GI Anatomy Flashcards
At what level does the gastro-oesophageal junction lie?
T10
Which part of the stomach is most superior and can become dilated with gas?
Fundus
The angular incisure marks the boundary between which two parts of the stomach?
Stomach body and the pyloric antrum
The stomach is an intraperitoneal organ. T/F?
True
What is the name of the folds of the stomach which flatten out to allow it to expand in volume?
Rugae
The left and right gastric arteries supply the stomach via anastamoses at the lesser curvature. What is the origin of these arteries?
The left gastric artery is a direct branch of the coeliac trunk
The right gastric artery comes from the common hepatic artery which also originates from the coeliac trunk
The anastomoses of the left and right gastro-epiploic arteries supply the stomach at the greater curvature. What is the origin of these arteries?
The left gastroepiploic artery comes from the splenic artery
The right gastroepiploic artery comes from the gastroduodenal artery
Lymph from the stomach drains into which nodes?
Coeliac nodes
What is the innervation of the stomach?
Parasympathetic innervation is 5rough the vagus nerve
Sympathetic innervation is through the splanchnic nerves (T6-T9)
Where does the duodenum lie in relation to the peritoneum?
The duodenum is retroperitoneal apart from the first 2.5cm which are intraperitoneal
Describe the blood supply to the duodenum
The first part of the duodenum until approximately the major duodenal papilla is supplied by the superior pancreticoduodenal artery which is a branch if the gastroduodenal artery
The remainder of the duodenum is supplied by the inferior pancreaticoduodenal artery which is a branch of the superior mesenteric artery
To which nodes does lymph from the duodenum drain?
Coeliac and superior mesenteric nodes
Describe the innervation of the duodenum
Sympathetic - greater and lesser splanchnic nerves
Parasympathetic - vagus nerve
What type of epithelium exists in the stomach?
Simple columnar epithelium
Describe the four layered microstructure of the GI tract.
Muscosa - epithelium, lamina propria, muscularis mucosae
Submucosa - larger blood and lymph vessels
Muscularis externa - innermost oblique muscle (only in stomach), inner circular muscle, outer longitudinal muscle
Serosa
The myenteric and submucosal plexuses combine to form the enteruc nervous system. Where do these plexuses lie?
The submucosal plexus lies within the submucosa
The myenteric plexus lies between the inner circular and outer longitudinal muscle layers in the muscularis externa
What type of epithelium exists in the oesophagus?
Stratified squamous epithelium
What is the name of the glands within the duodenum which secrete bicarbonate ions to neutralise acidic gastric secretions?
Brunner’s glands
Peyers patches exist in the small kntestine - what do these do?
They are lymphatic areas which protect against ingested pathogens
The lower oesophageal sphincter is merely a physiological sphincter, not an anatomical sphincter. What does these mean?
There is no thickening of the muscle but the sphincter still functions to close the opening between the oesophagus and cardia of the stomach
What is the greater omentum?
A large apron like fold of peritoneum which hangs from the greater curvature of the stomach and is mainly comprised of fatty tissue
What is the lesser omentum?
A small fold of peritoneum which exists between the liver and the stomach
The lesser sac allows the motility and expansion of the stomach. T/F?
True
What is the name of the foramen in the lesser omentum which provides a communication between the greater and lesser sac?
Epiploic foramen
What is the infracolic compartment?
The region of the greater sac which exists inferior to the transverse colon
What is the subphrenic space?
A potential space which sits between the right lobe of the liver and the inferior surface of the diaphragm
Which ligament divides the subphrenic space into a right and left half?
Falciform ligament
What is the name of the embryological remnant of the umbilical vein?
Ligamentum teres or round ligament of the liver
In terms of surface anatomy, where does the fundus of the gallbladder lie?
Where the latera edge of the recus abdominus (linea semilunaris) meets the costal margin
What features of the small intestine enhance its absorptive function?
The surface area of the small intestine is very large to help with absorption. This is achieved by:
Long length of intestine
Plicae circularis (permanent folds of the mucosa and submucosa)
Villi
Microvilli
What cells are contained in the crypts which exist between villi in the small intestine?
Enteroemdocrine cells
Paneth cells
Stem cells
What is the function of goblet cells in the small intestine?
Produce an alkaline mucous ti provide lubrication and protect the mucosa from digestive enzymes
What is the function of paneth cells in the small intestine?
Secrete lysozyme which acts as an antibacterial
The duodenum receives blood supply from the corliac trunk and the superior mesenteric artery. Where does this change in blood supply occur and why does this happen?
At the hepatopancreatic ampulla because this marks the division between the embryological foregut and midgut
What is the significance of the arterial arcades which supply the jejunum and ileum?
These ensure there is always an adequate supply of blood to these tissue despite the movement of these tissue
What are the four parts of the pancreas?
Head
Neck
Body
Tail
Where is the uncinate process of the pancreas?
It is a projection from the inferior part of the head and extends medially
The main pancreatic duct runs throughout the length of the pancreas and then drains to unite with which duct before entering the duodenum?
The common bile duct
What is the accessory pancreatic duct?
