GI Flashcards
what is slow waves of depolarisation in smooth muscle driven by?
interstitial cells of Cajal (ICCs) = pacemaker cells located largely between the circular and longitudinal muscle layers
- electrically coupled to each other and smooth muscle cells
- some ICCs form a bridge between nerve endings (post-ganglionic) and smooth muscles
where do parasympathetic nerves synapse with enteric nervous system?
S2 - S4
where and what do sympathetic preganglionic nerves synapse with? (gen GI)
thoraco-lumbar region
synapse in prevertebral ganglia:
- celiac
- superior mesenteric
- inferior mesenteric
name the 6 sphincters
- upper oesophageal (UOS)
- LOS
- pyloric
- Ileocaecal valve
- internal anal (smooth muscle)
- external anal (skeletal muscle)
minus sphincter oddi
describe the process of lipid catabolism
triglycerides from dietary and storage fat is broken down by lipases (lipolysis) into fatty acids and glycerols
fatty acids + CoA are oxidised in the cytoplasm to become acyl-CoA to become activated - requires 2 ATP
fatty acids are transferred from acyl-CoA to carnitine - fatty acyl-carnitine crosses membrane from cytoplasm to mitochondrial matrix
become fatty acyle-CoA
beta oxidation produces acetyl-CoA, FADH2, NADH + H+, fatty acyl-CoA
acetyl-CoA then enters TCA
describe ketosis in starvation and diabetes
- oxaloacetate is consumed for gluconeogenesis
- fatty acids are oxidised to provide energy
- acetyl-CoA is converted to ketone bodies
- high levels in blood
- too much for extrahepatic tissue (heart, brain etc)
- ketone bodies are moderate acids - accumulation leads to severe acidosis
- impairs tissue function (particularly CNS)
- smell of acetone on breath
what constricts the oesophagus in the thorax?
- arch of the aorta
- left main bronchus
what are the 4 pairs of extrinsic muscles of the tongue and what are they supplied by?
- palatoglossus **
- styloglossus
- hyoglossus
- genioglossus
all supplied by CN XII (hypoglossal - motor)
EXCEPT PALATOGLOSSUS (CN X- vagus)
what are the opening and closing muscles of the jaw? what are they supplied by?
opening = lateral pterygoid
closing = masseter, temporalis, medial pterygoid
supplied by mandibular division of trigeminal nerve = CN V3
what nerve supplies the general sensation to the superior half of oral cavity?
CN V2
which nerve provides the sensory limb of the gag reflex?
glossopharyngeal (CN IX)
what is the upper oesophageal sphincter called?
cricopharyngeus
what is included in the foregut?
oesophagus to mid-duodenum
liver, gall bladder, spleen and half of pancreas
what is included in the hindgut?
distal third of transverse colon to proximal half of anal canal
where do sympathetic nerves for the abdominal wall leave the spinal cord?
between T5 + L2
** except adrenal gland - leaves at T10 - L1 and synapses DIRECTLY onto cells
what 4 antibiotics should be avoided for C. Diff prevention?
cephalosporins
clindamycin
ciprofloxacin
co-amoxiclav
which bacteria associated with gastroenteritis can cause bloody diarrhoea?
E. coli 0157
campylobacter
salmonella
c. diff - sometimes bloody
shigella
how is variceal bleeding treated?
terlipressin (vasoconstrictor) - contraindicated in ischaemic heart disease
how are haustra formed?
tonic contraction of the teniae coli
what are the teniae coli?
3 longitudinal bands of thickened smooth muscle - runs from caecum to distal end of sigmoid colon
where is most often the maximum point of tenderness in appendicitis?
McBurney’s point - 1/3 of the way between ASIS (boney hip bit) to umbilicus
–> where appendiceal orifice is (usually)
what is meant by sigmoid volvulus?
when the sigmoid colon twists round itself
v motile due to long mesentery (sigmoid mesocolon)
where does the inferior mesenteric artery branch from the abdominal aorta?
L3 ish
what are the branches of the SMA? (superior to inferior)
inferior pancreaticoduodenal middle colic right colic ileocolic appendicular jejunal + ileal branches
what are the branches of the IMA?
left colic
sigmoid colic
superior rectal
what is the anastomosis between SMA + IMA called?what is the benefit of this?
marginal artery of Drummond
collateral prevent ischaemia/infarction
where do the veins of foregut, midgut and hindgut drain to?
hindgut -> IMV -> splenic
midgut -> SMV -> hepatic
foregut -> splenic -> hepatic
fore, mid, hind -> hepatic -> liver for first metabolism
clean blood -> IVC (retroperitoneal) -> RA
where are the 3 major portal systemic anastomoses?
distal end of oesophagus
skin around umbilicus
rectal / anal canal
what happens to the portal systemic anastomoses during portal hypertension?
blood is diverted through collateral veins back to systemic venous system
anastomoses now have large flow (usually small) - dilate, become varicose
describe the process of swallowing? what cranial nerves are involved?
