510-04 Epithelia Flashcards
Epithelia consists of one or more layers of closely adhering cells that form a flat sheet with an unattached ___ surface (exposed to environment or internal body cavity) and a ___ surface (attached to basement membrane).
free, basal
Do epithelia contain blood vessels?
no, epithelia are avascular
Because epithelia are avascular, through which process do they receive nutrients from capillaries in the underlying connective tissue or from a moist free surface?
diffusion
Are epithelia innervated?
yes
What kind of neurons innervate epithelia?
sensory neurons
What is the function of the basement membrane?
It anchors epithelium to underlying connective tissue (so that skin stays in place).
Is epithelium permeable/ semi-permeable/ non-permeable? If so, what is one type of cell that is is permeable to?
semi-permeable, white blood cells
Do epithelia cells on average have a longer or shorter lifespan than other cells? Why?
shorter, there are no blood vessels so they lack consistent nutrition
The basement membrane of the epithelia is composed of the ___ lamina and the ____ lamina.
basal, reticular
____ lamina is a complex mixture of proteins produced by the epithelial cells and underlying fibroblast?
basal lamina
What three proteins do basal epithelial cells contribute to the basal lamina?
laminin, entactin, type IV (4) collagen
What cells in the connective tissue under the epithelia contribute fibronectin and proteoglycans to the basal lamina?
fibroblasts
Fibroblasts in connective tissue under the epithelia contribute molecules including ____ and ___ to the basal lamina
fibronectin + proteoglycans
The ___ lamina is a layer of the basement membrane seen in some epithelia that attaches to underlying connective tissue.
reticular
What is the underlying connective tissue that the reticular lamina blends into?
lamina propria
Can the layers of the basal lamina be seen with a light microscope?
No, layers of the basal lamina can only be seen with an electron microscope
The basal lamina is composed of a thin, light staining ____ ____ and a darker staining ___ ___.
lamina lucida, lamina densa
(T/F) Lamina densa is light staining and lamina lucida is dark staining
false
____ is a glycoprotein secreted by epithelial cells that bind type IV collagen, heparin sulfate and integrins. This glycoprotein bridges the lamina lucida and lamina densa to the plasma membrane
laminin
Lamina densa is composed of _____ collagen and ____.
Type IV (4), proteoglycans
The ___ ___ is the structural attachment site for anchoring fibrils that extend to the reticular fibers in the connective tissue under the epithelium.
lamina densa
The basal lamina and reticular lamina are joined together by type __ and __ collagen fibrils that weave through loops of type ___ collagen anchoring fibrils
1, 3, 7
Hemidesmosome connect the basal lamina to the cytoskeletal ____.
tonofilaments
What are the functions of simple squamous epithelium?
- allows rapid diffusion of gases
- secretion of serous fluid
What kind of epithelial tissue lines the alveoli of the lungs, renal glomeruli, and the cardiovascular system?
simple squamous
Are simple cuboidal epithelium cells often found with microvilli?
yes
What are 3 functions of simple cuboidal epithelium?
1) absorption
2) secretion
3) conduction
What type of epithelium is found in the liver, thyroid, lung bronchioles, kidney tubules, mammary glands, salivary glands, and other glands?
simple cuboidal
What might the free surface of simple columnar epithelia posses?
microvilli or cilia
What are two functions of simple columnar epithelium?
1) absorption
2) secretion of mucus (goblet cells)
What kind of cells secrete mucus in simple columnar epithelium?
goblet cells
What kind of epithelium lines the intestines, uterus, and ducts of glands?
simple columnar
Pseudostratified epithelium has a mix of short ___ cells and taller ____ cells and ___ cells which creates a stratified appearance.
basal, goblet, ciliated
What does pseudostratified epithelium secrete and propel?
respiratory mucus
What kind of epithelium secretes and propels respiratory mucus?
pseudostratified
Which type of epithelium is found in the upper respiratory tract including the trachea and nasal cavities?
pseudostratified
What 3 parts do mucous mebranes consist of?
1) mucous-producing epithelium
2) lamina proria - underlying layer of vascular connective tissue
3) muscularis mucosae- thin layer of smooth muscle
What kind of tracts do mucous membranes line?
Tracts that open to the exterior: digestive, respiratory, urinary, and reproductive
Mucous is produced by ___ cells in the epithelium and by ____ ___ in the lamina propria
goblet, multicellular glands
Why are epithelia of the upper respiratory tract and parts of the reproductive tract ciliated?
to sweep mucous out of the body
Does a keratinized epithelium have a surface layer of alive or dead cells? Do these cells have nuclei?
dead, no
What is epithelium called with characteristics in between those of keratanized and nonkeratinized epithelium?
parakeritanized/ orthokeritanized
What kind of stratified epithelial cells are living, nucleated, and form an abrasion-resistant, moist, slippery layer?
nonkeratinized stratified squamous
Where can nonkeratinized stratified squamous be found in body?
oral mucosa, esophagus, vagina
What are 2 advantages of a keratinized layer of epithelium?
