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Physiology Flashcards

1
Q

From inner to outer, what are the 4 layers of a wall of the GI tract?

A

Mucosa, submucosa, muscularis externa, serosa

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2
Q

From inner to outer, what are the 5 layers of the mucosa?

A

Epithelial cells, exocrine cells, endocrine gland cells, lamina propria, muscularis mucosa

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3
Q

What is contained in the lamina propria?

A

Connective tissue, immune cells and capillaries

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4
Q

From inner to outer, what are the 4 layers of the submucosa?

A

Connective tissue, larger blood and lymph vessels, glands, submucus plexus

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5
Q

From inner to outer, what are the 3 layers of the muscularis externa?

A

Circular muscle layer, myenteric plexus, longitudinal muscle layer

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6
Q

What forms the serosa?

A

Connective tissue

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7
Q

Where is skeletal muscle found in the GI tract?

A

Mouth, pharynx, upper oesophageal and external anal sphincters

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8
Q

What happens upon circular muscle contraction?

A

Lumen becomes longer and narrower

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9
Q

What happens upon longitudinal muscle contraction?

A

Lumen becomes shorter and fatter

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10
Q

What happens upon contraction of the muscularis mucosae?

A

Changes in absorptive and secretory area of mucosae

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11
Q

What are adjacent smooth muscle cells coupled by?

A

Gap junctions

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12
Q

Spontaneous activity is generated by specialised pacemaker cells. What modifies these?

A

Enteric and autonomic nerves

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13
Q

What does electrical activity occur as in the stomach and intestines?

A

Slow waves

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14
Q

What are slow waves?

A

Rhythmic patterns of depolarisation and repolarisation which spread from cell to cell via gap junctions

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15
Q

What do slow waves determine?

A

Frequency, duration and velocity of rhythmic contractions

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16
Q

What are interstitial cells of Cajal?

A

Pacemaker cells interspersed between smooth muscle cells

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17
Q

More specifically, where are interstitial cells of Cajal found?

A

Between circular muscle and submucosa

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18
Q

What has to happen in order for contractions to occur?

A

Slow wave amplitude has to be sufficient

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19
Q

What in terms of action potentials, is force of contraction related to?

A

Number of action potentials produced

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20
Q

What factors determine whether slow waves reach potential or not?

A

Neuronal, hormonal or mechanical stimuli which act to depolarise smooth muscle cells

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21
Q

What does the myenteric plexus do?

A

Regulates motility and sphincters

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22
Q

What does the submucous plexus do?

A

Modulates epithelia and blood vessels

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23
Q

What are found in the myenteric and submucous plexus’?

A

Enteric nerves

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24
Q

What is the main autonomic influence of the GI tract?

A

Parasympathetic

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25
Q

What are parasympathetic excitatory influences?

A

Increased secretions, blood flow and smooth muscle contractions

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26
Q

What are parasympathetic inhibitory influences?

A

Relaxation of some sphincters and receptive relaxation of the stomach

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27
Q

What are sympathetic excitatory influences?

A

Increased sphincter tone

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28
Q

What are sympathetic inhibitory influences?

A

Decreased motility, secretion and blood flow

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29
Q

What is a local reflex in the GI tract?

A

Peristalsis

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30
Q

What is a short reflex in the GI tract?

A

Intestine-intestine inhibitory reflex

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31
Q

What is a long reflex in the GI tract?

A

Gastroilial reflex

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32
Q

What is a process which is known as haustration in the intestines, and involves mixing/churning ovements of the circular muscle layer?

A

Segmentation

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33
Q

What is colonic mass movement?

A

Powerful sweeping contraction which forces faeces into the rectum

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34
Q

What is a sweeping contraction from the stomach to terminal ileum?

A

Migrating motor complex

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35
Q

What does the upper oesophageal sphincter do?

A

Relaxes to allow swallowing and closes during inspiration

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36
Q

What does the lower oesophageal sphincter do?

A

Relaxes to permit food to enter the stomach and contracts to avoid reflux

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37
Q

What does the pyloric sphincter do?

A

Regulates gastric emptying

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38
Q

What opens and closes the ileocaecal valve?

A

Distension of ileum opens and distension of proximal colon closes

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39
Q

What are the anal sphincters regulated by?

