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Mpharm 1 > PH1124 - GI system > Flashcards

PH1124 - GI system Flashcards

1
Q

Describe the role of the submandibular glands.

A

The submandibular glands, which are in the floor of the mouth, secrete saliva into the mouth through the submandibular ducts. . The submandibular glands have cells similar to those of the parotid glands, as well as mucus-secreting cells. Therefore, saliva secreted by the submandibular glands also contains amylase but in a liquid thickened with mucus

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2
Q

Describe the role of the sublingual glands

A

• The sublingual glands, which lie below the tongue, use the lesser sublingual ducts to secrete saliva into the oral cavity. The sublingual glands contain mostly mucous cells, and they secrete the thickest saliva with the least amount of salivary amylase.

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3
Q

Describe the role of the parotid glands

A

The parotid glands lie between the skin and the masseter muscle, near the ears. They secrete saliva into the mouth through the parotid duct, which is located near the second upper molar tooth. the parotid glands secrete a watery solution that contains salivary amylase.

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4
Q

describe the role of saliva

A

Saliva is essentially (95.5 percent) water. The remaining 4.5 percent is a complex mixture of ions, glycoproteins, enzymes, growth factors, and waste products. Perhaps the most important ingredient in saliva from the perspective of digestion is the enzyme salivary amylase, which initiates the breakdown of carbohydrates. Food does not spend enough time in the mouth to allow all the carbohydrates to break down, but salivary amylase continues acting until it is inactivated by stomach acids. Bicarbonate and phosphate ions function as chemical buffers, maintaining saliva at a pH between 6.35 and 6.85. Salivary mucus helps lubricate food, facilitating movement in the mouth, bolus formation, and swallowing. Saliva contains immunoglobulin A, which prevents microbes from penetrating the epithelium, and lysozyme, which makes saliva antimicrobial. Saliva also contains epidermal growth factor, which might have given rise to the adage “a mother’s kiss can heal a wound.”

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5
Q

What are the two involuntary stages of the swallowing ?

A

In the pharyngeal phase, stimulation of receptors in the oropharynx sends impulses to the deglutition center (a collection of neurons that controls swallowing) in the medulla oblongata. Impulses are then sent back to the uvula and soft palate, causing them to move upward and close off the nasopharynx. The laryngeal muscles also constrict to prevent aspiration of food into the trachea. At this point, deglutition apnea takes place, which means that breathing ceases for a very brief time. Contractions of the pharyngeal constrictor muscles move the bolus through the oropharynx and laryngopharynx. Relaxation of the upper esophageal sphincter then allows food to enter the esophagus.

Esophageal Phase
The circular muscle layer of the muscularis contracts, pinching the esophageal wall and forcing the bolus forward. At the same time, the longitudinal muscle layer of the muscularis also contracts, shortening this area and pushing out its walls to receive the bolus. In this way, a series of contractions keeps moving food toward the stomach. When the bolus nears the stomach, distention of the esophagus initiates a short reflex relaxation of the lower esophageal sphincter that allows the bolus to pass into the stomach

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6
Q

What are the 5 major GI tract peptide hormones and what do they do ?

A

• Five major GI peptide hormones
• secretin - DECREASE gastric acid secretion
INCREASE bicarbonate from pancreas and bile from liver

• gastrin - INCREASE gastric acid secretion, motility

• cholecystokinin (CCK) -
INCREASE pancreatic juice and bile
DECREASE gastric acid secretion

  • gastric inhibitory peptide (GIP; glucose-dependent insulinotropic peptide) - INCREASE insulin secretion
  • motilin - INCREASE gastric emptying, peristalsis, pepsin
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7
Q

What are the 5 roles of the GI tract?

A
  1. Feeding.
  2. Absorption/Digestion.
  3. Neurohomronal regulations of fedding/appetite.
  4. Distribution.
  5. Elimination.
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8
Q

What is the function of the parotid duct?

A

Watery substance of saliva.

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9
Q

What is the function of the parotid salivary glans?

A

Contains amylase to break down carbs.

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10
Q

What is the function of the Submandibular gland?

A

Mucus secreting cells.

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11
Q

What is the function of the Sublingual salivary glans?

A

Thickens saliva with mucus- little amount of amylases.

