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Sem 4, case 1 (oesophageal cancer) > intro to epithelial solute and water transport (mini learning) > Flashcards

intro to epithelial solute and water transport (mini learning) Flashcards

(80 cards)

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1
Q

Which fluids make up the extra cellular fluid ?

A
  • interstitial fluid
  • plasma
  • transcellular fluid (CSF, synovial fluid etc)
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2
Q

Is the GI tract considered internal or external space ?

A

external space

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3
Q

Which membrane of the epithelium faces into the external space ?

A

apical membrane

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4
Q

Which membrane of the epithelium faces into the interstitial space ?

A

basement membrane

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5
Q

What type of membrane junction separate neighbouring cells ?

A

Tight junctions

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6
Q

What type of membrane junction allows for communication between cells ?

A

Gap junctions

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7
Q

What types of membrane junction provide structure to the epithelium ?

A
  • Adhering junction
  • Desmosomes
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8
Q

Are ‘tight junctions’ permeable or impermeable to most ions ?

A

impermeable

leaky to some small ions and water

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9
Q

Are the heads of phospholipids hydrophilic or hydrophobic ?

A

hydrophilic heads

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10
Q

Are the tails of phospholipids hydrophilic or hydrophobic ?

A

hydrophobic tails

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11
Q

What is the function of cholesterol in the phospholipid bilayer?

A
  • provide structural integrity
  • provide precursors for fat soluble vitamins and steroid hormones
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12
Q

Give examples of integral transmembrane proteins …

A
  • membrane transporters (channel proteins etc)
  • G proteins
  • cell surface receptors
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13
Q

What is the phospholipid bilayer impermeable to ?

A
  • Polar molecules
  • Ions
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14
Q

Describe the movement of ions through the sodium-potassium pump …

A

3Na out
2K in
using energy generated in ATP hydrolysis

keeps relative negative charge inside cell = membrane potential

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15
Q

What is the purpose of ion pumps ?

A

creating and maintaining electrochemical gradients

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16
Q

What does the K+ gradient (from the Na-K pump) generate ?

A

membrane potential

= keeping inside of cell less negative, so more positive ions want to diffuse into the cell

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17
Q

What does the Na+ gradient (in the Na-K pump system) drive ?

A

secondary active transport

= drives other passive transporters due to them leaving the cell and creating a more negative gradient inside the cell

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18
Q

What drives passive transport across membranes (ion channels etc) ?

A

the electrochemical gradient

= conc. gradient and membrane potential

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19
Q

Do carrier proteins use active or passive transport ?

A

passive

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20
Q

What determines transport through carrier proteins ?

A

the conc. gradient

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21
Q

What are the 2 subtypes of carrier protein?

A
  • co-transporters
  • exchangers
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22
Q

What does a co-transporter do ?

A

Transports multiple ions into the cell together = symporter

e.g co-transport of glucose

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23
Q

What does an exchanger do?

A

Transports multiple ions in/out of cell but in different directions = antiporter

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24
Q

What kind of active transport do co-transporters and exchangers use ?

