Cuboidal cells Are boxlike approximately as tall as they are wide Columnar

Cuboidal cells are boxlike approximately as tall as

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-Cuboidal cells: Are boxlike, approximately as tall as they are wide. -Columnar cells: Are tall and column shape. Layers -Simple epithelia: Concerned with absorption, secretion, and filtration. Single cell layer, very thin and often passable, protection is not one of their specialties. -Stratified epithelia: They contain at least 2 cell layers. When they regenerate; the basal cells divide and push apically to replace the older surface cells. They are more durable then simple epithelia and protection is their major role. 4 types of simple epithelia Simple squamous epithelium: They are flattened. Most concerned with absorption, secretion, and filtration. Very thin and passable so they are not good for protection. They are found where filtration or the exchange of substances by rapid diffusion is a priority.
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EX: In the kidneys it forms part of the filtration membrane that filters blood to make urine. EX: In the lungs, it forms the walls of the air sacs across which gas exchange occurs. EX: Endothelium: gives a slick friction-reducing lining in lymphatic vessels and in hollow organs of the cardiovascular system. EX: Mesothelium: Is the epithelium found in serous membranes lining the ventral body cavity and covering its organs. •Simple cuboidal epithelium: Has one layer of cell as tall as they are wide. Their functions are secretion and absorption. It forms the walls of the smallest ducts of glands and of many kidney tubules. •Simple columnar epithelium: Single layer of tall, closely packed like sticks cells. It lines the digestive tract from the stomach through the rectum. Their functions are mostly absorption and secretion, and the digestive tract lining has 2 modifications: -Dense microvilli on the apical surface of the absorptive cells. -Tubular glands made mostly of cells that secrete mucus-containing intestinal juice. •Pseudostratified (ciliated) columnar epithelium: They vary in height, they are on the basement of the membrane and only the tallest reach the free surface of epithelium. The short cells give rise to the taller cells. It secretes or absorbs substances EX: The motile cilia propel sheets of dust-trapping mucus away from the lungs. Types of stratified epithelium Stratified squamous epithelium: It is widespread, composed of a lot of layers, it is thick and its well suited for its protection role (basal cells cuboidal and undergo mitosis to keep regenerating the layer from below) in the body. Its free surface cells are squamous, and cells of the lower layers are cuboidal or columnar. The outer layer is keratinized meaning it contains keratin. Its surface cells (apical layers) are constantly being rubbed away and replaced by its division of its basal cells. EX: Epidermis of the skin, a dry epithelium. Transitional epithelium: It forms the lining of hollow urinary organs. Cells of its basal layer are cuboidal or columnar. The apical cells vary in appearance.
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  • Fall '08
  • CARNEGIE

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