GI system Flashcards
what is the GI system made up of
oral cavity
pharynx
oesophagus
stomach
small interstine
large interstine
rectum
anal canal
what are the GI systems accessory organs
teeth
tongue
salivary glands
pancreas
liver
biliary tree and gallbladder
what germ layers make up the GI tract
endodermal and mesodermal primary germ layers
derives from the primitive gut tube
what is the epithelial lining derived from
embryonic endoderm
what does the epithelial lining give rise to
specific secretory cells (the parenchyma) of the glands
what is derived from the splanchnic mesoderm
connective tissue for glands (stroma)
cognitive tissue, smooth muscle and peritoneal covering of the wall of the tube
what are the divisions of the embryological GI tract
foregut
midgut
hindgut
what does the foregut include
pharyngeal gut tube (pharynx)
where is the foregut
extends from the mouth to the point where the hepatopancreatic ampulla enters the duodenum
where is the midgut
extends from the point where the hepatopancreatic ampulla enters the duodenum to the junction between the proximal 2/3 and the distal 1/3 of the transverse colon
where is the hindgut
extends from the junction between the proximal 2/3 and the distal 1/3 of the transverse colon to the anus
what is the gut tube vascularised by
branches form the abdominal aorta
how is blood supplied to the foregut
by the coeliac trunk
how is blood supplied to the midgut
by the superior mesenteric artery
how is blood supplied to the hindgut
by the inferior mesenteric artery
what is ischaemic colitis
insufficient blood supply to splenic flexure of the colon
where is the he splenic flexure of the colon
the bend where the transverse colon and descending colon meet in the upper left part of your abdomen.
what is the role of the hepatic veins
Drain venous blood from the major parts of the GI tract through the hepatic portal venous system into the vena cava
what is the role of the hepatic portal vein
Receives venous drainage from the abdominal part of the GI tract, pancreas spleen and gallbladder via its tributaries (gastric, splenic and mesenteric veins to the liver
what are the derivative of the foregut
pharynx
larynx
oesophagus
stomach
duodenum (proximal half)
liver
biliary tree and gall bladder
pancreas
what are the derivates of the midgut
duodenum (distal half)
jejunum
ileum
cecum
ascending colon
transverse colon
what are the derivates of the hindgut
transverse colon
descending colon
sigmoid colon
rectum
anal canal
how is a normal physiological umbilical hernia formed
the intestinal loops protrude through the umbilical region of the developing fetus to form Physiological umbilical hernia
where do intestinal loops normally go
normally return back into the abdominal cavity through a number of rotation and fixations of the gut tube
what is omphalocele
failure of the intestinal loops to return back into the abdominal cavity after the physiological herniation
what is eckels (illegal) diverticulum
embryological remnant of the vitelline duct of the yolk sac attached close to the ileocecal junction
what is diverticula of the colon
small out pocketing pouches from the wall of the colon
what can diverticula of the colon lead to
diverticular disease or diverticulitis
what and where is the peritoneum
A smooth thin serous membrane which lines the walls of the abdominal cavity and covers some of the visceral
balloon empty in visceral cavity
what are the 2 layers of the peritoneum
parietal layer
visceral layer
parietal layer of the peritoneum
lines the inner surface of walls of the abdominal cavity
visceral layer
invests or covers most of the abdominal viscera
peritoneal cavity
the potential space between the parietal and visceral peritoneal layers
intraperitoneal
when organs are completely covered by the visceral peritoneum (small intestine)
retroperitoneal
when organs lie behind the peritoneum and are partially covered on their anterior surface only (kidney or pancreas)
what connects one abdominal viscera to another or abdominal wall
fold of peritoneum
mesenteries
mesenteries
double layers of peritoneum
enclose organs and connect them to either the anterior or posterior walls of the abdomen
how do you name mesenteries
named according to the organs / structures they connect
greater omentum
type of mesenteries
a draping double peritoneal fold that connects the stomach to the transverse colon
policeman of the abdominal cavity
lesser omentum
type of mesentery
connects stomach and bit of duodenum to the liver
falciform
type of mesentery
connects the liver to the anterior abdominal wall
what are they 2 ligaments of the lesser omentum
- hepatogastric ligament = connects liver to stomach
- hepatodudenal ligament = connects liver to duodenum
2 peritoneal cavities (sacs)
- omental bursa (lesser sac)
- greater sac
omental bursa / lesser sac
- Omental bursa (lesser sac)
- Perioneal cavity in fold of lesser omentum
- Behind the stomach
- Water bed of which the stomach is lying
- Stomach bed
- Lying anterior to the pancreas and stomach is lying on it
- Part of the bed of the stomach
greater sac
what is remaining of the periotoneal cavity - green and brown = supra colic compartment (green) and infraolic compartment (brown
