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MDENT210 > Gastrointestinal tract > Flashcards

Gastrointestinal tract Flashcards

1
Q

Describe the main components of the GI tract

A

mouth, oesophagus, stomach, (pancreas, liver, gallbladder), small and large intestine, anus

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2
Q

Discuss the control mechanisms of the GI tract

A
  1. autonomic nervous system
    - parasympathetic nerves stimulate digestion
    - sympathetic nerves inhibit digestion
  2. Enteric nervous system - 2 nerve plexus in the gut walls can sense the luminal contents and control muscles and glands (2nd brain)
    - myenteric plexus and submucosal plexus
    - has sensory, motor, interneurone, muscle and gland components
  3. Gut peptides - paracrine and hormonal

(neural, paracrine and hormonal)

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3
Q

Describe gastric functions (stomach)

A

Motility - gastric accommodation, trituration, gastric emptying
Digestion - digestive juice
Protection - acid/proteases, mucus
Absorption

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4
Q

Discuss the morphology of the gastric glands

A

Gastric pits - indentations in the stomach epithelial lining which are the entrances to 3-5 tubular shaped gastric glands

then other types of cells in the gland - mucous neck, parietal, chief, enteroendrocine

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5
Q

How is the function of the GI tract achieved overall? (4 ways)

A

Digestion
chemical - enzymes
mechanical - motility (mixing, grinding)
absorption

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6
Q

Approx how much saliva in ml is secreted?

A

1500ml

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7
Q

Approx how much bile, pancreatic and intestinal secretions in ml?

A

bile - 500ml
pancreatic - 1500ml
intestinal - 1500ml

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8
Q

Approx how much is absorbed in ml from the small intestine?

A

8500ml

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9
Q

What are the transit times in the mouth, oesophagus, small intestine and large intestine?

A

Mouth - 1 min
Oesophagus - 10 seconds
small intestine - 3-6 hours
large intestine - 1-2 days

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10
Q

What are the 4 levels of structural organisation of the GI tract?

A

Mucosa
Submucosa
Muscularis
Serosa

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11
Q

What are the 4 levels of structural organisation of the GI tract?

A

Mucosa (mucous epithelium, lamina propria, muscularis mucosse)
Submucosa
Muscularis (circular and longitudinal muscle layers)
Serosa (connective tissue and peritoneum)

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12
Q

What is swallowing/deglutition?

A

process by which food passes from mouth to stomach

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13
Q

What are the 3 phases of swallowing?

A

Oral phase
Pharyngeal phase
Oesophageal phase

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14
Q

Which phases of swallowing are voluntary and involuntary?

A

Oral - voluntary
Pharyngeal - involuntary
Oesophageal - involuntary

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15
Q

What happens in the oral phase?

A

Tongue moves upwards- compress bolus against hard palate. Respiration inhibited
Retraction of tongue forces bolus into pharynx, closes of oral cavity

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16
Q

What happens in the pharyngeal phase?

A

Involuntary movement pushes bolus from pharynx into oesophagus
Soft palate reflected backward closing nasal pharynx

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17
Q

What happens in the pharyngeal phase?

A

Involuntary movement pushes bolus from pharynx into oesophagus
Soft palate reflected backward closing nasal pharynx

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18
Q

how long and wide is the oesophagus?

A

25cm length and 2cm in diameter from pharynx to the stomach

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19
Q

What happens in the oesophageal phase?

A

Upper oesophageal sphincter relaxes and bolus moves into oesophagus

Start primary peristaltic wave (Vagal – vagus nerve)

Secondary peristaltic wave (Enteric)

Lower oesophageal sphincter relaxes

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20
Q

What does the lower oesophageal sphincter prevent?

A

Prevents reflux of material back into the oesophagus

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21
Q

What are the 4 main regions of the stomach?

A

Cardia, Fundus, Body, Pylorus

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22
Q

What are the two openings of the stomach?

