CHAPTER 5 The Integumentary System

The parts of the integument: Skin Sweat and Oil glands hairs Nails

The Integumentary System: The Skin The skin is pliable yet tough, allowing it to take constant punishment from external organs. Facts: Covers 2.2 meters, weighs 4 to 5 kg, and accounts for about 7% of total body weight in the average. Thickness varies from 1.5 to 4.0 mm or more in some areas. Millions of dead cells rub off daily A totally new epidermis every 25 to 45 days The average person sheds 18kg (40lbs) of skin flakes in a lifetime

The Skin

The Skin: Epidermis The epidermis is a keratinized stratified squamous epithelium consisting of four distinct cell types or five distinct layers. Cells of the epidermis: 1. Keratinocyte produce keratin 2. melanocyte produce melanin 3. Langerhans’ cell are macrophages 4. Merkel cells (epidermal dendritic cells) function as a sensory receptors for touch

Layers of the Epidermis Thick skin: covers the palms, fingertips, and soles of the feet Five Layers (strata) from deep to superficial 1. stratum basale 2. stratum spinosum 3. stratum granulosum 4. stratum lucidum 5. stratum corneum Thin skin: covers the rest of the body **stratum lucidum is absent and the other strata are thinner

The Skin:Dermis The dermis, composed mainly of dense, irregular connective tissue, is well supplied with blood vessels, lymphatic vessels, and nerves. Cutaneous receptors, glands, and hair follicles reside within the dermis

Layers of the dermis From superficial to deep: 1. papillary layer exhibits dermal papillae that protrude into the epidermis above and the epidermal ridges that produce fingerprints. 2. reticular layer is thicker and the connective tissue fibers are much more densely interwoven.

Skin Color Skin color reflects the amount of pigments (melanin and carotene) in the skin and the oxygenation level of hemoglobin in blood 1. Melanin is the only pigment made in the skin. ranges in color from yellow, redish brown, to black Stimulated by exposure to ultraviolet radiation in sunlight and protects the nuceli from damaging effects of UV radiation

Homeostatic Imbalance 1. stiae = stretch marks Tears in the dermis 2. blisters = separation of dermis and epidermis

Homeostatic imbalance Excessive sun exposure can cause clumping of elastin fibers, leading to leathery skin, temporarily depresses the immune system Alter the DNA of skin cells which may cause cancer

Homeostatic Imbalance 1. Cyanosis = poorly oxygenated blood

Homeostatic imbalance Redness, or erythema = redding of skin Pallor or blanching

Homeostatic balance Jaundice or yellow cast =

Homeostatic imbalance Bronzing =

Homeostatic imbalance Black-and-blue marks; bruises; hematomas

Appendages of the Skin Skin appendages, which derive from the epidermis, include: Hairs Hair follicles Nails Glands

Sweat (Sudoriferous) Glands Found all over the body except the nipples and the external genitalia More than 2.2 million per person

Sweat glands: Eccrine glands Merocirne glands Found over most of the body Thermoregulation Sweat is 99% water Salts, Vit C., antibodies, metabolic wastes and lactic acid

Sweat Gland: apocrine Largely confinded to the axillary and anogenital areas Larger than eccrine glands and their ducts empty along hair follicles Start production around puberty Function is unknown Cerunminous glands Mammary glands

Sebaceous (oil) glands Located all over body except palms of hands Sebum Functions to softens and lubricates the hair and skin Prevents hair from becoming brittle, and slows water loss from the skin Bacterialcidal action

Homeostatic imbalance Whiteheads Blackheads Acne Seborrhea “cradle cap”

Hairs and Hair Follicles Hair: main function is sensory protection