Exam 2 Flashcards
- Describe how the three primary germ layers contribute to the formation of the GI tract.
- Endoderm creates the lining of the primitive gut tube and mesoderm becomes the visceral and parietal peritoneum
- Describe the role of the embryonic body in folding in the formation of the primitive gut.
- Lateral folding contributes to folding the midgut tube and the cloacal/caudal folding contributes to forming the foregut and hindgut.
- List the three divisions of the gut tube and describe the cranial and caudal boundaries of each division. List the arterial supply of each division.
- Foregut: Everything that is supplied by the celiac trunk. The cranial boundary is the oropharyngeal membrane and the caudal boundary is just below the liver primordium (in the adult it is the major papilla of the duodenum)
Midgut: Everything that is supplied by SMA. The cranial boundary is just below the liver primordium and the caudal boundary will extend to the end of the proximal 2/3 of the transverse colon
Hindgut: Everything that is supplied by the IMA. The cranial boundary is the distal 1/3 of the transverse colon down to the cloacal membrane.
- Define peritoneum and mesentery. Define intraperitoneal and retroperitoneal.
- Peritoneum is a serous membrane that lines the walls of abdominal cavity. A mesentery is a double fold of peritoneum. Intraperitoneal is an organ that is connected to the posterior wall by a mesentery, retroperitoneal is when an organ lies against the posterior wall and is not connected via a mesentery.
- Describe the dorsal mesentery and list the divisions of this mesentery.
- The dorsal mesentery is an embryonic mesentery made from visceral mesoderm that extends from the lower end of the esophagus to the cloacal region of the hindgut.
a. Divisions: Dorsal mesogastrium (greater omentum), mesoduodenum (in the region of the duodenum), dorsal mesocolon (mesentery in region of colon), mesentery proper (connects to jejunum and ileum)
- Describe the ventral mesentery and the structures that arise from the ventral mesentery.
- The ventral mesentery is derived from the septum transversum.
a. Structures arising from it: Falciform ligament and lesser omentum of the liver and central tendon of the diaphragm.
- List the derivatives of the foregut.
- The derivatives of the foregut are the biliary apparatus, esophagus, trachea, stomach, pancreas, duodenum, lungs, liver
a. Describe the role that the respiratory diverticulum plays in dividing the foregut into the respiratory primordium and the esophagus.
a. The respiratory diverticulum is a blunt end pouch. This diverticulum grows cloacally and as it does, tracheoesophageal ridges form. These ridges eventually grow larger and fuse with one another forming the tracheoesophageal septum separating the trachea from the esophagus.
b. Describe the process of stomach growth and rotation. How does stomach rotation affect the final positioning the left and right vagus nerves?
b. The stomach begins growth by rotating 90 degrees clockwise. As a result of this the previous left side is now anterior and the previous right side is now posterior (leading to the right and left vagus nerves innervating the posterior and anterior of the stomach respectively). After this rotation the new left side grows faster than the new right side and as a result we get a greater and lesser curvature of the stomach. Finally the cardia will grow inferior and slightly to the left as the pylorus grows superior and to the right.
- Describe how stomach rotation leads to the formation of the omental bursa (lesser peritoneal sac).
- As the stomach rotates it pulls the dorsal mesogastrium with it, resulting in the dorsal mesogastrium looping around behind the stomach. The space that is created between the dorsal mesogastrium and the stomach is known as the omental bursa.
- Describe the formation of the spleen.
- The spleen primordium begins as a mesodermal proliferation between the two peritoneal layers of the dorsal mesogastrium. As the dorsal mesogastrium swings dorsally and fuses with the posterior wall the spleen swings to the left of the body. The spleen now remaining intraperitoneal is connected to the posterior near the kidneys by the lienorenal ligament and to the stomach by the gastrolieneal ligament.
- Describe the formation of the greater omentum.
Stomach rotation pushes part of the dorsal mesogastrium toward the anterior of the body. As this mesogastrium grows it grows inferior in front of the forming intestines. This loop of mesentery fuses and becomes 4 fused layers of peritoneum.
- Describe the formation of the duodenum. Discuss the rotation process that occurs such that the duodenum reaches its final position.
- The duodenum is formed from the terminal end of the foregut and the cephalic end of the hindgut. As the stomach rotates it also rotates the duodenum. As the pancreas rapidly grows It pushed the duodenum to the right creating the C shape. Both these structures then push against the posterior wall to become retroperitoneal.
- Describe the formation of the liver, gallbladder, and bile ducts.