A

Oesophagus and duodenum

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23
Q

What are the 4 main regions of the stomach?

A

Cardia, Fundus, Body (Corpus), Antrum/Pylorus

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24
Q

What is the role of mucus in the stomach?

A

Mechanical abrasion

Prevents autodigestion

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25
Q

What is the function of gastric juice?

A

Initiates the digestive process (proteins)

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26
Q

What is the composition of Gastric juice?

A

Water and ions

HCL - low pH prevents bacterial growth and catalyses cleavage of pepsinogens to pepsin so active form is not denatured by HCL

pepsinogens - pepsin breaks down proteins into peptides

intrinsic factors - glycoproteins bind to b12 allowing digestion in ileum

mucus - protects gastric mucosa - antibacterial/antiyeast

gastrin - hormone from G cells that regulate acid secretion

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27
Q

What are the 3 gastric glands in the stomach and what do they secrete?

A

Cardiac glands - secrete mucus and HCL

Oxyntic glands - mucus, hcl, pepsinogen, intrinsic factor

pyloric glands - mucus, pepsinogen

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28
Q

What cells do you find inside a gastric pit?

A

Mucus neck cells - produce mucus

parietal cells - hcl and instrinsic factors

chief cells- pepsinogen

endocrine cells - g cells (gastrin producing to stimulate acid secretion) and d cells (somatostatin to inhibit acid secretion)

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29
Q

What cells do you find inside a gastric gland?

A

Mucus neck cells - produce mucus

parietal cells - hcl and instrinsic factors

chief cells- pepsinogen

endocrine cells - g cells (gastrin producing to stimulate acid secretion) and d cells (somatostatin to inhibit acid secretion)

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30
Q

What is the gastric pit?

A

Opening/entrance/indentations that leads to the gastric gland

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31
Q

What is the gastric secretory response to a meal?

A

Cephalic phase 30% - sight, smell, thought of food triggers gastric secretion instigated by vagal fibres

Gastric phase 60% - food entering stomach stretches it which triggers secretion via long vagal and short myenteric reflexes

Intestinal phase 10% - intestinal gatrin release in response to distension of duodenum and/or products of protein digestion

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32
Q

What are the three regions of the small intestine?

A

duodenum

jejunum

ileum

4-6 metres long, highly folded, large SA

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33
Q

Where in the GI tract does the most absorption take place?

A

Small intestine

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34
Q

How many strata of folding Is there in the small intestine?

A

3

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35
Q

How long is the large intestine?

A

1.5m in length

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36
Q

What does the large intestine remove?

A

WATER, SALTS, SUGARS, VITAMINS

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37
Q

What are the 5 parts of the large intestine?

A 
1st Cecum 
2nd Ascending colon 
3rd Transverse colon
4th Descending colon
5th Sigmoid colon
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38
Q

What do Peyers patches do?

A

Local immune protection - areas of lymphoid tissues

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39
Q

What are long reflexes in the GI system?

A

Occur with external stimuli (sight and smell of food)
Involves CNS
Alters activity of ENS
it causes changes in motility and secretion

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40
Q

What are short reflexes in the GI system?

A

Internal stimuli (i.e. molecules in lumen)
ENS
Local neural circuits
Causes: changes in motility and secretion

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41
Q

What structures control movement through the tract?

A

Sphincters

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42
Q

What are the names of all the sphincters in the GI tract

A

Upper oesophageal
Lower oesophageal

Pyloric
Ileocaecal

Internal and external anal

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43
Q

What is peristalsis?

A

The contractive and relaxing movements of muscles in the Gi tract causing movement

Relaxation of longitudinal muscle- contraction of circular muscle

Contraction of longitudinal muscle- inhibition of circular muscle

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44
Q

What is peristalsis mediated by?

A

Neurones in the myenteric plexus

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45
Q

What stimulates peristalsis to occur

A

Distension by the bolus of food - oral contraction, aboral (moving away from the mouth) relaxation

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46
Q

What is Hirschprungs disease?

