Types of Tissues (Magill’s Medical Guide, Sixth Edition)
Histology is the study of tissues, which are groups of similar cells that are closely interrelated in their function and are organized together by location and structure. The four major types of tissues are epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
Epithelial tissue (or epithelia) includes those tissues that originate in broad, flat surfaces. Their functions include protection, absorption, and secretion. Epithelia can be one-layered (simple) or multilayered (stratified). Their cells can be flat (squamous), tall and thin (columnar), or equal in height and width (cuboidal). Some simple epithelia have nuclei at two different levels, giving the false appearance of different layers; these tissues are called pseudostratified. Some simple squamous epithelia have special names: The inner lining of most blood vessels is called an endothelium, while the lining of a body cavity is called a mesothelium. Kidney tubules and most small ducts are also lined with simple squamous epithelia. The pigmented layer of the retina and the front surface of the lens of the eye are examples of simple cuboidal epithelia. Simple columnar epithelia form the inner lining of most digestive organs and the linings of the small bronchi and gallbladder. The epithelia lining the Fallopian tube, nasal cavity, and bronchi are ciliated, meaning that the cells have small hairlike extensions called cilia.
The outer layer of skin...
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Histology as a Diagnostic Tool (Magill’s Medical Guide, Sixth Edition)
Many diseases produce changes in one or more body tissues; these changes are so characteristic that the diagnosis of a disease often depends on the microscopic observation of changes in tissues. For such a diagnosis to be made, the tissue must be sliced very thin on a machine called a microtome. Some tissues are sliced while frozen; others must be hardened (or “fixed”) in chemical solutions. After being sliced, the tissue is usually stained with chemical dyes that make viewing easier. Some tissues are viewed under the light microscope; others are sliced even thinner for viewing by electron microscopy.
Most hospitals have a pathology department that is responsible for these operations. After the tissues are sliced and examined, the pathologist makes a report that usually includes a diagnosis of the disease shown by the tissue samples.
Many diseases result in marked changes in the tissue at the microscopic level. Adaptively altered changes, which are usually reversible, include an increase in cell size (hypertrophy), increase in cell numbers (hyperplasia), a change from one cell or tissue type to another (metaplasia), and a decrease in size by withering (atrophy). Prolonged or repeated insults to the tissue may result in altered or atypical growth patterns (dysplasia). Overwhelming or sustained injury results in irreversible changes such as tissue degeneration or death. Tissue degeneration often...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
The microscopic study of tissues began historically with Robert Hooke’s Micrographia (1665) and the studies of Marcello Malpighi (1628-1694), but early microscopes were low in quality by today’s standards. As microscopes improved, so did their use in studying tissues. During the 1830’s, the Scottish botanist Robert Brown (1773-1858) discovered the cell nucleus. Soon, German biologists Matthias Jakob Schleiden (1804-1881) and Theodor Schwann (1810-1882) developed the so-called cell theory, a theory which proclaimed that all living things are constructed of cells and that all biological processes are rooted in processes occurring at the level of cells and tissues. The greatest advances in microscopic optics were made between 1870 and 1900, mostly in Germany, and the study of histology benefited greatly.
The great pathologist Rudolph Virchow (1821-1902) was the first to emphasize the structural changes in cells caused by the disease process; he showed that many diseases could be detected at the cellular level under the microscope. This claim, coupled with enthusiasm for the cell theory, aroused great interest in the study of cells throughout Europe and later in America. Advances in tissue-staining techniques in microanatomy were made in various countries over a long period; the Czech histologist and physiologist Jan Evangelista Purkinje (1787-1869) was one of the leaders of this early period. Early in...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Fawcett, D. W. A Textbook of Histology. 12th ed. New York: Chapman & Hall, 1994. A classic standard, well illustrated with a variety of light micrographs (often in color) and electron micrographs. Most thorough in its descriptions of physiological functions.
Junqueira, Luiz Carlos, and José Carneiro. Junqueira’s Basic Histology: Text and Atlas. 12th ed. New York: McGraw-Hill Medical, 2010. A leading text that describes the structure and function of cells and the function and specialization of the four tissue groups: epithelial, connective, adipose, and nerve. Also includes chapters on the cytoplasm and cell nucleus that review recent discoveries in cell biology.
Kerr, Jeffrey B. Atlas of Functional Histology. Reprint. St. Louis, Mo.: Mosby/Elsevier, 2006. This volume includes discussion of histology as it applies to the major biological systems, such as the endocrine, respiratory, reproductive, gastrointestinal, nervous, and circulatory systems.
Kessel, Richard G. Basic Medical Histology: The Biology of Cells, Tissues, and Organs. New York: Oxford University Press, 1998. This textbook is derived from Kessel’s notes, figures, and references accumulated over thirty-five years of teaching histology at the University of Iowa. Suitable for advanced undergraduate students in biology or possibly first-year medical students.
Lewin, Benjamin. Genes IX....
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