G.I organs

Question 1

Describe the abdominal oesophagus

Answer 1

Emerges through the right crus of the diaphragm at T10
Goes through the muscular part of the diaphragm which is important because it contributes to the formation of the Lower Oesophageal Sphincter which prevents gastro-oesophageal reflux
Passes from the oesophageal hiatus into the cardial orifice just left to the midline

Question 2

What are the relations of the abdominal oesophagus

Answer 2

Anterior vagal trunk- left vagus nerve- rotation of gut during development moves these fibres anteriorly
Posterior vagal trunk- single trunk- right vagus nerve

Question 3

Describe the arterial supply of the abdominal oesophagus

Answer 3

esophageal branches of the left gastric artery (celiac trunk)
esophageal branches from the left inferior phrenic artery (from the abdominal aorta)

Question 4

Describe the stomach

Answer 4

Most dilated part of G.I tract
J-shaped
Lies between abdominal oesophagus and S.I
Found in epigastric, umbilical and left hypochondriac regions

Question 5

Describe the different regions of the stomach

Answer 5

Fundus: superior to plane created by the cardial notch
Cardia: surrounds the opening
Body: bulk of the stomach, between the fundus and angular incisure
Pyloric antrum: between the pyloric canal and angular incisure
Pyloric canal: leads to the pyloric constriction where the pyloric sphincter controls flow to the duodenum

Question 6

Describe the other features of the stomach

Answer 6

Greater curvature: most lateral curvature; point of attachment of gastrosplenic ligament and greater omentum
Lesser curvature: most medial curvature; point of attachment of lesser omentum
Cardial notch: superior angle created where the oesophagus enters
Angular incisure: bend on the lesser curvature

Question 7

Describe the arterial supply to the stomach

Answer 7

Left gastric artery (celiac trunk)
Right gastric (hepatic artery proper)
Right gastro-omental artery (gastroduodenal artery)
Left gastro-omental (splenic artery)
Posterior gastric (splenic artery- variant)

Question 8

What is important to remember about the stomach

Answer 8

Clinical note – on chest x-rays be aware that you can often see a gas bubble in the fundus of the stomach lying directly beneath diaphragm. Do not confuse this air bubble with air in the peritoneum, say from an intestinal perforation.

Question 9

Describe the duodenum

Answer 9

Position: C-shaped structure adjacent to head of pancreas

Functional anatomy: lumen widest of small intestine, and all retroperitoneal apart from the first region

Above level of umbilicus
First part is attached to the liver via the hepatoduodenal ligament (part of lesser omentum)

Question 10

Describe the superior part of the duodenum

Answer 10

aka ampulla; extends from pyloric orifice to neck of gallbladder, passing anterior to the bile duct, portal vein and IVC (only intraperitoneal part)
Just right to the body of L1

Question 11

Describe the descending part of the duodenum

Answer 11

extends from neck of gallbladder to the lower border of vertebra LIII; crossed anteriorly by the transverse colon, and right kidney is posterior; contains the duodenal papillae
Major duodenal papilla: entrance of bile/pancreatic ducts
Minor duodenal papilla: entrance of accessory pancreatic duct (and junction of foregut/midgut)

Question 12

Describe the inferior part of the duodenum

Answer 12

longest section, crossing IVC, aorta and vertebral column

It is crossed anteriorly by the superior mesenteric artery and vein

Question 13

Describe the ascending part of the duodenum

Answer 13

passes upwards on the aorta to vertebra LII, terminating at the duodenojejunal flexure

Question 14

What is the duodenal flexure surrounded by

Answer 14

surrounded by fold of peritoneum (suspensory ligament of the duodenum)

Question 15

Describe the arterial supply to the duodenum

Answer 15

Branches from gastroduodenal artery

Branches from superior mesenteric artery

Question 16

Describe clinical implications of the duodenum

Answer 16

The relations of the duodenum are important clinically. Anurysms can compress the duodenum or ulcers can erode into the walls of vessels.
Most duodenal ulcers occur in the superior part (duodenal cap)

Question 17

Describe the position of the jejenum

Answer 17

proximal 2/5ths of the small intestine (mostly LUQ)

Question 18

Describe the position of the ileum

Answer 18

distal 3/5ths of the small intestine (mostly RLQ)

Question 19

Compart the jejunum to the ileum

Answer 19

Walls: jejunum has thicker walls with more frequent and prominent circular folds (plicae circulares)
Lumen: jejunum is larger in diameter
Arterial arcades: more prominent in the ileum
Vasa recta: longer in the jejunal supply
Mesenteric fat: larger in the ileum

