Epithelial tissue covers surfaces with an uninterrupted layer of cells. Epithelial tissue comprises an uninterrupted layer of cells. Epithelium covers nearly all external and internal body surfaces.
June 1, 0 Comments Epithelial Tissue Epithelial tissue is a sheet of cells that covers a body surface or lines a body cavity.
Two forms occur in the human body: Covering and lining epithelium— forms the outer layer of the skin; lines open cavities of the digestive and respiratory systems; covers the walls of organs of the closed ventral body cavity. Glandular epithelium— surrounds glands within the body.
Characteristics of epithelium Epithelial tissues have five main characteristics. Polarity— all epithelia have an apical surface and a lower attached basal surface that differ in structure and function.
For this reason, epithelia is described as exhibiting apical basal polarity. Most apical surfaces have microvilli small extensions of the Characteristics of epithelial tissue membrane that increase surface area.
For instance, in epithelia that absorb or secrete substances, the microvilli are extremely dense giving the cells a fuz zy appearance called a brush border. Examples of this would include epithelia lining the intestine and kidney tubules. Other epithelia have motile cilia hairlike projections that push substances along their free surface.
Next to the basal surface is the basal lamina thin supporting sheet.
The basal lamina acts as a filter allowing and inhibiting certain molecules from passing into the epithelium. Specialized contacts— epithelial cells fit close together and form continuous sheets except in the case of glandular epithelia. They do this with tight junctions and desmosomes.
Tight junctions form the closest contact between cells and help keep proteins in the apical region of the plasma membrane. Desmosomes connect the plasma membrane to intermediate filaments in the cytoplasm.
Supported by connective tissue— all epithelia are supported by connective tissue. For instance, deep to the basal lamina is reticular lamina extracellular material containing collagen protein fiber which forms the basement membrane.
The basement membrane reinforces the epithelium and helps it resist stretching and tearing. Regeneration— epithelium have a high regenerative capacity and can reproduce rapidly as long as they receive adequate nutrition.
Classification of Epithelia Epithelium has two names. The first name indicates the number of cell layers, the second describes the shape of its cell. Based on the number of cell layers, epithelia can either be simple or stratified. Simple epithelia— consist of a single cell layer found where absorption, secretion, and filtration occur.
Stratified epithelia— are composed of two or more cell layers stacked on top of each other typically found in high abrasion areas where protection is needed. All epithelial cells have six sides but they vary in height. For this reason, there are three ways to describe the shape and height of epithelial cells.
Squamous cells— are flat and scale-like. Cuboidal cells— are box-like same height and width. Columnar cells— are tall column shaped. Simple squamous epithelium Simple squamous epithelium— are close fitting and flattened laterally.
Two simple squamous epithelia in the body have special names reflecting their location. Endothelium— provides a friction-reducing ling in lymphatic vessels and all hollow organs of the cardiovascular system heart, blood vessels, capillaries.
Mesothelium— is the epithelium found in serous membranes membranes lining the ventral body cavity and covering the organs within it. Simple cuboidal epithelium— consists of a single layer of cells with the same height and width. Functions include secretion and absorption located in small ducts of glands and kidney tubules.
Simple columnar epithelium— is a single layer of tall, closely packed cells that line the digestive tract from the stomach to the rectum.
Functions include absorption and secretion. They contain dense microvilli on their apical surface. Additionally, some simple columnar epithelia may display cilia on their free surface also.
Pseudostratified columnar epithelium— vary in height.Epithelial tissue is composed of cells laid out in sheets with strong cell-to-cell attachments. These protein connections hold the cells together to form a tightly connected layer that is avascular but innervated in nature.
Epithelium (/ ˌ ɛ p ɪ ˈ θ iː l i ə m /) is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs.
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It is strong in relation to its weight, is insulating to heat and electricity, and has desirable acoustic properties. Epithelium Study Guide. Epithelial tissue comprises one of the four basic tissue regardbouddhiste.com others are connective tissue (support cells, immune cells, blood cells), muscle tissue (contractile cells), and nervous regardbouddhiste.com represent various combinations of these four basic tissue types, which thus comprise the entire body.
Epithelial tissue, or epithelium, has the following general characteristics: Epithelium consists of closely packed, flattened cells that make up the inside or outside lining of body areas. There is little intercellular material.