Gastrointestinal Pathophysiology Flashcards
(112 cards)
1
Q
How many feet long is the digestive tract from the mouth to the anus?
A
15 foot
2
Q
Describe the diameter and wall composition of the digestive tract.
A
Variable along the tube.
3
Q
Is the digestive tract technically inside or outside the body ?
A
Outside
4
Q
What issues arise from the digestive tract being technically outside the body?
A
This means that bacteria can enter without being dangerous. However, if the GI tract is ruptured, the bacteria may spread.
5
Q
What is the purpose of the mouth in the GI tract?
A
Ingestion
Chewing
Moistening of food
6
Q
What is the purpose of the liver in the GI tract?
A
Bile secretion
7
Q
What is the purpose of the large intestine in the GI tract?
A
Absorption of water and ions.
Storage.
Formation of faeces.
8
Q
What is the purpose of the salivary glands in the GI tract?
A
Salivation
9
Q
What is the purpose of the oesophagus in the GI tract?
A
Swallowing
10
Q
What is the purpose of the stomach in the GI tract?
A
Storage after ingestion.
Mixing of food.
Digestion.
11
Q
What is the purpose of the pancreas in the GI tract?
A
Digestive juice secretion.
12
Q
What is the purpose of the small intestine in the GI tract?
A
Digestion
Absorption
13
Q
What is the purpose of the rectum in the GI tract?
A
Storage of feces
14
Q
What is the purpose of the anus in the GI tract?
A
Defecation.
15
Q
How many pairs of salivary glands are there in the human body?
A
3 but more salivary tissue is being found.
16
Q
Describe mechanical digestion of food.
A
Large lumps are made into small lumps.
17
Q
Describe chemical digestion of food.
A
High molecular weight compounds are made into low molecular weight compounds.
18
Q
What is required for food to be absorbed?
A
It must be able to cross the wall of the GI tract.
19
Q
What are the 5 layers of the GI tract?
A
- Mucosa
- Sub-mucousal plexus
- Smooth muscle
- Myenteric plexus
- Smooth muscle within serosa
20
Q
What is the purpose of the mucosa in the GI tract?
A
It lines the lumen of the GI tract and is used for absorption, secretion and mechanical strength.
21
Q
What is the sub-mucosal plexus of the GI tract?
A
Nerves for regulation of gut.
22
Q
Describe the orientation of the smooth muscle of the GI tract.
A
When it contracts, it narrows down the lumen.
23
Q
Describe the orientation of the smooth muscle within the serosa of the GI tract.
A
Longitudinally orientated.
24
Q
Describe rhythmic segmentation and its purpose.
A
Nonadjacent segments of the intestine alternately contract and relax thereby mixing chyme.
25
Describe propulsive peristalsis
Oral to anal transport - wave of contraction preceded by a wave of relaxation.
26
What are the 3 types of muscle movement of the GI tract?
Rhythmic segmentation
Propulsive peristalsis
Sustained tonic contractions
27
Describe sustained tonic contractions of the GI tract and their purpose.
Sphincter such as the lower oesophageal, pyloric and ileocaecal sphincter ensure unidirectional transport and prevent reflex.
28
What are the purpose of Sphincters in the oesophagus?
They prevent back flow by closing the opening of the Oesophagus to the stomach.
29
What is caused by failing of the Sphincters in the Oesophagus?
Gastroesophageal reflux disease and possible heartburn.
30
What is the purpose of the pyloric sphincter?
Used to control the flow from the stomach to the small intestine and to ensure the SI is not overloaded.
31
Describe sensory innervation of the GI tract.
Sensory components detect presence of the food in the gut mechanically and chemically.
- Submucousal Plexus controls secretion from glands of the mucosa.
- Myenteric Plexus controls the muscle layers.
32
What makes up the enteric nervous system?
Submucousal and Myenteric Plexus
33
Via what branch is the autonomic nervous system likely to influence the gut?
Parasympathetic
34
Describe what causes Gastrin to be secreted, where it is secreted from and what is does this in response to.
Gastrin is release by G-cells in the stomach to stimulate motility and acid release.
This occurs in response to food being in the stomach to stimulate digestion or can occur in response to vagal stimulation.
35
Describe what causes Secretin to be secreted, where it is secreted from and what is does this in response to.
