Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ZOOL463 > GI Tract > Flashcards

GI Tract Flashcards

1
Q

What is the biggest challenge of digestion?

A

Food molecules being too large to absorb and transport! They have to be broken down.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the simple molecules that food gets broken down into?

A

Fatty acids (fats), amino acids (proteins), monosaccharides (polysaccharides).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the four basic processes of the digestive system?

A

Motility, secretion, digestion, absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does most of the digestion take place? Absorption?

A

In the stomach for proteins and in the small intestine for everything else. The small intestine is where most absorption takes place.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the difference between glycogen stored in the liver and glycogen stored in muscle?

A

Muscle glycogen is used for work, glycogen in the liver can be mobilized quickly and broken down anaerobically for use for exercise.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are some challenges to the GI tract?

A

Autodigestion and dehydration from diarrhea.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What role do hormones play in the GI tract?

A

They play a role in gut function and cellular metabolism. They act as checkpoints in digestion that regulate storage as needed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does the digestive system act as a defense against foreign invaders?

A

Mucus as a barrier, enzymes to destroy foreign cells, acid, lymphoid tissue (gut associated lymphoid tissue GALT)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where can you find 80% of immunoglobulin producing cells?

A

The small intestine. They produce T-cells, B-cells, and antibodies.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What enzyme is absolutely crucial for protein digestion?

A

Pepsin - the activated form of pepsinogen which is cleaved by hydrochloric acid in the stomach.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the regions of the GI tract?

A

Mouth, pharynx, esophagus: mechanical breakdown
Stomach: acidic
Upper/small intestine: digestion and absorption, most of both
Lower/large intestine: water absorption
Anus: release indigestible material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the major regions of the stomach?

A

The fundus, the body and the antrum. The fundus acts as acid storage, the body is where most digestion occurs, and the antrum is where semi-digested solids sit as chyme (bolus + gastric juice) before being excreted by the pyloric sphincter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the functions of the stomach?

A

It acts as a reservoir, partially digests proteins, disinfects because of acid, and forms chyme (bolus + gastric juice) which is released to the small intestine by neuronal and hormonal signals.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the regions of the small intestine and what are their functions?

A
  1. Duodenum - most of digestion of carbs and lipids
  2. Jejunum - more digestion
  3. Ileum - water + bile salt absorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the function of the large intestine?

A

Water absorption via aquaporin. It includes the colon and rectum, chyme is converted into semisolid feces. Distention of the rectal wall causes the defecation reflex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is surface area increased in the lumen of the stomach and intestine?

A

Rugae: infolding in the stomach covered in mucus
Plicae: outfolded fingers covered in microvilli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the layers of the GI tract? Are they continuous throughout the whole GI tract or do they change?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis
  4. Serosa
    Continuous.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the function of epithelial cells in the mucosa?

A

Epithelial cells with polarity (apical + basolateral), the apical side absorbs and the basolateral side shunts nutrients to blood vessels.The basolateral side also has Na/K ATPase and ONLY the basolateral side.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the most variable feature of the GI tract?

A

The epithelial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the different types of epithelial cells in the stomach? In the intestine? What are their purposes?

A

Stomach:
Mucus cells - secrete mucus to act as a barrier to avoid autodigestion
Parietal cells - secrete HCl. Important to activate pepsin.
Chief cells - secrete pepsinogen. It’s not constantly active so it can be safely stored
G cells - secrete gastrin into the blood. All others secrete into the lumen.

Intestine: Called enterocytes. Have microvilli that contain enzymes called the brush border to further digest while absorbing.
Absorptive cells - move nutrients to ECF
Endocrine cells - secrete endocrine hormones into the blood
Goblet cells - secrete mucus, same as in stomach just by a different name
Other secretory cells - mast cells produce histamine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How often are cells in the stomach recycled?

A

Every 3-5 days and they are replaced by pluripotent stem cells in crypts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How do cell to cell junctions vary between the stomach and intestine?

A

In the stomach they have tight junctions to avoid acid getting between cells, and in the intestine they tend to be leaky especially during development where some proteins can directly enter circulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the function of the lamina propria in the mucosa? How does it differ between the small intestine and the stomach?

A

Lamina propria - has hormones and blood vessels next to the epithelium, nerve fibres, and blood and lymphatic vessels (to transport fat molecules). It also has immune cells. Also contains Peyer’s patches, a collection of lymphoid tissue common in the small intestine.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the function of the muscularis mucosae in the mucosa?

A

Muscularis mucosae - a thin layer of smooth muscle, they open or close the surface area generating folds and separate the mucosa from the submucosa. This alters the effective surface area for secretion in the stomach, and food stimulates it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the function of the submucosa?

