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bi0005 > Digestion and Absorption 1 > Flashcards

Digestion and Absorption 1 Flashcards

1
Q

What are the General Functions of the GI Tract

A 
Digestion- physical and Chemical
Secretion
Expulsion
Protection (immune system)
Motility
Storage
Absorption- the ultimate goal as needed for growth and repair
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2
Q

Physical Processes of Digestion

A

Chewing, peristalsis, segmentation

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3
Q

What is Peristalsis

A

The wavelike, rhythimic muscular contractions of the GI tract that move chyme down its tract

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4
Q

Which muscles are involved in peristalsis

A

Circular muscles which give alternating waves of contraction

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5
Q

What is segmentation

A

Periodic squeezing and partitioning of the SI which mixes the chyme and promotes close contact with digestive juices and absorbing cells

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6
Q

Which muscles are involved in segmentation

A

Longitudinal muscles which move materials back and forth to aid in mixing

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7
Q

Extrinsic control of GI tract

A

Sympathetic and parasympathetic nerves (vagus nerve in PS which is stimulated by smell, sight and taste of food)

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8
Q

Intrinsic control of GI tract

A

The enteric nervous system made up of the myenteric plexus and submucosal plexus

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9
Q

Role of the myenteric plexus

A

Largely motor in fucntion

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10
Q

Role of the submucosal plexus

A

Largely sensory in function

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11
Q

What is chemical digestion aided by

A

Digestive enzymes

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12
Q

What is chemical digestion regulated by

A

Hormones

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13
Q

What substances make up intestinal secretion

A

Enzymes, acid, base, bile, mucus

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14
Q

What are enzymes

A

Protein compounds which catalyse hydrolysis but are not altered in the process. They are compatible with a specific compound or nutrient, each has an optimal pH range and each has an optimal temperature

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15
Q

What type of acid is found where

A

HCl is found in the stomach

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16
Q

What type of base is found where

A

Bicarbonate is found in the small intestine

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17
Q

Where is bile produced

A

Liver

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18
Q

Where is bile stored

A

Gall bladder

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19
Q

What is hydrolysis

A

The cleavage of chemical bonds by the addition of water

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20
Q

What are proteins broken down into

A

Amino acids

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21
Q

What are carbohydrates broken down into

A

Monosaccharides

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22
Q

What are fats broken down into

A

Monoglycerides and free fatty acids

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23
Q

What is pH

A

The concentration of hydrogen ions in solution. The more H+ ions the more acidic, conversely the more OH- ions the more basic. Each enzyme functions best within a certain pH range.

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24
Q

Where does digestion occur

A

Mouth, stomach, small intestine, large intestine.

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25
Q

What is the role of teeth

A

Physical digestion

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26
Q

What is the role of saliva

A

Chemical digestion

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27
Q

What is the role of amylase

A

To break down starch into small sugar molecules (5%)

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28
Q

What is the role of lingual lipase

A

To break down fats, however this only happens in minuscule amounts

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29
Q

Where is lingual lipase secreted

A

von Ebner’s glands

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30
Q

Which enzymes are secreted in the mouth

A

Amylase and lingual lipase

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31
Q

What is found in gastric juice

A

Water, HCl, enzymes, hormones, intrinsic factor (B12) and rennin.

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32
Q

Which cells secrete HCl and where are they found

A

Parietal cells in the gastric pit

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33
Q

Where is mucus secreted and what is its function

A

Secreted near the cells and is an alkaline substance and so protects the stomach wall

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34
Q

Which enzymes are present in the stomach?

