The Skin

Functions of the Skin

1. Largest organ!

2. Waterproofing –

 prevents fluid loss

 maintains balance of fluids

3. Protects against infection

 blocks pathogens from entering the body

4. Sense of touch

5. Synthesis of vitamin D

6. Protects against extreme temperatures.

Related Structures of the Skin

Sebaceous glands

    Secrete sebum (oil)

         lubricates and  bacterial growth

    On hair follicles

Sweat glands - (perspiration)

    regulates body temperature

    Open at the pores on the skin surface

Hair - keeps body warm

    Composed of protein and keratin

         Keratin – fibrous water-repellent protein

             Soft – epidermis

             Hard – hair and nails

    Color determined by melanocytes at core of hair shaft

    Shape of the hair follicle determines straight or curly

Nails – unguis—protects finger tips

    Made of hard keratin

    Nail bed joins nail to connective tissues – nourishes nail

    Lunula (loo-nyuh-luh)– pale half-moon shaped region at the nail root

         This is where new keratin cells are formed

Layers of Skin

1. Epidermis—outermost layer

 Does not contain blood vessels or connective tissue

 Dependent on lower layers for nourishment

 Replaced every 4-6 weeks—regeneration in lower

lays of epidermis

2. Dermis—corium—middle layer

 thick layer of living tissue directly below epidermis.

 Contains connective tissue, nerve fibers, and blood and lymph vessels

 Contains hair follicles, sebaceous glands and sweat glands

 Helps with gripping and has finger prints

3. Subcutaneous—innermost layer

 Connects directly to surface muscles

 Largest layer of skin

 Composed mostly of adipose tissue (most body fat is located here).

The Epidermis

Outermost skin layer

No blood vessels or connective tissues

Depends on lower layers for nourishment

Made of many epithelial tissues

Tissues that form a protective covering for all internal and external surfaces of the body

1) Squamous (scale-like) epithelial tissues

    a) Upper layer of the epidermis

    b) Flat, scaly cells that are continuously shed

2) Basal layer – lowest layer of epidermis

    a) New cells formed here and pushed upward

3) Melanocytes – cells found in basal layer that make melanin

    a) Melanin – skin pigment

         Makes freckles and age spots

         Protects skin from harmful ultraviolet sun rays

The Dermis Layer

Contains: connective tissue, blood vessels, lymph vessels, nerve fibers, hair follicles, sebaceous (oil) glands, sweat glands

1) Collagen (means glue) – tough/flexible protein found in skin, bones, cartilage, tendons and ligaments

2) Mast cells – Respond to injury/infection by releasing…

    a) Histamine – released d/t allergies (itching, mucus)

    b) Heparin – anticoagulant (prevents blood clotting)

Subcutaneous Layer

Below the layers of the skin

Connects the skin to the surface muscles

Made of loose connective tissue and adipose tissue (fat)

Lipocytes (LIP-oh-sights) – cells that manufacture and store fat

Pathology of Integumentary System

Sebaceous Glands

1) Acne Vulgaris –acne – chronic inflammatory disease

     Pustular eruptions of the skin d/t production of sebum. Common with hormonal changes of puberty

2) Comedo – non-infected lesion formed by the buildup of sebum and keratin in a hair follicle. (associated with acne vulgaris)

     Obstructed (closed) – whitehead

     Exposed (open) – Sebum oxidizes and forms a blackhead

3) Seborrhea – over activity of the sebaceous glands

4) Seborrheic keratosis – benign skin growth that has a waxy “pasted-on” look. Color can vary. Common in elderly.

Sweat Glands

1) Anhidrosis: lacking sweat

2) Diaphoresis: profuse sweating

    Normal if heat/exercise or can be a response to emotional or physical distress

    “The patient is diaphoretic”

3) Hyperhidrosis: excessive sweating in one area or over the

Hair

1. Folliculitis – inflammation of the hair follicles

2. Trichomycosis axillaris – superficial bacterial infection of the hair shafts.

    Often in areas with many sweat glands

Hirsutism (HER-soot-ism) – excessive body and facial hair in women.

    Hereditary or hormonal imbalance

Alopecia – AKA baldness – partial or complete loss of hair

    Alopecia areata (ah-ree-AY-tuh) – autoimmune disorder that attacks the hair follicles causing baldness in patches

Nails

1) Clubbing: Abnormal curving of the nails and enlargement of the fingertips

    Can be hereditary

     ***Usually associated with decreased O2 amounts***

2) Koilonychia “spoon nail”

3) Onychia (oh-NICK-ee-ah): Onchitis

    Inflammation of nail matrix

    Often leads to loss of nail

4) Onychocryptosis: ingrown toenail

    Edges of a toenail grow inward and cut the skin

    Can get inflamed or infected

5) Onychomycosis: fungal infection of the nail

6) Paronychia : infection of the skin fold around a nail

    Acute or chronic

Skin Pigmentation

1) Albinism: genetic deficiency/absence of pigment in the skin, hair, irises

 Color of eyes varies with type of albinism present. Many have blue eyes, but some have reddish or purple eyes

2) Chloasma: AKA “Mask of Pregnancy” – brownish spots of the face appearing during pregnancy

     Especially in women with dark hair but fair skin

     Disappears after pregnancy

3) Vitiligo – irregular patches of white skin (depigmentation)

     Melanocytes destroyed

     Cause unknown

Intradermal Bleeding

1. Petechiae: (pee-TEE-kee-ee or pee-TEE-uh/a)

     Pinpoint hemorrhages <2 mm in diameter

     Sometimes result of high fever

2. Purpura (pur-pyoor-uh):

     2 to 10 mm in diameter

3. Ecchymosis: (ech-ih-MOH-sis):

     bruise, Area of purplish discoloration and pain d/t blood within the skin

Hematoma

Is a swelling of clotted blood trapped in the tissues.