- Close lips to prevent drooling (orbicularis oris + CN VII)
- tongue (CN XII) pushes bolus posteriorly towards oropharynx
- Sequentially contract pharyngeal constrictor muscle (CN X) to push bolus inferiorly towards oesophagus
- At same time inner longitudinal layer of pharyngeal muscles (CN IX + X) contracts to raise larynx, shortening pharynx and closing off laryngeal inlet to prevent aspiration
- Bolus reaches oesophagus
where does the celiac trunk arise?
T12
what does the celiac trunk bifurcate into?
splenic artery
hepatic artery
left gastric artery
what ribs protect the liver and spleen respectively?
liver 7-11
spleen 9-11
name the 4 lobes of the liver
right
left
caudate (top at back)
quadrate (bottom at back)
what is the lowest part of the peritoneal cavity when the patient is supine?
hepatorenal recess
what are the 3 main ligaments of the liver and what do they connect to?
coronary ligaments (top) - attach to diaphragm
falciform ligament (between left/right) - attach to anterior abdominal wall
ligamentum teres - remnant of embryological umbilical vein
what does the gallbladder do?
stores + concentrates bile
foregut organ
removal = cholecystectomy
where does the bile duct drain?
joins with main pancreatic duct to form ampulla of Vater
–> both then drain into the 2nd part of the duodenum through major duodenal papilla
smooth muscle sphincters:
- bile duct sphincter
- pancreatic duct sphincter
- sphincter of Oddi (from ampulla of Vater)
what investigation is used to study the biliary tree and pancreas?
endoscopic retrograde cholangiopancreatography (ERCP)
–> pics of dye filled biliary tree
what autonomic nerves supply the pancreas?
vagus - parasympathetic
abdominopelvic splanchic - sympathetic
forms plexus around celiac trunk + SMA
what are lacteals?
specialised lymphatic vessels of small intestine
bile helps absorb into intestinal cells via lacteal
what is indicated is AST/ALT is more elevated than ALP?
hepatocellular injury
what is indicated is ALP is more elevated than AST/ALT?
obstruction
what is indicated by an acute rise in GGT?
alcohol consumption
why do patients with an obstructed biliary tree present with pale stools?
due to reduced levels of conjugated bilirubin entering GI tract which would colour the stool
conjugated bilirubin turns into bile and enters the small intestine (to be eliminated by stool)
what is the difference between conjugated and unconjugated bilirubin?
unconjugated = not water soluble so not excreted by urine - normal colour
conjugated = water soluble so can be excreted in urine, dark (coke) coloured wee
unconjugated bilirubin is bound to serum albumin and transferred to the liver where it is conjugated (making it water-soluble) to glucuronate by glucuronyl transferase. Conjugated bilirubin is excreted into bile.
what does shiga toxin do?
binds to receptors found on renal cells, RBC etc
inhibits protein synthesis –> causes cell death
what type of cells line the normal sigmoid mucosa?
simple columnar
what artery supplies the transverse colon?
middle colic artery
what is charcot’s triad?
acute cholangitis
fever
jaundice
RUQ pain
what 3 muscles make up the levator ani muscles? what type of muscle are they?
lateral to medial
iliococcygeus
pubococcygeus
puborectalis
skeletal muscle - under voluntary control
at what point does the sigmoid colon become the rectum?
anterior to S3
where does the rectum become the anal canal?
anterior to tip of coccyx
the rectum, anal canal and anus are all located in the perineum
true or false
false !
rectum = pelvis
anal canal + anus = perineum
what nerves supply the levator ani muscles?
superior = nerve to levator ani - S4
inferior = pudendal - S2, S3, S4
what function does the puborectalis muscle play in faecal continence?
contraction of this muscle decreases the anorectal angle - acting like a sphincter
when rectal ampulla is relaxed + filled with faeces, voluntary contraction of this muscle with help maintain continence
- part of levator ani muscle
- marks transition point between rectum + anal canal
characteristics + nerve supply of internal anal sphincter
smooth muscle (involuntary) superior 2/3rd of anal canal
contraction stimulated - sympathetic nerves
contraction INHIBITED - parasympathetic
contracted ALL the time - relaxes reflexive in response to distension of rectal ampulla
characteristics + nerve supply of external anal sphincter
skeletal muscle (voluntary) inferior 2/3rds of anal canal
contraction stimulated - pudendal nerve
–> voluntarily contracted along with puborectalis in response to distension in rectal ampulla + internal sphincter relaxation
where do the sympathetic fibres responsible for contraction of anal sphincter and inhibiting peristalsis come from?
T12-L2
what is the pudendal nerve formed from? what does it supply?
formed from S2, 3 + 4
supplies external anal sphincter
branches to supply structures of perineum
what does the pectinate line divide?
marks the junction between the part of the embryo which formed the
GI tract - endoderm
+
skin - ectoderm
arterial, venous, lymphatic + nerve supply differ above + below line
what are the fossae called that lie each side of the anal canal?
ischioanal fossae
–> filled with fat + loose connective tissue
can communicate with each other
what are haemorrhoids (piles)?
prolapses of rectal venous plexuses - raised pressure
can occur in chronic constipation
which organs are intraperitoneal?
stomach 1st part of duodenum jejunum ileum transverse colon sigmoid colon
which organs are retroperitoneal?
