Epithelial Tissue

Objectives: 1. identify all types of epithelia. 2. state the functions and locations of the following types of epithelium: lining epithelium (simple, stratified, pseudostratified, and transitional) and glandular epithelium (exocrine glands). 3. define terminal bar and terminal web. 4. identify and state the functions of kinocilia, sterocilia, and microvilli. 5. state the names and locations of cell junctions

What is tissue made up of?

cells (living component) and extracellular matrix (fluid and fibers/non-living component)

What are four major categories of tissue in the body?

Epithelial, connective, muscle and nerve

What are the groups of tissues assembled into?

organ

What are organs organized into?

organ systems

What are systems organized into?

a body

What are the four characteristics of epithelial tissue?

1. closely packed with very little intracellular substance in between cells 2. cells sit on a basement membrane 3. polarity in structure (apical-basal/basolateral) 4. avascular (no blood vessels in epithelium)

What is a basement membrane?

platform for epithelial cells to sit on (multilayer membrane with collagen)

If there is no blood vessels in the epithelium, where does it get its nutrients?

diffusion from blood vessels in the connective tissue below

What is the benefit of it being avascular?

It is the first line of defense and pathogens don’t get direct access to vascular system

What does the basement membrane protect the epithelial cells from?

carcinoma metastasis (type of cancer that starts in epithelial cells)

Does epithelial cells have fast or slow turnover?

fast turnover rate (undergoing apoptosis)

What epithelium lining turns over as fast as every five to ten minutes?

GI tract

What are the two classifications of epithelial tissue?

lining epithelium and glandular epithelium

What is lining epithelium?

sheet of cells covering a surface (external or internal)

Which epithelial tissue has a basement membrane?

lining epithelium

What is glandular epithelium?

invagination (cavity or pocket) from surface

What are the 6 functions of epithelium?

1. protection 2. secretion 3. absorption 4. transport of material on the epithelial surface (cilia) and transcellular transport across epithelium (diffusion and vesicle-mediated) 5. selective permeability 6. sensory cells in taste buds, retina, and hair cells in ear

What ways does epithelial lining and glandular do absorption?

endocytosis or pinocytosis

What does epithelial cells secrete?

mucus, enzymes, hormones

What is the classification and nomenclature of lining epithelial membrane?

number of layers and shape of the superficial cells

What is the classification based on the number of layers?

Simple (one layer) and stratified (multiple layers)

What is the classification based on the shape of the superficial cells?

squamous, cuboidal, columnar

What cells are flat?

squamous

What cells are cube shaped?

cuboidal

What cells are column shaped?

columnar

What are the two types of epithelium?

pseudostratified and transitional epithelium

Simple epithelia

single layer of cells (all cells contact the basement membrane and all cells reach the free surface)

What is simple squamous epithelium?

one layer of squamous cells on basement membrane

What is the special case of simple epithelia in that all cells touch the basement membrane, but not all reach the free surface?

pseudostratified

Stratified Epithelia

only the basal layer of cells touch the basement membrane, not all cells reach the free surface

Transitional Epithelia

type of stratified epithelia where the surface cells can change between squamous and cuboidal

Why do we see the transitional epithelia relaxed and distended?

line the bladder (squamous/squished when bladder is full)

What are the simple squamous epithelium involved in?

passive transport (diffusion) of gases or fluids

What is the shape of the squamous cell’s nuclei?

flat

What are examples of where we see simple squamous epithelium?

lungs or walls of blood vessels

Does the simple squamous epithelium perform one or many roles?

many roles

What is the nucleus shape of simple cuboidal epithelium?

round and centered

Where is simple cuboidal epithelium?

lining of small ducts and tubules (ducts of salivary glands and pancreas, collecting tubules of kidney)

What is the function of the simple cuboidal epithelium?

excretory, secretory, or absorptive

What is the difference between the nucleus in the simple cuboidal vs simple columnar epithelium?

cuboidal are centered and columnar are at the bottom

What is the description of the nuclei in simple columnar epithelium?

elongated and perpendicular to the basement membrane

Where are simple columnar epithelium found?

on absorptive surfaces such as small intestine (with microvilli)

What can simple columnar epithelium have?

microvilli or cilia

What is a goblet cell?

unicellular gland that produces mucus

Where are goblet cells?

in simple columnar epithelium (usually GI tract)

What makes up cilia cells?

microtubules

What is non-ciliated columnar cells, with secretory functions called when present in the fallopian tube?

peg cells

How many cilia can be on one cell?

