Lower Gastrointestinal Tract Flashcards
What do you find in the mesentery of the small intestine?
Nerves, blood vessels and lymphatics.
What do you call the permanent folds in the jejunoileum?
Plicae circulares.
What are the strips of longitudinal muscle in the wall of the colon called?
Teniae coli.
What are the outward bulges of the colon called?
Haustra.
Name the four regions of the colon.
Ascending, transverse, descending, sigmoid.
What does “uncinate” mean?
Hook-like.
What do you call the “arches” of arteries in the mesentery?
Arcades
Where does the superior mesenteric artery arise?
From the aorta, just below the coeliac artery.
Where does the superior mesenteric artery run?
Downwards behind the splenic vein, and in front of the left renal vein, then over the uncinate process of the pancreas and part 3 of the duodenum.
What branches does the superior mesenteric artery give off?
Branches to the pancreas and duodenum, then branches to the mesentery of the jejunoileum, then branches down and to the right in the retroperitoneum (ileocolic towards caecum, right colic to ascending colon), then a branch upwards into the transverse mesocolon (middle colic to transverse colon).
Where does the inferior mesenteric artery arise?
Below the pancreas and duodenum at the level L3.
What are the branches of the inferior mesenteric artery?
The left colic artery (supplies distal 1/3 of transverse colon, and descending colon), sigmoid branches (supply sigmoid colon), and superior rectal artery (supplies upper part of rectum - lower parts of rectum supplied by internal iliac artery).
Which two arteries anastomose to form an arcade in the transverse mesocolon?
Middle colic and left colic arteries.
What do the veins in the GI tract anastomose to form instead of joining the inferior vena cava, and where do they join?
The hepatic portal vein, formed behind the pancreas.
What level is the aortic bifurcation at?
L4.
Where does the hepatic portal vein take blood from and to?
Blood from the GI tract, spleen and pancreas, to the liver.
What veins form the portal vein?
Superior and inferior mesenteric veins, and the splenic vein.
What is different about the foregut from the midgut and hindgut during development of the embryo?
The foregut is attached the the abdominal wall by a double fold of peritoneum and the front and at the back (dorsal mesogastrium, and ventral mesogastrium), this allows the momentum to develop when the foregut rotates on its long axis. The midgut and hindgut are only attached to the abdominal wall by a double fold of peritoneum at the back.
Where does the attachment of the ventral mesogastrium end up after rotation of the foregut?
Along the lesser curvature, having swung round to the right.
Where does the attachment of the dorsal mesogastrium end up after rotation of the foregut?
Along the greater curvature, having swung round to the left.
What develops in the ventral mesogastrium?
The liver.
What develops in the dorsal mesogastrium?
The spleen.
What is the opening called that leads into the lesser sac (omental bursa)?
Epiploic foramen (foramen of Winslow).
In the embryo, what is the midgut continuous with?
The Vitelline duct (yolk stalk), which is later obliterated.
Which artery runs up into the rectus sheath past the arcuate line to supply the rectus abdomens muscles?
Inferior epigastric artery.
What happens at the tip of the 9th costal cartilage?
The external oblique muscles, internal oblique muscles, and transverses abdomens muscles become aponeurotic.
Where is the transpyloric plane?
Along the line drawn between the tips of the 9th costal cartilages.
It is half way between the suprasternal notch and the pubic symphysis.
It is at vertebral level L1.
What’s the name of the curved line on the lateral aspect of the six-pack where the muscles become aponeurotic?
Linea semilunaris.
Where does the linea semilunaris meet the costal margin?
At the tip of the ninth costal cartilage.
Which two muscles form the conjoint tendon, which goes from the roof of the inguinal canal toward the pubic symphysis?
The internal oblique, and transverses abdominis.
What forms the roof of the inguinal canal?
Arching fibres of internal oblique and transversus abdominis muscles as they pass from inguinal ligament to form conjoint tendon.
What forms the floor of the inguinal canal?
The inguinal ligament and lacunar ligament.
What forms the posterior wall of the inguinal canal?
The transversalis fascia, reinforced medially by conjoint tendon.
What forms the anterior wall of the inguinal canal?
The aponeurosis of transversus abdominis, reinforced laterally by lower fibres of internal oblique.
