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Flashcards in Digestion and Absorption 1 Deck (112):
1

What are the General Functions of the GI Tract

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

2

Physical Processes of Digestion

Chewing, peristalsis, segmentation

3

What is Peristalsis

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

4

Which muscles are involved in peristalsis

Circular muscles which give alternating waves of contraction

5

What is segmentation

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

6

Which muscles are involved in segmentation

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

7

Extrinsic control of GI tract

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

8

Intrinsic control of GI tract

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

9

Role of the myenteric plexus

Largely motor in fucntion

10

Role of the submucosal plexus

Largely sensory in function

11

What is chemical digestion aided by

Digestive enzymes

12

What is chemical digestion regulated by

Hormones

13

What substances make up intestinal secretion

Enzymes, acid, base, bile, mucus

14

What are enzymes

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

15

What type of acid is found where

HCl is found in the stomach

16

What type of base is found where

Bicarbonate is found in the small intestine

17

Where is bile produced

Liver

18

Where is bile stored

Gall bladder

19

What is hydrolysis

The cleavage of chemical bonds by the addition of water

20

What are proteins broken down into

Amino acids

21

What are carbohydrates broken down into

Monosaccharides

22

What are fats broken down into

Monoglycerides and free fatty acids

23

What is pH

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.

24

Where does digestion occur

Mouth, stomach, small intestine, large intestine.

25

What is the role of teeth

Physical digestion

26

What is the role of saliva

Chemical digestion

27

What is the role of amylase

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

28

What is the role of lingual lipase

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

29

Where is lingual lipase secreted

von Ebner's glands

30

Which enzymes are secreted in the mouth

Amylase and lingual lipase

31

What is found in gastric juice

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

32

Which cells secrete HCl and where are they found

Parietal cells in the gastric pit

33

Where is mucus secreted and what is its function

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

34

Which enzymes are present in the stomach?

Pepsin and gastric lipase

35

Which cells secrete the stomach enyzmes

Chief cells

36

What is pepsinogen

An inactive form of the enzyme pepsin

37

What are the 3 roles of hydrochloric acid

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

38

What is the role of rennin

To coagulate milk enabling the access of nutrients

39

Rennin is found in adults- true or false

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

40

What substances are absorbed in the stomach

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

41

What is found in the stomach

Gastric juice, mucus

42

What enters the small intestine

Chyme

43

What are the three parts of the small intestine

Duodenum, jejunum and ileum

44

How long is the duodenum

10-12 inches

45

How long is the jejunum

~4 feet

46

How long is the ileum

~5 feet

47

What features of the small intestine increase surface area

Circular folds -> villi -> microvilli

48

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

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

49

What stimulates the intestinal crypst cells

Distension, chyme, vagal nerve activity, hormones

50

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

The brunners glad secrete a bicarbonate rich fluid which neutralises chyme

51

What do goblet cells in the SI do

Secrete mucus

52

Which accessory organs does the SI need for digestion

Liver and pancreas

53

Which three substances are digested in the SI

Protein, fat and carbohydrate

54

What is role of bile

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

What is the function of bile salts

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

56

What is bile made up of

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

57

Which part of the SI is the site of pancreatic secretion

The duodenum

58

Which pancreatic enzymes are secreted in the SI

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

59

What is present in pancreatic secretions secreted in the SI

Pancreatic enzymes and bicarbonate

60

What is the role of bicarbonate in the SI

To neutralise HCl from the stomach

61

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

The release of pancreatic zymogens

62

What are zymogens

Inactive forms of enyzmes

63

Where are brush border enzymes secreted from

Enterocytes

64

What is the function of brush border enzymes

To break the double bonds in sugars to form simple sugars

65

Name 3 brush border enzymes found in adults

Sucrase, isomaltase, lactase

66

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

Lactase

67

Which two types of enzymes are present in the SI

Pancreatic and intestinal enzymes

68

What substances are absorbed unchanged in the SI

Minerals, vitamins and cholesterol

69

How much (%) absorption occurs in the SI

90%

70

How is nutrients absorbed in the SI

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

71

What substances are absorbed in the duodenum and upper jejunum

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

72

What substances are absorbed in the jejunum

Lipids and fat-soluble vitamins

73

What substances are absorbed in the terminal ileum

Vitamin B12

74

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

Active transport and passive diffusion

75

What is passive diffusion

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

76

How is fat absorbed in the SI

Passive diffusion

77

What is (secondary) active transport

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

78

How are amino acids and monosaccharides absorbed in the SI

(Secondary) active transport

79

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

Hepatic portal vein or lymph

80

Which nutrients are absorbed directly into the blood stream

Water-soluble nutrients

81

How are fat-soluble compounds transported and why

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

82

Which two vessels does each villus contain

Blood vessels and lymph

83

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

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

84

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

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

85

How long is the large intestine

~5 feet long

86

What is the LI comprised of

Cecum, colon, rectum and anal canal

87

What is the function of bacteria in the LI

To digest small amounts of fibre

88

What does the bacterial activity in the LI form

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

89

What is absorbed in the LI

Water, sodium, potassium chloride, some vitamin K

90

What happens to vitamin B12 in the LI

It is utilised by colonocytes

91

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

They are eliminated via faeces

92

What are the 4 GI hormones

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

93

What do the GI hormones influence

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

94

What is the release of GI hormones stimulated by

Passing of food through the digestive tract

95

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

Gastrin secretion by the G cells of the stomach

96

What does gastrin stimulate

Causes stomach cells to produce peptidases and HCl

97

What and where is gastrin secreted

By the G cells in the stomach

98

What and where is secretin secreted

By the S cells of the duodenal muscosa

99

What causes the secretion of secretin

In response to acid

100

What is the function of secretin

It inhibits the release of gastrin

101

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

CCK and GIP

102

What is the function of CCK and GIP

To inhibit the release of gastrin and gastric acid

103

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

1. Chyme enters the duodenum causing the duodenal mucosal cells to release secretin and CCK
2. CCK and secretin enter the blood stream
4. 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

Features of the stomach

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

105

Features of SI

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

Features of LI

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

107

Name 4 GI disorders

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

108

Gastrooesophageal reflux disease (GERD)

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

109

Lactose intolerance

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

110

Diarrhoea

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

111

Constipation

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

112

Which 2 GI disorders are related to water absorption

Diarrohea and constipation