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GI Anatomy > Physiology - upper GI + liver + gallbladder > Flashcards

Physiology - upper GI + liver + gallbladder Flashcards

1
Q

What is the chewing reflex

A

As jaw contracts, pressure created from food moving against gums and tongue –> pressure sensed by mechanoreceptors which then initiate a reflex which inhibits jaw muscles thus relaxing them –> and so on until food is chewed enough to swallow

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2
Q

Saliva is secreted by what 3 glands

A

Parotid
Submandibular
Sublingual

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3
Q

What kind of glands are exocrine glands + description

A

Exocrine - means they secrete into ducts to outside of body or on a surface

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4
Q

4 components of saliva

A

Water
Mucins
a-amylase
Lysozyme

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5
Q

Function of water as a component of saliva

A

Softens and dilutes particles thus reducing osmolarity

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6
Q

Function of mucins as a component of saliva

A

Combines with water to form mucus allows lubrication of food down the oesophagus

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7
Q

Function of a-amylase as a component of saliva

A

Is an enzyme that breaks down polysaccharides (starch, glycogen)

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8
Q

Function of lysozyme as a component of saliva

A

It kills bacteria in mouth by cleaving polysaccharide component of cell wall of bacteria

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9
Q

Salivary secretion is stimulated by what system

A

Autonomic - parasympathetic + sympathetic

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10
Q

What parasympathetic nerves control saliva secretion

A

Cranial nerves VII (facial nerve) + IX (glossopharyngeal nerve)

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11
Q

What type of salivary secretion is produced by parasympathetic system stimulation

  • volume
  • consistency
A

Lots of WATERY saliva

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12
Q

What type of salivary secretion is produced by sympathetic system stimulation

  • volume
  • consistency
  • mucus content
  • amylase content
A

Small volume, high protein THICK saliva
High mucus content (due to a1 adrenoceptors)
High amylase content (due to b2 adrenoceptors)

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13
Q

What is reflex control of salivary secretion

A

Food in mouth will be sensed my mechanoreceptors and cause salivary glands to become more active

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14
Q

Oesophagus vertebral level

A

C6 - T11/12

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15
Q

Types of muscle in oesophagus

A

Upper oesophagus is skeletal muscle

Remainder is smooth muscle

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16
Q

4 layers of oesophageal wall

A

Mucosa
Submucosa
Muscularis externa
Adventitia

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17
Q

Oesophageal mucosa is lined by what kind of epithelium

A

Stratified squamous non- keratinised

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18
Q

Where are submucosal glands (just means glands present in submucosa) found in the GI tract

A

Oesophagus and duodenum

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19
Q

What kind of glands are the submucosal glands in the oesophagus

A

Mucous secreting glands –> secrete into ducts –> lubricating oesophagus

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20
Q

Oesophagus function + peristalsis within oesophagus is produced by which layer of the muscularis externa

A

Transports food/liquid into stomach

Peristalsis produced by inner circular muscle of muscularis externa

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21
Q

What nerve innervating oesophagus controls contraction and relaxation of LOS

A

Vagus nerve

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22
Q

Stomach functions (5)

A

Temporary store of ingested food
Dissolves food particles
Controls delivery of food to small intestine
Sterilise ingested food (gastric acid kills micro-organisms)
Produce intrinsic factor

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23
Q

What function of the stomach is not compensatable by the body

A

Intrinsic factor production because it is essential for vitamin b12 absorption

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24
Q

What sphincter controls delivery of contents from stomach to SI

A

Pyloric

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25
Q

What is the opening of the top end of the stomach called (3 different names)

A

Cardiac/gastro-oesophageal opening

Lower oesophageal sphincter or cardiac sphincter

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26
Q

Stomach components from start to end

A 
Cardiac opening/sphincter
Cardiac region
Fundus
Body (greater/lesser curvature)
Antrum
Pyloric region
Pyloric opening/sphincter
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27
Q

How many layers in the muscularis externa of the stomach (different to oesophagus)

A

3

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28
Q

What are the 3 layers of the muscularis externae of the stomach

A

Outer - longitudinal muscle
Middle - circular muscle
Inner - oblique muscle, doesn’t appear until antrum area

