Types Of Epithelial Tissue And Their Functions – Question Explain the structure and function of different types of epithelial tissue. Draw a diagram of each type of epithelial tissue.
Solution Epithelial tissue: Most organs and cavities in the body are lined with epithelial cells, which are a thin protective layer. It also acts as a barrier, separating various body systems. Epithelial tissue consists of the skin, the lining of the mouth, the lining of blood vessels, the alveoli of the lungs, and the tubules of the kidneys. Epithelial tissue cells create a continuous layer that is closely packed. Epithelial tissue types: a) Squamous epithelial tissue: Transport of substances occurs through selective permeable surfaces in the cells lining the blood arteries or lung alveoli, this epithelium is a flat type of epithelium. Simple squamous epithelium is the name for this type of epithelium. b) Stratified squamous epithelium: To reduce wear and tear, skin epithelial cells are arranged in several layers. This epithelium consists of layers arranged in a pattern called Stratified squamous epithelium. c) Columnar Epithelium: These tall epithelial cells are where absorption and secretion occur, such as in the inner lining of the intestine. Movement through the epithelial barrier is facilitated by this columnar epithelium. d) Cuboid epithelium: This is the lining of kidney tubules and salivary gland ducts, and provides mechanical support. A multicellular gland can be formed when a piece of epithelial tissue is folded inward. Glandular epithelium is a glandular epithelium. Diagram:
Types Of Epithelial Tissue And Their Functions
Questions similar to P. Explain the structure and function of different types of epithelial tissue. Draw a diagram of each type of epithelial tissue. Q. (a) Name the types of epithelial tissue? (b) What is the basement membrane?Most epithelial tissue is basically a large sheet of cells that covers all the body surfaces exposed to the outside world and the outer layers of the organs. The epithelium also forms many of the body’s glandular tissues. The skin is not the only area of the body exposed to the outside. Other areas are the respiratory tract, the digestive tract, as well as the urinary and reproductive systems, all of which are lined with epithelium. Hollow organs and body cavities that are not connected to the outside of the body, which include blood vessels and serous membranes, are lined with endothelium (plural = endothelia), which is a type of epithelium.
Cell Junctions: Types, Structure And Functions
Epithelial cells originate from three main embryonic layers. The epithelium that covers the skin, parts of the mouth and nose, and the anus develops from the ectoderm. The cells that line the respiratory tract and most of the digestive system come from the endoderm. The epithelium that lines the vessels in the lymphatic and cardiovascular systems originates from the mesoderm and is called the endothelium.
All epithelia share some important structural and functional features. This tissue is highly cellular, with little or no extracellular material between the cells. Adjacent cells form special intercellular connections between their cell membranes called cell junctions. Epithelial cells exhibit polarity with differences in structure and function between the exposed or apical surface facing the cell and the basal surface near the underlying body structure. The basal lamina, a mixture of glycoproteins and collagen, provides a site of epithelial attachment, separating it from the underlying connective tissue. The basal lamina is attached to the reticular lamina, which is secreted by the underlying connective tissue, forming a basement membrane that helps hold everything together.
Epithelial tissue is almost completely avascular. For example, no blood vessels cross the basement membrane to enter the tissue, and nutrients must come by diffusion or absorption from the underlying tissue or water surface. Many epithelial tissues can quickly replace damaged and dead cells. Sloughing off damaged or dead cells is a characteristic of the surface epithelium and allows our airways and digestive tract to quickly replace damaged cells with new cells.
Epithelial tissue provides the body’s first line of defense against physical, chemical, and biological attack and tears. Epithelial cells act as the body’s gatekeepers that regulate permeability and allow selective material transfer across physical barriers. All substances entering the body must cross the epithelium. Some epithelia often include structural features that allow selective transport of molecules and ions across their cell membranes.
Describe Various Types Of Epithelial Tissues With The Help Of Labeled Diagrams
Many epithelial cells are capable of secreting and releasing mucosal chemical compounds specific to their apical surface. The epithelium of the small intestine secretes digestive enzymes, for example. The cells that line the respiratory tract secrete a mucus that traps incoming microorganisms and particles. Glandular epithelium contains many secretory cells.
