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GASTRO-INTESTINAL MEDICINE AND HEPATOLOGY > STRUCTURE AND FUNCTION OF THE GUT > Flashcards

STRUCTURE AND FUNCTION OF THE GUT Flashcards

1
Q

What is the cell type that lines the entire mouth?

A

Stratified squamous epithelial cells

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2
Q

How many teeth do adults normally have?

A

32

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3
Q

How many teeth do children normally have?

A

20 deciduous teeth

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4
Q

Where do the teeth arise from?

A

Alveolar bone

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5
Q

Where on the tongue are the receptors for sweet foods found?

A

Towards the front

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6
Q

Where on the tongue are the receptors for salty foods found?

A

Anterior middle portion

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7
Q

Where on the tongue are the receptors for sour foods found?

A

Posterior middle portion

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8
Q

Where on the tongue are the receptors for bitter food found?

A

Towards the back

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9
Q

What attached the anterior part of the tongue to the floor of the mouth?

A

The Frenulum

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10
Q

What are the roles of saliva?

A

Lubricate food to aid swallowing
Begin digestion of starches (amylase)
Break down of fats to help tongue analyse fragments (Lipases)
Antibacterial enzymes

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11
Q

How much saliva an adult produce per day?

A

1500 ml, most is swallowed and recycled

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12
Q

What is the enzyme found in the saliva which starts the breakdown of starch?

A

Alpha amylase

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13
Q

What are the names of the three main salivary glands found in the mouth?

A

Parotid gland
Submandibular gland
Sublingual gland

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14
Q

Which salivary gland in the mouth produces the highest percentage of saliva?

A

The submandibular gland - 70%

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15
Q

What is the specific role of the parotid gland?

A

Produces watery secretions lacking mucus

Secretes the alpha amylase

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16
Q

What is the specific role of the submandibular gland?

A

Secretes mucolipoproteins

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17
Q

Is saliva isotonic, hypertonic or hypotonic?

A

Hypotonic

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18
Q

What is the oesophageal hiatus?

A

The point where the oesophagues passes through the diaphragm and hence enters the abdomen

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19
Q

What proportion of the oesophagus is made of striated muscle?

A

The upper third

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20
Q

What proportion of the oesophagus is made of smooth muscle?

A

Lower two thirds

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21
Q

At what spinal level does the oesophageal hiatus sit?

A

T10

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22
Q

What is the name of the oesophageal sphincter that closes off the entrance to the stomach?

A

Cardio sphincter or lower oesophageal sphincter

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23
Q

Which nerve controls the sphincters of the oesophagus?

A

Vagus nerve

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24
Q

Describe the nervous pathway of swallowing.

A

Sensory endings in the mouth signal presence of food
Sends signal to nucleus of the tractus solitarius (solitary tract, NTS)
Activates motor neurones in nucleus ambiguus
Controls muscles of soft palate, larynx and epiglottis

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25
Q

What is the capacity of the average adult stomach?

A

4 Litres

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26
Q

What do we call the superior part of the stomach where the bolus enters?

A

The fundus

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27
Q

What is the name of the folds in the stomach that allow it to expand?

A

Rugae

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28
Q

What are the functions of the stomach?

A 
Temporary storage of food
Mechanical breakdown of food
Pepsin digestion of proteins
Controlled passage of chyme into small intestine
Secretion of intrinsic factor
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29
Q

What is chyme?

A

The name used for the semi-digested material which is passed on from the stomach to the small intestine.

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30
Q

What is the role of intrinsic factor?

A

It protects vitamin B12 from the very low pH of the stomach. It is absorbed with the vitamin in the ileum.

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31
Q

What is the name of the additional muscle layer in the stomach wall not found in other parts of the GI tract? What is its function?

A

Inner oblique muscle

Churn up the food

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32
Q

What is the primary barrier which prevents the digestive enzymes from digesting the stomach wall?

A

A very thick layer of mucus

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33
Q

Which cells secrete gastrin from the stomach wall?

A

G cells

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34
Q

Which cells secrete HCl from the stomach wall?

A

Parietal (oxyntic) cells

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35
Q

Which cells secrete intrinsic factor from the stomach wall?

A

Parietal (oxyntic) cells

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36
Q

What are pepsinogens and which cells are responsible for secreting them from the stomach wall?

A

Pepsinogens are inactive precursors of pepsin secreted from the chief cells (or peptic cells)

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37
Q

What is the role of gastrin?