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29
Q

The mucosa and submucosa of the stomach fold to give what

A

Rugae

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30
Q

What cells form the lumens surface of the stomach

A

Flat surface mucus cells

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31
Q

What are gastric pits

A

Invaginations in the lumens surface of the stomach that lead down to gastric glands

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32
Q

Gastric glands composed of what 3 cells

A

Mucus neck cells
Parietal cells
Chief cells

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33
Q

Function of mucus neck cells (component of gastric glands)

A

Secrete mucous to protect stomach from gastric acid

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34
Q

Function of parietal cells (component of gastric glands)

A

Secrete HCl and intrinsic factor

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35
Q

Function of chief cells (component of gastric glands)

A

Secrete pepsinogens

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36
Q

What happens in the bolus phase of swallowing

A

Bolus (food) pushed to back of mouth by tongue

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37
Q

What happens in pharyngeal phase of swallowing

A

Bolus triggers reflex contractions of pharyngeal muscles

Soft palate reflected backward and upward so closing off nasopharynx to prevent regurgitation through nose

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38
Q

What happens as bolus approaches oesophagus

A

UOS relaxes and opens

Epiglottis covers larynx to prevent food entering trachea

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39
Q

What happens once food has entered oesophagus

A

UOS contracts to prevent reflux

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40
Q

What happens in oesophageal phase of swallowing

A

Peristaltic wave (muscle behind bolus contracts and muscle ahead relaxes), propelling bolus down to stomach

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41
Q

How long does it take to propel bolus down oesophagus into stomach

A

10 secs

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42
Q

When is receptive relaxation of the stomach initiated

A

Following receptive relaxation of LOS and entry of bolus into stomach

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43
Q

What is receptive relaxation of the stomach + what nerve is it mediated by

A

Relaxation of the fundus and body following relaxation of LOS, increasing stomach volume from 50ml to 1500ml

CN X

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44
Q

Function of the fundus of stomach

A

Storage

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45
Q

Function of body of stomach (5)

-secretion of 4 things

A 
Storage
Mucus secretion
HCl secretion
Pepsinogen secretion
Intrinsic factor secretion
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46
Q

Function of pepsinogen (Secreted by chief cells)

A

Inactive precursor form of pepsin as pepsin would cause autodigestion of stomach
-pepsin breaks down proteins

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47
Q

Functions of antrum of stomach (2)

A

Mixing/grinding food (as contraction strongest here due to prominent inner oblique muscle)

Gastrin secretion by G cells

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48
Q

What is pepsin and how is it formed

A

Protein digestive enzyme

Pepsinogen gets cleaved chemically to form pepsin (Active form)

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49
Q

Describe gastric acid secretion process (7)

  • what compound diffuses into parietal cell from blood and combines with water
  • what does this then form and what enzyme is the reaction catalysed by
  • the substance formed is not stable so dissociates into what 2 ions
  • one of these ions gets pumped out apical membrane of parietal cell into the stomach lumen via a transporter
  • the other ion gets pumped out basolateral membrane into blood in exchange for a different ion
  • this exchanged ion then comes into parietal cell from the blood then what happens to it
  • gastric acid is then finally formed by combination of what 3 things
A
  1. CO2 from blood diffuses into parietal cells and combines with water present in the cytoplasm, catalysed by carbonic anhydrase expressed by the parietal cells to form CARBONIC ACID
  2. Carbonic acid not stable so dissociates into hydrogen and bicarbonate ions immediately
  3. The hydrogen ions then pumped out apical membrane via H/K ATPase into stomach lumen
  4. Bicarbonate ions pumped out across basolateral membrane into blood in exchange for Cl ions coming in via chloride/bicarbonate exchanger
  5. Cl ions that have come into cell subsequently leave cell across apical membrane via a chloride shunt
  6. Now have H+ and Cl- inside stomach lumen, creating an osmotic gradient which water will follow
  7. Water then combines with H+ and Cl- –> HCl
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50
Q

Name the 2 hormones that control gastric acid secretion and what produces them

A

Gastrin (hormone) is produced by G cells

Histamine produced by local gland and only acts in the vicinity of where it’s secreted (so not within circulation)

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51
Q

Describe hormonal control of gastric acid secretion (describe gastrin specifically - how it stimulates gastric acid secretion) (5)