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12
Q

What are the 3 parts of the stomach?

A
  1. Fundus
  2. Body
  3. Pylorus
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13
Q

What is the function of the pancreas?

A

Secrete inactive and active forms of digestive pancreatic juices.
Hormonal function

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14
Q

What are 2 inactive forms of pancreatic juices.

A

Trysinogen.

Chymotrypsinogen.

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15
Q

What are three active forms of pancreatic juices?

A

Amylase.
Lipase.
Nucleases.

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16
Q

What is the function of the gall bladder?

A

Concentrates and stores bile produced by the liver.

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17
Q

How are gall stones formed?

A

Imbalance of bile constituents.

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18
Q

What is the function of the liver?

A

Secrete Bile for lipid digestion.
Excretion.
Drug metabolism.
Storage of glycogen, Vitamins and iron.

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19
Q

What is the the function of the spleen?

A

Blood filter

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20
Q

What are the 4 parts of the Small intestine?

A
  1. Duodenum. 2. Jejunum. 3.Ileum. 4. Ileocecal Valve.
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21
Q

What is the function fo the Jejunum?

A

Absorption of food.

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22
Q

What is the function of the Ileocecal Valve?

Where is it located?

A

Function: Restrict movement of fluid in one direction only- limits reflux.
Located: Between small and large intestine.

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23
Q

What are the 4 functions of the colon?

A
  1. Regulation of chyme entry.
  2. Storage of Chyme.
  3. Absorption of water and electrolytes.
  4. Bacterial synthesis of vitamin K.
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24
Q

What is the function of the mouth?

A

Begins carbs and lipid breakdown.
Dissolves food allowing taste.
Some microbial function.

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25
Q

What is the function of the Oesophagus?

A

Propels food to the stomach.

Lubrication.

26
Q

What is the overall function of the stomach?

A

Forms chyme.
Chemical breakdown of proteins and absorbs fat.
Hormone secretion.

27
Q

What is the function of the overall small intestine?

A

Mixes chyme with digestive enzymes.
Absorbs nutrients and water.
Physical digestion.
Optimal medium for enzyme activity.

28
Q

What is the function of the large intestine?

A

Further breakdown of residue. Propels food to the rectum to be eliminated.
Storage before elimination.

29
Q

What are the 4 cells in the gastric pit and gastric gland?

A
  1. Mucous cells. 2. Parietal cells. 3. Chief cells. 4. G cells.
30
Q

Where is gastrin produced?

A

stomach mucosa- G cells of plyionic antrum.

31
Q

What is the function of gastrin?

A

Increase secretion of pepsinogen + HCl. Increases gastric emptying.

32
Q

What is the function of histamine in the GI Tract?

A

increase acid secretion by stimulating pariteal cells to produce HCl.

33
Q

What is the function of serotonin in the GI Tract?

A

Contacts smooth muscle cells.

34
Q

Where are histamine and serotonin produced for use in the GI Tract?

A

Stomach mucosa.

35
Q

What is the function of somatostatin?

A

Restricts all gastric secretions, motility and emptying.

36
Q

What is the myenteric plexus? (Auerbach’s plexus)?

What is its function?

A

Thin layer of muscle whose contractions folds the mucosa.

Function: Movement of food, control smooth muscle.

37
Q

What is the Submucosal Plexus (Meissner’s Plexus)?

What is its function?

A

Submucosa of vessels.

Control of secretions and blood flow.

38
Q

What are the 3 mechanisms that regulate motility and secretions in the GI tract?

A
  1. Endocrine hormones.
  2. Paracrine Mediators (signalling).
  3. Neural transmission.
39
Q

What is the function of Cholecystokinin (CCK)?

A

Increase pancreatic juice and bile and decrease gastric acid secretion.

40
Q

What is the function of GIP?

A

Increase insulin production and inhibits gastric emptying and acid secretion.

41
Q

What is the function of Motilin?

A

Increase gastric emptying, peristalsis and pepsin by stimulating migrating motor complex.

42
Q

Explain the sequence of a paracrine mediator in action.

A
  1. Gastrin released circulates the liver and stimulates endochromaffin cells in the stomach.
  2. Releases paracrine mediators which react on H2 receptors.
  3. Release Acid.
43
Q

Why are neurotransmitters used to release mediators?

