1. EPITHELIAL TISSUE

2. General Features of Epithelium
Consists of packed cells with little extracellular material between them
Cells are arranged in continuous sheets, in either single or multiple layers
Have a free surface and a basal surface
Are avascular : a- without vascular- blood vessels
Have nerve supply
High capacity for renewal by cell division

3. Covering and Lining Epithelium
Classification by shape
Squamous - flat
Cuboidal – cubes or hexagons
Columnar – tall, rectangular and cylindrical
Transitional – range in shape from flat to columnar and often change shape

4. Classification by Arrangement of Layers
Simple – single layer in areas of diffusion, osmosis, filtration, secretion and absorption
Stratified – two or more layers used for protecting underlying tissues
Pseudostratified columnar – contains one layer, appears to have several layers but not all cells reach the surface, ciliated or secrete mucous

5. Types of Epithelial Tissue

7. Simple Squamous Epithelium
Single layer, flat cells, central nucleus
Lines the heart, blood vessels, lymphatic vessels, alveoli, glomerular capsules, and forms the epithelial layer of serous membranes
Function: filtration, diffusion, osmosis, secretion in serous membranes

8. Simple Squamous Epithelium

9. Simple Cuboidal Epithelium
Single layer, cube shaped, central nucleus
Lines the tubes and smaller ducts of the kidneys
Function: secretion and absorption

10. Glomerular Capsules Renal Cortex Simple Cubiodal Epithelium

12. Nonciliated Simple Columnar Epithelium
Single layer, nonciliated, rectangular, cylindrical cells, nucleus at base, contain goblet cells, some have microvilli
Lines GI, respiratory, reproductive and urinary tracts
Function: secretion and absorption

13. Simple Columnar Epithelium in Small Intestine

14. Stratified Squamous Epithelium
Several layers, cuboidal or columnar deep, squamous superficial, basal cells replace surface cells
Keratinized epidermis, nonkeratinized lines the mouth, esophagus, vagina and tongue
Function: protection

15. Stratified Squamous Epithelium

16. Transitional Epithelium
Variable cell shapes, superficial cells squamous when stretched, cuboidal when relaxed
Lines urinary bladder and portions of ureters and urethra
Function: permits organs to stretch without rupturing

17. Transitional Epithelium

18. Pseudostratified Columnar Epithelium
Not true stratified tissue, cells at different layers, all cells attached to basement membrane, only some reach surface
Ciliated lines airways of most of the upper respiratory tract (trachea)
Function: secretion and movement of mucus

19. Ciliated Pseudostratified Columnar Epithelium

20. Glandular Epithelium Endocrine – ductless glands
Pituitary, thyroid, and adrenal glands
Exocrine – glands with ducts
Sweat and salivary glands