WEEK 3 Flashcards
1
Q
Where are carbohydrates absorbed? What are they broken into?
A
The small intestine
- glucose
- galactose
- fructose
2
Q
What is the mechanism behind the production of (i) glucose (ii) galactose (iii) fructose from a carbohydrate?
A
(i) Sodium dependant cotransport
(ii) sodium dependent cotransport
(iii) facilitated diffusion
3
Q
Describe how (i) secondary active transport (ii) facilitated diffusion work for carbohydrates?
A
(i) SGLT1 located on the apical membrane transports glucose and galactose
(ii) GLUT5 transports fructose across the apical membrane
4
Q
Where does protein digestion (i) begin (ii) complete/end?
A
(i) in the stomach with pepsin
(ii) small intestine with pancreatic and brush-border proteases
5
Q
What is the function of (i) endopeptidases (ii) exopeptidases?
A
(i) hydrolyse the interior peptide bonds of proteins
(ii) hydrolyse one amino acid at a time
6
Q
Pancreatic proteases are secreted as inacitve precursors, what is the importance of tryspinogen?
A
It is converted to the active from trypsin, by the brush border enzyme enterokinase
- the trypsin catalyses the conversion of the other inactive precursors to active enzymes
7
Q
Proteins are absorbed in the small intestine. What is the mechanism behind producing (i) amino acids (ii) dipeptides (iii) tripeptides?
A
(i) sodium dependent cotransport
(ii) H+ dipeptide cotransport
(iii) H+ tripeptide cotransport
8
Q
What must happen to dietary lipids before digestion and absorption can occur? Why is this the case?
A
They must be solubilised because they are hydrophobic (insoluble in water)
9
Q
Where does digestion of lipids begin? Where is it completed?
A
Begins in the stomach with the action of lingual and gastric lipases
- completed in the small intestine with the action of pancreatic enzymes
10
Q
What is the key role of gastric lipase?
A
to slow the rate of gastric emptying so that pancreatic enzymes are able to digest lipid
- CCK secreted from I cells of duodenal and jejunal mucosa in response to the presence of monoglycerides and fatty acids and small peptides and amino acids
11
Q
What emulsifies dietary lipids?
A
bile salts
lysolecithin
products of lipid digestion
12
Q
What does emulsification of dietary lipids produce?
A
small droplets of lipids dispersed in an aqueous solution creating a large surface area for pancreatic enzyme digestion
13
Q
What are secreted to complete the digestion of lipids?
A
Pancreatic enzymes (pancreatic lipase, cholesterol ester hydrolase and phospholipase A2) - Colipase (a protein)
14
Q
What is the structure of a chylomicron?
A
100nm diameter
- have a core of triglycerides and cholesterol ester-phospholipids and apoproteins on the outside (80%/20%)
15
Q
Where are chylomicrons found/stored? Where do they move?
A
Packaged into secretory vesicles on the golgi membrane and are exocytosed across the basolateral membrane
- they are too big to enter vascular capillaries but enter the lymphatic capillaries (lacteals) by moving between endothelial cells that line the lacteals
16
Q
What does the lymphatic circulation do with chylomicrons?
A
They carry them to the thoracic duct
- where they are emptied into the blood stream
17
Q
Lipids are absorbed in the small intestine. By which mechanism are fatty acids, monoglycerides and cholesterol produced?
A
- bile salts form micelle
- diffusion of products into intestinal cells
- re-esterification within the cell to triglycerides and cholesterol
- chylomicrons form in the cell and transfer to lymph
18
Q
What are the tight junctions like in the (i) small intestine (ii) large intestine?
A
(i) leaky (permeable via the paracellular route)
ii) tight (impermeable via the paracellular route
19
Q
What parts of the SMALL intestine are responsible for (i) absorption (ii) secretion?
A
(i) villi
(ii) crypts of Lieberkuhn
20
Q
What parts of the LARGE intestine are responsible for (i) absorption (ii) secretion?
A
(i) surface epithelial cells
(ii) colonic glands
21
Q
For an examination of the abdomen/GU, how should the patient be positioned?
A
Comfortably supine with head resting on 1 or 2 pillows
- have abdomen exposed from xiphisternum to symphysis pubis
22
Q
What is involved in the general inspection of an abdominal and GU examination?
A
- Look AROUND pt
- sick bowls
- empty bottles/cans - Look AT pt
- do they look well? in pain?
- nutritional state (cachectic or obese)
- signs of liver disease e.g. bruising, spider naevi
- oedema (cirrhosis, pelvic mass, nephrotic sydrome, renal failure)
23
Q
What is involved in the close inspection of the hands and arms in an abdominal/GU examination?
A
CLUBBING - causes are MILC - malabsorption (eg coeliac), IBD (UC and Crohn's), Lymphoma, Cirrhosis ASTERIXIS - coarse flapping tremor - occurs with hepatic encephalopathy RADIAL PULSE BP/TEMP
24
Q
What are you looking for at close inspection of the face?
A
Jaundice
Pull down eyelid to check for anaemia
25
What are you looking at/for during the mouth part of an abdominal/GU examination?
Mouth, Breath Lips, Tongue, Teeth, Gums
- stomatitis, glossitis, candidiasis, ulcers, pigmentation (Peutz-Jeghers Syndrome), telangiectasia, dentition, gingivitis and 'mousy' odour (fetor hepaticus)
26
When inspecting the chest and axillae, what are you looking for?
CHEST - spider naevi, gynaecomastia (in men)
| AXILLAE - loss of axillary body hair
27
What are you looking for in the close inspection of the abdomen?
Movement, distension, scars, herniae, masses, striae, dilated veins 'caput medusae'
28
What are the 5 reasons for distension of the abdomen? (HINT: the 5 F's)
```
Fat
Fluid
Faeces
Flatus
Foetus
```
29
During abdominal palpation you palpate all 9 regions both superficially and deep. What are you palpating for?
Tenderness (including guarding or re-bound tenderness)
Masses
Organomegaly (spleen, liver, kidneys)
Abdominal aorta
30
What are the causes of hepatomegaly?
