Tell us how you are using our epithelial cells and your study could be featured here on our blog! Join our mailing list Click Here. US Customers only. Click here! Most epithelial tissue is described with two names. The first name describes the number of cell layers present and the second describes the shape of the cells. For example, simple squamous epithelial tissue describes a single layer of cells that are flat and scale-like in shape.
Epithelial Tissue : There are three principal classifications associated with epithelial cells. Squamous epithelium has cells that are wider than they are tall. Cuboidal epithelium has cells whose height and width are approximately the same. Columnar epithelium has cells taller than they are wide.
Simple epithelium consists of a single layer of cells. They are typically where absorption, secretion and filtration occur. The thinness of the epithelial barrier facilitates these processes. Simple epithelial tissues are generally classified by the shape of their cells. The four major classes of simple epithelium are: 1 simple squamous; 2 simple cuboidal; 3 simple columnar; and 4 pseudostratified.
Simple squamous epithelium cells are flat in shape and arranged in a single layer. This single layer is thin enough to form a membrane that compounds can move through via passive diffusion. This epithelial type is found in the walls of capillaries, linings of the pericardium, and the linings of the alveoli of the lungs.
Simple cuboidal epithelium consists of a single layer cells that are as tall as they are wide. The important functions of the simple cuboidal epithelium are secretion and absorption. This epithelial type is found in the small collecting ducts of the kidneys, pancreas, and salivary glands.
Simple columnar epithelium is a single row of tall, closely packed cells, aligned in a row. These cells are found in areas with high secretory function such as the wall of the stomach , or absorptive areas as in small intestine. They possess cellular extensions e. These are simple columnar epithelial cells whose nuclei appear at different heights, giving the misleading hence pseudo impression that the epithelium is stratified when the cells are viewed in cross section.
Pseudostratified epithelium can also possess fine hair-like extensions of their apical luminal membrane called cilia. Both serous and mucous glands are common in the salivary glands of the mouth. Mixed exocrine glands contain both serous and mucous glands and release both types of secretions.
In epithelial tissue, cells are closely packed with little or no extracellular matrix except for the basal lamina that separates the epithelium from underlying tissue.
The main functions of epithelia are protection from the environment, coverage, secretion and excretion, absorption, and filtration. Cells are bound together by tight junctions that form an impermeable barrier.
They can also be connected by gap junctions, which allow free exchange of soluble molecules between cells, and anchoring junctions, which attach cell to cell or cell to matrix. The different types of epithelial tissues are characterized by their cellular shapes and arrangements: squamous, cuboidal, or columnar epithelia. Single cell layers form simple epithelia, whereas stacked cells form stratified epithelia.
Very few capillaries penetrate these tissues. Glands are secretory tissues and organs that are derived from epithelial tissues. Exocrine glands release their products through ducts. Endocrine glands secrete hormones directly into the interstitial fluid and blood stream. Glands are classified both according to the type of secretion and by their structure. Merocrine glands secrete products as they are synthesized. Apocrine glands release secretions by pinching off the apical portion of the cell, whereas holocrine gland cells store their secretions until they rupture and release their contents.
In this case, the cell becomes part of the secretion. In observing epithelial cells under a microscope, the cells are arranged in a single layer and look tall and narrow, and the nucleus is located close to the basal side of the cell. The specimen is what type of epithelial tissue? Which of the following is the epithelial tissue that lines the interior of blood vessels?
Which type of epithelial tissue specializes in moving particles across its surface and is found in airways and lining of the oviduct? The structure of a tissue usually is optimized for its function. Describe how the structure of the mucosa and its cells match its function of nutrient absorption. The mucosa of the intestine is highly folded, increasing the surface area for nutrient absorption.
A greater surface area for absorption allows more nutrients to be absorbed per unit time. In addition, the nutrient-absorbing cells of the mucosa have finger-like projections called microvilli that further increase the surface area for nutrient absorption. Skip to content The Tissue Level of Organization. Learning Objectives By the end of this section, you will be able to: Explain the structure and function of epithelial tissue Distinguish between tight junctions, anchoring junctions, and gap junctions Distinguish between simple epithelia and stratified epithelia, as well as between squamous, cuboidal, and columnar epithelia Describe the structure and function of endocrine and exocrine glands and their respective secretions.
The Epithelial Cell Epithelial cells are typically characterized by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces. Cell to Cell Junctions Cells of epithelia are closely connected and are not separated by intracellular material. Types of Cell Junctions. The three basic types of cell-to-cell junctions are tight junctions, gap junctions, and anchoring junctions.
Classification of Epithelial Tissues Epithelial tissues are classified according to the shape of the cells and number of the cell layers formed Figure. Cells of Epithelial Tissue.
Simple epithelial tissue is organized as a single layer of cells and stratified epithelial tissue is formed by several layers of cells. Goblet Cell. Stratified Epithelium A stratified epithelium consists of several stacked layers of cells. Summary of Epithelial Tissue Cells. Glandular Epithelium A gland is a structure made up of one or more cells modified to synthesize and secrete chemical substances.
Endocrine Glands The secretions of endocrine glands are called hormones. Exocrine Glands Exocrine glands release their contents through a duct that leads to the epithelial surface. Glandular Structure Exocrine glands are classified as either unicellular or multicellular. Types of Exocrine Glands. Modes of Glandular Secretion. These glands secrete oils that lubricate and protect the skin. They are holocrine glands and they are destroyed after releasing their contents.
New glandular cells form to replace the cells that are lost. Epithelial tissues are widespread throughout the body. They form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands.
They perform a variety of functions that include protection, secretion, absorption , excretion, filtration, diffusion , and sensory reception.
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