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PHGY 1030- EXAM 6 > Physiology of Digestive system April 6 > Flashcards

Physiology of Digestive system April 6 Flashcards

1
Q

What is the bulk of the pancreas composed of?

A
  • Pancreatic exocrine cells and their associated ducts
  • Islet of Langerhans which are the endocrine cells of the pancreas and secrete insulin , glucagon and several other hormones
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2
Q

What is the Pancreatic juice composed of ?

A

Two secretory products critical to proper digestion:
- Digestive enzyme
- Bicarbonate

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3
Q

What are three major groups of digestive enzymes that are critical to efficient digestion?

A
  1. Proteases :
    -This includes two major kinds in trypsin and chymotrypsin which are synthesized and packaged into secretory vesicles . The inactive forms are called trypsinogen and chymotrypsinogen
  2. Pancreatic lipase :
    -Important for digestion of triglyceride to break down into 2-monoglyceride and two free fatty acids.
  3. Amylase :
    - Hydrolyses starch to maltose as well as trisaccharide
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4
Q

What is the importance of bicarbonate in the pancreas and where does it come from ?

A
  • Epithelial cells in pancreatic ducts are the source of bicarbonate
  • bicarbonate is the base and critical to neutralizing the acid coming into the small intestine from the stomach
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5
Q

What is the first step of exocrine function in digestion?

A
  1. Neutralize Acid so pancreatic enzymes can work
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6
Q

What is the second step of exocrine function in digestion?

A
  1. Digestion Pancreatic Enzymes into intestinal lumen from pancreatic acinar cells

carbs:
- poly saccharides are broken up by pancreatic amylase into disaccharides (maltose)

Proteins:
First trypsinogen gets activate by enteropeptidase into trypsin
Then trypsin helps to activate multiple other enzymes like:
Trypsinogen –>Trypsin
Chymotrypsinogen–>Chymotrypsin
Procarboxypeptidase–>carboxypeptidase
Lastly dietary secretd proteins uses proteases to form peptides and AAs

Fats(lipids):
Pancreatic lipase is used to digest fat it helps to break down triglyceride into Fatty acids and monoglycerides

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7
Q

What are some examples of enzymes that will help on the intestinal wall to complete digestion of carbs and proteins?

A
  • Disaccharidases
  • Enterokinases
  • Aminopeptidases
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8
Q

Why is Amylase secreted in an active form instead of inactive like other enzymes ?

A
  • Because active amylase does not endanger the secretary cells
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9
Q

during digestion, the intestinal wall enzymes break carbohydrates further and what are some examples and the enzymes involved?

A
  1. Sucrose –>glucose +fructose . This happens with the help of Sucrase
  2. Maltose–>glucose + glucose . This happens with the help of Maltase
  3. Lactose –> glucose + galactose . This happens with the help of Lactase
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10
Q

What can lactase deficiency cause?

A
  • It can cause lactose intolerance because you have no lactase to help break down the lactose and it can cause diarrhea and cramping
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11
Q

What effect does intestinal wall enzymes have on protein and lipids?

A
  • Proteins(peptides):
    -peptides–>smaller peptides + amino acids . this is done with the help of aminopeptidases(enzyme)
  • Lipids(fats)
    -no digestion as there is no lipase on intestinal wall
    -fat is already fully digested in the small intestine lumen by pancreatic lipase so no further breakdown occurs
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12
Q

How does calcium absorption in the intestinal lumen change if there are low calcium levels?
What is the rate limiting step in this case?

A
  • Active absorption happens but in the duodenum only . So essentially calcium is imported into the enterocyte through a voltage insensitive (TRP) channel and is pumped out of the cell via a calcium ATPase
  • Rate limiting step is the transport across the epithelial cell and it is enhanced by calbindin which is made from vitamin D
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13
Q

How does calcium absorption change when there are high calcium levels?

A
  • Passive absorption happens but only in the jejunum and ileum and to a much lesser extent, the colon . This is done by calcium diffusion through tight junctions into basolateral spaces around enterocytes and hence into the blood
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14
Q

Where is iron absorbed and what is required for there to be efficient absorption and what can interfere with iron absorption?

A
  • absorbed in the proximal duodenum
  • Efficient absorption requires an acidic environment
  • Antacids or other conditions that interfere with gastric acid secretion can interfere with iron absorption
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15
Q

What happens if there is high iron availability?

A
  • Iron is trapped in ferritin and not transported into the blood and when the enterocyte dies , the iron dies
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16
Q

What happens if there is low iron availability?

A
  • Iron is exported out of the enterocyte by ferroportin located in the basolateral membrane and it then binds to the iron carrier transferrin for transport throughout the body
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17
Q

How much of the things presented to the small intestine Is actually absorbed and which section of the intestine does most of it occur in ?

A
  • Absorbs almost everything presented to it
  • Most occurs in duodenum and jejunum
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18
Q

What can cause Malabsorption in the intestine ?

A
  • May be caused by damage to or reduction of the surface are of the small intestine
19
Q

What do the absorption of the digestion end products of both carbs and proteins involve and where are they absorbed into?