- The liver begins to grow off of the duodenum as a liver bud (primordium). This bud begins to grow faster and penetrates the septum transversum (bare area). The connection between the liver and duodenum begins to narrow which forms the common bile duct. Ventrally off of this bile duct grows the gallbladder and cystic duct.
- Describe the formation of the pancreas. Discuss the rotation of the ventral bud. What portions of the pancreas are formed by the dorsal bud? What portions are formed by the ventral bud?
- The pancreas begins two separate buds (ventral and dorsal) the ventral bud during stomach rotation swings dorsally and fuses with the dorsal bud. The ventral bud creates the uncinate process of the head and the dorsal creates the head proper, neck, body, and tail.
- Define the main pancreatic duct (of Wirsung) and the accessory pancreatic duct (of Santorini). Describe their development in terms of the contributions of the dorsal and ventral pancreatic buds.
- The main pancreatic duct of Wirsung is made up of the duct from the uncinate process and the distal portion of the dorsal duct. This duct drains into the major papilla. The accessory duct (of Santorini) is formed by the proximal duct of the dorsal bud and empties into the minor papilla.
- Describe the boundaries of the midgut in the adult.
- The boundaries of the midgut in the adult is just distal the major papilla all the way through the proximal 2/3 the transverse colon.
- Discuss the formation of the primary intestinal loop. What structures arise from the cephalic limb? What structures arise from the caudal limb?
- The primary intestinal loop is a projection of the embryonic intestine that was forced out of the abdominal cavity into the extraembryonic cavity due to rapid liver growth. This loop is composed of a cephalic and caudal limb. The cephalic limb is responsible for the distal of the duodenum, jejunum, and most of the ileum. The caudal limb is responsible for forming the lower part of the ileum, the cecum, ascending colon, hepatic flexure, and proximal 2/3 of transverse colon.
- Describe the process of midgut rotation. What structure serves as the axis of rotation for this process?
- Midgut rotation occurs around SMA. Upon physiological umbilical herniation the intestines rotate 90 degrees in a counterclockwise manner. As they are pulled back into the abdominal cavity they rotate another 180 degrees to give a total of 270 degrees of rotation.
- Describe the process of physiological umbilical herniation. When does it occur?
- This is the outpouching of the intestines into the extraembryonic cavity during the sixth week.
- Describe the three vitelline duct abnormalities discussed in class: Meckel diverticulum, vitelline cyst, and vitelline fistula.
- Meckels diverticulum is when the vitelline duct persists as an outpouching of the ileum. The vitelline cyst is when both ends of the duct form fibrous cords and the middle part of the duct persists. The vitelline fistula is when the vitelline remains patent over the entire length and doesn’t close off to the outside.
- Describe the mesenteries of the midgut.
- The mesenteries of the midgut are the mesentery proper (small intestine) and the transverse mesocolon.
- List the derivatives of the hindgut.
- The hindgut creates the rest of the transverse colon, descending colon, sigmoid colon, rectum, upper anal canal.
- Describe the role of that the urorectal septum plays in separating the urinary tract from the GI tract.
- The urorectal septum separates the cloacal membrane into two separate membranes, the urogenital and the anal.
- Describe the difference in derivation of the superior 2/3 of the anal canal versus the inferior 1/3. What is the pectinate line? `
- The superior 2/3 of the anal canal is created from endoderm and the inferior is created from ectoderm. These two are delineated by the pectinate line (columnar to stratified squamous)
- What are the superior and inferior borders of the abdominal cavity?
The superior border is the diaphragm and the inferior border is the pelvic inlet.
- What are the planes that define the four quadrants of the abdominal cavity?
- Medan plane vertically and the transumbilical plane horizontally
- What are the planes that define the nine regions of the abdominal cavity?
- Vertically the midclavicular lines and horizontally the subcostal line and the intertubercular plane.
- Name the nine layers of the anteriolateral wall from superficial to deep.
- Skin→Camper’s fascia →scarpa’s fascia→External oblique→internal oblique→transverse abdominis→transversalis fascia→extraperitoneal fat→peritoneum (muscles separated by investing layers of deep fascia)
- What are the three muscle layers of the abdominal wall? Where is their aponeurotic attachment and in what orientation do they run?
- External oblique (runs anterioinferiorly), internal oblique (runs anteriosuperiorly), and transverse abdominis (runs medially). Their aponeurotic attachment is at the linea alba.
- What does the rectus sheath cover? How does its structure change as you move superior and inferior of the arcuate line?
- The rectus sheath covers the rectus abdominis. Superior to the arcuate line the external oblique and half of the internal oblique run superficial to rectus abdominis and the other half of internal oblique with and transverse abdominis run deep to rectus abdominis. Inferior to this line all muscles run superficial to the rectus abdominis and the transversalis fascia and peritoneum run deep.