Question 20

Describe the large intestine

Answer 20

extends from distal end of the ileum to the anus, absorbing fluids and salts to form faeces in gut

Question 21

Describe the caecum

Answer 21

Right groin- with associated appendix
In right iliac fossa inferior to the iliocaecal opening
Intraperitoneal- due to its mobility not due to suspension by mesentery
Continues with ascending colon at entrance of ileum
Usually in contact with anterior abdominal wall and may cross pelvic brim to enter true pelvis
Appendix attached to posteromedial wall just inferior to end of ileum

Question 22

Describe the colon

Answer 22

Ascending colon: continuation of the large intestine to the right colic flexure below the liver
Transverse colon: (intraperitoneal) crosses the abdomen to the left colic flexure below the spleen
Descending colon: passes to the left groin
Sigmoid colon: associated with the sigmoid mesocolon and joins to the rectum

Question 23

Describe the appendix

Answer 23

Point of attachment is consistent with the highly visible free taeniae leading directly to the base of the appendix, but the location of the rest of the appendix varies
Surface projection of base is at the junction of the lateral and middle one-third of a line from the ASIS to the umbilicus (McBurney’s point)
People with appendicular problems may describe pain near this junction

Question 24

Summarise the branches of the abdominal aorta that supply the G.I tract

Answer 24

3 UNPAIRED arteries arising from the anterior of the AORTA

COELIAC TRUNK = FOREGUT, liver, pancreas and spleen

SUPERIOR MESENTERIC ARTERY (SMA) = MIDGUT

INFERIOR MESENTERIC ARTERY (IMA) = HINDGUT

Question 25

Describe the features of the large intestine

Answer 25

Omental appendices: peritoneal-covered accumulations of fat associated with the colon Taeniae coli: segregation of longitudinal muscle into narrow bands Haustra of colon: sacculations of the colon

Question 26

Describe the coeliac trunk

Answer 26

Anterior branch of abdominal aorta Arises immediately below the aortic hiatus Anterior to upper part of L1 Immediately divides into left gastric, common hepatic and splenic arteries

