Digestive system Flashcards

1
Q

What does the GI tract consist of?

A

Mouth, esophagus, stomach, small intestine, large intestine, caecum, rectum

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

what components are added to the GI tract to create the digestive system?

A
  • salivary glands, gall-bladder, liver, pancreas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

general function of the mouth in digestion

A
  • mechanical breakdown of food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

general function of the esophagus in digestion

A
  • unidirectional tube that connects the mouth to the stomach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

general function of the stomach in digestion

A
  • holds food
  • distinguishes the 4 systems from each other
  • can be monogastric, avian, or 4 compartment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

general function of the small intestine in digestion

A
  • takes up nutrients into the body
  • “nutrient gateway”
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

general function of the large intestine in digestion

A
  • flows into caecum
  • majority of gut bacteria resides here
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

general function of the caecum in digestion

A
  • abundance of gut bacteria
  • roll in breaking down indigestible carbs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

general function of the rectum in digestion

A
  • things not digested are excreted from the body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are different ways you can classify a dietary CHO by for digestion?

A
  • solubility
  • digestability
  • fermentability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

solubility of CHOs

A

is a CHO soluble in the aqueous environment of the digestive tract?
yes = soluble
no = insoluble
- determined by physicochemical properties of CHO

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

digestability of CHOs

A

does the host organism have the enzymes necessary to digest a CHO?
yes = digestible
no = not digestible (fibre)
- determined by the host digestive enzymes

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

fermentability of CHOs

A

do gut bacteria have the enzymes necessary to break down a CHO?
yes = fermentable
no = non-fermentable
- determines by gut bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

4 types of digestive systems

A
  1. simple system (w/o caecum)
  2. simple system (w/ functional caecum)
  3. ruminant system
    4.avian system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

simple system w/o caecum: key features

A
  • human, cat, pig, dog
  • monogastric (single stomach)
  • non-functional caecum (still there but does not contribute to fermentation of digestible CHO)
  • hindgut fermenter
  • suited for a nutrient-dense, low fibre diet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how does the oral cavity work in a simple system?

A
  • food is chewed and mixed with saliva
  • 2 enzymes get the ball rolling…
    1. a-amylase: starts to break down CHO
    2. lingual lipase: starts to break down dietary fats
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How does the stomach work in a simple system?

A
  • includes the cardia, fundus, body and antrum
  • empty = 50mL, filled = 1-1.5L (remarkable ability to expand when food is consumed)
  • gastric emptying takes 2-6 hours
  • pH is about 2 (acidic)
  • food becomes chyme (food + acid)
  • gastric glands secrete gastric juice (includes H2O, electrolytes, HCl, enzymes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how does the small intestine work in a simple system?

A
  • includes the duodenum, jejunum and ileum
  • main site for nutrient digestion and absorption
  • surface area = 30m^2
  • intestinal motility is controlled by longitudinal and circular muscles
  • chyme acidity neutralized by pancreatic juice
  • food is digested by pancreatic juice and bile acids
  • soluble fibre = slows down digestion, insoluble = speed up
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how does the large intestine (aka colon) work in a simple system?

A
  • by the time food reached the LI most nutrients have already been taken up
  • site of fermentation - break down indigestible carbs
  • production of SCFA aka volatile fatty acids
  • site for water absorption
  • bile acids are taken back up and recycled
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What gives the small intestine such a large surface area

A
  1. kercking folds
  2. villi (and crypts) - pertrusions
  3. microvilli
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the different nutrient transport mechanisms for molecules to pass through the intestinal lumen?

A
  1. Diffusion
    - molecules follow a concentration gradient
    - small molecules with the right chemical properties can pass through with no energy needed
  2. Facilitated diffusion
    - like diffusion but involves a transporter
  3. Active transport
    - requires energy (ATP) to move molecules against a concentration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how can we decide which transport mechanism to use to get molecules from the intestinal lumen to the cytoplams

A
  • solubility of the molecule
  • concentration gradient
  • molecular size
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Gut bacteria

A
  • region specific - not evenly distributed along the tract
  • 1000:1 anaerobic to aerobic bacteria
  • very important for the fermentation of non-digestible CHO
  • CHO fermentation produces many compounds (e.g lactate and SCFA)
  • associated with disease
24
Q

