BL L7 Flashcards
On lateral surface, what holds the epithelial cells together?
‘AT GDC’, but better remembering it ‘TAD GC’ (like tad-juicy), as in the right order
- Tight junctions
- Adhesion junctions (adhesion belt)
- Desmosome
- Gap junctions
- Cell adhesion molecules like integrin
On the basal surface, what holds the epithelial cells to the basement membrane?
‘HIF’
Hemi-desmosomes
Integrins
Focal adhesion proteins and placques
(proteoglycans)
(cell adhession molecules e.g. integrins)
What makes up the basal membrane?
Basal lamina and retricular fibre:
- Basal lamina: thin layer of gel-like fluid excreted by epithelial cells
- Reticular lamina: sits below the lamina, acts as a net of collagen fibres
Tight junctions
- Seals neighbouring cells together to prevent leakage of molecules between them (e.g. large proteins and viruses)
- Gut-paracellular transport (in the gut, tight junctions can open for milli seconds to allow small molecules e.g. sugars, amino acids, water to cross the underlying tissue, called paracellular transport as going across the cell)
- Location: very top of the cell, nearest the apical surface
Adhesion junction
- Joins actin bundle in one cell to a similar bundle in the neighbouring cell
- Belt of adhesion (goes all the way around the epithelial cell)
- Found in pairs. Adhesion junctions are between the E-cadherin proteins on one cell and E-cadherin proteins on another cell, Ca2+ between the E-cadherin proteins)
- Location: 1/3 distance from luminal surface
(a and a, actin and adhesion)
Desmosomes
- Joins the intermediate filaments in one cell to those in a neighbour cells
- Strongest cell to cell adhesion, found in tissues that experience intense mechanical stress, like cardiac muscle and bladder tissue, pregnancy uterus)
- Randomly distributed
- Location: 1/2 way between top and bottom of cell
(I and D, D has I in)
Gap junctions
- Allows the passage of small water soluble ions including Ca2+ ions and molecules from one cell to another
- Quickly communicates changes between cells (e.g. will communicate if ‘their cell’ has a change in ATP or electrolyte concentration)
- Location: Close to the base of epithelial cells
Hemi-desmosome
- Role is to anchor the epithelial cells to the basal lamina and prevent loss to external surface
- (intracellular intermediate filaments attached to lamina by integrins)
Focal adhesion
- Anchors actin filaments in a cell to the basal lamina
a and a, actin and focal aaaadhesion
Fill in the gaps:
Overall:
Epithelial cells adhere to epithelial cells through __________
Epithelial cells adhere to basal lamina (extracellular matrix) through _________
Epithelial cells adhere to muscle cells through __________
Tissues adhere to other tissues (e.g. nerves and blood vessels) through __________
- cell surface proteins
- cellular adhesion molecules
- connective tissue fibres
- connective tissue fibres
Name one type of membrane
- Mucosal membrane
What does the mucosal membrane line?
Give examples of what it lines
What does mucosal membranes secrete and why?
Examples of where it is
- Lines all the ‘moist’ hollow internal organs
- Lines tracts (tracts are like tubes = have openings)
- Secrete mucous, this is a thick protective fluid.
- Function: Stop pathogens and ‘dirt’ from entering the body / Prevents bodily tissues from becoming dehydrated (mucus - contains mucins proteins that attract water helping to keep the tract moist, side note- electrolytes also keep the tract moist as they attract water too) / Lubricates the surface (additional function of mucus)
- e.g. GI tract, Urinary tract, Respiratory tract
How many layers are in GI tract?
6
Name and describe all the 6 layers in the GI tract
M Epithelial cells L Connective tissue M Muscle S Connective tissue M Muscle S Connective tissue
- Mucosa: Epithelial cells lining the lumen (secretes mucus)
- Lamina propria: Connective tissue layer
- Muscularis mucosae: Thin discontinuous smooth muscle layer (not epithelial cells!)
- Submucosa: Connective tissue layer that contains arteries and veins
- Muscularis externa: Smooth muscle layer that has muscle fibres going in two different directions: inner circular muscle (squeeze the tube flat) / outer circular muscle (push and pull the internal components)
- Serosa: Another connective tissue layer (contains fluid, allowing this layer to slide / contains collagen, elastin fibres, smaller artiers, veins, nerve fibres)
How many layers make up the mucosa in the GI tract and name them
3 layers:
- Mucosa: Epithelial cells lining the lumen (secretes mucus)
- Lamina propria: Connective tissue layer
- Muscularis mucosae: Thin discontinuous smooth muscle layer (not epithelial cells!)
Describe the inner and outer layers in the muscularis externae (GI tract)
- Inner circular muscle (‘G I, C I’)
- Outer longitudinal muscle
Describe layers in oesophagus
All 6 layers
- Muscularis externae is important for the peristalsis movement of food
Describe layers in stomach
All 6 layers
- Muscularis externa: 3 layers (instead of 2 which is characteristic for GI tract). Layers are - oblique, longitudinal, circular.
