Digestive System / Peritoneal Membranes

Question 1

What does the endoderm give rise to?

exceptions?

Answer 1

all of the Epithelium and all of the glands except the mouth and anal canal.

Question 2

What does the mesoderm give rise to?

Answer 2

splanchnic mesoderm

smooth muscle + connective tissue

Question 3

What do the neural crest cells give rise to?

Answer 3

autonomic ganglion

Question 4

What does the ectoderm give rise to?

Answer 4

mouth (1st arch portion) and anal canal

Question 5

What is the separation point for the foregut/midgut/hindgut?

Answer 5

wherever the yolk sac is attaching.

Question 6

Midgut portions?

Answer 6

small intestine (past the major papilla), cecum, appendix, ascending colon, right half of the transverse colon.

Question 7

Foregut portion?

Answer 7

pharynx, respiratory system.

esophagus, stomach, liver/pancreas, biliary apparatus, proximal duodenum

the boundary changes just distal to the major duodenal papilla

Question 8

Hindgut portions?

Answer 8

Left half of the transverse colon, descending colon, sigmoid colon, rectum, superior anal canal, and the urinary bladder/urethra

Question 9

Foregut artery is supplied by what artery?

midgut?

hindgut?

Answer 9

celiac trunk

Superior Mesenteric artery (sma)

Inferior Mesenteric Artery (ima)

Question 10

Where does the smooth muscle of the esophagus coming from?

skeletal muscle from the esophagus comes from where?

Answer 10

splanchnic mesoderm

mesoderm or pharyngeal arches 4/6

Question 11

Tracheoesophageal Fistula (TE)

esophageal atresia?

Answer 11

happens at week 5 (failure of tracheoesophageal septum to fold correctly)

abnormal passage between tracheal and esophagus.

blind end esophagus

Question 12

What does TE fistula present with?

Answer 12

frothy saliva, not able to swallow it.

polyhydramnios (too much fluid).

we’ll send down a NG tube and if it coils, TE fistula

Question 13

Explain the stomach development?

What about the vagus nerves? (mnemonic)

Answer 13

happens week 4

the dorsal surface is going to grow larger and have an out pocketing. We then have rotation along the longitudinal axis, and then an AP rotation as well.

Left Vagus is now anterior, right vagus is now posterior after the rotations. (LARP)

Question 14

What is hypertrophic pyloric stenosis?

what do they present with?

what plane would you see this at? what would it feel like?

Answer 14

circular muscles around the pyloric sphincters hypertrophy. It’s a knot at the pylorus of the stomach

immediately after feeding so the baby has nonbilous and forceful vomiting

as it progresses there are fewer and fewer stools. lose weight or failure to gain weight.

could feel an olive like mass at L1.

Question 15

How is the liver and biliary system formed?

when is bile formed?

hematopoeisis?

Answer 15

all is coming from a single hepatic diverticulum (gives rise to liver, gallbladder, and pancreatic bud)

the liver continues to grow superiorly to the septum transversum (becomes the diaphragm), to fuse to it.

gallbladder splits off and fuses to the liver.

the stalk of the diverticulum is the bile duct.

produced by the 12th week

starts 6 to week 30

Question 16

Stroma and coupler cells (of the liver) (cells that migrated in) come from where?

hepatocytes of the liver, the cells of the organs that are doing its functional business?

Answer 16

mesoderm

endoderm

Question 17

How is the pancreas formed?

what forms the body and tail and part of head?

what forms the rest of the head and the uncinate process?

what forms the main pancreatic duct (ventral duct) (part that opens to the duodenum)

Answer 17

you have a ventral pancreatic bud (that came from the hepatic diverticulum) gets a rotation and it fuses with the dorsal pancreatic bud. this is where we get our pancreas being formed.

dorsal primordia

ventral primordial

also part of the ventral primordia

Question 18

What is an annular pancreas?

how do they present?

if this annular pancreas was above or below the bile duct, what would you expect?

Answer 18

causes obstruction to the duodenum

the ventral pancreatic bud is bifed and it rotates in the wrong direction, which fuses it to the dorsal in the wrong area, forming a ring in the second part of the duodenum.

2/3 of patients are asymptomatic.. (not a tight right)

if it was tight, it would be similar to pyloric stenosis except the vomit is sometimes billous (depends on if its above or below the bile duct region.

bile or not in the vomit

Question 19

spleen: where does it come from? why is it different?

what week is it formed?

what does it do and what weeks is it?

Answer 19

foregut but it doesn’t come from endoderm, it comes from mesoderm!

most organs are endoderm

forms during week 5

9-28, helps with hematopoiesis.

