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Gastrointestinal > Alimentary Canal Physiology Pt.1 > Flashcards

Alimentary Canal Physiology Pt.1 Flashcards

1
Q

What is the digestive system

A

It is a system made up of the GIT and accessory organs

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2
Q

Names path of food going through the GIT

A

Oesophagus
Stomach
Duodenum
Jejunum
Ileum
Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anus

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3
Q

Name the accessory organs in the alimentary canal

A

salivary glands
liver
pancreas
gallbladder

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4
Q

What are the 4 main functions of the digestive system

A

digestion
absorption
secretion
motility

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5
Q

Is lumen of the GIT considered external or internal to the body

A

external

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6
Q

What is the function of the mouth

A

Foodstuffs broken down by chewing
saliva added as lubricant

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7
Q

What is the function of the oesophagus

A

Conduit between mouth and stomach

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8
Q

What is the function of the stomach

A

Digestion of proteins
foodstuffs reduced to semi-liquid form
storage
sterilisation

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9
Q

What is the function of the pancreas

A

Digestive enzymes for digestion of fats, carbohydrates and proteins

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10
Q

What is the function of the liver

A

Bile salts for digestion/absorption of fats in small intestine

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11
Q

What is the function of the gallbladder

A

Stores and concentrates bile

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12
Q

What is the function of the small intestines

A

Final stages of chemical digestion and nutrient absorption

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13
Q

What is the function of the large intestines

A

Water absorption
bacterial fermentation
formation of faeces

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14
Q

What are the four layers (tunics) of the GIT

A

Mucosa
Sub mucosa
Muscularis externa
Serosa/adventitia

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15
Q

What are the 3 layers of the mucosa and functions

A

Epithelium - lining of GIT (protection), Synthesis and secretion of digestive enzymes, hormones, mucus, absorbs products of digestion (function changes through out the tract
Lamina propria - loose connective tissue containing glands, blood and lymph vessels
Muscularis mucosae - thin layer of smooth muscle

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16
Q

What structures are found in the sub mucosa

A

connective tissue
neurones (sub mucosal plexus), blood vessels
glands in oesophagus and duodenum

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17
Q

What are the layers of the muscularis externa

A

Oblique muscle (in stomach)
circular muscle (constricts lumen)
longitudinal muscle (shortens tube)

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18
Q

What two plexus’s makes up the ENS and where are they found

A

Myenteric (Auerbach’s) plexus - found between longitudinal and circular muscle
Sub mucosal (Meissner’s) plexus - found between the circular muscle and submucosa

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19
Q

What is the difference between serosa and adventitia

A

Adventitia is found out with the peritoneal cavity eg. oesophagus, rectum
Serosa is found within the peritoneal cavity eg. stomach, small intestines, large intestines

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20
Q

What type of tissue is serosa

A

Connective tissue

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21
Q

Are long and short reflexes parasympathetic or ENS

A

Long - parasympathetic
short - ENS

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22
Q

Which parasympathetic nerves innervate the GIT

A

Vagus (X)
salivary glands - facial (VII) + glossopharyngeal (IX)

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23
Q

What is the effect of parasympathetic innervation on the GIT

A

Stimulatory
- increased secretion
- increased motility

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24
Q

Which sympathetic nerves innervate the GIT

A

Splanchnic nerves

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25
Q

What is the effect of sympathetic innervation on the GIT

A

Inhibitory (except salvation)
- decrease secretion
- decreased motility

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26
Q

What are the
- 3 abdominal branches of the aorta
- their vertebral level
- which organs do they supply

A

Coeliac trunk (T12) - foregut
Superior mesenteric artery (L1) - midgut
Inferior mesenteric artery (L3) - hindgut

