Digestive System Flashcards

1
Q

What is the alimentary tract?

A

Tube extending from mouth to anus

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2
Q

Describe structure of alimentary tract

A

Muscular tube lined internally with epithelium

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3
Q

What is the function of alimentary tract

A

Ingestion, processing, digestion, absorption + excretion

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4
Q

What is the sequence of the digestive system?

A

Mouth —> pharynx —> oesophagus —> stomach —> small intestine —> large intestine —> anus

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5
Q

What is the pathway that food takes?

A

Oral cavity –> pharynx –> epiglottis –> oesophagus –> stomach –> duodenum –> jejunum –> ileum –> caecum –> ascending colon –> transverse colon –> descending colon –> sigmoid colon –> rectum –> anus

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6
Q

What is mucosa?

A

Type of epithelium

Moistened by glandular secretion

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7
Q

Describe structure of lamina propria

Mucosa

A

Loose connective tissue
Small blood vessels, lymphatics + nerve fibres
Immune cells

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8
Q

Describe structure of muscularis mucosa

A

Thin muscle layer

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9
Q

What is the submucosa?

A

2nd layer of loose connective tissue

Between mucosa + main muscle layers

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10
Q

Describe structure of submucosa

A

Blood vessels, lymphatic vessels

Neural tissue - submucosa plexus

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11
Q

What does the submucosa plexus do?

A

Regulates contractions + glandular secretions

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12
Q

What is the muscularis externa?

A

Smooth muscle typically divided into 2 layers

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13
Q

What are the 2 layers of the muscularis externa?

A
Inner = circular layer
Outer = longitudinal layer
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14
Q

Why is it significant the muscularis externa have different layers?

A

Orientate in different directions

= contractions propel materials along tract

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15
Q

What is located between muscle layers in muscularis externa?

A

2nd nerve plexus

= myenteric plexus

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16
Q

What is the adventitia/serosa?

A

Covers muscularis externa

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17
Q

Describe alimentary canal position

A

Suspended in peritoneal cavity, covered in serosa

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18
Q

What are retroperitoneal organs covered in?

A

Adventitia NOT serosa

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19
Q

What is the oral cavity lined with?

A

Stratified squamous epithelium

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20
Q

What is function of oral cavity?

A

Ingestion + fragmentation of food

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21
Q

What is found in the oral cavity?

A

Salivary glands

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22
Q

Where are the salivary glands within the oral cavity?

A

Submucosa

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23
Q

What are the three salivary glands?

A

Sublingual
Submandibular
Parotid

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24
Q

What is the sublingual salivary gland?

A

Beneath tongue, many ducts

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25
Q

What is the submandibular salivary gland?

A

Floor of mouth, inner surface of mandible, ducts behind teeth

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26
Q

What is the parotid salivary gland?

A

Largest, empties at the molar

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27
Q

What is oral drug administration?

A

Given by mouth + swallowed

Easiest + safest BUT slow absorption

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28
Q

What is sublingual drug adminstration?

A

Placed under tongue - dissolves in saliva

Rapid absorption, high circulating levels

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29
Q

What is sublingual drug administration not used for?

A

Bad-tasting or irritating medications

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30
Q

What is buccal drug administration?

A

Placed in mouth next to cheek

Rapid absorption, high circulating levels

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31
Q

What is disadvantage of buccal drug administration?

A

Swallow pill

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32
Q

Describe mucosa in oesophagus

A

Above diaphragm = stratified squamous epithelium

Below = columnar epithelium

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33
Q

What is the mucosa in oesophagus?

A

Define lamina propria + muscularis

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34
Q

Describe muscularis externa in oesophagus

A

Striated muscle in upper 1/3

Smooth lower 1/3

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35
Q

What does muscle do in oesophagus?

A

Contract rhythmically towards stomach

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36
Q

What does the lower oesophagus sphincter prevent?

A

Reflux, emesis + regurgitation

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37
Q

What is involved in the lower digestive tract?

A

Stomach
Small intestine
Large intestine

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38
Q

How is the efficiency of absorption improved?

A

By increasing SA between epithelium + lumen

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39
Q

How is the SA increased?

A

Intrusions/folding
Inversions
Formation complex glands

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40
Q

What is the function of the stomach?

A

Reservoir + digestion

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41
Q

What does the stomach do?

A

Mixes food with gastric juices to form semifluid mass called chyme

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42
Q

How does stomach initiate protein breakdown + absorption of vitamin B12?

A

Release of intrinsic factor

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43
Q

What are the 4 anatomical regions of the stomach?

