The Integtumentary

System

Functions of the Integument

• Protection• Excretion• Sensory• Water balance• Thermoregulation• Endocrine (Vitamin D)

Some facts about skin

• Largest organ of the Body• Approximately 2 square meters or 22 square feet• About 5 kg (11 pounds)• Ranges in thickness between 0.5 mm (genitals, lips,

eyelids) to 5 or 6 mm on the soles of the feet.• Three layers, from superficial to deep:

1.Epidermis - outer layer of dead, keratinized cells2.Dermis - dense irreg. c.t., nerves, vessels, etc.3.Hypodermis - mostly subcutaneous adipose tissue

Slice o’ skin

Skin: Thick

Stratum corneum

Stratum spinosum

Stratum granulosum

Stratum Basale

Dermis

Thin skin: scalp

Human scalp

Scalp: deep

Human scalp

Organization of the Epidermis

Figure 5–2

The Epidermis

MelanocytesFigure 5–5

Skin Glands

There are two general types of skin glands:1. Sudoriferous glands (sweat glands).• Eccrine glands - produce watery sweat for

cooling, waste metabolite excretion & electrolyte excretion. Found all over the body except nail beds, genitals, & ear drums. Most dense on palms, soles, forehead & chest.

• Apocrine glands - produce “stinky” sweat. Secrete a thicker, protein and lipid rich fluid and “pheromones”. Concentrated in arm pits, pubic region, areolae. Activated by the stress response or sexual arousal (sympathetic n.s.)

Skin Glands b.

• Mammary glands - Mammary glands are specialized sudoriferous glands. They produce milk. And yes, men have them too!

• Ceruminous glands - Modified sweat glands that line the external auditory canal. They make “cerumen”, also known as ear wax.

2. Sebaceous glands - produce oily secretion called “sebum”. These glands open onto the hair follicles and the oil keeps hair supple and skin water resistant..

The Dermis: Glands

Sebaceous Glands

Figure 5–10

Apocrine Sweat GlandFigure 5–11a

Merocrine Sweat Gland

Other Integumentary Glands

• Mammary glands:– produce milk

• Ceruminous glands:– protect the eardrum– produce cerumen (earwax)

Control of Glands

• Autonomic nervous system:– controls sebaceous and apocrine sweat

glands– works simultaneously over entire body

• Merocrine sweat glands:– are controlled independently– sweating occurs locally

Epidermal Appendages: Hair

Structure of a HairFigure 5–9d

Hair follicle: cross sectionFollicle wall

Connective tissueRoot sheath

Medulla

Cortex

Cuticle

Internal root sheath

Hair follicle in cross section

Structures of a

Follicle

Figure 5–9c

Epidermal Appendages:

Nails

Ridges and

Ducts

Figure 5–4

Repair of Localized Injuries to the Skin: Step 1

• Bleeding occurs

• Mast cells trigger inflammatory response

Repair of Localized Injuries to the Skin: Step 2

• A scab stabilizes and protects the area

The Inflammatory Response

• Germinative cells migrate around the wound

• Macrophages clean the area

• Fibroblasts and endothelial cells move in, producing granulation tissue

Repair of Localized Injuries to the Skin: Step 3

• Fibroblasts produce scar tissue

• Inflammation decreases, clot disintegrates

Repair of Localized Injuries to the Skin: Step 4

• Fibroblasts strengthen scar tissue

• A raised keloid forms

Stages of wound healing• Inflammatory

• Migratory

• Granulation

• Maturation– Fibrosis: scar tissue formation

• Hypertrophic scar is one that remains within the boundaries of the original wound.

• Keloid scar is one that extends to surrounding tissue beyond the original wound.

Burns

Rule of Nines

• To estimate burn damage, surface area is divided into multiples of 9

Figure 5–14

First degree (partial thickness)

Second Degree

First & second degree burns

Third degree (full thickness)

Third degree burns

Skin Cancer

• Basal cell carcinoma - 75%, arise from epidermal cells. Rarely metastasize to other tissues. Easily removed.

• Squamous cell carcinoma - around 20%, may or may not metastasize. Also from epidermal tissue.

• Malignant melanoma - remaining 5%, arise from melanocytes. Often delayed reaction to sun exposure by 10 - 20 years. Poor prognosis, they metastasize very rapidly once they begin to grow.

ABCDs of skin cancer detection

Risk factors for skin cancer

• Skin type - lighter skin pigmentation = higher risk

• Sun exposure - lower latitude, more direct sun. Longer time, greater exposure.

• Family history - Genetics nearly always plays at least some role in susceptibility to disease.

• Age - older = longer exposure.• Immune system health - people with

compromised immune systems are at greater risk.

Skin Cancer

Figure 5–6

Fungating Melanoma

Other skin pathologies• Athlete’s foot - caused by a fungus• Cold sore - herpes simplex virus type I. HSV II causes genital herpes.• Acne - inflamed sebaceous glands. Can be seriously disfiguring. Accutane™ and Retin-A™ are prescription treatments which are derived from vitamin A and have proven helpful in severe cases. OTC treatments include salicylic acid and benzoyl peroxide with variable efficacy.• Impetigo - superficial infection caused by staphylcocci or streptococci, two genera of bacteria very common to skin.• Warts - raised lesions caused by papilloma virus. HPV causes genital warts, a sexually transmitted infection, that is often associated with cervical cancer in women.

Effects of Aging

• Epidermal thinning

• Decreased numbers of Langerhans cells

• Decreased vitamin D3 production

• Decreased melanocyte activity

• Decreased glandular activity (sweat and oil glands)

Effects of Aging

• Reduced blood supply

• Decreased function of hair follicles

• Reduction of elastic fibers

• Decreased hormone levels

• Slower repair rate

Another great use for skin