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27
Q

What are the 3 main branches of the coeliac trunk

A

Splenic artery
Left gastric artery
Common hepatic artery

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28
Q

What veins drain the GIT

A

Gastric vein
Splenic vein
Superior mesenteric vein
Inferior mesenteric vein

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29
Q

Where does venous drainage of GIT go

A

Hepatic portal vein => Hepatic vein => IVC

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30
Q

Why do we chew our food

A

Prolong tasting experience
Defence against respiratory failure

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31
Q

Is chewing involuntary or voluntary
Which nerves are used

A

Voluntary
Somatic nerves of skeletal muscle in jaw/mouth

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32
Q

How many salivary glands do we have

A

3 pairs
Sublingual glands
Submandibular glands
Parotid glands

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33
Q

What is in saliva
What is its function

A

Water - solvent
Mucins - added to water -> mucus
alpha amylase - breaks down polysaccharides
Electrolytes - tonicity/pH
Lysozymes - bactericidal

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34
Q

What do serious alveoli produce

A

Alpha amylase and lysosomes

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35
Q

What do mucous alveoli produce

A

Mucins

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36
Q

Histologicially, what are salivary glands similar to

A

Pancreatic cells

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37
Q

Is stimulation of salivary glands sympathetic or parasympathetic

A

Both

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38
Q

What is the difference between salivary glands stimulation in sympathetic and parasympathetic

A

Sympathetic
- small volume of viscous secretion
- high mucous content (a1 adrenoreceptors)
- high amylase content (B2 adrenoreceptors)

Parasympathetic
- watery salivary secretion

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39
Q

Which parasympathetic nerves stimulate salivary glands

A

Facial (VII) nerves
Glossopharyngeal (IX) nerves

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40
Q

Does the oesophagus have skeletal or smooth muscle

A

Upper 1/3 - skeletal muscle
Lower 2/3 - smooth muscle

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41
Q

How many phases of swallowing are there

A

3 phases
Oral
Pharyngeal
Oesophagus

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42
Q

When swallowing why does the soft palate reflect backwards and upwards

A

Stops food going in to the nasopharynx

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43
Q

Why does the epiglottis cover larynx during swallowing

A

Prevents food from entering the trachea

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44
Q

What propels bolus (food) down the oesophagus

A

Peristaltic wave

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45
Q

How many oesophageal sphincters are there

A

2 sphincters
Upper oesophageal sphincter
Lower oesophageal sphincter

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46
Q

What is the stomach volume
How does the pressure change

A

50ml -> 1500ml
No change in pressure

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47
Q

What is the function of the stomach fundus

A

Storage

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48
Q

What is the function of the stomach body

A

Storage
Mucus
HCl
Pepsinogen
Intrinsic factor

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49
Q

What is the function of the stomach antrum

A

Mixing/Grinding
Gastrin production from G cells

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50
Q

Which cells in the stomach produce mucus

A

Mucus neck cells

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51
Q

Which cells in the stomach produce pepsinogen

A

Chief cells

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52
Q

Which cells in the stomach produce HCl and intrinsic factors

A

Parietal cells

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53
Q

What is the name of the sphincter that controls food movement from the stomach to the duodenum

A

Pyloric sphincter

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54
Q

In HCl production CO2 is absorbed from the blood and mixes with H20 to produce which compound
What enzyme catalyses the reaction
What does it dissociate to produce

A

H2CO3
Carbonic anhydrase
H+HCO3

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55
Q

In HCl production as bicarbonate is pumped out of the cell what is being pumped in to the cell

A

Chlorine Cl

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56
Q

To pump H ions in to the stomach what is being pumped in to the cell

A

Potassium K

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57
Q

How does parietal cell production of HCl affect pH of blood

A

Increases pH of blood slightly
>7.4

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58
Q

Which medications can inhibit the H/K proton pump in parietal cells (and stopping HCl production)

A

PPIs
E.g Omeprazole, esomeprazole, lansoprazole
Antihistamines

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59
Q

What process activates the parietal cells H/K pump
What enzyme causes this reactions

A

Phosphorylation
Kinase

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60
Q

What four chemicals alter the amount of kinase in the cell

A

Gastrin
Histamines
Prostaglandins
Acetylcholine

61
Q

What receptor does gastrin bind to which alters the amount of kinase and how does the receptor work
How does it alter the amount of Kinase
Which type of kinase is produced

