The Integumentary System

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

Cutaneous membrane is the skin 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

One of the largest organs 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 D uv 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 Mammary glands Modified sudoriferous glands Secrete cerumen (ear wax) Mammary glands Secrete milk

Skin color Genetic factors Environmental 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 Shallow cuts Blood vessels dilate and become permeable Heat, redness, swelling and pain Shallow cuts Epithelial cells migrate Contact inhibition

Deeper wounds Inflammatory phase Migratory phase Proliferative 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