A

Stimulates the release of acid from the parietal cells.

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38
Q

What are the components of gastric juice?

A 
Salts
Water
HCl
Pepsinogens
Intrinsic factor
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39
Q

What are the three ions channels/transporters found on the lumen side of the parietal cells, used in the secretion of acid?

A

Proton pump - K+ in for H+ out - active transport
K+ and Cl- co-transporter - passive transport
Cl- channel

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40
Q

Where do the protons used to make acid come from?

A

Water

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41
Q

How are the OH- ions, made as a by product of acid secretion, dealt with?

A

They are deposited in the blood as bicarbonate.

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42
Q

What is the pH of the blood in the gastric vein? What do we call this?

A

“Alkaline tide”

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43
Q

What is the pH in the lumen of the stomach?

A

pH ~ 1.3

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44
Q

What are the roles of stomach acid?

A

Denatures connective tissue and muscle fibres of meat

Combines with calcium and iron in the food to form soluble salts that can be digested

Activates inactive pepsinogens

Optimizes pH for pepsins

Kills germs

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45
Q

What do we call pepsinogens wrapped up in membrane-bound granules?

A

Zymogens

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46
Q

Does the stomach secrete lipase?

A

Yes, however not much fat digestion occurs in the stomach

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47
Q

What is secreted with the mucus to prevent the digestion of the stomach wall?

A

Bicarbonate to shield wall from acid

48
Q

What prevents stomach acid from getting under the epithelium?

A

Tight junctions

49
Q

What increases mucus production?

A

Prostaglandins increase mucus production and increase blood flow to the mucosa, bringing bicarbonate with it.

50
Q

How much gastric juice is made in the adult stomach on an average day of eating?

A

2-3 litres

51
Q

What are the three phases that regulate gastric secretion?

A

Cephalic phase
Gastric phase
Intestinal phase

52
Q

What triggers the cephalic phase of gastric secretion?

A

Smell, sight, taste of food, chewing

53
Q

What transmits the signal in the cephalic phase?

A

Vagus nerve

54
Q

What triggers the gastric phase of the gastric secretion?

A

Distension of the stomach

55
Q

What triggers the intestinal phase of gastric secretion?

A

Protein digestion products in the duodenum

56
Q

What inhibits gastric secretion?

A

Low pH

Intestinal phase - Secretion of secretin, CCK and GIP

57
Q

What are the two parts of the stomach’s motor system?

A

Proximal motor unit

Distal motor unit

58
Q

How does the stomach churn up and mix the contents?

A

Through a peristaltic wave mainly from the distal motor unit

59
Q

What are the three parts of the small intestine?

A

Duodenum
Jejunum
Ileum

60
Q

What is the average length of the small intestine in an adult?

61
Q

What is the average width of the small intestine in an adult?

62
Q

What are the main two functions of the small intestine?

A

Digestion

Absorption

63
Q

What is particular about the folds in the small intestine in terms of how the chyme is passed through?

A

The folds force the chyme to take a spiral pathway

64
Q

What is the brush border of the small intestine?

A

The wall of the small intestine contains villi, which themselves have microvilli. These microvilli increase surface area and are sometimes referred to as the brush border.

65
Q

What is the name of the glands found in between the villi in the small intestine?

A

Crypts of Lieberkuhn

66
Q

How far do the Crypts of Lieberkuhn extend through the wall of the small intestine?

A

Down to the muscularis mucosa

67
Q

What do the endocrine cells of the Crypts of Lieberkuhn in the small intestine produce?

A

Secretin
Somatostatin
Entereroglucagon
Serotonin (5-HT)

68
Q

What is the pH of the fluid secreted into the lumen of the small intestine?

69
Q

What stimulates the secretion of secretin in the small intestine?

70
Q

What stimulates the secretion of cholecystokinin in the small intestine?

A

Fat digestion products

71
Q

What is the length of the duodenum?

72
Q

Is the duodenum contained within mesentery?

73
Q

Other than the chyme, what else enters the duodenum?

A

Bile

Pancreatic juices

74
Q

What is the name of the sphincter that separates the duodenum from the bile and pancreatic ducts?

A

Sphincter of Oddi

75
Q

How does the duodenum protect itself from the bile and the pancreatic juices?

A

It secretes an alkaline mucus

76
Q

Are the jejunum and ileum supported by mesentry?

77
Q

What is the arterial supply to the jejunum and ileum?

