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Clin Sci IMS, Respiratory, Renal, Cardiovascular, Nutrition & Energy > GI > Flashcards

GI Flashcards

1
Q

What are the three branches of GI Blood supply?

A
  • Coeliac trunk
  • Superior mesenteric
  • Inferior mesenteric
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2
Q

What are the branches of the coeliac trunk?

A
  • Hepatic artery
  • Splenic artery
  • Epigastric artery
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3
Q

What are the branches of the superior mesenteric artery?

A
  • Inferior pancreaticoduodenal artery
  • Jejunal and ileal arteries
  • Middle and right colic arteries
  • Ileocolic artery
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4
Q

What are the branches of the inferior mesenteric artery?

A
  • Left colic artery
  • Sigmoid branches
  • Superior rectal artery
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5
Q

Describe splanchnic circulation

A
  • Largest regional circulation from aorta
  • Storage site for blood
  • Blood diverted from splanchnic circulation to skeletal muscle beds - sympathetic activity
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6
Q

Describe blood flow control

A
  • Haemodynamic factors
  • Sympathetic nerve activity
  • parasympathetic nerve - vasodilator via indirect mechanisms
  • Activity of gut hormones - gastrin dilates
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7
Q

Describe gastric mucosal blood flow

A
  • Support secretion of gastric mucosal cells
  • Parasympathetic nervous system is main motor division for gut function - controlled by indirect mechanisms due to increase in metabolic activity of secretory cells
  • gastrin increases mucosal blood flow
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8
Q

Why are suppositorys used and why are they effective?

A

The superior rectal artery doesn’t drain into the hepatic vein therefore isn’t processed by the liver.
- Rectal artery drains into external iliac vein and then to the vena cava

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9
Q

Describe the blood supply to the different areas of the colon

A

Ascending and transverse = superior mesenteric

Transverse and descending = Inferior mesenteric

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10
Q

What gives rise to non-occlusive ischaemia of the gut?

A
  • Low blood pressure and cardiac output
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11
Q

Describe Non-occlusive ischaemia

A
  • Low CO gives rise to low perfusion of gut
  • Increase in viscosity / micro thrombi
  • Ischaemia - necrosis of mucosa and function disrupted as digestive enzymes due to lack of mucus to protect the gut
  • Intestinal permeability increases toxic substances gain access to body - toxaemia and septicaemia
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12
Q

Describe acute ischaemia

A
  • Rare because of collaterals
  • Results from venous occlusion - twisted or trapped intestine / hernia
  • Secondary obstruction arterial blood flow
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13
Q

What are the main purposes food provides energy for?

A
  1. Basal activities
  2. Cover expenditure of energy in simple activity
  3. For work activities
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14
Q

What is linoleic acid essential for?

A

Prostaglandin formation

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15
Q

Describe the importance of fibre

A
  • Maintains health of digestive tract
  • Bulks intestinal material, further stimulating peristalsis
  • Soluble and insoluble fibre
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16
Q

When is starvation declared?

A

When 25% body weight lost without permanent damage

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17
Q

When is a person declared obese?

A 
Female = above 30% body fat 
Male = above 20% body fat
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18
Q

Describe the liver

A
  • Largest visceral organ
  • Bile production
  • Blood sugar control
  • Protein synthesis and secretion
  • Lipid metabolism
  • Detoxification
  • Removal of bilirubin from damaged RBC- Kupfercells
  • Filtration
  • Vitamin A storage
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19
Q

Describe the anatomical position of the liver

A

Deep to ribs 7-11 right and midline, occupies most of right hypochondriac and upper epigastric, extending into left hypochondriac

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20
Q

What are the surfaces of the liver?

A

Right, left, caudete and quadrate

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21
Q

Describe the hepatic pedicle

A

Portal vein, hepatic artery, and bile duct

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22
Q

Describe a liver lobule

A

Central vein, sinusoids, hepatic artery, hepatic vein and portal triad

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23
Q

Describe the sinusoids of the liver

A
  • Blood channels between liver cells
  • Carry blood from triads to periphery of structural hepatic lobule to central vein
  • Lined by discontinuous and menstruated endothelial cells and kupffer cells
  • Perisinusoidal space - space of disse to facilitate exchange of material between blood plasma and hepatocytes
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24
Q

