GI Anatomy 2 Flashcards
Which nerves run anteroinferiorly on the transversus abdominis muscle?
T9 to L1
Where does the transversalis fascia lie?
Superficial to the parietal peritoneum
What is the nerve supply to the parietal peritoneum and how do these nerves course?
Anterior rami of spinal nerves T7 - L1 (somatic afferents)
The run in between the transversus abdominus and internal oblique then at lateral edge of the rectus sheath, enter the rectus sheath and pass posterior to the rectus abdominis (near to the midline, they give off an anterior cutaneous branch)
What characteristic does suspension by a mesentery confer to an organ?
1) Mobility
2) Prevent tangling
3) Conduit for vessels and nerves
Which organs of the abdominal cavity lie retro peritoneally?
1) 2nd and 3rd parts of the duodenum
2) Supra renal glands
3) Kidneys
4) Pancreas
5) Ascending, descending colon
6) Rectum
7) Aorta and IVC
8) Ureters
What is an adhesion?
Fibrous bands of scar tissue that form between internal organs, joining them together abnormally
How many layers of peritoneum in a mesentery?
2
How many layers of peritoneum in the greater omentum?
4
How many layers of peritoneum in the transverse mesocolon?
6
What is the mesocolic shelf and what does it separate the abdominal cavity into?
Mesocolic shelf = transverse mesocolon
Separates the abdominal cavity into a supra colic space and an infracolic space
What is the space in between the liver and the diaphragm called?
The subphrenic space
What is the sub hepatic channel and what is its inferior limit?
Space under the liver, the inferior limit is the transverse mesocolon
Which organs are located in the supracolic compartment?
1) Liver and gall bladder
2) Stomach
3) Duodenum
4) Spleen
What is the hepatorenal pouch of Rutherford Morison and what is it continuous with?
Space posterior to the liver limited by the posterior abdominal wall and the right kidney
Continuous with the right paracolic gutter
Why is the hepatorenal pouch of Rutherford Morison of surgical significance?
Lowest and deepest space within the abdominal cavity when youre lying supine that free fluid and pus gathers in
What is the name of the opening that leads into the lesser sac?
Epiploic foramen (of Winslow)
What structures form the 4 boundaries of the epiploic foramen of winslow?
Anterior = free edge of lesser omentum (gastroduodenal ligament) containing the portal triad Posterior = IVC Inferior = First part of duodenum Superior = caudate lobe of the liver
What ligament runs between the spleen and the left kidney?
Lienorenal ligament
What is the phrenico colic ligament?
fold of peritoneum between the diaphragm and the splenic flexure
What are the paracolic gutters?
depressions formed between the lateral margins of the ascending and descending colon and the posterolateral body wall
Why are the paracolic gutters clinically important?
Gutters through which material can pass from one part of the abdominal cavity to another
Major vessels and lymphatics tend to be on the medial or posterior side of the colon
Paracolic gutters are a good access point for surgeons without cutting vasculature
What is the name for the line of attachment of the mesentery to the posterior abdominal wall?
The root of the mesentery
Where does the mesentery run from and to?
From the duodenojejunal flexure to the right sacroiliac joint
Which side of the infracolic compartment communicates with the pelvis?
The left infra colic compartment
Which blood vessels run in the mesoappendix?
Appendicular artery (branch of posterior ileocolic artery from the superior mesenteric artery) Appendicular vein (empties into the ileocolic vein)
Where does the appendix receive its innervation from, where do visceral afferent fibres from the appendix enter the spinal cord?
Fibres from the superior mesenteric plexus
Visceral afferent enter the spinal chord at T10
Over which artery is the sigmoid mesocolon attached to the posterior abdominal wall?
The division of the left common iliac artery
Where does the rectovesical pouch lie?
inbetween the bladder and the rectum
Where does the recto uterine pouch (of douglas) lie?
Inbetween the rectum and the uterus
Where does the uterovesical pouch lie?
inbetween the uterus and the rectum
What is the difference in innervation of the visceral and the parietal peritoneum?
1) Visceral peritoneum = visceral afferent and efferent
2) Parietal peritoneum = somatic branches of associated spinal nerves (T7-L1)
What are the parts of the stomach?
1) Cardia (gastroesophageal junction)/ cardiac orifice
2) Fundus (superior to cardia)
3) Body
4) Pyloric antrum
5) Pyloric canal (pylorus)
What is meant by an anatomical sphincter and a functional sphincter?
Anatomical sphincters have localised and circular muscle thickening
Functional sphincters do not have this and achieve their action through muscle contraction
Are the pylorus and cardiac orifice anatomical or physiological sphincters?
