Tissues 2 Flashcards
Where do epithelia lie?
Basal lamina of connective tissue.
Apical side of epithelia is open (not in contact with anything else)
What are the 3 shapes of epithelia?
Cuboidal (uniform shape in 3D)
Columnar (extended)
Squamous (flattened)
What are the types of layers of epithelia?
Simple
Stratified
Give 3 examples of simple squamous epithelia.
- Lung alveolar
- Mesothelium
- Endothelium
Give an example of simple cuboidal?
Kidney Collecting Duct
Give an example of simple columnar?
Enterocytes
What are the 2 types of stratified squamous cells?
- Keratinising - nuclei not visible in surface layer cells
2. Non-keratinising - nuclei visible in surface layer cells
Give examples of keratinising cells. (DRY)
- Epidermis, skin
Give examples of non keratinising cells. (MOIST)
- Linings of the mouth
- Oesophagus
- GI tract
- Cervix
What is present in the base of keratinising cells?
Stem cells
They replace surface cells as they are lost
What are pseudo stratified epithelia?
Cells that appear to be stratified but are simple
Give an example of a pseudostratified epithelia?
Upper airway epithelia
Why do epithelia need functional polarity?
Secretion, transport, absorption are UNIDIRECTIONAL
What is the key for epithelial function?
Membrane polarity
What separates the apical domain from the basolateral domain?
Cell-cell junctions
What do tight junctions do?
Restrict paracellular permeability?
How do tight junctions keep the apical and basolateral domains distinct?
Prevents mixing of membrane components
The intestinal epithelium has absorptive and secretory cells. Which cells are absorptive and which are secretory?
Enterocytes - absorptive
Goblet cells - secretory
What are the two “…crine” functions that secretory tissues can be?
Exocrine (into gut)
Endocrine (into blood)
Where does the pancreas secrete digestive enzymes?
Lumen of the gut
Where does the pancreas secrete islet hormones?
Bloodstream
Where do endocrine cells have their secretory vesicles?
In the basal cytoplasm
They secrete contents into the basal aspect.
Where do exocrine cells have their secretory vesicles?
In the apical cytoplasm
They secrete into the apical aspect.
How are tissues arranged when the main purpose is secretion?
Into tubules and ducts
Endocrine tissues surround blood vessels
What are the 2 types of secretion?
Constitutive
Stimulated
What is constitutive secretion?
Vesicles go straight to the membrane and fuse as soon as they are formed
What is stimulated secretion?
Requires a stimulus to send vesicles to membrane and fuse
Give an example of constitutive secretion?
Plasma protein production by hepatocytes (constitutive endocrine)
Give an example of stimulated secretion?
Neurotransmitter release when action potential reaches axon terminus
Fight or flight (stimulated endocrine)
Pancreatic secretion of digestive enzymes (stimulated exocrine)
What are the 3 layers of the skin?
Epidermis
Dermis
Hypodermis
Non keratinising epithelia
What is the epidermis?
Keratinised Stratified Squamous epithelium - barrier to environment
What is the dermis?
Cuboidal basal cell layer (stem cells) - forms layer of cells that will later renew the top
Callouses = responses to pressure. Continued pressure produces callouses as skin responds to pressure with mitosis
What can defects in cytokeratins or cell junctions cause?
Epidermal damage may occur - cause blistering disease
What happens to CNS cells if they die?
They are lost
How are surface epithelial cells in the villus renewed?
Stem cells in the intestinal crypt gradually differentiate as they move up
How are surface epidermal cells renewed?
Dermis region is where stem cells differentiate as they move up.
