The Integumentary System (Skin) Department of Biology and Anatomy and Physiology Mission Hills High School

The Skin: The skin is an organ that forms a water-proof protective barrier against germs (and other organisms) keeps the inside of your body inside your body keeps what's outside of your body outside. Skin also helps maintain a constant body temperature. Regulates electrolytes It is also important in the production of vitamin D Important sensory organ for pain, touch and temperature

The Skin: The skin is the largest organ of the body Human skin is only about 0.07 inches (2 mm) thick. On average, an adult has from 18-20 square feet (about 2 square meters) of skin, which weighs about 6 pounds (2.7 kg). Skin is made up of two layers that cover a third fatty layer…

The outer layer is called the epidermis; it is a tough protective layer that contains melanin (which protects against the rays of the sun and gives the skin its color).

The second layer (located under the epidermis) is called the dermis; it contains nerve endings, sweat glands, oil glands, and hair follicles.

Under these two skin layers is a fatty layer of subcutaneous tissue (the word subcutaneous means "under the skin"). It is also called the Hypodermis

The epidermis The top most layer (epidermis) of the skin is translucent and allows light to be transmitted through to the dermis. It is composed of five layers of cells: Cornified layer, Lucidum layer(only in skin of palms of hands and soles of feet) Granular layer, Spinous layer and the germinal or basal layer.

Cornified (horny) layer Cornified Layer: - dead cells converted to a water-repellant protein called keratin that coninously flakes off (desquamates) Cornified (horny) layer

Lucidum layer – So named because of the translucent protein eleidin from which Keratin forms. It is present only on palms of hands and soles of feet Lucidum Layer

Thin skin- Most of the epidermis on the human body has four layers due to the Lucidum layer missing:

Granular layer: - So named because of granules visible in the cytoplasm of the cells (cells die in this layer) Granular layer

Spinous layer: - Several layers of irregularly shaped cells.

Basal (or germinal) Layer – Only cell layer in the epidermis that undergoes mitosis. New cells are produced in this deepest layer at the same rate as Keratinized cells are lost in the cornified layer. Basal (or Germinal) Layer

Basal Layer and Skin Color– Melanocytes which produce the skin pigment melanin, are found in this layer. Amount of melanin produced is a hereditary factor and determines skin color. Melanocytes found In the basal layer

Melanocytes– Excessive Ultraviolet light exposure (sun) also stimulates the melanocytes to produce melanin (sun tan). So too does excessive ACTH (a hormone) and MSH (melanocyte-stimulating hormone) produced by the pituitary gland. UV and Hormone Stimulation

Skin Cancer Skin cancer is the most common form of cancer in the United States. More than 500,000 new cases are reported each year-and the incidence is rising faster than any other type of cancer. While skin cancers can be found on any part of the body, about 80 percent appear on the face, head, or neck, where they can be disfiguring as well as dangerous.

WHO GETS SKIN CANCER ...AND WHY The primary cause of skin cancer is ultraviolet radiation –most often from the sun, but… also from artificial sources like sunlamps and tanning booths… an increase in outdoor activities… perhaps the thinning of the earth's protective ozone layer are behind the alarming rise we're now seeing in skin cancers.

TYPES OF SKIN CANCER 1. Basal Cell Carcinoma By far the most common type of skin cancer is basal cell carcinoma. Fortunately, it's also the least dangerous kind--it tends to grow slowly, and rarely spreads beyond its original site. Though basal cell carcinoma is seldom life-threatening, if left untreated it can grow deep beneath the skin and into the underlying tissue and bone, causing serious damage (particularly if it's located near the eye).

2. Squamous Cell Carcinoma Squamous cell carcinoma is the next most common kind of skin cancer frequently appearing on the lips, face, or ears. It sometimes spreads to distant sites, including lymph nodes and internal organs. Squamous cell carcinoma can become life threatening if it's not treated.

3. Malignant Melanoma A third form of skin cancer, malignant melanoma, is the least common (less than 5% skin cancer cases) incidence is increasing rapidly, especially in the Sunbelt states. Malignant melanoma is also the most dangerous type of skin cancer. If discovered early enough, it can be completely cured. If it's not treated quickly, however, malignant melanoma may spread throughout the body and is often deadly.

Malignant Melanoma

Normal skin vs. Melanoma

Treatment: Skin cancer is diagnosed by removing all or part of the growth and examining its cells under a microscope. It can be treated by a number of methods, depending on the type of cancer, its stage of growth, and its location on your body.

Surgery: Most skin cancers are removed surgically, by a plastic surgeon or a dermatologist. If the cancer is small, the procedure can be done quickly and easily, in an outpatient facility or the physician's office, using local anesthesia.

Major surgery, chemotherapy and radiation If the cancer is large, however, or if it has spread to the lymph glands or elsewhere in the body, major surgery may be required. Topical chemotharapy X- ray radiation may be helpful in some cases.

Prevention: Avoid prolonged exposure to the sun, especially between 10 a.m. And 2 p.m. and during the summer months. Remember, ultraviolet rays pass right through water and clouds, and reflect off sand and snow. When you do go out for an extended period of time, wear protective clothing such as wide brimmed hats and long sleeves.

SPF On any exposed skin, use a sunscreen with an SPF (sun protection factor) of at least 15. Reapply it frequently, especially after you've been swimming or sweating.

Regular self examinations Finally, examine your skin regularly. If you find anything suspicious, consult a plastic surgeon or a dermatologist as soon as possible.