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Short Term Care > Physiology Of GI Tract > Flashcards

Physiology Of GI Tract Flashcards

1
Q

How does the GI tract repel foreign invaders and why does it need to ?

A

The GI tract is the largest area of contact between the internal environnement and the outside world.
It possess the largest collection of lymphoid tissue in the body : 80% of the total.

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2
Q

What are the 4 basic process of the GI tract ?

A

Digestion : chemical and mechanical breakdown of food
Absorption : active or passive transfer of substance from the lumen to the extracellular fluid (ECF)
Motility : movement of material resulting from muscle contraction
Secretion : transfer of water and ions from the ECF to the lumen

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3
Q

What are carbohydrates ?

A

They are polymer of monosaccharide like glucose. They are classified in 2 categories : complex carb (‘good’, high in fibres and low glycemic index) and simple carb (‘bad’, low in fibres and nutrients with a high glycemic index).

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4
Q

What are fats and proteins ?

A

Fats comprise lipids and cholesterol.
Proteins are polymers of amino acid.

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5
Q

Where are the carbohydrates digested and by who ?

A

In the mouth by the alpha amylase in saliva.
In the stomach by alpha amylase until the pH fall below 4-5
In the intestinal lumen by pancreatic alpha amylase.

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6
Q

How are the carbohydrates absorbed ?

A

It is absorbed by the cells via sodium glucose transporters.

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7
Q

Where are the fats digested ?

A

In the stomach by lipase and in the intestinal lumen in severals step.

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8
Q

What are the different digestion of fat in the intestinal lumen ?

A

Emulsification of (triacylglycerol) neutral fat : by bile acid
Hydrolysis of neutral fat : by pancreatic lipase
Hydrolysis of phospholipids : by pancreatic phospholipase
Hydrolysis of cholesterol : by pancreatic cholesterol-esterase

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9
Q

What are the function of cholesterol ?

A

It is used to create different hormones in function of which enzyme is breaking it.

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10
Q

Where do fats go after absorption ?

A

Fatty acid go into the lymphatic system. Short chain fatty acid go into the portal vein then to the liver.

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11
Q

Where and by who are proteins digested ?

A

In the stomach by pepsin.
In the intestine by chymotrypsin, trypsin (both produced by the pancreas) and amino-polypeptidase (produced by the microvili)

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12
Q

What is it important to digested protein even though the body can produce them ?

A

Because there are 9 essential amino acid that the body cannot produce.

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13
Q

What is a syncytium ? Why is it possible in the gut ?

A

It is when an action potential is elicited anywhere within the muscle mass and travels in all direction.
It is possible in the gut because the bundle of muscle fibres are separated by loose connective tissue but fuse often with each other and that within the bundles the fibres are connected through large gap junction allowing for a low resistance so the signal can travel faster.

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14
Q

What are the 2 muscles layer of the gut ?

A

Longitudinal muscle layer : extend down the intestinal tract - outer
Circular muscle layer : extend around the gut - inner

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15
Q

What is the enteric nervous system ?

A

The nervous system dedicated to the GI tract. It is composed by more than 100 million neurons (more than the spinal cord neurons). Even if it can work on its own the GI tract still receive signals from the parasympathetic and sympathetic nervous system.

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16
Q

What are the 2 plexus of the enteric nervous system ?

A

The outer plexus situated between the longitudinal and circular muscle layer : myenteric or Auerbach’s plexus.
The inner plexus situated in the submucosa : submucosal or Meissner’s plexus.

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17
Q

What are the main neurotransmetteurs of the enteric nervous system ?

A

Acetylcholine : executes GI tract activity
Noradrenaline and adrenaline : inhibit GI tract activity

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18
Q

What is colostomy ?

A

Attaching a colon with a stoma which is a bag attached to the sin that store excrement.

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19
Q

What are type A and B chronic gastritis ?

A

Type A : immune system attacking the stomach cells.
Type B : bacteria H. Pylori causing ulcers in the stomach wall.

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20
Q

What is the most effective way to evaluate the upper GI tract ?

A

Do an endoscopy.

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21
Q

What area oesophageal varices ?

A

Enlarged veins around the oesophagus.

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22
Q

What can be compressed between the superior mesentery artery and the aorta ?

A

Also called the nutcracker syndrome, they squeeze the left renal vein.

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23
Q

What does the myenteric plexus do ?

A

Control muscle activity along the gut.
Like increasing tonic contraction, the intensity of the rhythms contraction, the rate of rhythms contraction and the velocity of the conduction.
It also inhibit the pyloric sphincter and the ileocecal valve.

24
Q

What does the submucosal plexus do ?

A

It control the GI tract secretion and local blood flow, it also receives sensory signals to help control local absorption and contraction.

25
Q

Where are the part of the autonomic nervous system located ?

A

The parasympathetic system : cranial nerve fibers are in the vagus nerve and innervate the oesophagus, stomach, pancreas, part of the large intestine and sacral nerve fibres pass through pelvic nerve and innervate the large intestine and anus.

The sympathetic nervous system : principally in the oral cavity and anus.

26
Q

What does the sympathetic nervous system do in the GI tract ?

