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Physiology > 27-29 - The Gut > Flashcards

27-29 - The Gut Flashcards

1
Q

Processing of food involves 5 general processes…

A

1. Motility

2. Secretion

3. Digestion

4. Absorption

5. Excretion

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2
Q

In the stomach, mucus is produced by which type of cell?

A

Surface epitheleal cells

(not goblet cells)

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3
Q

Why must ions, minerals and vitamins be absorbed by active transport in the small intestine?

A

They are charged molecules (therefore cannot cross cell membranes passively)

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4
Q

In the small and large intestines mucus is secreted by which cell type?

A

Goblet cells

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5
Q

Gut function is regulated in three ways…

A
  1. Neurocrine (neural)
  2. Endocrine (hormonal)
  3. Paracrine (local)
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6
Q

Saliva provides 5 properties…

A
  1. Lubrication
  2. Digestion
  3. Solution
  4. Moistness
  5. Protection
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7
Q

Salivary glands are divided into 3 main groups…

A
  1. Parotid
  2. Sublingual and submandibular
  3. Minor glands
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8
Q

Structure of the salivary glands

The acinus is the site of _________

The fluid here is _________

A

Primary secretion

Isotonic (plasma-like)

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9
Q

Structure of the salivary glands

The duct is the site of ________

Sodium and Chloride ions are __________

Potassium and Bicarbonate ions are _________

A

Secondary modification

Reabsorbed

Secreted

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10
Q

After secondary modification in the duct of the salivary glands, the resulting fluid is…

A

Bicarbonate rich and hypotonic

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11
Q

The low H2O permeability of the salivary gland duct makes the fluid more…

A

Concentrated

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12
Q

Control of salivation

Salivation occurs during the _______ phase of digestion

A

Cephalic

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13
Q

Control of salivation

Salivation is increased by activity through parasympathetic nervous system via cranial nerves ___ and ___

Transmission involves the neurotransmitter _________

A

Cranial nerves VII and IX (not the vagus)

Acetylcholine (cholinergic)

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14
Q

Control of salivation

Salivation is reduced through activity of the sympathetic nervous system. The neurotransmitter involved is _________

A

Noradrenaline (noradrenergic)

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15
Q

Name 5 gastric (stomach) functions…

A
  1. Reservior
  2. Mixing food with gastric secretions
  3. Digestion
  4. Controlled gastric emptying
  5. Protection
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16
Q

The main region of the stomach is known as the _____ (or _____ )

At the entrance is the _______ sphinctre

At the exit is the ______ sphinctre

The folds on the lining of the stomach are called _____

A

Body (or corpus)

Esophageal

Pyloric

Rugae

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17
Q

The top part of the stomach is known as the ______

The bottom part of the stomach is known as the _____

A

Fundus

Antrum

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18
Q

The cells found in the gastric glands are (6)…

A

(In order from opening to bottom of the gland)

1. Mucus neck cells

2. Parietal cells

3. ECL (Enterochromaffin-like) cells

4. Chief cells

5. D cells

6. G cells

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19
Q

What do mucous neck cells secrete and what stimulates this secretion?

A

Mucus and bicarbonate

Secretion is tonic (constant at a low level) but increases in response to irritation of the mucosa

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20
Q

Parietal cells secrete gastric acid (HCl) and intrinsic factor.

This is stimulated by both neurocrine (nervous) and paracrine (local) factors, which are…

A
  • Acetylcholine (nervous)
  • Gastrin and histamine (local)
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21
Q

Enterochromaffin-like cells in the gastric mucosa secrete ______ in response to ________ or _______ . This stimulates gastric acid secretion by the parietal cells.

A

Histamine, in response to Acetylecholine or Gastrin

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22
Q

Chief cells secrete ______ and gastric ______.

A

Pepsinogen and Gastric Lipase

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23
Q

When stimulated by stomach acid, D cells secrete _______.

This (inhibits / increases) gastric acid secretion.

