Skin and the Integumentary System

Chapter 6

Aids for understanding

Cut- skin Derm- skin Epi- upon Follic- small bag Kerat- horn Melan- black Seb- grease

Clinical

Transdermal patch contains drug Diffuses into the epidermis and enters

the blood vessels of the dermis

Skin

Organ vital in maintaining homeostasis Protective covering helps regulate body temp. retards water loss houses sensory receptors synthesizes biochemicals excretes small quantities of waste

Epidermis

Lacks blood vessels Stratum basale close

to the dermis is nourished by dermal blood vessels

Farther cells move, poorer nutrient supply, cells die

Older cells harden in a process called keratinization forming stratum corneum

In healthy skin, production=loss

Rate of cell division increases where the skin is rubbed or pressed regularly (calluses, corns)

Melanocytes produce melanin

Absorbs UV radiation, preventing mutations in DNA of the skin

Skin Color

All have same # of melanocytes

Amt. produced determines darkness

Environmental factors Sunlight Sunlamps X-rays

Physiological factors Amt. of blood Diet Biochemical imbalance

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Explain how the epidermis is formed.

Distinguish between the stratum basale and the stratum corneum.

What is the function of melanin?

What factors influence skin color?

Dermis

Boundary is uneven Dermal papillae extend between epidermal

ridges and form fingerprints Dermis binds epidermis to underlying

tissues Blood vessels supply nutrients to all skin

cells Nerve cell processes are scattered

throughout Contains hair follicles, sebaceous glands,

and sweat glands

Clinical

Interference with blood flow may kill epidermal cells

Pressure ulcer may appear

Occur in the skin overlying bony projections

Frequently changing body position or massaging the skin to stimulate blood flow can prevent ulcers

Subcutaneous Layer (hypodermis)

Consists of loose connective and adipose tissues

Insulates Contains major blood vessels

Accessory Organs of the Skin

Nails Protective coverings on the ends of the

fingers and toes Consists of a nail plate that overlies a

surface of skin called the nail bed The whitish, half-moon shaped lunula at

the base covers the most actively growing region

FYI: thumb nail grows slowest; the middle nail grows fastest!

Hair Follicles

Present on all surfaces except palms, soles, lips, nipples, and parts of the reproductive organs

Each hair develops from a follicle Contains hair root Composed of dead epidermal cells Arrector pili muscle attaches to each hair

follicle

Clinical

Just above base of follicle are stem cells that can give rise to hair and other epidermal cells

Manipulating these cells could someday treat baldness or extreme hairiness

Nerve Receptors

Pacinian corpuscle Detects vibrations and heavy touch sensations and sends

impulses to the brain Meissner’s corpuscle

Detects light touch sensations and sends impulses to the brain

Sebaceous glands

Holocrine glands that secrete an oily mixture of fatty material and cellular debris called sebum through ducts into the hair follicles

Clinical

Acne vulgaris – disorder of the sebaceous glands

Overactive and inflamed glands become plugged and surrounded by small, red elevations containing blackheads or pimples

Sweat Glands

glands consist of a tiny tube that originates as a ball-shaped coil in the deeper dermis

Eccrine glands respond to body temp. Common on forehead, neck, and back Sweat carried away in a duct that opens to the

outside (pore) Sweat is mostly water, but contains salt and

waste

Apocrine glands secrete sweat when a person is upset, frightened, or in pain

Ceruminous glands of the external ear canal secrete earwax

Mammary glands secret milk

Clinical

The avg. sq. in. of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than a thousand nerve endings.

Journey Through The Skin

Write a narrative essay of your journey through the skin.

Pretend as though I know nothing about these structures.

Be sure to “visit” Hypodermis

Adipose tissue Blood vessels

Dermis Nerves Hair Dermal papillae

Arrector pilius sebaceous gland Sweat gland Pores

Epidermis Stratum corneum Stratum basale melanocytes

Regulation of Body Temperature

Even slight shifts can disrupt metabolic rates 37°C (98.6°F) How it works:

Body temp. rises warmed blood reaches the brain signal sent to muscles in the walls of dermal

blood vessels to relax heat escapes Signal sent to sweat glands to release sweat

Clinical

Hypothermia – core body temp. falls below 95°F Gradual loss of

coordination Stiffening muscles Confusion Fatigue Slow, shallow breathing At 87.8°F, the skin turns

bluish-gray, weakness intensifies, and consciousness ebbs away

Hyperthermia – core body temp. exceeds 106°F Skin becomes hot, dry,

and flushed Person becomes

weak, dizzy, and nauseous

Headache Rapid, irregular pulse

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Why is regulation of body temp. so important?

How does the body lose excess heat?

Which actions help the body conserve heat?

Healing of Wounds

Inflammation – normal response to injury or stress; red and painfully swollen

blood vessels dilate and become more permeable forcing fluids to the leave the blood vessels and enter damaged tissue

Injuries Shallow break in skin – epithelial cells divide

more rapidly Deep – blood vessels break, escaping blood

forms clot (blood clot + dried tissue fluid = scab), fibroblasts form new fibers

Phagocytic cells remove dead cells and other debris

Scab sloughs off Scar may form

Large open wounds Healing accompanied by granulation (new

branch of a blood vessel and a cluster of collagen-secreting fibroblasts)

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Describe how inflammation helps a wound heal.

Distinguish between the activities necessary to heal a wound in the epidermis and those necessary to heal a wound in the dermis.

Explain the role of phagocytic cells in wound healing.

Define granulation.

Skin Cancer

the abnormal growth of skin cells — most often develops on skin exposed to the sun

There are three major types of skin cancer basal cell carcinoma squamous cell carcinoma melanoma

basal cell carcinoma

most common form of nonmelanoma skin cancer

rarely fatal, but can cause extensive damage to surrounding tissue and bone if they're not removed

have a high recurrence rate Most basal cell carcinomas are caused by

long-term exposure to ultraviolet (UV) radiation from sunlight

squamous cell carcinoma

second most common form of nonmelanoma skin cancer following basal cell carcinoma

rarely causes further problems when caught and treated early

Untreated, squamous cell carcinoma can grow large or spread to other parts of your body, causing serious complications.

melanoma

the most serious type of skin cancer, develops in the cells that produce melanin

can also form in your eyes and, rarely, in internal organs, such as your intestines

The exact cause of all melanomas isn't clear, but exposure to ultraviolet (UV) radiation increases your risk; your genetic makeup may also play a role

How to identify?

http://www.mayoclinic.com/health/melanoma/DS00575&slide=2