- What are the two layers that are always deep to the rectus abdominus?
- Transversalis fascia and peritoneum.
- What does the median umbilical fold cover and what are the connection points? What is this a remnant of?
- The median umbilical fold covers the obliterated urachus which is a remnant of the allantois. This fold runs from the bladder to the umbilicus.
- \What does the medial umbilical fold cover?
- The medial umbilical fold covers the medial umbilical ligament which is the obliterated umbilical artery.
- What does the lateral umbilical fold cover?
- The lateral umbilical fold covers the inferior epigastric vessels.
- Where are superficial vessels found?
- The superficial vessels are found running through camper’s fascia.
- What artery supplies the inguinal ligament? What is this artery a branch of?
- The artery that supplies the inguinal ligament is the superficial circumflex iliac artery. This is a branch of the femoral artery.
- What artery supplies the superficial abdomen inferior to the umbilicus? What is this artery a branch of?
- The superficial epigastric vessels which are a branch of the femoral artery.
- What supplies the inferior lateral abdominal muscles? What is this a branch of and what two muscle layers does this run between?
- The inferior lateral abdominis muscles are supplied by the deep circumflex arteries which are a branch of the external iliac artery. It runs between the internal oblique and transverse abdominis.
- What vessels supply the lower rectus abdominis muscles, what are they a branch of, where do they enter the rectus sheath, and with what do they anastomoses?
- The lower rectus abdominis muscles are supplied by the inferior epigastric artery. This is a branch of the external iliac and enter the rectus sheath at the arcuate line. They anastomose with the superior epigastric arteries.
- What vessels supply the upper rectus abdominis, what is it a branch of, and where does it enter?
- The upper rectus abdominis is supplied by the superior epigastric muscles which are a branch off of the internal thoracic. The superior epigastrics enter just lateral to the sternum.
- What vessels supply the upper abdominal muscles and diaphragm? What are they a branch of? What do they run along?
- The upper abdominal muscles and diaphragm are supplied by the musculophrenic vessels. They are a branch of the internal thoracic and run along the costal cartilage.
- Nerves of what vertebral levels supply the abdominal wall? Describe which nerves supply which regions.
- Nerves of T7-L1 supply the abdominal wall. T7-T9 supply above the umbilicus, T10 is umbilicus, and T11-L1 supply below umbilicus. These nerves run between internal oblique and transverse abdominis.
- Injury to what region causes hernias?
- Injury to T11-L1 causes hernias.
- At what vertebral level can the arcuate line be found?
- The arcuate line can be found around cutaneous innervation level of T12.
- Where can the inguinal region be found?
- The inguinal region is found superior the thigh, median to ilium, and lateral to the pubic bone.
- Where is the superficial inguinal canal ring?
- Inguinal ligament, inguinal canal, superficial and deep rings, wall of canal
- Where is the deep ring?
- The superficial inguinal ring is a triangular ring found in the external oblique.
- Where can an indirect hernia be found?
- The deep ring is an opening in the transversalis fascia.
- Where can a direct hernia be found?
- An indirect hernia can be found running through the entire inguinal canal (in the deep ring and out the superficial ring). This one can enter the scrotum or labia majora.
- What is the name for organs that lie behind the peritoneum called?
- A direct hernia is busts through the conjoint tendon and can be found at or near the superficial ring.
a. Within the peritoneum?
- Organs that lay behind the peritoneum are called retroperitoneal. Ones that lie within the peritoneum are intraperitoneal.
- What do two peritoneal layers coming together make?
- Two peritoneal layers that come together make a mesentery.
- What are the functions of the greater omentum? What is it made of? Where does it attach?
- The greater omentum serves to wall off infections and inflammation sites. It is made of 4 peritoneal layers (or two fused dorsal mesogastrium layers) and attaches to the greater curvature of the stomach and the transverse colon.
- Where does the lesser omentum attach? What are the two ligaments that attach the lesser omentum to the liver? Which contains the portal triad and what is it?
- The lesser omentum attaches to the liver, duodenum, and lesser curvature of the stomach. The two ligaments are the hepatoduodenal and hepatogastric ligament. The hepatoduodenal ligament contains the portal triad (portal vein, hepatic artery, bile duct).
- What anchors most of the small intestine?
- The mesentery proper anchors most of the small intestine.
a. What two junctions does it run between?
It runs between the ileocecal and duodenojejunal junctions.
- What is the duodenum anchored by?
- The duodenum is anchored by the suspensory ligament of Trietz at the duodenojejunal junction.
