Epithelial Cells and Tissues Flashcards
What are tissues
A group of groups of cells whose type, organisation and architecture are integral to its function
Tissues are made up of cells, extracellular matrix and fluid
What are the five main cell types
Connective tissue cells - fibroblasts, condrocytes, osteocytes
Contractile tissues - skeletal muscle, cardiac muscle, smooth muscle
Haematopoietic cells - blood cells, tissue-resident immune cells, cells of bone marrow
Neural cells - cells of the nervous system, neurones and glial cells
Epithelial cells - cells forming continours layers which surface and separate tissue compartments
Tumours based on where they originate
Epithelial cells - carcinomas
Mesenchymal cells - sarcomas
Haematopoietic cancers - leukaemias or lymphomas
Neural cells - neuroblastomas or gliomas
Epithelial Classification
Shape: squamous, cuboidal, columnar
Layering: single layer, multi-layer
Single squamous epithelium
Found in the lung alveolar (air sac) epithelium
Mesothelium (lining major body cavities)
Endothelium lining blood vessels
Allow for exchange to happen
Simple cuboidal epithelium
Linings found in ducts - those lining the kidney collecting ducts
Simple columnar epithelium
Absorption and secretion of molecules
Enterocytes lining the gut involved in the take up of breakdown products of digestion
Stratified squamous epithelium
Keratinizing: epithelial cells which produce keratin and become thicker in doing so. Lose their cellular organelles and nuclei, not visible under light microscopy
Non-keratinizing: Epithelial cells which do not undergo keratinisation, retain their nuclei and organelles (line mouth, oesophagus, anus, cervix and vagina)
Keratinizing and non-keratinizing
Keratinizing epithelium can form thick layers that protect underlying tissues from various physical and chemical insults
Pseudo-stratified epithelium
Surface cells have contact with basal lamina
e.g. airway epithelium, various ducts in the urinary and reproductive tracts
What is the membrane between two adjacent cells
Lateral membrane
What is required to give directionality of the epithelial cells
epithelial polarity
Why can directionality only be achieved when transported is polarised
Only pumping on one aspect of the membrane
Where do tight junction form
Involved in sealing the gap between cells
Apical membrane
What is the adherens junction
Master junctions which controls the formation of the other junctions
What is the desmosomes junction
Form mechanically tough junction between cells
Resist mechanical stress
What does the gap junction do
Form pores between cells to allow cells to share material
What are the key features of transporting epithelia
Plasma membranes contain high concentrations of ion transporters
Mitochondria concentrated towards basal lamina
Ion and water transport will have directionality
What are the key features of absorptive epithelium
Carriers transporting nutrients
found in Absorptive intestinal cells (enterocytes) and kidney proximal tubule cells
Secretory cells are found among the absorptive cells of the intestinal villi
Picture of the brush-border membrane
What are the key features of the secretory epithelium
Two main types of secretion: exocrine (into a duct or lumen) and endocrine (into the bloodstream)
Picture of the secretory epithelium of exocrine cells
Picture of secretory epithelium of an endocrine cell
What other ways you can classify an endothelial cell
Constitutive - secretory vesicles move directly to plasma membrane and release contents as they are formed
Stimulated - secretory vesicles are stored in the cytoplasm and only fuse with the plasma membrane to relase their contents