A

Gastrin binds to its receptor in the parietal cell basolateral membrane

  • -> This increases Ca2+ conc. inside the cell
  • -> which activates protein kinases
  • -> which stimulates H/K ATPase
  • -> Increased activity of H/K ATPase pumps more H+ into stomach lumen
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52
Q

Describe hormonal control of gastric acid secretion (describe histamine specifically - how it stimulates gastric acid secretion) (5)

A

Histamine acts on its G-protein coupled receptor on the basolateral membrane of the parietal cell

  • ->which activates the AC protein the G protein is coupled to, stimulating it to convert ATP to cAMP
  • -> cAMP then stimulates protein kinases
  • -> which stimulate H/K ATPase
  • -> Increased activity of H/K ATPase pumps more H+ into stomach lumen for HCl production
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53
Q

When the AC protein is activated, it stimulates the conversion of ATP to what (relating to gastric acid secretion)

A

cAMP

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54
Q

Describe neural control of gastric acid secretion (5)

-think what neurotransmitter stimulates gastric acid secretion

A

ACh released by parasympathetic fibres of CN X innervating stomach binds to muscarinic/cholinergic receptor in basolateral membrane of parietal cells

  • -> causes rise in calcium inside cell
  • -> increased Ca2+ conc. activates protein kinases
  • -> which then stimulates H/K ATPase
  • -> Increased activity of H/K ATPase pumps more H+ into stomach lumen for HCl production
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55
Q

What does H/K ATPase do (Relating to gastric acid secretion)

A

Uses ATP to pump 1 H+ out of cell into stomach lumen in exchange for 1 K+

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56
Q

What hormone like substance inhibits HCl production

-unlike gastrin, histamine and ACh (which all stimulate HCl production)

A

Prostaglandin

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57
Q

How does prostaglandin inhibit HCl production (5)

A

It binds to inhibitory G protein coupled receptors on the basolateral membrane of the parietal cell

  • -> inhibiting the AC protein the G protein is coupled to
  • -> so inhibiting conversion of ATP to cAMP
  • -> thus inhibiting protein kinase stimulation
  • -> therefore inhibiting H/K ATPase activity
58
Q

The CEPHALIC PHASE of digestion (first phase of digestion followed by gastric then intestinal phase) is the gastric secretion that occurs even before food enters the mouth
-it results from the sight/smell/taste of the food so the brain induces an anticipatory response to prepare the GI tract for digestion

What nerve is the cephalic phase mediated by + what 2 mechanisms does this nerve stimulate HCl secretion

A
  1. Increased vagal activity –> increasing release of ACh –> stimulating parietal cells to produce HCl
  2. Increased vagal activity –> stimulates G cells to produce gastrin –> gastrin then stimulates parietal cells to produce HCl
59
Q

3 things happen in the GASTRIC PHASE* that stimulate gastric acid secretion

*period in which swallowed food and semi-digested proteins activate gastric activity; 2nd phase of digestion; preceded by cephalic phase, proceeded by intestinal phase

A
  1. Stomach wall distends –> mechanoreceptors sense distension and trigger vagal/enteric reflexes –> triggering increase in ACh release –> stimulating parietal cells to make HCl
  2. Peptides in stomach lumen –> trigger G cells to produce gastrin –> stimulating parietal cells
  3. Local gastrin/ACh stimulates ECL cells which triggers them to release histamine –> which then stimulates parietal cells
60
Q

In which 2 out of 3 phases of digestion can you stimulate gastric acid secretion

A

Cephalic and gastric

NOT INTESTINAL

61
Q

In which phases of digestion (there are 3 phases) can you inhibit gastric acid secretion

A

All of them - cephalic, gastric + intestinal

62
Q

What can you physically do in the cephalic phase of digestion (there are 3 phases of digestion) that can inhibit gastric acid secretion

A

Stop looking/thinking/smelling/eating –> decreased vagal activity –> decreased stimulation of parietal cells by ACh or gastrin

63
Q

What negative feedback mechanism in the gastric phase of digestion (there are 3 phases of digestion) can inhibit gastric acid secretion