simple system w/ functional caecum: key features

A
  • horse, rabbit and hamster
  • pseudo-ruminant
  • hindgut fermenter
  • functional caecum
  • all other regions of the gut function similar to the monogastric system
  • suited for a diet with large amounts of fodder and foraging
25
what is the purpose of a functional caecum in a simple system?
- enormous hindgut (20-30L capacity) filled with bacteria - SCFA provide 70% of total energy needs for host - site for the production of vitamins
26
what are signs of an energy or nutrient deficiency for animals with a functional caecum?
- Coprophagy (eating dung or feces) - young animals eating feces colonize their guts with bacteria
27
where are nutrients absorbed in a simple system w/ a functional caecum?
stomach: nothing small intestine: glucose, amino acids, fatty acids large intestine/caecum: lactic acid, amino acids, SCFA - indigestible fibre does not get absorbed - few of the fat, proteins and CHO are not digested and are excreted from the body
28
lactic acid in horses
- lactic acid is produced in a diet high in carbs for horses - horses cannot vomit - colic will develop if there is too much lactic acid produced
29
Ruminant (multiple) system: key features
- cattle, sheep, goats - stomach is divided into 4 regions: reticulum, rumen, omasum, abomasum - system highly suited for animals that eat a high quantity of fodder and forage plant materials - all other regions of the gut function similar to the monogastric system
30
ruminant digestion: reticulum
- honeycomb appearance serves as a filter: can capture and trap foreign materials that are accidentally swallowed - can cause hardware diease - rich in bacteria (fermentation vat)
31
ruminant digestion: rumen
- the largest section of the stomach - rich in bacteria (fermentation vat) - rumen papillae: similar to vili, increase surface area for absorption - food is mixed and partially broken down and stored temporarily - 60-80% of total energy produced here as SCFA
32
ruminant digestion: omasum
- resorption of water and some electrolytes - filters large particles
33
ruminant digestion: Abomasum
digestive enzymes secreted from gastric glasnds (HCl, mucin, pepsinogen, lipase, etc)
34
fermentation in the ruminant system
- fermentation takes place before entering the intestine (foregut digestion) - nutrients produced by bacteria are available for digestion and absorption by the ruminant 2 ways to get rid of products of fermentation... 1. rumination: partially digested food called cud is regurgitated and chewed further then re-swallowed 2. eructation: periodic belching where methane gas is released from the stomach - can be bad because energy is lost
35
pros and cons of the ruminant system
pros - vitamin synthesis (B and K) - non-protein nitrogen used for making protein cons - carbohydrates degraded into gases and lost through eructation - heat production (large methane released)
36
avian system: key features
- chickens, turkeys - beaks and claws break up foods into smaller pieces that birds can swallow (don't have teeth) - rapid digestion (can starve if deprived of food for even a few hours)
37
unique components of the avian system
- crop - two chambered stomach - small intestine - ceca - large intestine (slight different function) - cloaca
38
avian system: crop
- enlarged area of the esophagus - well developed in most species but not in all - temporary storage location for food - food is softened here and often regurgitated to feed offspring
39
avian system: two-chambered stomach
Glandular portion: proventriculus - chemical digestion, gastric enzymes and HCl secreted - most comparable with monogastric stomach Muscular portion: Gizzard - has stone-like objects used for mechanical breakdown - grind and digest tough food
40
avian system: ceca
- minor site of bacterial fermentation - fermentation is not critical for avians but happens because bacteria are here
41
avian system: large intestine
- very short and serves predominantly to connect the small intestine and cloaca - a bit of storage of undigested material - water absorption
42
avian system: cloaca
- very unique - where the digestive, urinary and reproductive system meets - makes it difficult to understand how much is actually absorbed in birds
43
What is digestibility?
- measure of the fraction of a specific nutrient (or of energy) that is extracted by the GI tract -how much nutrient actually gets absorbed by the body - calculated from the amount of nutrient consumed and the amount appearing in feces - represents a combination of nutrient release from the food matrix, microbial fermentation and absorption
44
why is determining digestibility important?
- can prevent deficiency and ensure essential nutrients are available to the organism ( to support their lifestyle)
45
measuring digestibility: total collection method
- measures everything that goes in (food) and comes out (feces) - allow the animal to adapt to a diet over 7-21 days - isolate the animal for quantitative analyses - measure intake over a 3-10 day period - collect and weight all feces - analyze for nutrient
46
how do you calculate the apparent digestibility coefficient?
apparent digestibility coefficient = (total intake - total feces) / total intake the closer to 100%, = almost complete absorption of the nutrient
47
limitations of the total collection method
- accuracy in measuring food intake (e.g. crumbs) - metabolic cages create anxiety in animals, causing them to behave abnormally - labour intensive - animals confined in costly equipment - not feasible for captive wild animals (not much control)
48
what do metabolic cages do
collect and analyze urine and feces
49
measuring digestibility: Indicator method
- incorporates a marker into the food and tracks it - internal marker: a natural component of the feed - external marker: a component added to the feed - adapt the animal to test diet containing the marker - collect a feed and fecal sample - analyze each for the marker and nutrient of interest relative to your indicator
50
what is the difference between the total collection method and the indicator method
- indicator method just requires a sample since the marker will appear in both the feed and feces
51
what are characteristics of a marker for the total collection method?
1. non-absorbable 2. must not affect / be affected by the GI tract (not upset stomach) 3. must mix easily with the food 4. easily and accurately measured in samples
52
apparent digestibility coefficient for indicator method
(A - B) / A A = ratio of nutrient/marker in the feed B = ratio of nutrient/marker in feces
53
advantages of indicator method
- less labour intensive - ideal for wild animals
54
What is apparent digestibility?
- under-estimates the true digestibility doesn't take into account... 1. endogenous secretions - epithelial cells (e.g. fatty actids released from dying intestinal cells) - secreted into lumen and appear in feces 2. Bacterial growth in gut - nutrient synthesis takes place (e.g. biotin produced by gut bacteria) 3. Digestive enzymes - protein secretion (e.g. digestive enzymes released by cells)
55
What is true digestibility?
- perform a digestibility study using a test diet - switch to diet containing none of the nutrient of interest - analyze the feces after test diet is cleared - subtract the level of nutrient in feces of animals fed the zero nutrient diet from a test diet
56
how can you calculate the true digestibility coefficient?
use indicator marker method (A - (B -C)) / A A = ratio of nutrient/marker in TEST DIET B = ratio of nutrient/marker in feces C = ratio of nutrient/marker in feces after ZERO NUTRIENT DIET
57
what are some factors that affect digestibility?
- feed intake (what are they eating?) - particle size (smaller particles have faster transit time) - chemical composition (what nutrients?) - climate (hotter temps have different digestibility than colder) - age (younger can have different efficiency as older)