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Gastrointestinal > Physiology and Pharmacology of Salivary and Gastric Secretion and Gastric Motility > Flashcards

Physiology and Pharmacology of Salivary and Gastric Secretion and Gastric Motility Flashcards

(75 cards)

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1
Q

Name the three pairs of salivary glands in the head

A

Parotid
Submandibular
Sublingual

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2
Q

What are the functions of saliva?

A

Lubrication (important for speech and swallowing)
Solvent (taste)
Antibacterial
Digestion of complex carbohydrate (amylase)
Neutralization of acid (bicarbonate)
Facilitates sucking by infants (fluid seal)

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3
Q

Name some of the constiuents of saliva

A

Lysozyme, lactoferrin, immunoglobulins, amylase and bicarbonate

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4
Q

What are the two stages of saliva formation?

A

Primary secretion and secondary modification

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5
Q

Where does the primary secretion take place?

A

Acinus

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6
Q

What does the primary secretion contain?

A

Na+, K+, Cl-, HCO3-, mucus and amylase

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7
Q

Where does secondary modification of saliva take place?

A

Duct cells

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8
Q

How is saliva modified?

A

Na+ and Cl- is removed, K+ and HCO3- is added, there is no movement of water (dilution)

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9
Q

Where does the dilution of saliva take place?

A

As it passes through the duct cells

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10
Q

What aspect of saliva composition allows the detection of salty taste?

A

NaCl content is much lower than plasma

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11
Q

What aspect of saliva allows the detection of sweet taste?

A

No glucose

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12
Q

What two reflexes increase the rate of saliva formation?

A

Simple reflex

Conditioned reflex

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13
Q

What is the simple relex?

A

Chemo or pressure receptors in the mouth are activated in the presence of food or other stimulus
Impulses are sent via afferent nerves to salivary centre in the medulla

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14
Q

What is the conditioned reflex?

A

Think about, smell, see, hear preparation of food

Cerebral cortex sends messages to the salivary centre in the medulla

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15
Q

What happens once signals have reached the salivary centre in the medulla?

A

Impulses are sent via extrinsic autonomic nerves

(sympathetic and parasympathetic stimulation) to the salivary glands, which then increase production

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16
Q

Does sympathetic or parasympathetic stimulation have a more dominant role in saliva production?

A

Parasympathetic

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17
Q

What nerves are involved in the parasympathetic stimulation for saliva production?

A

Glossopharyngeal and facial nerves

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18
Q

What type of saliva does parasympathetic stimulation result in?

A

Large volume, watery, enzyme rich

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19
Q

What receptors are involved in the parasympathetic stimulation?

A

M3 muscarinic acetlycholine receptors

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20
Q

When is the sympathetic stimulation of salivary glands present?

A

During stressful situations

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21
Q

What nerve fibers are involved in sympathetic stimulation?

A

Postganglionic fibres from superior cervical ganglia

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22
Q

What type of saliva results from sympathetic stimulation?

A

Small volume, thick, mucus rich

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23
Q

What receptors are involved in sympathetic stimulation?

A

B1-adrenoceptors

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24
Q

What are the names of the different parts of the stomach?