A

Somatostatin

Inhibits gastric acid secretion

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24
Q

Intrinsic factors secreted by the parietal cells complex with vitamin ____ to allow its absorption

A

B12

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25
The key enzyme in parietal cells responsible for providing the H+ ions needed to make HCl is \_\_\_\_\_\_\_\_\_\_\_\_
**Carbonic Anhydrase**
26
How does the stomach stop **autodigestion**?
**Mucus acts as a mixing barrier** (some H+ will diffuse through the mucus, but it is neutralised by bicarbonate secreted from the cells)
27
How does omeprazole reduce stomach acidity?
* Omeprazole is a **proton-pump inhibitor** (PPI) * By inhibiting the proton pump on the apical membrane of the parietal cells, H+ ions can no longer move into the lumen of the stomach. * Less H+ = lower acidity
28
Parietal cell function is regulated by both _______ and _______ chemical regulators.
**Direct and indirect**
29
How does cimetidine reduce stomach acidity?
* Cimetidine **competively inhibits** histamine binding to **H2 receptor** * reduces **cAMP**, reducing HCl production
30
Vagus nerve activity (increases / decreases) stomach acid production
**Increases** ## Footnote * G cell gastrin increased * D cell somatostatin, G cell inhibition reduced * ECL cell histamine increased * Direct effect on parietal cells
31
In the small intestine the chyme is comes into contact with (3)...
* **Membrane-bound enzymes** * **Bile** from the liver * **Pancreatic** **enzymes**
32
The primary secretion from the pancreas comes from which cell type?
Acinar cells
33
Duct cells in the pancreas modify the primary secretion by adding ______ , increasing the pH
Duct cells in the pancreas modify the primary secretion by adding HCO3- , increasing the pH
34
The **pancreatic secretion** is ( acidic / neutral / alkaline ) ...
The pancreatic secretion is **alkaline** *to neutralise gastric acid and provide optimal pH for lipase and other intestinal enzymes*
35
Most enzymes are secreted in the form of inactive _________ in order to protect against __________ \_\_\_\_\_\_\_\_\_\_\_.
Most enzymes are secreted in the form of inactive **zymogens** in order to protect against **pancreatic** **autodigestion**.
36
Name 4 classes of enzmes present in the pancreatic secretion (and subtypes)...
* **Amylolytic** * **Proteolytic** (trypsin, chymotripsin, elastase) * **Lipolytic** (lipase, phospholipase) * **Nucleolytic** (DNA & RNA -ases)
37
**Trypsinogen** (an inactive **zymogen**) is converted into the active form **trypsin** by the enzyme...
**Enterokinase**
38
Outline the difference between an **endo** versus **exo** protease...
**Endoproteases** chop proteins in the **middle** ('inside'), **exoproteases** chop the **ends** ('outside')
39
Intestinal peptidases ( begin / continue / finish ) protein breakdown
Intestinal peptidases **finish** protein breakdown
40
**Intestinal peptidases** are involved in protein digestion in the small intestine. They are present both in the **cytosol** (cytosolic) and...
**In the brush-border membrane (membrane-bound)**
41
Which two hormones regulate pancreatic secretion?
* **Secretin** * **CCK**
42
**S cells** release **secretin** when stimulated by...
**Acids**, **lipids**, **bile** **acids** and **hyperosmolarity**
43
**Secretin** increases pH via...
HCO3- rich secretion from the **ductal cells** of the pancreas
44
**Secretin** regulates **pH** and **CCK** regulates...
**Enzyme secretion**
45
**CCK** is released by **I cells** in response to stimulation by...
**Lipids, peptides** and **amino acids**
46
**CCK** causes gall bladder ( relaxation / contraction ) to release bile to ( aid / prevent ) digestion
**CCK** causes gall bladder **contraction** to release bile to **aid** digestion
47
**CCK** stimulates the release of what from the pancreas?
**Digestive enzymes**
48
The effect of CCK on enzyme secretion in humans is... a) direct b) mediated via NA c) mediated via Ach d) mediated via secretin
The effect of CCK on enzyme secretion in humans is... a) direct b) mediated via NA **c) mediated via Ach** d) mediated via secretin * The effect is direct in rats*
49
**Bile** has 2 main functions...
1. **Elimation of waste** (such as lipophilic drugs) 2. **Promotion of digestion and absorption**
50
Like the pancreas, bile ducts secrete fluid rich in...
HCO3-
51
**Hepatocytes** (in the liver) secrete bile into \_\_\_\_\_\_\_\_\_\_\_\_
**Hepatocytes** (in the liver) secrete bile into **canaliculi (bile capillaries)**
52
Bile enters the duodenum via the \_\_\_\_\_\_\_\_\_\_\_\_\_
