The Integumentary System

1. The Integumentary System The Skin Anatomy Chapter 4

2. Functions of the Integumentary System • The word integument means covering • Keeps essential molecules inside the body such as water and nutrients • Keeps harmful substances out • Most of the functions are protective

3. Functions in protection from: • Mechanical damage • Bumps and cuts • Chemical damage • Acids and bases • Thermal damage • Heat and cold • UV radiation • sunlight • Bacteria

4. The upper most layer of the skin is composed of keratin which helps to prevent water loss. • Heat loss is regulated by sweat glands and a capillary network • The skin acts like a mini excretory system removing urea, salts, and water

5. The skin plays a role in immunity and synthesizes vitamin D • Cholesterol molecules in the skin are converted to vitamin D (calcium absorption) in presence of sunlight • The cutaneous sensory receptors are located in the skin • Touch, pressure, temperature, and pain

6. Structure of the Skin • The epidermis is the outer layer of the skin. • It is composed of stratified squamous epithelium • It contains keratin which makes the skin tough and waterproof

7. The dermis is the thick middle layer. • It is composed of dense connective tissue • The dermis and epidermis are connected • This connection can sometimes be separated allowing fluid to accumulate between the layers. • This is what causes a blister.

8. The subcutaneous layer or hypodermis is located below the dermis. • It contains adipose or fat tissue • It is not considered part of the skin but does provide several functions: • Insulation • Fat storage • Shock absorber

9. The skin is held to underlying organs by loose or areolar connective tissue.

10. Epidermis • Contains 5 layers called strata: • Corneum (top) • Lucidium (only found in thick skin) • Granulosum • Spinosum • Basale (bottom)

11. The epidermis is avascular • Most cells are keratinocytes which produce keratin which makes skin tough • The deepest layer is called the stratum basale. It is the most nourished because it is the closest to the dermis. • Cells in the basale layer are constantly dividing.

12. As cells move into the spinosum and granulosum layers, they become flatter and develop more keratin. • As the cells reach the stratum lucidium they die. The stratum lucidium is only found on the palms and soles. • The cells die in this area because of keratin, lipids, and distance from blood supply. They are not able to get the needed nutrients.

13. The stratum corneum is about 20 to 30 layers thick. It is the thickest part of the epidermis. • By the time the cells reach this point they are completely dead and filled with keratin. • Keratin is a protein that provides a tough protective covering. • The average person will shed about 40 pounds of corneum flakes in a lifetime. • You produce a totally new epidermis every 25 to 45 days.

14. Melanin is a pigment produced by cells called melanocytes. These cells are mostly found in the basale layer. • Increased exposure to sunlight causes the melanocytes to produce more melanin. • Melanin accumulates in structures called melanosomes. • Keratinocytes take up the melanosomes and forms a protective layer over any genetic material. • Freckles and moles form where melanin is concentrated in one spot.

15. The epidermis contains dendritic cells which can activate the immune system if there are bacterial or viral cells. • Merkel cells are found near the epidermis / dermis boundary. These cells serve as touch receptors.

16. Dermis • The dense connective tissue that makes up the dermis contains 2 major regions: • Papillary (upper) • Uneven surface called the dermal papillae moves into the epidermis • The dermal papillae provides nutrients to the epidermis and contains pain and touch receptors • The dermal papillae produces a pattern that increases friction on the fingers and feet. • These ridges produce fingerprints.

17. Reticular layer (lower) • The deepest skin layer. • The connective tissue contains fibers, blood vessels, sweat, and oil glands. • Contains deep pressure receptors called lamellar corpuscles. • Phagocytes found in this area help to fight off bacteria.

18. Collagen and elastic fibers are found all throughout the dermis. • Collagen fibers make the dermis tough. • Elastic fibers give the skin elasticity. • As we age, the amounts of collagen, elastic, and fat tissue in the skin decreases. This causes sagging and wrinkling.