What is contained in the inguinal canal?
The spermatic cord in men, the round ligament of the uterus in women, nerves, lymph and blood vessels.
Where is the deep ring of the inguinal canal?
At the start of the evagination of the transversalis fascia with the spermatic cord. Immediately lateral to inferior epigastric artery.
Where is the superficial ring of the inguinal canal?
The beginning of the tubular evagination of aponeurosis of external oblique, just above pubic tubercle.
Name the part of the enteric nervous system on the outside of the submucosa in the intestine.
Meissner plexus (submucosal plexus).
Name the part of the enteric nervous system on the ouside of the circular muscle layer in the intestine.
Auerbach plexus (myenteric plexus)
Name the 5 differences between the jejunum and ileum.
Jejunum has thicker wall.
Jejunum has more prominent plicae circulares.
Jejunum has large diameter (3cm).
Jejunum has big windows in mesentery (fewer artery arcades, longer vasa recta).
Jejunum is primary site for absorption.
Name the pale patches of lymphoid tissue in the submucosa of the ileum.
Peyer’s patches.
Name the three most distinguishing features between the small and large intestine.
Large intestine has: taeniae coli, appendices epiploicae, haustra coli.
(Also has plicae semilunaris inside.)
Name the two flexures of the large intestine.
Hepatic flexure (right colic flexure), and splenic flexure (left colic flexure).
What is the mesoappendix?
The short mesentery of the appendix arising from behind the terminal ileum.
What is the appendicular artery a branch of?
The ileocolic artery, which is a branch of the right colic artery, which is a branch of the superior mesenteric artery.
Name the distinguishing features of the anal canal.
Internal sphincter - smooth circular muscle.
External sphincter - deep, superficial, and subcutaneous skeletal muscle.
Anorectal junction.
Pectinate line, below anal columns, anal sinuses, and anal valves.
Anocutaneous line (white).
What is steatorrhoea?
The excretion of abnormal quantities of fat with the faeces owing to reduced absorption of fat by the intestine.
At which vertebral level is the posterior superior iliac spine?
S2.
Where is the transtubercular plane?
Across the iliac tubercles, at vertebral level L5.
Where is the interspinous plane?
Across the anterior superior iliac spines.
Which 4 planes divide the abdomen into its 9 quadrants?
2 mid-clavicular lines, transpyloric plane, transtubercular plane.
Which layer of fascia is Camper’s?
More superficial, fatty layer.
Which layer of fascia is Scarpa’s?
Deep, membranous layer.
Name the four muscles of the anterolateral abdominal wall, in the order most superficial to most deep.
External oblique, internal oblique, transversus abdominis (transversalis fascia).
Rectus abdominis is surrounded by aponeurosis of internal oblique above arcuate line, and is behind the aponeurosis of transversalis fascia below arcuate line (at the level of the anterior superior iliac spine).
Muscles form aponeurosis at tip of ninth costal cartilage.
Where is motilin secreted, and what is its function?
Motilin is secreted from M cells in the small intestine, it increases the migrating motility complex (regular wave activity happening in cycles, to increase peristalsis).
What is the Duct of Wirsung?
Pancreatic duct.
Where are bile salts mostly reabsorbed?
Terminal ileum.
What is an acinus in the liver?
Oval area between two central veins with the branches of the portal triad at the centre.
What is a lobule in the liver?
Hexagon with central vein in the middle and portal triad in three corners.
How many taeniae coli are there on the large intestine, and where do they converge?
Three, they converge at the base of the vermiform appendix.
And appendages epiploicae, and haustra, and plicae semilunaris.
What are the folds inside the large intestine called?
Plicae semilunaris.
Where is the muscularis mucosae in the wall of the small intestine?
Between the lamina propria and the submucosa.
What structures does the transpyloric plane (L1) pass through?
Tip of 9th costal cartilage, fundus of gallbladder, linea semilunaris where it crosses the costal margin, pylorus of stomach, duodenojejunal flexure, neck of pancreas, hila of kidneys, hilum of spleen, origin of superior mesenteric artery, origin of portal vein, end of the spinal cord.
What technique is used to bimanually palpate the kidney?
Balloting.
What do goblet cells store, which then becomes mucus?
