The Integumentary system

1. The Integumentary system • two major components • 1. cutaneous membrane • A. epidermis /superficial epithelium • B. dermis/underlying connective tissues. • C. hypodermis/Deep to the dermis • 2. accessory structures • hair, nails, exocrine glands, blood vessels, sensory receptors for touch, pressure, temperature, and pain

2. functions of the skin • Protection - organs against shocks, abrasion, and chemical attack.(stratified squamous epithelium) • Excretion- salts, water, and organic wastes by glands. • Maintenance of temperature - insulation or evaporation • Synthesis of vitamin D3 - steroid converted to hormone calcitriol, important to normal calcium metabolism and membrane repair. • Storage - nutrients.lipids • Detection - touch, pressure, pain, and temperature

7. The Epidermis There are four cell types found in the epidermis Keratinocytes Produces a tough protein called keratin Melanocytes Pigment cells located deep in the epidermis Produce melanin (skin color) Merkel cells Sensory cells Langerhans cells Fixed macrophages

8. The Epidermis Thick and thin skin Thick skin Found on palms and soles Made of five layers of cells Has stratum lucidum Thin skin Found on the rest of the body Made of four layers of cells

9. LAYERS OF THE EPIDERMIS • In order, from the basal lamina toward the free surface, are the • stratum germinativum(basale), • stratum spinosum, • stratum granulosum, • stratum lucidum, • stratum corneum.

11. Stratum granulosum Stratum spinosum

13. stratum germinativum/basale • Dermal projections called dermal papillae extend between adjacent epidermal ridges • The contours of the skin surface follow the ridge patterns - Fingerprints • Large basal cells, or germinativestem cells, dominate the stratum germinativum. • Skin surfaces that lack hair also contain Merkel cells that are sensitive to touch; when compressed, they release chemicals that stimulate sensory nerve endings. • The brown tones of skin result from the pigment cells called melanacytes, with cell processes extending into more superficial layers.

14. Stratum granulosum Stratum spinosum

15. Stratum Spinosum • Each time a stem cell divides, one of the daughter cells is pushed from the stratum germinativum into the stratum spinosum, • The stratum spinosum consists of 8 to 10 layers of cells • Langerhans cells (fixed macrophages) present, stimulate a defense against (1) microorganisms that manage to penetrate the superficial layers of the epidermis and (2) superficial skin cancers.

16. Stratum granulosum Stratum spinosum

17. Stratum Granulosum • consists of three to five layers of keratinocytes displaced from the stratum spinosum. • By the time cells reach this layer, most have stopped dividing & they begin making large amounts of keratin and keratohyalin • Keratin is a tough fibrous protein component of hair and nails. • Keratohyalin forms dense granules that dehydrate the cell and aggregate cross-linking of the keratin fibers. • The nuclei and other organelles disintegrate, and the cells die. • dehydration creates a tightly interlocked layer of cells of keratin fibers surrounded by keratohyalin.

18. Stratum granulosum Stratum spinosum

19. Stratum Lucidum • In the thick skin of the palms and soles, a glassy stratum lucidumcovers the stratum granulosum • The cells in the stratum lucidum are flattened, densely packed, and filled with keratin. • thick skin, on the palms and soles have five layers … lucidum is the 5th layer

20. Stratum granulosum Stratum spinosum

21. Stratum Corneum • At the exposed surface of both thick skin and thin skin • contains 15 to 30 layers of keratinized cells. • remain tightly interconnected by desmosomes. shed in large groups or sheets rather than individually. • 15 to 30 days for a cell to move from the stratum germinativum to the stratum corneum. • The dead cells remain in the exposed stratum corneum layer for an additional two weeks before they are shed • insensible perspiration Water from interstitial fluids slowly evaporates into the surrounding air. You lose roughly 500 ml (about 1 pt) of water in this way each day.