```
Hepatitis
Alcoholic Liver Disease
RHF
Fatty infiltration
Biliary tract obstruction
Malignancy (metastatic/primary)
Haematological disorders
```
31
How do you test for (i) Murphy's sign (ii) Courvoisier's sign?
(i) Feel for gall bladder tenderness (acute cholecystitis). The pt breathes in whilst you gently palpate RUQ in mid-clavicular line. On liver descent contact with inflamed bladder causes tenderness and sudden arrest of inspiration
(ii) Painless jaundice and a palpable gallbladder. Likely due to extrahepatic obstruction e.g. pancreatic cancer UNLIKELY to be gallstones
32
What are the causes of splenomegaly?
1. Haematological - haemolytic anaemias, leukaemias, polycythaemia rubra vera, lymphoma, myeloproliferative diseases, myelofibrosis
2. Infective - e.g. infectious mononucleosis, infective endocarditis, TB, malaria
3. Rheumatological disorders - RA (Felty's syndrome), SLE
4. Rare causes - sarcoidosis, amyloidosis, glycogen storage diseases
33
What are the causes of renal enlargement?
```
Hydronephrosis
Polycystic kidney disease
Renal cell carinoma
In CHILDREN, nephroblastoma (Wilm's tumour)
Solitary cysts
```
34
What is ascites? What are the causes?
```
An abnormal collection of fluid in the peritoneal cavity
CAUSES:
- hepatic cirrhosis
- intra-abdominal malignancy
- nephrotic syndrome
- cardiac failure
- pancreatitis
- constrictive pericarditis
```
35
What is involved in auscultation using the diaphragm side of your stethoscope?
1. Listen for normal bowel sound (up to 2 mins)
2. Auscultate for abdominal aortic bruits
3. Auscultate renal arteries
36
What 2 things are palpated for when examining the back?
Renal tenderness
| Cervical lymph nodes
37
What are the 3 other areas offered in an abdominal/GU exam?
Offer to examine groin
Offer to examine genitalia
Requests to do digital rectal examination (DRE)
38
What are the indications for a rectal examination?
Rectal bleeding
Prostatic symptoms
Change in bowel habit
Possible spinal cord injury
39
How is a pelvic examination performed? What are the indications to perform?
Bi-manual - one hand palpates per vagina and other per abdomen
INDICATIONS:
- pelvic pain
- abnormal vaginal bleeding or discharge
- if considering a vaginal or uterine prolapse
40
What are the causes of (i) acute (ii) chronic oesophagitis?
(i) Infection in immunocompromised pts (HSV, candida, CMV)
Corrosives
(ii) SPECIFIC - TB, bullous pemphigoid and epidermolysis bullosa, Crohn's disease
NON SPECIFIC - reflux oesophagitis
41
What happens to the body in reflux oesophagitis? What factors predispose GORD?
```
Squamous epithelium damaged
- eosinophils epithelial infiltration
- basal cell hyperplasia
- chronic inflammation
GORD
- 'incompetent' GO junction: alcohol and tobacco, obesity, drugs (caffeine), hiatus hernia, motility disorders
```
42
What can severe reflux oesophagitis lead to?
Ulceration
| - this may lead to healing by fibrosis (stricture or even obstruction)
43
What is Barrett's Oesophagus?
Longstanding reflux
Normally aged 40-60, males more so than females
Lower oesophagus becomes lined by columnar epithelium
Premalignant and so a risk of adenocarcinoma of distal oesophagus 100 times more than general pop.
44
What is acute gastritis caused by?
```
Usually due to chemical injury
- drugs e.g. NSAIDs
- Alcohol
Helicobacter pylori-associated
- usually the transient phase but often becomes chronic
```
45
Describe the details of H pylori-associated Gastritis.
Gram -ve spiral-shaped or curved bacilli
Oral-oral, faecal-oral, environmental spread
It occupies the protected niche beneath mucus where the pH is approx. neutral
Doesn't colonise intestinal type epithelium
Resolves with therapy
46
What therapy is used to resolve H pylori associated gastritis?
Double antibiotics and proton pump inhibitors
47
What are the 2 types of distribution patterns?
1. Diffuse involvement of antrum and body
- atrophy, fibrosis, intestinal metaplasia
- associated with gastric ulcer and gastric cancer
2. Antral but not body involvement
48
How is H pylori associated Gastritis detected?
Faecal bacteria
Urea breath test
Gastric biopsy rapid urease test (CLO test)
49
What is Chemical (reflux) Gastritis? What is it caused by?
Loss of epithelial cells with compensatory hyperplasia of gastric foveolae
- caused by regurgitation of bile and alkaline duodenal secretion
Associated with
- defective pylorus
- motility disorders
50
What is autoimmune chronic gastritis?
It is an autoimmune reaction to gastric parietal cells
- loss of acid secretion
- loss of intrinsic factors (vit B12 deficiency or macrocytic anaemia - pernicious)
51
With autoimmune chronic gastritis, what is there an increased risk of?
Of gastric cancer
52
What are the 4 major sites of peptic ulceration? Please put in descending order.
First part of duodenum
Junction of antral and body mucosa in stomach
Distal oesophagus
Gastro-enterostomy stoma
53
What is a peptic ulcer defined as?
A breach in mucosal lining of alimentary tract as a result of acid and pepsin attack
54
What factors can cause peptic ulceration? (HINT: there's 7 factors)
```
Hyperacidity
H. pylori gastritis
Duodenal reflux
NSAIDs
Smoking
Genetic factors
Zollinger-Ellison syndrome
```
55
What complications can arise as a result of peptic ulceration? (HINT there's 6)
```
Haemorrhage
Penetration of adjacent organs e.g. pancreas
Perforation
Anaemia
Obstruction
Malignancy
```
56
For gastric ulcers, what is the (i) relative incidence (ii) age (iii) social class (iv) blood group (v) acid levels (vi) helicobacter gastritis?
