1. TissuesTissues

2. No single cell… Although there are trillions of cells in the human body, there are only about 200 different types of cells Cells types combine to form tissues. –Collections of specialized cells and cell products that perform a limited number of functions. –Histology is the study of tissues

3. 4 basic tissue types Epithelia –Cover exposed surfaces –Line internal passages and chambers –Produce Glandular secretions Connective –Fill internal spaces –Provide structural support –Store Energy

4. 4 basic tissue types con’t. Muscle –Contracts to produce active movement Neural –Conducts electrical impulses –Carries information

5. From the outside in… Epithelial tissue –Epithelia (singular: epithelium) -- covers internal and external surfaces –Glands – secreting cells derived from epithelia

6. Key characteristics of Epithelia Bound closely together A free (apical) surface is exposed to the environment or internal space Attached to other cells by basement membrane Avascular –No blood vessels; cell must obtain nutrients across basement membrane Continually regenerated due to damage or loss

7. Functions of Epithelia Provide physical protection –Against abrasion, dehydration or destructive agents Control permeability Provide sensation –Helps relay info to the nervous system Produce specialized secretions –Individual cells are called gland cells –Entire tissues are called glandular epithelium

8. A note about secretions… If the secretions are discharged onto the surface of the epithelium, they are called exocrine –Ex. Milk, sweat, digestive enzymes If the secretions are released into the surrounding tissue fluid and blood, they are called endocrine –These are hormones; chemical messengers

9. Epithelial Surface AKA Apical Surface Can have specialized structures –Microvilli Small finger-like projections of the cell surface Help increase surface area for absorption and secretion of materials Found in the digestive and urinary tracts –Cilia Short hair like structures Found in the respiratory tract Helps move mucus trapped irritants

10. Classifying epithelia Can be simple or stratified –Simple = 1 layer of cells –Stratified = multiple layers 3 shapes –Squamous – flat like a fried egg –Cuboidal – like little hexagonol boxes –Columnar – like the cuboidal but taller

11. Pictures of epithelia Look at the hand outs of pages 94-96 for the different types of epithelia, both simple and stratified.

12. Connective Tissues

13. The most diverse tissues of the body Made of 3 different components –Specialized Cells –Protein Fibers –Fluid known as Ground Substance The protein fibers and ground substance combine to make up the matrix that surrounds the cells

14. Connective Tissues Never exposed to the outside environment although they are throughout the body Highly vascularized Contain receptors to pain, pressure, temperature, and other sensations

15. Special differences between epithelia and connective tissues Epithelial tissues are composed mainly of cells Connective tissues has a majority of its volume consisting of the extra- cellular matrix

16. Main uses of connective tissues Support & Protection –Help to establish a bony structural framework Transport Materials –Fluid connective tissues are very efficient at moving dissolved materials throughout the body

17. Main uses of connective tissues Storage of Energy Reserves –Adipose cells store energy until needed Defense of the Body –Respond to invaders of the body and produce antibodies

18. 3 Major types of Connective Tissue Connective Tissue Proper –Ex. Tissue under the skin, fat, tendons and ligaments –Has many types of cells and fibers in a syrupy ground substance

19. 3 Major types of Connective Tissue Fluid Connective Tissue –Ex. Blood and Lymph –Has a distinctive cell population in a watery ground substance with dissolved proteins

20. 3 Major types of Connective Tissue Supporting Connective Tissue –Ex. Cartilage and Bone –Less diverse cell population than CTP but has a matrix of dense ground substance and closely packed fibers –Bone is fiberous but calcified to provide rigidity and strength

21. Lets look at the players…

22. Connective Tissue Proper Major Cell Types –Fibroblasts –Macrophages –Fat cells (adipocytes) –Mast Cells Also can include stem cells and cells that produce antibodies

23. Connective Tissue Proper Connective Tissue Fibers –Collagen – long, straight, and unbranched strong and flexible –Elastic – Contain the protein elastin, they are branched and wavy –Reticular – Least common and form a woven branching framework

24. Connective Tissue Proper Ground Substance –Should be clear and colorless –Consistency of maple syrup Density helps slow bacteria and makes it easier for macrophages to consume them

25. Connective Tissue Proper Classified as either Loose or Dense Loose –Areolar Least differentiated, contains all of the cells of CTP Forms a layer that separates skin from underlying muscle –Why you can pinch skin without distorting the muscle

26. Connective Tissue Proper Loose con’t. –Adipose Tissue (Fat) Very similar to Areolar Tissue, just has a majority of adipocytes Found under the skin on the sides, buttocks and breasts

27. Connective Tissue Proper Dense Connective Tissue –Mainly collagen fibers –Tendons – connect skeletal muscle to bone –Ligaments – Connect bone to bone

28. Fluid Connective Tissue Blood –Watery matrix called plasma –Mostly Red Blood Cells (RBC’s) –Some White Blood Cell –Platelets

29. How Fluid Connective Tissues Work Together Plasma is in constant motion in the blood vessels due to contractions of the heart When it gets to capillaries, solutes will dissolve into interstitial fluid (fluid surrounding body cells) As interstitial fluid enters lymphatic vessels, lymph forms –Combines cells of the immune system to monitor the body

30. Supporting Connective Tissue Cartilage –Firm gel matrix containing only chondrocytes –Avascular – why it is difficult to repair –Separated from other tissues by the perichondrium

31. 3 types of Cartilage Hyaline –Tough by flexible, connects ribs to sternum, covers bone surfaces in joints Elastic –Very resilient and flexible, found in the outer ear flap and epiglottis Fibrocartilage –Very little ground substance, mostly collagen fibers –Found between vertebrae, connecting bones in the pelvis

32. Bones will be covered in the skeletal unit!