Question 20

how does the midgut rotate? (long answer)

what is the axis, how does it start

what is rotating and going underneath stuff

what ends up behind what

when does this happen and when does it come back in.

what is the total degree of rotation

Answer 20

we have this U shaped structure

the superior mesenteric artery is the axis and is herniating out into the umbilical cord.

the midgut loop makes a quarter turn counterclockwise, the distal part develops a bulge that becomes the cecum and the proximal loop becomes convoluted (small intestine)

(the cranial part becomes the small intestine
the caudal part becomes the large intestine)

proximal part passes under the distal part.

the distal part returns last and ends over to the right.

(the proximal part of the midgut ends up behind the distal midgut - which is the duodenum being behind the transverse colon)

it herniates out (at week 6) into the umbilical cord and rotates 90 degrees. it comes back in at week 10 and does another 180 degrees turns (one for the small, one for the large intestine), totaling 270 degree rotation.

Question 21

What is a Omphalocele? when does it happen?

what is covering it (2 things)

Answer 21

failure of the bowel to return to the body cavity

week 10.. it’s a membrane covering the guts.. because it went out to the umbilical cord. so it’s covered with peritoneum and ectoderm (amnion) covers the sac.

Question 22

What is Gastroschisis?

what week does this happen?

Answer 22

failure of body wall to close.

we do not have a sac covering the guts. Week 4. problem with the anterior abdominal wall on the right side.

they’re trapped outside of the body wall

Question 23

Umbilical hernias are not what? why?

Answer 23

Omphalocele

everything returns where it should, but the umbilicus is just a weak spot so later it can herneate back out, but that’s to do with increased abdominal pressure, not embryological.

Question 24

What is Hirschsprung Disease?

Answer 24

megacolon

most common cause of neonatal obstruction

***problem with neural crest cells because there’s absence of ganglion c ells (aganglionosis).. ENS still present, but no ganglion there to help

there’s no parasympathetics where the ganglion are missing so the sympathetics take over = constriction

the part that’s filled with feces (before it) is normal, but the distal part is so narrow that you get a big part of the

Question 25

Congenital inguinal hernia happens with direct or indirect?

Answer 25

indirect. it goes through the inguinal canal

Question 26

What other midgut rotations are possible? symptoms?

Answer 26

non rotation.. the small intestine is on the right side and the small intestine is on the left side. some people are asymptomatic, but the flexures now are super tight so you can get obstruction easier. reverse rotation = it rotates in the wrong direction. The transverse colon is now posterior to the duodenum (instead of the opposite), so the duodenum can cause an obstruction in the transverse colon.

Question 27

How does the gut lumen form? what could happen if done incorrectly? (2 things)

Answer 27

hollow tube + endodermal proliferation then recanalization through apoptosis then we have the completed lumen. you could have a duplication where it creates a side pouch and food can accumulate and it can fill and rupture through the wall. we could also get a stenosis where apoptosis didn't occur correctly and we have a narrowing in the canal.

Question 28

What is Meckel's Diverticulum? what structure is it associated with? what boards mnemonic do we use?

Answer 28

abnormality of the vitelline duct (normally regresses) that is attached to the umbilicus and pulls the ileum it pulls on the ileum and creates a pouch. so the ileum is projected to the abdominal wall. can lead to intestinal obstruction, GI bleeding, bowel sepsis. Rule of 2's. 2% pop, 2 feet from ileocecal junction, 2 inches long, 2 types of ectopic tissue, 2 year olds present, effects males 2x as often.

Question 29

What is an omphalomesenteric fistula? '' cyst? '' ligament?

Answer 29

extreme meckels pretty much. You have feces dribbling out of your umbilicus. the vitelline duct persisted and didn't close. not a problem, we see them post mortum. fibrous band that connected the ileum to the umbilicus, but didn't cause meckels.

Question 30

Urorectal septum does what? what are the two divisions. what do these two things become? what is it made of? what is missing and why? what does the urorectal septum become? and what is it made of?

Answer 30

grows towards the cloacal membrane and divides it... to anal membrane and urogenital membrane urogenital membrane --> forms bladder and urethra anal membrane --> anus both of those are ectoderm and endoderm.. no mesoderm because we want it to rupture. the urorectal septum is mesoderm. perineal body

Question 31

What does the hindgut give rise to for the anal canal? (above pectinate line) what is the blood vessels? nerve supply? lymphatics? what does the lower portion coming from? blood vessels? nerve supply? lymphatics?

Answer 31

upper 2/3. (superior to the pectinate line) IMA autonomics Inferior mesenteric lymph nodes from ectoderm (proctodeum) lower 1/3. middle + inferior rectal A. Pudendal N. (somatic N so voluntary control).. you can feel pain in this region! superficial inguinal lymph nodes

Question 32

What needs to happen for the anorectal region to happen correctly? (2 things) ex) anal stenosis? covered anus? recto-urethral fistula? rectal atresia

Answer 32

endoderm and proctodeum ectoderm must meet at the right place otherwise you won't have a good opening. urorectal septum needs to migrate correctly and separate the cloaca. ectoderm is narrow but otherwise OK. problem with ectoderm. septum doesn't go so you have stuff mixing hindgut didn't migrate as far as it should have.

