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Physiology > Gastrointestinal physiology > Flashcards

Gastrointestinal physiology Flashcards

1
Q

what are the 4 major activities of the Gastrointestinal (GI) tract?

A
  1. ingestion
  2. digestion
  3. absorption
  4. excretion
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2
Q

what is the transit time in context of the GI tract?

A

refers to the duration it takes for ingested material to travel through specific portions of the digestive system

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3
Q

transit times of the mouth, oesophagus, stomach, SI and LI

A

mouth = 5 sec - 2 mins
oesophagus = 8 - 10 seconds
stomach = 15 mins - 4 hours
SI = 1-5 hours
LI = 12-24 hours

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4
Q

what does transit time determine?

A

the health of the GI tract

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5
Q

what are the main functions of the stomach: (6)

A
  • storage of ingested food
  • mechanical digestion
  • chemical digestion
  • initiation of protein digestion
  • killing of microorganisms
  • controlled emptying into the SI
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6
Q

what is ‘intrinsic factor’, and why is it essential? (3)

A
  • it is a glycoprotein
  • produced by parietal cells in stomach lining
  • essential for absorption of vitamin B12 into SI
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7
Q

why is the absorption of vitamin B12 needed?

A
  • crucial for RBC production and neurological function
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8
Q

the 3 topographic areas of the stomach

A
  1. fundus
  2. corpus
  3. antrum
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9
Q

what do chief and parietal cells do?

A

chief cells - pepsinogen secretion
parietal cells - secrete HCL

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10
Q

what are gastric pits? (2)

A
  • small invaginations in the lining of the stomach
  • lead to gastric glands
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11
Q

where are gastric pits located in the stomach (2)

A
  • lining of the stomach
  • primarily upper portion
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12
Q

where are the oxyntic glands primarily found?

A

upper portion of the stomach

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13
Q

where are the pyloric glands primarily fond?

A

antrum (lower portion)

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14
Q

how does the proton pump effects hydrogen secretion? (2)

A
  • exchange K+ ions for H+ ions across apical membrane of parietal cells
  • H+ ions are secreted into stomach lumen
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15
Q

what is the canaliculus? (2)

A
  • a small canal structure in parietal cells
  • where the process of acid secretion takes palce
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16
Q

what is the enterogastric reflex? (2)

A
  • where vagal stimulation of the stomach is inhibited
  • inhibits stomach
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17
Q

what are the 3 main functions of the SI?

A
  • secretion
  • digestion
  • absorption
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18
Q

what are the main functions of the large intestine (4)

A
  • sstore faecal material and regulate its release
  • secretion
  • absorption
  • provide environment for bacteria
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19
Q

what does the secretion function of the LI involve?

A
  • secretion of high concentrations of K+ and HCO3-
  • secretion of a thick mucinous substance to lubricate passage of faeces
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20
Q

why is it important that the LI provides an environment for bacteria?

A
  • some of them produce vitamins of B complex and vitamin K
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21
Q

what pattern recognition receptors does the gut epithelium express?

A
  • Toll- like receptors (TLRs)
  • Nucleotide binding oligomerization domain 2 (NOD2)
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22
Q

what transcription factor controls epithelial integrity and the interaction between mucosal immune system and gut microflora?

A

NF-kB

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23
Q

what do M cells do in the epithelium? (3)

A

antigen sampling:
* they facilitate the uptake and transportation of antigens
* including pathogens
* takes from inestinal lumen to underlying lymphoid tissue

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24
Q
A
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24
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25
Q
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26
Q

fundamental cell biological pathways in the regulation of GI function: (3)

A
  1. autophagy
  2. intracellular bacterial sensing
  3. unfolded protein response
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27
Q

what essentially is autophagy?

A

a cellular process involving the degradation and recycling of cellular components

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28
Q

the physiological responses of autophagy (2)

A
  • to remove damaged organelles and microorganisms (selective)
  • cellular starvation (non-selective)
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29
Q

what is the main molecule involved in the autophagy induction?

A
  • ATP proteins
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30
Q

what is the generating step in the autophagy pathway? (3)

A
  • the recruitment of ATG8 (LC3-1)
  • to the autophagosomal membrane
  • via membrane anchoring
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31
Q

what blocks and initiates the autophagy pathway?

A
  • the mTOR complex
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32
Q

what is the main abcterial intracellular sensory?

A
  • NOD2
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33
Q

where is NOD2 located?

A

cytosol

34
Q

how NOD2 is activated?

A

binding to muramyl dipeptide (MDP)

35
Q

other bacterial sensors aside from NOD2 within the cell, and the main difference

A

Toll-like receptor
* membrane bound bacterial sensor

36
Q

what essentially is unfolded protein response? (3)

A
  • a cellular stress response mechanism
  • activated when there is an accumulation of unfolded or misfolded proteins
  • in the ER of the cell
37
Q

what sense the cumulated unfolded/misfolded proteins in the ER?

A

Grp78 protein

38
Q

what is inflammatory Bowel disease?

A

a term used to describe a group of chronic inflammatory conditions that affect the GI tract

39
Q
A
39
Q

what is inflammatory Bowel disease characterised by? (3)

A
  • rectal bleeding
  • severe diarrhoea
  • weight loss
40
Q

what is coeliac disease? (3)

A
  • an immune-mediated inflammatory disease
  • of the small intestine
  • caused by sensitivity to dietary gluten and related proteins in genetically predisposed individuals
41
Q

symptoms of coeliac disease: (3)

A
  • chronic diarrhoea
  • weight loss
  • anameia
42
Q

what is the prevalence of coeliac disease?

