GI tract anatomy Flashcards
How long is the oesophagus?
18-25cm long.
Where does the oesophagus originate from?
The pharynx at the inferior border of the cricoid cartilage.
At what vertebral level does the oesophagus begin at?
C6
Where does the oesophagus end?
At the cardiac orifice of the stomach.
At what vertebral level does the oesophagus end at?
T11
At what vertebral level is the oesophageal hiatus?
T10
At what costal cartilage level is the oesophageal hiatus?
Level of the 7th costal cartilage
Where is the oesophagus situated in the thorax?
In the superior mediastinum between the trachea and T1-T4 vertebrae.
What are the 3 points of constriction in the oesophagus?
Where pharynx joins oesophagus (behind cricoid cartilage)
Where it is crossed anteriorly by the aortic arch and left main bronchus
As the oesophageal hiatus
How many sphincters does the oesophagus have?
2
What type fo muscle is the upper oesophageal sphincter made of?
Striated muscle
What structures form the upper oesophageal sphincter?
Cricopharyngeus muscle situated at the junction between the pharynx and oesophagus.
Why is the upper oesophageal sphincter normally constricted?
To prevent entrance of air into the stomach.
Where is the lower oesophageal sphincter?
Between oesophagus and stomach (GOJ).
At what vertebral level is the gastro-oesophageal junction (lower oesophageal sphincter)?
T11
What is the function of the lower oesophageal sphincter?
Prevent reflux of gastric contents into the oesophagus.
Where does the thoracic oesophagus received arterial supply from?
Branches of thoracic aorta and inferior thyroid artery.
What is the venous drainage of the thoracic oesophagus?
Azygous veins
Inferior thyroid vein
What is the arterial supply to the abdominal oesophagus?
Left gastric branch of the coeliac trunk
Left phrenic artery
What is the venous drainage of the abdominal oesophagus?
Left gastric vein
Azygous vein
Both of above drain into portal venous system
What is the lymphatic drainage of the upper 1/3 of the oesophagus?
Deep cervical nodes
What is the lymphatic drainage of the middle 1/3 of the oesophagus?
Superior and posterior mediastinal nodes.
What is the lymphatic drainage of the lower 1/3 of the oesophagus?
Left gastric and coeliac nodes.
What is the innervation of the oesophagus?
Vagus nerve (+ cervical and thoracic sympathetic trunks)
What is the action of the vagus nerve on the oesophagus?
Supplies muscles of oesophagus, stimulating glandular contraction.
What are the 3 anterior relations of the thoracic oesophagus?
Trachea
Left recurrent laryngeal nerve
Pericardium
What are the 2 anterior relations of the abdominal oesophagus?
What are the 4 posterior relations of the thoracic oesophagus?
Thoracic vertebrae
Thoracic duct
Azygous veins
Descending aorta
What are the 2 posterior relations of the abdominal oesophagus?
Right vagus nerve
Left crus of diaphragm
What are the 2 right relations of the thoracic oesophagus?
Pleura
Terminal part of azygous vein
What is the right relation of the abdominal oesophagus?
Lesser sac of peritoneum
What are the 4 left relations of the thoracic oesophagus?
Subclavian artery
Arch of aorta
Thoracic duct
Pleura
What is the left relation of the abdominal oesophagus?
Greater sac of peritoneum.
What are the 4 regions of the stomach?
Cardia
Fundus
Body
Pylorus
What structure arises from the greater curvature of the stomach?
The greater omentum
What structure arises fro the lesser curvature of the stomach?
The lesser omentum
What does the angular notch of the stomach mark?
The junction of the body and the pylorus of the stomach.
Where is the angular notch of the stomach?
Two thirds of the way along the lesser curvature
Which 2 sphincters are contained within the stomach?
Lower oesophageal sphincter
Pyloric sphincter
Which 4 factors is the sphincteric effect of the lower oesophageal sphincter created by?
The angle at which the oesophagus enters the stomach
Compression by positive intra-abdominal pressure
Presence of mucosal folds
Locality of the right crus of the diaphragm
What type of muscle is the pyloric sphincter made from?
Smooth muscle
What is the function of the pyloric sphincter?
Controls the passage of chime into the duodenum.
What are the 4 layers of the stomach from external to internal?
Serosa
Muscle
Submucosa
Mucosa
What are the 5 anterior relations of the stomach?
Anterior abdominal wall
Left costal margin
Left pleura and lung
Diaphragm
Left lobe of the liver
What are the 9 posterior relations of the stomach?
Lesser sac
Diaphragm
Spleen
Left adrenal gland
Upper left kidney
Splenic artery
Pancreas
Transverse mesocolon
Transverse colon
The arterial supply of the stomach is derived from where?