A

Defaecation reflex

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40
Q

What afferent nerve impulses are sent to the pons and medulla at the start of the swallowing reflex?

A

CN IX and X

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41
Q

What efferent nerve impulses are sent to the skeletal muscles of the pharynx and larynx at the start of the swallowing reflex?

A

CN VII, IX, X, XI

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42
Q

What do the laryngeal muscles do during swallowing?

A

Close the glottis and raise larynx to inhibit ventilation

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43
Q

Where is the swallowing centre?

A

Pons and medulla

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44
Q

What nerve is involved in generated a primary peristaltic wave?

A

Vagus nerve

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45
Q

Where are the parotid glands?

A

Anterior to ear

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46
Q

Where does the parotid gland enter the mouth?

A

Above the 2nd maxillary molar

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47
Q

Where is the submandibular gland?

A

Medial to the body of the mandible

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48
Q

Where do the submandibular glands enter the mouth?

A

Under the tongue

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49
Q

Where are the sublingual glands?

A

Medial to the submandibular glands

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50
Q

Where do the sublingual glands enter the mouth?

A

Connect with the submandibular glands at the sublingual caruncula and enter under the tongue

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51
Q

What type of cells do the parotid glands have and what do they produce?

A

Serous cells producing a watery alpha amylase rich secretion

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52
Q

What type of cells do the submandibular glands have and what do they produce?

A

Mixed serous and mucous cells which produce a more viscous solution

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53
Q

What type of cells do sublingual glands have and what do they produce?

A

Mainly mucus cells producing a thick mucus

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54
Q

Are salivary glands endo or exocrine?

A

Exocrine

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55
Q

What is the functional unit of a salivary gland?

A

Salivon

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56
Q

What does a salivon consist of?

A

Secretory acinus, intercalated duct and striated duct

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57
Q

What do striated ducts combine to form?

A

Interlobular and excretory ducts

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58
Q

What type of cells surround the acinus of a salivary gland?

A

Contractile myoepithelial cells

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59
Q

What type of epithelium are intercalated ducts?

A

Cuboidal

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60
Q

What type of epithelium are striated ducts?

A

Columnar

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61
Q

What give striated ducts their appearance?

A

Infoldings between cells containing mitochondria

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62
Q

What are some functions of saliva?

A

Lubrication, protection, digestion, protective secretion prior to vomiting, facilitates suckling

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63
Q

What electrolytes are found in saliva?

A

Na+, K+, Ca++, Cl-, I-, PO4–, HCO3-

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64
Q

Which electrolytes are found at higher concentrations in saliva than in plasma?

A

K+ and HCO3-

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65
Q

What is the relationship between bicarbonate and rate?

A

Increases with rate

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66
Q

What is the relationship between K+ and rate?

A

Decreases with rate

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67
Q

What parasympathetic nerve acts on the sublingual and submandibular glands?

A

CN VII

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68
Q

What parasympathetic nerve acts on the parotid glands?

A

IX

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69
Q

What receptors are there a large volume of in the saliva?

A

Watery, enzyme rich M1/M3 acetylcholine receptors

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70
Q

What acts on sympathetic fibres in times of stress and where does this come from?

A

Adrenaline from adrenal medulla

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71
Q

What type of receptors are there a small volume of in saliva?

A

Mucus rich alpha and beta 1 adrenoceptors

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72
Q

What nerve relaxes the stomach?

A

Vagus

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73
Q

What is produced when the stomach mixes food with gastric acid?

A

Chime

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74
Q

How can the duodenum delay gastric emptying?

A

Neuronal response- decrease peristalsis

Hormonal response- inhibit stomach contraction

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75
Q

What factors cause delayed gastric emptying?

A

Fat, acid, hypertonicity and distension

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76
Q

What is secreted from the oxyntic mucosa?

A

HCl, pepsinogen, intrinsic factor, histamine, mucus

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77
Q

What is secreted from the pyloric gland area?

A

Gastrin, somatostatin, mucus

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78
Q

What 3 things does HCl do?

A

Activates pepsinogen to pepsin, kills bacteria ingested with food, denatures proteins

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79
Q

What is pepsinogen?

A

Inactive precursor of pepsin

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80
Q

What does intrinsic factor do?