A

They can act locally and be released at any time independant of the CNS and volunatry control.

44
Q

List 4 excitatory neurotransmitters used in the GI tract and state their function.

A
  1. ACh- contraction of smooth muscle.
  2. Serotonin- increase gut contraction.
  3. Substance P- increase saliva production and muscle contraction.
  4. CCK- stimulates pancreatic enzyme secretion and gall bladder contraction.
45
Q

List 5 inhibitory neurotransmitters that are used in the GI tract and their function.

A
  1. Enkephalins- moderate smooth muscle activity.
  2. Vasoactive intestinal peptide (VIP)- inhibits gastrin release and acid secretion.
  3. Somatostatin- modulates release of acid, pepsin, gastrin and insulin.
  4. NO- modulated motility.
  5. ATP-modulates motility.
46
Q

What is the function of GLP-1?

A

Stimulation of insulin release and inhibition of glucagon release and gastric function.

47
Q

Explain the 4 stages in the receptive relaxation of the stomach:

A
  1. Stomach relaxes to accommodate the passage of food with minor changes to intro-gastric pressure.
  2. Peristaltic contraction in the mid stomach moves food towards the antrum and +pylorus and some food back into the body of the stomach.
  3. Wave of peristalsis moved to the end and increases intensity- distal antrum contracts intensively.
  4. Chyme passed through pylorus with contraction. Most chyme squirted back into the pylorus by retropulsion.
48
Q

Describe the site of production and action of the endocrine hormone gastrin and the paracrine mediator ECL.

A
  1. Gastrin secreted by the pylorus.
  2. Through the bloodstream to parietal cells.
  3. Stimulate HCl production.
    ECL (enterochromafin-like)
  4. ECL releases histamine.
  5. Histamine stimulates parietal cells to release HCl.
49
Q

What are the 3 steps to generate saliva?

A
  1. Food stimulates receptors using salivary nuclei in the brain stem.
  2. Parasympathetic innervation by glossopharyngeal and facial nerves.
  3. Stimulates salivation.
50
Q

Explain the sequence of action for gastrin secretion.

A
  1. Chemical stimulus on open G cells.
  2. Gastrin released- hormone.
  3. Travels through blood.
  4. Binds to ECL cells.
  5. Triggers proton pump.
  6. Histamine signalled to make more acid.
  7. Results in more acid for breakdown.
51
Q

Explain how the proton pump is used to produce more acid in the stomach.

A
  1. CCK B receptor releases gastrin in the blood where it picks up CO2.
  2. CO2+ H2O —–? HCO3- + H+.
  3. Acid released out of the ATPase pump into gastric lumen to break down food.
  4. Cl- pulled into the pump and HCO3- released.
52
Q

Why does diarrhoea affect the proton pump for the production of acid in the stomach?

A

Due to a lack of electrolytes.

53
Q

What are the 3 distinct phases of secretion regulation?

A
  1. Cephalic Phase.
  2. Gastric Phase.
  3. Intestinal Phase.
54
Q

Explain how the cephalic phase is initiated.

A

Sight, smell, chewing and swallowing.

55
Q

Explain the stages in the cephalic phase.

A
  1. G cells release gastrin.
  2. Gastrin stimulates histamine using ECL cells.
  3. Using the proton pump histamine stimulates partiel cells releasing acid for breakdown.
  4. Gastrin also stimulates chief cells to increase pepsinogen release and prevents breakdown of cells proteins.
56
Q

Explain the stages in the intestinal Phase.

A
  1. Fats + fatty acids stimulate APUD cells increasing CCK and GIP to stimulate parietal cells for acid release.
  2. CCK also used to decrease stomach emptying.
  3. Gastric acid on APUD cells increase secretin release.
57
Q

What are the functions of conjugated bile salts as they are amphipathic?

A
  1. Emulsification and solubilisation of fats.
  2. Transport + absorption of fat soluble vitamins.
  3. Elimination of cholestrol.
58
Q

What makes up sucrose?

A

glucose and fructose

59
Q

What makes up lactose?

A

glucose and galactose

60
Q

What makes up maltose?

A

glucose and glucose

Mpharm 1 (59 decks)

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