A

Congenital disorder
All or part of colon has no innervation
1:5000 children affected
Surgical removal of the colon

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47
Q

What are enteroendocrine cells?

A

Intestinal ‘taste’ cells

sense luminal contents and respond via release of peptide transmitters and hormones (act as chemoreceptors)

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48
Q

How many hormones and paracrine hormones are involved in the GI tract?

A

in excess of 22

secreted by enteroendorine cells in the mucosa

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49
Q

What is the negative feedback mechanism that controls luminal contents?

A

Hormones detect the luminal contents

stimulate secretions/motility etc

change in luminal contents reduces stimulus, hormone activity adjust

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50
Q

Describe motility of the stomach

A
  1. fasting state
  2. meal enters, LOS, fundus and body relax, allows expansion
  3. peristalsis begins in the middle pushing towards pylorus (end bit of antrum), mixing occurs in the antrum
  4. ‘retropulsion’
5. antral systole = peristaltic wave pushes contents back into body
some chyme (the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food) moves into duodenum
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51
Q

What 3 things does the stomach act as?

A

Reservoir to store food

preparatory chamber - break down injected materials

emptying regulator - responds to feedback from duodenum. controls rate of release of calorie, H+ and particles into the duodenum.

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52
Q

What is chyme?

A

the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.

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53
Q

Describe how peptic ulcers form

A

Break in mucosal barrier exposing underlying tissue to corrosive action (acid, proteases)

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54
Q

Why do solid empty slower than liquids?

A

Lag due to time to reduce particle size (1mm diameter)

liquids empty 2-3 minutes faster

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55
Q

What are the symptoms of gastric ulcers?

A

Abdominal pain
Bloating
Nausea/vomiting
Bleeding- haemorrhage and anaemia

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56
Q

Why do gastric ulcers form? - endogenous and exogenous factors

A

Endogenous Factors
Anxiety
Parasympathetic output (Ach, Gastrin) →↑acid
Stress
Sympathetic output (Ad) → ↓ HCO3/mucus

Exogenous Factors

Diet
Alcohol - damages cells, stimulates parietal cell
Coffee – stimulates parietal cell

Non-steroidal anti-inflammatory drugs (NSAIDs)
↓prostaglandin production →↓inhibition of acid

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57
Q

What bacteria can cause gastric ulcers?

A

Helicobacter pylori

58
Q

What bacteria can cause gastric ulcers?

A

Helicobacter pylori - release proteases and endotoxins which break down stomach lining tissue

59
Q

What ducts does the gall bladder and pancreas use for secretions?

A

Bile and pancreatic ducts

60
Q

How much of the pancreas is made up of exocrine and endocrine glands and what are they and what do they secrete?

A

Exocrine - 86% - Acinus
secrete water, ions, bicarbonate (neutralises duodenal contents to prevent damage and ph for enzymes) and enzymes for digestion

Endocrine 2% - islets of langerhands - a cells (glucagon), b cells (insulin)

61
Q

What is an exocrine gland?

A

glands that produce and secrete substances onto an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, and mucous

62
Q

What is an endocrine gland?

A

glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct.

63
Q

What do duct cells secrete and how does this help within the small intestine?

A

Duct cells secrete a watery, bicarbonate-rich fluid which flush the enzymes through the ducts and play a pivotal role in neutralizing acid within the small intestine.

64
Q

Which ducts receive secretions from acini?

A

Intercalated ducts - flattened cuboidal epithelium extends into the lumen of the acinus to form centroacinar cells

65
Q

Which ducts receive secretions from intercalated ducts?

A

Intralobular ducts - cuboidal and seen within the lobules

66
Q

Which ducts transmit secretions from intralobular ducts to the major pancreatic duct?

A

Interlobular ducts - found between lobules

67
Q

Where does the main pancreatic duct receive secretions from?