19. The dermis contains an abundance of blood vessels. • This helps to maintain body temperature. • If body temperature rises the capillaries in the dermis fill with blood and dilate. The skin will redden. This allows heat to leave the skin. • If the body temperature lowers the blood will bypass the capillaries and the capillaries will constrict. This allows the body to conserve heat

20. Skin Color • Three pigments contribute to skin color: • Melanin: amount and kind (yellow, reddish brown, or black) • The more melanin the darker the skin • Carotene: found in the corneum and subcutaneous layers, orange-yellow pigment • Hemoglobin: pigment in red blood cells found in dermal blood vessels

21. Emotions also affect skin color and changes in skin color indicate certain diseases. • Redness or erythema • blushing, fever, hypertension, inflammation, or allergy. • Pallor or blanching: • becoming pale under stress or shock • possible sign of anemia, low blood pressure, or impaired blood flow. • Jaundice or yellow cast: • liver disorder in which excess bile is absorbed into the blood and circulated into the body.

22. Bruises or black-and-blue marks: • blood has escaped from circulation and has clotted in tissue • these clotted blood masses are called hematomas • A tendency to bruise easily may signify a vitamin C deficiency or hemophilia (bleeder’s disease) • Cyanosis • Occurs when the blood is poorly oxygenated • This causes the skin to be a blue color.

23. Appendages of the Skin Cutaneous glands Hair Hair Follicles All arise from the epidermis

24. Cutaneous Glands • Exocrine glands that secrete secretions to the surface of the skin through ducts • Fall into 2 groups • Sebaceous (oil) • Sudoriferous (sweat) • Form in the stratum basale • Push into and permanently reside in the dermis

25. Sebaceous (Oil) glands • Found all over the skin except palms and soles. • Ducts usually open into hair follicles • Produce sebum which is a mixture of oil and cell fragments. • Sebum keeps the skin soft and moist and prevents hair from becoming brittle. • Sebum also contains chemicals that kill bacteria on the skin.

26. Sweat (Sudoriferous) glands (2.5 million) • Eccrine Sweat Glands • Numerous and found all over the body • Produce sweat (water, salts, vitamin C, metabolic wastes, and lactic acid) • Sweat is acidic which inhibits the growth of some bacteria. • Nerve endings closely associated with sweat glands cause sweating when temperatures rise • Evaporation of sweat from the skin removes heat from the skin causing it to cool.

27. Apocrine Sweat Glands • Confined to the armpit and genital areas • Larger than eccrine glands • Contain all of the substances found in eccrine gland secretions plus fatty acids and proteins • Secretions have an odor when bacteria on the skin metabolize the proteins and fats. • Begin to function during puberty. • Play a minimal role in temperature regulation. • Precise function is unknown.

28. Hair and Hair Follicles • Serves a few minor protective functions: • Guarding the head • Shielding the eyes • Keeping foreign particles out of respiratory tract

29. Hair • Produced by hair follicles • Root: part of the hair enclosed by the follicle • Shaft: part projecting from the surface • Hair bulb: growth zone of hair where cell division occurs. • Division and growth occurs in the basale layer • As hair is pushed outward, the cells become keratinized and die.

30. Each hair contains a central medulla surrounded by a cortex. • The cortex is surrounded by the outer most layer called the cuticle. • The cuticle contains the most keratin and provides strength and compaction to the hair. • Split ends occur when the cuticle is worn away allowing the inner regions to frizz out.

31. Hair pigments are produced by different types and amounts of melanin produced by melanocytes in the hair bulb. • Hairs can be found on any body surface except palms, soles, nipples, and lips. • You are born with as many hair follicles as you will ever have. • Hairs are among the fastest growing tissues in the body.

32. Hair Follicles • Hair follicles have 2 sheaths 1) An inner epidermal and 2) An outer dermal which supplies blood vessels and reinforcement • Attached to each hair follicle is a band of smooth muscle called the arrectorpili. • When these muscles contract hair is pulled upright and dimpling occurs causing goose bumps when cold or frightened.

33. FYI (Not in Notes) The shape of your hair follicles determines if you will have straight or curly hair. Curly hair tends to be dryer because the oils secreted from your sebaceous glands have an easier time emptying into a straight hair follicle than a curved one.