A

It is a thick connective tissue layer with nerves, glands, blood vessels, and the submucosal plexus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the function of the muscularis?

A

Two layers of smooth muscle, the inner layer is circular and constricts/dilates and the outer layer is longitudinal which shortens/lengthens.
ONLY IN THE STOMACH there is a third layer called the oblique.
It also contains the myenteric plexus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the function of the serosa?

A

The visceral peritoneum, it’s connective tissue and squamous epithelium. In some areas it is continuous with the mesenteries.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How does mechanical mixing in the digestive system work? Why does it occur?

A

It occurs to maximize food exposure to absorptive cells and digestive enzymes.
It occurs via continuous slow waves of graded depolarization that are spontaneously generated.
These waves originate in circular muscle of the muscularis externa in a network of cells called the interstitial cells of Cajal (ICCs).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the frequency of slow waves called?

A

The basic electric rhythm (BER).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does BER vary across the GI tract?

A

It is propagated by electrical coupling in the form of gap junctions, and its height is influenced by neural and hormonal input.

30
Q

What are the two types of contractions involved in GI motility? Where do they occur, what is their purpose, and how do they vary?

A

Tonic: they are sustained, in smooth muscle sphincters and the stomach and act to keep the bolus from moving backwards.
Phasic: they last a few seconds, peristalsis moves the bolus forwards and segmentation of contractions promoted mixing.

31
Q

How does peristalsis work to promote forward movement?

A

Through a progressive wave of contraction. A segment contracts and the bolus moves into the next segment. The distension of this receiving segment’s wall causes the peristaltic reflex to cause another contraction. This is mediated by the enteric NS and is influenced by hormones, paracrines, and the ANS.

32
Q

How do segmental contractions promote mixing?

A

In one segment the circular muscle contracts while the longitudinal muscle relaxes, and in the receiving segment the opposite occurs.

33
Q

What is the use of zymogens in the GI tract?

A

It prevents autodigestion and allows for storage within the cells.

34
Q

How does acid secretion in the stomach work?

A

Carbonic anhydrase produces carbonic acid. Proton concentration increases, it gets pushed against its gradient into the parietal cell with a proton pump (exchanges K+ which leaks back out into the lumen). Bicarbonate goes to the basolateral side and is exchanged into the blood for chloride which diffuses into the lumen (NOT WITH CFTR) once the concentration is high enough, thus HCl is formed.

You can test for the presence of gastric or agastric animals by using an antibody to target carbonic anhydrase.

35
Q

How does secretion of bicarbonate in the pancreas and duodenum work?

A

Carbon dioxide diffuses into the cell and protons are pumped out into the interstitium (basolateral) in exchange for sodium which is removed by Na/K ATPase. An NKCC cotransporter moves from the interstitium into the cell. Potassium passively diffuses out back into the interstitium via channels. A CFTR channel allows built up chloride to diffuse into the lumen. This chloride is then exchanged via an anion exchanger for a bicarbonate.

36
Q

How does secretion in the large intestine work?

A
  1. NKCC cotransporter from interstitium.
  2. Cl- moved into the lumen via CFTR channel
  3. K leaks out, Na+ is actively transported out into the interstitium via Na/K ATPase (basolateral).
  4. The negative Cl- in the lumen attracts Na+ by paracellular pathway which brings water with it because of [] gradients
37
Q

What are secretions in the mouth?

A

Saliva - exocrine secretion
Digestive enzymes - amylase

38
Q

What does the liver secrete that is crucial for GI function? Where is this secretion stored?

A

Bile. It’s crucial for fat metabolism. It gets stored in the gall bladder.

39
Q

What are the endocrine and exocrine functions of the pancreas?

A

Endocrine: insulin, glucagon, etc. Nutrient absorption. To the blood.
Exocrine: buffers, secretions to a tube, usually duodenum. Not to the blood.

40
Q

What is the hepatic portal system used for?

A

It’s a shortcut for nutrient transport from the small intestine to the liver to the pancreas.

41
Q

Where and how are carbohydrates absorbed?

A

In the small intestine. GLUT transporters are required which are not in the stomach. Disaccharidases are in the brush border and break down complex sugars. On the apical membrane, there is an Na+ Glucose symporter (Na/K ATPase powers it via establishing a concentration gradient and is on the basolateral membrane). Glucose then relies on facilitated diffusion by GLUT2 at the BM. Fructose also relies on facilitated diffusion at the BM by GLUT2 and diffuses through the AM by GLUT5. GLUT 4 is necessary for the uptake of glucose and responds to insulin.

