Epithelial Tissues and Glands Flashcards
four basic/primary types of tissues
epithelial (epithelium), connective, muscular, nervous
two main categories of epithelial tissue
- covering or lining epithelium
2. glandular epithelium
functions of epithelial tissue
- Secretion 2. Absorption 3. Filtration 4. Excretion 5. Transport 6. Protection
special category of epithelium
transitional epithelium (urothelium)
naming epithelial tissue
surface specialization + number of cell layers + cell morphology + tissue
two types of stratified squamous epithelium
Nonkeratinized Stratified Squamous Epithelium
Keratinized Stratified Squamous Epithelium
characteristics of epithelial tissue:
- cellularity
- specialized contacts
- polarity
- supported by connective tissue- lamina propria
- avascular, but innervated
- regeneration
polarity of epithelial tissue
- free or apical surface/pole/domain
- lateral surface/domain
- basal surface/pole/domain
for defining the subclasses of epithelium, look at the _____
morphology
number of cell layers:
- simple
- stratified
- pseudostratified
cell height/shape variation
- squamous
- cuboidal
- columnar
sometimes another name can be added based on specializations at the ____ surface of the cell (ex _____) or at the _____ surface of the tissue (ex ______)
apical; ciliated; apical; keratinized
steps to naming epithelial tissue
- the number of cell layers (simple, stratified, pseudostratified)
- the cell morphology at the surface (squamous, cubiodal, columnar)
- additional details (ciliated or nonciliated; keratinized or nonkeratinized)
single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia
simple squamous epithelium
function of simple squamous epithelium
allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae
location of simple squamous epithelium
kidney glomeruli (Bowman's capsule); air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae); inner surface of tympanic membrane (eardrum) Forms epithelial layer of serous membranes, such as the peritoneum
simple squamous epithelium is present in the ______ of the peritoneum
mesothelial lining
simple squamous epithelium of the endothelium is present in:
arterioles and venules in the dermis
single layer of cube-like cells with large, spherical central nuclei
simple cuboidal epithelium
function of simple cuboidal epithelium
secretion and absorption
location of simple cuboidal epithelium
kidney tubules; ducts and secretory portions of small glands, such as in thyroid gland and pancreas; ovary surface; anterior surface of capsule of lens of eye, posterior surface of eye
single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells)
simple columnar epithelium
function of simple columnar epithelium
absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action
location of simple columnar epithelium
nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus
nonciliated simple columnar epithelium
single layer of nonciliated column-like cells with nuclei near base of cells; contains goblet cells and cells with microvilli in some locations
location of nonciliated simple columnar epithelium
lines the gastrointestinal tract (from stomach to anus), ducts of many glands, and gallbladder
function of nonciliated simple columnar epithelium
secretion and absorption
ciliated simple columnar epithelium
single layer of ciliated column-like cells with nuclei near base; contains goblet cells in some locations
location of ciliated simple columnar epithelium
lines a few portions of the upper respiratory tract, uterine (fallopian) tubes, uterus, some paranasal sinuses, central canal of spinal cord, and ventricles of the brain
function of ciliated simple columnar epithelium
moves mucus and other substances by ciliary action
stratified squamous epithelium
thick membrane composed of several cell layers; basal cells are cuboidally or columnar and metabolically active; surface cells are flattened (or squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers
function of stratified squamous epithelium
protects underlying tissues in areas subjected to abrasion
location of stratified squamous epithelium
nonkeratinized type forms the moist linings of the esophagus, mouth and vagina, part of epiglottis and pharynx, and covers the tongue; keratinized variety forms the epidermis of the skin, a dry membrane
two types of stratified squamous epithelium
keratinized and nonkeratinized
stratified cuboidal epithelium
two or more layers of cells in which the cells in the apical layer are cube-shaped
location of stratified cuboidal epithelium
ducts of adult sweat glands and esophageal glands and part of male urethra
function of stratified cuboidal epithelium
protection and limited secretion and absorption
stratified columnar epithelium
several layers of irregularly shaped cells; only the apical layer has columnar cells
location of stratified columnar epithelium
lines part of urethra, large excretory ducts of some glands, such as esophageal glands, small areas in anal mucous membrane, and part of the conjunctiva of the eye
function of stratified columnar epithelium
protection and secretion
pseudostratified columnar epithelium
single layer of cells of differing heights, some not reaching the free surface (all cells are attached to the basement membrane); nuclei seen at different levels; may contain goblet cells and bear cilia
function of pseudostratified columnar epithelium
secretion, particularly of mucus; propulsion of mucus by ciliary action
location of pseudostratified columnar epithelium
nonciliated type in male’s sperm-carrying ducts (epididymis and urethra) and ducts of large glands; ciliated variety lines the trachea and most of the upper respiratory tract
transitional epithelium
resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells surface cells dome shaped or squamous like, depending on degree of organ stretch
function of transitional epithelium
stretches readily and permits distension of urinary organ by contained urine
epithelial cells exhibit distinct polarity:
- apical domain
- lateral domain
- basal domain
Apical domain specializations: microvilli are ….