Question 27

Describe the branches of the coeliac trunk

Answer 27

``` Common hepatic artery (medium): supplies the stomach, liver and duodenum (via the gastroduodenal artery) Left gastric artery: (small) supplies the stomach (both surfaces- anastomoses with left gastric artery) Splenic artery (large): supplies the spleen and branches to supply the pancreas ```

Question 28

Describe the superior mesenteric artery

Answer 28

Anterior branch of abdominal aorta supplying the midgut Arises immediately below the celiac artery anterior to the lower part of L1 Crosses anteriorly by the splenic vein and neck of pancreas Posterior to the artery are the left renal vein, uncincate process of pancreas and the inferior part of the duodenum Inferior pancreaticoduodenal artery is first branch it then gives off jejunal and ileal arteries on the left Right: middle colic, right colic and ileocolic arteries

Question 29

Describe the branches of the SMA

Answer 29

Middle colic artery: supplies the transverse colon Right colic artery: supplies the ascending colon Ileocolic artery: supplies ascending colon and distal ileum Ileal arteries: supply the ileum (longer vasa recta and more prominent arterial arcades) Jejunal arteries: supply the jejunum (shorter vasa recta and less prominent arterial arcades)

Question 30

Describe the inferior mesenteric artery

Answer 30

Anterior branch of abdominal aorta and supplies the hindgut Arises anterior to L3 Initially descends along aorta before moving to the left Branches include the left colic, several sigmoid and superior rectal artery

Question 31

Describe the branches of the IMA

Answer 31

Left colic artery: supplies the distal 1/3rd of the transverse colon and the descending colon ( ascends retroperitoneally, before dividing into ascending and descending branches) Sigmoid arteries: supply the sigmoid colon Superior rectal artery: supplies the rectum

Question 32

Describe the portal vein

Answer 32

The portal vein arises from the superior mesenteric and splenic veins posterior to the 1st part of the duodenum / pylorus of the stomach. It then runs in the free edge of the lesser omentum to the liver. It drains blood from all abdominal viscera and liver Does not drain blood from rectum however

Question 33

Describe the relations of the portal vein

Answer 33

Ascending towards the liver, it passes posterior to the superior duodenum and enters the right margin of the lesser omentum As it passes through this part of the lesser omentum, it is anterior to the omental foramen and posterior to the bile duct (its right) and hepatic artery proper (left)

Question 34

Describe the splenic vein

Answer 34

collects blood from the spleen, gastric veins, pancreatic veins and the inferior mesenteric vein

Question 35

Describe the superior mesenteric vein

Answer 35

collects blood from the small intestine, ascending colon and transverse colon

Question 36

Describe the inferior mesenteric vein

Answer 36

collects blood from the descending and sigmoid colon as well as the rectum, draining to the splenic vein

Question 37

Describe the porto-systemic anastomoses

Answer 37

The portal-systemic anastomoses are where veins draining to the portal vein and the IVC communicate. Liver or portal obstruction causes these veins to dilate widely, possibly leading to severe venous haemorrhage from oesophagus or rectum

Question 38

Describe some porto-systemic anastomoses

Answer 38

Gastroesophageal junction- around cardia of stomach- where left gastric vein and its tributaries anastamose with tributaries to the azygos veins of the caval system anus- superior rectal vein anastomoses with inferior rectal veins of systemic system anterior abdominal wall around umbilicus- para-umbilical veins anastamose with veins of anterior abdominal wall colic veins and posterior abdominal wall veins

Question 39

What happens when the pressure in the portal system is elevated

Answer 39

venous enlargement (varices) tend to occur at the sites of portosystemic anastomoses and are called: varicies at anorectal junction esophageal varicies at the gastrooesophageal junction caput medusae at the umbilicus susceptible to trauma and once damaged may bleed profusely

Question 40

Summarise the lympahtics

Answer 40

The lymphatic drainage of the bowel follows the arterial supply, not the venous drainage. All lymph drains into the cisterna chyli. Cisterna chyli is an elongated lymphatic sac located in front of the L1 & L2 bodies The thoracic duct commences from the cisterna chyli

Question 41

Describe the celiac trunk

Answer 41

Drains lymph from structures part of abdominal foregut Drains to pre-aortic lymph nodes near origin of celiac axis (celiac nodes) Also receive lymph from superior mesenteric and inferior mesenteric groups of pre-aortic lymph nodes where they all drain into cisterna chyli

Question 42

Describe the superior mesenteric lymph nodes

Answer 42

Also recives lymph from inferior mesenteric lymph nodes

Question 43

Summarise the innervation of the gut

Answer 43

Abdominal viscera supplied by AUTONOMIC nervous system. Sensory fibres most important Parasympathetic sensory (regulate reflex gut function): VAGUS NERVE PELVIC SPLANCHNIC NERVES (S2-S4) ``` Sympathetic sensory (mediate PAIN): THORACIC SPLANCHNIC (T5-T12) LUMBAR SPLANCHNIC (L1+L2) ```

Question 44

List the splanchnic nerves

Answer 44

``` Greater Splanchnic: T5-9 Lesser Splanchnic: T10-11 Least Splanchnic: T12 Lumbar Splanchnic: L1-2 Pelvic Splanchnic: S2-4 ```

Question 45

Describe the thoracic and lumbar splanchnic sympathetic fibres

Answer 45

Thoracic- three nerves pass from sympathetic ganglia in along sympathetic trunk in the thorax to the prevertebral plexus and ganglia associated with the abdominal aorta and abdomen Lumbar- two to four nerves from lumbar part of sympathetic trunk or ganglia

Question 46

Describe the sacral splanchnic nerves

Answer 46

Pass from sacral part of sympathetic trunk or associated ganglia and enter the inferior hypogastric plexus- an extension of the prevertebral plexus.

Question 47

Describe the pelvic splanchnic nerves

Answer 47

Carry pre-ganglionic PSNS fibres from anterior rami of S2-S4 and pass to the inferior hypogastric plexus, where some fibres pass upwards to the prevertebral plexus PSNS innervation of hindgut

Question 48

What does the abdominal prevertebral plexus receive

Answer 48

preganglionic PSNS and visceral afferents from vagus nerve preganglionic sympathetics and visceral afferent fibres of lumbar and thoracic splanchnic nerves preganglionic PSNS fibres from pelvic splanchnic nerves

Question 49

Describe the vagus nerves

Answer 49

After entering the abdomen as anterior and posterior vagal trunks- they send branches to the abdominal prevertebral plexus- which contain preganglionic PSNS fibres and visceral afferent fibres Provide PSNS innervation of foregut and midgut

Question 50

Describe the role of visceral afferent fibres in the gut

Answer 50

Innervation: the sensory fibres are most important. In the viscera: Sensory fibres running with the sympathetic (T1-L2) mediate pain and control of sphincters Sensory fibres running with the parasympathetic (vagus or sacral) are involved in reflex regulation of gut function peristalsis