- What parts of the colon are anchored by a mesocolon?
- The transverse colon and the sigmoid colon are both anchored by their respective mesocolon (which means these lie intraperitoneal and the other portions lie retroperitoneal).
- How does the transverse mesocolon divide the abdominal cavity?
- The transverse colon divides the abdomen into infracolic and supracolic (above and below the colon).
- When do peritoneal pouches become relevant?
- They become relevant when you are in a recumbent position.
- What is the pouch that is found in the pelvis of the male?
- The pouch that is found on the male is the rectovesicle pouch.
- What are the two pouches found in the pelvis of a female?
- The two pouches on the woman are the vesico-uterine pouch and the rectouterine pouch. (don’t forget about the pouch of Morrison (hepatorenal pouch))
- Describe the following surfaces on the liver:
a. Diaphragmatic
b. Visceral
c. Right
d. Left (what tendon separates R and L?)
e. Caudate
f. Quadrate
g. What does the porta hepatis functionally allow?
a. The diaphragmatic surface is the surface that contacts the diaphragm.
b. The visceral surface is the one that faces the organs inferior the liver
c. The right lobe is to the right and is the larger lobe (forces many organs on the right side of the body to be more inferior than their counterparts i.e. the kidneys)
d. The left lobe is left. These lobes are separated by the falciform ligament.
e. Caudate is on the right lobe and is superior the quadrate.
f. Quadrate is also on the right lobe and is inferior to the caudate.
g. Porta hepatis functionally allows for the filtration of blood by the liver.
- What does the round ligament contain?
a. Where is it located?
- The round ligament contains the obliterated umbilical vessels.
a. It is located at the inferior region of the falciform ligament anteriorly.
- What divides the liver into the R and L lobes?
a. What does this ligament anchor the liver to?
- The falciform ligament divides the liver into the right and left lobes.
a. Anchors the liver to the anterior wall.
- What ligament surrounds the bare area of the liver and where can the bare area be found?
a. What does this ligament attach the liver to?
- Coronary ligament surrounds the bare area of the liver
a. This ligament attaches the liver to the inferior region of the diaphragm.
- What are the three regions of the gallbladder?
a. How much bile does it store and what artery supplies this organ?
b. What is the duct system that leads to and from the gallbladder?
- Furthest from the cystic duct is the fundus, then body, then neck closest to the cystic duct.
a. 750 mL/day; supplied by the cystic artery from the hepatic proper.
b. Leading from the liver is the hepatic duct, and from the gallbladder is the cystic duct. These combine to form the common bile duct.
- What are the regions of the pancreas?
a. how does this organ lay relative to the peritoneum?
b. What organs surround it?
c. Where and what does the main duct enter?
d. The accessory duct?
- The head (made up of the uncinate process and the head proper), the neck, body, and tail.
a. This organ lays retroperitoneally.
b. It is surrounded by the duodenum, spleen, stomach
c. The main duct enters at the major papilla in the duodenum
d. The accessory duct enters at the minor papilla.
- What does the spleen contact and where?
a. What connects it to the greater curvature of the stomach?
i. What does this connection contain?
b. What connects it to the kidney?
i. What does this connection contain?
c. What is an entry point for the splenic vessels?
d. What is the arterial supply?
- The spleen contacts the diaphragm, the pancreas, and the stomach.
a. It is connected to the greater curvature of the stomach by the gastrosplenic ligament.
i. Contains the left gastro-epiploic vessels.
b. It is connected to the kidney by the splenorenal ligament.
i. Contains the splenic vessels.
c. The entry point for the vessels is the hilum of the spleen.
d. The arterial supply is the splenic artery which is a main branch of the celiac trunk.
- What arteries distribute to the 12th rib?
a. From where do they arise?
- The subcostal arteries distribute to the twelfth ribs
a. arise from the thoracic trunk.
- Where does the upper abdominal supply begin?
- The upper abdominal supply begins at the aortic hiatus T-12 (with the inferior phrenic arteries).
- What bifurcation ends this supply and where?
- The bifurcation of the aorta into the common iliac arteries ends this supply.
- What does the common iliac divide into?
- The common iliac artery divides into the internal and external iliacs.
- What is the first major branch of the aorta?
- The celiac trunk.
- What does it branch into?
- Celiac trunk branches into the common hepatic artery, left gastric artery, and the splenic artery.
What is the order of the digestive tract beginning with the esophagus?
- The digestive tract order is esophagus →stomach →duodenum → jejunum → ileum → cecum → ascending → hepatic flexure → transverse colon → splenic flexure → descending colon → sigmoid colon