Cardiac orifice = physiological sphincter
Pylorus = anatomical sphincter
At what level is the transpyloric plane?
Passes through the lower border of L1
Where does the pylorus lie?
To the right of the midline in the transpyloric plane (through lower border of L1)
Which nerves may sink into the muscular wall of the stomach anteriorly and posteriorly?
Anteriorly = left vagus Posteriorly = right vagus
How did the left and right vagus nerves come to lie anteriorly and posteriorly (respectively) on the stomach?
Rotation of the stomach 90 degrees on the craniocaudal axis during development
What is the difference between a hiatal hernia and a congenital hernia?
Hiatal hernia is aquired, stomach pushed through oesophageal hiatus, reducible hernia
Congenital hernia is due to insufficient elongation of the oesophagus during development, some of the stomach will lie supradiaphragmatically, hernia is irreducible
What does the superior mesenteric artery run within?
The mesentery
What does the coeliac trunk supply?
The GI tract down to the major duodenal papilla The liver (and the gall bladder), the pancreas and the spleen
At what level of the coeliac trunk given off?
Anterior to the upper border of L1 (immediately below aortic hiatus of diaphragm)
What arteries supply the greater curvature of the stomach and where do they arise from?
Left gastro-omental artery (from splenic artery)
Right gastro-omental artery (from gastroduodenal artery from common hepatic artery)
Short gastric arteries (from splenic artery)
What arteries supply the lesser curvature of the stomach and where do they arise from?
The left gastric artery (from the coeliac trunk)
The right gastric artery (from the common hepatic artery)
Where does the oesophageal artery arise from?
The left gastric artery (From the coeliac trunk)
What 3 branches come off the coeliac trunk?
1) The left gastric
2) The splenic
3) The common hepatic
What are the components of the midgut?
The major duodenal papilla to the proximal 2/3 of the transverse colon
Is there any macroscopic demarkation between the jejunum and ileum?
No
What are the 4 main differences between the jejunum and ileum?
1) Jejunum has thicker walls
2) Jejunum has more and more prominent plicae circulares (mucosal fold)
3) Jejunum has longer vasa recta
4) Jejunum has less arterial arcades
What is Meckel’s diverticulum and what is its symtoms?
Present in 2% of the population
Remnant of the vitelline duct creates an outpocketing of the ileal wall
Usually asymptomatic but may contain ectopic pancreatic or gastric tissue causing inflammation, ulceration and bleeding
What are appendices epiploicae?
Fatty tags present on the ascending, transverse and descending colon
What are the main differences between the large and small intestine?
1) Large intestine = greater callibre
2) Large intestine has appendices epiploicae
3) Large intestine has haustra (sacculations)
4) Large intestine longitudinal muscle is arranged into taeniae coli
What is diverticulosis?
Pouches from in the wall of the colon
Diverticula in diverticulosis dont cause symptoms
What is diverticulitis?
Infection of diverticula causes them to become inflammed
Symptoms of severe abdominal pain, fever and diarrhoea
What is the caecum?
Blind ended pouch of the large bowel that projects downwards from the beginning of the ascending colon
What is the retrocaecal fossa?
Structure that separates the caecum from the posterior wall of the right iliac fossa and can extend as far up as the liver
Where is the appendix attached to the caecum?
Posteriomedial wall of caecum, below the ileo-caecal junction
What are the initial symptoms of acute appendicitis?
1) Para umbilical discomfort
2) Malaise
3) Diarrhoea or constipation
Why is it dangerous to use laxatives in the case of appendicitis?
Vigorous contractions of the gut wall often ruptures the inflamed appendix leading to peritonitis
What is McBurney’s point?
Surface marking of the appendix in the right iliac fossa
2/3 of the way from the umbilicus to the ASIS
In what percentage of adults is the appendix retro caecal and where does it lie in the rest?
65% its retro caecal
25% hangs over the pelvic brim
Why can an abscess in the appendix lead to pain the shoulder?
Pus can travel upwards in the right paracolic gutter to the subphrenic space and result in referred pain to the shoulder
Where is an incision commonly made in surgery to remove the appendix and how is the root of the appendix found?
Incision at McBurney’s point
Tracing the Tenaie coli
Where does the descending colon extend from and to?
From the splenic flexure to the pelvic brim
At the pelvic brim it aquires a mesentery and becomes the sigmoid colon
At what vertebral level does the superior mesenteric artery leave the abdominal aorta?
Lower border of L1
Immediately below the coeliac artery
What branches come off the superior mesenteric artery (to what side and in order)?
1) Inferior pancreaticoduodenal (right)
2) Middle colic (right)
3) Right colic
4) Jejunal arteries (left)
5) Ileal arteries (left)
6) Ileocolic artery (right)
What does the middle colic artery supply mainly?