Question 33

what happens to separate the cardial cavity and the peritoneal region? (4 structures help) pretty much how is the heart, abdomen, and lungs separated from each other?

Answer 33

pericardial cavity (for the heart), 2 pleural cavities (for the lungs), and one peritoneal cavity (abdomen). pleuropericardial membrane separates the heart from lungs pleuroperitoneal membrane (somatic layer of lateral plate mesoderm) fuses with septum transversum and creates the abdominal cavity.

Question 34

How is the diaphragm formed?

Answer 34

Septum transversum doesn't migrate all the way to the posterior body wall. We need the pleuroperitoneal membranes from the somatic layer of the lateral plate... they grow towards the septum transversum and fuse. after that tissue is pulled from body wall and that gives rise to the rest of the diaphragm.

Question 35

What things do we see on the diaphragm in lab? 2 things what are they coming from?

Answer 35

(central tendon) - from Septum transversum (right and left crus) - coming from dorsal mesentary of esophagus

Question 36

Congenital Diaphragmatic Hernia? what is it called? where does it usually happen? what do kids present with?

Answer 36

defective fusion of the pleuroperitoneal membranes Foramen of Bachtalect 85-90% on the left side. abdominal contents go up into the thorax. polyhydramnios, hypo plastic lungs.

Question 37

Mesentary of the peritoneal cavity is what?

Answer 37

double layer of splanchnic mesoderm (serous membrane) (allow blood vessels and nerves to get to the organs. comes around the gut tube and comes back around

Question 38

What is the dorsal mesocardium? what mesenteries are in the abdominal cavity and liver? what does each give rise to? midgut and hindgut mesenteries? (4 of them)

Answer 38

degenerates leaving the transverse pericardial sinus dorsal mesogastrium (dorsal mesentery but attached to the stomach so this is what its called)--> gives rise to the greater omentum.. this attaches to the posterior wall the ventral mesogastrium create the lesser omentum the falciform ligament comes from the ventral mesentary too mesoduodenum --> mesentary around duodenum mesentary proper - mesentary containing the jejunum and ileum mesocolon - mesentary around the transverse colon and sigmoid colon mesorectum - mesentary around the rectum

Question 39

What are the different segments of the dorsalmesogastrium? ventralmesogastrium? ventral mesogastrium and ventral mesentary? remember.. the dorsal mesentary is subdivided into dorsal mesogastrium and ventral mesogastrium, the ventral mesentary doesn't split.

Answer 39

splenorenal ligament (ligament from spleen and kidney) gastrolienal ligament (gastrosplenic --> from stomach to spleen) -greater omentum Ventral mesogastrium = lesser omentum ventral mesentary - falciform ligament.

Question 40

What happens to the greater omentum? how many layers are there? what is the omental bursa?

Answer 40

as the stomach is doing its longitudinal rotation it pulls the dorsal mesentary over and over until you have this Long dorsal mesentary that's going to the stomach. this thing fuses forming the greater omentum. it's a fusion of 2 double layers, 4 layers in total of splanchnic mesoderm. omental bursa (lesser sac) is a space between the stomach and the posterior body wall

Question 41

some structures are completely surrounded in mesentary, but some of them will attach to the posterior body wall and become retroperitoneal. which ones will do this? these are called secondary retroperitoneal actually because some of the parts are still itnraperitoneal

Answer 41

STARTED in the mesentary but then fused, didn't start out in the posterior body wall like the kidneys (mesogastrium dorsal to spleen) Pancreas (except for the tail) (mesoduodenum) duodenum (2-4 parts) ascending + descending colon

Question 42

After rotation of the stomach, what happens to the ventral border, dorsal border, left and right side? AFTER THE FIRST TURN

Answer 42

becomes right becomes left ventral dorsal

Question 43

why does the midgut jut out into the umbilical cord, why can't it do it where it's at?

Answer 43

the liver and kidney are huge and there is no room

Question 44

what is mesentary? (2 ways of thinking about it) what about the parietal layer of the peritoneum? visceral layer?

Answer 44

double layer of serous membrane OR a double layer of the splanchnic mesoderm! comes from somatic layer of the lateral plate it attaches the organs and going around them. THAT'S A MESENTARY!

Question 45

What's the difference between dorsal and ventral mesenteries? important to know about ventral?

Answer 45

dorsal attaches to the posterior body wall ventral attaches to the anterior wall (most degenerate!! with the exception of foregut)

Question 46

What parts of the gut are intraperitoneal? retroperitoneal?

Answer 46

``` stomach tail of the pancreas first part of duodenum jejunum, ileum, transverse colon sigmoid colon ``` pancreas (exception tail) duodenum (2-4) ascending/descending colon