Secretin is secreted by the S-cells in the duodenum in response to low pH. This causes the pancreas to secrete bicarbonate which can be used to neutralise the acid.
The contents of the intestines then become more neutral and allow digestion to continue. Damage to the GI tract is also prevented.
36
Describe what causes Cholecystokinin to be secreted, where it is secreted from and what is does this in response to.
CCK is secreted by the intestines in response to protein rich chyme. It slows gastric emptying to allow digestion of food to be completed.
It is also involved in satiety and sends signals to the brain to make you feel full.
37
How does weight control an individuals feeding behaviour?
Adipose tissue signals to the appetite controlling signals in the brain which aids control of the GI tract.
38
What causes people to become fat?
Imbalance in the determinants of body fat stores.
- Intake (type, amount, CNS control).
- Expenditure (depends mostly on lean mass)
39
Describe the accuracy of formulae used to calculate the energy requirements of individuals of various weights.
Accuracy of these formulas has been challenge.
An overestimate in energy requirements has been found common due to a proportional decrease in metabolically active tissues. (e.g. a lot of fat tissues is not greatly metabolically active).
40
What 2 factors are used for satiety signals?
Cholecystokinin and leptin
41
Describe the satiety single produced by. Cholecystokinin and how this is produced.
This is secreted by the GI tract during and after a meal in response to the chemical and mechanical presence of food in the intestines.
It inhibits motility in preceding sections of the GI tract and also feedbacks to the brain to inhibit appetite.
42
Describe the satiety signal produced by Leptin and describe how this is produced.
This is a hormone produced by fat cells in proportion to the amount of fat an individual has.
(More body fat = more leptin).
- It travels in the bloodstream via the hypothalamus where it surpasses appetite.
43
Describe the effects caused by congenital leptin secretion deficiency.
- Hyperphagia (massive obesity).
| - Hyperinsulinemia.
44
What is hyperphagia?
Massive obesity
45
What causes congenital leptin secretion deficiency and what is it?
If there is a deficiency in Leptin or Leptin reception, there will be reduced appetite suppression and so feelings of hunger will be frequent/constant.
There will be no break in hunger and feeding behaviour.
46
How is leptin impairment thought to manifest in obese individuals.
Leptin signalling is thought to be impaired giving leptin resistance which leads to a lack of appetite suppression.
47
What is Ghrelin and what is its function and how does it work?
It is a protein made by the endocrine cells of the stomach and the GI tract.
Acts on the hypothalamic receptors to stimulate appetite.
48
Describe Ghrelin in individuals with Prader-Willi syndrome.
High Ghrelin levels in Prader-Willi syndrome lead to a voracious appetite and therefore often obesity.
49
What is the only GI hormone that promotes appetite?
Ghrelin
50
What causes contribution to putting on weight after a diet?
Increase in Ghrelin
51
What is Peptide YY3-36 and what is its purpose?
It is produced in the stomach cells and has a reducing effect on Ghrelin secretion.
52
Describe the difference in Peptide YY3-36 production in different people.
Lean people tend to produce more of this hormone than obese people.
53
Outline how leptin and gherkin produce opposite effects in the brain.
Catabolic cell group:
POMC and CART
- Activated by Leptin and inhibited by Ghrelin.
Anabolic cell group: NPY and AgRP
- Activate by Ghrelin and inhibited by Leptin
54
What effects do Ghrelin and Leptin have on each other?
Antagonistic
55
What accounts for all the well-known psychotropic effects of cannabis?
CB1 receptors
56
What does activation of CB1 endocannabinoid receptors cause?
Food ingestion (attenuation of satiety signals), relaxation, pain reduction and extinction of aversive memories.
57
Why was use of Rimonabant CB1 inverse agonist withdrawn?
It was effective but cause anxiety because pain reduction and relaxation effects were removed as well as feeding behaviours.
58
Describe the time courses of regulation in the GI tract and what causes each type.
From gut for day to day regulation.
From adipose tissue for longer term regulation.
59
What controls regulation of appetite?
Hormonal and neurological controls are interlinked so that disruption of one causes a shift in the homeostatic balance.
60
Describe hypothalamic obesity.
Injury or lesions in the hypothalamus may result in a pattern of weight gain that is characterised by abrupt onset and rapid acceleration.
61
What are some of the causes of hypothalamic obesity?