A

Binds vitamin B12 to allow absorption in the terminal ileum

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81
Q

What does histamine do?

A

Stimulates HCl production

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82
Q

What does mucus do?

A

Protective

83
Q

What does gastrin do?

A

Stimulates HCl secretion

84
Q

What does somatostatin do?

A

Inhibits HCl secretion

85
Q

When does the cephalic stage of gastric secretion occur?

A

Before food reaches the stomach

86
Q

What happens in terms of production of molecules during the cephalic and gastric stage of gastric secretion?

A

Decreased somatostatin, increased ACh, histamine and gastrin

87
Q

When does the gastric stage of gastric secretion occur?

A

When food reaches the stomach

88
Q

When does the intestinal stage of gastric secretion occur?

A

After food has left the stomach

89
Q

What happens to somatostatin secretion as the stomach is emptied?

A

It is increased

90
Q

What are peptic ulcers?

A

Any ulcers where the mucosa is exposed to HCl and pepsin

91
Q

What protects the mucosa from attack of HCl and pesin?

A

Locally produced prostaglandins PGE2 and PGI2

92
Q

What do PGE2 and PGI2 do?

A

Reduce acid secretion, increase mucus and bicarbonate secretion and mucosal blood flow

93
Q

What reduces prostaglandin formation?

A

NSAIDs

94
Q

What does H. pylori secrete?

A

Agents causing inflammation which weakens the mucosal barrier and leaves the submucosa open to attack

95
Q

What are drugs that are used to reduce gastric acid secretion used for?

A

Peptic ulcers, GORD, acid hypersecretion

96
Q

What are sucralfate and bismuth chealate examples of?

A

Mucosal strengtheners

97
Q

What are the 3 main components of food?

A

Carbohydrates, lipids and proteins

98
Q

What are examples of carbohydrates?

A

Starch, glycogen, disaccharides, cellulose

99
Q

Which carbohydrate is indigestible?

A

Cellulose

100
Q

What are examples of lipids?

A

Triacylglycerols, phospholipids, cholesterol and fatty acids

101
Q

What is luminal digestion?

A

Digestion through pancreatic enzymes secreted into the duodenum

102
Q

What is membrane digestion?

A

Mediated by enzymes situated at the brush border of epithelial cells

103
Q

What happens to the absorbable products of digestion during absorption?

A

They are transferred across both the apical and basolateral borders of the enterocytes

104
Q

What are enterocytes?

A

Absorptive cells of intestinal epithelium

105
Q

What is assimilation?

A

Combined digestion and absorption

106
Q

What are digestible carbohydrates?

A

Polysaccharides, oligosaccharides and monosaccharides

107
Q

What are polysaccharides?

A

Glucose polymers joined by alpha 1,4 linkages

108
Q

What is an example of a straight glucose chain?

A

Amylase

109
Q

What is an example of a branched glucose chain?

A

Amylopectin

110
Q

Explain the structure of glycogen compared to amylase and amylopectin?

A

Similar but with a greater molecular weight and more branches

111
Q

What must all dietary carbohydrates be converted to for absorption?

A

Monosaccharides

112
Q

Which enzyme breaks down internal alpha 1,4 linkages but not terminal ones?

A

Alpha amylase

113
Q

Because of the way it works (not breaking terminal bonds) what can alpha amylase not produce?

A

Glucose

114
Q

What are the products of alpha amylase breakdown?

A

Glucose oligomers e.g. maltose

115
Q

What are integral membrane proteins with a catalytic domain which faces the lumen of the GI tract?

A

Oligosaccharides

116
Q

What does lactase do?

A

Breaks down lactose to glucose and galactose

117
Q

What are enzymes which convert oligosaccharides to monosaccharides known as?

A

Oligosaccharisases

118
Q

Apart from lactase, what do all other oligosaccharidases yield?

A

Glucose

119
Q

What can degrade alpha 1,4 linkages in straight chain oligomers up to 9 monomers in length?

A

Maltase

120
Q

What does sucrase do?

A

Hydrolyses sucrose to glucose and fructose

121
Q

What is the only enzyme which can split the branching alpha 1,6 linkages of alpha limit dextrins?

A

Isomaltase

122
Q

What are monosaccharides which can be absorbed?

A

Glucose, fructose, galactose

123
Q

What is primary lactose intolerance?