(i) 1
(ii) increases with age
(iii) higher in class V
(iv) A
(v) normal or low
(vi) about 70%
57
Where is the zone of cell proliferation found? How often does it replace villous cells?
In the base of the crypts
| - every 48-96 hrs
58
What causes acute peptic ulcers? (HINT: there's 3 causes)
1. Related to acute gastritis
- full thickness loss of epithelium, rather than just erosion
2. Related to a stress response
- e.g. curling's ulcer following severe burns
3. A result of extreme hyperacidity
- e.g. gastrin secreting tumours
59
Where do chronic peptic ulcers tend to occur? What is their pathogenesis?
```
They tend to occur at mucosal junctions
e.g. antrum -> body
PATHOGENESIS
- hyperacidity
- mucosal defence defects
```
60
What effect does a chronic gastric ulcer have on the body?
```
Normal pH of gastric juice 1-2
Mucosal defences
- mucus-bicarbonate barrier
- surface epithelium (less important
Mucus-bicarbonate barrier
- dissolved by biliary reflux
Surface epithelium
- damaged by NSAIDs
- injured by H. pylori
```
61
WHERE does intestinal secretion occur?
In the epithelial cells lining the crypts of Lieberkuhn
62
What is the pathology of a chronic gastric or duodenal ulcer?
```
They are usually small (less than 20mm)
- sharply 'punched out' with defined edges
Has a defined structure
- granulation tissue at base
- underlying inflammation and fibrosis
- loss of muscularis propria
COMPLICATIONS
= bleed, burst or block. Penetration of adjacent organs (pancreas). Malignant change (rare in gastric and 'never' in duodenal ulcer
```
63
For duodenal ulcers, what is the (i) relative incidence (ii) age (iii) social class (iv) blood group (v) acid levels (vi) helicobacter gastritis?
(i) 3
(ii) increases up to 35 years
(iii) even distribution
(iv) O
(v) high or normal
(vi) 95-100%
64
What causes acute peptic ulcers? (HINT: there's 3 causes)
1. Related to acute gastritis
- full thickness loss of epithelium, rather than just erosion
2. Related to a stress response
- e.g. curling's ulcer following severe burns
3. A result of extreme hyperacidity
- e.g. gastrin secreting tumours
65
Where do chronic peptic ulcers tend to occur? What is their pathogenesis?
```
They tend to occur at mucosal junctions
e.g. antrum -> body
PATHOGENESIS
- hyperacidity
- mucosal defence defects
```
66
Q ON CHRONIC GASTRIC ULCER???????
*********************
67
What 2 things cause the formation of a chronic duodenal ulcer?
1. INCREASED ACID PRODUCTION
- more important than for gastric ulcer
- can be induced by H pylori
2. REDUCED MUCOSAL RESISTANCE
- gastric metaplasia occurs in response to hyperacidity
- then colonised by H. pylori
68
What is the pathology of a chronic gastric or duodenal ulcer?
```
They are usually small (less than 20mm)
- sharply 'punched out' with defined edges
Has a defined structure
- granulation tissue at base
- underlying inflammation and fibrosis
- loss of muscularis propria
COMPLICATIONS
= bleed, burst or block. Penetration of adjacent organs (pancreas). Malignant change (rare in gastric and 'never' in duodenal ulcer
```
69
What are the ways that the GI tract can become damaged? (HINT: there's 5 ways)
1. Local Infammation
2. Ulceration/perforation of mucosal epithelium
3. Disruption of normal microbiota
4. Pharmacological action of bacterial toxins
5. Invasion to blood or lymphatics
70
How does epithelial perforation arise? What can it lead to? What is the current treatment?
The lining of the mucosa wall is perforated due to untreated ulcers
- may result in leaking of food and gastric juices to peritoneal or abdominal cavities
- treatment = surgery
71
What are the various bacterial diarrhoeal pathogens? Name them. (HINT: there's 5/6)
1. Vibrio cholerae
2. Escherichia coli
3. Campylobacter jejuni
4. Salmonella spp.
5. Shigella spp.
6. Listeria monocytogenes
72
Where is the liver located?
Across the upper abdomen, under the diaphragm
| - note it should not be palpable below the costal margin
73
Deep to the peritoneal covering, what is the liver surrounded by? Describe this surrounding.
By Glisson's capsule
- a thin connective tissue layer that sends extensions into the organ, in between the lobules
- it isn't really strong enough to hold sutures that may be required following trauma to the liver. Similarly, the interlobular connective tissue is hardly visible in a normal liver
74
What is the (i) arterial supply (ii) venous drainage of the liver?
(i) (hepatic) portal vein (divides into R and L terminal branches that enter porta hepatis behind arteries) bringing absorbed nutrients from the stomach and SI; and the hepatic artery (from coeliac trunk, divides into R and L terminal branches that enter porta hepatis) which supplies the hepatocytes with oxygen
(ii) hepatic veins emerge from posterior surface of liver and drain into the IVC
75
How is bile drained in the liver?
Via canaliculi that lie between the hepatocytes into bile ductules and eventually into bile ducts
76
What are the 4 functions of the liver?
1. Synthesis and secretion of bile
2. Storage of glucose, glycogen, proteins, vitamins and fats
3. Detoxification of metabolic waste
4. Synthesis of blood clotting & anticoagulant factors
77
What is the visceral surface of the liver covered by? Where is it NOT covered by this?
By peritoneum
- except at the fossa for the gall bladder and at the porta hepatis, which houses the portal triad (portal vein, hepatic artery, hepatic (biliary) ducts
78
What is the new surgical approach to describing sections of the liver? What are these sections related to?
Couinaud liver segments
| - related to branches of the hepatic artery, portal vein and hepatic veins; the segments may be surgically removed
79
What are the liver ligaments?
reflections of peritoneum that surround the bare area
- on the left the coronary ligaments form the left triangular ligament, while on the right, they form the right triangular ligament
80
What is the lymphatic drainage of the liver?