Is usually caused by an injury.

Is reabsorbed by the body.

Is often named for the area where it occurs.

Surface Lesions

1. Crust: scab

    Collection of dried serum and cellular debris

2. Macule: Discolored flat spot that is <1cm

    Examples: freckles, flat moles

3. Papule: small raised red lesion <.5cm

    Does not contain pus

    Examples: small pimples, insect bites

4. Verrucae: (veh-ROO-kee) warts

    Small hard skin lesions caused by the human papillomavirus

5. Wheal: welt

    Small bump that itches.

    Generally from an allergic reaction

    Urticaria (ur-ti-kair-ee-uh) = hives

Fluid-Filled Lesions

1. Abscess: closed pocket of puss (bacterial)

2. Purulent (PYOUR –oo-lent): producing puss

3. Exudate (ECKS-you-dayt): fluid, such as puss, that leaks out of an infected wound

4. Cyst: Abnormal sac containing gas, fluid, or a semisolid material

    Most common is a sebaceous cyst

5. Pustule: Pimple

    Small circumscribed lesion containing pus

    *remember a papule does not contain pus

6. Bulla: Large blister

Lesions Through the Skin

1. Laceration: Torn or jagged wound or an accidental cut wound

2. Abrasion: Superficial layers of the skin are scraped or rubbed away

3. Pressure sore: Bedsore or decubitus ulcer

Birthmarks

Capillary hemangioma: strawberry birthmark

    Pink or red vascular (made of small blood vessels) birthmark

Port-wine stain: flat vascular birthmark made of dilated blood capillaries

    Large reddish/purple mark on face or neck

Dermatitis

Eczema (ECK-zeh-mah): atopic dermatitis

    Chronic, persistent condition, seen often in infants/children

    Malfunction of immune system

Exfoliative dermatitis: Widespread scaling of the skin

    Accompanied by pruritus (proo-rahy-tuhs)(itching)

    redness and hair loss

Erythema

Erythroderma: abnormal redness of the entire skin surface

Exanthem (eck-ZAN-thum): widespread rash, usually in children

Skin Conditions

1. Ichthyosis (ick-thee-OH-sis): Group of hereditary disorders

     Dry, thick and scaly skin

     Either increase in production of skin cells, or a decrease in shedding of skin cells

2. Lipedema: painful fat syndrome

     Chronic – fat accumulates in the tissue just under the hips and legs

     Does not go away even with weight loss

3. Systemic Lupus Erythematosus (er-ih-thee-mah-TOH-sus) AKA lupus

    Autoimmune disorder

    Red scaly rash on face and upper trunk

    Attacks other connective tissues like the joints

4. Psoriasis: red papules covered with silvery scales

    Flares

    Elbows, knees, scalp, back or buttocks

5. Rosacea: adult acne

    Red pimples and broken blood vessels

     Chronic, unknown cause

6. Scleroderma: autoimmune disorder

    Connective tissues (skin, joints and internal organs) become red, thick and hard and swollen

7. Urticaria: hives

    Itchy wheals d/t allergic reaction

8. Xeroderma: Excessively dry skin

Bacterial Infections

Cellulitis: acute rapidly spreading bacterial infection in the connective tissues (extremely serious)

     Malaise, swelling, warmth, and red streaks

Furuncles (FYOU-rung-kulz): boils

     Large tender swollen areas around hair follicles or sebaceous glands

     Staphylococcal infection

Carbuncle: cluster of connected furuncles (cluster of connected boils)

Impetigo (Im-peh-TYE-goh)

    Highly contagious

    Isolated pustules that crust and rupture

Necrotizing fasciitis: caused by group A strep which is flesh-eating bacteria

    Group A strep often live harmlessly on the skin

    If enter a wound, the infection destroys tissue and can be fatal

Fungal Skin Infections

Tinea (TIN-ee-ah): ringworm

    No worms involved, lesion circular with normal middle

    Can grow on anywhere on the body. Different names depending on location

Tinea capitis : scalp

Tinea corporis: body

Tinea cruris: jock itch

Tinea pedis: athlete’s foot

Parasitic Skin Infections

Pediculosis (pi-ˌdi-kyə-ˈlō-səs): lice

    Nits (lice eggs) must be destroyed as well as the lice themselves

Scabies:

    Infestation of itch mites

    Burrow into top layer of skin to lay eggs

    Cause small itchy bumps/blisters

Skin Growths

Granulation tissue: tissue that normally forms during wound healing.

    This tissue eventually forms the scar

Cicatrix: Normal Scar resulting from the healing of a wound.

Keloid: Abnormally raised/thick scar that expands beyond the boundaries

of the original incision

    More common in dark-pigmented skin

Granuloma: Small knot-like swelling of granulation tissue in the epidermis d/t inflammation, injury or infection

Keratosis: any skin growth that results in an overgrowth/thickening of the skin

    Actinic keratosis: precancerous skin growth on sun-damaged skin.

    Pink scaly – feels like sandpaper

Papilloma: benign superficial wart-like growth on the epithelial tissue