Introduction to Histology

1. PULSE October 7, 2009 Introduction to Histology

2. What is Histology? -The study of tissues -But, what does all this mean? -Put simply, it’s microanatomy!

3. But Why Do We Really Care? Not so much! BORING!!!!! • Because…structure correlates with function! • In disease states, normal tissue architecture changes. • If we understand the normal, then we understand the disease! • We can use this information to help us make a diagnosis and possibly even to guide treatment.

4. Histology Basics • Cells are the basic structural and functional unit of the human body • All disease processes can be traced back to an underlying defect in the cell • BUT…We want the BIG PICTURE!!!!!! • CellsTissuesOrgansOrgan Systems

5. What is a Tissue? • There are four basic types of tissues that come together to comprise organs: • 1) Epithelium • 2) Connective tissue • 3) Muscle • 4) Nervous tissue

6. Epithelium Epithelium is a type of tissue that lines the surfaces of the body as well as the surfaces of body cavities (e.g. the gastrointestinal and respiratory tracts) In addition, many glands (endocrine and exocrine) are also formed from epithelial tissue.

7. Epithelium • Classification: • By cell shape: • Squamous: Flat, “pancake-shaped” cells; flat nuclei • Cuboidal: Cube-shaped cells equal in width and height; circular nuclei • Columnar: Tall rectangular cells with a height greater than two times the width; stretched nuclei • Transitional: Complex! Not important…yet! • By the number of layers: • Simple: One cell layer • Stratified: Two or more cell layers *The type of epithelium found in a given structure depends on the function of that structure!

8. Stratified Squamous

9. Simple Cuboidal

10. Simple Columnar

11. Connective Tissue • Connective tissue is important in support and strength • It consists of cells (mostly fibroblasts) and extracellular matrix (laid down by the connective tissue cells

12. Connective Tissue: Classification • 1) Connective Tissue Proper • A) Loose connective tissue • B) Dense irregular connective tissue • C) Dense regular connective tissue • 2) Embryonic Connective Tissue • 3) Specialized Connective Tissue • A)Blood • B)Cartilage • C)Bone

13. Loose Connective Tissue • A lot of cells; not a lot of extracellular matrix • Often found beneath epithelial surfaces, around glands • It serves as a place for immune cells to “wait” beneath the epithelial surfaces to attack invading microbes

14. Dense Irregular Connective Tissue • Dense: More extracellular matrix (mostly collagen), less cells • Irregular: Collagen fibers have no specific pattern; wavy • Function: Resists stretching (e.g. found in the deep layer of the skin)

15. Dense Regular Connective Tissue • Dense: More extracellular matrix (mostly collagen), less cells • Regular: Collagen fibers are laid down in rows • Function: STRENGTH! • Found in tendons and ligaments

16. Muscle • Three types • 1) Skeletal • 2) Cardiac • 3) Smooth

17. Skeletal Muscle • Skeletal muscle is what you think about when you hear the term “muscle” • Features: • Multiple nuclei per cell • Nuclei at the periphery of the cell • Striated

18. Cardiac Muscle • Cardiac muscle is the muscle found in the heart • Responsible for pumping blood! • Features: • One nucleus per cell • Nucleus is centrally-located in the cell • Striated • Intercalated discs • Branching pattern

19. Smooth Muscle • Smooth muscle is the muscle found in blood vessels, glands, and the components of the GI tract • This is “involuntary” muscle • We can’t make it contract by thinking about it like we can with our skeletal muscles • Features: • One nucleus per cell • Nucleus is centrally-located within the cell • Not striated • “Spindle-shaped” cells and nuclei

20. Nervous Tissue • Pretty complex! • We won’t cover it today!

21. Microscope Etiquette -One more important thing before we start the laboratory exercise