anatomy of the GI system Flashcards
parietal peritoneum
- lines abdominal cavity
- retroperitoneal organs (behind) eg kidneys, pancreases
- on posterior abdominal wall
visceral peritoneum
- covers organs into the abdominal or pelvic cavities
- intraperitoneal organs - covered by visceral peritoneum eg stomach jejunum
what is the peritoneum
- serous membrane
- aids movement making it friction free
- peritoneum fluid
what is the peritoneum that covers the intestine called
mesentary
what is the peritoneum that covers the stomach called
omentum
- hangs from the greater curvature of the stomach, fatty material, can migrate to site of infection and wrap around it
what are the compartments of the stomach
- lesser sac behind the stomach
- greater sac
parts of the foregut
- Oesophagus
- Stomach
- Proximal half duodenum
- Liver
- Pancreas
- Spleen
the oesophagus
- Begins at inferior end of pharynx
- Goes through the diaphragm at T10
- 3 constrictions: origin, crossed arch of aorta and left bronchus, through diaphragm
- Constricted by contractions of the diaphragm
- Stratified squamous epithelium
Inner circular, outer longitudinal muscle
the stomach
- chemically and physically break down food
- Inner oblique layer
- Fundus, body, lesser curvature and the greater curvature (where greater omentum), pyloric antrum, pyloric canal
- Rugay - funnal food down
the small intestine - duodenum
- Retroperitoneal organ - needs to be protected
- 4 parts:
- Superior L1: Intraperitoneal (very beginning)
- Descending L2/3: Receives bile duct and pancreatic duct, Opens onto the major duodenal papilla, MDP marks foregut midgut boundary
- Transverse L3
- Ascending L2: Intraperitoneal (very end)
what are the organs in the midgut
- Distal half duodenum
- Jejunum
- Ileum
- Caecum
- Ascending colon
- Proximal 2/3rds transverse colon
jejunum and ileum
- Attached to posterior abdominal wall by the mesentery
- Peritonise - intraperitoneal structures
description of the jejunum
- colour: deep red
- wall: thick wall (many folds, absorb more), large, tall and closely packed plicae circulares
- vascularity: greater
- vasa recta: long
- arterial arcades: few large loops
- peyer patches: few
description of the ileum
- colour: pale pink
- wall: thin and light, low and spare plicae circulares, absent in distal part
- vascularity: less
- vasa recta: short
- arterial arcades: numerous short loops
- peyers patches: many
large intestine
- Caecum: Appendix attached
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal: Haustra - formed by taenia coli - creates pouched, Omental appendage
- Taenia coli
what are the organs in the hind gut
- Distal 1/3rd transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal
the rectum and anal canal
- Continuous with sigmoid colon at S3
- Continuous with anal canal at tip of coccyx
- 3 transverse rectal folds
- Internal anal sphincter - smooth muscle, involuntary
- External anal sphincter - made of skeletal matter, allows for voluntary movement
liver
- 4 lobes - left, right,(anterior view) caudate and quadrate
- Porta hepatis - hilum of liver, entrance and exit for the main structures associated with the liver
- Portal tirade - hepatic portal vein, hepatic artery proper, bile duct: Runs between peritoneum hepatoduodenal ligament
- Coronary ligaments superiorly
- Between liver and diaphragm
- Surrounded by bare area
- Triangular ligaments laterally
- Falciform ligament anteriorly’
- Contains ligament teres (umbilical vein remnant)
gallbladder
- Store and concentrates bile produced by the liver
- Right and left hepatic duct, form to get common hepatic duct, to cystic duct and the bile duct - binds with main pancreatic duct
pancreas
- parts: head, neck, body, tail, uncinate process
- Main pancreatic duct opens into the 2nd part of the duodenum with the bile duct as the hepatopancreatic ampulla
- Retroperitoneal
- At the transpyloric plane
what are the branches of the aorta
- coeliac trunk (T12)
- superior mesenteric artery (L1)
- inferior mesenteric artery (L3)
what does the coeliac artery supply
- Lower oesophagus
- Stomach
- Proximal half of duodenum
- Liver
- Gall bladder
- Pancreas
what are the 3 arteries off the coeliac trunk
- left gastric
- splenic
- common hepatic
left gastric artery
- Runs of lesser curvature of the stomach
- Off to oesophageal branches
splenic artery
- Runs to supply spleen
- Short gastric - fundus
- Spleen
- Left gastro omental artery - along greater curvature of stomach
common hepatic artery
- Right gastric
- Proper hepatic artery
- Gastroduodenal: Super duodenal, Right gastro omental
- Superior pancreaticoduodenal
what does the superior mesenteric artery supply
- Distal half of duodenum
- Small intestine
- Large intestine
what are the breanckes of the superior messenterid artery
- Inferior pancreaticoduodenal artery
- Jejunal and ileal branches
- Runs between 2 layers of the mesentery
○ Ileal branches
○ appendicular
○ Ileocolic artery: Inferior branches to ileocolic junction, Superior branch to ascending colon - Right colic artery: To ascending colon
- Middle colic artery: To transverse colon
where does the inferior mesenteric artery supply
Large intestine distal to splenic flexure up to anal canal
what are the branches of the inferior mesenteric artery
- Left colic artery: Ascending branch in transverse mesocolon, Descending branch to lower descending colon
- Superior sigmoid artery and sigmoid arteries: In sigmoid mesocolon, Lowest part of descending colon, Sigmoid colon
- Superior rectal artery: In right and left branches either side of rectum, Supply rectum to inferior anal sphincter
what is the hepatic portal vein
- Formed by union of splenic vein and superior mesenteric vein
- Posterior to the neck of the pancreas
- Receives most of the blood from the GI tract
what are the parts of the autonomic nervous system
- Coeliac ganglion: foregut
- Superior mesenteric ganglion: midgut
