Chapter 4 Histology - Chapter 4 Histology: The Study of...

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Chapter 4 Histology: The Study of Tissues Histology Tissue is a Group of similar cells common embryonic origin common function Histology study of tissues Pathologist looks for tissue changes that indicate disease Tissues and Histology Tissue Level of Organization Epithelial Connective Muscle Nervous Tissues and Histology Epithelial Tissue covers surfaces because cells are in contact lines hollow organs, cavities and ducts forms glands when cells sink under the surface Connective Tissue material found between cells supports and binds structures together stores energy as fat provides immunity to disease Tissues and Histology Muscle Tissue cells shorten in length producing movement Nerve Tissue cells that conduct electrical signals detects changes inside and outside the body responds with nerve impulses Embryonic Tissue Germ layers Endoderm Inner layer Forms lining of digestive tract and derivatives Mesoderm Middle layer Forms tissues as muscle, bone, blood vessels
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Ectoderm Outer layer Forms skin and neuroectoderm Epithelium Characteristics Consists almost entirely of cells Covers body surfaces and forms glands Has free and basal surface Specialized cell contacts Avascular Undergoes mitosis Functions of Epithelia Protecting underlying structures Acting as barriers Permitting the passage of substances Secreting substances Absorbing substances Classification of Epithelium Classified by arrangement of cells into layers simple = one cell layer thick stratified = many cell layers thick pseudostratified = single layer of cells where all cells don’t reach apical surface nuclei at found at different levels so it looks multilayered Classified by shape of surface cells squamous =flat cuboidal = cube-shaped columnar = tall column transitional = shape varies with tissue stretching Simple Squamous Epithelium Single layer of flat cells lines blood vessels (endothelium), body cavities (mesothelium) very thin --- controls diffusion, osmosis and filtration nuclei centrally located Cells in direct contact with each other Examples of Simple Squamous Surface view of lining of peritoneal cavity Section of intestinal showing serosa Simple Cuboidal Epithelium Single layer of cube-shaped cells viewed from the side Nuclei round and centrally located Lines tubes of kidney Absorption or secretion
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Chapter 4 Histology - Chapter 4 Histology: The Study of...

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