Mucin.
Where do you find paneth cells, and what do they do?
Botton of the crypts of Lieberkuhn. They secrete peptidases and have antimicrobial properties.
Which drugs would be used to treat nausea and vomiting caused by chemotherapy?
5-HT3 receptor antagonists like ondansetron (blocks receptors in CTZ and gut).
Where is alanine aminotransferase produced, and what does it mean if it’s detected in the blood?
Produced in hepatocytes, and present in the blood if the hepatocytes are damaged e.g cirrhosis.
What is the duodenum the principle site for in fat digestion?
Emulsification of fats with bile.
What is the jejunum the principle site for in fat digestion?
Absorption of 2-monoacylglycerol, and fatty acids.
What is the ileum the principle site for absorption of?
Bile salts and vitamin B12.
What are the white horizontal lines on the anterior surface of rectus abdominis called?
Tendinous intersections.
Which vessels enter the rectus sheath between the arcuate line and the muscles?
Inferior epigastric vessels.
What are the grooves running down the lateral sides of the peritoneal cavity called?
Paracolic gutters.
Which muscle lies between the mylohyoid muscle and the intrinsic muscles of the tongue?
The geniohyoid.
What are the grooves on the anterior surface of the epiglottis called?
Valleculae.
Since the ascending and descending colon are retroperitoneal, name the two mesocolon of the large intestine.
Transverse mesocolon, sigmoid mesocolon.
What is the bend at the anorectal junction called, where the anteroinferiorly pointing rectum becomes the posteroinferiorly pointing anal canal?
Perineal flexure.
Which abdominal regions does the liver occupy?
Right hypochondrium and epigastrium.
What is the round ligament of the liver called (at the bottom of the falciform ligament) and what is it a remnant of?
Ligamentum teres, a remnant of the obliterated umbilical vein.
What is another name for the lesser omentum (which contains the portal triad)?
Hepatoduodenal ligament.
Name the two sets of ligaments on the diaphragmatic surface of the liver.
Right and left, anterior and posterior coronary ligaments.
Right and left triangular ligaments.
Name the area of the liver between the coronary ligaments that is devoid of peritoneal covering, why is it important in cancer?
The bare area. There are lymphatic vessels here that pass directly from the liver through the diaphragm and into the thorax, giving a potential route for the spread of metastatic cancer.
Name the two recesses either side of the liver.
Subphrenic (suprahepatic) recess, and the hepatorenal recess (pouch of Morrison).
Name the ligament between the quadrate lobe and left lobe of the liver.
Ligamentum teres.
Name the ligament between the caudate lobe and the left lobe of the liver.
Ligamentum venosum (a remnant of the ductus venosus)
What are the surface markings of the liver?
The upper margin is almost level with the xiphisternal joint.
The left side reaches the fifth costal cartilage.
The right border is between the seventh and eleventh ribs in the mid-axillary line.
The inferior border is roughly level with the costal margin on the right side.
The fundus of the gallbladder is at the tip of the 9th costal cartilage.
Name the borders of the kidneys.
Medial and lateral borders, and superior and inferior poles.
Name the muscle of the posterior abdominal wall that the ureters pass over.
Psoas major.
What vertebral level are the kidneys at?
T12 to L3.
Under 12th and 11th rib.
Where are the suprarenal glands in relation to the kidneys?
Superior to the right kidney and medial to the left kidney.
What vertebral level is the coeliac trunk at?
L1.
What vertebral level is the superior mesenteric artery at?
L1.
What vertebral level is the inferior mesenteric artery at?
L3.
What are the branches of the superior mesenteric artery?
MRI - middle colic, right colic, ileocolic.
What are the branches of the inferior mesenteric artery?
Left colic, sigmoidal, superior rectal.
Name the three ligaments making up the greater omentum.
Gastrophrenic, gastrosplenic, gastrocolic.
Name the specialised multipolar sympathetic neurones in the enteric nervous system.
Dogiel cells.
What is innervated by the myenteric (Auerbach) plexus?
The circular and longitudinal muscle, so it is mostly responsible for the movements of peristalsis.
What is innervated by the submucosal (Meissner) plexus?
The epithelium and muscularis mucosae.
Where do the plexuses of the enteric nervous system arise?