22. Skin Color • Three pigments contribute • (1) melanin - amount and kind (yellow, reddish brown, or black) • (2) carotene - orange-yellow found in carrots & orange, deep yellow, or leafy green vegetables. • (3) oxygen – amount bound to hemoglobin • people who produce a lot of melanin have brown-toned skin. • the crimson color of oxygen-rich hemoglobin gives the skin a rosy color • When hemoglobin is poorly oxygenated, the skin appear blue, a condition called cyanosis • Cyanosis is common during heart failure and severe breathing disorders. • skin color signals disease states: • • Rubor, Redness, or erythema - embarrassment (blushing), fever, hypertension, inflammation, or allergy. • • Pallor, or blanching - emotional stress (fear, anger, and others), Pale skin may also signify • anemia, low blood pressure, or impaired blood flow into the area. • • Jaundice, or a yellow- cast – liver disorder excess bile pigments in the blood • Bruises - sites where blood has escaped and has clotted in the tissue spaces.(hematomas) unusual bruising may signify a deficiency of vitamin C or hemophilia

23. melanin • yellow to brown to black, is produced by melanocytes • sunlight stimulates the melanocytes to produce more melanin (tanning) • basale cells phagocytize the melanin & forms a protective "umbrella" over nuclei (DNA) from ultraviolet radiation in sunlight. • Freckles and moles are where melanin is concentrated in one spot. • excessive sun eventually damages the skin. • It causes the elastic fibers to clump, leading to leathery skin. It also depresses the immune system. • herpes simplex cold sore virus - are more likely to have an eruption after sunbathing. • Overexposure to the sun can also alter the DNA of skin cells and in this way lead to skin cancer.

27. Dermis • The dermis is your "hide." It is leather • The dense fibrous connective tissue has two major regions— papillary and reticular • The papillary layer is the upper region. It is uneven and has fingerlike projections called dermal papillae that create fingerprints • They contain capillaries, pain receptors (free nerve endings) and touch receptors called Meissner's corpuscles • The reticular layer is the deepest skin layer. It contains blood vessels, sweat and oil glands, and deep pressure receptors called Pacinian corpuscles & phagocytes That attack bacteria • As we age we produce less collagen and elastin and fat decreases (wrinkles)

28. hypodermis • Foundation that attaches to bone and muscle • Supplies skin with blood vessels and nerves • Consists of loose connective tissue • Called subcutaneous tissue or superficial fascia • ½ of the body’s fat is in hypodermis • Insulates, energy, padding • Used to calculate total body fat

29. Hairs and Hair Follicles • millions of hairs all over the body • Guards the head, shields the eyes (eyelashes) • keep foreign particles out of the respiratory tract (nose hairs) • A hair is produced by a hair follicle • root - part of the hair enclosed in the follicle • Shaft - projecting from the surface of scalp or skin • hair bulb matrix - the growth zoneat the inferior end of the follicle • As the daughter cells are pushed away from the growing region they become keratinized and die. • medulla - a central core surrounded by a bulky cortex layer • cuticle - single layer of cells overlap like roof shingles • most heavily keratinized region • pigment is made by melanocytes in hair bulb • dermal sheath - dermal connective tissue provides blood to hair bulb. • arrectorpili - smooth muscle connecting hair follicle to dermal tissue (goose bumps)

32. glands of the Skin • Cutaneous Glands (all are exocrine glands) • Exocrine Glands - release secretions to surface via ducts • two groups: • 1. sebaceous glands and • 2. sweat glands. • Both formed by stratum basale & push into dermis.

33. 1. Sebaceous (Oil) Glands – • - all over except on the palms of hands and feet. • Their ducts usually empty into a hair follicle but • some open directly onto the skin surface.(lips, eyelids, genitalia) • sebum (seb = grease), mixture of oily substances and fragmented cells lubricate skin & kill bacteria, • male sex hormones produced in both sexes during adolescence increase sebum • Whitehead - a sebaceous gland's duct becomes blocked by sebum • blackhead - the accumulated material oxidizes, dries and darkens • Acne - active infection of the sebaceous glands • can be mild or extremely severe, leading to permanent scarring. • Seborrhea ("cradle cap“) in infants – • overactivity of the sebaceous glands on the scalp • starts as pink, raised lesions that gradually form a yellow to brown crust that sloughs off as oily dandruff.

