Lecture 1 Characteristics of Epithelial Tissues Flashcards
9 characteristics of Epithelial Tissues
Cells with relatively uniform geometric shape
Cells tightly bound together
Relatively little intercellular matrix
Cells exhibit polarity
Tissues do not contain blood vessels
Tissues sit on top of basal lamina
Tissues derived from -Ecto -Endo and Mesoderm
Line body cavities and cover body surfaces
Form secretory and excretory parts of glands
Where do epithelial tissues get blood?
Mostly from connective tissue, do not contain blood vessels
Epithelial Tissues derived from:
The 3 germ layers
- Ecto
- Endo
- Meso
Germ Layers
All tissue in adults come from the 3 layers
Ecto
Endo
Meso
Most come from ecto and endo. Some specialized from Meso.
Where are Epithelial Tissues?
Line body cavities and cover body surfaces
4 ways to classify epithelial
- number of cell layers (simple, stratified)
- shape (squamous, coboidal, columnar)
- according to surface modifications on apical domain
- keratinized or non-keratinized
Simple
Single cell layer
Stratified
2 or more cell layers
Squamous
flattened cells
Cuboidal
tall as they are long cells
Columnar
much taller than they are wide cells
Which cell layer do you look at when classifying it?
Only the top.
If top cells don’t have nucleus they are
keratinized
Keratinized stratified squamous example
Epidermis
Cilia
long, filamentous that move back and forth
Organized by basal bodies:
-formed by 9 microtubule triplets in a helicoid array
Stereocilia
Same as cilia but don’t move
3 surface modifications on apical domains of outermost cell layer
(way to classify)
- Cilia
- Stereocilia
- Microvilli (brush border)
Microvilli
surface modification on apical domains Short filamentous, forms brush border Core of Actin filaments Anchored to terminal web made of other Actin cells Cap controls how long they are
Kerratinized
Way to classify epithelial tissues
top cells do not have nucleus
Main function microvilli
Increase surface area and associated absorption.
Ex of where stereocillia occur
Epididymis
Pseudostratified
Type of simple
Single layer of cells, microscopically looks like two or more layers
Cells of varying height, all in contact with basement membrane
Transitional
Type of simple? (some consider to be stratified)
Epithelium that is designed to be stretches.
Lines urinary bladder, ureters.
2 parts of cell Polarity
- Apical domains
2. Basolateral domains
Apical domains
Characterized by surface modifications
Ex. cilia and microvilli
Basolateral domains
Characterized by intercellular junctions
In contact with basement membrane
Example of Simple Columnar cells
Intestinal cells
Type of cells in thyroid
Simple cuboidal
Goes from high to low depending on function
Non-keratinized
Or lightly keratinized
May show presence of nuclei in outermost layers of cell
Ex. esophagus and vagina
Basement membrane consists of
Basal lamina that contains Laminin either entactin and proteoglycans
Reticular lamina
Basal Lamina
Part of basement membrane
Produced by epithelium
Contains: Entactin and Proteoglycans
2 things Basal lamina contains
- Laminin
Entactin
Proteoglycans
Fibronectin
Made up of two protein chains cross-linked by disulfide bonds Has binding sites for: -Heparin -Integrins -Collagen -Fibrin
Fibronectin 4 binding sites
- Heparin
- Integrins
- Collagen
- Fibrin
Simple squamous examples
Lung air sacs
Bowman’s capsule
Endothelium
Mesothelium
Simple cuboidal examples
Surface of ovary Pigmented epithelium of retina Kidney tubules Glands and ducts Terminal bronchioles Choroid plexus of brain
Simple, non-ciliated columnar examples
Digestive tract from cardia of stomach
Excretory ducts of many glands
Gallbladder
Simple, ciliated columnar examples
A few portions of upper respiratory tract Uterine tubes Uterus Paranasal sinuses Central canal of the spine
Stratfifed squamous, non-keratinized or moderately keratinized examples
Lining of mouth Tongue Esophagus Part of epiglottis Vagina
Stratified squamous, highly keratinized
Epidermis
Stratified cuboidal examples
Seldom found
Stratified columnar examples
Seldom found
Stratified transitional examples
aka urothelium
Lining of bladder
Ureters
Superior urethra
Pseudostratified epithelium
Ciliated in respiratory system
Male reproductive system without cilia
Pseudostratified examples
Large excretory ducts of many large glands Male urethra Eustachian tube Upper respiratory tract Some ducts of male reproductive system