The liver produces about one third to one half of all body lymph
- the lymph vessels leave the liver and enter several lymph nodes in the porta hepatis
- efferent vessels pass to coeliac nodes
- a few vessels pass from the bare area of the lover through the diaphragm to the posterior mediastinal lymph nodes
81
What may a retrograde tumour spread from the coeliac nodes involve?
The hepatic nodes in the porta hepatis and obstruct the bile ducts to cause jaundice
82
What is the nerve supply of the liver?
Sympathetic nerves from the coeliac plexus
| - the anterior vagal trunk gives rise to a large sympathetic hepatic branch, which passes directly to the liver
83
What are the various parts of the gallbladder?
A rounded fundus
A body that is its major part
A neck that narrows towards the cystic duct
- the cystic duct combines with common hepatic duct to form bile duct
84
What is the capacity of the gall bladder? What is the function of the gall bladder?
60ml
| - sole function is to store and concentrate bile, both of which are non-essential
85
What is Hartmann's pouch?
A dilatation at the neck of the gall bladder
86
Do the IVC and hilum of the right kidney lie anterior or posterior to the duodenum?
POSTERIOR
87
What is the spiral valve of Heister? What is its function?
The mucous membrane of the cystic duct is raised to form a spiral fold that's continuous with a similar fold in the neck of the gall bladder
- function is to keep the lumen constantly open
88
What is the (i) arterial supply (ii) venous drainage of the gall bladder?
(i) cystic artery - a branch of right hepatic
| (ii) cystic vein - drains directly to portal vein
89
What is the lymph drainage of the gall bladder?
To a cystic lymph node situated near the neck of gall bladder
- from here lymph passes to hepatic nodes along course of hepatic artery and then to coeliac nodes
90
What is the nerve supply of the gall bladder?
Sympathetic (T5-9) and parasympathetic vagal fibres from the coeliac plexus
91
What does the gall bladder contract in response to?
The hormone CCK, which is produced by the mucous membrane of the duodenum on the arrival of fatty food from the stomach
92
What is Calot's cystohepatic triangle?
Bounded by the edge of the right lobe of the liver, the common hepatic and cystic duct
- used to surgically locate the cystic artery
- NOTE normal variations are very common in the location of the cystic artery
93
Where is referred pain from the gall bladder to?
usually to the epigastrium (T7-9)
- but irritation of adjacent peritoneum may involve the phrenic nerve giving referred pain to the shoulder tip (via supraclavicular nerves)
94
Describe the 4 parts of the course of the common bile duct.
1. In the 1st part it lies in the free margin of the lesser omentum infront of the opening into the lesser sac. It lies in front of right margin of portal vein and to the right of the hepatic artery
2. 2nd part its situated behind the 1st part of duodenum to right of gastroduodenal artery
3. Lies in a groove on posterior surface of head of pancreas, where bile duct joins with main pancreatic duct
4. Combined ducts open into duodenum at major duodenal papilla (ampulla of Vater)
95
What structures lie on the transpyloric plane - L1 level (tips of 9th CC's)? (HINT: there's 9)
1. Fundus of gall bladder
2. Pylorus
3. Neck of pancreas
4. Formation of portal vein
5. Hilum of kidney (right lower than left)
6. Spinal cord ends at L1/2
7. Aorta and origin of SMA
8. IVC
9. 2nd part duodenum
96
What are the functions of the pancreas?
Has both exocrine and endocrine functions
- digestive pro-enzymes secreted via pancreatic duct to 2nd part of duodenum
- insulin and glucagon from islets of Langerhans
97
Where is the pancreas located within the body?
Retroperitoneal
- across epigastrium close to major BVs (=> difficult to access)
- lies in the C shaped curve of the duodenum with a head, neck, body, tail and uncinate process
98
Where does the pancreatic duct begin?
In the tail of the pancreas
| - joins the bile duct at the hepatopancreatic ampulla (of Vater) which opens as the major duodenal papilla
99
What are the 3 components of the Sphincter of Oddi?
1. Around the end of the pancreatic duct (to control flow but prevent bile entering pancreas
2. Around end of bile duct
3. Around the combined ducts
100
What is the arterial blood supply of the pancreas?
1. COELIAC TRUNK
- gives gastroduodenal which goes direct to pancreas but also divides to superior pancreaticoduodenal which gives off anterior and posterior branches
- gives splenic which divides to greater and dorsal pancreatic branches
2. SMA
- gives inferior pancreaticoduodenal which gives anterior and posterior branches
101
What is the venous supply of the pancreas?
same as arteries, all draining to portal vein
| but the portal vein is the mirror image of the gastroduodenal artery
102
What is the (i) lymphatic drainage (ii) nervous supply of the pancreas?
Nerve supply also comes with arteries and is vagus (parasympathetic) plus both T7 to 9 and T10 and 11
103
Describe features of the bacteria Vibrio cholerae.
Gram -ve
Comma shaped rod, flagellated
- characterised by epidemics and pandemics
- human only pathogen
- it flourishes in communities with no clean drinking water/sewage disposal
104
What are the (i) serotypes (ii) vaccines for Vibrio Cholerae?
(i) Based on O antigens
(ii) Parenteral vaccine - low protective efficiency
Oral vaccine - effective and suitable for travellers
105
What is the pathogenesis of Vibrio Cholerae?
Only infective in large doses
- many of the organisms are killed in the stomach
- colonises the small intestine involving flagellar motion, mucinase, attachment to specific receptors
- produces multicomponent toxin
- there's a loss of fluid and electrolytes without damage to enterocytes
106
What is the make up of cholera toxin? What is it responsible for?
Oligomeric complex of 6 protein subunits that leads to an increase in cAMP
- 1 copy of A subunit (enzymatic)
- 5 copies of B subunit (receptor binding)
It is responsible for the characteristic watery cholera diarrhoea
107
What are the consequences of Cholera infection? (HINT: there's 5)
1. Fluid loss of up to 1 lire/hr
2. Electrolyte imbalance leading to dehydration, metabolic acidosis and hypokalaemia
3. Hypovolaemic shock
4. 40-60% mortality
5. less than 1% mortality if given fluid/electrolytes (ORT)
108
What is E.coli?