A
  • They involve the carrier mediated secondary active transport mechanisms
  • Absorbed into the blood
20
Q

How much water is absorbed intro the small intestine daily and how much is lost to the large intestine ?

A
  • 8500ml/day absorbed in small intestine
  • 500 ml/day absorbed in large intestine
21
Q

Where do the absorbed nutrients go ?

A
  • To liver via hepatic portal vein (blood)
  • Into lacteals (lymph) –>Thoracic duct->left subclavian vein
22
Q

Where is bile required from during fat digestion and absorption ?

A
  • Liver (synthesizes)
  • gall bladder (stores)
23
Q

What is the only liver function that is not accomplished by the hepatocytes ?

A
  • Kupffer cells are macrophages which remove bacteria and worn out red blood cells
24
Q

What does bile consists of and where does bile go after a meal?

A
  • Consists of:
    -Bile salts
    -Cholesterol
    -Lecithin
    -Bilirubin
    -detoxified / inactivated drugs
    -toxins
    -hormones in an aqueous alkaline fluid
  • Bile enters duodenum after meals
25
Q

What is the function of bile salts ?

A
  • Emulsification :
    -breaks up larger globules of fat into many small droplets
  • Micelle formation :
    -This is when bile salts and lecithin aggregate in small clusters with their fat soluble parts huddled together in the middle to form a hydrophobic core while their water soluble parts form an outer hydrophilic shell
26
Q

In the micelle formation, what happens when there is excessive secretion of cholesterol ?

A
  • It starts to precipitate into micro crystals that aggregate into gallstones, these are 75% derived from cholesterol and 25% from bilirubin
27
Q

What gives bile and urine its yellow color?

A
  • Bilirubin
28
Q

Can you still survive without the gall bladder and what would happen when gall bladder is removed from the body?

A
  • Yes you can survive without the gall bladder
  • The common bile duct dilates taking over the role of storage
29
Q

When the content first comes into the large intestine from the small intestine what does it consist of ?

A
  • Indigestible food residues
  • Unabsorbed biliary components
  • remaining fluids
30
Q

What controls the juncture between the ileum and large intestine?

A

There is a ileocecal valve which is surrounded by thickened smooth muscle, the ileocecal sphincter

31
Q

What controls the juncture between the ileum and large intestine?

A

There is a ileocecal valve which is surrounded by thickened smooth muscle, the ileocecal sphincter

32
Q

How does the ileocecal valve and sphincter controlled ? why is it important for a sphincter to be there between the small and large intestine?

A
  • The valve and sphincter opens allow content to flow through into large intestine in response to pressure on the ileal side of the valve and to the hormone gastrin secreted.
  • It is important because without it the toxins would travel back to small intestine harming the nutrient absorbed
33
Q

What are Haustral contractions in the large intestine and what does the movement of material allow for ?

A
  • These are slow and weak contractions initiated by autonomous rhythmicity of colonic smooth muscle cells
  • These move material down tube: allow mixing, absorption of salts and H2O.
34
Q

What are Mass Movements in the Large Intestine?

A
  • These are massive contractions mediated from stomach to colon by gastrin and by autonomic nerves.
35
Q

What is a gastrocolic reflex?

A
  • It is when there is food in the stomach and there are powerful waves of contractions from transverse colon to rectum and this is most evident after first meal of the day
36
Q

What effects does gastrin, secretin and CCK have on the stomach and duodenum ?

A
  • Gastrin:
    • Increase in acid and gastric enzyme secretion
  • Secretin:
    • Increase in alkaline fluid secretion
    • Decrease in gastric secretion
  • CCK:
    • Increase in pancreatic enzyme secretion
    • Increase in contraction of gallbladder
    • Decrease in gastric motility and secretion
37
Q

What is glucose used for in cells?

A
  • Catabolism by cells –> ATP
  • Anabolism –> glycogen
38
Q

What is lipids used for in the body?

A
  • Cholesterol used to make steroid hormones, bile salts and cell membrane
  • Triglyceride in blood
39
Q

What is amino acids used for in the body and what happens to the excess amount ?

A
  • AA mainly used for protein synthesis
  • Can also be used for energy when glucose is low
  • Excess is not stored, it is converted to fat
40
Q

How does the Rectal (defection) reflex work?

A
  • It is stimulated by the faces in rectum and it sends a signal to the sacral segment of spinal cord (PSNS) in the CNS and then a signal is send to the effector which causes smooth muscle of rectum to contract and internal anal sphincter relaxes
41
Q

What happens during Nausea?

A
  • Sensation immediately before vomiting
  • Cold , sweat. pallor , salivation
  • Loss of gastric tone
  • Reflux of intestinal content into the stomach
42
Q

What happens during retching ?

A
  • No expulsion of gastric content , no vomiting
  • it builds pressure gradient leading to vomiting
43
Q

What is vomiting caused by ?

A
  • Caused by sustained contraction of the abdomen and chest muscle

PHGY 1030- EXAM 6 (7 decks)

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