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Chapter 40 Homeostasis

Chapter 40 Homeostasis - Figure 40.1 Maintaining Internal...

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Figure 40.1 Maintaining Internal Stability
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Systems
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Organs are composed of tissues An organ is composed of tissues, usually of several different types. Cells grouped together with the same characteristics or specializations are called tissues . The four basic types of tissue are epithelial, connective, muscle, and nervous .
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Epithelial cells cover the body and line hollow organs and blood vessels. They come in three shapes: 1. Squamous : flat cells, often serving as permeable boundaries ; found in skin and the lining of the gut. Shown here are stratified (multiple layers) squamous (flattened) from mouth and from skin. Squamous epithelial cells
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Epithelial cells come in three shapes: 2. Cuboidal : cube-shaped cells involved in transport or secretion ; found in lining of ducts of, for example, kidney and thyroid follicles. Cubioidal epithelial cells
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Epithelial cells come in three shapes: 3. Columnar : tall and narrow cells (the apical ends of which may bear cilia) involved in transport ; these are found in the lining of the respiratory tract, the small intestine, and here in the intra-hepatic bile duct Columnar epithelial cells
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Apical and basal ends Epithelial tissues have distinct inner and outer surfaces. The outer surfaces are the apical ends of the epithelial cells. They face the air (skin, lungs) or a fluid-filled organ cavity (the lumen of the gut). Apical ends may have cilia or be highly folded to increase surface area. The inner surfaces are the basil ends; they rest on an extracellular matrix called a basal lamina. Some epithelial tissue, such as skin, gets much wear and tear, and thus has a high rate of cell division and replacement.
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Connective tissue consists of dispersed populations of cells embedded in an extracellular matrix (ECM) that they secrete. A distinguishing feature of different kinds of connective tissue is the protein fiber of which the extracellular matrix is comprised. Here are some examples: Proteoglycans resist compression resistant and line joints . Adipose tissue provides a fuel reserve, cushioning, and insulation with collagen, fibronectin, and laminin in the ECM. Blood is a loose connective tissue made up of cells in a fluid extracellular matrix called blood plasma , containing many different proteins Cartilage and bones contain collagen , which is strong and resists stretch. Chondrocytes in cartilage secrete collagen. Lungs and the walls of blood vessels contain stretchy elastin .
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