A

By decreasing pH (by increasing HCl conc.) –> triggers decreased gastrin production (NEGATIVE FEEDBACK - enough HCl so don’t need to make more)

64
Q

What 2 things occur in the intestinal phase (there are 3 phases of digestion) that inhibits gastric acid secretion

A
  1. Acid in duodenum triggers enterogastric (splanchnic) reflex + release of secretin –> decrease gastrin secretion –> decreased parietal stimulation
  2. Fat in duodenum –> triggers GIP (gastroinhibitory polypeptide) release –> decreases gastrin secretion –> decreased parietal stimulation
65
Q

What are enterogastrones + 3 examples of enterogastrones

A

Hormones released from glands in duodenal mucosa

  • Secretin
  • Cholecystokinin (CCK)
  • Gastroinhinitory polypeptide (GIP)
66
Q

Function of enterogastrones

A

Prevent further acid build up in duodenum by either INHIBITING GASTRIC ACID SECRETION or REDUCING GASTRIC EMPTYING

67
Q

What is a zymogen + why are they produced

A

Inactive form of enzymes (inactive precursor) that undergoes acid hydrolysis to form the active form

Storing enzymes as zymogens prevents autodigestion

68
Q

2 cytoprotective roles of gastric mucus

A
  1. protects mucosal surface from mechanical injury

2. HCO3 in mucus neutralises acidic pH –> protecting against gastric acid corrosion and pepsin digestion

69
Q

Why is intrinsic factor important in vitamin B12 absorption

A

Intrinsic factor is needed to form a complex with vitamin B12 to allow it to be absorbed in the ileum

70
Q

What does intrinsic factor deficiency cause

A

Pernicious anaemia - failure of RBC maturation because vit. B12 needed for RBC maturation

71
Q

Stomach body v antrum motility

A

Body has thin muscle –> so weak contraction –> so no mixing

Antrum has thick muscle –> so powerful contraction –> allowing MIXING OF FOOD & CONTRACTION OF PYLORIC SPHINCTER

72
Q

How is the peristaltic rhythm generated

A

By pacemaker cells in the longitudinal muscle layer

73
Q

How many peristaltic waves are there per min

A

3

74
Q

Slow peristaltic waves are due to what + description about AP threshold

A

Spontaneous depolarisation/repolarisation (intrinsic rhythm)

Slow wave depolarisation is sub-threshold so requires further depolarisation to induce APs

75
Q

What determines the strength of contraction in peristalsis

A

Number of APs

76
Q

What 4 things inhibit motility of GI tract

A

Fat
acid
amino acids
hypertonicity

in the duodenum

77
Q

What neutralises gastric acid in the duodenum

A

Bicarbonate secretion from Brunner’s gland duct cells in the submucosa

78
Q

What are the submucosal glands called in the duodenum

A

Brunner’s glands

79
Q

When acid arrives in duodenum, it triggers what 2 things + what do these 2 things subsequently cause

A
  1. Long (vagal) and short (ENS) reflexes -
  2. Release of secretin from S cells

CAUSE HCO3 SECRETION

80
Q

What is the main trigger for Brunner’s glands to make bicarbonate

A

Secretin from s cells

81
Q

Secretin stimulates bicarbonate secretion from Brunner’s glands and what other 2 places

A

Pancreas (specifically the duct cells in the exocrine pancreas)
Liver

82
Q

Bicarbonate ions bind with hydrogen ions from gastric acid to form what

A

Carbonic acid

83
Q

Pancreas has 2 portions called what

A

Endocrine and exocrine

84
Q

Function of endocrine portion of pancreas (made of what cells + produces what 3 hormones)

A

Made of islet of langerhans cells

  • beta cells produce insulin
  • alpha cells produce glucagon
  • delta cells produce somastatin
85
Q

What is somatostatin

A

A hormone that controls secretion of insulin and glucagon, and other hormones in the body

86
Q

Function of exocrine pancreas + made of what 2 types of cells + what do these cells produce)

A

DIGESTIVE FUNCTION

Made of ACINAR cells which secrete pancreatic (digestive) enzymes
and DUCT cells which secrete bicarbonate

87
Q

Individual acinar cells of exocrine pancreas join together to form what structure

A

Lobules

88
Q

The point of joining of the main pancreatic duct with the common bile duct is called what

