1. Tissues and a Introduction to the Epithelium

2. Levels of Organization atoms→molecules→organelles→cells →tissues

3. In the body, tissues can be classified into the following functions: Epithelial – cover 1 Connective – support 2 Movement – muscle 3 Control – nervous 4

5. Epithelial Tissues Epithelial cells can be classified into 2 types, those that cover surfaces and cavities and those that form a glandular function.

6. Epithelial tissues have the following functions: Protection Absorption Filtration Excretion Secretion Sensory Reception

7. Characteristics of epithelial tissues: Epithelial cells have an upper or free surface.

8. Characteristics of epithelial tissues: Epithelial cells have an upper or free surface. This is known as the Apical Surface

9. Polarity The apical surface can be modified by microvilli or cilia. Microvilli are seen with cells associated with absorption.

10. Polarity The microvilli can be so thick that it can be described as a brush boarder.

11. Polarity The bottom side of the epithelial cell is called the basal surface. It is supported by a non cellular, adhesive sheet called the basal lamina.

12. Polarity The basal lamina is made of glycoproteins that are secreted by the basal region of the epithelial cell. Remember the RER→Golgi→Vesicle s→Secretion ?

13. Specialized Contacts Epithelial cells have contact with each other. These lateral contacts are the desmosomes and tight junctions.

14. Specialized Contacts The tight junction forms an impermeable junction between each cell and thus prevents diffusion between the cells.

15. Specialized Contacts The desmosomes help hold the cell’s shape with anchoring junctions scattered between each cell.

16. Connective Tissue Support The basilar surface attached to a connective tissue net work. There are two parts. The first is the basal lamina secreted from the epithelial cell. The second is the reticular lamina that is made of collagen which is produced by fibroblasts.

17. Connective Tissue Support Together the basal lamina and reticular lamina form the basement membrane. This forms the foundations which anchor the epithelial cells.

18. Avascular but Innervated Epithelial cells do not have a blood supply They depend on diffusion for the delivery of nutrients and removal of wastes. They do have a nerve supply, innervated, for sensory function.

19. Regeneration Do to their protective function; epithelial cells need to be continually replaced. Mitotic figures are not uncommon.

20. Cancer Many cancers are of epithelial origin. The greater the mitotic index, the greater the chance of cancer.

22. Cancer Types

23. Lung cancer caused by smoking typically starts in the bronchial epithelium

24. 1 Picture & 1000 words