INTEGUMENTARY SYSTEM

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I. Integumentary Structure and Function A.

The integument is the largest organ of the body, and together with its epidermal structures (hair, glands and nails) it is the integument system.

1. The skin is considered an organ since it consists of several kinds of tissues that function together.

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2. The skin varies in thickness, the thickest parts of the body exposed to wear and abrasion, soles of feet and palms of hands.

3. The thinnest is the eyelids, external genitalia and tympanum. 4. Skin variations help to identify some underling problem. Example – pale skin- shock, red skin- infection. 3

B. Development of the Associated Structures 1. Hair, glands and nails develop from the germinal layer of the epidermis and are ectodermal in organ.

2. Before hair can form, a hair follicle must be present.

3. Each hair follicle begins to develop about 12 weeks.

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4. Sebaceous glands and sweat glands are both two important aspects of the integumentary system. Both develop from the germinal layer of the epidermis.

5. Mammary glands are modified sweat glands, which develop like sweat glands.

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6. Nails begin developing at about ten weeks. 7. The thickened area of epidermis is called the nail field. 8. The nail itself is called the nail plate.

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C. The integumentary system has two major components: the cutaneous membrane and the accessory structures.

1. Cutaneous membrane or skin is an organ composed of epidermis and the underlying connective tissues of the dermis.

2. Large stem cells or germinative cells, culminate the stratum germinativum 10

3. The accessory structures include hair, nails and endocrine glands.

4. Beneath the dermis, is the subcutaneous layer or the hypodermis, which attaches the integument to muscles or bones.

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5. Five functions of the integument are: protection, temperature maintenance, synthesis and storage of nutrients, sensory reception and excretion/secretion.

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D. The Epidermis 1. The epidermis consists of a stratified squamous epithelium of several different cell layers.

2. In thick skin (the thickest found on palms of your hands and soles of the feet) have five layers.

3. Thin skin only has three layers.

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E. Layers of the Epidermis 1. Stratum Germinativum- The deepest epidermal layer. Also called stratum basale. The stratum germinativum forms epidermal ridges.

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Stratum granulosum consists of cells displaced. they make amounts of keratin. Keratin is water-resistant. 15

3. The most superficial layer of the epidermis is the stratum corneum, consists of 15-30 layers of flattened and dead epithelial cells that have accumulated large amounts of keratin.

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F. The color of your skin is caused by epidermal pigmentation and dermal blood supply.

1. The epidermis contains two skin pigments carotene (orange-yellow) and Melanin (brown, yellow- brown or black pigmentation) 2. Melanocytes make and store melanin.

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3. Melanocytes activity slowly increases in response to sunlight. 4. Freckles are areas of larger than average melanin production. 18

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5. Sunlight contains significant amounts of Ultraviolet radiation (UV). A small amount of UV is necessary for the production of vitamin D.

6. Vitamin D is absorbed by the liver and then converted by the kidneys into calcitriol, a hormone essential for the absorption of calcium and phosphorous. Low levels of Vitamin D can lead to abnormal bone growth 20

7. To much exposure to UV can cause serious burns or cancer 8. Despite the presence of melanin, long term damage can result form repeated exposure, even in darkly pigmented individuals. 21

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G. Dermal Circulation 1. Blood with abundant oxygen is bright red, which is apparent in lightly pigmented individuals. 2. Skin takes on a bluish color when it has low levels of oxygen or when the skin is very cold. This condition is called cyanosis. It can occur for poor circulatory disorders (blue lips, skin) and heart conditions.

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H. Skin Cancer 1. Skin cancers are the most common form of cancer.

2. Basal cell carcinoma is a malignant cancer that originates in the stratum basal layer. This is the most common skin cancer.

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3. Less common are squamous cell carcinomas. Metastasis (spreading) seldom occurs in either cancer, and most people survive these cancers.

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4. Melanomas are extremely dangerous. 5. Melanomas usually begins from a mole but may appear anywhere in the body. This type of cancer grows quickly and metastasizes through the lymphatic system. 27

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6. The outlook for long-term survival depends on when the condition was detected and treated. 29

II. The Dermis

A. Layers of the dermis 1.

The papillary layer consists of loose connective tissue that supports ad nourishes the epidermis. 2.

The deeper reticular layer consists of irregular connective tissue. 3.

The dermis contains a mixed cell population that include small of the cells of connective tissue.

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B. The subcutaneous layer 1. The subcutaneous layer (hypodermis) consists of loose connective tissue with many fat cells.

2. These adipose (fat) cells provide infants and small children with a layer of baby fat, which helps them reduce heat loss. 32

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4. Subcutaneous fat acts as in insulator and also serves as energy reserve and a shock absorber.

5. As we grow where we store fat changes. 34

6. Men tend to store it in the neck, upper arms and along the lower back and over the buttocks.

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7. Women store in their breasts, buttocks, hips and thighs. 8. Both men and women can also store adipose tissue in the abdominal region, “ pot belly.

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C. Assessory structures 1.