Intestinal cells use glutamine as a power source.

42
Q

How does lactose intolerance work?

A

Increase in osmotic pressure in the colon pulls water from the body because lactose cannot be broken down by us.

43
Q

How does protein digestion occur?

A

In the stomach mostly and some in the small intestine, they get digested to peptides and amino acids. Enzymes involved are
1. Endopeptidases - proteases (secreted in the stomach, intestine, and pancreas as inactive proenzymes/zymogens). Break down smaller peptides.
2. Exopeptidases . Break down single amino acids.

44
Q

How does protein absorption occur?

A

Small peptides rely on transporters and further digestion, amino acids are transported.

45
Q

How does fat digestion occur?

A
  1. Bile salts from liver coat fat droplets
  2. Pancreatic lipase and colipase break down fats and store 2 free fatty acids and monoglyceride in micelles.
    3a. Monoglycerides and fatty acids move out of micelles and enter cells by diffusion
    3b. Cholesterol transported into cells by a membrane transporter
  3. Absorbed fats combine with cholesterol and proteins to form chylomicrons in intestinal cells
  4. Chylomicrons released into lymphatic system

Lingual lipase in the mouth also helps.

46
Q

How does bile help digest fat?

A

Bile has salts, pigments, cholesterol. Bile acids combine with aas to form bile salts.
Bile salts break up lipids into micelles. They are absorbed by simple diffusion. Bile acids have a hydrophobic and hydrophilic side. They get recycled.

47
Q

How is nucleic acid digested and absorbed?

A

Not significant in most diets. Pancreatic and intestinal enzymes break down into nucleotides and then bases and monosacchs. Bases get absorbed by active transport.

48
Q

How are fat soluble and water soluble vitamins and minerals absorbed?

A

Fat soluble: absorbed with fats. No transport.
Water soluble: mediated transport
B12: made by bacteria, absorbed by binding to intrinsic factor secreted by stomach. A deficiency results in pernicious anemia.
Minerals: active transport, concentration based
Water and electrolytes (salt): similar to kidney, CFTR channels (chloride)

49
Q

How does digestion and absorption occur in the large intestine?

A

Gut microbes in the colon help absorb amino acids and peptides and digest complex carbs, they produce absorbable vitamins and gas - flatus.

50
Q

How does the ENS work?

A

Separately to the CNS and ANS. It has short reflexes that impact motility, secretion, or growth. It’s in contact with the brain. It has neurons and interneurons that are stimulated by pH, stretch, osmolarity, and products of digestion.

51
Q

How is the ENS similar to the brain?

A

It releases neurotransmitters, there are support cells, capillaries are not very permeable, there is complete reflex integration and no discrete central command center.

52
Q

Where are most serotonin producing cells?

A

In the GI tract.

53
Q

What is the role of digestive hormones?

A

To regulate how quickly food moves from the stomach to the duodenum. They excite or inhibit motility and secretion, are involved in secretory processes, have trophic effects and behavioral effects.

54
Q

What are the families of digestive hormones and what are some key roles they play? Where are they secreted?

A

Gastrin family: Gastrin and CCK. Gastrin triggers pepsinogen secretion from chief cells. CCK tells your brain to stop eating.
Secretin family: Secretin, VIP, GIP, GLP-1. Buffers stomach contents.
Others: motilin. Gut contraction and elongation.

Stomach: gastrin
Intestinal mucosa: secretin, CCK, GIP, motilin
ENS: VIP

Note: GIP is trophic and causes insulin secretion.

55
Q

What signals hormone release?

A

Food dependent or nervous system dependent.
EX: GIP released in response to carbs, secretin is released in response to acid in the small intestine, CCK is released in response to fats and causes gall bladder contraction and slower gastric emptying, and the nervous system secretes gastrin via parasympathetic activity after a meal.

56
Q

What is the role of paracrine hormones?

A

Procolipase splits into colipase and enterostatin (signal for fat satiety)
Histamines are secreted into the ECF on the basolateral side which can control acid secretion
Serotonin increases luminal pressure and stimulates reflexes.

57
Q

What are the gastric event phases?

A

Cephalic: see, smell food. Vagus. Cholinergic.
Gastric
Intestinal

58
Q

What steps constitute the gastric phase?

A
  1. Food or cephalic reflexes start gastric secretion
  2. Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine from ECL cells. The vagus nerve can also directly stimulate the parietal cell or indirectly stimulate it through ECL cell and histamine.
  3. Acid stimulates short reflex secretion of pepsinogen by interacting with the enteric sensory neuron which stimulates chief cells (also secrete lipase)
  4. Somatostatin is released by protons and inhibits G cells, parietal cells, and ECL cells. Negative feedback.
59
Q

What causes stomach ulcers? How can you treat it?