cytoplasmic extensions / processes with core of actin filaments
average height and width of microvilli
1 micrometer and 0.08 micrometer
microvilli create a _____ in the intestinal epithelium or a _____ in kidney tubule cells
striated border; brush border
function of microvilli
increase surface area
stereocilia are…
considered long microvilli
function of stereocilia
increase surface area
produce movement, rapid back and forth
cilia
length and diameter of cilia
5-10 micrometers, 0.2 micrometers
cilia contain an _____
axoneme (microtubules in 9+2 arrangement)
the microtubules of cilia insert into the ____
basal bodies
lateral domain specifications: in light microscopy, we see _____ at the apicolateral margin of the cells; with EM, the ____ has been shown to be a _____
terminal bars; terminal bar; junctional complex
components of the junctional complex:
- zonula occludens or tight junctions
- zonula adherens
- macula adherens or desmosomes
zonula occludens (aka tight junction)
- type of occluding junction
- found closest to apical surface
- transmembrane proteins (occludins and claudins) fuse outer surfaces of adjacent membranes together sealing off the intercellular space
- forms a continuous band around cell which is impermeable, thus it limits the movement of substances between luminal space and tissue compartments via the intercellular space
- diffusion barrier between cells
- prevents integral membrane proteins movement between domains
- provide only limited resistance to mechanical stresses
the zonula occludens gives the ____ characteristic to epithelial tissue; for items to get across now they must be _____ via the specialized membrane proteins of epithelial cells
“barrier;” actively transported
zonula adherens
- a type of anchoring junction
- provides mechanical stability by linking the cytoskeleton of one cell to the cytoskeleton of the next; great for resisting separation
- forms continuous band around cell
process of connecting one cell to the next
microfilaments (actin) of the first cell attach to a plaque on the inside of its plasma membrane; this plaque is attached to transmembrane protein (cadherin) which crosses the plasma membrane of the first cell and attaches to the cadherin of an adjacent cell; this second cell’s cadherin crosses its plasma membrane where it attaches to a plaque just on the inside of the plasma membrane; this plaque is attached to the microfilaments (actin) of the second cell; thus connecting cytoskeleton of one cell to the next.
macula adherens (aka desmosome)
- a type of anchoring junction
- provides mechanical stability by linking cytoskeleton of one cell to the next; great for resisting separation
- forms spot welds; not continuous around cell; localized
process of macula adherens connecting one cytoskeleton to the next
intermediate filaments of the first cell attach to a plaque on the inside of its plasma membrane; this plaque is attached to transmembrane protein (cadherin) which crosses the plasma membrane of the first cell and attaches to the cadherin of an adjacent cell; this second cell’s cadherin crosses its plasma membrane where it attaches to a plaque just on the inside of the plasma membrane; this plaque is attached to the intermediate filaments of the second cell; thus connecting cytoskeleton of one cell to the next.