A

Pepsin and gastric lipase

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35
Q

Which cells secrete the stomach enyzmes

A

Chief cells

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36
Q

What is pepsinogen

A

An inactive form of the enzyme pepsin

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37
Q

What are the 3 roles of hydrochloric acid

A

To break down the connective tissue or muscles in meat.
To activate pepsinogen to form pepsin.
To act as a defence mechanism in killing micro-organisms

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38
Q

What is the role of rennin

A

To coagulate milk enabling the access of nutrients

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39
Q

Rennin is found in adults- true or false

A

False, it is important in newborns and isn’t found in adults

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40
Q

What substances are absorbed in the stomach

A

Only some lipid-soluble compounds and weak acids such as alcohol and asprin

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41
Q

What is found in the stomach

A

Gastric juice, mucus

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42
Q

What enters the small intestine

A

Chyme

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43
Q

What are the three parts of the small intestine

A

Duodenum, jejunum and ileum

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44
Q

How long is the duodenum

A

10-12 inches

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45
Q

How long is the jejunum

A

~4 feet

46
Q

How long is the ileum

A

~5 feet

47
Q

What features of the small intestine increase surface area

A

Circular folds -> villi -> microvilli

48
Q

What cells in the small intestine secrete fluid, and how much is secreted each day

A

Intestinal crypst cells secrete 1-2L of fluid each day

49
Q

What stimulates the intestinal crypst cells

A

Distension, chyme, vagal nerve activity, hormones

50
Q

What does the brunners glad in the SI secrete and what is the purpose of the secretion

A

The brunners glad secrete a bicarbonate rich fluid which neutralises chyme

51
Q

What do goblet cells in the SI do

A

Secrete mucus

52
Q

Which accessory organs does the SI need for digestion

A

Liver and pancreas

53
Q

Which three substances are digested in the SI

A

Protein, fat and carbohydrate

54
Q

What is role of bile

A

To emulsify fats and so break down fats into smaller fat goblets, increasing the surface area of fats. The increased surface area enhances enzyme breakdown of fats

55
Q

What is the function of bile salts

A

To attach to fat goblets making them hydrophilic (water soluble).

56
Q

What is bile made up of

A

Bile salts, bile pigment, cholesterol, phospholipids,, electrolytes.

57
Q

Which part of the SI is the site of pancreatic secretion

A

The duodenum

58
Q

Which pancreatic enzymes are secreted in the SI

A 
Pancreatic amylases (carbohydrates).
Pancreatic lipase (fats).
Trypsin, chymoptrypsin and carboxypeptidase (proteins).
59
Q

What is present in pancreatic secretions secreted in the SI

A

Pancreatic enzymes and bicarbonate

60
Q

What is the role of bicarbonate in the SI

A

To neutralise HCl from the stomach

61
Q

What does the conversion (joining) of the common bile duct and pancreatic duct result in

A

The release of pancreatic zymogens

62
Q

What are zymogens

A

Inactive forms of enyzmes

63
Q

Where are brush border enzymes secreted from

A

Enterocytes

64
Q

What is the function of brush border enzymes

A

To break the double bonds in sugars to form simple sugars

65
Q

Name 3 brush border enzymes found in adults

A

Sucrase, isomaltase, lactase

66
Q

Name a brush border enzyme only found in people less than 4 years old

A

Lactase

67
Q

Which two types of enzymes are present in the SI

A

Pancreatic and intestinal enzymes

68
Q

What substances are absorbed unchanged in the SI

A

Minerals, vitamins and cholesterol

69
Q

How much (%) absorption occurs in the SI

A

90%

70
Q

How is nutrients absorbed in the SI

A

Nutrients is trapped in the folds of the intestinal wall and absorbed through the microvilli

71
Q

What substances are absorbed in the duodenum and upper jejunum

A

Carbohydrates, amino acids, water-soluble vitamins and most minerals (except Na+, Cl-, K2+)

72
Q

What substances are absorbed in the jejunum

A

Lipids and fat-soluble vitamins

73
Q

What substances are absorbed in the terminal ileum

A

Vitamin B12

74
Q

Which two process are involved in the absorption of substances in the SI

A

Active transport and passive diffusion

75
Q

What is passive diffusion

A

When nutrients move from high to low concentration , no energy is required

76
Q

How is fat absorbed in the SI

A

Passive diffusion

77
Q

What is (secondary) active transport

A

When nutrients move from low to high concentration with the help of a carrier protien

78
Q

How are amino acids and monosaccharides absorbed in the SI

A

(Secondary) active transport

79
Q

In which vessels are substances from the SI transported to the liver

A

Hepatic portal vein or lymph

80
Q

Which nutrients are absorbed directly into the blood stream

A

Water-soluble nutrients

81
Q

How are fat-soluble compounds transported and why

A

In the lymph as they are too big to directly enter the blood

82
Q

Which two vessels does each villus contain

A

Blood vessels and lymph

83
Q

How do monosaccharides, amino acids and nucleotides cross the gut lining and where do they enter