A

Secondary active transport

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25
What is meant by secondary active transport ?
transporting an ion in the direction of its electrochemical gradient causes another ion to travel against its electrochemical gradient **= active transport using a conc gradient already established by an ion pump**
26
What are the concentrations of Na and K like in intracellular fluid ?
Low Na+ High K+ *established by the Na-K pump*
27
What are the concentrations of Na and K like in extracellular fluid ?
High Na+ Low K+ *established by the Na-K pump*
28
What types of diffusion are classed as passive transport ?
- simple diffusion - facilitated diffusion
29
Do molecules move along or against their concentration gradient in passive transport ?
**along** their conc. gradient *high conc to low conc*
30
Do molecules move along or against their concentration gradient in active transport ?
**against** their conc. gradient *low conc to high conc*
31
What channels does water travel through?
Aquaporins
32
Define osmosis …
Movement of water from an area of **low solute** concentration **to high solute** concentration **through a semipermeable membrane**
33
What is osmolarity ?
measure of osmotic pressure
34
What are the 3 categories of osmolarity ?
**Hypertonic** = a more solute concentrated solution = **water would leave cells** placed in a hypertonic solution **Isotonic** = solute concentration is in **equilibrium** with surroundings **Hypotonic** = a less solute concentrated solution = **water would enter cells** placed in a hypotonic solution
35
What % of Saliva secretion comes from the parotid gland when stimulated ?
50%
36
Which salivary gland secretes the majority of saliva ?
Parotid gland
37
What % of saliva is secreted from the submandibular glands when stimulated ?
35%
38
Which salivary gland secretes the least amount of saliva ?
sublingual
39
Rank the salivary glands in order of the amount of saliva they secrete (1 = most)…
1. **Parotid** (60% of saliva from here) 2. **Submandibular** (35% of saliva from here) 3. **Sublingual** (7-8% of saliva from here) 4. other minor glands (7-8%)
40
What are serous secretions made up of ?
watery iron-rich
41
What are the 2 components that make up a salivary gland?
- secretory acini - ducts
42
What are the 2 types of secretory acini ?
- serous acini - mucous acini
43
Which kind of secretory acini do serous secretions come from ?
serous acini
44
Which kind of secretory acini do mucous secretions come from ?
- mucous acini - serous acini
45
What are the 2 types of saliva secretions ?
- serous secretions (watery) - mucous secretions
46
Which is the largest saliva gland?
parotid gland
47
What type of saliva does the parotid gland mainly secrete?
serous secretions/saliva *watery, iron-rich*
48
Which type of secretory acini are found in the parotid gland ?
serous acinar cells (acini)
49
Which type of acini are found in the submandibular gland ?
- serous acinar cells (acini) - mucous acinar cells (acini)
50
What type of saliva does the submandibular gland secrete?
both: - serous secretions - mucous secretions
51
What type of saliva does the sublingual gland mainly secrete?
mucous secretions
52
Which type of acini are found in the sublingual gland ?
mucous acinar cells (acini)
53
What type of saliva does each gland mainly secrete?
**Parotid** = serous **submandibular** = both serous + mucous **sublingual** = mucous
54
In histology, how can you tell serous acinar cells from mucous acinar cells ?
**mucous** acini = **dont stain well/darkly** due to being full of mucous **serous** acini = **stain well/purple**
55
Roughly how much saliva is secreted each day ?
1 Litre
56
Which inorganic ions are in saliva (in order of highest-lowest conc) ?
1. Na+ 2. HCO3- (bicarbonate) 3. Cl- 4. K+
57
How are inorganic ions and water transported out the acinar cells in a salivary glands ?
- ions leave the acinar cells via **active transport** into the salivary duct - water follows via **osmosis**
58
What are the 2 stages of saliva secretion ?
1. **secretion** = Na, Cl, bicarbonate + water leave the acinar cells into the duct 2. **reabsorption** = NaCl reabsorbed into the duct, saliva leaves hypotonic
59
Is saliva hypertonic, isotonic, or hypotonic ?
**Hypotonic** = ion conc of saliva is lower than plasma
60
Which transport proteins are preset in the basolateral membranes of acinar cells ?
- **Na-K pump** (3Na out, 2K in) - **Na, Cl, K co-transporter** (all 3 in) - **K channel** (K out into blood) - **aquaporins** (H2O in)
61
What kind of junction is found between acinar cells in salivary glands ?
Tight junction
62
Which transport proteins are preset in the apical membranes of acinar cells ?
- **Cl channel** (Cl out into duct) - **aquaporins** (H2O out into duct)
63
Which ion moves into the duct through the tight junctions between acinar cells in a salivary gland ?
**Na+** following the Cl- that makes the duct lumen negative, drawing sodium out
64
Where does modification of primary saliva occur?
Salivary duct cells
65
Which ion transporters are found in the basolateral membrane of the salivary duct cells ?
- **Na-K pump** (3Na out, 2K in) - **Cl- channel** (Cl out into blood) - **Na - H exchanger** (Na in, H out)
66
Which ion transporters are found in the apical membrane of the salivary duct cells ?
- **Na+ channel** (Na into cell) - **Cl- channel** (Cl into cell) - **Cl-HCO3 exchanger** (Cl in, HCO3 out)
67
What enzyme catalyses the formation of bicarbonate within salivary duct cells ?
Carbonic anhydrase
68
How do salivary duct cells differ to acinar cells with regards to water ?
**Acinar cells = permeable** to water via aquaporins **Duct cells = impermeable** to water *this causes the saliva to be hypotonic, as water isn’t reabsorbed*
69
Is primary saliva hypertonic, isotonic or hypotonic ?
**isotonic** and becomes hypotonic as it travels through the duct
70
Is stimulation of saliva secretion primarily sympathetic or parasympathetic?
Parasympathetic stimulation (Ach) *some sympathetic input via NA*
71
What is the process of parasympathetic stimulation for saliva secretion ? (detailed version)
1. **ACh binds to M1 and M3 receptors** 2. activates signalling cascade that 3. results in activated G-protein, and 4. **activates phospholipase C enzyme** 5. this increases inositol triphsophate 6. this **triggers Ca2+ release from endoplasmic reticulum** 7. **Ca2+ activates ion channels** to enable secretion
72
Which parasympathetic neurotransmitter is involved in stimulating saliva secretion ?
Acetylcholine
73
What is the action of Ach in the parasympathetic pathway that ultimately triggers salivation?
**Ach triggers Ca2+ release** from endoplasmic reticulum that **stimulates K+ and Cl- ion channels**
74
Which ion channels does Ca2+ activate in the stimulation pathway of salivation ?
- **K+** channels in basolateral membrane of acinar cells - **Cl-** channels in apical membrane of acinar cells
75
Which sympathetic neurotransmitter is involved in stimulating saliva secretion ?
Noradrenaline
76
How does the sympathetic pathway affect saliva secretion ?
Noradrenaline **increases cAMP** levels which **promotes protein secretion**
77
What is the parasympathetic pathway in stimulating saliva secretion ? (simple version)
- ACh binds to muscarinic receptors on acinar cells - raises intracellular Ca2+ levels - opens ion channels (K+ and Cl-) = ion + water secretion into salivary duct
78
What is the sympathetic pathway in stimulating saliva secretion ? (simple version)
- Noradrenaline binds to beta-adrenoceptors - increases intracellular cAMP - promotes protein secretion (mucins, enzymes etc) = enzyme secretion into the saliva
79
Is saliva acidic or alkaline ? why ?
Alkaline *because bicarbonate raises pH*
80
Which step of saliva production/secretion results in hypotonic saliva ?
**Modification** of saliva in the salivary ducts

Sem 4, case 1 (oesophageal cancer) (6 decks)

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