Epithelial cells Flashcards
What happens in the nucleolus?
Ribosomal subunits are synthesised
What three types of filament constitute the cytoskeleton?
Microtubules
Intermediate Filaments
Microfilaments
What are microtubules made of and what is the diameter of a microtubule?
Alpha and beta tubulin heterodimers
20nm.
What are microtubules used for?
Cell shape
Movement of organelles through the cell – involves motor proteins
Involved in spindle fibre formation
Describe the organisation of microtubules in cells.
They originate from a point within the cell called the microtubule organising centre (MTOC)
Microtubules are an important structural component for which cellular features?
Cilia and flagellae
Which component of the cytoskeleton distinguished different cell types?
Intermediate Filaments – different for different cell types
What are intermediate filaments usually connected to?
Desmosomes which are connected to cytokeratins
Where else are intermediate filaments found than in the cytoplasm and what do IF provide to cells?
Nuclear lamin – on the internal surface of the nuclear envelope – provides support
-Give mechanical strength
What are microfilaments made of?
Actin
What do microfilaments associate with and what is it involved in?
Adhesion belt and accessory proteins e.g. myosin
Involved in cell shape and cell movement.
What is the monomer of microfilaments and where is it found and what structure does it have ?
G-actin (globular actin)
- usually near the periphery of the cell
- helical structure
Define ‘Extracellular Matrix’.
The insoluble material found extracellularly.
What are the four main types of cell-cell junctions (in order of apical to basal)?
Tight junction
Adhesion belt
Desmosomes
Gap Junctions
What is the role of tight junctions?
Seals off the paracellular pathways. Allows polarity. Stops proteins that diffuse through membranes.
Describe the structure of the adhesion belt.
It consists of a cadherins, which interact with similar molecules on the adjacent cell and clusters to form these junctions. Actin filaments are bound to the adhesion belt. It is the first to form- Master Junction
Describe the structure of desmosomes.
Also involves cadherins interacting to maintain adhesion. Cadherins links to the Intermediate filaments.
What is the role of Gap junctions?
Allows transport of small molecules between cells.
Important to communicate between the cells.
What are the cancer called when they originate from:
- epithelial cell: carcinomas
- mesenchymal: sarcomas
- heamatopoietic: leukaemias
- neural : neuroblastomas ( from neurone precursors) and gliomas (from glial cells)
What does peroxisomes contain?
Contain enzymes involved in lipid and oxygen metabolism e.g. catalases, peroxidases.
What is the main function of the nucleolus?
It is the site of ribose production
What is mesenchymal cells
connective tissue
Which major cytoskeletal component is associated with the desmosome cell-cell junctions in epithelial cells?
Cytokeratins
what are the main types of cells and give examples?
Epithelial cells: cells forming continuous layers, these layers line surfaces and separate tissue compartments.
Mesenchymal cells: cells of the connective tissues, e.g. fibroblasts (many tissues), chondrocytes (cartilage), osteocytes (bone), muscle cells (skeletal, cardiac, smooth), the endothelial cells lining blood vessels.
Haematopoietic cells: blood cells and the cells of the bone marrow from which they are derived.
Neural cells: cells of the nervous system having two main types; neurones (carry electrical signals) and glial cells (support cells).
what are the two types of endoplasmic reticulum?
rER: exists as flattened sheets which is studded on its outer surface with ribosomes.
sER: more tubular and lacks ribosomes. It has a major function in lipid metabolism.