A

A genetic cause

124
Q

What is secondary lactose intolerance?

A

Caused by damage to/infection of the proximal small intestine

125
Q

What is congenital lactose intolerance?

A

Rare autosomal recessive disease

126
Q

What can it cause if lactose is eaten in someone who is lactose intolerant?

A

Bloating, abdominal pain and flatulence

127
Q

What can undigested lactose cause?

A

Acidification of the colon and increased osmotic load

128
Q

Where does absorption of final monosaccharides take place?

A

Duodenum and jejunum

129
Q

How are glucose and galactose absorbed?

A

Secondary active transport mediated by SGLT1

130
Q

How is fructose absorbed?

A

Facilitated diffusion mediated by GLUT5

131
Q

What is the exit out of enterocytes for all monosaccharides?

A

Facilitated diffusion by GLUT2

132
Q

What other transporter is expressed in enterocytes?

A

GLUT1

133
Q

What must proteins be broken down into for efficient absorption?

A

Oligopeptides and amino acids

134
Q

How many different pathways can be used for protein breakdown?

A

4

135
Q

What does pepsin do to proteins?

A

Cleaves them into peptides

136
Q

What are the endopeptidases secreted as proenzymes from the exocrine pancreas to be converted to the active form in the duodenum?

A

Trypsin, chymotrypsin, elastase

137
Q

What does digestion by endopeptidases produce?

A

Oligopeptides 2-6 amino acids long

138
Q

What are the exopeptidases secreted as proenzymes from the exocrine pancreas to be converted to the active form in the duodenum?

A

Procarboxypeptidase A and B

139
Q

What does digestion by exopeptidases produce?

A

Single amino acids

140
Q

Peptidases found where are numerous and have affinity for larger oligopeptides?

A

Brush border

141
Q

Peptidases found where are less numerous and primarily hydrolyse di and tripeptides?

A

Cytoplasm

142
Q

Where are amino acids absorbed?

A

Brush border and basolateral membrane

143
Q

What transporters for moving protein breakdown products out of the brush border are present?

A

7 different mechanisms- 5 Na+ dependent co-transporters (secondary active transport) and 2 Na+ independent

144
Q

In the basolateral membrane there are 5 different mechanisms of moving protein breakdown products, what are these?

A

2 Na+ dependent and mediate influx of amino acids, 3 Na+ independent and mediate efflux of amino acids

145
Q

What are fats?

A

Long chain fatty acyl esters of glycerol

146
Q

What is formed when heat and movements mix foods with gastric lipase?

A

An emulsion

147
Q

What does pancreatic lipase do in the small intestine?

A

Hydrolyses triacylglycerols to 2 x monoglycerides and 2 x free fatty acids

148
Q

What aids the action of pancreatic lipase?

A

Bile salts from the gallbladder

149
Q

What is formed when a triglyceride is broken down by gastric lipase?

A

Diglyceride and free fatty acid

150
Q

What does the free fatty acid produced by breakdown with gastric lipase stimulate release of?

A

CCK from duodenum and pancreatic lipase

151
Q

How are short and medium chain fatty acids absorbed?

A

Diffusion through the enterocyte to enter the villus capillaries

152
Q

How are long chain fatty acids and monoglycerides absorbed?

A

Resynthesised to triglycerides in the ER and incorporated into chylomicrons

153
Q

What are chylomicrons?

A

Small fat globules which transport lipids from the intestines to other body sites

154
Q

Triglycerides in chylomicrons are released by exocytosis into where?

A

Lymphatic system to enter the systemic system at the subclavian vein

155
Q

Chylomicron triglycerides are metabolised in capillaries by what?

A

Lipoprotein lipase present on endothelial cells

156
Q

What do free fatty acids and glycerol bind to to be taken up by tissues?

A

Albumin

157
Q

Where is cholesterol from chylomicrons released?

A

Secreted unaltered in bile to be stored or oxidised to bile salts

158
Q

What is albumin?

A

The dominant carrier of lipids in blood

159
Q

What is ezetimibe?

A

A drug which binds to a transporter and prevents cholesterol absorption and is sometime used alongside statins

160
Q

What type of transport is generally used in absorption of Ca++ in chime?

A

Active

161
Q

What mediates Ca++ absorption from chime?

