Epithelial Tissue Flashcards
Epithelial tissue has two forms:
- covering and lining epithelium
2. glandular
ET covers
walls/organs of the closed ventral body cavity
ET lines
cavities
ET lining/covering examples:
digestive, urogenital, respiratory
ET glandular tissue:
fashions the glands of the body
What are the functions of the ET boundary (6)?
- protection
- absorption
- filtration
- excretion
- secretion
- sensory receptor
What are the special characteristics of Epithelium (5)?
- polarity
- specialized contacts
- supported by connective tissue
- avascular but innervated
- regeneration
Classification– What does the first and second name indicate about the ET layer?
first name indicates the number of cell layers
second layer describes the shape of the cell
What are the two first names for ET?
either simple (single layer) or stratified (multiple layers)
Function of simple ET?
the thin layer is mostly for secretion, filtration, and absorption
Function of stratified ET (provide example)?
common in areas of high abrasion where protection is needed
ex: skin surface and lining of mouth
Squamous ET description:
flattened and scale like
Simple squamous ET has what two coverings?
an inner covering: endothelium
a mid covering: mesothelium
Purpose of ET endothelium:
the inner covering provides a slick, friction-reducing lining
ex: blood vessels and heart
What is the purpose of ET mesothelium (provide where it is most commonly found)?
the mid covering lines ventral body and covers organs
ex: found in serous membranes
Simple cuboidal description:
the cells are box like and are as tall as they are wide
Function of simple cuboidal (provide example):
secretion and absorption
ex: kidney tubules, wall of small glands, and ovary surface
Simple columnar description:
the cells are a tall layer that is closely packed
Function of simple columnar:
absorption and secretion (mainly of enzymes and mucus)
Where can you find simple columnar (both nonciliated and ciliated)?
NONCILIATED: digestive tract, gallbladder, glands
CILIATED: small bronchi, uterine tubes, some regions of the uterus
What is a pseudostratified columnar layer?
they vary in height, giving the impression of multiple layers
ex: trachea
How do you classify stratified layers?
distinguish the top layer aka the apical layer
The top of the layer is called the apical layer, the bottom layer is known as
the basal layer that holds basement cells
Dead cells are at which point of the stratified layer?
the apical layer
Newly regenerated cells are found…
at the basal layer
Stratified squamous description:
the free surfaces (apical layer) is squamous, while the remaining layers are cuboidal or columnar
Where can stratified squamous layers be found?
places subjected to wear and tear
Where can stratified cuboidal layers be found?
RARE– found in mostly ducts or large glands (mammary glands and sweat glands)
Where can columnar stratified be found?
LIMITED– found at transition areas or junctions between two other types of epithelia
ex: pharynx, male urethra, lining of glands
Stratified columnar description:
the free surface (apical layer) is columnar, they remaining layers are cuboidal
Transitional epithelium description:
apical cells are dome-shaped or squamous like, resembles stratified squamous or stratified cuboidal; basal cells are cuboidal or columnar
cells overlap for the purpose of stretching
Function of transitional epithelium:
for areas that need to readily stretch
ex: urinary organs (uterus, bladder, urethra)
Gland consists of one of more cells that…
make and secrete a particular product
Secretion description:
an aqueous fluid that contains proteins
* can also be lipid/steroid rich
Secretion definition:
an active process where glandular cells obtain substances from the blood and chemically transform and discharge the product
Glands are either internal or external also known as…
endocrine and exocrine respectively
How are glands classified (2)?
- whether internal/external
2. number of cells– multicellular or unicellular
Where are unicellular glands?
scattered within epithelial sheets
How are multicellular glands formed?
invagination: inward growth of epithelial sheet into underlying connective tissue
Endocrine glands are ductless and produce…
hormones
Exocrine glands […] products onto […] or into […].
secrete; body surfaces (skin); cavities
Unicellular exocrine glands secrete
directly
How do multicellular exocrine glands secrete?
via epithelium– walled duct
What are two types of unicellular exocrine glands? What is the one thing they ALL produce?
- mucous
- goblet cells
produce mucin
What is the mucin produced by mucous and goblet cells?
a complex glycoprotein that dissolves H2O when secreted
this forms mucous
Where can mucous and goblet cells be found?
along epithelial linings of intestinal and respiratory
What two parts make up the multicellular exocrine glands?
- duct
2. secretory unit (acinus)
What is a secretory unit?
secretes substance
Multicellular glands can be classified as either simple or compound. What’s the difference?
simple– unbranched duct
compound– branched duct
What are the 3 modes of secretion?
- merocrine
- holocrine
- apocrine
Pancreas, sweat glands, and salivary glands are what type of glands? What is their mode of secretion?
multicellular exocrine glands
merocrine
Oil glands are what type of glands? What is their mode of secretion?
multicellular exocrine glands
holocrine
Describe merocrine:
they secrete by exocytosis as they are produced
“merely secrete”
Describe holocrine:
accumulate products till they rupture
“die for their cause”
Describe apocrine:
ANIMALS ONLY: accumulate till filled; apical surface pinches off
