The Integumentary System Chapter 6 Organs are two

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 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 – 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