A

The interlobular ducts

68
Q

Which type of duct is not present in the pancreas?

A

Striated ducts

69
Q

Which enzymes are responsible for the digestive function of the pancreas?

A 
Digest proteins (acinar cells secrete): 
Trypsinogen - trypsin
Chymotrypsinogen - chymotrypsin
Proelastase - elastase
Procarboxypeptidase - carboxypeptidase

Lipase and phospholipase- Fats
Nucleases- Nucleic acids
α-amylase- Carbohydrates

70
Q

Which cells secrete, bicarbonate, water and ions??

A

Ductal cells and centroacinar cells (extension of the intercalated duct cells into each pancreatic acinus)

71
Q

What is cholecystokinin?

A

a hormone which is secreted by cells in the duodenum into the blood stream in response to proteins and fats in chyme and stimulates the release of bile from the gallblader into the intestine and the secretion of enzymes by the pancreatic acinar cells.

72
Q

What is Secretin?

A

A hormone produced by the S cells of the duodenum which is stimulated by HCL in chyme to be released into the blood (pH <5) .

Secretin helps regulate the pH of the duodenum by (1) inhibiting the secretion of gastric acid from the parietal cells of the stomach and (2) stimulating the production of bicarbonate from the ductal cells of the pancreas

73
Q

What are some of the functions of the liver?

A

Protein synthesis
Storage - triglycerides, glycogen, some vitamins (A)
Gluconeogenesis
Toxins - conjugation, breakdwn
Bile synthesis and secretion of bile acids and bilirubin

74
Q

What is bilirubin?

A

an orange-yellow pigment formed in the liver by the breakdown of haemoglobin and excreted in bile

75
Q

Where is bile stored?

A

Gall bladder

76
Q

What are the main functions of bile?

A

Adequate pH - enzymes in the SI work best in alkaline conditions
Facilitate fat digestion/ emulisification
Excretion of waste products (cholesterol/bilirubin) by secretion into the bile

77
Q

What is the composition of bile?

A

Water and ions- alkali

Bile acids- digestion and absorption of dietary fats (micelle formation) 70%

Proteins- protect against infection

Bile pigments- breakdown products of hemoglobin (bilirubin)

Organic molecules
Cholesterol (4%)
Phospholipid- Lecithin (20%)

78
Q

What is the function of the gallbladder?

A

Alters bile composition and delivery:

absorption of Na, cl, water - concentrates the bile

secretion of H+ - neutralise alkaline mucin and protect surface epithelium

storage of bile

contracts and delivers the bile (cephalic 20% via Acetycholine, intestinal phase 80% CCK)

79
Q

How is bile delivery controlled? (hormones)

A

Secretin stimulates secretion

CCK - stimulates release of bile by relaxing sphincter of Oddi and contracting gall bladder

80
Q

What are gall stones?

A

Calcified stones made up of cholesterol, bilirubin and calcium

81
Q

What are the main causes of gallstones?

A 
Genetics
Body weight
Decreased mobility of gall bladder
Diet 
Other diseases (cirrhosis, sickle cell)
82
Q

Why does the microvilli have a large surface area?

A

Large number of tiny projections on the surface of small intestinal epithelial cells increases the surface area for nutrient absorption from the lumen

83
Q

What does the glycocalyx do?

A

Unstirred layer on top of microvilli helps molecules to stay in the surface once absorbed

84
Q

Name some brush border enzymes

A

Maltase, lactase, sucrase, dipeptidases

85
Q

What type of transport is the glucose/galactose carrier?

A

Co-transport - Na dependent

energy needed to maintain Na gradient (secondary active transport)

86
Q

What type of transport moves fructose into the cell?

A

GLUT2 carrier - facilitated diffusion

87
Q

Where do the transported carbohydrates in the small intestine go to?

