The Integumentary System

Chapter 6

• Organs are two or more tissues which together perform a specialized function.

• Epithelial membranes are thin structures that usually contain both epithelial and connective tissue.

Three types of epithelial membranes

• Serous Membranes– Line cavities and cover organs– Simple squamous epi. over loose connective

tissue– Parietal and visceral portions– Secrete a serous (watery) fluid for lubrication

• Mucous membranes – Line cavities that open to the exterior– Layer of epithelium over connective tissue;

epithelium varies with location– Tight junctions and goblet cells

• Cutaneous membrane is the skin– the major organ of the integumentary system

• Integumentary system is the skin and the organs derived from it (hair, glands, nails)

• One of the largest organs– 2 square meters; 10-11 lbs.– Largest sense organ in the body

• The study of the skin is Dermatology

Functions:1. Regulation of body temperature

– Cellular metabolism produces heat as a waste product .

– High temperature• Dilate surface blood vessels• Sweating

– Low temperature• Surface vessels constrict• shivering

2. Protection

physical abrasion

dehydration

ultraviolet radiation

3. Sensation

touch

vibration

pain

temperature

4. Excretion

5. Immunity/ Resistance

6. Blood Reservoir

8-10 % in a resting adult

7. Synthesis of vitamin Duv light

aids absorption of calcium

Anatomy

• Epidermis Skin

• Dermis

• Subcutaneous layer or hypodermis

Epidermis

• Stratum basale (stratum germinativum)– Single layer of cuboidal to columnar cells– Stem cells that produce keratinocytes– Melanocytes - # the same for all races

• Melanin produced in a melanosome

• Stratum spinosum (thorn-like, prickly)– 8-10 layers attached by desmosomes– See spines when cell is stained for

microscopy– Keratinocytes take in melanin by cytocrine

secretion

• Stratum granulosum– 3-5 layers – Keratinization begins here– Keratohyalin found in granules– Cells beginning to die

• Stratum lucidum (lucid = clear)– More apparent in thick skin– 3-5 layers of clear cells– Eleidin

• Stratum corneum (corneum means horny)– Dead, flat cells full of keratin– Keratin is waterproof– Cells are shed

• Basal cell to surface – about 2-4 weeks

Dermis• Connective tissue layer

• Collagen and elastic fibers, nerves, blood vessels, muscle fibers, adipose cells, hair follicles and glands.

• Papillary layer – 1/5 of dermis – loose areolar connective

tissue– Highly vascular– Dermal papillae - fingerprints

• Reticular (net) layer– Dense irregular connective tissue– Sebaceous (oil) glands– Hair follicles– Ducts of sudoriferous (sweat) glands– Striae or stretch marks– Meissner’s corpuscles and Pacinian

corpuscles

Hypodermis

• Attaches the reticular layer to the underlying organs

• Loose connective tissue and adipose tissue

• Major blood vessels – rete cutaneum

Accessory organs or epidermal derivatives

• Hairs– Epidermal growths that function in protection– Shaft, root, and folllicle– Sebaceous glands, arrector pili muscle, and

hair root plexus (touch)– Hair growth and replacement have a cyclical

pattern– ‘male-pattern’ baldness

Nails

• Plates of highly packed, keratinized cells

• Protection, scratching, & manipulation

• Formed by cells in nail bed called the matrix ( in area of lunula)

• 1 mm / week

• Eponychium - cuticle

Skin Glands

• Sebaceous (oil) glands– Usually connected to hair follicles– Holocrine glands– Fats, cholesterol, proteins, salts, and cell

debris– Moistens hair and waterproofs skin

• Sweat (sudoriferous) glands– Eccrine sweat glands

• Merocrine glands• Water, salt, wastes• Function is to cool the body (also nervous)

– Apocrine sweat glands• Larger, merocrine glands• Associated with hair follicles• More viscous – fatty acids and proteins• Odor occurs when broken down by bacteria

• Ceruminous glands– Modified sudoriferous glands – Secrete cerumen (ear wax)

• Mammary glands– Secrete milk

Skin color

• Genetic factors– Same number of melanocytes– Albinism

• Environmental factors– Uv light or x-rays

• Physiological factors– Amount of blood– Amount of oxygen

• Cyanosis• Carotene accumulation• Jaundice – liver disorder

Wound healing

• Inflammation– Blood vessels dilate and become permeable

• Heat, redness, swelling and pain

• Shallow cuts– Epithelial cells migrate– Contact inhibition

Deeper wounds

• Inflammatory phase– Fibrin forms clot

• Migratory phase– Fibroblasts make granulation tissue

• Proliferative phase

• Maturation phase

• Scars – hypertrophic scar – keloid

Burns

• First degree or partial thickness burn– Only epidermis is damaged– Erythema, mild edema, surface layer shed– Healing – a few days to two weeks– No scarring

• Second degree- deep partial-layer burn– Destroys epidermis– Blisters form – Healing depends on survival of accessory

organs– No scars unless infected

• Third degree or full-thickness burn– Destroys epidermis, dermis and accessory

organs of the skin– Healing occurs from margins inward– Skin grafting may be needed

• Autograft• Homograft

• Rule of Nines