Chapter 5 epith

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Chapter 5 epith

  1. 1. Chapter 5 Epithelial Tissue
  2. 2. EPITHELIAL TISSUE <ul><li>It is the basic tissue which covers surface areas: the fill spaces, surfaces and the cavities of the body. </li></ul>
  3. 3. There are three types of epithelial tissues: <ul><li>1. Covering and lining </li></ul><ul><li>2. Glandular </li></ul><ul><li>3. Sensory </li></ul>
  4. 4. Characterisitics of epithelial cells: <ul><li>1. They are contiguous (i.e., the cells are attached to one another or closely packed). </li></ul><ul><li>2. The cells rest on an extracellular matrix which they produce, called the basement membrane which acts as a semi permeable membrane where they get their nutrients. </li></ul><ul><li>3. Epithelia are avascular . This means that blood vessels do not penetrate up between these cells, as they do in connective tissue and muscle cells. </li></ul><ul><li>4. A major component of epithelial tissue is the intermediate filament called keratin. </li></ul>
  5. 5. Three features are important in the classification of epithelium: <ul><li>1. Shape </li></ul><ul><li>A. squamous -very flat cells </li></ul><ul><li>B. cuboidal - taller than squamous cells, all four sides approximately equal </li></ul><ul><li>C. columnar - cell length is greater than cell width </li></ul><ul><li>2. Number of Layers of cells in the epithelium: </li></ul><ul><li>A. simple - a single layer of cells; all cells sit on the basement membrane. </li></ul><ul><li>B. stratified - several cells stacked upon one another; not all cells touch the basement membrane. The shape of the apical stratum determines the &quot;shape&quot; designation of the epithelium. </li></ul><ul><li>Pseudo stratified - a simple epithelium, but gives the illusion of being stratified. All cells do sit on the basement membrane, but not visually apparent because the nuclei are at various levels. </li></ul>
  6. 7. Simple cuboidal epithelium is found in glandular tissue and in the kidney tubules. Simple columnar epithelium lines the stomach and intestines. Pseudostratified columnar epithelium lines portions of the respiratory tract and some of the tubes of the male reproductive tract. Transitional epithelium can be distended or stretched. Glandular epithelium is specialized to produce and secrete substances.
  7. 8. Simple Squamous Ep <ul><li>Flat shape characteristic of typical &quot;squamous cells.&quot; The nucleus (A) is centrally located, the cell membrane (C) is very thin, and the cell is filled with cytoplasm (B). </li></ul><ul><li>Locations : Capillary walls, alveoli of the lungs, covering visceral organs, lining body cavities </li></ul><ul><li>Function: diffusion and filtration </li></ul>
  8. 9. Simple Cuboidal <ul><li>In kidney tissue we find the kidney's tubules cut such that they appear as rings of cells around empty spaces. These cuboidal cells (A) that line these tubules are as wide as they are tall as they are deep - cuboidal. The nuclei (B) are easily observed. </li></ul><ul><li>Locations: lining kidney tubules, salivary ducts, pancreatic ducts </li></ul><ul><li>Functions: secretion, excretion, and absorption </li></ul>
  9. 10. Simple Columnar <ul><li>The villi of the small intestine are lined by a single layer of columnar cells (A) - thus the name simple columnar epithelium. Note these cells are not as wide as they are tall with the darkly stained nuclei (B) located at the base of the cells.The cell membranes (C) are very thin but easily identified. </li></ul><ul><li>Locations: lining most of the digestive tract </li></ul><ul><li>Function: protection, secretion and absorption </li></ul>
  10. 11. 3. Surface Specializations: <ul><ul><li>Microvilli – finger like projections </li></ul></ul>
  11. 12. Cilia <ul><li>Cilia – Hair-like structure </li></ul><ul><li>Goblet – flask like structure </li></ul>
  12. 13. Neuro-epithilium
  13. 14. Psuedostratified Ciliated Columnar Ep. <ul><li>Locations: This is a respiratory epithelium being found in such places as the nasal septum, trachea, and bronchi. </li></ul><ul><li>Function: trap and move &quot;pollutants&quot; to the mouth where they are swallowed </li></ul>
  14. 15. Stratified Squamous <ul><li>The bracket labeled A marks the stratified squamous epithelium.The many layers of cells that make up this tissue are easily seen with higher magnification (right). Observe that the surface cells (at B) are flattened (are squamous). </li></ul><ul><li>Location : mouth, vagina, esophagus, anal canal </li></ul><ul><li>Function: protection </li></ul>
  15. 16. Stratified Cuboidal or Columnar <ul><li>relatively rare. </li></ul><ul><li>Examples are found in larger excretory ducts of salivary glands and portions of the urethra (stratified columnar) and </li></ul><ul><li>the ducts of sweat glands (stratified cuboidal) </li></ul>
  16. 17. Transitional Ep <ul><li>At the left observe the ureter is lined by transitional epithelium (A). At the left the epithelium is more highly magnified. Note that the cells at the exposed surface (A) are large and rounded. They are also larger than the cells at the attached surface (B). </li></ul><ul><li>Locations : ureter, urinary bladder </li></ul><ul><li>Function: distention </li></ul>
  17. 18. GLANDULAR EPITHELIA <ul><li>There are two types of glandular tissue in the body: exocrine and endocrine . </li></ul><ul><li>Exocrine glands secrete through ducts or directly onto an epithelial surface. </li></ul><ul><li>Endocrine glands do not secrete into ducts, but rather secrete into the bloodstream. </li></ul>
  18. 21. Mechanisms of Secretion: <ul><li>Merocrine - Secretory granules released by exocytosis. </li></ul><ul><li>Apocrine - Secretion &quot;pinched off.&quot; </li></ul><ul><li>Holocrine - Cells released as part of secretion. </li></ul>
  19. 22. Merocrine <ul><li>This is the most common type of secretion mechanism. Secretory granules form in the cells and accumulate in the apex. The granules fuse with the plasma membrane and are secreted into the lumen of the gland by exocytosis </li></ul>
  20. 23. Apocrine <ul><li>There are few examples of this type of gland in the body. Secretions in the apex of the cell and a portion of the cell itself (including the plasma membrane) is pinched off for secretion. Some cytoplasm may be discharged with the secretion. An example is the lactating mammary gland </li></ul>
  21. 24. Holocrine <ul><li>In these glands the cell fills with its secretory product while the nucleus becomes smaller. The cell dies and the entire cell is released and disintegrates, releasing its product. </li></ul>
  22. 25. <ul><li>End of Presentation </li></ul><ul><li>Next Meeting </li></ul><ul><li>EXAM! </li></ul>
  23. 26. Serous <ul><li>These secrete enzyme-rich products as in the pancreas or salivary glands. Usually the secretion is watery. </li></ul>
  24. 27. <ul><li>These cells secrete a carbohydrate-rich, viscous secretion. </li></ul><ul><li>Glands found in the soft palate and esophagus are examples. </li></ul>

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