1. Tissues Whole body contains only 200 different cells types that are organized into tissues The extracellular fluid surrounding the cells organized into tissues is called interstitial fluid Four primary tissue classes –epithelial tissue –connective tissue –muscular tissue –nervous tissue

2. Epithelial Tissue Covers the entire surface of the body –includes skin, lining of the lung, lining of the digestive tract, lining of the urinary tract, lining of the reproductive tract –barrier between what is IN the body and what is OUT of the body –controls what substances enter/exit the body and what substances stay in/out of the body Primary tissue type found in exocrine glands –secrete substances out of the body (sweat, saliva, digestive system juices) Classification of epithelial tissue is based on: –the shape of the cells that make up the tissue –the number of layers of epithelial cells

3. Epithelial Tissue: Basic Structure Made of epithelial cells that are connected to adjacent cells by proteins called tight junctions –create “sheets” of epithelial cells similar in structure to a six-pack of cans Anchored to the body by a structure called the basement membrane Epithelial cells have 2 sides –apical side of the cell faces toward the OUTSIDE of the body –basal side of the cell faces toward the INSIDE of the body

4. Shape of Epithelial Cells Cell shape –squamous (flattened cells) cell width is larger than cell height cells have flat nuclei –cuboidal (cube-like cells) cell width is equal to cell height spherical nuclei –columnar (column-like cells) cell height is larger than cell width tall nuclei

5. Layering of Epithelial Cells Simple –one cell layer thick –transports substances into or out of the body Stratified –more than one cell layer thick –protects body from mechanical damage (abrasion, puncture…) Pseudostratified –one cell layer thick made of cells with differing heights –gives false impression of stratified epithelium

6. Epithelia: Simple Squamous Single layer of squamous epithelial cells

7. Epithelia: Simple Cuboidal Single layer of cuboidal epithelial cells

8. Epithelia: Simple Columnar Single layer of columnar cells

9. Epithelia: Pseudostratified Columnar Single layer of cells with different heights; some do not reach the surface of the body

10. Epithelia: Stratified Squamous Multiple layers of squamous cells with flat nuclei

11. Epithelia: Stratified Cuboidal and Columnar 2-3 layers of cuboidal/columnar cells Both are rare in the body

12. Epithelia: Transitional The shape of the cells will change based on the amount of stress (stretch) on the tissue Can appear as cuboidal or columnar when not stretched or squamous when stretched

13. Connective Tissue Most abundant tissue type 4 primary types –Connective tissue proper loose dense –Cartilage –Bone –Blood

14. Structural Elements of Connective Tissue 3 structural elements (components) of connective tissue Cells Ground substance unstructured (gel-like) material that fills the space between cells (interstitial space) Fibers very large proteins extracellular proteins which make a web-like structure holding tissues together Ground substance + fibers = Extracellular Matrix

15. Structural Elements of Connective Tissue

16. Cells There are 4 different cell types which are responsible for building (blast = “to build”) the 4 different types of connective tissue Fibroblasts –connective tissue proper Chondroblasts –cartilage Osteoblasts –bone Hemocytoblast –blood

17. Fibers 3 primary types of extracellular fibers provide different physical characteristics to connective tissue types Collagen –very thick and strong, do not stretch –provides tough structure to tissue Elastic –thin and strong, allow for stretch and then recoil (return to original length) when released Reticular –thin and fragile, do not stretch –provide delicate structure to tissue

18. Loose Connective Tissue Proper: Areolar

19. Loose Connective Tissue Proper: Adipose Stores lipids to use as fuel, insulation and protection

20. Loose Connective Tissue Proper: Reticular

21. Dense Connective Tissue Proper: Regular Many parallel collagen fibers with a few elastic fibers Attaches muscles to bone (tendons) and bone to bone (ligaments)

22. Dense Connective Tissue Proper: Irregular Many non-parallel collagen fibers with a few elastic fibers

23. Connective Tissue: Cartilage 3 types –Hyaline –Fibrocartilage –Elastic Made of chondrocytes found in a lacuna (“pit”) within the firm but flexible extracellular matrix comprised of a network of collagen fibers