A

Cardia (closest to heart)
Fundus (upper area)
Body (middle portion)
Pylorus (narrow bottom)

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44
Q

Describe structure of gastric mucosa?

A

Columnar epithelium
Mucosa folded
Shallow depression on surface
Entire mucosa has simple tubular gastric glands

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45
Q

What do the cardiac gland do?

A

Mucus producing gland

Provide alkaline layer

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46
Q

What are the 4 cell types of corpus-fundic gland?

A

Chief cells
Parietal cells
Mucous neck cells
Endocrine cells

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47
Q

What do chief cells produce?

A

Pepsinogen
Gastric lipase
Chymosin

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48
Q

What do parietal cells produce?

A

Gastric acid

Intrinsic factor

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49
Q

What do endocrine cells do?

A

Stimulate secretion of other cell types

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50
Q

What do pyloric glands contain?

A

Endocrine cells, NO chief cells

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51
Q

What are the gastric glands?

A

Cardiac gland
Corpus-fundic gland
Pyloric gland

52
Q

What are the disorders of the stomach?

A
Achlorhydria 
Dyspepsia
Gastritis 
Gastroenteritis 
Haematemesis
Hiatal hernia
53
Q

What is achlorhydria ?

A

Lack of gastric acid in the stomach

54
Q

What is dyspepsia?

A

Difficulty digesting food

55
Q

What is gastritis?

A

Stomach inflammation

56
Q

What is gastroenteritis ?

A

Inflammation of stomach + small intestine

57
Q

What is haematemesis?

A

Vomiting of blood

58
Q

What is hiatal hernia?

A

Protrusion of stomach through opening in diaphragm

59
Q

What is the small intestine made up of?

A

Duodenum
Jejunum
Ileum

60
Q

What does the pancreatic + bile duct empty into?

A

Duodenum

61
Q

What is present in mucosa of small intestine?

A
Plicae 
Microvilli 
Tubular glands 
Goblet cells 
Intestinal villi
62
Q

What does the plicae do?

A

Folds mucosa + submucosa

63
Q

Describe plicae in small intestine

A

Permanent structures

Absent from start of duodenum + distal ileum

64
Q

What is the intestinal villi?

A

Entire intestine mucosa

65
Q

What does the intestinal villi do?

A

Increase SA by x10

66
Q

What is the main cell type for intestinal villi + why?

A

Enterocyte

= absorptive function

67
Q

What cells are the microvilli?

A

Enterocytes

68
Q

What does the microvilli do?

A

Increase SA by x20

69
Q

Where are the tubular glands in small intestine?

A

From base of villi through lamina propria to muscularis mucosa

70
Q

What do tubular glands do?

A

Secrete intestinal juices

71
Q

What cells in tubular glands + why?

A

Paneth cells at base of crypt

= secretion + control of infection

72
Q

Describe small intestine

A

Rich blood supply

Large absorption SA

73
Q

Describe absorption in small intestine

A

Secretin released upon appearance of chyme in small intestine, stimulates release of bicarbonate to neutralise chyme

74
Q

Describe what happens in duodenum

A

Carbohydrates broken down into simple sugars
Proteins broken down
Fats emulsified by bile salts = fatty acids + monoglycerides by pancreatic lipase
Form micelles

75
Q

Describe what happens in jejunum

A

Monosaccharides, amino acids absorbed

H2O soluble vitamins, fat soluble vitamins

76
Q

Describe what happens in ileum

A

Bile salts reabsorbed

Vitamin B12 absorbed

77
Q

What is the main sections of the large intestine?

A

Caecum (including appendix)
Colon
Rectum

78
Q

What are the external + internal sphincter of large intestine under?

A

Voluntary control

79
Q

What is the large intestine primarily involved in?

A

Absorption of fluids + electrolytes
Secretion of electrolytes
Formation, storage + periodic elimination of faeces

80
Q

Describe structure of the large intestine

A
Columnar epithelium
Mucosal layer thicker
Surface relatively smooth
Crypts of Lieberkühn
Goblet cells more numerous
81
Q

Why is large intestine surface relatively smooth?

A

No plicae or villi

82
Q

Why is there bacteria in large intestine?

A

Synthesise vitamin K + B

83
Q

Describe what happens in defecation

A
Faeces enters rectum
Rectum dilates, stimulating mass peristalsis 
Levator ani muscle relaxes
Internal + external sphincter relax 
Anus pulled up over faecal mass
Faecal mass expelled
84
Q

Describe absorption of H2O in GI tract

A

Passive process driven by transport of solutes

H2O ingested + secreted in balance with H2O absorbed

85
Q

What does an antacid do?

A

Neutralise stomach acid

86
Q

What does an antidiarrheal do?