Gram neg bacillus
- is a member of normal GI microbiota
- some strains possess virulence factors enabling them to cause disease
109
What are the 6 types of E.coli causing GI infections?
1. EPEC (enteropathogenic) - sporadic cases and outbreaks of infection in under 5's
2. ETEC (enterotoxigenic) - 'travellers' diarrhoea
3. VTEC (verocytotoxin-producing) - sporadic cases and outbreaks of gastroenteritis
4. EHEC (enterohaemorrhagic)
5. EIEC (enteroinvasive) - food-borne infection in areas of poor hygiene
6. EAEC (enteroaggregative) - resource-poor countries
110
What 2 enterotoxins does E.coli produce?
LT = heat-labile toxin (v. similar to cholera toxin) increase in cAMP
STa = heat stable toxin
leads to increase in cGMP
111
What is C.jejuni?
Gram -ve helical bacillus with a large animal reservoir
- causes food-associated diarrhoea and is the commonest case in the developed world
- transmission through consumption of raw/undercooked meat, contaminated milk
- mucosal inflammation and fluid secretion
112
What is the histological appearance of C.jejuni?
Inflammation involves the entire mucosa
- villous atrophy
- necrotic debris in crypts
- thickening of BM
113
What is salmonella spp.?
Gram neg bacilli
- causes food associated bacteria
- transmission through consumption of raw/undercooked meat, contaminated eggs and milk
- secondary spread can be human to human
114
What are the 3 important species of salmonella?
S. typhi
S. paratyphi
S. enteritidis
115
What is the pathogenesis of a salmonella infection?
Ingestion of large no. of bacteria
- absorption to epithelial cells in terminal section of SI
- penetration of cells and migration to lamina propria
- multiplication in lymphoid follicles
- inflammatory response mediates release of prostaglandins
- stimulation of cAMP
- release of fluid and electrolytes causing diarrhoea
116
Describe the species S. typhi and S. paratyphi.
Cause enteric fevers - typhoid and parathyphoid
- systemic infections initiated in GI tract
- restricted to humans
- multiply within, and are transported around the body, in macrophages
117
Describe/ explain typhoid fever.
Pt can excrete S. typhi in faeces for several weeks after recovery
- 1-3% become chronic carriers, most common in women and elderly
- is a blanching rash
- a notifiable disease (public health concern)
118
Is there typhoid vaccines? If so, describe them. How effective are they and who are they recommended for?
1. ORAL, live attenuated with a booster after 5 years
2. PARENTERAL, capsular polysaccharide with a booster after 2 years
50-80% effective
- recommended for travellers to endemic areas
119
What is shigella spp. ?
Bacillus that causes shigellosis
| - is a human only species
120
What are the 4 species of shigella?
1. S. dysenteriae = most serious
2. S. flexneri = severe
3. S. boydii = severe
4. S. sonnei = mild
121
What is the pathogenesis of shigella infections?
Attaches to mucosal epithelium of distal ileum and colon
- it causes inflammation and ulceration and is rarely invasive
- produces shiga toxin and is usually self-limitiing
- diarrhoea initially watery, but can contain blood and mucus in later stages
122
What is listeria monocytogenes?
Coccobacillus that causes listeriosis
- food borne pathogen associated with pate, soft cheese and unpasturised milk
- usually presents as meningitis
123
Who are the 3 populations at risk for listeriosis?
!. PREGNANT women
2. IMMUNOSUPPRESSED individuals
3. ELDERY
124
What are the 6 diarrhoeal pathogens?
1. Rotavirus
2. Norovirus
3. Enteric adenovirus
4. Calicivirus
5. Coronavirus
6. Astrovirus
125
What is rotavirus?
11 separate segments of double stranded RNA that infects many mammals
126
What is the pathogenesis of a rotavirus infection?
Incubation period of 1-2 days
- replication of virus in small intestinal epithelial cells at tips of villi, result in villous atrophy
- damage caused to infected cells leaving immature cells with reduced absorptive capacity for sugar, water and electrolytes
- onset of vomiting, diarrhoea for 4-7 dyas
127
Who does rotavirus normally affect?
Children under 2 years old
128
What is the occurence of rotavirus?
seasonal occurence as is more common in colder months
129
What is the transmission of rotavirus?
Faceo-oral
| but may also be faeco-resp
130
What are the vaccines used for rotavirus?
RotaRix RotaTeq
- orally administered (2-3 doses)
- first dose @ 6-10 weeks of age
- live, attenuated virus
131
What is norovirus? How is it transmitted?
'Winter vomiting disease' accounts for most non-bacterial outbreaks worldwide
- past infection in 60% adults and is a human only pathogen
Transmission = faeco-oral, contaminated water/shellfish, fomites
132
Is there a norovirus vaccine?
NO
133
What is enteric adenovirus?
Accounts for 10% of community acquired diarrhoea's in young children
- no seasonal incidence
- asymptomatic infections common
- mild, but prolonged diarrhoea
134
What is antibiotic-associated diarrhoea? How can it arise?
DOESN'T involve ingestion of pathogen/toxin
| - can arise from the disruption of gut microbiota following antibiotic therapy
135
What is C. difficile infection now associated with?
Resistance to vancomycin
136
What does (i) tetracycline (ii) clindamycin allow?
(i) colonisation by staph aureus and candida spp.
| (ii) suppresses gut microbiota and allows c. difficile to multiply
137
What does C. difficile infection produce?
Spores for survival
| - produces an enterotoxin and a cytotoxin
138
What is largely responsible for the increase in cases of C. difficile diarrhoea?
Nosocomial infections
139
What is the structure of Helicobacter pylori?