2nd, 3rd, 4th parts of duodenum ascending colon descending colon pancreas kidneys ureters aorta IVC
what are antimicrobials? what is antimicrobial resistance (AMR)?
all agents that act against microorganisms - bacteria, fungi, viruses, protozoa
AMR = when microbes are resistant to one or more antimicrobial agents to treat infection / as an antiseptic
–> multi-drug resistance (MDR)
what are antibiotics?
drugs that kill or inhibits growth of microorganisms
list some mechanisms of antimicrobial resistance
inactivation - add phosphate group on the antibiotic which will reduce its ability to bind to bacterial ribosomes
pumping out - increasing active efflux of drugs
modification - modifying drug target
impermeability - modifying cell wall protein (decreased influx)
how can bacteria develop antimicrobial resistance?
chromosomal mutations - vertical transmission (innate)
most common = resistent genes/clusters via conjugation, transposition, transformation - horizontal (acquired)
why is antimicrobial resistance increasing?
increasing resistance in community
complacency regarding ABs
increased use of broad spectrum ABs
–> antimicrobial stewardship to fix this
common presentations of gonorrhoea + chlamydia
GONORRHOEA low abdo pain diarrhoea rectal bleeding anal discharge tenesmus urethral/vaginal discharge
CHLAMYDIA
mostly asymptomatic, milder than gonorrhoea - similar symptoms
discomfort itch
anal discharge
clinical feautes of HSV
pain
ulcers
painful defecation
bleeding, mucus
what STI are anal warts a common presentation in?
HPV
coffee bean sign on AXR
sigmoid volvulus
what is Choledocholithiasis?
presence of gallstones in bile duct
what are the borders of hesselbach’s triangle and what type of hernia is it associated with?
medial = rectus abdominus muscle
superior / lateral = inferior epigastic artery
inferiorly = inguinal ligament
direct inguinal hernias (reducible)
advantages of buccal/sublingual drug administration
buccal/sublingual = under tongue - GTN
by-passes portal system + avoids first pass metabolism
avoids gastric acid
most common liver tumour
haemangioma - benign
well demarcated circular on USS
most likely liver tumour in younger patients
adenoma
focal nodular hyperplasia - central scar
which nerve supplies the anterior 2/3rd of taste on the tongue?
CN V3 - mandibular branch of trigeminal nerve
which nerve supplies the posterior 1/3rd of taste on the tongue?
CN VII - facial nerve (chorda tympani branch)
what level is the caval hiatus?
T8 - contains IVC, phrenic nerve
where does the oesophagus + aorta pass through the diaphragm respectively?
oesophageal hiatus = T10
aortic hiatus = T12
where does the coeliac, SMA + IMA branch from the abdominal aorta respectively?
coeliac axis - T12
SMA - L1
IMA - L3
autoimmune liver disease investigations + management
young/middle aged women
diagnosis = liver biopsy - piecemeal necrosis
+ anti-smooth muscle antibody (ASMA)
Mx = steroids (remission) + azathioprine
alpha 1 anti-trypsin deficiency
liver failure in YOUNG
lung emphysema
what can the presence of antinuclear antibodies (ANA) indicate?
autoimmune disease
what are pseudocysts?
collections of pancreatic juice
–> can develop 4 weeks after acute pancreatitis
what is a whipple procedure? when would it be done?
surgical operation to remove tumour of head of the pancreas that has NOT spread
removal of - head of pancreas pylorus - can be preserved (modified Whipple = PPPD) duodenum gallbladder bile duct relevant lymph nodes
courvoisiers law
palpable gall bladder + jaundice
–> cholangiocarcinoma / pancreatic cancer
what class of drugs can cause gynaecomastia?
H2 receptor antagonists –> ranitidine
can cause drug-induced gynaecomastia
what is the most common cause of liver failure in the UK (massively raised ALT) ?
paracetamol overdose
flapping hands tremor
hepatic encephalopathy - increased ammonia
what type of bacteria is C. Diff?
gram positive bacillus
pathophysio of chronic pancreatitis
destruction of the islets of Langerhans cells
Excessive alcohol intake is the most common risk factor for the development of chronic pancreatitis, with this inflammation of the pancreas resulting in the destruction of the islets of Langerhans cells.
what pathway is responsible for ketone development in states of insulin depletion?
lipolysis (fat breakdown)
-> develops ketone bodies which can be measured in urine plasma clinically in diabetic ketoacidosis / insulin deficiency
this pathway is regulated by insulin
different types of vomit in intestinal obstruction
semi-digested food eaten a day or 2 ago (no bile) = gastric outlet obstruction
copious bile-stained fluid = upper small bowel obstruction
thicker brown, foul smelling (faeculant) = most distal