gap junctions
- communicating junctions
- transmembrane proteins are in the form of a protein tunnel called a connexon
- allows communication between cells; this is important in tissues where the activity of the cells needs to be coordinated
how gap junctions allow communication
-the connexon of one cell lines up with the connexon of of the next cell allowing the cells to exchange ions and small molecules; these items can diffuse from the cytosol of one cell to the cytosol of the next
the basement membrane is associated with ____ microscopy
light
the basal lamina is associated with _____
electron microscopy
2 components of basal lamina
- lamina lucida
2. lamina densa
type of occluding junction found closest to the apical surface
zonula occludens
type of junction in which transmembrane proteins (occludins and claudins) fuse outer surfaces of adjacent membranes together sealing off the intracellular space
zonula occludens
type of anchoring junction that provides mechanical stability by linking cytoskeleton of one cell to cytoskeleton of the next ; involves microfilaments (actin)
zonula adherens
type of anchoring junction that provides mechanical stability by linking the cytoskeleton of one cell to the cytoskeleton of the next ; involves intermediate filaments
macula adherens (desmosome)
type of communicating junction ; transmembrane proteins in the form of a protein tunnel called a connexon
gap junctions
type of anchoring junction that links the cell to the basal lamina ; specifically, it anchors microfilaments (actin) of the cytoskeleton of a cell to the basal lamina
focal adhesion
in focal adhesions, actin filaments are attached to extracellular matrix _____ (ex. laminin and fibronectin) in the basal lamina via _____ (the transmembrane protein used here)
glycoproteins; integrins
focal adhesions have functional role in _____ and transmitting signals from the extracellular environment to the interior of the cell (mechanosensitivity)
signal detection
a type of anchoring junction that links the cell to the basal lamina ; specifically anchoring intermediate filaments of the cytoskeleton to the basal lamina
hemidesmosome
in hemidesmosomes, intermediate filaments are attached to _____ and _____ in the basal lamina via integrins (the transmembrane protein used here)
laminin; type IV collagen
hemidesmosomes are found in epithelia subject to ____ and _____; useful for keeping the epithelium from separating from the underlying connective tissue
abrasion; mechanical shearing forces
two main categories of epithelial tissue
- covering or lining epithelium
2. glandular epithelium
proliferation of epithelial cells and their downgrowth into the subjacent connective tissue leads to _____
glandular epithelium
glands can be classified by their connection to ____ (where they secrete their secretion)
surface
2 types of glands
endocrine and exocrine
endocrine glands are ____ glands that secrete into _____
ductless; interstitial fluid
exocrine glands secrete their products onto a surface either ____ or via an _____
directly; epithelial duct
endocrine glands secrete ____ which can be classified as:
hormones:
- circulatory hormones
- paracrine hormones
- autocrine hormones
exocrine glands include ____, ___, and ____ ducts of the skin; digestive glands such as ____ glands, which secrete into mouth cavity, and _____, which secretes into the small intestine
sweat; oil; earwax; salivary; pancreas
exocrine glands can be classified based on:
- cellularity
- structure/morphology
- type of secretion
- mode/mechanism of secretion
exocrine glands can be classified based on the number of ____ that compose the gland (i.e. cellularity)
cells
cellularity of exocrine glands
unicellular and multicellular
type of unicellular exocrine gland in the intestinal epithelium that produce and secrete mucin, also found in the epithelial lining of the respiratory tract
goblet cells
classification of the structure of the duct of an exocrine gland
- simple- unbranched
2. compound- two or more branches
classification of the structure of the secretory units of an exocrine gland
- tubular- tube shaped; either short or long or coiled
- alveolar or acinar - round or globular
- tubuloalveolar and tubuloacinar - combination
exocrine glands can also be classified based on the type of secretion:
- mucous glands
- serous glands
- mixed glands
polarized, protein-secreting cells that typically produce digestive enzymes and other proteins
serous cells
produce hydrophilic glycoprotein mucins; cuboidal or columnar in shape
mucous cells
two major types of secretory cells associated with glands
serous cells and mucous cells
cells found in the basal lamina of secretory units and the initial part of duct system
myoepithelial cells
the basic unit of a salivary gland (i.e. salivon) is composed of the ____ and all related ducts
acinus
a blind sac composed of secretory cells and is the secretory portion
acinus
3 secretory acini are found in salivary glands:
- serous acini
- mucous acini
- mixed acini
serous acini
serous cells only; generally spherically shaped
mucous acini
mucous cells only; generally tubular shaped
mixed acini
contain both serous and mucous cells
in traditional fixation methods, it appears the mucous acini have a cap of ____ cells; these caps are called _____, found in the ____ and _____ glands
serous; serous demilunes; sublingual; submandibular
exocrine glands can be classified based on the mode of secretion:
- merocrine glands
- holocrine glands
- apocrine glands
serous cells are ____ in shape; ___ on basal lamina and _____ apical surface facing lumen
pyramidal; broad base; narrow
serous cells contain secretory granules called _____- spherical in shape, found in apical cytoplasm
zymogen granules
serous cells have ____ cytoplasm due to RER and free ribosomes
basophilic
in serous cells, nuclei are _____
rounded