Gram neg spiral that is flagellated
- microaerophilic
- more than 80% individuals are asymptomatic
140
What diseases can Helicobacter pylori cause? (HINT: there's 4)
Duodenal ulcers
Gastric ulcers
GO reflux disease
Non-ulcer dyspepsia
141
What are the key features of H. pylori? (HINT: there's 5)
1. ACID INHIBITING PROTEIN
- allows for survival in stomach
2. UREASE - neutralisation of acid pH
3. ADHESINS - binding to gastric epithelium
4. CYTOTOXIN - damage to gastric epithelium
5. FLAGELLUM - movement through gastric mucus layer
142
What is the treatment of H. pylori associated Gastritis?
```
1 week triple therapy
EITHER:
PPI plus clarithromycin and amoxycillin
OR
PPI plus clarithromycin and metronidazole
```
143
What is food poisoning?
Syndrome restricted to diseases caused by toxins elaborated by contaminating bacteria in food before it is consumed
144
What are 3 examples of toxins that cause food poisoning?
1. Emetic toxins of Bacillus cereus
2. Enterotoxin of staph aureus
3. Neurotoxin of Clostridium botulinum
145
What is ORT? What does it involve?
Oral Rehydration Therapy
- involves the replacement of fluids and electrolytes lost during diarrheal illness
- 90 to 95% of acute watery diarrhoea can be successfully treated with an ORS
146
What does ORS do?
Increases the resorption of fluids and salts into the intestinal wall
147
What is can be used instead of ORS?
Fruit juices, coconut water and other indigenous solutions can be an alternative if unable to access ORS
148
What is the food associated GI infection Clostridium perfringens?
Usually caused by type A strains from animal guts and soil
149
How does Clostridium perfringens cause a food associated GI infection?
Contamination of raw meat products as the spores survive cooking and germination takes place
150
What does Clostridium perfringens do to the body?
Multiplies in large intestine and produces spores and enterotoxin
- damages intestinal epithelium and causes diarrhoea
151
What is the liver lobule?
Sheets of cells (hepatocytes) radiate outwards from the central vein which forms the central axis of the lobule
152
Where do sinusoids lie? What do they do?
Lie between sheets and carry blood from hepatic artery and portal vein to the central vein
153
What is the functional, vascular distribution of the liver?
Caudate and quadrate lobes are part of left lobe
| - with the fossa for the gall bladder and IVC as the division between the right and left lobes
154
What do infection levels of intestinal protozoa and helminths reflect?
Hygiene/sanitation standards
155
How are intestinal protozoa and helminths acquired? What are the common symptoms?
Through ingestion of contaminated food or water
| - symptoms usually present as acute to chronic diarrhoea and inflammation
156
What are the types of protozoal infections of the (i) small intestine (ii) large intestine?
(i) Giardia lamblia
Cryptosporidium parvum
(ii) Entamoeba histolytica
157
With regards to Giardia Lamblia; (i) what is it a frequent cause of? (ii) What is it detected in? (iii) how is it transmitted? (iv) How is it diagnosed?
(i) Travellers diarrhoea
(ii) Drinking and recreational water
(iii) Person to person
(iv) By microscopy of stool samples
158
What are the 2 stages of a life cycle of G. lamblia? Describe them.
1. TROPHOZOITE
- flagellated and bi-nucleated
- lives in upper part of SI
- adheres to brush border of epithelial cells
2. CYST
- formed when trophozoite forms resistant wall
- passes out in stools
- can survive for several weeks
159
Where is G. lamblia present? What is its pathogenesis?
In duodenum, jejunum and upper ileum
- attaches to mucosa via ventral sucker but does not penetrate the surface
- it causes damage to the mucosa and villous atrophy
- leads to malabsorption of food, especially fats and fat soluble vitamins
- may swim up the bile duct to the gall bladder
160
What are the clinical manifestations of G. lamblia?
Mild infections are asymptomatic
- diarrhoea is usually self-limiting (7 to 10 days)
- chronic diarrhoea is present in immunocompromised pts
- stools are characteristically loose, foul-smelling and fatty
161
How is Cryptosporidium parvum transmitted? How large is an infective dose?
Transmitted through faecally-contaminated drinking water
| Infective dose = as few as 10 oocysts
162
What is the life cycle of C. parvum within the body?
1. Asexual and sexual development within host
2. Ingestion of resistant oocysts
3. Release of infective sporozites in small intestine
4. Invasion of intestinal epithelium
5. Division to form merozoites with re-infect cells
6. After the sexual phase, oocytes are released
163
What is the pathogenesis of C. parvum?
Enters cells of the microvillus border of the SI
- it remains within a vacuole of an epithelial cell but it may multiply to give large no. of progeny, especially in immunocomropmised hosts
164
How does C. parvum clinically manifest itself? What is the danger in certain HIV+ individuals?
Moderate-severe profuse diarrhoea
- up to 25 litres of water faeces a day
- usually self limiting
- In HIV+ with CD4+ T cell counts of less than 100mm3 the diarrhoea is prolonged and may become irreversible and life-threatening
165
With regards to Entamoeba histolytica; (i) where is it common? (ii) how is it transmitted? (iii) what do they do?
(i) in tropical and sub-tropical countries
(ii) Via ingestion of contaminated food or water, also through anal sexual activity
(iii) cysts pass through stomach and exist in SI, giving rise to progeny. they adhere to epithelial cells and cause damage mainly through cytolysis. After mucosal invasion, cysts invade red blood cells giving rise to amoebic colitis. Trophozoite stages live in large intestine and pass out as resistant, infective cysts
166
What is the pathogenesis of E. histolytica?
Adheres to epithelium and acute inflammatory cells
- resists host humoral and cell mediated defence mechanisms
- it produces hydrolytic enzymes, proteinases, collagenase and elastase
- produces protein that lyses neutrophils, the contents of which are toxic to the host
167
How does Entamoeba histolytica clinically manifest itself?
Small localised superficial ulcers leading to mild diarrhoea
| - the entire colonic mucosa may become deeply ulcerated leading to severe amoebic dysentry
168
What complications can arise from E. histolytica?