A

capillaries –> hepatic portal vein –> pass through liver

88
Q

What are the 3 places of protein digestion in order? What enzymes act in these places and what is produced?

A

stomach
Gastric pepsin
Protein-polypeptide–> small peptide

duodenum
Pancreatic proteases
Protein- polypeptide –> small peptides and amino acids

brush border
Peptidases
Large peptides —> small peptides and amino acids

89
Q

What type of transport takes small peptides and free amino acids into a cell?

A

Active transport

90
Q

How are free amino acids moved into capillaries?

A

Facilitated diffusion

91
Q

What do lipases digest?

A

Lipids into monoglycerides, fatty acids, glycerol in the pancreas

92
Q

In what form are the lipids transported across the unstirred layer in the small intestine?

A

Micelles

93
Q

What are triglycerides combined with to form chylomicrons within cells?

A

Cholesterol, protein, phospholipids

94
Q

Where do chylomicrons ultimately end up

A

Diffusion into lacteals

Return to systemic circulation via thoracic lymph duct

95
Q

What are three reasons malabsorbtion can occur?

A

Absent or defective digestive enzymes
Defects in transporter proteins
Diseases or infections of small intestine

96
Q

What are the symptoms of malabsorption?

A

steatorrhea (frothy greasy stools), diarrhoea, weight loss

97
Q

What are some examples of conditions where malabsorption occurs?

A

Lactase deficiency - lactose intolerance
Coeliac disease – abnormal immune response to gluten – loss of mucosal epithelium
Pernicious anaemia – malabsorption Vit B12 in ileum due to antibodies to intrinsic factor

98
Q

What are tenia coli?

A

three separate longitudinal ribbons (taeniae meaning ribbon in latin) of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons.

99
Q

What are Haustra?

A

small pouches caused by sacculation (sac formation), which give the colon its segmented appearance

100
Q

What type of cell is there a high concentration of in the large intestine?

A

Goblet cells

101
Q

What are the main functions of the large intestine?

A

High mucus secretion
all absorption by diffusion

efficient water reabsorption (aided by cl- absorption in exchange for hco3-)

Hco3= buffers acid produced by bacterial fermentation (indigestable products)

absorbing essential vitamins produced by gut bacteria

converts food into faeces

102
Q

Which part of the GI tract has the most gut flora?

A

The colon

103
Q

What essential nutrients are produced by gut bacteria?

A

Folic acid

vitamin K

b12

biotin

thiamin

short chain fatty acids

104
Q

Where does dietary fibre mainly come from?

A

The indigestible portion of plant foods

105
Q

What is the role of dietary fibre?

A

Motility - decreases gastric emptying in the stomach, increases motiliy of colon and intestines

adsorption - holds water, slows absorption of enzymes and nutrients

colonic bacterial substrate

prevention and treatment of constipation, haemorrhoids

reduces risk of colon cancer/

106
Q

What are the sources of gastrointestinal gas?

A

Swallowed air, result of neutralisation of acid and bacterial metabolism, diffusion from blood (small). bacterial fermentation

gases - hydrogen, methane (ammonia, hydrogen sulphide, indole, skatole, volatile amines)

107
Q

Describe mechanisms responsible for expulsion of GI contents via the mouth

A

Reversal of peristalsis

GI tract as a trigger for vomiting

108
Q

What is the net absorption in % in the small intestine of protein, carb, fats?

A

100% protein
100% digestible carbohydrate
95% fats
Water, electrolyte (eg Na+, Cl-, Ca2+, Fe2+) vitamins (eg B12)

109
Q

What is excreted?

A

indigestible fibre, bacteria, inorganic material, fat derivatives, desquamated cells, mucus

110
Q

What is the normal balance between absorption and secretion?

A

absorption greater than secretion

111
Q

What is diarrhoea?

A

Increase stool volume or increased frequency of defecation

112
Q

What are the 4 types of diarrhoea?