A

Stress or drugs cause too much acid to be secreted or bad mucus cells. Aspirin can cause it. Heliobacter pylori causes an immune response that can destroy the stomach lining. They survive by using urease to make ammonia. A perforating ulcer can cause peritonitis which can be fatal.

Treatment by buffering stomach acid with milk or antacids and proton pump inhibitors like omeprazole.

60
Q

What constitutes the intestinal phase?

A

Chyme moving into the small intestine stimulates the enteric nervous system, which stops gastric motility. Then, depending on the contents of the chyme, other things happen.

Hyperosmo solution: stimulates endocrine cells. Inhibit gastric motility.
Carbohydrates: stimulate GIP and GLP-1 which stimulate insulin secretion in the pancreas. Also inhibit gastric motility and acid secretion.
Fats/Proteins: stimulate CCK, leads to secretion of pancreatic buffers and lipases, acts on GB to release bile, indirectly regs motility.
Acid: stimulates secretin which stimulates pancreatic bicarb release which inhibits acid.

61
Q

What is the trend in the evolution of digestive systems?

A

Increasing anatomical and functional specialization. Sections of GI tract specialize depending on diet of organism.

62
Q

What does a longer intestine imply?

A

Lower quality more complex food. Herbivory.

63
Q

How can you figure out if an organism is gastric or agastric?

A

Look for acid producing cells in the stomach by using carbonic anhydrase as a marker, and check for protons in the lumen. Check for proton ATPase in cells with antibodies, if this is present = gastric!

64
Q

What determines if a fish is gastric or agastric?

A

There are exceptions but generally agastric species are detritivores or herbivores and gastric species are carnivores. A high protein diet means that an animal must be gastric (pepsin)

65
Q

How does the relative intestinal length vary among herbivores, carnivores, and omnivores?

A

RIL will be very large in herbivores and very small in carnivores, with omnivores at an intermediate.

66
Q

What are some ways to increase SA without increasing the length of the intestine?

A

Pyloric cecae (blind ended sacs), spiral intestine, rugae, plicae.

67
Q

How do ruminants improve the digestion of plant materials?

A

They have a very large chamber ahead of the stomach called the rumen filled with microbes (mostly bacteria, some protists, yeasts, and fungi similar to what we have in our hindgut lumen. Anaerobic heterotrophs that ferment.) that break down carbs and then send it to the true stomach, the abomasum. The rumen is nonacidic and next to the esophagus. Examples of ruminants include cattle, moose, deer, sheep and goats.

68
Q

Why is fermentation important in ruminants and hindgut fermenters?

A

The microbes synthesize vitamins and essential amino acids from complex carbs and proteins
Fermentation allows the break down of cellulose, the production of short chain fatty acids, and produces CO2 and methane. It also allows the recycling of waste nitrogen.

69
Q

What are the two different hinds of hindgut fermenters? How do their anatomy and lifestyles vary?

A

Hindgut colon fermenters: very large colon, small large intestine. They can eat over a long period of time and more slowly. Fatty acids are absorbed in the colon.
Hindgut cecal fermenters: much smaller colon, massive cecum. Very little absorbed in the colon. Since most of the digestion occurs in the cecum, very little absorption can occur in the small intestine on first pass so they create pellets and then eat them again to absorb more nutrients. Called cecotrophy.

70
Q

What is Specific Dynamic Action?

A

It’s the amount of energy required to digest a meal. We have a very small SDA because our gut maintains a semi constant state but Burmese pythons have a massive SDA due to rebuilding the brush border of the intestine and other things after a meal. The SDA is caused by increased oxygen intake because the body produces acids, enzymes, and muscle contraction and protein synthesis needs ATP.

71
Q

What are the benefits of the Burmese Python’s digestion style? What is the digestion style of the Burmese Python?

A

They don’t have to constantly secrete the mucosal layer because an acidic environment is not maintained in the stomach when not feeding, and they also are not constantly secreting enzymes, this is energy efficient. They are sit and wait predators. After eating, hypertrophy of the mucosa occurs which breaks down after about 6 days when the prey is fully digested.

72
Q

What is degenerated in the digestive system of the Burmese Python? Is anything maintained?

A

Mucosa, submucosa degenerate leading to a thinner gut and a decreased brush border. Smooth muscles and nerves are maintained. The intestine is rebuilt just ahead of the food and this happens very quickly.

73
Q

What is the best way to measure metabolic rate?

A

Heat production. O2 consumption works as a proxy for very large animals.

ZOOL463 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions