Chapter 5

Integumentary System

Integumentary System•The integumentary system includes the skin and all of its appendages (hair, nails, and skin glands). It consists of two layers: epidermis and dermis.•Epidermis – outermost layer consists of stratified squamous epithelial tissue; no blood vessels.•Dermis – composed of connective tissue; contains collagen fibers, elastin fibers, and reticular fibers; blood vessels, sweat glands, sebaceous glands, nerve endings, and hair follicles.•Hypodermis – areolar and adipose tissue; binds skin to underlying tissue.

Cutaneous Membrane

Epidermis

Dermis

Hypodermis

Layers of Epidermis

View animation on “The generation of skin layers”

Stratum basale

Stratum corneum

Layers of Epidermis• Innermost layer is the stratum basale (basal layer or stratum germinativum), a layer of columnar stem cells that continually undergo mitosis to produce new skin cells.

• New skin cells push older cells upward and they stop dividing , producing keratin.

• Cells reach the outermost layer, the stratum corneum, and only keratin is left. These keratinocytes replace dead cells that flake away with daily wear.

• Stratum corneum consists of up to 30 layers of dead, flat, keratin-coated cells making the skin’s surface durable and resistant to abrasions. It also forms an effective barrier, preventing water from entering the body from the outside whereas still allowing for evaporation.

Skin ColorMelanocytes produce melanin.Melanin protects the nucleus from

ultraviolet (UV) exposure.The amount and type of melanin

determines skin color.Two types of melanin:

pheomelanin – a reddish coloreumelanin – a brown-black color

Various disorders can produce abnormal changes in skin color, such as cyanosis, jaundice, bronzing, albinism, erythema, pallor, and hematoma.

Functions of the SkinProtectionBarrierVitamin D productionSensory perceptionThermoregulation

QuestionNew skin cells produce which tough, fibrous protein?

A. CollagenB. ElastinC. MelaninD. Keratin

HairShaft

Hair follicle

Hair bulb or root

Papilla

Arrector pili

Hair•The hair shaft extends above the skin’s surface. •Each hair lies within a sheath of epidermis called a hair follicle. •Buried in the dermis is the hair bulb or root where growth occurs. •At the base of the hair is a cluster of connective tissue and blood vessels called the papilla that nourishes each hair. •Attached to each hair follicle is a small bundle of smooth muscle called the arrector pili muscle.

Nails

Nail body

Cuticle

Lunula

Nail bed Nail root

Nails• Nails consist of densely packed, heavily keratinized epithelial cells.

• Nail body – visible part of the nail; cuticle – a fold of skin surrounding nail body; lunula – a crescent-shaped white area at the base.

• Nail bed – layer of epithelium under the nail; normally appears pink because of the rich blood supply in the area.

• Nail root – proximal end of the nail.

• Various disorders can cause changes in nails, including clubbing, cyanosis, flattened or concave nail beds, dark lines beneath nail, white nails, yellowish nails, pale nail beds.

Sweat Glands

Eccrine gland

Apocrine gland

Sebaceous gland

Sweat Glands• There are two types of sweat glands: eccrine glands and apocrine glands.

• Eccrine glands contain a duct that leads from the secretory portion to the skin’s surface; produce sweat, which contains potassium, ammonia, lactic acid, uric acid, and other wastes.

• Apocrine glands contain a duct that leads to a hair follicle; these are scent glands that respond to stress and sexual stimulation. Sweat does not have a strong odor unless it accumulates on the skin.

• Sebaceous glands open into a hair follicle; secrete an oily substance called sebum, which helps keep the skin and hair from drying out and becoming brittle

QuestionWhich glands secrete sweat onto the skin’s surface?

A. Apocrine glandsB. Eccrine glandsC. Sebaceous glandsD. Ceruminous glands

First-Degree Burn

Involves only the epidermis

Causes redness, slight swelling, and pain

Often results from sunlight (sunburn)

First- and second-degree burns are partial-thickness burns.

Second-Degree BurnInvolves the epidermis and

part of the dermisResults in blisters, severe

pain, and swellingMay result in scarring May appear red, white,

or tan

Third-Degree BurnExtends into the subcutaneous layerMay not be painful initially May appear white or black and

leatheryOften requires skin graftsComplications include infection,

fluid loss, and lack of thermoregulation

Eschar secretes toxins and promotes bacterial growth; it can also restrict circulation

QuestionA 36-year-old woman comes to the emergency department after being exposed to steam from a broken water heater. She describes extreme pain. The skin on her face is red with white patches, swollen, and beginning to blister. What is the most likely diagnosis?

A. First-degree burnB. Second-degree burnC. Third-degree burnD. A severe scalding injury