Skin and Mucous Membranes

Structure and Function

The integumentary system includes the skin and mucous membranes, which cover surfaces and line body cavities that open to the exterior. The skin is the largest and one of the most important organs of the body. It is a sheet-like organ made up of two main layers: the epidermis and the dermis.

The outer layer is called the epidermis. The outer layer of the epidermis is constantly shed. Oil on the skin keeps it water repellant and pliable. The epidermis contains melanin, which gives skin its color, and keratin, which provides waterproofing.

The inner layer is called the dermis. This layer contains tough fibers that hold the skin together and make it more elastic. It also contains a rich blood supply, hair follicles, and sweat and oil glands. The cells of the dermis divide continuously and move toward the outer surface. Glands, nails and hair follicles are all considered appendages of the skin.

Under the dermis is the subcutaneous layer of tissue. This is a fatty, elastic layer that provides support, insulation, protection and energy storage.

The skin has several important functions: protection, temperature regulation and communication. The skin protects the body from infection by providing an acidic barrier. Intact skin will also repel many disease-causing organisms. The skin protects against injury and water loss. Skin also helps to regulate body temperature.

When the body needs to cool down, blood is sent to the skin; sweat coats the skin and removes body heat through evaporation into the air. When the body needs to conserve heat, blood is shunted away from the skin, and shivering may occur. Nerve endings in the skin provide information to the brain about what is going on outside the body. This allows us to communicate with our external environment and to self-regulate our internal environment.

Mucous membranes are similar to skin except that they line cavities that open to the exterior of the body. They include the linings of the mouth, nose, eyelids, vagina and rectum. The cells of the mucous membranes produce a continuous supply of a thick, moist substance called mucus. Mucus keeps the membrane wet and soft, and provides lubrication. The mucous membrane has three main functions: protection, secretion and absorption. Mucous membranes protect the cavities of the body the same way skin does. Mucous membranes secretes mucus when extra protection is needed or lubrication is required. Mucous membranes can also absorb chemicals directly into the bloodstream. Certain medications are applied directly to mucous membranes for this purpose.

Age-Related Changes

 As the skin ages, it becomes thinner and more fragile. The epidermis is more prone to injury and infection. Vitamin D production occurs in the skin and decreases with age. Loss of vitamin D production results in diminished calcium storage in the bones. Glandular activity in the skin decreases, resulting in less oil and sweat production, which means the skin becomes drier and less supple. With a diminished capacity to sweat, the risk of overheating increases. Blood supply to the skin decreases, which causes the skin to cool and the person to feel cold. Decreased blood supply also causes healing to occur more slowly. Hair follicles stop functioning, and hair loss accelerates. The dermis is less resilient, and wrinkles and sagging tend to occur. The subcutaneous layer also thins. The loss of this insulation results in very fragile skin. Blood vessels break more easily, so bruising is more common. Years of exposure to the sun causes wrinkles, age spots and dry skin, and can cause skin cancer. Nerve endings in the skin can become less sensitive. This means the older person may not feel injury to the skin or temperature changes well.

Drugs that Affect the Skin and Mucous Membranes

  1. Local anesthetics are agents that have a numbing effect on the skin and mucous membranes.
  2. Antihistamines may be used to control the body’s response to a substance that may be causing itching.
  3. Anti-inflammatory drugs such as corticosteroids may reduce itching caused by allergic reactions.
  4. Antibacterial agents (antibiotics or anti-infectives) prevent or treat infections.
  5. Antifungal agents treat fungal infections. These infections may be found in almost any location on the skin or mucous membranes. Fungal infections are especially troublesome in warm, moist areas. Common names for these infections include ringworm, athlete’s foot, thrush, and yeast infections of the skin or vagina. Frequently used antifungal agents include terbinafine hydrochloride (Lamisil), fluconazole (Diflucan) and nystatin (Mycostatin).
  6. Scabicides and pediculicides kill mites that cause scabies, and head and body lice. For scabies, permethin (Nix) is most often used. For hair lice, parethrins (RID) is often used to treat infestations in the elderly.

The most common side effect of any drug applied to the skin is a local allergic reaction. During a local reaction, the area may become reddened, swollen and itchy. As a result of any topical medication, weeping or drainage may occur. If you suspect a resident is allergic to any of these drugs, report it to the person providing direction and monitoring.

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