A

Cckb receptor - Increases Ca in the cell
Increases kinase
Protein kinase C

62
Q

What receptor do histamines bind to which alters the amount of kinase and how does the receptor work
How does it alter the amount of Kinase
Which type of kinase is produced

A

H2 receptor - activates GS receptor->activates adenyl cyclase-> increase ATP converted to cAMP-> cAMP activates Kinase
Increase kinase
Protein Kinase A

63
Q

What receptor do neurotransmitters (e.g. acetylcholine) bind to which alters the amount of kinase and how does the receptor work
How does it alter the amount of Kinase
Which type of kinase is produced

A

M3 muscarinic receptors (parasympathetic) - increases Ca in the cell
Increases kinase
Protein kinase C

64
Q

What receptor do prostaglandins bind to which alters the amount of kinase and how does the receptor work
How does it alter the amount of Kinase
Which type of kinase is altered

A

EP3 receptors - activates G protein (GI)-> inhibits conversion of ATP to cAMP
Decreases kinase
Protein kinase A

65
Q

Which three mechanisms control gastric acid secretion

A

Neurocrine - vagal/local reflex
Endocrine - gastrin
Paracrine - histamine

66
Q

How many phases for gastric acid secretion stimulation are there
What are they

A

Two
Cephalic and gastric

67
Q

Explain the cephalic phase for gastric acid secretion stimulation

A

Increased vagus nerve stimulation will produce acetylcholine and stimulate G cells to produce gastrin
Also ECL cells produce histamines

68
Q

Explain the gastric phase for gastric acid secretion stimulation

A

Distension-> vagal/enteric reflex-> produces ACh
Peptides in lumen->G cells-> gastrin
Gastrin/ACh-> ECL cells-> histamines

69
Q

Why does acid secretion have to start before we begin eating

A

To sterilise food as soon as it is in our stomach

70
Q

How many phases for gastric acid secretion inhibition are there
What are they

A

Three
Cephalic, Gastric, Intestinal

71
Q

Explain the cephalic phase for gastric acid secretion inhibition

A

Stop eating-> decreased vagal activity

72
Q

Explain the gastric phase for gastric acid secretion inhibition

A

Decreased pH (increased HCl concentration) -> decreased gastrin production

73
Q

Explain the intestinal phase for gastric acid secretion inhibition

A

Acid in duodenum-> ENS reflex and secretin release-> decreased secretion and stimulation of parietal cells

Fat/CHO in duodenum -> GIP release-> decreased secretion and stimulation of parietal cells

74
Q

What are enterogastrones
Name the three enterogastrones

A

Hormones released from gland cells in duodenal mucosa, released in response to acid, hypertonic solutions, fatty acids and monoglycerides in duodenum
Seretin, chloecystokinin (CCK), gastric inhibitory peptide (GIP)

75
Q

How do enterogastrones prevent further acid build up

A

Inhibits gastric acid secretion
Reduce gastic emptying (inhibits motility)

76
Q

What is a zymogen
Give an example

A

Inactive form of an enzyme
Pepsinogen, trypsinogen

77
Q

What is the zymogen pepsinogen converted into
What is the function of the enzyme

A

Pepsin
Digests proteins in ingested food

78
Q

What conditions are required to convert pepsinogen to pepsin
Is the process reversible
Why

A

pH <3 (acidic)
Yes (at neutral pH)
To protect the duodenum from damage

79
Q

What is the role of gastric mucus

A

Cytoprotective role
Protects mucosal surface from mechanical injury
Neutral pH protects against gastric acid corrosion and pepsin digestion

80
Q

What is produced by parietal cells and is essential for vitamin B12 absorption

A

Intrinsic factor

81
Q

Where in the stomach do peristaltic waves take place

A

Weak in body
Strong in the antrum

82
Q

How many peristaltic waves are there a minute

A

Approx. 3/minute

83
Q

What is the slow peristaltic wave rhythm called

A

Basic electrical rhythm (BER)

