Tissues

1. Tissues

2. Tissue • A group of similar cells, usually of similar embryonic origin, that function together to carry out specialized activities

3. Histology • The science that deals with the study of tissues • Pathologist – a scientist who specializes in laboratory studies of cells and tissues to make accurate diagnoses. A pathologist examines tissues for any changes that might indicate disease.

4. Types of Tissues • Epithelial Tissue • Covers body surfaces; lines body cavities, hollow organs and ducts; forms glands • Connective Tissue • protect and supports the body and its organs, binds organs together, stores energy reserves as fat, provides immunity • Muscular Tissue • Generates the force needed to make body structures move • Nervous Tissue • Detects changes inside and outside the body and initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis

5. Cell Junctions • Points of contact between plasma membranes of different cells that join them into functional units.

6. Epithelial Tissue • AKA Epithelium • 2 types: • Covering and Lining Epithelium • Forms the outer covering of the skin and some internal organs. It also lines body cavities, blood vessels, ducts, and the interiors of many of the body systems. • Glandular Epithelium • Makes the secreting portion of glands

7. General Features of Epithelium • 1. Closely packed cells with little extracellular material between them arranged in sheets • 2. Surfaces: • Apical Surface – exposed to a body cavity, the outside of the body or lining an internal organ • Lateral Surface – Face adjacent cells • Basal Surface – bottom layer attached to a basement membrane (extracellular structure composed mainly of fibers located between epithelium and underlying connective tissue)

8. General Features of Epithelium • 3. Avascular – no blood vessels. Epithelial cells must get their nutrients from underlying connective tissue through diffusion • 4. Innervated (have a nerve supply) • 5. High mitotic rate – high capacity for cell division because of wear and tear and injury

9. Covering and Lining Epithelium – Cell Shapes • Squamous – flat cells that attach to each other like tiles • Allows for rapid passage of substances through them • Cuboidal – cells are as tall as they are wide, sometimes contain microvilli • Function in Secretion and Absorption • Columnar – Taller than they are wide, sometimes contain microvilli or cilia • Function in Secretion, Absorption and Protection • Transitional – Cells that have the ability to change shape from Cuboidal to Squamous and back as organs stretch

14. Simple Epithelium • A single layer of cells found in areas where diffusion, osmosis, filtration, secretions and absorption occur

15. Simple Squamous Epithelium • A single layer of flat cells that resembles a tile floor when viewed from the apical surface • Nucleus is a flattened oval found in the center of the cell • Found where filtration or diffusion take place, not found in areas of high wear and tear

16. Simple Squamous Epithelium • Endothelium – simple squamous that lines the heart, blood vessels and lymphatic vessles • Mesothelium – simple squamous that lines serous membranes (lines cavities not open to the outside of the body, like the abdomen or thorax)

17. Simple Cuboidal Epithelium • Single layer of cube shaped cells • Found on the surface of the ovary, the lens of the eye and lining of glands as well as the secreting portion of glands • Function in Secretion and Absorption

18. Simple Columnar Epithelium • Single Layer of Column Shaped Cells • 2 Forms – cilliated and noncilliated

19. Non-cilliated Simple Columnar Epithelium • Contains absorptive cells and goblet cells • Absorptive Cells – have microvilli to increase surface area • Goblet Cells – modified Columnar cells that secrete mucus at the apical surface • Lines most of the GI tract, ducts of glands and gallbladder

22. Ciliated Simple Columnar Epithelium • Cells with cilia at the apical surface, usually interspersed with goblet cells • Mucus secreted by goblet cells forms a thin layer over the cell surface which is moved by the ciliated cells. • Found in the respiratory tract

24. Stratified Epithelium • Contains 2 or more layers of cells used for protection of underlying tissue in area where there is a lot of wear and tear • The name of the tissue depends on the shape of the cell on the apical layer

26. Stratified S quamous Epithelium • Cells in the apical layer are flat • Cells in the deep layers vary in shape • Basal cells continuously undergo mitosis • As they move farther from the basal layer they become dehydrated and harder

27. Keratinized Stratified Squamous Epithelium • Tough layer of keratin is deposited on the top layers to help protect the skin and underlying tissues from microbes, heat and chemicals

28. Nonkeratinized Stratified Squamous Epithelium • Does not contain keratin • Found on the lining of the mouth, esophagus, and tongue

29. Stratified Cuboidal Epithelium • Fairly Rare • 2 or more layers of cells, apical layer is cuboidal • Found in sweat glands

30. Stratified Columnar Epithelium • Fairly Rare • 2 or more layers of cells, the top layer is columnar • Found in excretory ducts of some glands and some mucous membranes

31. Transitional Epithelium • Varies in appearance depending on whether the organ it lines is distended or relaxed. • Looks similar to stratified cuboidal except the top layer is large and rounded

33. Pseudostratified Columnar Epithelium • Appears to have several layers because the nuclei of the cells are at various depths. • All of the cells are attached to the same basement membrane so there is only 1 layer of cells

35. Glandular Epithelium • Functions in Secretion • A gland consists of one cell or a group of cells • Endocrine Glands – secretions enter the interstitial fluid • Hormones • Exocrine Glands – secrete their products into ducts (tubes) that empty at the surface of the covering/lining epithelium • Mucus, oil, earwax, digestive enzymes