Describe liver metabolism - Mitochondria, RER, SER, Golgi and lysosomes

A

Mitochondria - Takes up 18% cell volume - enzymes for citric acid cycle, beta oxidation of fatty acids and first stage of urea cycle
RER - Protein synthesis - albumin, coagulation factors, enzymes, triglycerides
SER - Microsomes involved in bilirubin conjugation, detoxification, steroid synthesis, cholesterol synthesis and bile/acid synthesis
Lysosomes - contain dense hydrolytic enzymes containing organelles that act as scavengers for iron decomposition
Golgi - lies proximal to canaliculi involved in secretions such as bile acids and albumin

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25
Q

Describe liver cirrhosis

A
  • Unable to convert liver ammonia to urea and blood levels of toxic ammonia rise
  • Ammonia can cause coma and death due to toxicity of nervous system
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26
Q

Describe the bile system

A
  1. Food in duodenum
  2. CCK Release
  3. Contraction of the gallbladder
  4. Bile enters duodenum
  5. Transport of bile acids to ileum
  6. Absorption into portal blood
  7. IncreaseBile acid concentration in portal blood
  8. Uptake and secretion
  9. Store in gallbladder
  10. Back to step 3
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27
Q

Describe gallstones

A
  • Cholelithiasis
  • Gallbladder stones and concentrated bile
  • Abnormal metabolism of bile results in gallstones
  • cholesterol and pigment stones
  • Inflammation of gallbladder
  • Infection of bile duct
  • Obstruction of common bile duct
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28
Q

Describe portal hypertension

A
  • Restricts blood flow through damaged liver, increases blood pressure in portal system
  • Creates back pressure and shunting which can result in damaged to blood vessels in intestine and oesophagus
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29
Q

What are direct indicators of hepatobillary disease?

A
  • Plasma albumin
  • Plasma prothrombin
  • Serum bilirubin
  • Urine bilirubin/ urobillogen
  • Plasma alpha fetoprotein - hepatic tumour marker
30
Q

Describe pancreatic secretion

A
  • 2 Litres a day - alkaline fluid - bicarbonate rich and enzymes responsible for intermediate digestion of nutrients
  • Hormonal control of secretion - secretion CCK - cholecystokinin and secretin
31
Q

Describe the control of pancreatic juice secretion

A
  • Control of fluid secretions
  • Strongly acidic material enters duodenum as stomach empties
  • Entry of acid causes release of secretion from duodenal mucosa into blood stream
  • Secretion causes pancreas to secrete alkaline fluid into duodenum
  • Acid neutralised by bicarbonate rich secretion
32
Q

Describe activation of proteolytic enzymes from pancreas

A
  • Activated in the small intestine

- Involves enzymes from mucosa enterokinase - intestinal brush border enzyme

33
Q

What are the 4 pancreatic zymogens (proenzyme) and their activation process?

A

Trypsinogen activated by enteropeptidases in brush border to trypsin
- Chymotrypsin
- Carboxypeptidase
- Colipase
- Phosphodipase
These are the activated enzymes activated by trypsin

34
Q

Describe pancreatin - CREON

A
  • Orally administered pancreatic enzymes from porcine pancreas used to compensate for deficiency in pancreatic secretions
  • Used for cystic fibrosis causing chronic pancreatitis and pancreatectomy
35
Q

Describe ACARBOSE

A

Glucobas inhibitor

- Alpha glucosidases which delay digestion and absorption of starches and sucrose used in diabetic patients

36
Q

Describe ORLISTAT

A
  • Inhibitor of pancreatic lipase which reduces digestion and absorption of fats used in obesity treatment - unpleasant side effects
37
Q

Describe bile functions and the role of emulsification

A

Excretory route for non water-soluble substances especially pigments from haemoglobin break down - bilirubin

  • Role of emulsification of fats prior to digestion, bile salts lower surface tension of fat droplets and iAd on formation of mixed muscles
  • Absence of bile salts reduce fat/digestion and absorption - derivatives of cholesterol
38
Q

Describe the intestinal mucosal cells (6)

A 
Intestinal stem cells 
Paneth cells 
Transit amplifying cells 
Goblet cells 
Enteroendocrine cells 
Enterocytes
39
Q

What are the 5 enteroendocrine cells and what do they secrete?

A 
G Cells - gastrin secretion 
I cells - Cholecystokinin 
K cells - Glucose dependent insulinotropic peptide 
M cells - motilin 
S cells - secretin
40
Q

What are paneth cells and their function?

A

Control of gut flora

- bacterial enzyme lysozyme

41
Q

What is the function of motilin?

A

Accelerates gastric emptying and intestinal peristalsis

42
Q

What are causes of malabsorption ?

A
  • Bile salt deficiency
  • Pancreatic enzyme deficiency
  • Infections
  • Deficiency of brush border enzyme/ carrier
  • Coeliac disease
  • rapid transit
43
Q

What are symptoms of malabsorption?