Intestinal perforation
Trophozoites may spread to the liver, and other organs
Rarely, abscesses spread to the overlying skin
169
What is the difference between bacillary (Shigella) and Amoebic (Entamoeba) dysentry?
```
BACILLARY
- many PMN in stool
- eosinophils absent
- many bacilli in stool
- blood/mucus present in stool
ENTAMOEBA
- few PMN in stool
- eosinophils present
- few amoebae in stool
- blood/mucus present in stool
```
170
What is the treatment of protozoal infections of the GI tract, for (i) G. lamblia (ii) C. parvum (iii) E. histolytica?
(i) FOR G. LAMBLIA
- mepacrine hydrochloride
- metronidazole
- tinidazole
(ii) FOR C. PARVUM
- nitazoxanide
- spiramycin
(iii) FOR E. HISTOLYTICA
- metronidazole
171
What is ORT? When is it used?
Involves the replacement of fluids and electrolytes lost during diarrhoeal illness
- 90-95% of cases of acute watery diarrhoea can be successfully treated with an oral rehydration solution (ORS) - which increases the reabsorption of fluids and salts into the intestinal wall
172
What are 4 ways to prevent protozoal infections of the GI tract?
1. Improved hygiene and water supplies
2. Eating only freshly prepared food served hot
3. Avoiding salads and fruits that can't be peeled
4. Avoiding tap water and ice cubes
173
What are the 3 types of Helminths (worms)?
1. ROUNDWORMS (Nematodes)
2. TAPEWORMS (Cestodes)
3. FLUKES (Trematodes)
174
What are the 6 types of Helminthic infections of the GI tract?
1. Stronglyloides stercoralis - pinworm/threadworn
2. Trichuris trichiura - whipworm
3. Ascaris lumbricoides - giant roundworm
4. Enterobius vermicularis - pinworm/threadworm
5. Ancylostoma duodenale - hookworm
6. Taenia solium - tapeworm
175
What are the most clinically important intestinal worms?
Nematodes
176
How are nematodes transmitted? How does infection by them occur? How are they diagnosed?
Soil-transmitted
Infection occurs by one of the following:
1. Swalloing infective eggs
2. Active skin penetration by larvae and systemic migration through lung to intestine
Diagnosis by eye/sometimes stool microscopy
177
What is Stronglyoides stercoralis?
A pinworm that causes disruption of the small intestinal mucosa causing villous atrophy and marked loss of elasticity of intestinal wall.
178
How does stronglyoides stercoralis clinically manifest itself? (HINT: there's 5 points)
```
Dysentery (which is persistant in immunocompromised pts)
Dehydration
Malabsorption
Anal pruritis (itching)
Association with appendicitis
```
179
What is T. trichiura? How is it acquired?
Whipworm that can live in the gut for greater than 3 years
- acquired through ingesting eggs on vegetables
- 10,000 eggs produced daily (by just one of them)
180
What is A. lumbricoides?
A giant roundworm
- large thick wide worm 20-30cm
- females produce approx 20,000 eggs/day from 65 days after infection and adults live in the gut for 2 years
181
How does Ascaris lumbricoides manifest itself clinically? (HINT: there's 5 points)
```
An allergic reaction in sensitised people
Digestive upsets
Protein/energy malnutrition
Intestinal blockages
Worm may invade mouth, nose etc.
```
182
What is enterobius vermicularis? What symptoms arise as a result?
A threadworm
- small cylindrical nematodes smaller than 1cm
- females migrate to anus at night to lay approx. 10,000 eggs which may develop to infective stage within hours
- cause intense itching - mild catarrhal inflammation and diarrhoea, slight eosinophilia
183
What is Ancyclostoma duodenale? How is it picked up? What does it do? What does it cause?
A hookworm which is often picked up from walking bare foot in infected areas
- attaches to SI, sucks blood and protein, often present in huge numbers
- causes hypochromic anaemia
184
What is taenia solium? How is it acquired? Where does it reside?
Tapeworm
- acquired from ingesting worms or eggs in uncooked pork
- resides in the large intestine and can grow up to 7m long
185
Why do antiprotozoal and antihelminthic agents pose particular problems? (HINT: there's 4 reasons)
Because of:
1. Large variety of species
2. Complexities of their life cycles
3. Differences in their metabolic pathways
4. Drugs active against protozoa are inactive against helminths
186
What percentage of colorectal cancer pts have a familial history of it?
About 25%
| - of those we only know the causative mutations in 5-6% of cases
187
What does (i) FAP (ii) HNPCC stand for?
(i) familial adenomatous polyposis
- autosomal dominant
(ii) hereditary nonpolyposis colon cancer (Lynch syndrome)
188
What are the features of FAP coli?
Autosomal dominant inheritance
- Large number of polyps (100s or more) developing from adolescence onwards
- 90% of patients also have pigmented lesions in retina (CHRPE)
189
What is the gene defect in APC (adenomatous polyposis coli)? How do you test for the gene defect?
Chromosome 5 q21-22
- large gene
- mostly nonsense or frameshift mutations that result in a premature termination of the protein
Test for by protein truncation test or direct sequencing
190
Why do defects in APC predispose to cancer?
If the first hit is a germline mutation, the second somatic mutation is more likely to enable cancer
191
What 2 things does APC do?
Binds to beta catenin and microtubules
| - the regions of binding match to the C terminus of the protein - in FAP pts this c terminus is often missing
192
What is beta catenin? What does it do?
1. Protein that can work as a transcription factor but is normally found in the cytoplasm where APC can bind to it and degrade the beta catenin, keeping its levels low
- its levels can accumulate when not bound to APC and move into the nucleus where (with other transcription factors) it turns on genes to increase cell division.
2. Also present in junctions which links actin cytoskeleton to the adherens junction
193
What do defects in APC also cause?
Chromosome instability (CIN)
194
Why is it the colon that cancer arises due to an APC gene defect?
Colon organised in v unusual way such that cell proliferation occurs at bottom of crypts due to there beings stem cells there constantly dividing
- if cells divide in wrong orientation they stay in crypts instead of moving out and so proliferate again whilst still in the crypts
195
Where else is mutation of APC seen?