34. 2. Sweat Glands (sudoriferous= sweat)— • more than 2.5 million per person. • There are two types merocrine/eccrine and apocrine. • Merocrine/eccrine glands - more numerous all over the body. produce sweat, primarily water plus salts, vitamin C, traces of metabolic wastes (ammonia, urea, uric acid), and lactic acid (attracts mosquitoes). • Sweat is acidic (pH from 4 to 6), and inhibits growth of bacteria, which are always present on the skin surface. • Apocrine glands - confined to axillary and genital areas • larger than eccrine glands, their ducts empty into hair follicles. • Their secretion contains fatty acids, proteins, salt & water • may have a milky or yellowish color. odorless, but when bacteria that live on skin use its proteins and fats it has an unpleasant odor. • Apocrine glands begin to function during puberty under the influence of androgens. • Their precise function is not yet known, but they are activated by nerve fibers during pain and stress and during sexual foreplay.

35. nails • A scalelike modification of the epidermis • free edge • body (visible attached portion) • root (embedded in the skin) • Nailfolds - overlapped skin folds • cuticle - thick proximal nail fold • nail bed - stratum basale beneath the nail • nail matrix - thickened proximal areais responsible for nail growth • produced by the matrix nails become keratinized and die (nonliving) • Nails look pink because of the rich blood supply in the underlying dermis • Lunula - white crescent over nail matrix

36. eyelopmental Aspects of Skin l/and Body Membranes • During the fifth and sixth months of fetal develop­ment, the soon-to-be-born infant is covered with a downy type of hair called lanugo (lah-noo'go), but this hairy cloak has usually been shed by birth. When a baby is born, its skin is covered with vernix caseosa (ver'niks kah-se-o'sah). This white, cheesy-looking substance, produced by the seba­ceous glands, protects the baby's skin while it is floating in its water-filled sac inside the mother. The newborn's skin is very thin, and blood vessels can easily be seen through it. Commonly, there are accumulations in the sebaceous glands, which ap­pear as small white spots called milia (mil'e-ah), on the baby's nose and forehead. These normally disappear by the third week after birth. As the baby grows, its skin becomes thicker and moist, and more subcutaneous tat is deposited. • During adolescence, the skin and hair become ,,more oily as sebaceous glands are activated, and acne may appear. Acne usually subsides in early adulthood, and the skin reaches its optimal ap­pearance when we are in our 20s and 30s. Then visible changes in the skin begin to appear as it is continually assaulted by abrasion, chemicals, wind, sun, and other irritants and as its pores become clogged with air pollutants and bacteria. As a re­sult, pimples, scales, and various kinds of der­matitis (der"mah-ti'tis), or skin inflammation, be­come more common. • During old age, the amount of subcutaneous tissue decreases, leading to the intolerance to cold so common in the elderly. The skin also becomes drier (because of decreased oil production and de­clining numbers of collagen fibers) and, as a result, it may become itchy and bothersome. Thinning of the skin, another result of the aging process, makes it more susceptible to bruising and other types of injuries. The decreasing elasticity of the skin, along with the loss of subcutaneous fat, allows bags to form under our eyes, and our jowls begin to sag. This loss of elasticity is speeded up by sunlight, so one of the best things you can do for your skin is to shield it from the sun by wearing sunscreens and protective clothing. In doing so, you will also be decreasing the chance of skin cancer. Although there is no way to avoid the aging of the skin, good nutrition, plenty of fluids, and cleanliness help delay the process. • Hair loses its luster as we age, and by age 50 the number of hair follicles has dropped by one-third and continues to decline, resulting in hair thinning and some degree of baldness, or alopecia (al"o-pe'she-ah), in most people. Many men become ob­viously bald as they age, a phenomenon called male pattern baldness. A bald man is not really hairless— he does have hairs in the bald area. But because those hair follicles have begun to degenerate, the hairs are colorless and very tiny (and may not even emerge from the follicle). Such hairs are called vellus (veil = wool) hairs. Another phenomenon of aging is graying hair. Like balding, this is usually genetically controlled by a "delayed-action" gene. Once the gene takes effect, the amount of melanin deposited in the hair decreases or becomes entirely absent, which results in gray-to-white hair. • S Certain events can cause hair to gray or fall out prematurely. For example, many people have claimed that they turned gray nearly overnight be­cause of some emotional crisis in their life. In addi­tion, we know that anxiety, protein-deficient diets, therapy with certain chemicals (chemotherapy), ra­diation, excessive vitamin A, and certain fungal dis­eases (ringworm) can cause both graying and hair loss. However, when the cause of these conditions is not genetic, hair loss is usually not permanent. •