A

Dihydroxyvitamin D3 and parathyroid hormone

162
Q

What is iron an important constituent of?

A

Haemoglobin, myoglobin and any haem containing enzymes

163
Q

What does transport of iron take place through?

A

Divalent metal transporter 1 and haem carrier protein 1

164
Q

What is a hormone released from the liver which controls iron absorption?

A

Hepcidin

165
Q

What are examples of fat soluble vitamins?

A

A, D, E, K

166
Q

What do fat soluble vitamins require to be absorbed?

A

Adequate bile secretion and intact intestinal mucosa

167
Q

How are fat soluble vitamins transported into enterocytes?

A

Passively in mixed micelles

168
Q

How are fat soluble vitamins distributed?

A

By intestinal lymphatics

169
Q

What are water soluble vitamins?

A

B, C and H

170
Q

What transporters do water soluble vitamins use to be absorbed?

A

Na+ dependent or independent transporters

171
Q

Why does vitamin B12 require specially effective absorption?

A

It is present in minute amounts in the diet

172
Q

What is energy homeostasis?

A

Energy intake is matched to energy expenditure over time

173
Q

What has a mismatch in energy homeostasis over time led to?

A

Obesity

174
Q

What other things can obesity cause?

A

Metabolic syndrome, dyslipidaemia, type 2 diabetes and insulin resistance, cardiovascular disease

175
Q

What are the main factors influencing obesity?

A

Genetics and environment

176
Q

What do we need fat for?

A

Energy storage, energy buffer during prolonged illness and prevention of starvation

177
Q

How does the CNS influence energy balance and body weight?

A

Behaviour (exercise/feeding), ANS activity, neuroendocrine secretions

178
Q

Where is the site of integration of CNS mechanisms controlling energy balance and body weight and what neural centre is responsible?

A

Site of integration in the brain, neural centre is hypothalamus

179
Q

What is satiation?

A

The feeling of fullness generated during a meal

180
Q

What is satiety?

A

The time between the termination of one meal and initiation of the next

181
Q

What is a satiation signal which is secreted from enteroendocrine cells in the duodenum and jejunum and signals via sensory nerves to the hindbrain?

A

Cholecystokinin (CCK)

182
Q

What satiation signal is secreted from the endocrine mucosal L cells of the GI tract?

A

Peptide YY

183
Q

What does peptide YY do?

A

Slows gastric emptying, inhibits gastric motility and reduces food intake

184
Q

What are satiation signals which are products of the pro-glucagon gene?

A

Glucagon like peptide and oxyntomodulin

185
Q

What does oxyntomodulin do?

A

Suppresses appetite

186
Q

What is ghrelin?

A

A hunger signal

187
Q

Where is ghrelin produced?

A

Oxyntic cells in the stomach

188
Q

What raises levels of ghrelin?

A

Fasting and hypoglycaemia

189
Q

What are the two main adiposity signals in humans?

A

Insulin and leptin

190
Q

Where is leptin made and released?

A

Fat cells

191
Q

Where is insulin made and released?

A

Pancreatic cells

192
Q

What does reduced leptin cause?

A

It mimics starvation and causes unrestrained appetite

193
Q

What are some roles of leptin?

A

Food intake and fat deposition, glucose homeostasis and insulin sensitivity, maintenance of reproductive/immune systems, angiogenesis, tumourigenesis

194
Q

What is food reward?

A

The pleasure derived from eating

195
Q

What pathways are involved in food reward?

A

Dopamine

196
Q

What limits the use of leptin as an obesity therapy?

A

Resistance

197
Q

What causes leptin resistance?

A

Defective transport to the brain or altered signal transduction following leptin binding to its receptor

198
Q

What is the present obesity drug?

A

Orlistat

199
Q

What does orlistat do?

A

Inhibits pancreatic lipase and decreases triglyceride absorption

200
Q

What are side effects of orlistat?

A

Cramping and diarrhoea

201
Q

What is liraglutide?

A

Glucagon like receptor antagonist used in treatment of type 2 diabetes

202
Q

What is the only way to produce sustainable weight loss medically?

A

Bariatric surgery

203
Q

What does brown adipose tissue do?

A

Produces heat after eating to get rid of energy

GI (17 decks)

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