- Inferior mesenteric ganglion: Hindgut
what is the parasympathetic pathway
- rest and digest
- craniosacral outflow
what is the sympathetic pathway
- fight or flight
- throacolumar
where does the oesophagus originate from
the inferior border of the cricoid cartilage (C6)
- travels down to the cardiac orifice of the stomach - T11
what are the layers of the oesophagus
- adventitia
- muscle layer
- submucosa
- mucosa
arterial supply of the thoracic oesophagus
- thoracic aorta
- inferior thyroid artery
venous drainage of the thoracic oesophagus
- branches of the azygous veins
- inferior thyroid vein
arterial supply of the abdominal oesophagus
- left gastric artery
- left inferior phrenic artery
venous drainage of the abdominal oesophagus
- portal circulation via left gastric vein
- systemic circulation via azygous vein
innervation of the oesophagus
- the oesophageal plexus
- this is formed by the parasympathetic vagal trunk and sympathetic fibres from cervical and thoracic sympathetic trunks
parts of the lymphatic drainage of the oesophagus
- superior third - deep cervical lymph nodes
- middle third - superior and posterior mediastinal node
- lower third - left gastric and celiac nodes
greater curvature of the stomach
- long convex lateral border of the stomach
- arising at cardiac notch, arching backwards and inferiorly to the left
- curves to the right as it continues medially to reach the pyloric antrum
blood supply of the greater curvature of the stomach
- right and left gastro-omental arteries
lesser curvature of the stomach
- shorter, concave, medial surface of stomach
- angular notch indicates the junction of the body and pyloric region
- gives attachment to hepatogastric ligament
blood supply of the lesser curvature of the stomach
- left gastric artery
- right gastric branch of the hepatic artery
what are the sphincters of the stomach
- inferior oesophageal sphincter
- pyloric sphincter
what is the function of the inferior oesophageal sphincter
- transition point of the oesophagus and the stomach
- allows food to pass through the cardiac orifice into the stomach
- not voluntary controlled
what is the function of the pyloric sphincter
- controls the exit of chyme from the stomach (food and gastric acid mixture)
- contains smooth muscle
greater omentum
- hangs from greater curvature of the stomach
- folds back on itself attaching to the to the transverse colon
- contains lymph nodes
lesser omentum
- continuous with peritoneal layers of the stomach and duodenum
- arises from lesser curvature of stomach
- ascends to attach to the liver
- function: attach stomach and duodenum to liver
arterial supply of stomach
- from celiac trunk
- left gastric, right gastric
- right gastro-omental, left gastro-omental
venues supply of the stomach
- right and left gastric vein drain into the hepatic portal vein
innervation of the stomach
autonomic nervous system
- parasympathetic - anterior and posterior vagal trunks from vagus nerve
- sympathetic nerve T6-T9 spinal cord, carries pain transmitting fibres
where do stomach lymph fluids drain
- into gastric and gastro-omental lymph nodes
how are the ileum and jejunum attached to the posterior wall
by the mesentery
where does the ileum end
at the ileocaecal junction
what is the function of the ileocecal valve
to stop a reflex of material back into the ileum
arterial supply of the duodenum
- gastroduodenal artery = proximal to the major duodenal papilla
- inferior pancreaticoduodenal artery = distal to major duodenal papilla
what are the lymphatics of the duodenum
- pancreatoduodenal and superior mesenteric nodes
arterial supply of the jejunum and ileum
superior mesenteric artery
venous drainage of the jejunum and ileum
superior mesenteric vein
lymphatics of the jejunum and ileum
superior mesenteric nodes
vascular supply of the caecum
superior mesenteric vessels
- artery = ileocolic artery
- vein = ileocolic vein
innervation of the caecum
- sympathetic and parasympathetic branches of the autonomic nervous system
- from the ileocolic branch of the superior mesenteric plexus
lymphatic drainage of the caecum
ileocolic lymph nodes
what are the possible positions of the appendix
- pre-ileal
- post-ileal
- sub-ileal
- pelvic
- subcecal
- paracecal
- retrocecal
vascular supply of the appendix
branches of the superior mesenteric vessels
arterial supply of the appendix
appendicular artery
innervation of the appendix
sympathetic and parasympathetic branches of autonomic nervous system
- ileocolic branch of the superiro mesenteric plexus
lymphatic drainage of the appendix
ileocolic lymph nodes
what is the paracolic gutters
two spaces between the ascending/ descending colon and the posterolateral abdominal wall
what is the importance of the paracolic gutters
allow material that has been released from inflamed or infected abdominal organs to accumulate elsewhere in the abdoment
venous drainage of the ascending colon
ileocolic and right colic veins
venous drainage of the transverse colon
middle colic vein
venous drainage of the descending colon
left colic vein
venous drainage of the sigmoid colon
sigmoid vein
innervation of the midgut
sympathetic, parasympathetic and sensory supply from superior mesenteric plexus
innervation of the hindgut
sympathetic, parasympathetic and sensory from inferior mesenteric plexus
- parasympathetic = pelvic splanchnic
- sympathetic = lumbar splanchnic
lymphatic drainage of the large intestine
- ascending and transverse = superior mesenteric nodes
- descending and sigmoid = inferior mesenteric nodes
arterial supply of the rectum
- superior rectal artery
- middle rectal artery
- inferior rectal artery
venous drainage of the rectum
- superior rectal vein
- middle rectal vein
- inferior rectal vein
- into portal venous system
innervation of the rectum
sensory and autonomic
lymphatic drainage of the rectum
- pararectal lymph nodes
- internal iliac lymph nodes (lower aspect)
