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

24. melanin • produced by melanocytes • sunlight stimulates the melanocytes to produce more melanin (tanning) • basale cells phagocytize the melanin & form 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. • Overexposure to the sun can also alter the DNA of skin cells and in this way lead to skin cancer.

26. Dermis • The dermis is your "hide." It is leather • The dense fibrous connective tissue has two major regions— papillary and reticular

27. 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

29. The reticular layer is the deepest skin layer. It contains blood vessels, sweat and oil glands, and deep pressure receptors called Paciniancorpuscles & phagocytes That attack bacteria • As we age we produce less collagen and elastin and fat decreases (wrinkles)

30. 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

31. The Dermis Wrinkles Under normal circumstances, the fibers of the reticular layer of the skin stretch and recoil. Skin wrinkles are due to: Age UV light

32. The Dermis Stretch Marks Extensive stretching during pregnancy causes reticular fibers to break The skin does not recoil The skin wrinkles and creases resulting in stretch marks

33. The Dermis Lines of Cleavage Fibers have a tendency to organize themselves in a parallel fashion In certain areas of the body, there is a pattern To reduce scar formation (extensive damage to the fibers), surgeons try to cut parallel to the lines of cleavage

34. Accessory Structures Glands in the skin 1. Sebaceous glands 2. Sweat glands Apocrineglands Ceruminousglands (a type of apocrine gland) Mammary glands (a type of apocrine gland) Merocrine glands Both formed by stratum basale & push into dermis. Gland function: Lubricates the epidermis, excretes waste, assists in thermoregulation Cutaneous Glands (all are exocrine glands) Exocrine Glands - release secretions to surface via ducts

36. 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

40. 2. Sweat Glands (sudoriferous= sweat)— • more than 2.5 million per person. • There are two types merocrine/eccrineand 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.

41. Apocrine glands - confined to axillary and genital areas • their ducts empty onto 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 foreplay.

42. Accessory Structures Sweat glands Mammary glands A special type of apocrine gland Produce milk under the control of hormones from the pituitary gland Ceruminous glands A special type of apocrine gland Found only in the ear canal Produce cerumen (ear wax) Provide minimal protection associated with the ear

43. Disorders Sebaceous (Oil) Glands • Acne • Active infection of sebaceous glands • Can be mild or extremely severe • Whitehead • A sebaceous gland‘s duct becomes blocked by sebum • Blackhead • Accumulated material oxidized, dries, and darkens

44. Hairs and Hair Follicles • 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 • As the daughter cells are pushed away from the growing region they become keratinized and die. • root - part of the hair enclosed in the follicle • Shaft - projecting from the surface of scalp/skin • hair bulb matrix - the growth zoneat the inferior end of the follicle • medulla - a central core surrounded by a bulky cortexlayer • cuticle - single layer of cells overlap • most heavily keratinized region • dermal sheath - dermal connective tissue provides blood to hair bulb. • arrectorpili- smooth muscle connecting hair follicle to dermal tissue (goose bumps)

48. Accessory Structures Types of Hair Vellus Covers most of the body Intermediate Covers arms and legs Terminal Covers the head

49. Accessory Structures Functions of Hair Protection from UV light Insulation Guards entrance to nose and ears Movement of the hair sends impulses via nerves to the brain Such as when a bug is crawling on your arm Contraction of the arrector pili muscles Results in goose bumps

50. Accessory Structures Hair color Due to: Variation in melanin production by the melanocytes Melanin production decreases with age Influenced by: Genetics Hormones Environmental factors