300

How many layers in stratified epithelium?

2 or more

What is the main function of stratified epithelium?

protection

What are the two types of stratified squamous?

non-keratinizing or keratinizing

What does the non-keratinized stratified squamous do?

strongest protection against abrasion (not to dryness)

What is another name for non-keratinized stratified squamous?

mucus membrane (has mucus producing glands)

Where would you find non-keratinized stratified squamous?

oral cavity, pharynx, esophagus, anal canal, cervix, and vagina

What is the number of layers for non-keratinized stratified squamous?

Variable. Superficial (squamous), intermediate (polygonal), basal (cuboidal)

What is the only type of keratinized stratified squamous epithelium?

epidermis and tongue

What is the process of accumulating cytokeratin called?

keratinisation

What is the benefit of keratinized stratified squamous epithelium?

waterproof and protect against dryness

Where would you find stratified cuboidal epithelium?

lining the duct of sweat gland in skin

How many layers in stratified cuboidal epithelium?

2 layers of cuboidal epithelium

What is stratified columnar epithelium?

thin, stratified epithelium with only two or three layers of cuboidal (bottom) and one layer columnar (top)

Where would you find stratified columnar epithelium?

lining the large excretory ducts of exocrine glands, such as the salivary glands

What is the function of stratified columnar epithelium?

provide lining of the duct (no absorptive/secretory function)

What is the layers for pseudostratified (columnar) epithelium?

appears multilayers, but is truly 1 layer

Are the cells the same or different height in pseudostratified (columnar) epithelium?

different

What makes pseudostratified epithelium look multilayered?

different height

Where is pseudostratified (columnar) epithelium found?

respiratory tract

What can pseudostratified (columnar) epithelium also have?

kinocilia and goblet cells

What is kinocilia?

motile/movement of contents

What do goblet cells do in pseudostratified (columnar) epithelium?

produce mucus and purify air

What cells are affected by smoking and cause the need to cough up mucus?

Goblet cells in pseudostratified (columnar) epithelium

What is different with pseudostratified (columnar) epithelium with stereocilia?

no basal bodies and non-motile

What does stereocilia do?

absorption only

Where are stereocilia found?

epididymal duct (male reproductive tract) or the inner ear

What do stereocilia do in the male reproductive tract?

absorb water to make semen more concentrated

What is special about the transitional epithelium?

cells at the surface transition between cuboidal and squamous

Where is transitional epithelium found?

urinary system, urothelium (proximal one third of the urethra and urinary bladder)

What are transitional epithelium also called?

umbrella or dome cells

What are all the names of epithelium lining?

Simple squamous, cuboidal, and columnar. Stratified squamous, cuboidal, columnar. Pseudostratified columnar. Transitional epithelium

What structures are present at the surface of epithelial cell’s plasma membrane

apical, lateral, and basal

Is apical surface top or bottom of cell?

top

Is basal top or bottom of cell?

bottom

What is another name for apical surface?

luminal

What are three types of apical surfaces?

microvilli, kinocilia, and stereocilia

What are kinocilia?

true cilia made of mircotubules

What are sterocilia?

not true cilia, not made of microtubules, actually longer versions of microvilli

What are microvilli?

finger-like projections extended toward the lumen. outward folding of membrane

What is the function of microvilli?

increase the surface area for the purpose of better and faster absorption

What does microvilli in small intestine form?

brush border

Microfilaments hold up microvilli. What are they called?

actin

What are the functions of the mircofilaments?

maintain stability, perform contraction and elongation

What makes up the terminal web?

actin filaments

What do actin filaments insert on?

Terminal web

What is the function of terminal web?

provide anchor and base

What are the motile structures with project from the apical surfaces of some epithelial cells?

kinocilia

Where is kinocilia found?

respiratory and female reproductive tracts

Is kinocilia built fast or slow?

slow (takes a lot of energy)

Which is longer: cilia or microvilli?

cilia

What protein do cilia have that allows them to move?

Dynein (ATPase)

What is the function of Dynein?

allows kinocilia to bend