Transverse colon
What does the right colic artery supply mainly?
Ascending colon
Where do the anterior and posterior cecal arteries arise from?
The ileocecal artery (from the superior mesenteric artery)
What arteries supply the jejunum and ileum?
Jejunal and ileal arteries
What is the duodeno-jejunal junction surrounded by?
A fold of peritoneum containing muscle fibres called the suspensory muscle of the duodenum
What vertebral levels do the kidneys and suprarenal glands lie between?
T12 and L3
Where does the hindgut run from and to?
Distal 1/3 of transverse colon to cranial 2/3 of anal canal
At what vertebral level is the inferior mesenteric artery given off?
L3
What are the 2 main branches of the inferior mesenteric artery and what other artery does it give off?
1) Left colic artery
2) Sigmoid arteries
3) Also gives off the superior rectal artery
Why would an AAA that was obstructing the inferior mesenteric artery not affect gut function?
Marginal artery is large enough to supply oxygenated blood to the parts of the colon supplied by the inferior mesenteric artery via the superior mesenteric artery
Thus all of the colon still recieves oxygenated blood
At what vertebral level does the sigmoid colon become the rectum?
S3
How does the surface of the large intestine change from the rectosigmoid junction onwards?
Taenia coli and appendices epiploicae are no longer present
What is a sigmoid volvulus?
When the sigmoid colon twists on its mesentery resulting in a closed loop obstruction full of faeces and gas
Why is a sigmoid volvulus a dangerous condition?
Venous infarction leads to perforation and faecal peritonitis
How far above the cutaneous margin of the anus does the ano-rectal junction lie?
3 cm
How do the peritoneal attachments of the rectum and sigmoid colon differ?
Sigmoid colon = intraperitoneal
Rectum is primarily retroperitoneal
What is the pelvic floor?
Sheet of muscle that separates the pelvic cavity above from the perineum below
What arteries supply the rectum and where do they originate from?
1) 1 superior rectal artery (from the inferior mesenteric - major artery to the rectum)
2) R+L middle rectal arteries (from the internal iliac)
3) R+L inferior rectal arteries (from the internal pudendal from the internal iliac)
Definition of a portal vein?
Vein formed from the fusion of other veins that terminates in a capillary network that delivers blood to somewhere other than the heart
Other than the hepatic portal vein where is the one other portal vein in the body?
Brain
Hypophyseal system - connects the hypothalamus to the anterior pituitary
By which veins do the foregut, midgut and hindgut drain?
1) Foregut - straight into hepatic portal vein or one of its tribituaries
2) Midgut - superior mesenteric vein
3) Hindgut - inferior mesenteric vein
What veins do the right gastric and left gastric veins generally drain into?
portal vein
What veins do the Short gastric veins generally drain into?
Splenic vein
Which vessel does the left and right gasto omental (same as gastroepiploic vein) drain into?
Splenic vein
Where do the oesophageal veins drain?
Azygous vein
What is a portosystemic anastamoses?
Site of anastamosis between the portal and systemic venous systems
What are the 3 sites of portosystemic anastamoses?
1) Gastro oesophageal junction around the cardia of the stomach
2) Anus: superior rectal vein of the portal system with the middle and inferior rectal veins of the systemic system
3) Anterior abdo wall around umbilicus: para umbilical veins anastamose with epigastric veins
What is the clinical significance of portosystemic anastamoses?
1) In a patient with portal hypertension, blood enters collateral channels at portosystemic anastamoses
2) Venous enlargement (varices) tends to occur at the sights of portosystemic anastamoses
3) Varices (in particular oesophageal) are susceptible to trauma and when damaged bleed profusely
Where do the lymphatics of the GI tract tend to drain?
1) Lymph vessels follow the arteries back to lymph nodes that lie infront of the aorta (pre-aortic lymph nodes) around the origins of the celiac, superior mesenteric and inferior mesenteric arteries (have a group for each)
2) Inferior mesenteric -> superior mesenteric -> celiac -> cisterna chyli (thoracic duct drains into left subclavian vein)
What is the exception to the rule in the lymphatic drainage of the GI tract?
Although the major arterial supply to the rectum is from the superior rectal artery from the inferior mesenteric artery - the rectal lymph vessels also follows the middle rectal artery to drain into the internal iliac lymph nodes
Where would pain be referred to from the foregut, midgut and hindgut?
Foregut = epigastric region Midgut = umbilical region Hingut = suprapubic region
Why might abdominal malignant disease lead to enlargement of the supraclavicular nodes on the left side?
Malignant cells travel in the lymph system to the nodes in the left supraclavicular region (where the lymph ultimately drains to)
