1. Epithelial Tissue
Department of Biology, WCU

2. Introduction Unicellular versus multicellular Tissue definition
Tissue types
epithelial (skin, villi)
connective (between muscles)
muscle (skeletal, smooth, cardiac)
nervous (CNS, PNS)
Histology

3. Epithelium 1. Covering and lining 2. Glandular
skin, pericardium, digestive tract
2. Glandular
Mucus, oil, sweat, goblet cells
Epithelium forms boundaries
Internal, external

4. Functions of epithelium
Protection
Absorption
Filtration
Excretion
Secretion
Sensory reception

5. Characteristics of epithelium
Cellularity
Simple, stratified
Cell contacts
Tight junction, desmosome, gap junction
Polarity
Microvilli, flat, rounded

6. Characteristics of epithelium
Innervated but avascular
Nutrients and O2 diffuse from blood vessels
Regeneration
Abrasion (lower GI, skin)

7. Classification of epithelium
1. Number of cells in layer

8. Classification of epithelium
2. Shape
squamous
cuboidal
columnar
transitional

9. Simple epithelium Simple squamous diffusion, filtration
e.g. lungs, glomerulus of kidney

10. Simple epithelium
Simple cuboidal
Secretion and absorption
e.g. kidney

11. Simple epithelium Simple columnar Secretion and absorption
e.g. GI tract

12. Simple epithelium Pseudostratified columnar Secretion and absorption
One layer
Ciliated (trachea)

13. Stratified epithelium
Stratified squamous
most abundant
named after cells on surface
lining skin, mouth, esophagus

14. Stratified epithelium
Stratified cuboidal
ducts of glands

15. Stratified epithelium
Stratified columnar
Male urethra, some gland ducts

16. Stratified epithelium
Transitional epithelium
Basal cells cuboidal/columnar, apical cells distendable

17. Surface modifications
1. Microvilli
Increase surface area (intestine, kidney brush border)

18. Surface modifications
2. Cilia
Longer than microvilli
Unidirectional particle movement (trachea)

19. Glandular epithelium Cell or group of secreting cells
Covering and lining epithelium
Secretion
water based, contains protein
Types
exocrine, endocrine

20. Exocrine glands Numerous e.g. surface - sweat, cavity - intestine
Types
unicellular: goblet cell

21. Exocrine glands Types Multicellular Duct and secretory unit
Simple- unbranched
Compound - branched

22. Exocrine glands

23. Exocrine glands Modes of secretion Merocrine (exocytosis)
Holocrine (rupturing)

24. Glands 3. Apocrine - apex of cell pinching Endocrine glands
mammary gland
Endocrine glands
ductless
secretions enter blood stream
pancreas (insulin and glucagon)