Accessory structures include hair follicles, sebaceous glands, sweat glands and nails.

2. Hairs project above the surface of the skin almost everywhere except over the sides and soles of the feet, palms of the hands and sides of the fingers and toes, lips and portions of the external genital organs.

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3. Hairs are nonliving structures produced in organs called hair follicles. 4. Hair follicles project deep into the dermis and often extend into the underlying subcutaneous layer. 5. Hair papilla is a peg of connective tissue containing capillaries and nerves.

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6. A hair root is the portion that anchors the hair into the skin.

7. The hair shaft is the part we see on the surface 40

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8. We have over 5 million hairs on our body and they all serve important functions.

9. The roughly 100,000 hairs on our head protect our scalp from UV light, helps cushion a light blow to the head and provides insulation benefits for the skull.

10. Nose hairs, ear hairs and eyelashes protect entry of foreign particles and insects.

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11. Arrector pili muscles extend from the papillary dermis. When stimulated it makes the hairs stand up. Could be caused by emotions or response to cold.

12. Hair color reflects differences in the type and amounts of pigment produced by melanocytes.

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13. Hair color is genetically controlled by environmental conditions or hormones may make the hair lighter. 14. On average about 50 hairs are lost a day but conditions could alter this; drug use, dietary factors, radiation, high fever, stress or hormonal factors regarding pregnancy. 45

15. In males, changes in he level of circulating sex hormones can affect the scalp, causing a shift in production from normal hair to peach fuzz- male pattern baldness 46

III. Sebaceous glands

A. The integument contains two types of exocrine glands: sebaceous and sweat glands.

1. skin.

Sebaceous glands or oil glands discharge a waxy, oil secretion into hair follicles or on to the 2. Sebum is oil squeezed into the hair shaft, which inhibits the growth of bacteria.

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3. The skin contains two different types of sweat glands: apocrine and merocrine sweat glands. 48

B. Apocrine 1.

Apocrine sweat glands secrete their secretions into the hair follicles in the armpits, around the nipples, and the groin. 2.

At puberty these glands are active.

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C. Merocrine sweat glands 1.

Merocrine sweat glands or eccrine sweat glands are far more numerous than apocrine.

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The skin contains about 2-5 million merocrine glands.

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3. Their secretion is called perspiration, cool the surface of the skin and reduce body temperature. 4. The skin also contains other modified sweat glands- mammary glands that secrete milk.

5. Ceruminous gland secretes earwax 51

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D. Nails 1.

Nails form on the dorsal surface of fingers and toes. 2.

Know the diagram of the finger fig 5.8

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IV. Local control and homeostasis

A. Injury and repair 1.

The skin can regenerate effectively even after considerable damage ahs occurred. 54

2. There are four steps in repair.

a. Bleeding occurs at the injury – tries to push out all the possible bacteria. Mast cells in the region trigger an inflammatory response.

b. A scab forms. Phagocytic cells remove the debris and damaged cells. Clotting around the edges begin.

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c. Phagocytic activity has ended, and the blood clot is disintegrating, d. Scab shed, depression is left where the injury occurred but scar tissue is forming.

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3. Burns are the most common injury that result from exposure of the skin to heat, radiation, electric shock or strong chemical agents. The degree of damage depends on how deep the burn goes.

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C. Aging and the Integumentary System 1.

Skin injuries and infections become more common.

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The sensitivity of the immune system is reduced. 3. Muscles become weaker, and bone strength decreases.

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4. Sensitivity to sun exposure increases.

5. The skin becomes dry and often scaly.

6. Hair thins and changes in color.

7. Sagging and wrinkling of the skin appears.

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8. The ability to lose heat decreases.

9. Skin repairs proceed relatively slow.

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V. Clinical considerations

A. Inflammatory Conditions 1. Immunological hypersensitivity or infectious agents cause inflammatory skin disorders. (Infection) 61

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2. Allergies is a hypersensitive reaction redness, itching and swollen symptoms.

3. Both benign and malignant neoplastic conditions are diseases of the skin- skin cancer.

4. Moles are a benign neoplastic growth.

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B. Burns 1. First degree burns- the epidermal layer of the skin are damaged- redness, pain and edema (swelling) 64

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2. Secondary degree burns- involves the epidermis and the dermis, blisters may appear and recovery is usually slow.

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3. Third degree burns destroy the entire thickness of the skin and frequently some underlying muscle. The skin appears charred and is insensitive to touch.

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C. Frostbite 1. First degree- the skin will appear cyanotic (bluish) and swollen.

2. Second degree- vesicle formation and hyperemia (swollen blood) 3. Third degree- Severed edema, some bleeding and numbness followed y intense throbbing pain and necrosis of the affected tissue. Gangrene will follow untreated third degree burns.

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D. Skin Grafts 1. If extensive area is damaged new skin cannot grow back. 2. A skin graft is a segment of skin that has excised from a donor site and is transplanted to the recipient site or graft bed. 72

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The end- Integumentary system: skin/hair/glands/nails

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