Epithelium Characteristics cont. 2. Apical Surface

Transcription

1 Epithelium Characteristics cont. 2. Apical Surface always has one exposed (apical) surface Some surfaces are smooth & slick, others may have: microvilli fingerlike extensions of the plasma membrane; increase surface area to absorb & secrete substances (intestine & kidney) cilia hairlike projections commonly found in internal tracts; propel substances along the epithelial surface

2 Epithelium Characteristics cont. 3. Basement membrane cells rest on thin supporting basal lamina which separates it from connective tissue Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings: adapted by K. roy Slide 3.43

3 Epithelium Characteristics cont. 4. Avascularity (have no blood supply) well supplied with nerve fibers, but has no blood vessels all cells receive nutrients by diffusion from underlying connective tissue Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings: adapted by K. roy Slide 3.43

4 Epithelium Characteristics cont. 5. Regeneration High capacity to regenerate As long as the cells receive adequate nutrition, they can replace lost cells rapidly by cell division Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings: adapted by K. roy Slide 3.43

5 Classification of Epithelium The types of epithelia are identified by shape of cells arrangement of cells (number of cell layers present) Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 3.44a

6 Epithelium Classification

7 Classification of Epithelium By height, there are 3 common shapes Squamous flattened & scalelike Cuboidal cube-shaped (as tall as they are wide) Columnar column-like (tall & column shaped) *The shape of the nucleus conforms to that of the cell and can help distinguish epithelial types

8 Classification of Epithelium Cell arrangement (# of cell layers) 2 major types of epithelium 1. Simple one layer; typically found where absorption & filtration occur 2. Stratified more than one layer; found in high abrasion areas where protection is important (skin surface & lining of mouth)

9 Classification of Epithelium 4 major classes of simple epithelial tissue 1. simple squamous 2. simple cuboidal 3. simple columnar (may or may not contain cilia) 4. pseudostratified columnar (may or may not contain cilia)

10 Classification of Epithelium 4 major classes of stratified epithelial tissue 1. stratified squamous 2. stratified cuboidal 3. stratified columnar 4. transitional epithelium FYI classification of epithelia by cell type and arrangement reveals nothing about the tissue s body location

11 Simple Epithelium Simple Squamous Functions Filtration, Diffusion Lines lungs and capillaries

12 Simple Squamous Epithelium Serous membranes, O 2 and CO 2 Diffusion

13 Simple Squamous Epithelium

14 Simple Epithelium Simple Cuboidal Functions Common in glands and their ducts Found in salivary glands, kidney tubules, ovaries

15 Simple Cuboidal Epithelium One layer of cuboidal cells resting on a basement membrane

16 SIMPLE CUBOIDAL Epithelium

17 Simple Cuboidal Epithelium

18 Simple Epithelium Simple columnar Functions May includes goblet cells, which produce mucous Lines digestive tract

19 Simple Columnar Epithelium Goblet cells produce a lubricating mucus.

20 Simple Ciliated Columnar Epithelium

21 Simple Epithelium Pseudostratified Single layer, but some cells are shorter than others Absorption or Secretion Sometimes ciliated, such as in the respiratory tract

22 Pseudostratified Ciliated Epithethium Respiratory Tract; nuclei appear at different heights

23 Stratified Epithelium Stratified Squamous Cells at the free edge are flattened Protective covering where friction is common Locations Skin Mouth Esophagus Figure 3.17e Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 3.49

24 Stratified Squamous Epithelium Abuse/Friction, esophagus, mouth, outer skin

25 Stratified Squamous Epithelium

26 Stratified Squamous Epithelium

27 Stratified Epithelium Stratified cuboidal Two layers of cuboidal cells Stratified columnar Surface cells are columnar, cells underneath vary in size and shape Both: Rare in human body Found mainly in ducts of large glands function in protection Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 3.50

28 Stratified Cuboidal Epithelium Usually found with 2 layers being cuboidal Ducts of glands

29 Stratified Cuboidal Epithelium

30 Stratified Cuboidal Epithelium

31 Stratified Columnar Epithelium Ducts of large glands, basal cells vary in size. RARE

32 Stratified Epithelium Transitional epithelium Shape of cells depends upon the amount of stretching Lines organs of the urinary system Figure 3.17f Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 3.51

33 Transitional Epithelium Highly modified, urinary bladder, ureters,

34 Transitional Epithelium