Bile enters the duodenum via the **common bile duct**
53
When not eating what happens to bile secreted by the liver?
50% is collected in the gall bladder
54
**Bile salts** coat lipids to make...
**Emulsions**
55
What is the main change that **bile** undergoes in the **gall bladder**?
**Concentration** (Gall bladder bile is 20x more concentrated than the isotonic hepatic bile)
56
Describe the 3 steps of bile acid synthesis...
1. **Primary bile acid** is derived from cholesterol 2. **Secondary bile acid** is dehydroxylated by intestinal bacteria 3. Bile acids are conjugated with amino acids to improve solubility -\> **conjugate bile acids**
57
Control of bile acid secretion occurs through 3 mechanisms...
* B**ile-acid dependent** (based on bile acid plasma conc) * **Ductal** * Secretin * **Gall bladder contraction** (integrated w/ *pancreatic enzyme secretion*) * **CCK** * Vagal nerves (**ACh**)
58
Intestinal surface area is enhanced by...
Villi (and microvilli)
59
Dietary **polysaccharides** must be...
Broken down into **monosaccharides** in order to be absorbed
60
Amylase is an **endoenzyme**, which means it can't produce...
**Monosaccharides** (monomers)
61
Glucose (or galactose) is co-transported out of the lumen with...
Sodium (Na+)
62
Name the transporter responsible for the co-transport of sodium and glucose...
**SGLT-1**
63
**SGLT-1** works by a) diffusion b) active transport c) secondary active transport d) facilitated diffusion
**SGLT-1** works by a) diffusion b) active transport **c) secondary active transport** d) facilitated diffusion
64
**Fructose** is absorbed from the intestinal lumen via which transporters?
**GLUT5** and **GLUT2**
65
**GLUT5** transports fructose from the intestinal lumen via...
**Facilitated diffusion**
66
**Gastric pepsin** includes a) endopeptidases b) exopeptidases c) endo and exopeptidases d) pancreatic pepsides
**Gastric pepsin** includes **a) endopeptidases** b) exopeptidases c) endo and exopeptidases d) pancreatic pepsides (endo - cuts in the middle, not the ends)
67
Pancreatic peptidases include both...
Endo and exo peptidases
68
How is the **pH gradient** between the intestinal lumen and the epithelial cells used in the **absorption of peptides**?
Peptides are transported **coupled with H+** (the H+ gradient is maintained by **NHE3** a **sodium/H+ exchanger**)
69
Amino acids are absorbed in the intestine by ( a single / many different types of) transporter.
Amino acids are absorbed in the intestine by **many different types of transporter.**
70
Transport of amino acids across the apical membrane occurs via...
**secondary active transport** by carrier proteins (coupled with ion transport, much like glucose)
71
**Amino acids** pass across the **basolateral** membrane by: a) diffusion b) facilitated diffusion c) active transport d) secondary active transport
**Amino acids** pass across the **basolateral** membrane by: a) diffusion b) **facilitated diffusion** c) active transport d) secondary active transport
72
The main barrier to lipid digestion is their low \_\_\_\_\_\_\_\_\_\_\_\_.
The main barrier to lipid digestion is their low **solubility**.
73
Which process is the function of **bile salts**?
**Solubilisation of lipids**
74
After solubilisation by bile salts, lipids are **digested** via...
**Pancreatic lipase**
75
After digestion, lipids are absorbed... a) passively b) via active transport c) via secondary active transport d) via facilitated diffusion
After digestion, lipids are absorbed... **a) passively** b) via active transport c) via secondary active transport d) via facilitated diffusion
76
Name 3 types of dietary lipid...
Phospholipid, triglycerides and short chain fatty acids
77
After passive absorption, lipids undergo ________________ and exit the cell to maintain the concentration gradient.
After passive absorption, lipids undergo **reesterification** and exit the cell to maintain the concentration gradient.
78
Pancreatic lipase and colipase break down fats into ____________ and ______ \_\_\_\_\_\_\_\_\_ .
Pancreatic lipase and colipase break down fats into **monoglycerides** and **fatty acids**.
79
Lipids are **solubilised** by bile salts in a process called...
**Emulsification** (large droplets (1microM) from stomach are broken into smaller micelles (5nM))
80
Describe the microanatomy of the small intestine (3)...
Finger-like **villi** (which are covered with **microvilli**) and **crypts** between them, which extend down into the mucosa.
81

Physiology (17 decks)

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