A

Hepatopancreatic ampulla (ampulla of vater)

89
Q

Relation of sphincter of oddi + ampulla of vater

A

Sphincter of oddi is the actual muscular valve that surrounds the ampulla of water and controls the flow of bile and pancreatic juices through the ampulla of vater into duodenum

90
Q

Where does bile and pancreatic juice enter duodenum

A

Major duodenal papilla in 2nd part of duodenum

91
Q

What cells in exocrine pancreas secrete bicarbonate and digestive enzymes

A

Duct cells - secrete bicarbonate

Acinar cells - secrete digestive enzymes

92
Q

Digestive enzymes secreted by acinar cells of pancreas are secreted in what form

A

Zymogens - inactive

93
Q

What 2 organs produce zymogens

A

Chief cells in stomach

Acinar cells in pancreas

94
Q

What zymogen produced by the pancreas is activated a different way from other digestive zymogens

A

Trypsinogen

95
Q

How is trypsinogen (produced by the pancreas) activated differently from other digestive enzymes

A

Enterkinase (a membrane bound enzyme of the duodenum) converts trypsinogen to trypsin when trypsinogen comes into contact with it

96
Q

Zymogen secretion in the pancreas is stimulated by what hormone/enterogastrone

A

Cholecystokinin

97
Q

What secretes CCK + what physiological stimuli causes CCK to be released

A

Secreted by gland cells in duodenal mucosa

Fatty acids + amino acids in duodenum triggers CCK release

98
Q

As well as fatty + amino acid trigger for CCK stimulation, what else controls CCK release

A

Neural control - vagus nerve

ENS - local reflexes

99
Q

List 6 pancreatic enzymes + their respective functions

A

Proteases - cleave peptide bond

Nucleases - hydrolyse dna/rna

Elastases - digest collagen

Phospholipases - breakdown phospholipids to fatty acids

Lipases - break down TAG to monoglyceride + 2 fatty acids

A-amylase - break down starch/glycogen

100
Q

Physiological stimuli for secretin release from S cells

A

Acid in duodenum

101
Q

Functions of secretin (5)

A

Stimulates duct cells in pancreas to secrete bicarbonate

Stimulates Brunner’s gland in duodenal mucosa to secrete bicarbonate

Stimulates bile duct to secrete bicarbonate

Decreases gastric acid secretion

Decreases gastric emptying

102
Q

Functions of CCK (4)

A

Stimulates pancreatic acinar cells to secrete zymogens (inactive digestive enzymes)

Relaxes sphincter of oddi - increasing pancreatic flow into duodenum

Contracts gallbladder to release more bile into duodenum

Increases tone of pylorus - decreasing gastric emptying

103
Q

4 lobes of liver (major + minor)

A

Major - right and left

Minor - caudate and quadrate

104
Q

What is the porta of the liver + where is it located

A

Where vessels enter and exit the liver

On the inferior surface of liver

105
Q

Name the 3 main vessels at the porta

+ other vessels

A

Hepatic artery
Hepatic portal vein (just means portal vein inside liver)
Hepatic duct

Lymphatic vessels, nerves

106
Q

How is common bile duct formed

A

Common hepatic duct joins with cystic duct (from GB)

107
Q

What ligament attaches liver to underside of diaphragm

A

Coronary ligament

108
Q

What area of the liver isn’t covered by connective tissue capsule and visceral peritoneum + where is it on the liver

A

Bare area

- Diaphragmatic surface on the right lobe

109
Q

What structures within the liver are the functional units

A

Hexagonal LOBULES

110
Q

What is the portal triad + where is it located

A

A branch of the portal vein, hepatic artery and hepatic duct

Located at each corner of a hexagonal lobule

111
Q

What does each component of the portal triad carry (specify the thing being carried) + differentiate if each component is carrying into or out of the liver

A

Hepatic portal vein - carries nutrient rich, deoxygenated blood from GI tract INTO LIVER

Hepatic artery - carries oxygenated,, nutrientless blood from left side of circulation INTO LIVER

Hepatic duct - carries bile OUT OF LIVER

112
Q

What vein exists at the centre of each hexagonal liver lobule and what is the subsequent pathway of venous blood through this vein