Around the superior mesenteric artery.
Since PPIs are irreversible inhibitors of the proton pump, why must they be taken everyday?
The stomach lining is constantly replaces (including the parietal cells) because of its battering by gastric juice and motility.
What is misoprostol?
A prostaglandins receptor agonist that is also used in the termination of pregnancy.
What are domperidone and metoclopramide?
Dopamine receptor antagonists used to treat nausea and vomiting caused by the chemotherapy and radiotherapy used to treat neoplasms. They have the side effect of muscle spasms.
What is ondansetron?
A 5-HT3 receptor antagonist used to treat nausea and vomiting caused by chemotherapy. A side effect is QT elongation which can cause fatal arrhythmia, so it is contraindicated in patients with atrial fibrillation.
What type of vomiting do H1 receptor antagonists target?
Motion sickness and morning sickness (e.g that arising in the vestibular nuclei).
What are the 6 layers of the wall of the small intestine?
Mucosa - ciliated simple columnar epithelium, lamina propria
Muscularis mucosae
Submucosa (submucosal/Meissner plexus)
Muscularis externa - circular, myenteric/Auerbach plexus, longitudinal
Subserosa
Serosa - visceral peritoneum
Which parts of the small intestine are peritoneal and which are retroperitoneal?
Duodenum = retroperitoneal
Ileum + jejunum = peritoneal
How much of the jejunoileum is jejunum?
Proximal 2/5
Which of the jejunum and ileum has a thicker wall?
Jejunum - more prominent plica circularis, larger diameter
How are the arcades in the mesentery (vasa recta and arteries) different for the jejunum and ileum?
Jejunum - longer vasa recta, less complex arteries (bigger windows)
Ileum - more arterial arcades and shorter vasa recta (smaller windows)
In which regions is the jejunum found?
Umbilical and left iliac fossa
In which regions is the ileum found?
Hypogastric and right iliac fossa
Which part of the small intestine has patches of lymphoid tissue in the submucosa and what are they called?
Ileum - Peyer’s patches
Where oaths Meckel’s diverticulum, how many people have it, and how long is it?
In 2% of people there is a Meckel’s diverticulum, that is 2 feet away from the ileocaecal junction, and 2 inches long.
How long is the vermiform appendix?
6-9cm
What are the 3 transverse folds of the rectum called, and where are they?
Houston’s valves.
The superior and inferior are on the left, the middle is on the right.
The rectal ampulla is below the folds.
What happens to the taeniae coil when the sigmoid colon becomes the rectum?
They become a continuous layer of longitudinal muscle again.
What is the anal canal?
The last 4cm of the gastro intestinal tract.
What are the anal sphincters?
Internal (smooth circular muscle) sphincter.
External (skeletal muscle) deep, superficial and subcutaneous sphincters.
What are the three features of the anorectal junction?
Anal columns, anal sinuses, anal valves
What is the line below the anorectal junction called, where origin changes from endoderm to ectoderm?
Pectinate line
What is the line below the pectinate line called?
Anocutaneous line (white line)
Which ribs does the spleen lie under on the mid-axillary line?
9, 10, 11
What type of abdominal organs are the kidneys?
Retroperitoneal
What is the mnemonic for organs that are retroperitoneal?
SAD PUCKER Suprarenal glands Aorta and inferior vena cava Duodenum (except D4) Pancreas (except tail) Ureters Colon (ascending and descending only) Kidneys Esophagus Rectum
What type of gut motility in the small intestine moves chyme around and mixes it with digestive enzymes?
Segmentation
Which type of gut motility moves chyme along the tube?
Migrating motility complex
What governs segmentation and migrating motility complex?
Myenteric (Auerbach) plexus
What is the gastroileal reflex?
After a meal, the intensified peristalsis in the small intestine opens the ileocaecal valve wider and pushes chyme into the caecum.
What effect does gastrin have on the ileocaecal sphincter?
Relaxes the ileocaecal sphincter.
What effect does the caecum becoming distended with chyme have on the ileocaecal sphincter?
Contracts the ileocaecal sphincter.
What is the gastrocolic reflex?
Mass peristalsis being stimulated and driving content into the rectum.
What is haustral churning?
Chyme being moved from one haustra to another.
