{"id":4717,"date":"2020-05-12T13:09:16","date_gmt":"2020-05-12T13:09:16","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/7-3-tissues-3\/"},"modified":"2023-11-30T18:48:36","modified_gmt":"2023-11-30T18:48:36","slug":"7-3-tissues-3","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/7-3-tissues-3\/","title":{"raw":"7.4 Tissues","rendered":"7.4 Tissues"},"content":{"raw":"
\r\n\r\n \r\n\r\n[h5p id=\"534\"]\r\n\r\nFigure 7.4.1 Construction \u2014 It's important to have the right materials for the job.\u00a0\u00a0<\/em>\r\n

The Right Material for the Job<\/h1>\r\nBuilding a house is a big job and one that requires a lot of different materials for specific purposes.\u00a0 As you can see in Figure 7.4.1, many different types of materials are used to build a complete house, but each type of material fulfills certain functions.\u00a0 You wouldn't use insulation to cover your roof, and you wouldn't use lumber to wire your home.\u00a0 Just as a builder chooses the appropriate materials to build each aspect of a home (wires for electrical, lumber for framing, shingles for roofing), your body uses the right cells<\/em> for each type of role.\u00a0 When many cells work together to perform a specific function, this is termed a [pb_glossary id=\"2801\"]tissue[\/pb_glossary].\r\n

Tissues<\/h1>\r\n<\/div>\r\nGroups of connected cells form tissues. The cells in a tissue may all be the same type, or they may be of multiple types. In either case, the cells in the tissue work together to carry out a specific function, and they are always specialized to be able to carry out that function better than any other type of tissue.\u00a0 There are four main types of human tissues: connective, epithelial, muscle, and nervous tissues. We use tissues to build organs and organ systems.\u00a0 The 200 types of cells that the body can produce based on our single set of DNA can create all the types of tissue in the body.\r\n

Epithelial Tissue<\/h1>\r\n[pb_glossary id=\"2814\"]Epithelial tissue[\/pb_glossary]<\/strong>\u00a0is made up of cells that line inner and outer body surfaces, such as the skin and the inner surface of the digestive tract. Epithelial tissue that lines inner body surfaces and body openings is called\u00a0mucous membrane.<\/strong>\u00a0This type of epithelial tissue produces\u00a0mucus<\/strong>, a slimy substance that coats mucous membranes and traps pathogens, particles, and debris. Epithelial tissue protects the body and its internal organs, secretes substances (such as hormones) in addition to mucus, and absorbs substances (such as nutrients).\r\n\r\nThe key identifying feature of epithelial tissue is that it contains a free surface and a basement membrane.\u00a0 The free surface is not attached to any other cells and is either open to the outside of the body, or is open to the inside of a hollow organ or body tube.\u00a0 The basement membrane anchors the epithelial tissue to underlying cells.\r\n\r\nEpithelial tissue is identified and named by shape and layering.\u00a0 Epithelial cells exist in three main shapes: squamous, cuboidal, and columnar.\u00a0 These specifically shaped cells can, depending on function, be layered several different ways: simple, stratified, pseudostratified, and transitional.\r\n\r\nEpithelial tissue forms coverings and linings and is responsible for a range of functions including diffusion, absorption, secretion and protection.\u00a0 The shape of an epithelial cell can maximize its ability to perform a certain function.\u00a0 The thinner an epithelial cell is, the easier it is for substances to move through it to carry out diffusion and\/or absorption.\u00a0 The larger an epithelial cell is, the more room it has in its cytoplasm to be able to make products for secretion, and the more protection it can provide for underlying tissues. Their are three main shapes of epithelial cells: squamous (which is shaped like a pancake- flat and oval), cuboidal (cube shaped), and columnar (tall and rectangular).\r\n\r\n[h5p id=\"535\"]\r\n\r\nFigure 7.4.2 The shape of epithelial tissues is important.\u00a0\u00a0<\/em>\r\n\r\nEpithelial tissue will also organize into different layerings depending on their function.\u00a0 For example, multiple layers of cells provide excellent protection, but would no longer be efficient for diffusion, whereas a single layer would work very well for diffusion, but no longer be as protective; a special type of layering called transitional is needed for organs that stretch, like your bladder.\u00a0 Your tissues exhibit the layering that makes them most efficient for the function they are supposed to perform. There are four main layerings found in epithelial tissue: simple (one layer of cells), stratified (many layers of cells), pseudostratified (appears stratified, but upon closer inspection is actually simple), and transitional (can stretch, going from many layers to fewer layers).\r\n\r\n[h5p id=\"536\"]\r\n\r\nFigure 7.4.3 The layerings found in epithelial tissues is important.\u00a0\u00a0<\/em>\r\n\r\nSee Table 7.4.1 for a summary of the different layering types and shapes epithelial cells can form and their related functions and locations.\r\n