A
  1. osmotic
  2. secretary
  3. inflammatory/infectious
  4. deranged motility
113
Q

What is osmotic diarrhoea? What are the causes?

A

increased solutes in lumen causes water to move down concentration gradient from blood to lumen of the gut.

Less water is reabsorbed

causes - poorly absorbed substrate or a malabsorption disorder e.g. lactose intolernce

114
Q

What is secretory diarrhoea? What are the causes?

A

Increased secretion of water into the lumen (exceeds absorption)

causes: Cholera toxin - opening of chloride channels can increase secretion of water,
hormomes, drugs, caffeine, laxatives, bile acid malabsorption

these cause some change in the function of the cells lining the gut

115
Q

What is the mechanism of cholera producing diarrheoa?

A

cholera produces a toxin - binds to sugars on the surface of the cells - enters the cell (activated by cell RER)- binds to a G protein - activates adenylate cyclase - this produces cAMP which is a second messenger that can activate other processes - activates a chloride channel on the surface - pumps chloride ions into the lumen of the gut - which causes movement of sodium ion in to the lumen of the gut - water follows this osmotic gradient through the tight junctions in cells

116
Q

What is secretory diarrhoea? What are the causes?

A

Increased secretion of water into the lumen (exceeds absorption)

causes: Cholera toxin - opening of chloride channels can increase secretion of water,
hormomes, drugs, caffeine, laxatives, bile acid malabsorption

these cause some change in the function of the cells lining the gut

117
Q

What is inflammatory/infectious diarrhoea? What are the causes?

A

Bacteria can express proteases that damage the epithelial absorptive lining of the gut, less water can be absorbed

118
Q

What is deranged motility diarrhoea? What are the causes

A

altered transit time through the gut hence less time for water reabsorption -

IBS, can result in constipation and diarrhoea

119
Q

What is the purpose of segmented contractions in the colon?

A
  1. Retain material in the proximal colon
    - Fermentation
    - Water absorption
  2. Mixing contents - allows things to be absorbed and bacteria to do its job - fermentation
120
Q

How is defecation controlled? (nervous)

A

Faeces moved into the rectum, leading to distension. This activates stretch receptors in the lower sigmoid and rectum- afferent signals to the spinal cord

If it is convenient to defecate, voluntary motor nerves are inhibited allowing the external anal sphincter to relax

Symp and Parasymp- Stimulate contraction of the rectum and relaxation of the internal anal sphincter

121
Q

What are two reasons for incontinence?

A

Pelvic floor damage

Pudendal nerve damage

122
Q

What processes help continence?

A 
Rectal accommodation (relaxation of colon/rectum)
Sphincter closure
123
Q

Why may there be failure in defecation?

A

Spinal injury

Outlet obstruction

124
Q

What internal changes occur during defecation?

A

Colorectal contraction
Raised abdominal pressure

Sphincter relaxation
Internal (autonomic)
External (somatic)

125
Q

What is emesis and why is it imporant?

A

The action of vomiting

protective mechanisms to prevent damage to GI tract and ingestion of contaminated/toxic substances

126
Q

What are the detectors of toxin?

A
  1. -ingestion
    Smell, sight, taste
  2. Pre-absorbtion
    Toxin detection in the lumen by
    Mechanoreceptors and chemoreceptors
    Causes neutralisation/expulsion (vomiting)
127
Q

What are the detectors of toxin?

A
  1. -ingestion
    Smell, sight, taste
  2. Pre-absorbtion
    Toxin detection in the lumen by
    Mechanoreceptors and chemoreceptors
    Causes neutralisation/expulsion (vomiting)
  3. Chemoreceptive trigger zone - area postrema in the medulla
    Outside of blood brain barrier- samples toxins in the blood

Induces nausea to prevent further ingestion and activates vomiting centres

128
Q

What centre can be directly activated with emetics?

