Where Can The Epithelial Tissue Be Found – The term tissue is used to describe a group of cells found together in an organism. The cells within the tissue have a common embryonic origin. Microscopic observation shows that the cells in the tissue have morphological characteristics and are arranged in an orderly pattern that achieves the functions of the tissue. From an evolutionary point of view, tissues appear in more complex organisms. For example, multicellular protists, the ancient eukaryotes, do not have cells that organize into tissues.

Although there are many different types of cells in the human body, they fall into four major tissue categories: epithelial tissue, connective tissue, muscle, and nervous tissue. Each of these categories is characterized by specific functions that contribute to the overall health and maintenance of the body. Failure of the structure is a sign of injury or disease. Such changes can be detected histologically, by microscopic examination of the appearance, organization and functioning of tissues.

Where Can The Epithelial Tissue Be Found

Epithelial tissue, also known as epithelium, refers to the layers of cells that cover the external surfaces of the body, line internal cavities and passages, and form certain glands. Connective tissue, as the name suggests, connects the cells and organs of the body and functions to protect, support and integrate all parts of the body. Muscle tissue is excitable, responds to stimulation and contracts to provide movement, and occurs in three main types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle. Nervous tissue can also be stimulated, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body (Figure 1).

What Is The Structure Of Simple Columnar Epithelium? What Purpose Does It Serve?

Figure 1: Four types of tissue: Body. Examples of the four types of tissue are nervous tissue, stratified squamous tissue, cardiac muscle tissue, and connective tissue of the small intestine. Clockwise from neural tissue, LM × 872, LM × 282, LM × 460, LM × 800. (Micrographs courtesy of the Directors of the University of Michigan School of Medicine © 2012)

The next level of organization is the organ, where multiple tissues combine to form a functional unit. Just as knowing the structure and function of cells helps you study tissues, knowing tissues helps you understand how organs work. Epithelial and connective tissues are discussed in detail in this chapter. Muscle and nerve tissues will only be discussed briefly in this chapter.

A tissue membrane is a thin layer or layer of cells that covers the outside of the body (such as the skin), organs (such as the pericardium), and internal passages leading to the outside of the body (such as the abdominal cavity). ), as well as the lining of movable joint cavities. There are two basic types of tissue membranes: connective tissue and epithelium (Figure 3).

Figure 3: Tissue membranes. The two broad categories of tissue membranes in the body are (1) connective tissue membranes, which include joint membranes, and (2) epithelia, which include mucous membranes, serous membranes, and dermis, or in other words, skin.

Unit 6: Tissue Structure And Functions

Epithelial tissues cover the outside of organs and structures in the body and line the lumens of organs in a single layer or multiple layers of cells. The types of epithelia are classified based on the shape of the cells present and the number of cell layers. An epithelium consisting of a single layer of cells is called a simple epithelium; epithelial tissue consisting of several layers is called stratified epithelium. (Fig. 4) summarizes the different types of epithelial tissue.

Figure 4: Epithelial tissue cells. Simple epithelium is organized as a single layer of cells, and stratified epithelium is made up of several layers of cells.

Squamous cells are usually round, flat, and have a small, centrally located nucleus. The outline of the cell is somewhat irregular and the cells fit together to form a covering or lining. When cells are arranged in a single layer (simple epithelium), they facilitate diffusion in tissues such as the lungs in areas of gas exchange, and the exchange of nutrients and waste products in blood capillaries.

Figure 5. Squamous cells (a) are slightly irregular in shape and have small, centrally located nuclei. These cells can be layered as in (b) in this human cervix sample. (b credit: modification of Ed Uthman; scale bar data by Matt Russell)

Tissues, Organs, & Organ Systems (article)

(Fig. 5) illustrates a layer of squamous cells whose membranes join together to form an epithelium. Picture (Figure 5)b shows squamous cells located in layered layers, where the body needs to be protected from external wear and damage. This is called stratified squamous epithelium and occurs in the skin and tissues lining the mouth and vagina.

Cuboidal epithelial cells (Figure 6) are cuboidal with a single central nucleus. They are most often found in a single layer that represents a simple epithelial layer in glandular tissues throughout the body where glandular material is made and secreted. They are also found in the walls of the tubules and in the ducts of the kidney and liver.

Figure 6: Simple cuboidal epithelial cells line tubules in the mammalian kidney, where they participate in blood filtration.

Columnar epithelial cells are taller than they are wide: they resemble a cluster of columns in an epithelial layer and are most often found in a monolayer arrangement. In the digestive tract, the nuclei of the columnar epithelial cells appear to line up at the base of the cells, as shown in Figure 7. These cells absorb the material from the lumen of the digestive tract and prepare it for entry into the body through the circulatory and lymphatic systems.

Epithelial Tissue The Outer Shell.

Figure 7. Simple columnar epithelial cells absorb the substance from the digestive system. Goblet cells secrete mucus into the lumen of the digestive tract.

The columnar epithelial cells lining the airways appear stratified. However, all cells are attached to the basement membrane of the tissue, so they are simple tissues. The nuclei are located at different levels in the cell layer, making it appear as if there is more than one layer, as shown (Figure 8). This is called pseudostratified columnar epithelium. This cellular covering has cilia on the apical or free surface of the cells. Cilia enhance the outflow of mucus and trapped particles from the airways, helping to protect the system from invasive microorganisms and harmful substances inhaled into the body. Goblet cells are located in some tissues (such as the lining of the trachea). Goblet cells contain a mucous membrane that traps irritants, which in the case of the trachea prevents these irritants from entering the lungs.

Figure 8. Pseudostratified columnar epithelium lines the airways. They exist in one layer, but the arrangement of the cores at different levels gives the appearance of more than one layer. Goblet cells interspersed between the columnar epithelial cells secrete mucus into the airways.

Connective tissues are composed of a matrix consisting of living cells and a non-living material called matrix. Ground material consists of organic material (usually protein) and inorganic material (usually mineral or water). The main cell of connective tissue is the fibroblast. This cell produces the fibers found in almost all connective tissue. Fibroblasts are motile, able to perform mitosis and synthesize the necessary connective tissues. Macrophages, lymphocytes and occasionally leukocytes are also found in some tissues. Some tissues have specialized cells that are not found in others. The matrix in connective tissues gives the tissue its density. If a connective tissue has a high concentration of cells or fibers, it has a proportionally less dense matrix.

Epithelium: What It Is, Function & Types

The organic part or protein fibers found in connective tissues are collagen, elastic or reticular fibers. Collagen fibers give strength to the tissue, preventing it from tearing or separating from the surrounding tissue. Elastic fibers are made of the protein elastin; this fiber can stretch up to half its length and return to its original size and shape. Elastic fibers provide elasticity to fabrics. Reticular fibers are the third type of protein fibers found in connective tissues. This fiber consists of thin collagen fibers that form a network of fibers to support the tissues and other organs to which they are attached. Below is a summary of the different types of connective tissue, the types of cells and fibers they are made of, and the locations where the tissues are sampled.

Loose connective tissue, also known as areolar connective tissue, is sampled from all components of connective tissue. As illustrated in (Figure 9), there are some fibroblasts in the loose connective tissue; macrophages are also present. Collagen fibers are relatively wide and light pink in color, while elastic fibers are thin and dark blue to black in color. The space between the formed elements of the tissue is filled by the matrix. The substance in the connective tissue gives it a loose consistency that resembles a pulled cotton ball. Loose connective tissue is found around all blood vessels and helps hold the vessel in place. Tissue is found around and between most body organs. In summary, areola tissue is hard,

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