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Epithelial Tissues 1. Epithelial tissues Introduction  They cover the outer body surface and some body organs.  They line cavities of organs and the.

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Presentation on theme: "Epithelial Tissues 1. Epithelial tissues Introduction  They cover the outer body surface and some body organs.  They line cavities of organs and the."— Presentation transcript:

1 Epithelial Tissues 1

2 Epithelial tissues Introduction  They cover the outer body surface and some body organs.  They line cavities of organs and the internal body cavity (peritoneal cavity). Common characteristics  They rest on a basement membrane.  With very little intercellular substance or matrix.  They are never penetrated by blood vessels.  They are able to divide and form new cells. 2

3 Epithelial tissues Classification of epithelial tissues Epithelia tissues are classified according to three structural characteristics: 1.The number of cell layers:  A single layer of epithelial cells is termed simple epithelium.  Epithelium with more than one layer is called stratified epithelium. 3

4 Epithelial tissues Classification of epithelial tissues Epithelia tissues are classified according to three structural characteristics: 2.The shape of the component cells (the shape of the outermost layer in case of stratified epithelia):  Squamous (spindle shape).  Cuboidal.  Columnar. 4

5 Epithelial tissues Classification of epithelial tissues Epithelia tissues are classified according to three structural characteristics: 3.The presence of surface specialization:  Cilia.  Keratin. 5

6 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 1.Simple squamous epithelium:  Cells are arranged in one layer.  Cells are flattened with condensed nucleus.  They are almost found on absorptive or secretory surfaces.  Location:  Found in lung alveoli and wall of Bowman's capsules in kidney.  Form lining of blood vessels (endothelium) and peritoneal cavity (mesothelium). 6

7 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 1.Simple squamous epithelium: 7 Simple squamous epithelium in a Bowman's capsule in kidney. Simple squamous epithelium in a blood capillary.

8 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 2.Simple cuboidal epithelium:  Cells are arranged in one layer.  Cells are square in shape with rounded central nucleus.  The epithelium usually lines small ducts of exocrine glands and small kidney tubules which have secretory and excretory functions, respectively.  Location  Pancreatic ducts  Small collecting tubules of kidney. 8

9 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 2.Simple cuboidal epithelium: 9 Simple cuboidal epithelium in small collecting tubules of kidney. Simple cuboidal epithelium in a pancreatic duct.

10 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 3.Simple columnar epithelium:  Cells are arranged in one layer.  Cells are tall with ovoid and basally located nucleus.  The epithelium usually lines intestine and large kidney tubules which have absorptive and excretory functions, respectively.  Location  Gastrointestinal tract, from stomach to rectum.  Large collecting tubules of kidney. 10

11 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 3.Simple columnar epithelium: 11 Simple columnar epithelium of large collecting tubule in kidney. Simple columnar epithelium in small intestine.

12 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 4.Simple ciliated columnar epithelium:  This epithelium is similar to the previous type, but the free border of the cells have cilia.  Location  Female reproductive tract (Fallopian tubes). 12

13 Epithelial tissues Classification of epithelial tissues A.Simple epithelia 5.Pseudostratified ciliated columnar epithelium:  Another type of simple epithelium (all cells rest on the basement membrane).  Not all cells extend to the surface.  The nuclei of cells lie at different levels giving the epithelium a false stratified appearance.  Location  Lining of trachea and nasal cavities. 13 Pseudostratified ciliated columnar epithelium in trachea

14 Epithelial tissues Classification of epithelial tissues B.Stratified epithelia:  Consisting of two or more layers of cells.  Have a protective function.  The cells of the basal layer are usually cuboidal or short columnar. The cells of the surface layer vary. The intermediate layers are polygonal.  The classification of epithelia is related to the structure of the surface layer. 14

15 Epithelial tissues Classification of epithelial tissues B.Stratified epithelia: 1.Non-keratinized stratified squamous epithelium:  The cells at the free surface are squamous.  The epithelium is adapted to withstand moderate abrasion (friction).  Location  Lining of the oral cavity, pharynx and esophagus. 15 Non-keratinized stratified squamous epithelium

16 Epithelial tissues Classification of epithelial tissues B.Stratified epithelia: 2.Keratinized stratified squamous epithelium:  The cells at the free surface are squamous.  During maturation, the epithelial cells undergo a process called keratinization forming a non-cellular surface layer known as keratin.  The epithelium is adapted to withstand abrasion (friction) and desiccation.  Location  Skin 16 Keratinized stratified squamous epithelium

17 Epithelial tissues Classification of epithelial tissues B.Stratified epithelia: 3.Transitional epithelium:  It is highly specialized to accommodate a great degree of stretch and to withstand the toxicity of urine.  In the relaxed state (bladder is empty), transitional epithelium appears formed of 4-8 layers of cells.  In the stretched state, transitional epithelium appears formed of 2 or 3 layers of cells, and the intermediate and surface layers are extremely flattened.  Location  Lining of urinary bladder, ureters and urethra. 17 Transitional epithelium (relaxed)

18 Epithelial tissues Exocrine glands:  They are glands which discharge their secretory product via (through) a duct.  Exocrine glands can be divided morphologically into:  Simple glands (with a single unbranched excretory duct).  Compound glands (with a branched duct system).  The secretory portion of both simple and compound glands have two main forms:  tubular (the secretory part is tubular).  acinar or alveolar (the secretory part is flask-shaped). 18

19 Epithelial tissues Exocrine glands: 19


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