A
  • 1-2%
  • raising over the current decades and we do not know why
43
Q

the 4 lobes of the liver

A

right lobe (largest)
left lobe
quadrate lobe - undersurface of liver
caudate lobe- posterosuperior surface

44
Q

what is the liver supplied by?

A
  • portal vein
  • hepatic artery
45
Q

what are sinusoids? (3)

A
  • specialised blood vessels
  • that recieve blood both from hepatic artery and portal vein
  • to supply hepatocytes
46
Q

what are the metabolising functions of the liver? (8)

A
  • energy metabolism
  • carbohydrate metabolism
  • fat metabolism
  • protein metabolism
  • hormone metabolism
  • bilirubin metabolism
  • metabolism of vitamins, minerals drugs
  • toxin metabolism
47
Q

what are the other functions of the liver aside from metabolism: (5)

A
  1. detoxification
  2. bile production
  3. filtration of pathogens
  4. storage of nutrients
  5. self-regeneration
48
Q

what is cholesterol required for? (5)

A
  • synthesis of cell membranes
  • repair of cell membranes
  • hormone synthesis
  • bile salt production
  • myelin sheath formation
49
Q

what do VLDL’s do (very low-density lipoproteins)?

A
  • transport cholesterol to various tissues thoughout the body
50
Q

what does the ouput pathway of ‘bile acid synthesis’ insinuate?

A

cholesterol can be converted into bile acids

51
Q

what is the reticuloendothelial system? (3)

A
  • a network of cells and tissues found throughout the body
  • play a crucial role in the immune system, and clearance of particles in the blood stream
  • consist mainly of phagocytic cells
52
Q

how does erythrocyte breakdown have anything to do with the liver?

A
  • kupffer cells engulf the erythrocytes and they undergo haemolysis
53
Q

what happens to the globin (1) and iron (2) in the breakdown of the erythrocyte? (2)

A

globin
* hydrolysed to amino acids and returned to blood

iron:
* carried to bone marrow
* used to make a new haemoglobin for RBC’s

54
Q

what does conjugation and un-conjugation mean?

A
  • refers to the chemical modifications involving the attachment or removal of certain molecules to form a compound
55
Q

where is bile stored

A

gall bladder

56
Q

what is bilirubin? (4)

A
  • a natural by-product of RBC breakdown
  • yellow/brown pigment
  • principle constituent in bile
  • insolube
57
Q

how is bilirubin transported in the blood?

A
  • binding to a protein called albumin
58
Q

what is conjguated bilirubin also known as?

A

direct bilirubin

59
Q

the main roles of bilirubin in bile: (2)

A

digestion and absorption of fats in SI

60
Q

what is jaundice? (2)

A
  • a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae, and other mucous membranes
  • caused by high blood bilirubin levels (hyperbilirubinemia)
61
Q

which form of bilirubin is undetectable in urine and why?

A
  • unconjugated bilirubin
  • it isnt water soluble due to binding to albumin
62
Q

what is a similar symptomatic disease that is harmless that may be mistaken for jaundice?

A
  • carotenemia
63
Q

typical disease that you see elevated bilirubin levels in: (2)

A

liver diseases:
* hepatitis
* liver cancer

64
Q

what causes hepatic hyperbilirubinemia?

A

defects in conjugation of bilirubin within the liver (UDP-glucuronyl transferase)

65
Q

what is more dangerous, conjugated or unconjugated hepatic hyperbilirubenmia?

A

conjugated

66
Q

the main causes of jaundice: (3)

A
  • haemolysis
  • hepatocellular
  • cholestasis
67
Q

what is portal hypertension? (2)

A
  • the development of collateral vessels that bypass the liver and connect portal and systemic venous system
  • can be caused by liver cirrhosis that causes obstruction
68
Q

what is a hepatotoxic disorder?

A
  • a condition or substance that has the potential to cause damage to the liver
69
Q

what is hepatotoxicity?

A
  • a term used to describe the adverse effects of certain drugs, chemicals, infections, or diseases on the liver
70
Q
A
71
Q

what are some therapeutic drugs that have been withdrawn from the market primarily because of their hepatotoxicity? (2)

A
  • troglitazone
  • bromfenac
72
Q

the 2 phases of drug metabolism in the liver:

A
  1. chemical modifications or inactivation by cytochrome P450
  2. conversion of lipid-soluble substances to water soluble derivatives
73
Q

what is the most common cause of acute liver failure?

A
  • paracetamol - 40 % of cases
74
Q

what makes paracetamol overdose more likely?

A
  • other substances such as alcohol that reduce GSH levels
75
Q

what cell of the stomach secretes acidic solution?

A
  • parietal cell
76
Q

what are the stimulants of acid secretion (3)

A
  • acetylcholine
  • Gastrin
  • Histamine
77
Q

what is the main digestive gland in the GI tract, and why

A

pancreas
* exocrine pancreas provides all the enzymes needed to digest food

78
Q

what is one of the main disorders of the pancreas?

A
  • acute pancreatitis - the pancreas digests itself and its surroundings
79
Q

what is the cell of the pancreas that produces the digestive enzymes?

A

the acinar cell

80
Q

what are the cell types that play an important role in the development of acute pancreatitis (3)?

A
  • the acinar cell
  • stellar cells
  • immune cells (macrophages)
81
Q
A

Physiology (10 decks)

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