Tissues 1 Flashcards
What is the single lipid bilayer that binds animal cells?
The plasma membrane
What is the nuclear envelope?
A double lipid bilayer that encloses the contents of the nucleus.
What is an organelle?
Membrane bound/membrane associated structure within a cell
What do eukaryotic cells have?
- Membrane bound organelles
2. A highly compartmentalised cytoplasm
What do the darker regions of a TEM nucleus show?
Heterochromatin
Why is heterochromatin in the darker regions less active?
It is more condensed
What is the nucleus?
- The site of the production of sub-units of ribosomes.
- An aggregate of clusters of rRNA genes
- Contains synthesised rRNA and proteins - assembled to make ribosomal subunits.
How many pairs of rRNA genes are there in humans?
5.
What structure is the nuclear envelope continuous with?
The endoplasmic reticulum
What are the 3 faces of the Golgi apparatus? Where do they face?
Cis - towards nucleus
Medial
Trans - towards plasma membrane
What are peroxisomes?
- Single membranes
2. Contain enzymes involved in lipid and oxygen metabolism.
What is the nuclear lamina?
- Specialised cytoskeleton
- Formed on internal surface of nuclear envelope
- Important in cell division - controls assembly/disassembly of nuclear envelope in cell division
Where are Ca ions stored in cells?
SER
What are the 3 main types of cytoskeleton?
- Microtubules
- Intermediate Filaments
- Microfilaments
What are microtubules made up of?
Alpha-tubulin and Beta-tubulin
What to microtubules do?
- Involved in cell shape
- Act as tracks for the movement of other organelles/components.
- 20nm
may involve other accessory proteins
What are microtubules the major component of?
Cilia and Flagellae
What is the centrosome
The central point of the cell from which the microtubule radiates out of (aka Microtubule Organising Centre, MTOC)
What forms the mitotic spindle?
Microtubules
What is the 9+2 arrangement?
9 MT doublets + 2 central MTs form the core of cilia and flagella
What are intermediate filaments?
- Group of filamentous protein polymers - form rope like filaments
- Cell type determines type of IF it has.
- Give mechanical strength to cells
- 10-15nm diameter
What connects desmosomes?
Cytokeratin
What are nuclear lamins?
- IFs that form a network on internal surface of nuclear envelope.
- IFs Involved in stabilising envelope
What are Microfilaments?
- Actin polymers
- Associated with adhesion belts in epithelia and endothelia.
- 5-9nm in diameter
- Involved in cell movement and shape
- Have accessory proteins (e.g. myosin) - acts with actin to control actin organisation and cell movement (by giving non-muscle cells contractile properties)
Where are actin MFs typically found in the cell?
Lining the peripheral regions of the cell.
Actin MF - what is the monomer?
G-actin
Actin MF unit - what type of actin?
F-actin
Which parts of the cytoskeleton are in the cell core?
Microtubules and Intermediate filaments
How are the cytoskeleton parts subject to remodelling?
Through biochemical and biomechanical signals.
What are the main cell types?
- Epithelial cells
- Connective tissue cells (e.g. fibroblasts/osteocytes/chondrocytes)
- Contractile tissue cells (smooth muscle/cardiac muscle/skeletal muscle)
- Haematopoietic cells
- Neural cells
Describe epithelial cells.
- Cells form continuous layers
2. Line surfaces and separate tissue compartments
Describe Mesenchymal cells.
- Cells of connective tissues (e.g. fibroblasts/chondrocytes/osteocytes/muscle cells)
Describe haematopoietic cells.
- Cells originating from bone marrow.
- Comprise mainly cells from blood
- Include the cells from which blood cells originate
Describe neural cells.
- Cells of the nervous system
2. 2 main types - neurones and glial cells
What do glial cells do?
Act as support
What comes under the umbrella “mesenchymal”?
Connective tissue and muscle
What are carcinomas?
Epithelial cancers
What are sarcomas?
Mesenchymal cancers
What are leukaemia?
Haematopoietic cancer (bone marrow)
What are lymphomas?
Haematopoietic cancer (lymphocytes)
What is a neuroblastoma?
Neural cell cancer (neurones)
What are gliomas?
Neural cell cancer (glial cells)
Define a tissue.
- Group / groups of cells
2. Type, organisation and architecture are integral to its function.
What are tissues made up of?
Cells and extracellular matrix.
What forms the insoluble part of the extracellular environment?
Extracellular matrix
What is the extracellular matrix composed of?
Fibrillar proteins (e.g. collagens/elastin) embedded in a hydrated gel
Give an example of poorly organised extracellular matrix.
Loose connective tissue
Give an example of highly organised extracellular matrix.
Tendon, bone, basal lamina, etc
How do epithelial cells form continued, cohesive layers?
They make organised, stable cell-cell junctions.
Name 4 functions of epithelial layers.
- Transport
- Absorption
- Secretion
- Protection
What do cell-cell junctions give epithelia?
- Mechanical integrity.
2. Seals intracellular pathways
Where are cell-cell junctions found?
At the apical region of cell-cell contact. As a junctional complex
What are the 2 forms of junctional complex.
Zonulae (belts)
Maculae (spots)
What is the order of the apical junctional complex?
- Tight Junction
- Adhesion belt
- Desmosomes
Why are gap junctions important?
Allow direct communication between adjacent cells.
Where are desmosomes scattered?
Throughout the lateral membrane.
Tight Junctions.
- aka Zonula Occludens
- Points on adjacent lateral membranes form close contacts at apical lateral membranes
- Form network of contacts (more elaborate network = tighter seal)
- Seal paracellular pathways.
How do tight junctions contribute to polarity?
By segregating the apical and basolateral membranes
Adhesion belt
- aka Zonula adherens
- Usually just basal to apical tight junction
- Transmembrane adhesion molecule = cadherin
- Junction controls stability other junctions (hence MASTER JUNCTION)
What do cadherins associate with?
Microfilament (actin) cytoskeleton
Desmosome.
- aka Macula adherens
- Found between adjacent cell membranes
- Uses transmembrane adhesion molecule LIKE cadherin
- Linked to Intermediate filament cytoskeleton
- Provides mechanical continuity between cells.
Gap Junction
- aka macula communicans
- Consists of clusters of pores that are continuous with pores in adjacent cell membrane
- Allows passage of ions and small molecules between cells
- Passage affected by pH, Ca conc, Voltage and signalling molecules
Synapse.
- Mainly found in neural tissue
- Button like junctions
- Also cell-cell junctions
- One way chemical communication system via chemical signals.
- Signals/receptors utilised at synapses.
Cell-cell junctions are labile. What does this mean?
Able to change their assembly and organisation.