In sporadic tumours
| - an APC mutation alone is not sufficient to cause cancer
196
What is Gardner syndrome? Describe it.
A variant of FAP
- rare
- masses of benign tumours
- jaw cysts and sebaceous cysts
- osteomata (bone tumour)
- pigmented lesions of the retina (CHRPE)
197
What are the features of hereditary nonpolyposis coli (Lynch syndrome)?
1-5% of all colon cancers and is autosomal dominant
- high risk of colon tumours
- can be an underlying cause of other tumour types e.g. endometrium, ovarian, small intestine, stomach
- low number of polyps
198
What is the gene defect(s) in HNPCC (Lynch syndrome)? (HINT: there's 3 defects)
1. MSH2 2p21 (40% mutations)
2. MLH1 3p21 (50% mutations)
3. MSH6 2p16 (7-10%)
DONT need to know actual genes but know they all have the same role/function - DNA MISMATCH REPAIR
199
What do mismatch repair gene products do?
They exist to recognise when you have the WRONG pairs of bases paired together
- they attract machinery which can cut out the error and correct it
200
What types of regions are more susceptible to errors? WHY is this the case?
Repetitive regions
| - due to microsatelite instability
201
How do you test for a mutation defect causing HNPCC?
Analysis of someone with stable microsatellites will have traces that loon the same for both normal and tumour cells but a patient with microsatellite instability will have different traced for normal and tumour cells
OR
Do biopsies of tumour and see which proteins are being expressed - use this as a code to figure out if there is any mutations
202
Comparing both FAP and HNPCC, what is the difference in (i) number of polyps (ii) mutation rate (iii) risk of cancer?
(i) FAP = large no. of polyps
HNPCC = low no. polyps
(ii) FAP = high rate
HNPCC = low rate
(iii) FAP = high cancer risk bcoz high no. polyps
HNPCC = high cancer risk despite low no. polyps
203
What is the average age of onset for both FAP and HNPCC?
Around 40
204
What is the life-time risk (penetrance) for (i) FAP (ii) HNPCC?
(i) close to 100%
| (ii) 80% approx
205
What screening is currently done in Scotland for colon cancer?
Those over 50 are screened every 2 years for occult blood - if positive then colonoscopy
If known FAP/HNPCC then biannual colonoscopy from age of 25
Those classes as high to moderate risk have a colonoscopy every 5 years from age 50-75
206
What is obesity? What BMI greater than is a pt then classed as obese?
Excess adiposity
| - greater than or equal to 30 kg/m^2
207
What is the score of BMI and risk of co-morbidities of (i) obesity class I (ii) obesity class II (iii) Obesity class III?
(i) 30.0 - 34.9 = moderate
(ii) 35.0 - 39.9 = severe
(iii) greater than 40 = v. severe
208
What are some of the medical complications (co-morbidities) of obesity?
Stoke, Heart disease, diabetes, pancreatitis, lung disease, liver disease, gallstones, cancer, sleep apnea, arthritis, inflamed veins, gout and psychological problems (depression, body dysmorphia, anxiety)
209
What does 1st degree kinship mean?
Would share 50% of your DNA with that individual
- patent and child
- siblings
210
What protein is over-expressed often in sporadic colon cancer? What does this protein result in?
EGFR
- increase proliferation
- decrease apoptosis\- increases invasion and metastasis
- increases angiogenesis
211
What drug is used to prevent over expression of EGFR?
Cetuximab
- only used where wildtype Kras
- antibody against EGFR and prevents ligand binding to EGFR
212
Diet is another risk factor for colon cancer. What (i) reduces risk (ii) increases risk of colon cancer? WHY is this the case?
(i) high fibre and fish decrease risk
(ii) high intake of red and processed meats increase risk
WHY
- less time in bowel
- bile salts pass through quicker
- presence of anti-oxidants and folate in fruit and veg
- cooking methods
213
How much does obesity increase the risk of colon cancer?
OVERWEIGHT men have a 25% increased risk
| OBESE men have a 50% increased risk
214
What risk does alcohol have on colon cancer?
40% increased risk if more than 5 units are consumed per day
215
What is a preventative measure to colon cancer? WHY?
ASPIRIN
| - inhibits COX-2 which is increased in the early stages of prostaglandin synthesis
216
What is a drawback of using aspirin as a preventative measure to colon cancer?
Increased risk of CV problems as prostaglandins regulate BP
217
What are the functions of COX-2? (HINT: there's 3 functions)
- increased prostaglandin synthesis
- stimulates proliferation and angiogenesis
- inhibits apoptosis
218
Why is BMI a proxy measure?
Contains fat mass and fat free mass (e.g. muscle)
219
How is obesity defined in children?
Tend to use arbitrary reference values
- but these vary worldwide and are difficult to compare
- now the adult cut offs are linked to BMI centiles for children to provide child cut-offs
- international cut offs reformulated to allow BMI to be expressed as a centile or SD score... very minor changes in existing cut-offs
220
What are the centiles for (i) overweight (ii) obese in children?
(i) By sex, passing through a BMI of 25 kg.m^2 @ age 18
| (ii) by sex, passing though BMI of 30kg/m^2 @ age 18
221
What is the link between socioeconomic status and obesity?
Those with a lower income have a greater chance of being overweight/obese
222
Are genes linked to obesity?
YES - but genes MODIFY they are not the sole reason for obesity
223
Explain (i) monogenic (ii) polygenic forms of obesity.
(i) rare (less than 5%), single gene disorders
| (ii) most common with complex interactions between genes and environments
224
What is an example to show the importance of gene - environment interaction in the pathogenesis of obesity?
PIMA INDIANS
- pima in Mexico have traditional methods of farming, cooking, fetching water and are largely unaffected by labour saving devices
- pima in Arizona have a typical american lifestyle and diet
- both have the same/similar genotypes yet those in Arizona on average have higher BMIs
