin and internal organs to harden

Figure 7-21 Psoriasis.

Diseases Diseases of the Sebaceous Glands Acne vulgaris Acne rosacea

Figure 7-22 Acne vulgaris.

Figure 7-23 Acne rosacea.

Diseases Diseases of the Sweat Glands Diseases of the Hair Diaphoresis- excessive sweating Diseases of the Hair Alopecia- baldness

Alopicia (all/o/pea/cia) - baldness