Table 7.4.1 <\/strong><\/p>\r\n

Summary of Epithelial Tissue Cells<\/em><\/p>\r\n\"\"\r\n\r\nSo far, we have identified epithelial tissue based on shape and layering.\u00a0 The representative diagrams we have seen so far are helpful for visualizing the tissue structures, but it is important to look at real examples of these cells.\u00a0 Since cells are too tiny to see with the naked eye, we rely on microscopes to help us study them.\u00a0\u00a0[pb_glossary id=\"2879\"]Histology[\/pb_glossary]<\/strong> is the study of the microscopic anatomy and cells and tissues.\u00a0 See Table 7.4.2 to see some examples of slides of epithelial tissues prepared for the purpose of histology.\r\n\r\nTable 7.4.2<\/strong>\r\n\r\nEpithelial Tissues and Histological Samples<\/em>\r\n\r\n \r\n\r\n\r\n\r\n\r\n\r\n\r\n
Epithelial Tissue Type<\/td>\r\nTissue Diagram<\/td>\r\nHistological Sample<\/td>\r\n<\/tr>\r\n
Stratified squamous\r\n\r\n(from skin)<\/td>\r\n\"\"<\/td>\r\n\"\"<\/td>\r\n<\/tr>\r\n
Simple cuboidal\r\n\r\n(from kidney tubules)<\/td>\r\n\"\"<\/td>\r\n\"\"<\/td>\r\n<\/tr>\r\n
Pseudostratified ciliated columnar\r\n\r\n(from trachea)<\/td>\r\n\"\"<\/td>\r\n\"\"<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n

Connective Tissue<\/h1>\r\nBone and blood are examples of connective tissue.\u00a0[pb_glossary id=\"2815\"]Connective tissue[\/pb_glossary]<\/strong> is very diverse. In general, it forms a framework and support structure for\u00a0body tissues\u00a0and organs.\u00a0It's\u00a0made up of living cells\u00a0separated by non-living material, called [pb_glossary id=\"6005\"]extracellular matrix[\/pb_glossary], which can be\u00a0solid\u00a0or\u00a0liquid.\u00a0The extracellular matrix of bone, for example, is a rigid mineral framework. The extracellular matrix of blood is\u00a0liquid\u00a0plasma.\r\n\r\nThe key identifying feature of connective tissue is that is is composed of a scattering of cells in a non-cellular matrix. There are three main categories of connective tissue, based on the nature of the matrix. They \u00a0look very different from one another, which is a reflection of their different functions:\r\n
    \r\n \t
  1. Fibrous connective tissue: is characterized by a matrix which is flexible and is made of protein fibres including collagen, elastin and possibly reticular fibres.\u00a0 These tissues are found making up tendons, ligaments, and body membranes.<\/li>\r\n \t
  2. Supportive connective tissue: is characterized by a solid matrix and is what is used to make bone and cartilage.\u00a0 These tissues are used for support and protection.<\/li>\r\n \t
  3. Fluid connective tissue: is characterized by a fluid matrix and includes both blood and lymph.<\/li>\r\n<\/ol>\r\n

    Fibrous Connective Tissue<\/h2>\r\nFibrous connective tissue contains cells called [pb_glossary id=\"6011\"]fibroblasts[\/pb_glossary].\u00a0 These cells produce fibres of collagen, elastin, or reticular fibre which makes up the matrix of this type of connective tissue.\u00a0 Based on how tightly packed these fibres are and how they are oriented changes the properties, and therefore the function of the fibrous connective tissue.\r\n\r\n \r\n