W1 GI (except Biochem and embryology) Flashcards
accessory organs of GI system
- salivary glands
- pancreas
- hepatobiliary system (liver and gall bladder)
where does carbohydrate digestion begin
mouth- salivary amylase
type of muscle in oesophagus
upper 2/3= skeletal muscle
lower 1/3= smooth muscle
layers of GI tract
mucosa
submucosa
muscularis externa
serosa/adventitia
describe contents of mucosa
- mucosa epithelium with exocrine and endocrine glands
- lamina propria-capillaries, enteric neurons, lymphoid tissue
- muscularis mucosa
describe submucosa
connective tissue
larger blood and lymph vessels
submucosal plexus
describe muscularis externa
circular and longitudinal smooth muscle
myenteric plexus
describe serosa
connective tissue
additional layer to GI tract in stomach
oblique muscle
internal to circular muscle
where is skeletal muscle found in the GI tract
mouth, pharynx, upper oesophagus, external anal sphincter
what is aucherbach’s plexus
Function
myenteric plexus
motility and sphincters
what is meissner’s plexus
submucosal plexus
modulates epithelia and blood vessels
Describe how slow wave activity can occur in smooth muscle cells and nerves involved
gap junctions L type Ca2+ interstitial cells of cajal enteric nerves, autonomic nerve, hormones slow waves
Describe location of interstitial cells of cajal
Between circular and longitudinal muscle
gap junctions between themselves and smooth muscle
bridge nerve endings and smooth muscle
Difference between slow wave activity in intestine and stomach
depolarisation must reach a threshold in the intestine, but not in the stomach
how does slow wave activity vary along GI tract
increases from stomach to SI
decreases from SI to LI
Parasympathetic innervation of GI tract
Vagal nerves from medulla-oesophagus to ascending colon
Pelvic nerves from s2-s4- ascending colon to anus
Sympathetic innervation of GI tract
synapses at prevertebral ganglia (celiac, superior and inferior mesenteric)
thoracolumbar region
Location of ENS
entirely in gut wall
Example of local reflex and describe them
peristalsis
intrinsic
sensory neuron stimulated and will cause effector neuron to bring about effect via interneuron
up to 10cm, oral to aboral
short reflex
intestino intestinal inhibitory reflex
autonomic nervous system
relaxation of parts of tract
long reflex
Gasto-ileal reflex
vago-vagal reflex
CNS
communication between distant parts of GI tract
peristalsis
wave of relaxation then contraction in aboral direction
which substances cause contraction and relaxation in peristalsis
contraction-substance P and ACh
relaxation- VIP and NO
segmentation
mixing and churning
contraction of circular muscle
what is haustration
segmentation in LI
when does segmentation occur in SI
fed state
colonic mass movement
sweep of contraction forcing faeces to rectum in colon
2/3 per day
migrating motor complex
powerful sweep form stomach to terminal ileum in SI
Name the sphincters in GI tract and muscle type
UOS (skeletal) LOS (smooth) pyloric sphincter (smooth) ileocecal sphincter (smooth) IAS (smooth) EAS (skeletal)
+sphincter of Oddi (pancreas and SI)
epithelium of oral cavity, oropharynx and laryngopharynx
stratified squamous epithelium
only keratinised around teeth and hard palate
Describe the surface of the tongue
anterior 2/3: stratified squamous epithelium, papillae
posterior 1/3: stratified squamous epithelium which lacks papillae, except for circumvallate papillae, has lymphoid tissue which aggregates at submucosa
Describe the surface of the tongue
anterior 2/3: stratified squamous epithelium, papillae
posterior 1/3: smooth stratified squamous epithelium which lacks papillae, except for circumvallate papillae, has lymphoid tissue which aggregates at submucosa
nerve supply of tongue
anterior 2/3: facial nerve
posterior 1/3: glossopharyngeal
Name 4 types of papillae on tongue and which has no taste buds?
