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Principles of Physiology and Pharmacology > Bililary System, Salvivary, Pancreatic and Gastric Secretions > Flashcards

Bililary System, Salvivary, Pancreatic and Gastric Secretions Flashcards

1
Q

Where is secretin produces and what does it do?

A

Produced by S-cells in the duodenum.

It stimulates liver ductal secretion of bile.

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2
Q

Where is bile stored?

A

In the gallbladder.

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3
Q

Give 2 stimuli which cause the gallbladder to secrete bile into the duodenum.

A
  1. Vagal stimulation - causes gallbladder to contract

2. Cholecystokinin causes gall bladder contraction.

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4
Q

What is cholecystonkinin and where is it produced?

A

Cholecystonkinin is a hormone secreted by cells in the duodenal wall that causes the gallbladder to contract, secreting bile into the duodenum.

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5
Q

What is the composition of bile?

A

Ions: Na+, K+, Ca2+, Cl-, HCO3-
Bile acids
Bilirubin
Phospholipids, cholesterol, proteins

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6
Q

How is bile concentrated in the gallbaldder?

A

Reabsorption of water caused by ion pumps created a crystalloid oncotic pressure.

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7
Q

What is the importance of bile salts?

A

Digestion and absorption of lipids.
Emulsifies fats into lipid droplets (micelles).
Also important as a critical excretory fluid - allows body to dispose of lipid soluble end products of metabolism - the only route to dispose of cholesterol.

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8
Q

Where is bile acid formed?

A

In hepatocytes of the liver

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9
Q

How does bile travel from the liver into the gallbladder?

A

Leaves the liver via the hepatic bile duct into the common bile duct. Then passes up the cystic duct to the gallbladder.

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10
Q

Name the 3 salivary glands.

A

Submandibular
Sublingual glands
Parotid glands

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11
Q

What is the function of saliva?

A

Lubricates food for swallowing and glycoproteins aid starch digestion.
Speech, keeps teeth healthy

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12
Q

What nervous system is responsible for stimulation of the salivary glands?

A

Autonomic
Sympathetic - release of pre-stored amylase
Parasympathetic - fluid secretion and blood flow increase.
Cholinergic, adrenergic and peptidergic stimulation cause salivation.

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13
Q

What is the function of acinar cells of the salivary glands?

A

Produce the primary secretion of saliva.

Primary secretion is isotonic.

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14
Q

What is the function of ductal cells of the salivary gland?

A

Modify the primary secretion by reabsorption of NaCl and secretion of K+ and HCO-. Produces a hypotonic solution called the final secretion.

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15
Q

How does the sympathetic nervous system stimulate acinar cells?

A

Sympathetic nerve releases noradrenaline - activates α1 and β1 adrenergic receptors.
Increases cAMP production and increases intracellular calcium.
Leads to watery protein secretion

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16
Q

What causes the watery secretion?

A

Massive increase in blood flow through microvasculature due to arterial smooth muscle tone relaxation.
Increase in blood flow from 0.5 to 10 ml/g leads to watery secretion.

17
Q

What are gastric pits and what cells are present in them?

A

Entrance to tubular gastric glands (oxyntic gland.

Contains chief cells, parietal cells.

18
Q

What is the function of chief cells in the stomach?

A

Release pepsinogen which is activated in acid to form pepsin.

19
Q

What is the function of parietal cells?

A

Secrete HCl into the stomach.

Secretion is stimulated by gastrin.

20
Q

Where is gastrin produces?

A

In the G-cells of the stomach and duodenum.

21
Q

How is the stomach surface protected from HCl?

A

By a mucus bicarbonate buffer lining secreted by stomach epithelial cells.

22
Q

What is the role of blood flow during gastric secretion?

A

Blood flow increases dramatically during secretion which brings bicarbonate from vasculature to buffer the mucosal surface.

23
Q

Outline the physiological stimulation of gastric acid secretion.

A
  1. Gastrin is released from G-cells in stomach epithelium.
  2. Gastrin binds to CCK 2 receptors of ECL-cell.
  3. ECL-cell releases histamine which binds to receptor on parietal cell.
  4. This trigger HCl secretion from the aprietal cell.
24
Q

How does the negative feedback mechanism control gastric acid secretion?

A

HCl activates D-cells which release somatostatin which binds to G-cells, inhibiting gastrin secretion.

25
Q

Which cell secretes somatostatin and what is its function?

A

D-cells in the stomach.

Somatostatin inhibits further gastrin secretion by G-cells.

26
Q

What does Omeprazole do?

A

Forms disulphide link with H+/K+ ATPase - blocking enzyme irreversibly.
Inhibits gastric HCl secretion.
Therapy for peptide ulcer.

27
Q

What can occur if the mucus layer of the stomach is damage?

A

HCl can destroy epithelium and activate mast cells.
Mast cells secret histamine and damage blood stream epithelium
Causes a peptic ulcer

28
Q

Name the 3 phases of gastric secretion in order.

A

Cephalic phase
Gastric phase
Intestinal phase

29
Q

What occurs during the cephalic phase of gastric secretion?

A

Salivary secretions.
Sight/thought of food or stimulation of taste/smell receptors stimulates the hypothalamus/medulla oblongata. Sends action potential via vagus nerve to stimulate salivary secretion.

30
Q

What occurs during the gastric phase of gastric secretion?

A

Stomach distension activates stretch receptors which acts via local reflexes or via vagovagal reflexes to cause gastric secretion in the stomach

31
Q

What occurs during the intestinal phase of gastric secretion?

A

Presence of low pH and partially digested foods in the duodenum stimulates intestinal gastrin release into the blood stream which stimulates secretory activity.

32
Q

What are the constituents of pancreatic secretion?

A

Rich in HCO3- -neutralises duodenal content.
Proteolytic enzymes - trypsinogen, chymotrypsinogen, procarboxypolypeptidase, ribonuclease, deoxribonucelase.
Amylase and lipase

33
Q

How is pancreatic secretion produced?

A

Active process of ATPase and tritransporter enables accumulation of Cl- in the acinar lumen which creates an NaCl rich fluid.
Na+ can flow though gap junctions along with H2O

34
Q

What is a zymogen granule?

A

Specialised storage organelle in the exocrine pancreas that allows sorting, packaging and regulating apical secretion of digestive enzymes.

Principles of Physiology and Pharmacology (13 decks)

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