34. FYI (Not in Notes) • As we stated earlier, skin and hair color are controlled by the pigment melanin. • The amount of melanin in our skin and hair is determined by at least 6 genes. • There are 2 additional forms of melanin that cause variations: • Pheomelanin – red to yellow • Eumelanin – dark brown to black • People that produce more pheomelanin tend to have lighter skin.

35. Nails • A nail is a modification of the epidermis • Each nail has a free edge, a body, and a root. • The borders are overlapped by nail folds • The edge of the nail fold is called the cuticle • The stratum basale makes up the nail bed • As nail cells are produced they become keratinized and die. • Nails look pink because of the rich blood supply. • The exception to this is the white base called the lunule

36. Sensory Receptors in the Skin • Free nerve endings • Pain and temperature receptors • Meissner’s corpuscles • Touch receptors • Lamellar corpuscles • Deep pressure receptors

37. Homeostatic Imbalances of the Skin • Burns • Tissue damage and cell death caused by intense heat, electricity, sunburn, or chemicals. • As a result of burns the body loses valuable fluids that contain proteins and electrolytes. • Dehydration and electrolyte imbalance can follow which can lead to shutdown of the kidneys and circulatory system.

38. The amount of fluids lost can be estimated by determining how much of the body surface is burned. • To do this you use the Rule of Nines. • This method divides the body into 11 areas each accounting for 9% of the total body surface plus an additional 1% that accounts for the genital area.

39. Head and Neck – 9% • Anterior of Arms – 9% • Posterior of Arms – 9% • Upper Anterior Trunk – 9% • Lower Anterior Trunk – 9% • Upper Posterior Trunk – 9% • Lower Posterior Trunk – 9% • Anterior Lower Legs – 9% • Anterior Upper Legs – 9% • Posterior Lower Legs – 9% • Posterior Upper Legs – 9% • Genital Area – 1%

41. After the loss of fluids, the next danger is infection. • Burned skin is sterile for about 24 hrs. • After this time pathogens can invade the burn areas. • The pathogens thrive because • 1) they are able to feed on the dead tissue • 2) after two days the immune system is depressed

42. Classification of Burns • Burns are classified according to severity or depth • First Degree • only the epidermis is damaged • area is red and swollen • usually not serious • temporary discomfort • heal in 2 to 3 days • sun burn is an example

43. Second Degree • The epidermis and upper dermis are damaged • Skin is red and painful • Blisters can form • Regeneration can occur • Normally no scars form • First and second degree burns are called partial thickness burns

44. Third degree • destroy entire thickness of skin • area appears blanched (gray or white) or blackened • because nerve endings are destroyed, the burned area is not painful • regeneration is NOT possible • skin grafting must be done to cover the underlying tissue • full thickness burns

45. Burns are considered critical if… • Over 25% of the body has second degree burns • Over 10% has third degree burns • There are third degree burns on the face, hand, or feet

46. Infections and Allergies • Athletes foot: • fungal infection • Boils & carbuncles: • inflammation of hair follicles and sebaceous glands • Cold sores: • fever blisters found around the mouth caused by viral infection

47. Contact dermatitis: • itching redness & swelling of skin caused by chemicals that cause allergic reactions • Impetigo: • pink water-filled regions with a yellow crust caused by a staphylococcus infection • Psoriasis: • overproduction of skin cells causes red lesions that can itch, burn, crack, and bleed • caused by an autoimmune disorder

48. Skin Cancer • Numerous neoplasms (tumors) arise on the skin. • Most are benign and do not spread (metastasize). • Skin cancer is the single most common type of cancer in humans (1 in 5) • Most important risk factor is exposure to UV radiation.

49. Basal Cell Carcinoma • Least malignant most common • Occurs in stratum basale • Cells proliferate into the dermis and hypodermis • Lesions occur in sun exposed areas as shiny dome shapes with a pearly edge. • Slow growing • Full cure in 99% of cases

50. Squamous cell carcinoma • Occurs in stratum spinosum • Scaly red papule that gradually forms an ulcer • Most common locations are the scalp, ears, back of the hand, and lower lip • Grows rapidly and can metastasize • Sun induced • If caught early the chance of complete cure is good