Class notes
First Class Lecture notes Dynamic Cell Module
- Course
- Institution
Cell junctions lecture notes
[Show more]
Seller
Follow
jessicabrown-11
Content preview
Exploring our junctions…1) In what general ways do cells interact to form tissues?
Animal tissues fall into 2 broad categories of cellular organisation:
Δ Epithelial tissues – cells = dominant feature
Cells are closely bound together into sheets called epithelia. The ECM
is scarce, consisting mainly of a thin mat called the basal lamina (or
basement membrane) underlying one face of the sheet.
Within the epithelium, cells are attached to each other directly by cell-
cell adhesions, where cytoskeletal filaments are anchored.
Form barriers – e.g. the epidermis covering the skin, forming a barrier
between body and external environment, but also all sorts of other
structures such as the lining of the gut.
Δ Connective tissues – ECM = dominant feature
ECM is plentiful and cells are sparsely distributed within it. However,
the ECM is both secreted by and signals to the mesenchymal cells within.
The matrix is rich in fibrous polymers, especially collagen, and it is the matrix (rather than the cells) that
bears most of the mechanical stress the tissue is subjected to.
Direct attachments between one cell and another are rare, but the cells have important attachments to the
matrix.
E.g. bone or tendon
2) What are cell junctions?
Δ Definition : A specialised site on a cell at which it is attached to another cell or the extra cellular
matrix
, Δ All of these cell junction components were identified in the early days of electron microscopy (electron dense
so easy to see), creating a potential confusion because they were named because of their appearance under
the TEM, without knowledge of the underlying molecular basis.
Basis of cell-cell interactions is a homophilic mechanism – same =transmembrane receptor protein in the
plasma membrane of both cells that mediates cell-cell interaction
By contrast, cell-ECM interactions would involve heterophillic rather than homophilic mechanisms (different
protein receptors in the cell compared to the ECM)
3) What are the major types of cell junction and what are their
functions?
Cell junctions can be classified into 4 functional groups (each
with a different molecular basis):
Similar principle of recognition of partners - - either like-for-like in nearby
cells, or binding to ECM components.
Δ Anchoring junctions: transmit stresses and are tethered to
cytoskeletal filaments inside the cell. Link cells together or to the
ECM.
Actin filament attachment sites:
1. Adherens junctions – cell-cell junctions
2. Focal adhesions – cell-matrix junctions
Intermediate filament attachment sites:
1. Desmosomes – cell-cell junctions
2. Hemidesmosomes – cell-matrix junctions
Δ Occluding junctions: seal the gaps between cells in epithelia so as to make the cell sheet into an
impermeable (or selectively permeable) barrier. Also maintain cell polarity (distinction between apical and
basolateral surfaces).
1. Tight junctions (vertebrates)
2. Septate junctions (invertebrates)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller jessicabrown-11. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $9.68. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52355 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now