Craniopharyngioma, head trauma, cancers, sarcoidosis, aneurysm, surgery, radiation, metastasis
62
What are the classifications of GI disorder?
Motility disorders
Disorders of secretion
Gi manifestations of systemic diseases
63
Describe GI motility disorders and give some examples.
GI motility affected by damage to GI smooth muscle or neural or hormonal controls (e.g. Hirschsprung's disease or Gastroparesis).
64
Describe GI disorders of secretion and describe one.
Either increased or decreased levels of secretion that can make the GI tract susceptible to damage.
(E.g. increased acid or decreased mucous secretion can lead to ulcer development).
65
Describe a GI manifestation of systemic disease
E.g. hyperthyroidism causing hypercalcaemia resulting in gastric dysmotility.
66
What symptoms would you expect with problems of the GI tract?
- Pain (visceral – hard to localise)
- Dyspepsia (‘upset stomach’ – non-specific term used to cover many problems)
- Dysphagia (difficulty swallowing)
- Ileus (paralysis of the intestines)
- Nausea and vomiting
- Anorexia and weight loss
- GI bleeding
- Constipation
- Diarrhoea
67
What symptoms of GI dysfunction are caused by the brain? Describe the mechanisms of this and what causes this.
Nausea and vomiting is initiated by the vomiting centre in the brain.
The medullary vomiting centre stimulates contraction of the oesophageal muscle, diaphragm and respiratory muscles to reflex contents of stomach.
This may be activated by sensory stimuli, emotions, various drugs, touch receptors in the throat or sensory receptors in the gut.
68
What is pre-oesophageal dysphagia?
Problems outside of the oesophagus due to lack of control of muscles of swallowing.
69
Name a type of pre-oesophageal dysphagia.
Parkinson's disease
| Myasthenia Gravis
70
What different types of Oesophageal dysphagia are there and describe each.
- Motility disorders such as oesophageal spasms.
- Intrinsic obstruction of the oesophagus that may be caused by oesophageal rings, webs or chronic inflammation.
- Extrinsic obstruction (blockages due to pressure on the oesophagus). E.g. caused by tumours.
71
What is the purpose of the Lower Oesophageal Sphincter.
Prevents acid reflux
72
What can occur due to inappropriate opening of the lower oesophageal sphincter?
This can cause acid reflux which damages the oesophagus and leads to heart burn. Gastroesophageal reflux disease (GORD) may also occur.
73
What are the treatment options for GORD?
Using proton pump inhibitors or histamine antagonists to reduce acid secretion.
74
What is Barrett’s Oesophagus and what may this cause?
Normal cells are protected from acid damage because the interstitial cells propagate into the oesophagus. This can lead to adenocarcinoma and fibrosis may lead to stenosis in the oesophagus.
75
What can influence the development of GORD?
- Abnormal tone of lower oesophageal sphincter
- Chemical composition of regurgitated gastric contents
- Integrity of the oesophageal mucosal barrier
- Increased intra-abdominal pressure
- Irritants in food (spice, pepper, alcohol)
76
What are peptic ulcers?
A deep defect of the mucosa related to the action of hydrochloric acid causing erosion of the stomach wall.
77
Where in the GI do peptic ulcers extend to?
Extend into the muscular layer of the gastric walls.
78
What are the causes of peptic ulcers and how does this occur?
Most are related to infection by helicobacter pylori. These bacterium live underneath the protective mucous lining of the stomach. They damage the lining of the stomach causing reduced resistance to pepsin degradation and damage to the duodenum which reduces bicarbonate section. This leads to inflammation and secretion of more stomach acid.
79
What are the symptoms of peptic ulcers?
- GI bleeding (if chronic, iron deficient anaemia may be caused)
o Massive bleeding may cause faeces to turn black due to HCl breakdown of Haemoglobin
- Perforation – deep ulcers can penetrate the entire stomach wall and allow gastric contents into the peritoneal cavity – peritonitis
- Penetration – duodenal ulcers may penetrate into other organs such as the pancreas leading to pancreatitis. This leads to elevated amylase and lipase levels in the blood.
- Stenosis – fibrosis in wall of pyloric channel
80
What effect does Zollinger-Ellison syndrome have on peptic ulcers and how?
Increases in their incidence - Neuroendocrine tumour results in excessive and uncontrolled gastrin production, thereby increasing acid production and increasing incidence of ulcers.