A

Central vein –> hepatic veins –> IVC

113
Q

Hepatocytes (functional liver cells in the lobule) form what things that radiate out from the central vein

A

Hepatic cords

114
Q

What are hepatic sinusoids + where are they in the liver + function

A

They are discontinuous, fenestrated open capillaries found between hepatic cords (line of hepatocytes)
Blood flowing through these sinusoids leaks into hepatocytes allowing them to process the blood so damaged/old RBCs can be removed from circulation

115
Q

Direction of flow of blood from hepatic artery at the corner of a lobule

A

Hepatic artery –> hepatic sinusoid –> central vein –> hepatic veins

116
Q

Direction of flow of blood from the hepatic portal vein at the corner of a lobule

A

Hepatic portal vein –> hepatic sinusoids –> central vein –> hepatic veins

117
Q

4 functions of hepatocytes

A

Produce bile

Store nutrients

Nutrient interconversion - when nutrient deprived, liver will convert other nutrients into what’s needed

Detoxification - takes out harmful substances and puts it into bile, converts ammonia to urea

118
Q

What nutrients does the liver store

A

Glycogen
Vit B12, A, D, E, K
Cu, Fe

119
Q

6 components of bile

A 
Bile acids
Lecithin
Cholesterol
Bile pigments
Toxic metals
Bicarbonate
120
Q

What 3 components of bile are made in liver and can solubilise fat

A

Bile acids
Lecithin
Cholesterol

121
Q

What are bile pigments

A

Breakdown products of haemoglobin from old/damaged erythrocytes

122
Q

What is the predominant bile pigment called

A

Bilirubin - breakdown product of haem

123
Q

How does yellow bile form

A

Bilirubin is extracted from blood by hepatocytes and secreted into bile, giving it a yellow colour (bilirubin gives yellow colour)

124
Q

How do faeces get its brown colour

A

Bilirubin is modified by bacterial enzymes in LI creating brown pigments

125
Q

How does urine get its yellow colour

A

Bilirubin that’s not secreted into bile gets reabsorbed and excreted in urine, giving it a yellow colour

126
Q

How are bile acids made

A

Made in liver from cholesterol

127
Q

Before bile acids are secreted into bile to go to duodenum, what happens to them

A

Bile acids are conjugated (chemically combined) with glycine/taurine to form BILE SALTS

128
Q

What are bile canaliculi + where are they found

A

Thin vessels that collect bile secreted by hepatocytes, lie between hepatocytes within a hepatic cord

129
Q

Bile that gets secreted into canaliculi flows into what

A

Hepatic duct

130
Q

How are bile salts recycled + where are they recycled

A

Recycled in ileum via a BILE SALT TRANSPORTER into the hepatic portal vein then back into the liver

131
Q

Path of bile acid/salts from liver (recycled so ends up in liver again)

A

Liver –> common bile duct –> duodenum –> ileum –> hepatic portal vein –> liver

132
Q

What surface of liver is the gallbladder on

A

Inferior

133
Q

3 layers of the wall of the gallbladder

A

Mucosa - folded into rugae
Muscularis - contractile
Serosa - connective tissue

134
Q

2 functions of gallbladder

A

Stores bile by active absorption of Na+

Concentrates bile 5-20 times by absorbing Na and H2O from it

135
Q

What does gallbladder do if you keep eating lots of fatty food

A

Releases more bile out of it so less time to concentrate it

136
Q

What is the trigger for gallbladder to release bile

A

Fat in duodenum

137
Q

The stimuli for hydrochloric acid secretion by the parietal cells in the cephalic phase include

A

tasting/smelling/chewing

138
Q

The major inhibitory mechanism for hydrochloric acid secretion by parietal cells is through what hormone

A

somatostatin (GHIH)

139
Q

Presence of fat in stomach increases or decreases gastric emptying time

A

increases

140
Q

3 phases of swallowing

A

Oral (voluntary)
Pharyngeal (involuntary)
Oesophageal (involuntary)

141
Q

In which phase of swallowing is the back of the tongue is elevated and the soft palate pulled anteriorly against it
-this keeps the food within the oral cavity and allows the airway to remain open

A

Oral (voluntary) phase

GI Anatomy (21 decks)

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