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BIOL10002 > 27. Regulation of Digestion > Flashcards

27. Regulation of Digestion Flashcards

1
Q

Why is digestion necessary?

A
  • Major food nutrients are large macromolecules which cannot pass through the lining of the intestine
  • They must be broken down to small molecules that can pass through cell membranes
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2
Q

What does physical digestion involve?

A

The physical breakdown of food into small particles by grinding or chewing to increase surface area

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3
Q

What is enzymatic digestion?

A

The breakdown of complex molecules by hydrolytic enzymes usually secreted into the gut lumen

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4
Q

What does physical digestion require?

A

Jaws and strong jaw muscles

- Teeth of different types

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5
Q

What are the three types of teeth?

A

Incisors, canines, molars and premolars

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6
Q

What is the first component of the digestive tract?

A

The oral cavity

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7
Q

What is the purpose of the oral cavity?

A

Physical breakdown or mystification of ingested food

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8
Q

Why is the physical breakdown of food in the oral cavity necessary?

A

Necessary for efficient chemical digestion (increases surface area)

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9
Q

What enzyme is involved in the oral cavity?

A

Salivary amylase which is secreted from salivary glands acting on the substrate (starch/glycogen) to produce maltose (end product)

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10
Q

What is the second component of the digestive tract?

A

The oesophagus

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11
Q

What does the oesophagus do?

A

It is a muscular tube which transports food through the thorax and diaphragm to the stomach

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12
Q

What is the epiglottis?

A

A covering that blocks the trachea so that food goes straight down into the stomach

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13
Q

What are the two sphincters?

A

The lower esophageal sphincter and the pyloric sphincter

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14
Q

What is the purpose of the sphincters?

A

They are control points to ensure food enters the stomach at the correct point and exists when it needs to (no back flow or premature entry)

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15
Q

What is the lower oesophageal sphincter between?

A

Oesophagus and the stomach

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16
Q

What is the pyloric sphincter between?

A

Stomach and small intestine

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17
Q

What are the three types of cells in the gastric pit in the stomach?

A

Chief cells, parietal cells and epithelial cells

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18
Q

What do chief cells do?

A

They secrete pepsinogen

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19
Q

What do parietal cells do?

A

Produce hydrochloric acid

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20
Q

What do epithelial cells do?

A

Secrete mucus which protects the tissues from the acids and enzymes

21
Q

How is pepsin secreted?

A
  • Chief cells secrete pepsinogen, the inactive form or zymogen of the protease pepsin
  • The low pH of the stomach converts it to the active form
  • Pepsin activates other pepsinogen molecules in a process called autocatalysis
22
Q

What is the third component of the digestive tract?

A

The stomach

23
Q

What component of the stomach churns food?

A

Thick muscular walls churn food

24
Q

What is the substrate and end product of the enzyme pepsin?

A

The substrate is polypeptide bonds and the end product is large peptides

25
Q

What is the fourth compartment of the digestive tract?

A

The small intestine

26
Q

What are the three different regions of the small intestine?

A

Duodenum Jejunum and ileum

27
Q

What is the purpose of the small intestine?

A
  • Moves chyme forward from the stomach
  • Continues enzymatic digestion with secretions from cells in its walls and from accessory digestive glands
  • Absorbs products of digestion through villi
28
Q

What does the gallbladder do?

A

Stores bile which aids in digesting lipids

29
Q

What does the liver do?

A

Synthesises bile salts from cholesterol and secretes them as bile

30
Q

What does the pancreas do?

A

Produces digestive enzyme and bicarbonate solution

31
Q

What is the purpose of bicarbonate?

A

Bicarbonate is required to neutralise the pH of the chyme released from the stomach

32
Q

What is the pathway of the movement of bile from the liver?

A

Bile flows through the HEPATIC DUCT to the DUODENUM and through the CYSTIC DUCT to the GALL BLADDER where bile is stored

33
Q

What does bile do?

A
  • Bile salts emulsify fats in the chyme
34
Q

How are micelles formed?

A
  • One end of the bile salt molecule is lipophilic and the other end is hydrophobic
  • The lipophilic ends merge with fat droplets and keep them from sticking together
  • This enlarges the surface area exposed to lipase that digest fat
35
Q

What is the action of lactase?

A

Breaks down lactose into galactose and glucose

36
Q

What is the action of sucrase?

A

Breaks down sucrose into fructose and glucose

37
Q

What is the fifth compartment of the digestive tract?

A

The large intestine (colon)

38
Q

What is the function of the large intestine?

A
  • Absorption of water and inorganic ions

- Formation and storage of faeces from undigestable material. These are periodically excreted from the rectum

39
Q

What nervous system controls the constriction of the muscles in the large intestine?

A

Enteric nervous system

40
Q

What are the names of the two layers of smooth muscle that are outside the submucosa?

A

The circular muscle layer and the longitudinal muscle layer

41
Q

What is the circular muscle layer?

A

Innermost cells oriented around the gut which CONSTRICT the gut

42
Q

What is the longitudinal muscle layer?

A

Outermost cells oriented along the gut which shorten the gut

43
Q

How does the absorption of breakdown products of carbohydrates occur in the small intestine?

A
  • Carbs are absorbed as monosaccharides into the capillaries of the villi
  • Glucose is taken up by active transport
  • Blood vessels drain into hepatic portal vein which carries blood to the liver
  • The liver converts carbs into glycogen which is stored in the liver
44
Q

How does the absorption/breakdown of proteins occur in the small intestine?

A
  • Absorbed into the capillaries as amino acids
  • Taken up directly by cells which are synthesising proteins
  • Excess is deaminated by the liver which uses nitrogen to form urea for excretion
45
Q

Which breakdown products of the small intestine may be absorbed directly into underlying blood vessels irrespective of need?

A

Water salts and alcohol

- Excess excreted by kidneys

46
Q

How does the absorption of fats occur in the small intestine?

A
  • Fats are absorbed as glycerol and neutralised fatty acids into lacteals and then via lymphatics back to major veins near the heart
  • Excess stored in adipose tissue
47
Q

What is the role of gastrin?

A
  • Food entering the stomach stimulates release of gastrin hormone from the stomach mucosa into the blood
  • Causes the release of HCl and pepsin from the stomach mucosa
48
Q

What is the role of secretin?

A
  • Acid in duodenum causes the release of secretin from intestinal mucosa
  • This causes the pancreas to release bicarbonate and the gall bladder to release bile

BIOL10002 (28 decks)

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