A

Fundus
Body
Antrum

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25
What are the functions of the stomach?
Starting point for protein digestion Mixes food with gastric secretions to produce chyme Limited amount of absorption Stores food before passing it into the small intestine as chyme for further digestion and absorption
26
How is the food emptied from the stomach?
Waves of peristaltic contraction push the food | The strength of antral waves determine the escape of chyme through the pyloric sphincter
27
What factors govern the strength of the antral waves?
Gastric and duodenal factors
28
What are the gastric factors that influence stomach emptying?
The rate of emptying is proportional to the volume of chyme in the stomach Distension increases motility
29
How can the duodenum delay gastric emptying through neural response?
Enterogastric reflex - | Signals from intrinsic nerve plexuses and autonomic nervous system decrease antral peristalic activity
30
How can the duodenum delay gastric emptying through hormonal response?
Release of enterogastrones from the duodenum inhibits stomach contraction
31
What stimuli within the duodenum drive the neuronal and hormone responses?
Fat Acid Hypertonicity Distension
32
What is the name of the neck of the gastric glands?
Gastric pIt
33
Where do the gastric glands lie?
In the mucosa
34
Name the 2 different cell types in the gastric glands in the pyloric gland area
D cell | G cell
35
What do each of the cells secrete?
D cells - somatostatin | G cells - gastrin
36
Where is the pyloric gland area?
The antrum
37
Name the 3 different cell types in the gastric glands in the oxyntic mucosa
Chief cell Enterochromaffin-like cell Parietal cell
38
What do each of the cells secrete?
Chief cells - pepsinogen Enterochromaffin-like cells - histamine Parietal cells - hydrochloric acid and intrinsic factor
39
Where is the oxyntic mucosa?
The fundus and body
40
In the pyloric gland area, what is the function of gastrin?
Stimulates HCl secretion
41
n the pyloric gland area, what is the function of somatostatin?
Inhibits HCl secretion
42
n the pyloric gland area, what is the function of mucus?
Protective
43
In the oxyntic mucosa what is the function of HCl?
Activates pepsinogen to pepsin Denatures proteins Kills most micro-organisms ingested with food
44
In the oxyntic mucosa what is the function of pepsinogen?
Inactive precursor of the peptidase, pepsin
45
In the oxyntic mucosa what is the function of instrinsic factor?
Binds vitamin B12 allowing absorption in terminal ileum
46
Explain the autocatalytic effect of pepsin
HCl converts pepsinogen to pepsin. Pepsin then activates pepsinogen
47
What are the three stages of gastric secretion?
Cephalic Gastric Intestinal
48
When is the cephalic phase of gastric secretion?
Before food reaches the stomach
49
When is the gastric phase of gastric secretion?
When food is in then stomach
50
When is intestinal stage of gastric secretion?
After food has left the stomach
51
What is the function of the cephalic stage of gastric secretion?
It prepares the stomach to receive food
52
What two neurotransmitters are involved in vagal stimulation of the enteric nervous system?
Acetylcholine | Gastrin releasing peptide
53
What is the gastric stage of gastric secretion?
Chemical and mechanical factors augment secretion
54
What is the intestinal phase of secretion?
Factors originating from the small intestine switch off acid secretion
55
What happens to stimulation of somatostatin when the stomach is full?
It is inhibited
56
What are the drug classes that influence acid secretion?
Muscarinoc receptor antagonists Proton-pump inhibitors Non-steriodal anti-inflammatory drugs H2 histamine receptor antsgonists
57
How do muscarinic receptor antagonists influence acid secretion?
They competively block the M1 and M3 receptors meaning that AcH doesn't have an affect
58
Give an example of a muscarinic receptor antagonist
Pirenzepine
59
How do proton-pump inhibitors work?
They block the H+/K+- dependent proton pump of cells by covalent modification They are delivered via the systemic circulation
60
What is an example pf a proton pump inhibitor?
Omaprazole
61
How do NSAIDs work?
They block reversibility
62
Give an example of an NSAID
Aspirin
63
How do histamine receptor antagonists work?
They competitively block the histamine receptor reducing acid secretion
64
Give an example of a H2 histamine receptor antagonist
Ranitidine
65
What protects the mucosa from attack by HCI and pepsin?
A thick mucus gel layer above the apical surface of the mucosa cell
66
What is released into the muscus layer to neutrilise it?
Bicarbonate
67
What is a peptic ulcer?
An ulcer in an area where the mucosa is exposed to hydrocholric acid and pepsin
68
How can NSAIDs cause gastric ulcers or bleeding
They reduce prostaglandin formation
69
How can gastric ulcer formation from long term use of NSAIDs be prevented?
Stable PGE1 analogue e.g. misoprostol
70
Chronic infection of the gastric antrum from what bacteria causes development of peptic ulcers?
Helicobacter pylori
71
How does infection from helicobacter pylori result in the formation of peptic ulcers?
The bacteria hide in the mucus layer and secrete agents that cause persistent inflammation that weakens to mucosal barrier. the breakdown of the mucosal barrier damages the mucosal cell layer and leaves the submucosa subject to attack by HCl and pepsin
72
How does peptic ulcer treatment aim to promote healing?
Inhibit acid secretion Increase muscosal resistance Eradicate Helicobacter pylori
73
What conditions are drugs that reduce acid secretion used in the treatment of?
Peptic ulcers Gastro-oesophageal reflux disease Acid hypersecretion e.g. Zollinger-Ellisonn syndrome Cushing's ulcers
74
Give two examples of mucosal strengtheners
sucralfate | Bismuth chealate
75
How does sucralfate work?
Requires an acidic environment for activation Binds to the ulcer base and forms complex gels with mucus, providing a mucosal barrier against acid and pepsin Increases mucosal blood flow, mucus, bicarbonate and prostaglandin production

Gastrointestinal (11 decks)

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