PHYL2064 > GIT L2: Upper GIT and disorders > Flashcards

GIT L2: Upper GIT and disorders Flashcards

(54 cards)

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1
Q

When we see food, what reflexes do we activate?

A

Long reflex

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2
Q

What are 2 reasons why it is important to regulate the stomach?

A
  1. If left unregulated –> over production of HCl
  2. Since stomach muscles require a lot of energy, it is inefficient to activate muscles if no food is there and the process does not need to happen (waste energy)
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3
Q

When we see food, _____ (long/short) reflex is activated to produce saliva but we don’t activate any other processes until food is actually eaten (otherwise we waste energy)

A

long

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4
Q

What are the 2 types of cells of the gastric pit?

A
  1. Exocrine cells
  2. Endocrine cells
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5
Q

The body has _____ muscosa, which are important for production of gastric juices

A

oxyntic

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6
Q

What are the 3 types of exocrine cells?

A
  1. Mucous cells
  2. Chief cells
  3. Parietal cells
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7
Q

What are 3 types of endocrine/paracrine cells?

A
  1. Enterochromaffin-like (ECL) cells
  2. G cells
  3. D cells
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8
Q

What is the function of mucous cells?

A

Secret mucous

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9
Q

What is the function of chief cells?

A

secrete pepsinogen & gastric lipase

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10
Q

What is the function of parietal cells?

A

secrete HCl & intrinsic factor (glycoprotein for B12 absorption)

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11
Q

What are 3 reasons why mucous is so important?

A
  1. Protects the gastric wall from the acid (which could burn)
  2. pH2-2.5
  3. Protective cells
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12
Q

What are 3 characteristics of chief cells?

A
  1. Pepsinogen (inactive version of the enzyme pepsin- which is important for digestion of protein)
  2. Gastic lipase –> lipid absorption
  3. Important for absorption of protein and lipids (by producing enzymes)
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13
Q

Why is it important that chief cells produce inactive versions of enzymes (eg. pepsinogen)?

A

So that the stomach will not get “eaten” away and will not get digested (needs to get activated)

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14
Q

What are the 2 characteristics of parietal cells?

A
  1. Intrinsic factors
    • If cells damaged –> cannot absorb B-12 –> Problem –> as B-12 important for production of RBCs
  2. Function of the stomach
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15
Q

What are the 3 benefits of tof having a pH of 2-2.5 in the stomach?

A
  1. Breakdown food
  2. Pepsinogen (inactive enzyme) requires HCl to activate into pepsin
  3. Kills bacteria (which have survived and passed from the mouth into stomach)
    • Very difficult for bacteria to survive in the stomach due to high acidity
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16
Q

The stomach and the small intestine have a lot of stem cells. What are 3 reasons why?

A
  1. Have pH 2-2.5
  2. The stomach is very reliant on specific cells –> the moment any of these cells are damaged ..etc –> wont be able to digest a significant (50%) amount of food that has been ingested. (eg. if chief cells are gone –> all pepsinogen is gone –> no absorption of protein
  3. Sometimes cells need to be replaced
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17
Q

Endocrine/ paracrine cells are important for _____ of food and _____.

A

degeneration; secretion

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18
Q

What are the 2 roles of HCL?

A
  1. Activates pepsinogen (zymogen) - converts it in active pepsin
  2. Contributes to nonspecific disease resistance by destroying most ingested pathogens
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19
Q

Pepsin can also activate pepsinogen. This is called ______

A

autocatalysis

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20
Q

It is important to regulate the system to that it produces the right amount of _____. Why?

A

HCL

Too much will cause too much digestion and too little will cause not enough digestion

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21
Q

HCL cells produced by parietal cells (exocrine cells)- What are the 3 processes of production in regards of movement of Cl from plasma to lumen (passive or active but no ATP) ?

A
  1. Cl comes from the plasma (blood stream)
  2. Goes to the parietal cells (through secondary active transport which is transport against the gradient without using ATP)
  3. Pumped out of parietal cell in a passive diffusion way
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22
Q

HCL cells produced by parietal cells (exocrine cells)- What is a process of production in regards of movement of H from plasma to lumen (passive or active but no ATP) ?

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A

From parietal cell to lumen (need ATP active transport - because pH is so low in the lumen and this would be increasing the concentration gradient)

23
Q

What are 4 characteristics of mucus as a protective barrier?

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A
  1. Impermeable mucosal cells: luminal membranes are impermeable to H+
  2. Tight junctions: prevent HCl from penetrating Will not reach muscularis externa
  3. Mucous coat: physical barrier to HCl
  4. Chemical barrier: HCO3 - neutralizes HCl
24
Q

H+ are pumped up by ______cells..etc but don’t actually touch the _____cells (are impermeable but can still be damaged (that’s why stem cells are commonly present)