A

Control loose stool

87
Q

What does an antipasmodic do?

A

Calms GI spasms

88
Q

What does an antiemetic do?

A

Prevents regurgitation

89
Q

What does an cathartic do?

A

Causes vomiting or relieves constipation

90
Q

What does an laxative do?

A

Relieves constipation

91
Q

Describe the pancreas

A

Retroperitoneal

92
Q

What is the functionality of the pancreas?

A

Exocrine + endocrine

93
Q

What does the endocrine function of the pancreas do?

A

Islets produce insulin + glucagon

94
Q

What does the exocrine function of the pancreas do?

A

Glandular secretion of digestive enzymes

95
Q

What digestive enzymes are secreted by the pancreas?

A
Trypsin
Chymotrypsin 
Carboxypeptidase 
Pancreatic amylase 
Pancreatic lipase
96
Q

What is the endocrine pancreas?

A

Islets of Langerhans

97
Q

What are 4 main cell types in endocrine pancreas?

A

β-cells - secrete insulin
Alpha-cells secrete glucagon
Other - secrete somatostatin
PP/F cells - secrete pancreatic polypeptides

98
Q

What do β-cells do?

A

Stimulate glycogen, protein + fatty acid synthesis

Facilitate glucose uptake, lower blood glucose

99
Q

What is somatostatin?

A

Locally actin hormone, inhibits other endocrine cells

100
Q

What do PP/F cells do?

A

Stimulate gastric chief cells, inhibit bile secretion

Inhibit pancreatic exocrine function

101
Q

What does the exocrine pancreas do?

A

Pancreatic juice secreted by acini

102
Q

What is pancreatic juice?

A

Clear isosmotic alkaline fluid containing digestive enzyme precursors

103
Q

What does cholecystokinin (CCK) induce?

A

Enzyme-rich secretion from acini

104
Q

What does secretin cause?

A

HCO3- rich ductal cell secretion

105
Q

What are the pancreatic enzymes?

A

Amylase
Lipase
Proteases

106
Q

What is the max activity of amylase + what does it require?

A

pH 7

Require bicarbonate acid neutralisation

107
Q

What does amylase do?

A

Hydrolyse complex carbohydrates

108
Q

What is the max activity of lipase?

A

pH 7-9

109
Q

What does lipase do?

A

Emulsify + hydrolyse fats in presence of bile salts

110
Q

What are proteases secreted as?

A

Proenzymes

111
Q

What are proteases activated within?

A

Activated in proteolytic cascade within duodenum

112
Q

What does the secretion of somatostatin do?

A

Increase blood glucose
Increase blood amino acids
Increase blood fatty acids
Increase conc of upper GI hormones

113
Q

Where does somatostatin act?

A

Acts locally within endocrine pancreas to depress insulin + glucagon secretion

114
Q

What is glucagon produced by?

A

Alpha cells of endocrine pancreas

115
Q

What do glucagon prevent?

A

Hypoglycaemia by elevating blood glucose levels

116
Q

What is glucagon stimulated by?

A

Cholinergic system, beta-sympathetic fibres

117
Q

What is glucagon inhibited by?

A

Glucose, insulin somatostatin + alpha-sympathetic fibres

118
Q

What does insulin have a direct effect on?

A

Carbohydrates, fats + protein metabolism

119
Q

What is insulin degraded by?

A

Insulinase in liver

120
Q

What is cellular activity of insulin controlled by?

A

Insulin receptors

121
Q

What do the majority of cells respond to insulin for?

A

Glucose uptake

122
Q

What happens if there is a low glucose level?

A

Decreases brain activity

123
Q

What happens if there is a high glucose level?

A

Osmotic H2O loss, damaged blood vessels, organ disfunction

124
Q

What are the effects of insulin?

A

Alters phosphorylation of metabolic enzymes

Alter protein synthesis + gene transcription

125
Q

What effect does insulin have on the muscle?

A

Inhibition of glycogenolysis + stimulation of glycogenesis

Uptake of glucose + immediate use of storage as glycogen

126
Q

What effect does insulin have on the liver?

A

Inhibition of glycogenolysis, stimulation of glycogenesis, activation glycogen synthase
Decease gluconeogenesis, stimulation of phosphofructokinase
Inhibition of hepatic ketone formation
Stimulation of amino acid uptake + protein synthesis
Inhibition of protein degradation
Uptake of glucose + storage of glycogen

127
Q

What effect does insulin have on adipose tissue?

A

Promotes glucose uptake + conversion to glycerol for fat production
Stimulation of fat deposits + inhibition of lipolysis in adipose tissue