Epithelium l General Histology revision for dental students

Epithelium l General Histology and biology revision for dental students

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Epithelium

Introduction

• the human body composed of 4 basic tissue :                        

1.        epitheliual tissue                                                                       
2.        connective tissue                                                                      
3.        muscular tissue                                                                           
4.        nervous tissue

• Epithelial tissue has cells that are very tightly packed together. There is always a free surface associated with epithelial tissue. If a tissue is composed of a conglomeration of cells in tightly packed together, but it does not have a free surface, the tissue is called epithelioid tissue. An example of epithelioid tissue is the parenchyma of the adrenal gland.

• Mesothelium is simple squamous epithelium that lines the abdominal cavity, the pericardial cavity, and the thoracic cavity.

• Endothelium is simple squamous epithelium that lines the vascular system.

• Transitional epithelium is seen in the urinary tract. Transitional epithelium has dome shaped cells on the apical surface. 

• Pseudostratified epithelium is a type of epithelium that has cells which all touch the basement membrane. Pseudostratified epithelium is only one cell layer thick. Pseudostratified epithelium appears stratified, but it is not really stratified. Thus the name. The prefix "pseudo" means false, such as pseudonym or pseudo-science.

• Epithelium that is classified by the number of cell layers and the cell shape. Epithelium that is one cell thick is classified as simple. Epithelium that is more than one cell layer thick is classified as stratified. If the cells are flat, the epithelium is termed squamous. If the cells are as tall as they are wide, it is cuboidal. If the cells are taller than they are wide, the epithelium is classified as columnar.

 

Def. :

• Tissue cover the body from outside & line body cavities from inside

character :

1. Adherent to basement membrane (separate it from underling tissue).
2. Avascular (No blood vessels) but contain nerve endings.
3. Closely adherent with few inter-cellular space.
4. Show continuous degeneration & regeneration.

Simple squamous epith

• The lining of a blood vessel is simple squamous epithelium. This lining is called endothelium. Epithelium lines body cavities and surfaces. Simple squamous epithelium is "simple" because it is one cell thick. "Squamous" refers to the fact that the cells are flat.

Structure:   

1. Flat cells.    
2. Flat nucleus

sites   :

1. A → Alveoli (lung)                 
2. B → Blood vessels
3. S → Serous membranes 

• {Pericardium-Pleura- protenium}
•  Lining of blood vessels → Endothelium.   
•  Lining of serous membranes  → Mesothelium

 

Glandular Epithelium

• A simple gland has an unbranched duct. A compound gland has a branched duct. If the secretory portion of a gland is tube shaped, it is called "tubular". If the secretory portion of a gland is flask shaped, it is called "alveolar" or "acinar". If the secretory portion of a gland is a tube shaped but at the terminus is flask shaped, it is called "tubuloalveolar".