A

Cross the gut lining by active transport and enter the bloodstream heading to the liver

84
Q

How do fatty acids and monoglycerides cross the gut lining and where do they enter

A

They diffuse into the gut epithelium before reforming and entering the lymphatic system

85
Q

How long is the large intestine

A

~5 feet long

86
Q

What is the LI comprised of

A

Cecum, colon, rectum and anal canal

87
Q

What is the function of bacteria in the LI

A

To digest small amounts of fibre

88
Q

What does the bacterial activity in the LI form

A

Vitamin K, vitamin B12, thiamin, riboflavin, biotin and gases

89
Q

What is absorbed in the LI

A

Water, sodium, potassium chloride, some vitamin K

90
Q

What happens to vitamin B12 in the LI

A

It is utilised by colonocytes

91
Q

What happens to the remaining materials that aren’t absorbed in the LI

A

They are eliminated via faeces

92
Q

What are the 4 GI hormones

A
  1. Gastrin
  2. Secretin
  3. Cholesytokinin (CCK)
  4. Gastric inhibitory peptide (GIP)
93
Q

What do the GI hormones influence

A

GI motility, stomach emptying, gall bladder contraction, intestinal absorption, hunger

94
Q

What is the release of GI hormones stimulated by

A

Passing of food through the digestive tract

95
Q

What does vagal stimulation (sight, smell, taste, distension of the stomach) stimulate

A

Gastrin secretion by the G cells of the stomach

96
Q

What does gastrin stimulate

A

Causes stomach cells to produce peptidases and HCl

97
Q

What and where is gastrin secreted

A

By the G cells in the stomach

98
Q

What and where is secretin secreted

A

By the S cells of the duodenal muscosa

99
Q

What causes the secretion of secretin

A

In response to acid

100
Q

What is the function of secretin

A

It inhibits the release of gastrin

101
Q

Which two hormones are released in response to the presence of the products of fat digestion

A

CCK and GIP

102
Q

What is the function of CCK and GIP

A

To inhibit the release of gastrin and gastric acid

103
Q

Describe the sequence of hormonal events stimulated regarding the secretion and entering the bloodstream of secretin and CCK

A
  1. Chyme enters the duodenum causing the duodenal mucosal cells to release secretin and CCK
  2. CCK and secretin enter the blood stream
  3. Upon reaching the pancrease CCK induces the secretion of pancreatic juice and secretin causes the secretion of bicarbonate-rich pancreatic juice
  4. Secretin causes the liver to secrete more bile, CCK stimulates the gall bladder to release stored bile
104
Q

Features of the stomach

A

Starts process of fat and protein digestion, little absorption, gastrin stimulates release of HCl and pesinogen

105
Q

Features of SI

A

site of most digestion and absorption, pancreatic and brush border enzymes, bile aids fat digestion, CCK secretin and GIP are released, absorption via diffusion/ active transport into circulation or lymph

106
Q

Features of LI

A

Little digestion (bacteria), little absorption (absorbs water, sodium, potassium chloride and some vit K)

107
Q

Name 4 GI disorders

A
  1. Gastrooesophageal reflux disease (GERD)
  2. Lactose intolerance
  3. Diarrhoea
  4. Constipation
108
Q

Gastrooesophageal reflux disease (GERD)

A

Incompetence of the lower oesophageal sphincter, allows reflux of gastric contents into oesophagus

109
Q

Lactose intolerance

A

Inability to digest lactose, deficiency of the enzyme lactase which leads to diarrhoea and cramping

110
Q

Diarrhoea

A

Even small reductions (1%) in intestinal water absorption/ increases in secretions can increase water content enough to cause diarrohea

111
Q

Constipation

A

Too much intestinal water absorption results in slow. reduced peristalsis.

112
Q

Which 2 GI disorders are related to water absorption

A

Diarrohea and constipation

bi0005 (21 decks)

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