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Sport Sci > Digestion and Absorption (Lecture four) > Flashcards

Digestion and Absorption (Lecture four) Flashcards

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1
Q

Define digestion:

A

Breaking down of food into small units that can be absorbed.

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2
Q

Define Absorption:

A

Transport of nutrients from the intestine to the blood or lymph systems.

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3
Q

What is the first part of the GI tract involved in digestion?

A

The Mouth

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4
Q

How is the mouth involved in digestion?

A

Chewing mechanically breaks up food, increasing its surface area. Saliva aids in digestion.

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5
Q

After the mouth what is the next part of the GI tract?

A

The esophagus. (simply transports food)

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6
Q

After the esophagus is the? and what is its function?

A

The stomach.

1.5L j shaped bag that stores food.

Very little absorption occurs here besides water and alcohol.

Food mixes with gastric gases which further breaks it down.

Regulates the digestion of food.

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7
Q

Describe the small intestine and its specialized structures:

A

Duodenum, Jejenum, Ilium.

Plicae, (folds that increase SA) and villi + microvilli for increased absorption into the underlying capillary network

Each villus has a lacteal too (lymph)

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8
Q

Whats the function of the gall bladder?

A

Stores, concentrates and releases bile.

Bile facilitates the absorption of fats (emulsification)

Released through the hepatic duct which feeds into the duodenum

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9
Q

What is the function of the pancreas?

A

Endocrine and exocrine organ. Releases digestive juices into the duodenum

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10
Q

Function of the large intestine?

A

Absorbs water and electroclytes.

Stores waste before excretion.

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11
Q

What is the transit time of food in the GI tract before excretion?

A

1-3 days typically.

Time food spends in the digestive system.

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12
Q

What is motility?

A

The movement of food within the digestive system.

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13
Q

How is motility achieved?

A

Peristalsis - mixes and moves food.

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14
Q

When is peristalsis increased?

A

post meals.

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15
Q

How long does digestion take?

A

4-6hrs

BUT is dependent on the nutrient

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16
Q

How is CHO digestion started?

A

Digestion starts in the mouth.

800-1500mL Saliva released per day

99.%% water but contains a-Amylase which breaks down CHO

CHewing increases surface area for contact with amylase

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17
Q

How does CHO digestion occur in the stomach?.

A

Acid slows amylase action.

CHO mostly oligosaccharides

passes through to duodenum

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18
Q

How does the small intestine promote CHO digestion?

A

pH (higher than stomach) increase activating enzymes for digestion.

Small glucose polymers (dextrose) and maltose mostly present.

Unique enzymes present at the villus and microvilli

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19
Q

What are the enzymes present at the villi and microvilli/

A

Maltase - Maltose to 2 x Glucose
Sucrase - Sucrose to glucose and fructose
Lactase - Lactose to glucose and galactose

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20
Q

Is fibre digested?

A

If fibre is composed of cellulose then NO

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21
Q

How does lipid digestion start?

A

Silivia contains (lingual) lipase.

  • Splits glycerol into three FA
  • Gastric lipases continue TG breakdown
  • Lipases account for 10-30% TG digestion.
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22
Q

How does lipid digestion occur in the small intestine?

A

Bile and pancreatic lipases are secreated.

Bile aids in emulsification - (the lipases break mono,di, TG into FA) so the FA forms small droplets, allowing them to remain in water.

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23
Q

Where does protein digestion occur?

A

Stomach and SI

24
Q

How does protein digestion occur in the stomach?

A

pH relient, pH activates pepsinogen into pepsin which breaks down proteins. (protease)

25
Q

How does protein digestion occur in the SI?

A

Basic environment activates trypsin and other pancreatic proteases.

26
Q

What do proteases do?

A

Proteases breakdown protein to amino acids, dipeptides, or tripeptides for absorption

27
Q

How are CHO absorbed?

A

AS monosaccharides.

SGLT transports Glucose, Galactose with two Na

GLUT 5 transports fructose.

From epithelium to capillary uses GLUT 2

28
Q

How are FA absorbed?

A

Fat droplets move to the area of villi and microvilli.

