Chapter 5 The Integumentary System

Dermatology

Study and treatment of the integumentary system, which includes skin, hair, nails, and cutaneous glands.

Epidermis

The superficial region of the skin composed of epithelial tissue.

Dermis

The underlying layer of skin, primarily made of fibrous connective tissue.

Hypodermis

The connective tissue layer beneath the skin that anchors the skin to underlying structures.

Keratinocytes

Cells that produce the fibrous protein keratin and are the most numerous in the epidermis.

Melanocytes

Cells in the skin that produce the pigment melanin, which protects keratinocyte nuclei from UV damage.

Dendritic (Langerhans) cells

Macrophages in the epidermis that activate the immune system.

Stratum Basale

The deepest layer of the epidermis containing actively mitotic stem cells.

Stratum Corneum

The outermost layer of the epidermis made up of dead, keratinized cells.

Sebaceous glands

Glands that secrete an oily substance called sebum to lubricate the skin and hair.

Eccrine sweat glands

Sweat glands found all over the body that are involved in thermoregulation.

Apocrine sweat glands

Sweat glands located in specific areas; their secretion can lead to body odor upon bacterial interaction.

Alopecia

Hair thinning or loss that can occur in both sexes, often associated with aging.

First-Degree Burn

A burn that affects only the epidermis, causing redness and pain.

Second-Degree Burn

A burn that affects the epidermis and part of the dermis, causing blistering and pain.

Third-Degree Burn

A burn that destroys both the epidermis and dermis, often resulting in disfigurement.

Melanin

The pigment responsible for dark skin colors, produced by melanocytes.

Carotene

A pigment that gives a yellow to orange color, most visible in the palms and soles of the feet.

Cyanosis

A bluish skin color due to low oxygenation of hemoglobin.

Erythema

Redness of the skin due to fever, inflammation, or allergy.

Jaundice

A yellow cast to the skin caused by liver disorders.

Striae

Silvery-white scars also known as stretch marks, caused by dermal tears.

Flexure lines

Folds in the skin at or near joints that result from tight attachment of the dermis to underlying structures.

Tactile (Merkel) cells

Sensory touch receptors located in the epidermis.

Reticular layer

The deeper, denser layer of the dermis made of fibrous connective tissue.

Papillary layer

The superficial layer of the dermis composed of areolar connective tissue.

Skin

is body’s largest organ

Hypodermis (superficial fascia)

Subcutaneous layer deep to skin

Hypodermis (superficial fascia)

Not part of skin but shares some functions

Mostly adipose tissue that absorbs shock & insulates

Anchors skin to underlying structures – mostly muscles

Cells of the Epidermis

Keratinocytes, Melanocytes, Dendritic (langerhans) cells, and Tactile (merkel) cells

Keratinocytes

Produce fibrous protein keratin, Most cells of epidermis, Tightly connected by desmosomes

Melanocytes

10–25% of cells in deepest epidermis, Produce pigment melanin – packaged into melanosomes, Protect apical surface of keratinocyte nucleus from UV damage

Dendritic (langerhans) cells

Macrophages – key activators of immune system

Tactile (merkel) cells

Sensory touch receptors

Layers of the Epidermis:
Stratum Basale (Basal Layer)

Deepest epidermal layer, Also called stratum germinativum, Firmly attached to dermis, Single row of stem cells, Melanocytes compose 10 – 25% of this layer

Stratum Spinosum (Prickly Layer)

Several layers thick, Cells contain web-like system of intermediate prekeratin filaments attached to desmosomes, Abundant melanosomes and dendritic cells

Stratum Granulosum (Granular Layer)

Thin - four to six cell layers, Cell appearance changes, Cells above this layer die

Stratum Lucidum (Clear Layer)

Only in thick skin, Thin, translucent band superficial to the stratum granulosum, A few rows of flat, dead keratinocytes

Stratum Corneum (Horny Layer)

20–30 rows of dead, flat, anucleate keratinized
membranous sacs, three-quarters of epidermal thickness, Though dead, its cells have function, Protect deeper cells from environment and water loss, Protect from abrasion and penetration, Barrier against biological, chemical, and physical assaults