CH 4: Tissues

1. CH 4: Tissues

2. Tissues • Tissues are groups of cells that are similar in structure and function. • Tissues can be solid, semi-solid or liquid. • Histologyis the study of tissues. • There are 4 main types of tissues in the human body: • Epithelial • Connective • Muscular • Nervous

3. Epithelial Tissue (Epithelium) • Covers body surfaces and lines cavities, hollow organs and tubes. It also forms glands. • Cells are closely packed and arranged in sheets of either single or multiple layers. • Bottom surface of epithelium is attached to the basement membrane- fibers that are located between the epithelium and the connective tissue below it.

4. Epithelium continued….. • Avascular- without blood vessels. Epithelium gets nutrients from the adjacent connective tissue. • Has a nerve supply. • Is constantly being regenerated because it suffers so much wear and tear. • There are 2 main types of epithelial tissue: • Covering/Lining epithelium • Glandular epithelium

6. Covering/Lining Epithelium • Outer covering of the skin and some internal organs. • Inner lining of blood vessels, ducts, and body cavities. • Interior of the digestive, respiratory, reproductive and urinary systems.

7. Glandular Epithelium • Consists of glands that secrete substances. • Glands are either endocrine or exocrine. • Endocrine- Secrete hormones that enter the fluid around the cells (interstitial) and eventually the bloodstream (Ex. thyroid) • Exocrine- Secrete substances into ducts that empty onto the surface of a covering/lining epithelium (Ex. Sweat gland)

8. Epithelial Tissue Classification • Epithelial tissue is classified based on the number of cell layers present and the shape of the cells of the tissue. Bio 111-73

9. Number of Layers • Simple- • one layer • usually involved in absorption and/or diffusion • Stratified- • 2 or more layers • Protects underlying tissues from wear and tear

10. Number of Layers Continued.. • Pseudostratified Looks like many layers because not all cells reach the surface and the nuclei lie at different levels

11. Cell Shape • Squamous • Thin and flat and attach to each other like tiles • Easily allow substances to pass through • Cuboidal • Shaped like cubes • Function in secretion or absorption

12. Cell Shape Continued… • Columnar • taller than wide • protect underlying tissues • Transitional • change shape due to stretching or movement of body parts

13. Other modifications • Cilia- Tiny hairs that move substances around outside the cell • Microvilli- Folds that increase surface area for absorption • Goblet cells- embedded in between epithelium and secrete mucus for lubrication or to trap particles

14. Simple Squamous • A single layer of tightly packed thin, flat, irregularly shaped cells • Location: • Lines the heart, blood vessels, and lymphatic vessels • Forms the peritoneum, pericardium and pleural linings • Found in the air sacs of lungs (alveoli) • Function: • Allows for easy diffusion of gases and blood components

15. Simple Squamous – Top View – found in the walls of capillaries and alveoli of lungs

17. Simple Cuboidal • A single layer of tightly packed cube shaped cells. • Location: • Lines kidney tubules, ducts of glands, and secreting parts of glands • Covers the surface of the ovary • Function: • Secretion and absorption

18. Simple Cuboidal Epithelial Tissue – this is of ducts of the kidney

21. Simple Columnar • A single layer of tightly packed rectangular cells • Can be non-ciliated or ciliated • Goblet cells are modified columnar cells that secrete mucus • Non-ciliated have microvilli on the surface of the cells • Non-ciliated Location: • Lines the gastrointestinal tract (from stomach to anus), ducts of many glands, and gall bladder

22. Simple Columnar Continued… • Non-ciliated Function: • Secretion and absorption • Ciliated Location: • Lines tubes of the respiratory tract, fallopian tubes, uterus, and ventricles of the brain • Ciliated Function: • The cilia beat in unison to move substances outside the cell like mucus and egg cells.

23. Simple Columnar Non-Ciliated Epithelial Tissue - This is a cross section through the small intestine – for absorption – microvilli on surface of cells

26. Pseudostratified Columnar • A single layer of tightly packed columnar cells that appear to be multi-layered • Location: • Ciliated- Lines respiratory tract • Non-ciliated- Male urethra • Function: • Ciliated- moves materials across the apical surface of a tissue. • Non-ciliated- Absorb and protect

28. Stratified Squamous • Multiple layers of tightly packed squamous epithelial cells. • Location: • Areas that are subject to much “wear and tear”. • Upper layers are designed to be shed and replaced. • Function: • Protection

30. Stratified Cuboidal • Two layers of cube shaped epithelial cells • Rare • Location: • Lining the ducts of glands found in the esophagus • Function: • Moderate protection from the stomach acid that refluxes

32. Stratified Columnar • Multiple layers of columnar epithelial cells • Rare • Only the layer closest to the lumen (opening in a duct) is columnar in shape. The outer layers are somewhat squashed. • Location: • Lining the ducts of glands lining the esophagus • Function: • Moderate protection from stomach acid that refluxes

34. Transitional • Epithelial tissue that has a variable shape • Can stretch and relax multiple times without being damaged • Location: • Lines the urinary bladder • Function: • Protection

36. Let’s Practice For the following, indicate the type of epithelial tissue and where you would find it.

48. Bio 111-73

49. Bio 111-73