3 parts of greater sac
supra colic compartment and infracolic compartment
how are the lesser and greater sac connected
through omental (epiploic) foramen of Winslow
anterior boundary of omental (episodic) foramen of Winslow
free edge of lesser omentum (hepatodudenal ligament)
within which are
* bile duct
* hepatic artery
* portal vein
posterior boundary of omental (episodic) foramen of Winslow
inferior vena cave
inferior boundary of omental (episodic) foramen of Winslow
first part of duodenum
superior boundary of omental (episodic) foramen of Winslow
caudate lobe of liver
regions of Gi tract in abdominal cavity
right hypochondrium
left hypochondirum
right flank
left flank
right groin
left groin
epigastric
umbilical
pubic
planes of abdominal cavity
intertubcular plane
midclavicular plane
subcostal plane
parts of the stomach
duodenum
pylorus
pyloric canal
pyloric antrum
angular incisure
body
cardia
oesophagus
fundus
cardial notch
what supplies blood to the stomach
celiac trunk
who is the pylorus identified in surgery
pre pyloric vein of mayo which ascends over the pylorus is used to identify the pylorus in surgery
anatomical lobes of the liver
right and left lobes
quadrate and caudate lobes (part of right lobe)
what are the right and left lobes separated by
Falciform ligament
what are the quadrate and caudate lobes seperated by
sagittal fissure and transverse porta hepatis
why is the caudate lobe regarded as the third liver or lobe
as it receives vessels from both branches of the hepatic artery and bile duct and drain directly into the inferior vena cava
how many segments is the liver divided into
8 segments based on the distributions of the portal triad and hepatic vein
Livers dual oxygenated blood supply
- hepatic portal vein (75% of blood -40% more oxygen than systemic veins)
nourishes the liver parenchyma
carriers all of the nutrients absorbed by the GI tract - hepatic artery - 25% of blood to the liver
lymphatic drainage of the liver
- liver is a major lymph producing organ of the body
- 1/4 to 1/2 of the lymph entering the thoracic duct comes form the liver
- the lymphatic vessels of the liver drain into the thoracic and right lympthatic ducts via a number of lymph nodes
Pancreas position
- elongated accessory digestive gland
- lie retroperitoneally transversely across the bodies of the L1 and L1 vertebrae at the level of the transpyloric plane on the posterior abdominal wall
- contains exocrine and endocrine secreting cells
Pancreas position
- elongated accessory digestive gland
- lie retroperitoneally transversely across the bodies of the L1 and L1 vertebrae at the level of the transpyloric plane on the posterior abdominal wall
what does the pancreas contain
contains exocrine and endocrine secreting cells
how is the pancreas divided
- head (with projecting uncinate process)
- neck
- body
- tail
2 main ducts of the pancreas
- main pancreatic duct
- accessory pancreatic duct
what forms the hepatopancreatic ampulla of Vater
- main pancreatic duct unites with bile duct = hepatopancreatic ampulla of Vater = opens into the duodenum
blood supply to the pancreas
- Derived from branches of the splenic, gastrodudenal and superior mesenteric arteries
why are the blood vessels for pancreas ad duodenum the same
They have a close relationship
implications = pancreatic cancer surgery (Whipple’s procedure)
Lymphatic drainage follow both vessels to what nodes
follow blood vessels to drain into superior mesenteric or coeliac lymph nodes via pancreaticosplenic lymph nodes and pyloric lymph nodes
where is the nerve supply of the pancreas derived
derived from the vagus and abdominopelvis splanchnic nerves
Nerve supply of pancreas
parasympathetic (via posterior vagal trunk)
sympathetic (T6-10 via splanchnic nerves)
pass along the arteries from the coeliac and superior mesenteric plexus
what supplies the pancreatic acing and islet cells
parasympathetic (secretomotor) and sympathetic (vasoconstrictor) fibres also supply the pancreatic acing and islet cells
what is pancreatic secretion hormonally mediated by
Secretin and cholecystokinin of the duodenal epithelium
Pancreatic centroacinar cells
perform exocrine functions synthesise and secrete the digestive enzymes (amylase, trypsin, chymotrypsin, lipase and nucleases)
Pancreatic stellate cells
Perform functions relating to tissue repair and destruction of tumour cells
what do alpha cells secret in pancreas
glucagon
what do beta cells secret in pancreas
insulin
what do data cells secrete in pancreas
somatostatin
what do F cells secrete in pancreas
Pancreatic polypeptide
pancreatic islet of langerhans cells
alpha cells
beta cells
delta cells
F cells
perform endocrine functions
how is the pancreas formed
By 2 buds from the endodermal lining of the duodenum
what are the 2 buds that form the pancreas
- dorsal pancreatic bud
- ventral pancreatic bud ( out pocket from bile duct)
embryonic development of the pancreas
- 2 buds form pancreas (dorsal pancreatic bud and ventral pancreatic bud)
- dorsal pancreatic bud moves to the right - due to rotation of the gut tube and ventral pancreatic bud moves dorsally