84
Q

What generates the peristaltic rhythm
Where are they found

A

Pacemaker cells in the longitudinal muscle

85
Q

What determines contraction strength of peristaltic waves

A

The number of action potentials/wave

86
Q

What types of control are there for peristaltic waves of the GIT

A

Neural - wall distention-> long/short reflexes-> increases contraction force
Hormonal - gastrin
Fat/amino acids/acids/hypertonicity in duodenum - motility inhibited

87
Q

Why must acid be neutralised in the duodenum

A

Acid can damage duodenal walls and pancreatic enzymes

88
Q

Where is bicarbonate (HCO3) produced

A

Duodenum - Brunner’s glands

89
Q

What causes HCO3 secretion
what happens once acid is neutralised

A

Long (vagal) and short (ENS) reflexes
Release of secretin from S cells (HCO3 secretion from liver and pancreas)

Secretin inhibition (negative feedback)

90
Q

What two types of hormones are produced by the pancreas

A

Exocrine and endocrine

91
Q

Name the endocrine hormones and function of the pancreas
Where in the pancreas are they produced

A

Insulin - decrease blood glucose
Glucagon - increase blood glucose
Somatostatin - controls insulin and glucagon secretion
Pancreatic islets

92
Q

Where do endocrine hormones from the pancreas go to
How do they move there

A

Bloodstream
Vein

93
Q

What are endocrine hormones
What are exocrine hormones

A

Endocrine - hormones go to bloodstream
Exocrine - go to an epithelial surface

94
Q

Name exocrine proteins of the pancreas and its function

A

Pancreatic amylase - breakdown of starch into maltose
Digestive enzymes

95
Q

Where are exocrine products of the pancreas produced

A

Acinar cells in lobules

96
Q

Where do pancreatic exocrine products go
How do they move there

A

Duodenum
Via pancreatic duct
(accessory duct in case of problems)

97
Q

What is trypsinogen converted into
What enzyme aids this process

A

Trypsin
Enterokinase

98
Q

What is the function of trypsin

A

Converts zymogens to enzymes

99
Q

What are the categories of pancreatic enzymes

A

Protease
Nuclease
Elastase
Phospholipase
Lipase
Alpha amylase

100
Q

What does CKK control
How does it achieve this

A

Digestion of fats and proteins
Increases enzyme secretion

101
Q

What does Secretin control
How does it achieve this

A

Acid neutralisation
Increases bicarbonate secretion

102
Q

What is the largest internal organ

A

Liver

103
Q

What are the four lobes of the liver

A

Left
Right
Caudate
Quadrate

104
Q

Portal hepatic vein-> ? -> IVC

A

Hepatic veins

105
Q

What is the function of the liver

A

Production and secretion of bile

106
Q

What are the 6 components of bile
Where are they synthesised

A

Bile acids
Lecithin
Cholesterol
Bile pigments
Toxic metals
Bicarbonate HCO3
Synthesised by hepatocytes except HCO3 (duct cells)

107
Q

What are bile pigments produced from

A

Haemoglobin (damaged erythrocytes)

108
Q

What is the most common bile pigment
What colour does it make bile
what extracts it

A

Bilirubin
Yellow
Hepatocytes

109
Q

What causes the yellow colour of urine

A

Reabsorbed bilirubin that is excreted in the urine

110
Q

What are bile acids synthesised from

A

Cholesterol

111
Q

Bile acids conjugate with glycine or taurine
What is the product
Why do they conjugate

A

Bile salts
Increase solubility

112
Q

How are secreted bile salts recycled

A

Enterohepatic circulation

113
Q

Where is bile stored and concentrated
How is it concentrated
How many times concentrated is it

A

Gallbladder
Na and H20 are absorbed into the gallbladder
5-20x concentrated

114
Q

Fat in the duodenum leads to the release of CCK
How does CCK work

A

Relaxes sphincter of Oddi
Contracts the gallbladder
Bile is discharged into the duodenum
Solubilises fat

115
Q

How long is each section of the small intestines

A

Duodenum - 25cm
Jejunum - 2.5m
Ileum - 3.5m

116
Q

Name functions of each part of the small intestines

A

Duodenum - Gastric acid neutralisation, digestion, iron absorption
Jejunum - Nutrient absorption (95%)
Ileum - NaCl/H20 absorption -> chyme dehydration, Vit B12 absorption