81
Describe treatment of Zollinger-Ellison syndrome.
Treatment involves proton pump inhibitors to block acid.
82
What is Gastroparesis and what does it do?
the stomach is contractile and contains a pacemaker which causes sweeps of contraction to occur around 3 times per minute. This grins up the food and expels it into the duodenum.
83
What causes Gastroparesis to occur?
When waves of depolarisation spread
84
What are the causes of Gastroparesis?
Usually caused by nerve damage to the vagus nerve. Could be caused by tumours blocking stomach outlets.
85
What are the symptoms of Gastroparesis?
- Results in fullness after a few bites of food.
- Nagging ache in the stomach
- Vomiting
- Heartburn
- Regurgitation into the mouth
86
What are the treatments for gastroparesis?
- Manage underlying cause
- Manage food intake
- Frequent food intake
- Medications
87
When in life is inflammatory bowel disease likely to occur?
The 3rd decade of life.
88
What are the 2 types of inflammatory bowel disease?
Chron's disease
| Ulcerative Colitis
89
What is Chron's disease?
Transmural inflammation of the terminal ileum
90
What are the symptoms of Chron's disease?
Abdominal pain, fever, non-bloody diarrhoea
91
How does Chron's disease hinder digestive function?
Depth of inflammation results in narrowing of the lumen in Chron's disease.
92
Where in the GI tract does ulcerative colitis usually occur?
Predominantly in the rectum and descending colon
93
What are the symptoms of ulcerative colitis?
Pain, fever, malaise and often dehydration.
94
What causes damage to the GI tract in ulcerative patients?
Backwash ileitis (inflammation spreading back up the GI tract)
95
Describe the depth of inflammation in ulcerative colitis.
Not so deep - limited to the mucosa.
96
What cause Ulcerative Colitis patients to be at a greater risk of colon cancer?
The intestinal walls tend to thin and may possibly allow intestine to dilate. This causes toxic megacolon.
97
Why do GI problems cause malabsorption syndromes ?
- Failure in digestion
| - Failure in absorption/ transport.
98
What causes malabsorption syndromes of the GI tract?
- Infection
- Pancreatic Dysfunction
- Autoimmune (e.g. coeliac disease – reaction to gluten leading to inflammation)
- Enzyme deficiency (lactase deficiency leading to lactose intolerance).
99
What affects the symptoms of malabsorption syndromes.
Symptoms depend on what is not absorbed.
100
Describe what Diverticulosis is and when it develops.
Pockets or projections of colon develop at weak points in the colon wall. This appears later in life
101
Where do most diverticula occur and why?
In the sigmoid colon where the greatest pressure is.
102
What are the symptoms of diverticulosis?
Often none, may eventually affect function leading to constipation and diarrhoea.
Perforation of the Gi tract may occur, allowing bacteria to escape via the gut leading to infection.
103
How is diverticulosis treated?
Fibre rich diet and lack of stress may be preventative but surgery is required to remove disease portions of the colon.
104
How is the GI tract affected in Hirschsprung's disease?
There is a lack of innervation due to a missing enteric nervous system. This reduced contractions within the GI tract.
Lack of enteric nervous system also leads to construction sections in the gut which cause pressure to build-up and in preaching sections of the colon.
105
What are some of the knock on effects of Hirschsprung's disease?
Aganglionic section of the large intestines.
Section of bowel may enlarge.
106
What are the symptoms of Hirschsprung's disease?
Severe constipation, anaemia
107
What treatments are there for Hirschsprung's disease?
Initially treated with a colostomy bag, then by removing ganglionic section or pull through surgery to pull healthy section of bowel through affected portion.
108
Where is it most common for cancers to affect the GI tract?
In the large intestines?
109
What are the greatest causes of cancers affecting the GI tract.
Dietary issues (increased risk if low residue, high fat diet).
Hereditary
110
What are the symptoms of cancers affecting the GI tract.
Initially asymptomatic, eventually may obstruct gut and may undergo metastasis (especially to the liver)
111
What is irritable bowel syndrome?
Unusual contractions of the digestive tract leading to pain and unpredictable bowel movements.
112
What causes irritable bowel syndrome?
Result of some foods (caffeine, alcohol, spices) but may be due to an overabundance of nerves supplying the gut leading to the gut becoming hypersensitive.