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A

parietal; mucosal

25
\_\_\_\_\_\_ is a buffer used to protect the muscosa
HCO3-
26
\_\_\_\_\_\_ is extremely important for the protection of muscosa which is important for the production of \_\_\_\_\_\_.
Mucus; gastric juices
27
What are the 2 ways to regulate gastric secretion?
1. Neural control 2. Hormonal control
28
What is an example of neutral control to regulate gastric secretion?
Acetylcholine (ACh)
29
What are 3 examples of neutral control to regulate gastric secretion?
1. Enterochromaffin-like (ECL) cells 2. G cells 3. D cells
30
What does Acetylcholine (ACh) do?
released by intrinsic nerve plexuses within the stomach, under the control of short local reflexes and vagal stimulation
31
What do Enterochromaffin-like (ECL) cells do?
secrete histamine among the parietal and chief cells (oxyntic mucosa)
32
What do G cells do?
secrete gastrin into the bloodstream
33
What do D cells do?
secrete somatostatin in response to acid
34
What are 13 steps in the regulation of gastric secretion (excitation and inhibition)? **EXAM QUESTION**
1. Stimulation: see/ thought of food (eg. pizza) 2. Increases salivation 3. Activates autonomic NS which releases Ach 4. Ach activates chief cells, parietal cells, ECL cells and G cells (not D cells) 5. System is telling the stomach to get ready because food is coming 6. If just see food, thought of food = no food within 15mins system shuts down (Need a second step for it to actually happen) 7. If food actually reaches oesophagus and stomach --\> G cells (which were originally activated by Ach) get activated by short reflexes of the receptors present in the oesophagus --\> produce gastrin 8. Gastrin is released into the blood stream to activate chief cells, parietal cells and ECL cells. 9. When food reaches the stomach, more HCL is produced by parietal cells 10. Since there is more HCL, histamine is produced 1 11. After a few hours since ingestion and digestion is occurring, need to "shut down" the system(since gastric emptying and mixing is occurring as well) 12. D cells sense change in pH and start to produce somatostatin (opposite effect) 13. Somatostatin shuts down system (mainly acting on parietal cells because need to reduce the amount of acidity HCL )
35
What are the 3 steps in the excitation part of gasrtic secretion regulation? EXAM QUESTION
Step 1: Thinking about food..etc where Ach released and activates chief cells, parietal cells, ECL cells and G cells Step 2: Food reaches the mouth and oesophagus and the G cells produce gastrin and gastrin produces chief cells, parietal cells and ECL cells. Step 3: Histamine is the final drive of production of gastric juices
36
What are the 3 phases in the control and regulation of gastric secretion?
1. Cephalic phase 2. Gastric phase 3. Intestinal phase
37
What is the cephalic phase?
factors arising before food reaches the stomach Long reflexes (food is not in system yet) sight and thought of food increase gastric juices
38
What is the gastric phase?
factors resulting from food in the stomach Short reflexes begins when food is in the stomach (especially proteins). Drives the production of gastric juices the most
39
What is the intestinal phase?
factors in the duodenum after food has left the stomach factor that originates in the small intestine (duodenum). Inhibitory phase, which helps with stomach emptying.
40
What is gastritis?
Breakdown of the mucus barrier can result in inflammation.
41
What are 4 things that cause a chemical breakdown of mucosal barrier?
1. alcohol 2. caffeine 3. aspirin 4. non steroidal anti-inflammatory drugs (NSAIDs such as ibuprofen)
42
Redness (erythema) is caused by excessive production of _____ and gastric juices when no need it. "burn" inside of stomach
HCl
43
What are 2 treatment options for gastritis? (If first stage (gastritis) --\> eg. just when stressed)
1. antacids tablets: neutralize HCl 2. lifestyle changes: avoid aggravating food (spicy food, coffee, chocolate, mint and tomato).
44
What are peptic ulcers?
Extreme gastritis or bacterial infection increase the chance of developing peptic ulcers. Open wound which is infected --\> extremely painful (when you eat/drive or drive production of HCL)
45
\_\_\_\_\_\_ (excitation/inhibition) will ALWAYS prevail over ____ (excitation/inhibition) (inhibition is stronger than excitation). Why?
Inhibition; excitation 3 steps/cell types to activate the system (ACh, Gastrin, Histamine) Only 1 cell type to completely shut down the system (Somatostatin)
46
What is the bacterial infection in peptic ulcers?
Colonise antrum (which has a very small amount of parietal cells = less acidic than other parts) --\> learnt to produce urea (ammonia) to balance/buffer the acidic environment
47
What does Helicobacter pylori (acid-resistant bacteria) look like?
* Flagella * Prefer to settle in the antrum (no parietal cells) * Production of urease to buffer HCl
48
What are 2 diagnostic tests for peptic ulcers?
1. urea breath test (UBT) 2. if positive endoscopy to check for ulcers
49
Why is a urea breath test (UBT) done in peptide ulcers?
Bacteria has ammonia so drives a strong ammonia smell
50
What are 4 treatments options for peptic ulcers?
1. antibiotics (2 weeks) 2. proton pump inhibitors (action on H+-K+ ATPase pump) 3. blocker for histamine receptor 2 (H2) (cimetidine): inhibits production of HCl, no effect on H1 receptors (involved in allergic respiration disorders) * For extreme cases 4. lifestyle changes
51
What is pernicious anemia?
Defective erythrocyte production
52
What happens in pernicious anemia?
Autoimmune disease that affects the parietal cells. Absence of intrinsic factors (glycoprotein) release by parietal cells. Impossibility of the body to absorb enough vitamin B12 in ileum Defective erythrocyte production
53
What is a treatment for pernicious anemia?
Regular injections of vitamin B12
54
What are the 2 functions of parietal cells?
1. HCL 2. Intrinsic factor * B12 absorption
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