Coeliac trunk and it’s branches
What are the arterial anastomoses along the lesser curvature formed by?
Left and right gastric arteries
What are the arterial anastomoses along the greater curvature formed by?
Left and right gastro-mental arteries.
Which 5 arteries provide arterial supply to the stomach?
Left gastric
Right gastric
Left gastro-omental
Right gastro-mental
Short gastric arteries
Where do the left and right gastric veins drain into?
Portal vein
Where do the short gastric veins and the left gastro-mental vein drain into?
Splenic vein
Where does the right gastro-mental vein drain into?
Superior mesenteric vein
What is the lymph drainage of the stomach?
Gastro-mental lymph nodes along the curvatures.
What is the parasympathetic innervation of the stomach?
Anterior and posterior vagal trunks and their branches.
What is the sympathetic innervation of the stomach?
T6-T7 spinal segments.
Which part of the gut wall do peptic ulcers extend through to?
Muscular mucosae
Which part of the stomach do gastric ulcers most commonly form in?
Lesser curvature
Which part of the duodenum do duodenal ulcers most commonly occur?
Proximal duodenum
What is the most frequent perforation site of peptic ulcers?
First part of duodenum
How long is the first part of the duodenum?
5cm
Which vertebral body does the first part of the duodenum lie anterior to?
L1
How is the first part of the duodenum connected to the liver?
Hepatoduodenal ligament
How long is the 2nd part of the duodenum?
7-10cm
Which vertebral bodies does the second part of the duodenum descend along?
L1-L3
The 2nd part of the duodenum curves inferiorly around which structure?
Head of pancreas
How long is the 3rd part of the duodenum?
6-8cm
Which vertebral body does the 3rd part of the duodenum cross?
L3
Which vessels does the 3rd part of the duodenum cross anteriorly over?
IVC and aorta
Where is the 3rd part of the duodenum located in relation to the pancreas?
Inferior to the pancreas
How long is the 4th part of the duodenum?
5cm long
Next to which vertebral body does the 4th part of the duodenum begin?
L3
Which vertebral level does the 4th part of the duodenum ascend to?
L2
Which part of the duodenum is the only part which is intraperitoneal?
1st part
Which parts of the duodenum are retroperitoneal?
All except the 1st part.
What is the ligament of Treitz?
Suspensory muscle of the duodenum
At what vertebral level does the ligament of Treitz sit?
L2
Which structures does the ligament of Treitz connect?
Connects duodenum, jejunum and duodenojejunal flexure to connective tissue surrounding SMA and coeliac artery.
What is the arterial supply to the duodenum?
Pancreaticoduodenal arteries
Which aspect of the duodenum is supplied by the superior pancreaticoduodenal artery?
Duodenum proximal to entry of bile duct (section derived from foregut)
Which aspect of the duodenum is supplied by the inferior pancreaticoduodenal artery?
Duodenum distal to entry of bile duct (section derived from midgut)
The superior pancreaticoduodenal artery arises from where?
Gastroduodenal artery
The inferior pancreaticoduondeal artery arises from where?
SMA
Where do the duodenal veins drain into?
Hepatic portal vein
Where do the anterior lymph vessels of the duodenum drain into?
Pancreaticoduondeal + pyloric nodes
Where do the posterior lymph vessels of the duodenum drain into?
Superior mesenteric nodes
What is the innervation of the duodenum?
Vagus + sympathetic nerves via plexuses on pancreaticoduodenal arteries.
Where does the jejunum begin?
At the attachment of the suspensory muscle of the duodenum (ligament of Treitz)
Which abdominal region does the ileum normally lie under?
RLQ
Which abdominal region does the jejunum normally lie under?
LUQ
Where does the ileum end?
Ileocaecal junction
The jejunum and ileum are suspended inside what?
Mesentery
What is the arterial supply to the jejunum and ileum?
SMA
At which vertebral level does the SMA arise?
L1
What is the venous drainage of he jejunum and ileum?
Superior mesenteric vein
What does the superior mesenteric vein unite with to form the hepatic portal vein?
Splenic vein
What is the lymphatic drainage of the jejunum and ileum?
Mesenteric nodes
What is the lymphatic drainage of there terminal ileum?
Ileocolic nodes
Which spinal segments do the sympathetic nerves to the jejunum and ileum arise from?
T5-T9
Where are the parasympathetic nerves to the jejunum and ileum derived?
Posterior vagal trunk
What is a Meckel’s diverticulum?
A vestigial remnant of the vitellointestinal duct
Where would a Meckel’s diverticulum be located?
Distal ileum (within 60-100cm of the ileocaecal valve)
Where do mocker’s diverticulum receive their blood supply from?
Mesentery of the ileum
What are the 2 most common types of ectopic mucosa found in Meckel’s diverticulum?