A
  • Diarrhoea
  • Steatorrhoea - fat in faeces
  • Abdominal pain
  • Vomiting
  • Loss of appetite
  • Weight loss
  • Dehydration
  • Oedema
  • Anaemia
44
Q

Describe the salivary glands

A

Paotid - serous
Sublingual - predominantly mucous
Submandibular - mucous and serous

45
Q

Describe the minor salivary glands

A

Mucosa of buccal cavity, tongue and epiglottis

46
Q

Describe salivary secretion

A

Dependent on nervous system

  • Tastebud and mechanoreceptors activated by food
  • Sensory information sent to salivary nuclei in medulla of brain
47
Q

What are the 6 main gastric secretions?

A
  • HCL
  • Pepsinogen
  • Gastrin
  • Intrinsic Factor
  • Mucous and bicarbonate
  • Histamine
48
Q

Describe the secretions of the Proximal 80% of the stomach

A

Parietal and chief cells

- HCL, intrinsic factor, pepsinogen and mucous

49
Q

Describe the distal 20% secretions of the stomach

A

Gastrin and mucous cells - some chief cells

- Gastrin, pepsinogen and mucous

50
Q

What are the functions of gastric acid?

A
  • Activates pepsinogens
  • Mountains of pepsin activity
  • Bactericidal
  • Disrupts connective tissue proteins
  • Dissolves particulate matter in food
51
Q

Describe gastrin

A

Hormone released from G cells of gastral mucosa by acetylcholine stretch and dietary proteins
- Circulates in blood stream to parietal and other secretory cells

52
Q

Describe histamine

A

Local hormone released from cells close to parietal cells by gastrin and acetylcholine
- Acts with them to give strong secretory response

53
Q

What are the three control phases of digestion?

A

Cephalic - 20%
Gastric - 70%
Intestinal - 10%

54
Q

Describe the cephalic phase

A

Triggered by thought, smell and taste of food

  • Nervous mechanisms, impulses from CNS via vagus nerve
  • Release acid + pepsin
  • Small release of gastrin from gastral g cells
55
Q

Describe the gastric phase

A

Triggered by distention of the stomach by food

  • Action of food components
  • Hormonal mechanisms - release gastrin from G cells of antrum which circulates to glands in the fondus and increases acid and pepsin secretion
56
Q

Describe the intestinal phase

A

Triggered by emptying of stomach contents into duodenum and low PH in gastric antrum

  • Release of hormones from duodenal mucosa which inhibit gastric secretion
  • Short and long CNS nervous reflexes which inhibit gastric secretion/ release
57
Q

What are secretions of small intestine? (12)

A
  • Enteropeptidases
  • Aminopeptidases
  • Carboxypeptidases
  • Endopeptidases
  • Dipeptidases
  • Maltase
  • Lactase
  • Sucrase
  • Alpha lextrinase
  • Tehlase
  • Nuclease
  • Related enzymes
58
Q

Describe the foregut

A

Pharynx, oesophagus, stomach, superior duodenum

59
Q

Describe the midgut

A

Inferior duodenum, jejunum, ileum caecum, ascending and transverse colon

60
Q

Describe the hindgut

A

Transverse and descending colon, sigmoid colon, rectum

61
Q

Describe peristalsis and segmentation

A 
Peristalsis = forward movement 
Segmentation = mixing
62
Q

Describe modulation of GI muscles

A

Parasympathetic - increase gut muscle activity releases sphincters
Sympathetic - Inhibit gut movements and constricts sphincters
Hormones - Increase or decreases activity of CCK and secretin

63
Q

Describe stimulation of gastric phase

A
  • Stretch of wall and presence of specific food components results in the release of gastrin and activation of CNS and local reflexes
  • Increase motility and emptying of stomach
64
Q

Describe inhibition during the intestinal phase

A

Emptying of stomach into duodenum results in release of hormones which inhibit gastric motility and activation of nerve reflexes

65
Q

Describe bulk laxatives

A

Increase faecal mass and peristalsis

66
Q

Describe osmotic laxatives

A

Increase water in large bowel

67
Q

Describe Faecal softeners

A

Act as detergent permitting water and lipids to penetrate

68
Q

Describe stimulative laxatives

A

Stimulate sensory nerve endings

69
Q

Describe oral rehydration

A

Amount depends on size of individual

70
Q

What is a homemade oral dehydrator recipe?

A

1 tsp salt, 8 tsp sugar, 1 litre water

Clin Sci IMS, Respiratory, Renal, Cardiovascular, Nutrition & Energy (17 decks)

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