- ventral pancreatic bud fuses with the lower part of the dorsal pancreatic bud
- lies posterior inferior to it
- the ventral pancreatic bud forms the uncinate process and part of the head of the Pancreas
- rest of pancreas formed by the dorsal pancreatic bud
- main pancreatic duct is formed by the distal part of the dorsal pancreatic duct and entire ventral pancreatic duct
- proximal part of the dorsal pancreatic duct may persist as the accessory pancreatic duct
- ventral apncreatic pud and duct with the proximal part of the bile duct - 2 ducts fuse together to for the hepatopancreatic ampulla
8 pancreatic islets and other secretory cells develop form the endodermal tissue cells in 3 month of feral life
when does insulin secretion begin
5th month of fatal life
Annular pancreas
- improper rotation and migration of parts of the tissues of the ventral pancreatic bud with the rotation of the duodenum
- constrict the duodenum and raise complete obstruction
accessory pancreatic tissue
ectopic pancreatic tissue may develop either in the oesophagus stomach and duodenum or in the small intestine
Blockage of the hepatopancreatic ampulla and pancreatitis
- blockage of hepatopancreatic ampulla by gallstone could lead to pancreatitis due to refill of bile into pancreatic duct
endoscopic retrograde cholangiopancreatography
procedure using a fibre optic endoscope passed through the mouth oesophagus stomach and duodenum and inject radiographic contrast medium for the diagnosis of both pancreatic and biliary disease
type of pancreatic cancer
- exocrine pancreatic cancer - adenoocarcinoa (head of pancreas)
- endocrine pancreatic cancer (pancratic neuroendocrine tumours)
how can pancreatic cancer in the head of pancreas lead to jaundice
cancer of the head of the pancreas often compresses and obstructors the bile duct, enlargement of the gallbladder and hepatopancreatic ampulla (close)
= leading to obstructive jaundice
how can pancreatic cancer in the neck and body of pancreas lead to jaundice
*cancer in neck and body of pancreas = hepatic portal or inferior vena caval obstruction
* extensive lympatic drainage of the pancreas into inaccessible lymph nodes
8 pancreatic cancer - metastasis to the liver early via the hepatic portal vein
pancreatectomy
Removal of most of the pancreas for treatment of chronic pancreatitis or cancer
Whipples procedure
- most common types of surgery
tumoru in head or neck of pancreas that haven’t yet spread
what is the extra hepatic part of the biliary tree made of
- right and left hepatic ducts which joins to form
- common hepatic duct which receives the cystic duct to form
- bile duct = unites with the main pancreatic duct to form
- hepatopancreatic ampulla which opens into the duodenum
gall bladder
visceral surface of the liver
what does the small intestine consist of
duodenum
jejunum
ileum
duodenum
- fist 25cm and widest part of small intestine
- c shaped course around the head of the pancreas
- starts at the junction with pylorus on the right and ends at duodena jejunal flexure on the left
4 parts og duodenum
- superior horizontal first part
- descending ventricle second part
- inferior horizontal 3rd part
- ascending vertical 4th part
jejunum
- proximal 2/5 of the small intestine following the duodenum
- left upper quadrant of the infracolic compartment of the abdominal cavity
- ileum is the distal 3/5 of the small intestine - located right lower quadrant
mesenteric border
concave margin of a small bowel loop
toward the axis of the root of the mesentery
anti mesenteric border
the convex margin of small bowel loop
facing away from the axis of the root of the mesentery
why is it good to be able to distinguish between mesenteric and anti mesenteric borders of small bowel loops
for radiologic diagnosis
intra abdominal disease processes
- diverticulosis = mesenteric border
- mockers diverticulum = anti mesenteric border
what does the large intestine consist of
cecum
appendix
ascending colon
transverse colon
descending colon
sigmoid colon
recum
anal canal
most common location of the appendix
retro caecal
variations in the position of the appendix
retro colic
retro caecal
sub caecal
pelvic
retro ideal
pre ideal
what 2 sources is the anal canal developed
- endodermal cloaca of the hindgut (upper 2/3)
- ectodermal cloaca (proctodaeum ) (lower 1/3)
what are the 2 embryonic regions of the anal canal delineated by
the pectinate (dentate) line
Above pectinate line = internal iliac lymph nodes
Below line = inguinal lymph nodes
clinical significance of the pectinate (dentate) line
2 regions of the anal canal differ in their blood and nerve supply and lymphatic drainage above and below the pectinate line
what nerves carry the sympathetic and visceral afferent fibres to and from the GI tract
splanchnic nerves
types of splanchnic nerves
Abdominopelvic splanchnic nerve (T5 L2/L3)
lower thoracic splanchnic
* greater splanchnic (T5 - T9/T10)
* lesser splanchnic (T10-T11)
* lumbar splanchnic (L1-L2/3)
what carries parasympathetic and visceral afferent fibres to and from the GI tract
Vagus nerves
Pelvis splanchnic nerves (s2-s4)
what leads to jaundice and pancreatitis in the binary tree and gallbladder
gall stones
