Tissues Flashcards
Describe the cellularity of epithelial tissue
composed almost entirely of cells; little extracellular matrix; cells are connected by intercellular junctions
Describe the polarity of epithelial tissue
defined apical (top) and basal (bottom) surface
Describe the attachment of epithelial tissue
attach to basement membrane
What is basement membrane?
An acellular surface produced by epithelial and connective cells
What are the two layers of basement membranes in epithelial tissues?
basal lamina and reticular lamina
Is epithelial tissue vascular or avascular?
avascular
What are important functions of epithelial tissue?
physical protection, selective permeability, movement/clearing, secretion, sensating
What does the basal lamina secrete?
collagen, laminin, proteoglycans
What does the reticular lamina secrete?
reticular fibers, fibronectin, glycoproteins
tell me as much as you can about epithelial cell structure
refer to notes bestie
Describe this function of epithelial tissue: Physical protection
protection from dehydration, abrasion, and physical, chemical, or biological agents
Describe this function of epithelial tissue: Selective permeability
regulates the passage of certain molecules in or out of a certain region of the body; exchange: passive and transport: active or facilitated (ex. the lungs)
Describe this function of epithelial tissue: movement/”clearing”
pushing of fluid or other material along a surface
Describe this function of epithelial tissue: Secretion
release of materials (ex. sweat, saliva)
Describe this function of epithelial tissue: Sensation
receptors connected to nerve endings that can detect light, chemicals, mechanical stimuli, cold/heat
Desmosomes
Hold cells together
What happens in exchange epithelia
leaky exchange epithelium allows movement through gaps between the cells (bulk filtration/ diffusion)
What happens in transport epithelia?
tight junctions in a transporting epithelium prevent movement betweem adjacent cells (substances must instead pass through the epithelial cell)
Clearing/moving epithelia are normally
ciliated; columnar
(microvilli- expand surface area)
Examples of Sensory Epithelia
retina, cochlea
How are Goblet cells an example of secretory epithelia?
secrete mucus into the lumen of hollow organs such as the intestine
exocrine glands
secrete products through ducts; products enter “exterior”: intestinal lumen, skin surface
endocrine glands
ductless; products enter body “interior”; direct secretion into bloodstream or interstitial fluid
Merocrine
secretory products secreted by vesicular exocytosis (sweat, saliva)
Apocrine
partial cellular breakdown; cytoplasm and vesicular contents secreted ( milk, under arm sweat)
holocrine
entire cell lost with secretion; stem cells divide to replace lost cells (oil glands
Where are you going to find intercellular junctions in epithelial tissue?
near their apical surface
(this makes sense because they are the gatekeepers
molecules have to go from apical to basal)
In the ZO protein tight junction what binds to ZO1
occludin
In the ZO protein tight junction what binds to ZO2
claudin
In the ZO protein tight junction what binds to ZO3
JAM
What are adhering junctions made from
actin
adhering junctions are actin filament-based systems also known as…
zonula adherens
Where are you likely to find adhering junctions?
basal layer
microfilaments are made out of
actin
Intermediate Filaments are made out of
Keratin and laminin
Microtubules are made from
tubulin
3 major types of cytoskeletal elements
microtubules, microfilaments, intermediate filaments
intracellular proteins provide
structure and framework
E-Cadherin
helps cells stick together (extracellular)
Button desmosomes
tie cells together; flexible
hemidesmosomes
tie cell to basal lamina
Gap Junctions
allow transport between two cells without going through extracellular fluid; rapid communication between cells
Gap junctions are made from how many sub-units
6
the 6 subunits of a gap junction form a
hemichannel
each hemichannel is called a
connexon
each connexon is a
hexamer
2 hemichannels make
1 gap junction