The keratin retards water loss and is a barrier to irritants and pathogens
Where is keratinized stratified squamous epithelium found in the body?
epidermis and some oral epithelia
In the uncommon stratified cuboidal and columnar epithelium, the basal cells are typically ____ with surface cells that are either ___ or ____.
cuboidal, cuboidal or columnar
Where may stratified cuboidal and columnar epithelium be found in the body? Are they common?
Can be found in the larger ducts of some glands including the pancreas, salivary glands and sweat glands. Not common type of epithelium
What is the purpose of the protective protein plaques that cover the domed surface cells of transitional epithelium?
protect cells from infection
protect cells through the mechanism of stretching (i.e when the bladder stretches to accommodate for larger volume of urine)
What type of epithelium is characterized by domes surface cells covered with protective plaque surfaces?
transitional epithelium
(T/F) Transitional epithelium is actually a pseudostratified epithelium
True
Where in body is transitional epithelium found?
urinary bladder
All cells, except ___ ___, are anchored to other cells or to the matrix surrounding them by intercellular junctions
blood cells
Which intercellular junction seals together neighboring cells in an epithelial sheet to prevent leakage between cells?
tight junction (zonula occludens)
Which intercellular junction joins actin bundles in one cell to actin bundles in an adjoining cell?
adhesive junctions (zonula adherens)
Which intercellular junction joins the intermediate filaments in one cell to those in an adjoining cell?
desmosome (macula adherens)
Which intercellular junction allows passage of small, water-soluble molecules from one cell into another?
gap junctions
Which intercellular junction anchors intermediate filaments in a cell to the basal lamina?
hemidesmosomes
What is the strongest intercellular junction?
desmosome
What kind of junction does “zonula” describe? “macula”?
zonula- junction that completely encircles cell (tight, adhesive)
macula- junctions in specific spots (desmosomes)
Tight junctions completely encircle the cell at the ___ end
apical
Tight junctions are composed of transmembrane adhesive proteins including ____, ___, and other cell-specific ____
claudin, occludin, JAMs (junctional adhesion molecules)
(T/F) In tight junctions, the transmembrane adhesive proteins of one cell bind to different proteins on the adjacent cell.
False, they bind to the same protein (i.e claudin binds with claudin)
Adhesive junctions are dependent on what ion?
Ca ++ (calcium
Desmosomes are abundant among cells of ___ and ____
muscle and skin
____ are strong attachments that hold cells together against mechanical stresses like shearing forces
Desmosomes
Desmosomes are composed of attachment plaques of structural proteins linked to intermediate filaments of the cytoskeleton, like ___, and to integral membrane proteins like ____.
keratin, cadherin
What are the cadherins in desmosomes?
desmoglein and desmocollin
What intracellular proteins in desmosomes form a dense plaque that anchors intermediate filaments?
plakoglobin, desmoplakin, and plakophilin
Where in the body are gap junctions abundant?
embryos, cardiac muscle, and smooth muscle
What protein controls gap junctions?
connexin
How many connexins make up a connexon?
6
Gap junctions are clusters of ___.
connexons
What kind of junction is formed when the connexons of two cells pair up?
gap junction
Glands are composed predominantly of ____ tissue
epithelial
What kind of glands possess ducts?
exocrine
Do endocrine glands have ducts? What are there products? How are they secreted?
- No
- hormones
- directly into the blood or intercellular fluids
What organs are both exocrine and endocrine?
pancreas, liver, and gonads
What are the two types of exocrine glands? What is the difference between them?
- simple glands have an unbranched duct
- compound glands have branched ducts
What are the shapes of exocrine glands and when does each shape occur?
tubular- if the ductal cells are secretory
acinar- if secretory cells form a dilated sac called an acinus
tubuloacinar- if secretory cells are in both ductal and acinar regions of the gland
Which glands produce thin, watery secretions such as sweat, milk, tears and digestive juices?
serous glands
Which glands produces a glycoprotein, mucin, that absorbs water to form a sticky secretion called mucus?
mucous glands
Which glands contains both serous and mucous glands?
mixed glands
Which glands release whole cells into ducts (i.e testes release sperm into ductus deferense and ovaries release ova into fallopian tube)
cytogenic glands
What is a merocrine secretion?
cells release product into a duct by exocytosis
What is a holocrine secretion?
cells mature, die, and then disintegrate to deliver accumulated product into duct