FA diffuse across the membrane and are incorperated into new triglycerides

Triglycerides combine with cholesterol and phospholipids to form chylomicrons - making the transport of fats in an aqueous environment possible

29
Q

How does the absorption of amino acids occur?

A

AA, diAA and triAA cros the epithelium with a Na dependent transporter. Then are broken down into AA within the cell. Transported into Capillaries via active transport and flow to the liver via the hepatic portal vein.

30
Q

Where does most water absorption occur?

A

Jejenum

31
Q

What defines water absorption?

A

Laws of diffusion/ osmosis.

Nature of tight junctions
Expression of aquaporins
ECF osmolarity

i.e osmotic gradient causes water movement

32
Q

How are vitamins absorbed?

A

Passive diffusion in the small intestine mostly.

However fat soluble vitamins are absorbed with FA

Water soluble vitamins are not stored in tissues therefore are excess intake is excreted in urine

33
Q

Describe the absorption of minerals:

A

Minerals are not well absorbed therefore the intake in food is far higher than that which is needed.

34
Q

Describe the absorption of iron and calcium:

A

15% of animal iron is absorbed
• 2-10% of plant iron is absorbed
• 35% of calcium in absorbed while 50% is excreted in urine.

35
Q

What are five factors that affect GI Emptying?

A
  • Volume of food
  • Osmolality
  • Energy Density
  • Exercise Intensity
  • psychological factors
36
Q

How does the volume of food affect GI emptying?

A

Large volume of food empty faster

37
Q

How does Osmolality affect GI emptying?

A

Higher osmolality slows GI emptying

38
Q

How does energy density affect GI emptying?

A

Fat is a very strong inhibitor of gastric empyting

CHO and Protein can inhibit gastric inhibiting depending on concentration

39
Q

How does exercise intensity affect gastric intensity?

A

Above ~80% VO2 max slows gastric emptying.

40
Q

What is gastric empyting?

A

The flow of food from the stomach through the pyloric valve into the duodenum.

41
Q

What could be possible causes of GI problem in exercise?

A

During exercise shunts shift blood from the GI tract to the muscles, decreased blood flow up to 80% may attribute to GI problems.

42
Q

Among whom is GI problems more common?

A

30-50% of endurance athletes report GI distress during competitions

More often in:
Females
Younger Athletes
Runners

43
Q

What are some upper GI problems?

A

Vomiting
Heartburn
Bloating

44
Q

What are some lower GI problems?

A

Diarrhea

Bleeding

45
Q

What are related problems to GI problems?

A 
Urge to urinate
Urge to defecate
Side Ache
Nausea
Dizziness
46
Q

what are ways to avoid GI distress?

A
  • Adequate conditioning
  • Drinking regime
  • Avoidance of strongly hypertonic solutions
  • CHO rich diet with avoidance of large changes in diet pre-competition
  • Avoidance high dietary fibre before competition
  • Avoidance of extra caffeine, vitamin C, bicarbonate or dairy (if lactose intolerant) pre-competition.
  • Avoidance of anti-inflammatory medications.
  • Medical examination if symptoms occur in non-exercising state.
47
Q

What does exercise cause in regards to water and CHO?

A

Exercise induces deficits in water, CHO as they are used.

48
Q

What does GI mean in sport sci?

A

Glycemic index

49
Q

What causes heartburn?

A

Incompetent inferior esophageal spincter

50
Q

What does the gall bladder contain?

A

12hrs of bile, which consists of water, electrolytes, proteins etc.

51
Q

With regards to motility what does sport induce?

A

Increased motility due to irritation of the GI tract caused by sport.

52
Q

What is emulsification?

A

The conversion of fat into a form that can be suspended in water.

53
Q

Where does protein digestion occur and why?

A

In the stomach and small intestine, regulated by pH because otherwise autodigestion could occur.

54
Q

What limits CHO uptake?

A

Saturation of transporters. Hence why sports drinks include multiple types of monosaccharides to increase maximal CHO uptake.

55
Q

Why are sports drinks isotonic?

A

To replenish lost salts, CHO and water

56
Q

How does exercise influence the rate of gastric emptying?

A

Static exercise (no change in rhythm) results in homeostasis and faster rates of gastric emptying over dynamic exercise which hinders this.

Sport Sci (20 decks)

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