- Rugae: the folds you can see in the lumen of an empty stomach
- Very thin lamina propia layer
Describe layers in dejunum
All 6 layers
- Plicae circulares (finger like appearances)
Describe layers in large intestine (colon)
All 6 layers
- Crypts of Lieberkuhn (these have simple columnar epithelial cells)
Role of the crypts of Liberkuhn
- Produces mucus
Overall - functions of mucosa in GI tract and which specific layers help with this?
- To absorb substances from the lumen (except in the stomach and oesophagus).
- Prevent ingress of pathogens
- Move contents and expel waste (out through anus end)
- Epithelial cells aid processes 1 and 2 (folding mucosa, microvilli, peristalsis)
- Lamina propria contains lymphatic tissue aiding process 1
- Muscularis mucosa folds mucosa to increase surface area (aids 1 and 2)
- Muscularis externa performs peristalsis (aids 3)
Briefly describe the structure of the UT system
- Kidney
- Ureter
- Bladder
- Urethra
Shape of the epithelium lining collecting ducts
Simple cuboidal epithelium
Shape of the epithelium in the Bowman’s capsule and glomerular capillaries
Squamous epithelium
Shape of the epithelial in the ureter and the bladder
Transitional
Name the epthelial cells in the UT tract (they have a specific name)
Urothelium
Describe the layers in the ureter and the bladder
- add detail about muscularis mucosa and muscularis externa
All 6 layers
- Muscularis mucosa (important in changing the shape of the tube when urine passes through)
- Muscularis externa (layers are the opposite way around compared to the GI tract)
- inner longitudinal muscle
- outer circular muscle
What is different about the muscularis externa layer in GI tract and UT tract?
GI tract:
- Inner circular muscle (‘GICI’)
- Outer longitudinal muscle
UT tract:
- Inner longitudinal muscle
- Outer circular muscle
Bladder
What are the epithelial cells called?
Why is there lots of smooth muscle?
Why does some of the outside tissue contain lots of fat cells?
How long do the epithelial cells in the bladder last?
Why do the epithelial cells produce mucus in the bladder?
Why are the tight junctions well packed?
- Urothelium cells
- Can contract and remove the contents of the bladder
- Fat cells act as ‘shock absorbers’ for an expanding bladder
- Last 2-7 days (depending on how much urine you produce and it’s pH)
- Produce mucus because the urine is very acidic (pH 6), the mucus protects the urothelium cells from damage
- Tight junctions are very well packed to prevent leakage (keeping urine in the lumen)
pH of urine
pH 6
Describe layers in urethra
- Structure is similar to the bladder
- Mucus glands produce lots of sticky mucus, prevent ingress of pathogens
Overall - Functions of UT (3)
- Absorption of essential nutrients back into the blood
- Prevention of pathogen entry
- Removal of waste products
How is the respiratory tract divided into 2 parts?
- Conducting portion (nasal cavity to bronchioles)
- Respiratory portion (Respitatory bronchioles to alveoli)
Brief description of Respiratory tract
- Nasal cavity
- Trachae
- Bronchi
- Bronchioles
- Alveoli
Describe the layers in the Trachea and primary bronchi
Mucosa: Epithelial layer, covered in cilia (moves dust, debris etc towards the mouth). Lamina propria is very thin, no longitudinal muscularis mucosa layer
Submucosa
Cartilage: Two layers - Perichondrium layer (contains fibroblasts that lay down collagen fibres), Chrondrogenic layer (from which cartilage forms)
What key layer does the trachea, primary, secondary and teritary bronchi not have?
No outer smooth muscle layer
Describe the layers in the secondary and tertiary bronchi
Similar to Trachea and Primary bronchi except:
Cartilage is not present in full rings (present in a crescent shape)
Again, no outer layer of smooth muscle
Alveolus structure
- Lined endothelium cells
- Folds in basal lamina allows for expansion
- Surrounded by many layers of elastin fibres, role it is to provide elastic recoil
- Connective tissue (lots of collagen and elastin fibres)
What is secreted in the trachea and bronchials?
- Mucins and water (makes sticky mucus)
- Serum products (lubricates the surface)
- Lysozyme (destroys bacteria)
- Anti-protease (inactivates bacterial enzymes)
Describe the mucosilarly escalator/elevator
With the ‘cilia wave’, mucus moves material to the oral cavity so the material can be swallowed
What does the basal bodies look like? (part of cilia)
Purple line at the base of cilia cells in H+E stain
What type of cells make mucins and why do they appear white?
Goblet cells are where mucins are made.
They are white because mucins are glycosylated proteins and have lots of sugar on them, sugar attracts lots of water, this is what makes them sticky