Fungiform
circumvallate (V line)
foliate
filiform (no taste buds, keratin)
name the tonsils
palatine tonsils
pharyngeal tonsils
lingual tonsils
tubal tonsils
Barrets Oesophagus
gastric reflux damages squamous epithelium of oesophagus, metaplasia to SI epithelium
pre-cancerous
Epithelium of cardia
simple columnar
Describe gastric pits in stomach
Gastric pit- 1 to 7 gastric glands- mucous cells
isthmus has mostly parietal cells
neck-mucous and parietal cells
fundus- chief , parietal and endocrine cells
What do parietal cells produce
HCl
what do chief cells produce
pepsinogen
gastric pits in cardia, fundus and pylorus
cardia- deep, coiled, less numerous
body- shallow, straight
pylorus- deep, coiled, more numerous
Location and function of Brunners glands
Duodenum submucosa
secrete alkaline fluid
Tallest and smallest villi in SI
tall-jujunum
small- ilium
Describe lymphoid follicles in SI
infrequent in jejunum
Peyer’s patches in ilium submucosa
location and function of paneth cells
crypts of Lieberkühn
anti-bacterial
regulate gut flora
secrete lysosomes and defensins
enteroendocrine cell function
secrete hormones
eg CCK, VIP
Arrangement of Longitudinal muscle in the LI
split into 3 strands
teniae coli
epithelium of anal canal
non-keratinised stratified squamous epithelium
Exact location of myenteric plexus
Ganglia between circular and longitudinal muscle
portal triad
hepatic artery (from left heart)
hepatic portal vein (from gut)
bile duct
also lymphatic tissue and nerves
number of hepatic veins and where they go
3
go to IVC
Describe the liver capsule
layer of mesothelial cells (simple squamous)
then connective tissue capsule
Structure of liver lobule
hexagonal
centrolobular vein
portal triad at each corner
what cells line bile ducts
cholangiocytes
how to differentiate between contents of portal triad
start with bile duct- lined with simple cuboidal epithelium
HA more rounded than HPV
HPV is usually the largest
thin walled and no blood cells- LV
Structure of hepatocytes and sinusoids
hepatocytes- sheets/plates
sinusoids- spaces, blood channels
direction of blood flow in hepatocyte
PT to CV
name of space between hepatocytes and sinusoids
Space of Disse or perisinusoidal space
microvilli of hepatocytes project into this space
how are sinusoids adapted to their function
Fenestrated, so plasma can access hepatocytes but blood cells can’t get out
what does the space of disse contain which supports the liver
Reticular fibres (Type III collagen) and type I collagen
- Where are hepatic stellate cells found?
- Other name for hepatic stellate cells
- Function of hepatic stellate cells
- What can Hepatic stellate cells do in disease
- space of disse
- Ito cells
- modified fibroblasts which make connective tissue, store Vitamin A in fat droplets in their cytoplasm
- Can transform into myofibroblasts and produce scar tissue in liver (cirrhosis)
what are kupffer cells
liver macrophages
also remove old RBC
direction and mechanism of movement of bile in lobules
hepatocytes to bile ducts in PT via bile canaliculi (tight junctions)
Describe exocrine division of pancreas
how this enters duodenum
acinar cells
duct cells
enzymes- protease, lipase, nuclease, amylase
enter duodenum via pancreatic duct
Describe endocrine pancreas
secretes hormones- insulin and glucagon
Islets of langerhaun (1-2%)
in what form are enzymes released form exocrine pancreas
describe activation of trypsin
inactive proenzymes
when they reach pancreas, they are activated by enteropeptidase to covert trypsinogen into active trypsin
Compare apical and basal parts of acinar pancreatic cells
apical- eosinophilic due to zymogen
basal- basophilic due to RER
what is unique about pancreatic acinar cells
ducts extend into acinus
Function of gall bladder
Stores and modifies bile
layers of gall bladder
simple columnar epithelium lamina propria loose connective tissue, blood and lymphatic vessels smooth muscle adventitia
Removal of gall bladder
cholecystectomy
How does gall bladder get bile from liver
actively pumping Na+ and Cl-from bile into spaces between epithelial cells, water follows,
what causes gall bladder to contract
vagal control
hormones- CCK
What is cholecystitis
potential cause
Inflammation of the gall bladder
could be caused by galls tones, leading to thickening of smooth muscle of the gall bladder
How can we view GI tract
endoscope
what is jaundice
yellowing of the sclera and the skin due to build up of bilirubin in the body
What is bilirubin
breakdown products of RBC haemoglobin (spleen) and forms part of bile
Location of lesser and greater omentum
in which omentum in the portal triad
Great omentum connects the stomach and the transverse colon
lesser omentum connects the stomach and duodenum to the liver
PT in the lesser omentum
- location of spleen and what ribs it is protected by
- function of the spleen
- difference between the function of the spleen in adults and children
left hypochondrium, protected by ribs 9-11
produces lymphocytes, mini blood transfusion, immune protection and response
adults- breaks down RBC
foetus- makes RBC
What ribs protect the liver
ribs 7-11
Describe the two ways of dividing the liver
four anatomical segments:
right lobe, left lobe, caudate and quadrate (on right lobe)
