1. The Tissue Level of Organization
Four main types of tissue
Epithelial tissue

2. Four Tissue Types
• Epithelial (epithelium)
• Connective
• Muscle
• Nervous

4. Function of Epithelial tissue
• Covers body surfaces
• Lines body cavities and ducts
• Forms glands

5. Functions of Connective Tissue
• Protects and supports body and organs
• Binds organs together
• Storage of energy reserve

6. Function of Muscular Tissue
• Generate force for movement
• Body temperature maintenance

7. Functions of Nervous Tissue
• Initiates nerve impulses
• Body coordination

8. Epithelium
• Two types of epithelium
– Covering and lining
– Glandular

9. Covering and lining epithelium
• Characterized by
– cell arrangement
– cell shape

10. Epithelial cell arrangements
• Simple
– One layer of cells
• Stratified
– Two or more layers of cells
• Pseudostratified
– One layer of cells; appears to have multiple layers

11. Epithelial cell shapes
• Squamous
– Flat, thin, arranged like floor tiles.
• Shape allows for rapid transport
• Cuboidal
– Shaped like cubes (or hexagons)
• Secretion and absorption

12. Epithelial cell shapes
• Columnar
– Tall and cylindrical
• Protect underlying layers of tissue
• May also have cilia, may also secrete and absorb materials
• Transitional
– Shape can change (from columnar to flat)
• Allows body parts to stretch or expand or move

15. Simple squamous epithelium

16. Simple cuboidal epithelium

17. Simple columnar epithelium

18. Pseudostratified columnar epithelium

19. Transitional epithelium

20. Stratified squamous epithelium

21. Stratified cuboidal epithelium
• Rare
• Found in ducts of some glands
(mammary, sweat, salivary, pancreas)

22. Stratified columnar epithelium
• Rare
• Found only in male urethra and lactiferous
ducts

23. Epithelial structure
• Little or no space between cells
• Cells meet at “junctions”.
• Avascular

24. Epithelial structure
• Held in place by underlying connective tissue
• Nutrients supplied by underlying tissue

25. Glandular epithelium
• Has cells that are specialized to produce and
secrete substances into ducts or into body fluids
• gland = 1 or more cuboidal or columnar cell
• secretion
• salivary glands, sweat glands, endocrine glands

26. Exocrine and Endocrine gland
• Endocrine – ductless – secrete products
directly into blood.
– Pituitary, thyroid, adrenal glands
• Exocrine – secretions sent into ducts at skin
surface or organ.

27. Types of ducts

28. Exocrine glands classified by function
• Holocrine
– Cell dies as it secretes; replaced by new cell
• Merocrine
– Cell secretes via exocytosis Golgi produced secretory
vesicles
• Apocrine
– Part of cell pinches off and becomes secretion. Cell
repair itself and repeats