Epithelial cells Flashcards
What types of cells are haemopoietic cells?(3)
Blood cell
Tissue-resident immune cells
Cells derived from bone marrow.
What are neural cells?
Cells that constitute the nervous system: Neurones (transmit electrical signals), and glial cells (provides neurone support and insulation - Schwann cell).
What are contractile tissues?
Skeletal muscle, cardiac muscle, smooth muscle.- Tissue with the ability to contract.
What are connective tissue cells?
Fibroblasts (many tissues), chondrocytes (cartilage), osteocytes (bones)- Connects, bind and supports tissue cells.
What are epithelial cells?
Cells forming continuous layers, layers line surfaces and separate tissues compartments- variety of alternative function- Secretion, selective absorption, protection, transcellular transport and sensing.
What are squamous epithelial cells?
Flattened, plate shape, abundant cytoplasm and small round circular nucleus.
What are columnar cells?
Arranged in columns; approximately 3000 microvilli per cell (maximises surface area for absorption). Simple columnar epithelial cells secrete molecules- enterocytes assist in molecular degradation in gut.
What are cuboidal cells?
Cuboidal: Cube-like (lines nephrons, ovaries and ducts)- main function is secretion.
What are stratified epithelium?
Multiple layers of cells
What are pseudo-stratified epithelium?
This epithelium appears to be multi-layered, but on close examination, the surface cells have contact with the basal lamina. e.g. airway (trachea and bronchi) epithelium, various ducts in the urinary and reproductive tracts.
What is epithelial cell polarity?
Membrane is organised into discrete domains through formation of junctions, distinct polarity has apical membrane at the luminal surface and a basolateral domain (basal surface is in contact with the extracellular matrix)
What is a lateral membrane?
Membrane is situated between two surfaces, membranes of adjacent membrane appose each other
Why is polarity important?
Important for secretion of fluid, and solute transport
Directional flow and ion/cotransporter proteins
What are tight junctions?
Belt around apical lateral membrane (membranes of two adjacent cells accumulate together to form a barrier). Membranes are attached by strands of transmembrane proteins (claudins and occludins). Binding action prevents molecules from passing in between the cells- helps to maintain diffusion gradients
What are adherens?
Initiation and stabilisation of cell-cell adhesion, regulation of the actin cytoskeleton, intracellular signalling, and transcriptional regulation. Junction holds adjacent epithelial cells together.
What proteins comprise adherens?
Cadherins bound to calcium ions
What are desmosomes?
Cell-cell anchoring junctions- provide mechanical stability as a result of strong cellular adhesives.
What are gap-junctions and what do they allow for?
Allows various molecules and ions to pass between cells. Composed of two connexons (hemichannels) that align across the intercellular space. Hemichannels composed of complex of six connexin proteins (transmembrane domains). Gap junctions allow for electrical communication between cells, and passage of second messengers.
What is exocrine secretion?
Exocrine secretion is the secretion of molecules within the duct or lumen
What is endocrine secretion?
Secretion directly into the blood
Which membrane do exocrine cells release secretions through?
Apical membrane
Which membrane do endocrine cells releases secretions into?
Basal membrane
What is constitutive secretion?
Secretary vesicles as they formed move directly to the plasma membrane, releasing their contents immediately
What is stimulated secretion?
Stored in cytoplasm within secretory vesicles, fusing with membrane upon stimulation
Which cells are produced within the small intestine?
Stem cells are present within the crypt of Lieberkuhn , replacing cells lost from the villus tip
How does hyperproliferation occur?
Cell production > cell loss, cells accumulate into a thick layer known as corns
What conditions cause hyper proliferation?
Frequent abrasions and pressure
Which virus causes hyper proliferation?
The papilloma virus, controls stratified squamous epithelium
What characterises a keratinising cell?
Epithelial cells which produce keratin and in doing so die, becoming thicker, stronger, protective structures (e.g. epidermis (skin epithelium). Such cells lose their cellular organelles and nuclei, not visible under light microscopy.
How can you determine the direction a cell will secrete its substances towards?
Location of secretory vesicles, golgi apparatus, mitochondria
How do stratified epithelial cells replace lost surface cells?
By dividing and migrating towards the apical membrane and replacing the lost cells.
What can be a consequence of epithelial hyperproliferation?
Adenoma formation - Benign tumour