Epithelial cells are typically characterized by a polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces. Special structures found in some epithelial cells are adaptations to specific functions. Certain organelles are separated on the basal side, while other organelles and extensions, such as cilia, when present, are on the apical surface.
Cilia are microscopic extensions of the apical cell membrane supported by microtubules. They beat in unison and move fluid as well as trapped particles. Ciliated epithelium lines the ventricles of the brain where it helps circulate cerebrospinal fluid. The ciliated epithelium of your airways forms a mucociliary escalator that sweeps dust particles and pathogens trapped in the secreted mucus toward the throat. It is called an escalator because it constantly pushes mucus and trapped particles upwards. Instead, nasal cilia sweep a blanket of mucus down your throat. In both cases, the transported material is usually swallowed, and ends up in the environment of your stomach acid.
Epithelial cells are closely connected and not separated by intracellular material. Three basic types of connections allow varying degrees of interaction between cells: tight junctions, anchoring junctions, and gap junctions (Figure 1).
The Function And Cell Types Of Epithelial Tissue
Figure 1. Types of Cell Junctions. The three basic types of cell-to-cell junctions are tight junctions, gap junctions, and anchoring junctions.
At one end of the spectrum are tight junctions, which separate cells into apical and basal compartments. Anchoring junction includes several types of junction cells that help stabilize the epithelial tissue. Anchoring junctions are common on the lateral and basal surfaces of cells where they provide a strong and flexible connection. There are three types of anchoring junctions: desmosomes, hemidesmosomes, and adherens. Desmosomes occur in patches on the cell membrane. Patch is a structural protein on the inner surface of the cell membrane. Adhesion molecules, cadherins, are attached to these patches and project through the cell membrane to bind with cadherin molecules of adjacent cells. These connections are especially important in holding cells together. Hemidesmosomes, which look like half of a desmosome, connect cells to the extracellular matrix, for example, the basal lamina. While similar in appearance to desmosomes, they include adhesion proteins called integrins instead of cadherins. Adheren junctions use either cadherins or integrins depending on whether they are linked to other cells or the matrix. The junctions are characterized by the presence of contractile protein actin located on the cytoplasmic surface of the cell membrane. Actin can connect isolated patches or form a belt-like structure inside the cell. These junctions affect the shape and fold of the epithelial tissue.
In contrast to tight and anchoring junctions, a gap junction forms an intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions between the cytoplasm of adjacent cells. This junction allows electrical and metabolic coupling of adjacent cells, which coordinate functions in large groups of cells.
Epithelial tissues are classified according to cell shape and the number of cell layers formed (Figure 2). The cell shape can be squamous (flat and thin), cuboidal (box, as wide as tall), or columnar (rectangular, taller than wide). Similarly, the number of cell layers in the tissue can be one, where each cell rests on the basal lamina, which is a simple epithelium, or more than one, which is a stratified epithelium and only the basal layer of cells rests on the basal. lamina. Pseudostratified (pseudo- = “false”) describes tissue with a single layer of irregularly shaped cells that give the appearance of more than one layer. Transition describes the shape of a special stratified epithelium in which the shape of the cells can vary.
Solved Epithelial Tissue4. describe Five General
Figure 2. Epithelial Tissue Cells. Simple epithelial tissue is organized as a single layer of cells and stratified epithelial tissue is formed by several layers of cells.
The shape of the cells in the single cell layer of a simple epithelium reflects the function of their cells. The cells in simple squamous epithelium have the appearance of thin scales. The nucleus of squamous cells tends to be flat, horizontal, and elliptical, mirroring the shape of the cell. The endothelium is the epithelial tissue that lines the lymphatic vessels and cardiovascular system, and is composed of a single layer of squamous cells. Simple squamous epithelium, due to the thinness of the cells, is present where the rapid passage of chemical compounds is observed. Lung alveoli where gas diffuses, parts of renal tubules, and capillary layers are also made of simple squamous epithelial tissue. The mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines the body cavity.
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