A

Area postrema in the medulla - contains chemoreceptive trigger zone recognises toxins in the blood

129
Q

Give some examples of appropriate and inappropriate vomiting?

A

Food poisoning
Bowel obstruction
Bowel disease

Motion sickness
Cancer therapy
Pregnancy

130
Q

What are signs of nausea?

A 
Pallor
Sweating
Salivation
Irregular breathing
Increased heart rate 
Retching (several, increased force)
131
Q

What movements in the stomach and abdomin occur during nausea and then emesis?

A
  1. Retrograde Giant contractions return intestinal contents to the stomach
  2. The proximal stomach relaxes to accommodate returning intestinal contents
  3. Antral motility (pushing back the other way) inhibited to prevent gastric emptying
  4. Expulsion caused by contractions of the diaphragm and abdominal wall
132
Q

Describe the act of vomiting

A

Deep inspiration allows closure of glottis- protects respiratory tract
Air and saliva drawn into esophagus- protection and decrease esophageal pressure
Soft pallet elevated to prevent entry into nasopharynx
Expiration against closed glottis and abdominal contraction- increase intra abdominal pressure
Relaxation of the LOS (oesphogeal sphincter)
Passage of contents into esophagus
Relaxation of the UOS
Violent expulsive force- stomach and abdominal contraction

GI smooth muscle
Relaxation of all areas from gastric body to upper oesophagus
Violent contractions of gastric antrum pushing material up

Respiratory system
Slow deep inspirations to decrease oesophageal pressure

Skeletal muscle
Contraction of abdominal muscle

Retching
Upper oesophageal sphincter remains closed

Vomiting
Upper oesophageal sphincter opened

133
Q

How is the GI tract stimulated for emesis?

A

Distension (stomach and duodenum)
Irritation of back of throat
Chemical or toxin

134
Q

How is the chemoreceptor trigger zone stimulated for emesis?

A

Anaesthesia
Drugs
Radiation

135
Q

How is the genitourinary system, hypothalamus/cerebellum and vestibular apparatus stimulated for emesis?

A

Injury/infection (geno)

stimulation or injury (hypothalamus/cereblleum)

motion sickness (vestibular)

136
Q

What is the role of 5-HT (serotonin) in the emetic pathway?

A

produced by neuroendocrine cells lining the gut especially small intestine

respond to emetic signals e.g. radiation, injury, infection, toxins and release 5HT molecule that binds to its receptor 5HT3 in the nervous system - on vagus nerve

can also enter blood stream and act on chemoreceptor trigger zone

137
Q

What are the three phases of the emetic reponse to anticancer chemo?

A

Anticipatory- Conditioned response (at the thought of receiving chemo)

Acute- Enterochromaffin cells release 5HT which acts on 5-HT3 on the chemoreceptor trigger zone

Delayed- Damage to epithelial/cell breakdown products evokes mediator release (including 5HT )

138
Q

How do anti-emetics work?

A

blocking activation of the vomiting centre - chemoreceptor trigger zone

e.g. Ondanstron - 5HT3 antagonist

5-HT3 receptor antagonists have revolutionized treatment of nausea and vomiting in cancer patients.

139
Q

What does the pancreas feature?

A 
Acinar cells
Centroacrinar cells
Intercallated ducts
Intralobular duct
Islets of langerhans
140
Q

Where are enzymes involved in protein degradation found?

A

Zymogen granules

141
Q

Name some pancreatic enzymes

A 
Digest proteins: 
Trypsinogen - trypsin
Chymotrypsinogen - chymotrypsin
Proelastase - elastase
Procarboxypeptidase - carboxypeptidase

Lipase and phospholipase- Fats
Nucleases- Nucleic acids
α-amylase- Carbohydrates

142
Q

What do acinar cells produce?

A

a small amount of protein (enzyme rich) fluid

Passes through the intercalated duct- ductal cells and centraacinar cells secret bicarbonate, water and ions

MDENT210 (7 decks)

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