8 Functional segments - each have their own hepatic artery, HPV, bile duct and hepatic vein. (makes hepatic segmentectomy possible)
Ligaments of the liver
Coronary ligament on the superior surface attaches liver to the diaphragm
Falciform ligament which divides right and left lobe
Ligamentum teres - embryological remnant of umbilical vein
Describe venous drainage from the liver
3 hepatic veins drain into IVC
Consequence of no valves on IVC and hepatic veins
hepatomegaly- rise in central venous pressure is directly transmitted to the liver
what are the two clinically important recesses on the peritoneal cavity and clinical name and importance
hepatorenal recess (morrisions pouch) subphrenic recess
Peritonitis can cause pus in morrisons pouch-abscess formation and excess fluid will collect in hepatorenal cavity when lying down
tube that comes off gall bladder
Cystic duct
bile flows in and out of GB
Blood supply of GB
cystic artery
usually from right hepatic artery
Presentation of gall bladder pain
foregut organ so will begin in epigastric region (T6-9)
can also occur in hypochondrial region
may refer to right shoulder - anterior diaphragm is irritated and its somatic sensory innervation comes from C3, 4, 5 which also carry somatic sensory to the shoulder so pain is referred to the shoulder
Describe/draw the biliary tree
the right and left hepatic duct join to from the common hepatic duct. the hepatic duct and cystic duct join to from the biliary duct, which drains into the duodenum
where does celiac trunk branch from
celiac trunk is the 1st branch of three branches of abdominal aorta
at what vertebral level does the cephalic trunk arise at
T12
Branches of celiac trunk
splenic artery
hepatic artery
left gastric artery
Blood supply of the stomach
right and left gastric arteries to the lesser curvature
right and left gasto-omental arteries to greater curvature
both anastomose together
where do the left and right gastric arteries arise from
left- celiac trunk
right-
Blood supply of the liver
Hepatic artery
Branches into right and left hepatic artery
Function of hepatic portal vein
Drains blood from the foregut, midgut, hindgut to the liver
Function of splenic vein
Drains blood from foregut
function of inferior mesenteric vein
drains hindgut
function of superior mesenteric
drains midgut
what is colicky pain
pain that comes and goes, due to obstruction
Describe two ways in which abdomen can be divided
4 quadrants- RUQ, LUQ, LLQ, RLQ
9- Epigastric, R and L hypochondrium,
umbilical, R and L lumbar
Public, R and L inguinal
what is a) intraperitoneal b) retroperitoneal c) within a mesentery
a - completely surrounded in peritoneum eg liver
b - only on anterior surface eg kidneys, pancreas
c - double layer of peritoneum, hanging from posterior abdominal wall-intestine
how do the greater and lesser omentum communicate with eachother
through the omental foramen
pouch in males
rectovesical pouch
pouches in females
vesicouterine pouch rectouterine pouch (pouch of Douglas)
Treatment of ascites
Paracentesis or abdominocentesis
needle is inserted lateral to the rectus sheath to avoid inferior epigastric artery which arises from the external iliac artery
Contents of foregut, midgut and hindgut and how origins come about
Embryological origins-
foregut: oesophagus to mid duodenum and liver, GB and 1/2 of the pancreas
midgut: second half of duodenum to proximal 2/3rds of
the transverse colon and other 1/2 of pancreas
hindgut: distal 1/3rds of transverse colon to proximal 1/2 of the anal canal
where are the thoracoabdominal nerves
7th-11th intercoastal spaces
Where is the subcostal nerve
12th intercostal space
how do sympathetic nerves get to abdominal organs
exit spinal cord at T5-L2
leave spinal cord via abdominopelvic splanchnic nerves and synapse at the prevertebral ganglia anterior to the aorta
hitch a ride with the arteries to smooth muscles and glands
Sympathetic nerves of adrenal gland
T10-L1 and enter abdominopelvic splanchnic nerves but do not synapse with pre vertebral ganglia, synapse directly onto cells
Parasympathetic innervation of abdominal organs
vagus nerve travels on oesophagus, then in periarterial plexus around the abdominal aorta and synapse at organs, supplying up to the distal end of transverse colon
pelvic nerves (S2,3,4) provide descending colon to the anus
Visceral afferent of the foregut
T6-9
Visceral afferents of midgut
T8-12
Visceral afferents of the hindgut
T10-L2
Where does pain originating from foregut tend to be felt
epigastric
Where does pain originating from midgut tend to be felt
umbilical
Where does pain originating from hindgut tend to be felt
pubic
why may pain from liver be felt in upper shoulder
Liver is on underside of diaphragm irritating it, diaphragm and upper shoulder is innervated with C3, C4, C5
effect of CCK on gall bladder
contraction
gold standard investigation for suspected biliary dyskinesia.
CCK-HIDA
pH of stomach
2
what do Parietal cells secrete
HCl, Ca, Na, Mg and intrinsic factor
what do chief cells secrete
pepsinogen
what do Surface mucosal cells secrete
mucus and bicarbonate
where are bile salts absorbed
terminal ileum
how much bile enters duo per day
500ml-1.5L
