Flashcards in MCB Lecture 36 Epithelial Tissue Deck (55)
Coordination of tissues
Coordination of cell types
What are the different types of tissue? (5)
Where is epithelial tissue found?
Lining external and internal surfaces and ducts
What are the different morphologies of epithelial tissues?
What type of morphology are the epithelial cells in blood vessels?
What type of morphology are the epithelial cells in intestine?
What type of morphology are the epithelial cells in skin?
What type of morphology are the epithelial cells in the respiratory tract?
Ciliated pseudo stratified
Describe how the epithelium in the respiratory tract provides protection
The cells secrete mucous that traps dirt and detritus.
The cilia beat up, moving the mucous up to the mouth where it is swallowed and excreted
What are two genetic mutations that cause problems in the respiratory epithelium?
1. Mutation in Dynein, preventing the cilia from beating
2. Cystic fibrosis: ion channel mutation, mucous is too thick to be moved up
Describe the function of the epithelium in the digestive tract
Villi to increase surface area
Absorption of nutrients at apical end: active transporter
Basal end: passive transporters, nutrients move down diffusion gradient into the blood stream
Describe the polarisation of epithelial cells
The position of the nucleus
Also, apical end and basal end
What are the different types of cell junctions? (5)
5. Focal adhesions
6. Hemi desmosomes
Where are tight junctions localised?
Near the apical region of a cell
What is the function of tight junctions?
They prevent movement of materials between two cells
Describe the structure of tight junctions
Interaction between the proteins on the two adjacent cells
What is the function of Claudin and occludin?
These are the proteins presented on the outermembrane of cell that form tight junctions, preventing movement of materials between cells
What is the function of Adherens junctions?
1. Sticks cells together
2. Epithelial folding
3. Cell sorting
Describe the structure of Adherens junctions. Which protein is involved?
Classical cadherin proteins are involved. The cadherins on adjacent cells interact at the N terminus
Linker proteins connect the cadherins to the actin filaments inside the cell
Between which two things are Adherens junctions present?
Cadherin interaction is ... dependent
Without calcium, the cadherin chains are floppy and can't interact with the cadherins of the adjacent cell
What are junctional complexes?
These are the localisation of certain types of junctions in certain regions
A single cell can have different types of junctions
How does cadherin interact with the cell membrane and actin?
Through linker proteins
How do two cadherins interact?
At the N terminus
What are some of the linker proteins that connect cadherin to actin
Alpha and beta
Describe the process of epithelial folding
There is a belt of actin and Adherens junctions in the apical region of cells
This belt contracts, and an invagination forms
This pinches off to form a tube
Describe Adherens junctions role in cell sorting
Cells presenting Adherens junctions will stick together
In this way, certain cells are grouped together
Which cell secretes mucus into the respiratory lumen?
The epithelium in which two organs is important for absorption?
What are some generally features of the apical region of epithelial cell?
What are some generally features of the basal end of epithelium?
Adhesion to ECM
Diffusion of materials
Secretion into sub mucosa
In polarised cells, organelles are ...
Differentially distributed, polarised
How do tight junctions affect the polarity of membranes?
It separates the different ends of the membrane.
Eg. The cilia and the basal end
Which junction is vital for the apical-basolateral polarity?
What sort of binding is there between Claudin and occludin in tight junction?
The more tight junction proteins, ...
The more impermeable
Why are Adherens junction said to be homophobic?
Interaction between with of the same molecule, classical cadherin
What gives skin it's high tensile strength?
Integrins will not engage ECM unless...
There is signalling
Eg. Activation of tallin
Outside - in signalling in focal adhesions requires other kinases because ...
What are these other kinases?
Because the integrins don't have kinase regions
Describe the tissue structure of the alimentary tract
Connective tissue (fibroblasts, collagen etc)
Surrounding layer of epithelium
What is transitional epithelium?
This is epithelium that has a different appearence depending on the state of the organ.
Ie, it can look squamous when stretched and cuboidal in the unstretched state
What is pseudo stratified epithelium?
All the cells connect to the basement, however, not all cells extend to the apical surface
What are the cell types in the respiratory tract?
Goblet cells (mucous secreting)
Basal cells (stem cells)
What type of epithelium is the thyroid?
What type if epithelium is the bladder?
What is the name of the disorder in which the cilia are immobile?
A Claudin molecule in a tight junction bonds ... with a ... molecule
Which junctions are important for organogenesis?
Adherens junctions: epithelial folding and cell sorting
Which cadherin family proteins are present in Desmosomes?
Describe which junctions intermediate filaments connect to, and how they do so
Desmosomes: connects to the side of intermediate filaments
Hemidesmosomes: connects to the ends of intermediate filaments
What are the linker proteins in Desmosomes?
How does inside out signalling affect outside-in signalling?
Once an ECM protein has been engaged through inside-out signalling, outside in signalling occurs