Dr. Michael P. Gillespie


The skin (cutaneous membrane) covers the external surface of the body.

It is the largest organ of the body in terms of both surface area and weight.


Thermoregulation

Reservoir for blood

Protection from external environment

Cutaneous sensations

Excretion and absorption

Vitamin D synthesis


Two main parts

Epidermis – epithelial tissue

Dermis – connective tissue

Subcutaneous layer (hypodermis) – not part of the skin – areolar and adipose tissue

Contains nerve endings called lamellated
(Pacinian) corpuscles


Keratinized squamous epithelium

4 types of cells

5 basic layers of the epidermis


Keratinocytes (90%)

Keratino = hornlike; cytes = cells

Keratin –protects from heat, microbes, and chemicals

Melanocytes (8%)

Melano = black

Produce pigment melanin – absorbs UV light

Langerhans cells

Arise from red bone marrow – migrate to epidermis

Immune response

Merkel cells

Tactile (Merkel) disc


Stratum Basale

Stratum Spinosum

Stratum Granulosum

Stratum Lucidum

Stratum Corneum


Deepest layer

Single row of columnar or cuboidal keratinocytes

Keratin protects the deep layers from injury

Stem cells

Also known as the stratum germinativum
(germ = sprout)


Spinos = thornlike

8 – 10 layers of many sided keratinocytes close together

Provides strength and flexibility to the skin


Middle of the epidermis

Granulos – little grains

3-5 layers of flattened keratinocytes

Undergoing apoptosis (cell death)

Lamellar Granules – release a lipid-rich secretion


Lucid = clear

Present only in the thick skin of the fingertips, palms, and soles

3-5 layers of flattened clear, dead keratinocytes


Corne = horn or horny

25 – 30 layers of flattened dead keratinocytes

Shed and replaced by cells from deeper strata

Mostly keratin

Between the cells are lipids from lamellar granules
– creates water repellent barrier

Protects deep layers from injury

Friction creates a callus – abnormal thickening


Newly formed cells are pushed to the surface

Accumulate more keratin (keratinization)

Undergo apoptosis

Keratinized cells slough off

4 weeks


Common skin disorder

Keratinocytes divide more quickly than normal and shed prematurely (7-10 days)

Immature keratinocytes make abnormal keratin

Forms flaky, silvery scales

Knees, elbows, and scalp (dandruff)

Tx. Topical ointments, UV phototherapy
(decreases cell division)


Deeper layer

Mainly connective tissue

Collagen and elastic tissue

Fibroblasts, macrophages, and adipocytes


Papillary region – dermal papillae (papillae = nipples) – indent the epidermis – capillary loops

Corpuscles of touch (Meissner corpuscles)

Free nerve endings – warmth, coolness, pain, tickling, and itching


Reticular region (reticul = netlike) – deeper part of dermis

Dense irregular CT

Adipose cells, hair follicles, nerves, sebaceous (oil) glands, sudoriferous (sweat) glands

Striae – streaks – stretch marks

Epidermal ridges – grip / friction – palms, fingers, soles, toes


Thin skin – covers all surfaces of the body except for the palms, palmar surfaces of the digits, and soles.

Lacks a stratum lucidum

Thick skin – covers the palms, palmar surfaces of the fingers, and soles

Distinct stratum lucidum


Hair

Skin glands

Nails


Hair or pili – present on most surfaces except the palms, palmar surfaces of fingers, soles, and plantar surfaces of feet

Shaft – superficial portion – projects from skin

Root – deeper portion – penetrates the dermis and sometimes into the subcutaneous layer

Arrector pili – muscle which pulls on hair shaft causing it to raise – emotional stress (cold or fright)


Hirsutism = excessive body hair due to excessive androgens – tumor of the adrenal glands, testes, or ovaries

Androgenic alopecia – male-pattern baldness


Sebaceous Glands (greasy) – oil glands - typically connected to hair follicles

Secrete sebum – coats hair and keeps it from becoming dry and brittle – keeps skin soft and pliable

Sudoriferous Glands – sweat glands

Eccrine – throughout skin

Apocrine – skin of axilla, groin, areolae and bearded regions

Ceruminous Glands – cer = wax – external ear


Cerumen = earwax – creates sticky body to impede entrance of foreign substances
Impacted cerumen – irrigation w/ enzymes or blunt inst.


Tightly packed, hard, keratinized epidermal cells

Nail body, free edge and nail root

Lunula

Hyponychium – beneath free edge

Eponychium (cuticle) adheres to the lateral margin of the nail wall.


Cells enlarge and migrate across the wound

Contact inhibition – when migrating cells touch one another they stop due a this cellular response


The injury extends to the dermis and subcutaneous layer

Inflammatory phase

Blood clot forms

Inflammation eliminates wastes and microbes

Migratory phase

Damaged blood vessels begin to regrow

Proliferative phase

Extensive growth of epithelial cells

Deposition of fibroblasts

Maturation phase


The Integumentary System contributes to the functioning of all other body systems.

Refer to the table on page 155.


Skin Cancer

Burns

Pressure Ulcers


Almost exclusively caused by excessive exposure to the sun.

Basal cell carcinomas

Squamous cell carcinomas

Malignant Melanomas


A Asymmetry

MM lack symmetry

B Border

MM have notched, indented, scalloped, or indistinct borders

C Color

MM have uneven coloration, may contain several colors

D Diameter

MM are typically greater than 6mm (0.25 in.)

E Elevation


1. Skin type

Light skinned individuals who burn, but don’t tan

2. Skin exposure

Sunny areas, high altitude (UV light), outdoor occupation

3. Family Hx.

4. Age

5. Immunological status

Immunosuppressed individuals have a higher risk of skin cancer


Tissue damage caused by

Excessive heat

Electricity

Radioactivity

Corrosive chemicals
 Destroy some of the skin’s contributions to homeostasis


First-degree burn

Second-degree burn (partial thickness)

Third-degree burn (full thickness)


1. Large loss of water, plasma, and plasma proteins (causes shock)

2. Bacterial infection

3. Reduced circulation of blood

4. Decreased production of urine

5. Diminished immune response


Determined by the depth of the burn and the extent of the area involved.

According to the American Burn Association a major burn includes:

Third-degree burns over 10%

Second-degree burns over 25%

Third-degree burns over face, hands, feet, or perineum

When the burn area exceeds 70%, more than half of the victims die


Rule of nines – a quick method for estimating the surface area affected by burns

Lund-Browder method – a more accurate method for assessing the extent of burns


Melanin – causes skin color from pale yellow to black

Melanocytes produce melanin

Freckles and liver spots are accumulations of melanin

Carotene – yellow-orange pigment

Hemoglobin – imparts a red color

Albinism – inability to produce melanin - missing from the hair, eyes, and skin

Vitiligo – loss of melanocytes from patches of skin


Cyanotic – blue - hemoglobin is depleted of oxygen

Jaundice – yellow – buildup of the yellow pigment bilirubin in the blood – usually indicates liver disease

Erythema – red – engorgement of capillaries in the skin – skin injury, heat, infection, inflammation, allergies