A

It secrete noradrenaline to inhibit intestinal smooth muscle and inhibit the entire enteric system.

27
Q

What stimulate the afférent sensory nerve fibres in the gut ?

A

An irritation of the gut, an excessive gut distension presence of specific chemicals.

28
Q

What type of reflexes are integrated into the wall of the enteric nervous system ?

A

The control of secretion, peristalsis, mixing contraction, local inhibitory effect.

29
Q

What type of reflexes pass by the sympathetic nervous system.

A

They are sensed in the gut, go though the sympathetic nerves fibres then back to the GI tract.
Gastronomic reflex, enterogastric reflexes, colonoileal reflex.

30
Q

What reflexes pass by the spinal cord ?

A

They are sensed in the gut, go though the spinal nerves and back to the GI tract.
Stomach/duodenum : to control gastric motor and secretory activity
Pain reflexes : cause a general inhibition
Defecation reflexes : cause abdominal contraction

31
Q

What are the main hormones of the GI tract ?

A

Gastrin, Cholecystokinin, secretin, gastric inhibitory peptide, motilin.

32
Q

Where and why is gastrin secreted ?

A

In the G-cell of the antrum (next to the pylorus) of the stomach, in response to the distension of the stomach or odor, taste, thinking of food.

33
Q

What does gastrin do ?

A

It stimulate gastric acid release and mucosal growth by activating the parietal cell that release H+ to produce HCl.

34
Q

Where and why is cholecystokinin secreted ?

A

By the I cell of the small intestine in response to the presence of fatty acid and mono-glycerin in the intestinal content.

35
Q

What does cholecystokinin stimulate ?

A

The secretion of pancreatic enzyme. The contraction of the gallbladder to release bile to emulsify fatty acid. The growth of exocrine pancreas.

36
Q

What does cholecystokinin inhibit ?

A

Gastric emptying to give adequate time for digestion. Appetite to prevent overeating.

37
Q

Where and why is secretin secreted ?

A

In the S cells of the small intestine in response to gastric juice in the duodenum.

38
Q

What does secretin stimulate ?

A

The secretion of pepsin, pancreatic bicarbonate and biliary carbonate to neutralise acid. The growth of exocrine pancreas.

39
Q

What does secretin inhibit ?

A

Gastrin release to reduce gastric secretion.

40
Q

Where and why is motilin secreted ?

A

In the M cells of the duodenum and jejunum in response to fasting.

41
Q

What does motilin do ?

A

It stimulates the gastric and intestinal motility

42
Q

Where and why is gastric inhibitory peptide secreted ?

A

In the K cells of the duodenum and jejunum in response to the presence of fatty acid and amino acid.

43
Q

What does gastric inhibitory peptide do ?

A

It stimulates insulin release and inhibits gastric secretion.

44
Q

What is peristalsis ?

A

Propulsive movement allowing the food to move forward at an appropriate rate to accommodate digestion and absorption. It looks like a contractile ring in the circular muscle, spreading along the tube gut.

45
Q

What stimulate peristalsis ?

A

It is stimulated by the stretching of the gut wall (because of the amount of food) or by chemical and physical irritation.

46
Q

What happen to peristalsis if the myenteric plexus is not functionally active ?

A

If it if depressed, absent or blocked then the peristalsis will be weak.
It must be polarised in the right direction toward the anus to avoid backward movement.

47
Q

What is segmental contraction ?

A

Keep intestinal content mixed together. It differ in various part of the GI tract.

48
Q

What is the Splanchnic circulation ?

A

The blood flow of the gut, spleen, pancreas and liver. It flows through the liver with the portal veins using the liver sinusoids and lease using the hepatic vein that empty into the vena cava.

49
Q

How is the Splanchnic circulation related to the activity of the gut ?

A

Vasodilator substances can be released during the digestive process to increase blood flow.
Decreased oxygen in the cells will increase the blood flow too.

50
Q

What is the function of the mouth, which enzyme are present ?

A

It chew to break down nutrient in small bit. With the help of the enzyme produced by the saliva glands : amylase and lipase.

51
Q

What is the LES and what’s its function ?

A

The lower oesophageal sphincter, a valve located between the oesophagus and the stomach. It prevents food from leaking up and causing heartburn.

52
Q

What is the chyme of the stomach ?

A

The liquids nutrients leaving the stomach through the pyloric sphincter.

53
Q

From where comes the enzyme of the duodenum ?

A

From the liver (bile) stored in the gallbladder. From the pancreas.

54
Q

What are the substances produced by the pancreas ?

A

Pancreatic amylase, pancreatic lipase, trypsin (proteins) and chymotrypsin (proteins).

55
Q

What is the point of the vili , what are they made of ?

A

They increase the surface of absorption for nutrients. On their surface are microvili made of enterocyte.

The central lacteal, part of the lymphatic system, is continuous in every vili. It absorb nutrient (then the capillaries around the central lacteal absorbed them) and fats (they stay in the lymphatic system).

56
Q

What are the main type of cell in the pancreas ?

A

The acinar cells that produce enzyme. The centroacinar cells that produce HCO3- and the duct cells and exchange HCO3- and Cl-.

Short Term Care (10 decks)

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