117
Q

What increases surface area of the small intestines
Why is this important

A

Fold, villi, microvilli
Increases absorption

118
Q

What is absorbed in the small intestines

A

NaCl, peptides, mineral, vitamins, fats, monosaccharides, amino acids, water,

119
Q

Where does secretion take place in the small intestines

A

Crypts

120
Q

What is secreted by crypts of the intestines

A

Chorine
Water (1500ml/day) - reabsorbed by villi

121
Q

What is the purpose of water secretion in the intestines

A

Maintains liquid state of luminal contents
Promotes mixing of enzymes with digestive contents
Aids nutrient presentation to absorbing surface
Dilutes + washes away potential injurious substances

122
Q

What are the two types of intestinal motility and there functions

A

Segmentation
- provide mixing of contents and enzymes
- brings chyme into contact with surfaces
Peristalsis
- Migrating motility complex (MMC)
- gastric antrum -> terminal ileum (1 wave at a time)
- moves undigested material
- limits bacterial colonisation

123
Q

Does segmentation get stronger or weaker as it travels towards the rectum

A

Weaker

124
Q

What hormone causes peristalsis

A

MMC hormone - motilin

125
Q

Do peristalsis and segmentation take place at the same time
When do they start

A

No
Segmentation starts once food reaches the stomach
Peristalsis begins once segmentation ends

126
Q

What plexus mediates the intestinal motility

A

Myenteric plexus (between circular and longitudal muscle layers of muscularis externa

127
Q

What leads to increased segmentation activity in the ileum

A

Gastric emptying

128
Q

Explain the gastroileal reflex

A

Ileolcecal valve opens
Chyme enters the large intestines
Colon distends
Reflex contraction of ileocecal sphincter (prevents back flow)

129
Q

How long is the colon

A

1.5-1.8m

130
Q

Which muscle layer of the colon is complete and which is incomplete

A

Complete - circular
Incomplete - longitudinal

131
Q

What are the three bands of muscle the run the full colon called

A

Tenaie coli

132
Q

What are the pouches in the colon called

A

Haustra

133
Q

What type of epithelium is found in the colon mucosa

A

Simple columnar epithelium

134
Q

What are the sections of the colon called

A

Cecum
Ascending
Transverse
Descending
Sigmoid

135
Q

What is the rectum

A

Straight muscular tube

136
Q

Is the muscularis externa of the rectum thicker or thiner compared to the rest of the GIT

A

Thicker

137
Q

What type of epithelium is found in the rectum mucosa

A

Simple columnar epithelium

138
Q

What type of epithelium is found in the anal canal mucosa

A

Simple columnar->stratified squamous

139
Q

How long is the anal canal

A

2-3cm

140
Q

Is the external anal sphincter smooth or skeletal muscle
Is the sphincter under voluntary or involuntary control

A

Skeletal muscle
Voluntary control

141
Q

Does the colon have a role in nutrient absorption

A

No

142
Q

What are the functions/characteristics of the colon

A

Transports Na from the lumen to the blood->osmotic absorption of water->chyme dehydration->solid faecal pellets
Long residence time in the colon - bacterial colonisation

143
Q

How many bacteria are found in the colon

A

1000000000000000 (10 to the power of 14)
(approx. 1kg)

144
Q

What is the function of the bacteria in the colon

A

Fermentation of undigested carbohydrates
- short chain fatty acids
- vitamin K
- gas flatus

145
Q

What gases are produced by the bacteria of the colon

A

Nitrogen, CO2, hydrogen, methane, hydrogen sulphide

146
Q

What is the function of vitamin K

A

Blood clotting

147
Q

Is the internal anal sphincter smooth or skeletal muscle
Is the sphincter under voluntary or involuntary control

A

Smooth
Automatic/involuntary

148
Q

What cause the defection reflex

A

Rectal wall distention->mechanoreceptors->reflex-> defecation urge

149
Q

Which parasympathetic nerves control the defecation reflex

A

Pelvic splanchnic nerves

Gastrointestinal (4 decks)

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