A

Superior mesenteric artery

78
Q

What is particular about the mucosal thickness of the jejunum and ileum?

A

As you move distally, there is a gradual reduction in the mucosal thickness

79
Q

Is the pancreas an endocrine or an exocrine gland?

80
Q

What are the endocrine functions of the pancreas?

A

Secretion of insulin and glucagon

81
Q

What cells secrete digestive enzymes from the pancreas?

A

The acinar cells

82
Q

Innervation of the endocrine islets of the pancreas is supplied by what?

A

Parasympathetic vagal nerve

83
Q

What is the role of the duct cells in the exocrine ducts?

A

Regulated by secretin, they release a HCO3- rich secretion which is added to the enzyme and Cl- rich secretion from the acinar cell above.

84
Q

What are the enzymes released from the pancreas that are responsible for the digestion of protein?

A

Trypsin
Chymotrypsin
Elastase
Carboxypeptidase

85
Q

What is the enzyme released from the pancreas that is responsible for the digestion of sugars?

86
Q

What are the enzymes released from the pancreas that are responsible for the digestion of oils and fats?

A

Lipase
Colipase
Phospholipase
Cholesterol esterase

87
Q

What is the major activator of most of the enzymes released from the pancreas?

88
Q

What is the zymogen of trypsin?

A

Trypsinogen

89
Q

What emulsifies fat before digestion?

90
Q

What is the enzyme used as the catalyst in bicarbonate ion production?

A

Carbonic anhydrase

91
Q

How are bicarbonate ions secreted into the lumen of the pancreatic ducts?

A

Cl- exchanger

92
Q

How are the protons left behind as a by product of bicarbonate ion production removed from the cell?

A

Na+ ions are countertransported at the non-lumenal side.

93
Q

What regulates the secretion of the aqueous component of pancreatic juices?

94
Q

What is the first part of the large intestine?

A

The caecum

95
Q

How much passes into the large intestine everyday in the average healthy adult?

A

About 500 ml

96
Q

What are taeniae coli?

A

Thickened bands of longitudinal muscle

97
Q

What are haustra?

A

Pockets formed by the smooth muscle action of the taeniae coli.

98
Q

What is the function of the large intestine?

A

Storage of residues before elimination
Secretion of mucus to lubricate faeces
Absorption of remaining water and electrolytes

99
Q

Where in the GI tract is most of the water reabsorbed?

A

The small intestine

100
Q

How much water is reabsorbed in the large intestine?

A

400-1000 ml

101
Q

What happens if the large intestine fails to reabsorb the water?

102
Q

How does re-absorption by the large intestine occur?

A

Sodium ions actively taken up, under control of aldosterone.

103
Q

What otherwise indigestible things are digested by flora in the large intestine?

A

Some carbohydrates and lipids

104
Q

Give an example of an aerobic microbe found in the flora of the large intestine.

A

Enterobacter aerogenes

105
Q

Give an example of an anaerobic microbe found in the flora of the large intestine.

A

Clostridium perfringens

Bacteroides fragilis

106
Q

How do microbes naturally found in the flora of the large intestine contribute to the bilirubin cycle?

A

Convert bilirubin into non-pigmented urobilinogens.

107
Q

What are the vitamins synthesized by the microbes naturally found in the flora of the large intestine?

A 
Vitamin K
Biotin
Vitamin B12
Folic acid
Thiamine
108
Q

Why might antibiotics lead to an increased risk of bleeding?

A

Vitamin K synthesized by microbes naturally found in the flora of the large intestine is a cofactor in the production of blood clotting factors.

109
Q

How long does stuff end up staying in the large bowel in an average adult?

A

16-20 hours

110
Q

What muscle layer contracts in the mixing movements of the large intestine?

A

Circular muscle

111
Q

Which parts of the large intestine have peristaltic movements occur and different points throughout the day?

A

The transverse colon and descending colon

112
Q

What is a mass movement of the large bowel?

A

Portion of the colon that contracts is longer than a normal peristaltic wave. Material is moved out of the proximal colon. When the mass movement happens in the descending colon we experience the need to defecate.

113
Q

Does the rectum normally contain anything?

A

No, not unless we need to defecate.

114
Q

Which sphincter in the rectum is under voluntary control?

A

The external anal sphincter

115
Q

What controls the internal anal sphincter?

A

Sympathetic inhibitory fibres of the autonomic system

GASTRO-INTESTINAL MEDICINE AND HEPATOLOGY (24 decks)

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