1. Epithelial Tissues

2. Tissues – Introduction
a group of similar cells specialized to carry on a particular function
tissue = cells + extracellular matrix
nonliving portion of a tissue that supports cells
4 types
epithelial = protection, secretion, absorption
connective = support soft body parts and bind structures together
muscle = movement
nervous = conducts impulses used to help control and coordinate body activities

3. Epithelial Tissues Characteristics
free surface open to the outside or an open internal space
basement membrane anchors epithelium to underlying connective tissue
lack blood vessels
readily divide (ex. skin healing)
tightly packed with little extracellular space

4. Epithelial Classifications
classified based on shape and # of cell layers
shape
squamous = thin, flat cells
cuboidal = cube-shaped cells
columnar = tall, elongated cells
number
simple = single layer
stratified = 2 or more layers

5. Epithelial Locations
cover body surfaces, cover and line internal organs, and compose glands
skin cells, cells that line the stomach and small intestine, inside of your mouth

6. Simple squamous epithelium
a single layer of thin, flattened cells
look like a fried egg
easily damaged
common at sites of filtration, diffusion, osmosis; cover surfaces
air sacs of the lungs, walls of capillaries, linings of blood and lymph vessels

8. Simple cuboidal epithelium
single layer of cube-shaped cells
centrally located nucleus
secretion and absorption
surface of ovaries, linings of kidney tubules, and linings of ducts of certain glands

10. Simple columnar epithelium
single layer of cells that are longer than they are wide
nucleus located near basement mem.
ciliated or nonciliated
some have microvilli
goblet cells = secrete mucus
absorption, secretion, protection
linings of the uterus, stomach, and intestine

12. Pseudostratified columnar epithelium
appear stratified b/c nuclei are at 2 or more levels
NOT stratified b/c all cells touch basement mem.
ciliated
goblet cells
protection, secretion, movement of mucus
linings of respiratory system

14. Stratified squamous epithelium
many layers of flattened cells
named based on appearance of top layer of cells
protection
outer layers of skin, linings of oral cavity, throat, vagina, and anal canal

16. Stratified cuboidal epithelium
2 or 3 layers of cuboidal cells
protection
linings of larger ducts of mammary glands, sweat glands, salivary glands, and pancreas

18. Stratified columnar epithelium
protection and secretion
vas deferens, part of the male urethra, parts of the pharynx (throat)

20. Transitional epithelium
can stretch
distensibility (stretching), protection
inner lining of urinary bladder and linings of the ureters and part of urethra

22. Glandular epithelium
cells that are specialized to produce and secrete substances into ducts or into body fluids
gland = 1 or more cuboidal or columnar cell
secretion
salivary glands, sweat glands, endocrine glands

24. Exocrine vs. Endocrine
exocrine = secrete sub. into ducts that open onto surfaces
skin or linings of digestive tract
endocrine = secrete sub. into tissue fluid or blood
hormones

25. Exocrine glands
merocrine = release watery, protein-rich fluid by exocytosis
salivary glands, sweat glands
apocrine = lose small portions of their cell body during secretion
mammary glands, ear wax
holocrine = entire cell lysis (breaks apart) during secretion
sebaceous glands of the skin

27. Serous vs. Mucous serous = typically watery with lots of enzymes
lubrication
mucous = mucus
digestive and respiratory systems
protection