After completing this chapter the student will be able to:
1. Classify, compare the structure of, and give examples of each type of body membrane.
There are two major categories of body membranes:
a. Epithelial membranes, which are composed of an outer layer of epithelial tissue and an inner layer of connective tissue.
b. Connective tissue membranes, which are composed of two or more layers of connective tissues.
2. Describe the structure and function of the epidermis and dermis.
The epidermis is the outermost layer of skin. It is made up of a thin sheet of stratified squamous epithelium. The cells found in the innermost layers of the epidermis undergo mitosis; this enables the skin to repair itself. As cells produced in the deep layers of the epidermis move up toward the surface, their cytoplasm is replaced by a protein called keratin. Keratin waterproofs the skin. The tough, outer layer of the epidermis, called the stratum corneum, contains dead cells that continually flake off. Another layer of cells called the pigment layer also exists in the epidermis. This layer gives color to the skin.
The dermis is the deeper layer of skin. It is composed primarily of connective tissue. Its upper regions contain projections called dermal papillae that make fingerprints possible. The deeper areas of the dermis are filled with collagenous fibers that give toughness to skin and elastic fibers that enable the skin to stretch. The dermis also contains nerves, muscles, hair follicles, glands, and blood vessels.
3. List and briefly describe each accessory organ of the skin.
Hair is an accessory organ of the skin. It grows from a space called the hair follicle. Growth begins from a small cluster of cells at the base of the follicle. These cells are called the hair papillae. They form the hidden part of the hair, called the root, and the visible portion of the hair, called the shaft. Other accessory organs of the skin include sense receptors that carry messages of touch, temperature, pain, and pressure. Meissner’s corpuscles, which are sensitive to light touch, and Pacinian corpuscles, which are sensitive to pressure, are examples of sense receptors. Nails are also classified as accessory organs. They consist of a visible part, called the body, and a hidden part, called the root. They function to protect the skin. Skin glands are also classified as accessory organs. Examples include:
a. The sudoriferous glands that, if eccrine, produce perspiration and if apocrine, produce a thick, milky secretion.
b. The sebaceous glands produce oil to lubricate the skin.
4. List and discuss the three primary functions of the integumentary system.
The functions of the skin are:
Protection—It keeps microorganisms out of the body, protects against harmful chemicals, protects against excess fluid loss, and shields against ultraviolet radiation.
Temperature regulation—It produces sweat that cools the body.
Sense organ activity—The skin contains nerve endings, which keep us informed of changes that occur in the environment.
5. Classify burns and describe how to estimate the extent of a burn injury.
The classification system used to describe the severity of burns is based on how many tissue layers of skin are involved. A first-degree burn causes minor discomfort and reddening of the skin. It damages the epidermal layers. A second-degree burn is characterized by blisters, severe pain, swelling, fluid loss, and sometimes scarring. It involves deep epidermal layers and upper layers of the dermis. A third-degree burn causes severe scarring and is accompanied by inability to feel pain, because nerve endings have been destroyed. Both the epidermis and the dermis are completely destroyed, and tissue death can extend into subcutaneous layers.
The “rule of nines” is one of the most frequently used methods of determining the extent and depth of a burn injury. With this scale, the body is divided into 11 sections, each representing 9%, allowing 1% for the genitals.