Gastric (50%)
Pancreatic (5%)
What is the most common age in which a Meckel’s diverticulum presents?
2
What is the role of the anal canal?
Maintenance of faecal continence and defecation.
Where does the anal canal start?
Anorectal junction
What is the innervation of the internal anal sphincter?
Enteric neutrons of the myenteric plexus (Auerbach’s plexus)
Which anal sphincter is involuntary?
Internal
What type of muscle is the internal anal sphincter made up of?
Smooth muscle
What is the innervation of the external anal sphincter?
Somatic efferent neurons
What is the pectinate (dentate) line?
A line that divides the upper two thirds and lower third of the anal canal
Where is the anus located?
Within the anal triangle of the perineum
What are the anterior relations of the anus in males?
Perineal body
Urethra
Bulb of penis
What are the anterior relations of the anus in females?
Perineal body
Vagina
What are the posterior relations of the anus?
Anococcygeal ligament
Coccyx
Sacrum
What are the lateral relations of the anus?
Ischioanal fossa
What is the arterial supply to the anal canal above the pectinate line?
Superior rectal artery (branch of IMA)
What is the venous drainage of the anal canal above the pectinate line?
Superior rectal vein (drains into inferior mesenteric vein)
What is the arterial supply to the anal canal below the pectinate line?
Inferior rectal artery (branch of internal pudendal artery)
What is the venous drainage of the anal canal below the pectinate line?
Inferior rectal vein (drains into internal pudendal vein)
What is the lymphatic drainage of the anal canal above the pectinate line?
Internal iliac nodes
What is the lymphatic drainage of the anal canal below the pectinate line?
Superficial inguinal nodes
What is the innervation of the anal canal above the pectinate line?
Inferior hypogastric plexus (sensitive to stretch only)
What is the innervation of the anal canal below the pectinate line?
Inferior anal nerves (branches of pudendal nerve)
**Sensitive to pain, touch, pressure + temperature
What spinal segments are responsible for the anal reflex?
S2-S4
Which nerve carries the anal reflex arc?
Pudendal nerve
How long is the rectum?
12-15cm
Where does the rectum start?
Rectosigmoid junction
At what vertebral level does the rectum start?
L3 (where the mesocolon ends)
At what vertebral level does the mesocolon end?
L3
What are the 3 flexures of the rectum?
Sacral
Anorectal
3 x lateral (superior, intermediate, inferior)
Which part of the rectum are faeces stored in?
Rectal ampulla (distal end of rectum)
Which flexure of the rectum is responsible for producing the angle of the rectum that maintains faecal continence?
Anorectal flexure
The tone of which muscles forms the anorectal flexure?
Puborectalis muscle
Relaxation of which muscle allows the anorectal angle to be reduced + defecation to occur?
Puborectalis muscle
Where does the rectum end?
Anorectal junction
Which muscle sling is present at the level where the rectum ends?
Puborectalis sling
What are the anterior relations of the rectum in men?
Sigmoid colon
Ileum
Rectovesical pouch
Bladder
Prostate
What are the anterior relations of the rectum in women?
Sigmoid colon
Ileum
Rectouterine pouch
Vagina
Cervix
What are the posterior relations of the rectum?
Sacral plexus
Sacrum
Coccyx
Piriformis
Coccygeus
Levator ani
Which 3 arteries provide arterial supply to the rectum?
Superior, middle and inferior rectal arteries
The superior rectal artery is a branch of what?
IMA
The middle rectal artery is a branch of what?
Internal iliac artery
The inferior rectal artery is a branch of what?
Pudendal artery
What is the venous drainage of the rectum?
Superior, middle and inferior rectal veins
Where do the superior rectal veins drain into?
Portal venous system
Where do the middle and inferior rectal arteries drain into?
Systemic venous system
What can the portosystemic anastomosis in the anal canal cause?
Haemorrhoids
Where does lymph from the upper third of the rectum drain to?
Pararectal nodes > inferior mesenteric nodes
Where does lymph from the lower third of the rectum drain into?
Internal iliac lymph nodes
What is the sympathetic innervation of the rectum?
Lumbar splanchnic nerves
AND
superior and inferior mesenteric plexuses
What is the parasympathetic innervation of the rectum?
Pelvic splanchnic nerves
AND
inferior hypogastric plexuses
What is the sensory innervation of the rectum?
Pelvic splanchnic nerves
AND
inferior hypogastric plexus
Which structure plays an important role in limiting the spread of carcinoma to the rectum?
Rectovesical fascia
What is the rectovesical fascia?
A membranous partition situated at the lowest part of the rectovesical pouch.
In males, what does the rectovesical pouch separate?
Rectum from prostate + bladder.
