Upon completing this section, you will be able to: 1. Define the word histology. 2. Name and briefly describe the four basic types of tissue. 3. Name the three subtypes of simple epithelial tissue. 4. List the five main subtypes of connective tissue. 5. Name the three subtypes of muscle tissue. 6. Name the two types of nerve tissue.
Section 6 Types of Tissue
Histology is the microscopic study of cells, tissues, and organs. Also called microscope anatomy, histology has two basic classes: 1) normal histology— the study of normal tissues, and 2) pathologic histology—the study of diseased tissue. Malignancies are diagnosed according to the pattern of cellular growth and deviations of individual cells from their normal forms. Nurses involved with the treatment of malignancies must possess a knowledge of histology in order to understand the anatomy and classification of tumors. In this section, we will review the four basic types of tissue, their functions and locations, and the terms used to describe these tissues—terms such as squamous, stratified, cuboidal, columnar, and others. We are interested in the types of normal body tissue for two reasons: 1) cancers are named according to the cells and tissues from which they arise, and you should be familiar with these names, and 2) different histologic types of cancers have different responses to chemotherapy and radiotherapy. Basic Types of Tissue There are four basic types of tissue: 1) epithelial tissue, 2) connective tissue (blood, bone, cartilage) muscle tissue, and 4) nerve tissue. The primary tissues are divided into subtypes, which we will discuss shortly. Each tissue type is designed to perform a specific function. For instance, nerve tissue conducts nerve impulses, muscle tissues are contractile, and epithelial tissues cover body parts. Tissues differ in several ways: 1) according to the size, shape, and arrangement of their cells; 2) according to the kind or intercellular substance; and 3) according to location and function. tissue are the skin and the mucosa and serosa that line the body cavities and internal organs, such as intestines, urinary bladder, uterus, etc. In some cases, epithelial tissue extends into deeper tissue layers to form glands, such as mucus-secreting glands. The term carcinoma is reserved for malignant growth arising from epithelial cells. Epithelial cells are tightly packed together in sheets and have very little intercellular material between them. Securing the epithelium to the underlying connective tissue is a membrane called the basement membrane. Since epithelial tissue has no blood vessels, it receives nourishment from nutrients that diffuse from blood vessels in the underlying connective tissue. Dead and injured epithelial cells are constantly being replaced by new cells. Epithelial tissue always has a free surface exposed to the outside (eg, skin) or to an open space internally (eg, the uterus). Epithelial tissue is concerned with protection, secretion, absorption, and filtration. For example, the surface layer of the skin, the epidermis, has tightly packed epithelial cells and protects the body from the elements; epithelial cells in glands secrete various liquids; epithelial cells in the small intestine absorb nutrients into the bloodstream, and so on. Epithelial tissue may be a single layer thick or several cell layers thick, as shown in Figure 15. The cell layers are arranged in thin sheets, called membranes, that are firmly attached to the underlying connective tissue by a permeable basement membrane. Epithelial tissue is classified into subtypes, according to the shape, arrangement, and function of cells. For instance, an epithelial membrane composed of single layers of cell is called simple; those several cell layers thick are called stratified. Thin, flat epithelial cells are called squamous (platelike); cube-like cells are called cuboidal; and tall, column-like cells are...