Human Anatomy & Physiology Eleventh Edition PDF

 Tissue: The Living Fabric In this chapter, you will learn that Tissues are groups of cells similar in structure that perform a common or related function by f irst asking and next...

 Tissue: The Living Fabric In this chapter, you will learn that Tissues are groups of cells similar in structure that perform a common or related function by f irst asking and next asking t hen asking "" "". How do cutaneous, "" How are t issues mucous, ancl serous repaired? membranes differ? then comparing r - and - finally, - - exploring - - - -, Epithelial tissue Developmental Aspects of L - - - - - - - -...J CAREER CONNECTION Watch a video to learn O how the chapter content is used in a rea I hea Ith ca re setting. Go to Mastering A&P® > Study Area > Animations and Videos or use quick access URL https://goo.g l/88srfV 115 116 UNIT 1 Organization of the Body Unicellular (one-cell) organisms are independent little Tissues (tissu = woven) are groups of cells that are similar creatures. Each cell alone obtains and digests its food, ejects its in structure and perform a common or related fu nction. Four wastes, and carries out all the other activities necessary to keep pri mary tissue types interweave to form the "fabric" of the itself al ive. But in the multicellul ar human body, cells do not body. These basic tissues are epithelial, connective, muscle, and operate independently. Instead, they form tight cell communi- nervous tissue. ties that live and work together. If we summarized the role of each primary tissue in a single Individual body cells are special ized, with eac h cell type word, we could say that epithe lial tissue covers, connect ive performing specific functions that help maintain homeostasis tissue suppor/s, muscle tissue ,noves, and nervous tissue con- and benefit the body as a whole. Cell specialization is obvious: trols. However, these words reveal only a fraction of what each Muscle cells look and act differently from skin cells, which in tissue does (Figure 4.1). turn are easy to disti nguish from brain cells. Cell specialization As we explained in Chapter I, tissues are organized into allows the body to function in sophisticated ways, but division organs such as the kidneys and heart. Most organs contain all of labor has certain hazards. When a particular group of cells four tissue types. How these tissues are arranged determines an is indispensable, its injury or loss can disable or even destroy organ 's structure and capabilities. The study of tissues, or his- the body. tology, complements the study of gross anatomy. Together they provide the structural basis for understanding organ physiology. Musc,l e tissue: Contracts to cause movement ,i':.._.!.- - - · Muscles attached to bones (skeletal) ~ - ,1-f,l;~- - - Muscles of heart (cardiac) __..- - Muscles of walls of hollow organs (smooth) Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters ?--- - Lining of digestive tract organs and other hollow organs 'l'--- - Glands (e.g., pancreas)...,....__ _ Skin surface (epidermis) Figure 4.1 Overview of f our basic tissue types: epithelial, connective, muscle, and nervous t issues.  Chapte r 4 Tissue: The living Fabric 117 Tissue samples are fixed, sliced, Epithelial tissue covers body and stained for microscopy surfaces, lines cavities, and forms Learning Outcome glands... List the steps involved in prepari ng animal t issue for Learning Outcomes microscopic viewing.... List several structural and functional characteristics of Microscopy allows us to study tissue structure. Before a speci- epithelial tissue. men can be viewed through a microscope, it must be fixed... Name, classify, and describe t he various types of , (preserved) a nd then cut into sections (slices) thin enough to epithelia, and ind icate their chief f unction(s) and transm it light (in light microscopy) or electrons (in electron location(s). microscopy). Fi nally, the specimen must be stained to enhance.,. Define gland. contrast between structures.... Differentiate between exocrine and endocrine g lands, In light microscopy, the stains are beautifully colored syn- and between multicellular and unicellular gland s. thetic dyes, most of which were origi nally developed by cloth-... Describe how multicellu lar exocri ne glands are classified ing manufacturers. Many dyes co nsist of negat ively charged structura lly and functionally. molecu les (acidic stains) or posit ively c harged molecu les E pithelial tiss ue (ep''i- the' le -ul), or a n epith eliu m (plural: (bas ic stains) that bind within the tissue to macromolecules of epithelia), is a sheet of cells that covers a body surface or lines the opposite charge. Different parts of cells and tissues take up a body cavity (epithe = laid on, covering). Two forms occur in different dyes, disti nguishing different anatomical structures. the body: For trans111ission electron 111icroscopy (TEM), tissue sections Covering and lining epitheliu,n, which forrns the outer layer are stained with heavy metal salts. These metals provide con- of the skin; dips into and lines the open cavities of the trast by deflecting electrons in the beam to different ex te nts. urogenital, digestive, and respiratory systems; and covers Electro n-microscope images are in shades of gray because color the walls and organs of the closed ventral body cavity is a property of light, not of electron waves. However, the irnage may be artificially colored to e nhance contrast. Another kind Glandular epitheliu,n, which fashions the glands of the body of electron microscopy, scanning electron ,nicroscopy (SEM), Epithelia form bou ndaries between different environments, provides three-dimensional pictures of an unsectioned tissue and nearly all substances received or given off by the body rnust surface (Figure 4.2). pass through an epithelium. For example, the epidermis of the skin lies between the inside and the outside of the body. Epithe- lium li ning the uri nary bladder separates underlying cells of the bladder wal l from urine. In its role as a bou ndary-forming tissue, epithelium accom- plishes many functions, including (I) protection, (2) absorption, (3) filtration, ( 4) excretion, (5) secretion, and (6) sensory recep- tion, all of which will be touched upon later in this chapter. Special Characteristics of Epithelium Epithelial tissues have five d istingu ishing characteristics, dis- cussed below. Figure 4.2 Comparison of transmission and scanning elect ron micrographs. TEM (left) shows a th in section of the cell Polarity revealing cilia (tiny hairlike projections of the plasma membrane). All epithel ia have two surfaces that differ in structure and func- SEM (right) shows the surfaces of the cilia. Artificially colored. tion. The apical surface is not attached to surrounding tissue and is exposed to either the outside of the body or the cavity of Preserved tissue we see under the microscope has been an internal organ. The bas al surface is attached to the underly- exposed to many procedures that alter its original condition and ing connect ive tissue (see below). For this reason, we say that introduce minor distortions called a r tifacts. For this reaso n, epithelia exhibit apical-basal polarity. most structures that we view under a microscope are not exactly like those in living tissue. Check Your Understanding 1. What is the purpose of fixing tissue for microscopic viewing? 2. What types of stains are used to sta in tissues to be viewed with a transmission electron microscope? Next to underlying. - - - - - - - - - - For answers, see Answers Appendix. connective tissue 118 UNIT 1 Organization of the Body Although some apical surfaces are smooth and slick, most damaged by hostile substances in the external environment have microvilli, fi ngerlike extensions of the plasma membrane (bacteria, acids, smoke). If and when their apical -basal polar- (