In females, what does the rectovesical pouch separate?
Rectum from vagina.
Is the ascending colon peritoneal or retroperitoneal?
Retroperitoneal
Is the transverse colon intraperitoneal or retroperitoneal?
Intraperitoneal
What is the least fixed part of the colon?
Transverse colon
Is the descending colon intraperitoneal or retroperitoneal?
Retroperitoneal
Is the sigmoid colon intraperitoneal or retroperitoneal?
Intraperitoneal
What vertebral level does the sigmoid colon finish at?
S3
What are the 3 anterior relations of the ascending colon?
Anterior abdominal wall
Small intestine
Greater omentum
What are the 5 posterior relations of the ascending colon?
Quadratus lumborum
Iliacus
Right kidney
Iliohypogastric nerve
Ilioinguinal nerve
What are the 2 anterior relations of the transverse colon?
Anterior abdominal wall
Greater omentum
What are the 4 posterior relations of the transverse colon?
Duodenum
Jejunum
Ileum
Head of pancreas
What are the 3 anterior relations of the descending colon?
Anterior abdominal wall
Small intestine
Greater omentum
What are the 5 posterior relations of the descending colon?
Quadratus lumborum
Iliacus
Left kidney
Iliohypogastric nerve
Ilioingunal nerve
What are the 3 anterior relations of the sigmoid colon?
Urinary bladder
Uterus (females)
Upper vagina (females)
What are the 2 posterior relations of the sigmoid colon?
Rectum
Sacrum
Where does the superior mesenteric artery arise?
L1 (1cm below coeliac trunk)
Where does the inferior mesenteric artery arise?
L3
Which parts of the colon are supplied by the SMA?
Ascending colon
2/3rds transverse colon
Which parts of the colon are supplied by the IMA?
1/3rd transverse colon
Descending colon
Sigmoid colon
What is the arterial supply of the ascending colon?
SMA:
Ileocolic artery
Right colic artery
What is the arterial supply to the transverse colon?
SMA:
Right colic artery
Middle colic artery
IMA:
Left colic artery
What is the arterial supply of the descending colon?
Left colic artery (IMA)
What is the arterial supply of the sigmoid colon?
Sigmoid arteries (IMA)
What is the venous drainage of the ascending colon?
Ileocolic and right colic veins (drain to SM vein)
What is the venous drainage of the transverse colon?
Superior mesenteric vein
What is the venous drainage of the descending colon?
Left colic vein (drains to IM vein)
What is the venous drainage of the sigmoid colon?
Sigmoid veins (drain to IM vein)
Where do the superior and inferior mesenteric veins drain into?
Hepatic portal vein
What is the lymphatic drainage of the ascending colon and proximal 2/3 of the transverse colon?
Colic nodes
Superior mesenteric nodes
What is the lymphatic drainage of the distal 1/3 of the transverse colon, descending colon and sigmoid colon?
Colic nodes
Inferior mesenteric nodes
Where do the colic, superior mesenteric and inferior mesenteric nodes drain to?
Cisterna chyli > thoracic duct
Which structures are innervated by the superior mesenteric plexus?
Ascending colon
Proximal 2/3 transverse colon
Which structures are innervated by the inferior mesenteric plexus?
Distal 1/3 transverse colon
Descending colon
Sigmoid colon
Where is the most common site of diverticulitis?
Sigmoid colon
What does the caecum do?
Acts as a reservoir for chyme received from the ileum.
Is the caecum intraperitoneal or retroperitoneal?
Intraperitoneal
What part of the caecum is the appendix attached to?
Posteromedial end of the caecum.
What are the 2 most common locations for the end of the appendix to be found?
Retrocaecal (ascending retrocaecal = 64%)
Subcaecal (32%)
What is the arterial supply to the caecum?
Anterior and posterior caecal arteries
What is the venous drainage of the caecum?
Ileocolic vein
What is the arterial supply to the appendix?
Appendicular artery
What is the venous drainage from the appendix?
Appendicular vein
Where does lymph from the caecum and appendix drain to?
Nodes in mesoappendix and ileocolic nodes.
Where do the ileocolic nodes lie?
Along the ileocolic artery
What is the innervation of the caecum and appendix?
Derived from sympathetic and parasympathetic nerves of the superior mesenteric plexus
Which part of the spinal cord do afferent fibres from the appendix travel to?
T10 segment of spinal cord
The sympathetic fibres supplying the caecum and appendix originate from where?
Lower thoracic part of the spinal cord
The parasympathetic fibres supplying the caecum and appendix originate from where?
Vagus nerve
Where is does McBurney’s point lie?
1/3rd of the distance from the ASIS to the umbilicus.
What does McBurney’s point correspond to?
The most common position of the attachment the base of the appendix to the caecum.