A duct which drains the uncinate process and inferior part of the head of the pancreas and drains into the duodenum and the minor duodenal papilla. This duct dies nit exist in all people however
What is the blood supply to the pancreas?
The splenic artery runs along the superior margin of the pancreas and supplies the neck, body and tail with its branches
The head of the pancreas is supplied by the inferior and superior pancreaticoduodenal arteries
Which vein drains the pancreas?
Splenic vein
Describe the venous drainage of the small intestine?
The duodenum drains into the hepatic portal vein and the jejenum and ileum drain to the superior mesenteric vein
What percentage of the overall mass of the pancreas do the endocrine islets of langerhans account for?
1-2%
List some of the hormones secreted by the islets of langerhans
Somatostatin
Insulin
Glucagon
Describe the structure of the exocrine part of the pancreas
This is arranged into lobes separated by fibrous tissue. Cells in these lobes are organised into clusters called acini which surround a central intercalated duct which drains to the main pancreatic duct.
There are both acinar cells and centroacinar cells. The centroacinar cells surround and create the duct.
What is the function of pancreatic acinar cells?
To secrete the pancreatic enzymes such as trypsinogen, chymotrypsinogen, lipase, pancreatic amylase,
What is the function of pancreatic centroacinar cells?
Secrete bicarbonate ions which act ti neutralise the acidic chyme in the duodenum and thus create an optimum pH for the digestive enzymes to work at
Between which structures does the root of the mesentery exist?
This connects the intestine to the posterior abdominal wall from the area of the duodenaljejunal flexure to the ileocoecal junction
The hepatic flexure is superior to the splenic flexure. T/F?
False the opposite is true
What is the function of the mesentery?
To support the intestines and to tether them to the abdominal wall whilst still allowing them tk be mobile stuctures
What three features of the large intestine distinguish it from the small intestine?
Haustrations
Taenia coli
Appendices epiploicae (fatty tags)
The base of what structures lies where the three bands of smooth muscle of the taenia coli of the large intestine converge?
Appendix
What artery supplies the ascending colon?
Right colic artery
What artery supplies the tranverse colon?
Middle colic artery
What is the function of the arterial arcades of the jejunal and ileal branches of the superior mesenteric artery?
To maintain blood supply despite the motility of the intestine
What is the name of the ‘turning point’ where the ascending colon becomes the transverse colon?
Right colic or hepatic flexure
What is the name of the ‘turning point’ where the transverse colon becomes the descending colon?
Left colic or splenic flexure
The transverse colon is U shaped in some people. T/F?
True
What shape is the sigmoid colon?
S shaped
What structures maintain continence in the anal canal?
External and internal anal sphincters
The large intestine contains villi. T/F?
False
The large intestine contains goblet cells which secrete mucous. What is the importance of this?
The mucous provides lubrication of the lumen of the large intestine which helps in the movement of faces through the colon, this is particularly important due to the large amount of water absorption that occurs in the large intestine and which therefore makes the faeces increasingly solid as they progress towards the rectum
Why is the large intestine supplied by the superior mesenteric artery until a point approximately 2/3 of the way along the transverse colon and then from this point supplied by the inferior mesenteric artery?
The proximal colon was formed by the midgut and the distal colon was formed by the hindgut
What branches of the superior mesenteric artery supply the ascending colon?
Ileocoecal arery and right colic artery
What branch of the superior mesenteric artery supplies the transverse colon?
Middle colic artery
What is the function of the marginal artery of drummond?
To provide an anastomoses between the branches of the superior and inferior mesenteric arteries
Which branch of the inferior mesenteric artery supplies the descending colon?
Left colic artery
What is the exact definition of the neck of the pancreas?
The neck of the pancreas exists just in front of where the portal vein is forming
Why can the globular structure of the pancreas be seen on dissection?
Because it has a thin capsule
Why is the splenic artery so torturous?
In order to decrease the pressure in the artery to prevent the pulsation of the spleen
The splenic artery gives off several branches to the pancreas. What is the name of the largest of these branches?
The artery pancreatica magna
What feature of the spleen is evidence of its embryological rings where it exists as several different parts before fusion?
The splenic notch
In relation to the pancreas, where does the inferior mesenteric vein lie?
Posterior to the pancreas
Which two veins combine to form the hepatic portal vein on the posterior surface of the pancreas?
The superior mesenteric vein and the splenic vein
What is the function of the red pulp of the spleen?
To act as a filtration system, removing from the circulation old red blood cells, other cellular debris, particulates and microorganisms
The central artery is contained within the red pulp of the spleen. T/F?
False - it is contained within the white pulp
Describe the closed circulation theory of the spleen
Blood cells escape the venous sinusoids into the splenic cords and here are filtered by the spleen, with healthy cells being returned to the venous sinuses and being drained from here into the splenic veins
Describe the open circulation theory of the spleen
In this theory, venous sinuses in the spleen are thought to be blind-ended and blood is thought to flow from the central artery directly into the splenic cords where it is filtered. From here, healthy cells then flow into the venous sinuses and are drained into the splenic veins
