abdominal cavity I- embryology

Question 1

ectoderm

Answer 1

forms integument (skin) and nervous system (dorsal hollow nerve and chord, eventually spinal cord and all nerves and the lining of the anus (proctodeum) and mouth (stomodeum)

Question 2

Mesoderm

Answer 2

forms muscles, muscular walls of gut tube and most of connective tissues including bones

Question 3

endoderm

Answer 3

the lining of the gut and most gut derived organs

Question 4

yolk sac

Answer 4

sac attached to the primitive endodermal gut tube connected to the yolk sac via the omphaloenteric duct or yolk stalk

Question 5

why is the developing fetus not effected by alcohol in the first four weeks of development?

Answer 5

because it is getting all of its nutrients from the yolk sac that is attached to the primitive endoderm via the yolk stalk or omphaloenteric duct (future umbilical cord)
ie: the baby is not attached to the mom’s body yet

Question 6

what does the yolk sack do?

Answer 6

• gives nutrients
• forms endoderm that forms the respiratory tract and the gut tubes
• germ cells and yolk stalk gives rise to the gonads
• blood develops here until liver is fxnl

Question 7

Foregut
what is it?
arterial supply?
gives rise to?

Answer 7

-an embryonic gut division
-area includes stomodeum (primitive mouth) to first 1/3 of duodenum
-oropharyngeal membrane separates the stomodeum from the foregut
arterial supply- celiac trunk
-gives rise to-pharyngeal pouches

Question 8

midgut
what is it?
arterial supply?
gives rise to?

Answer 8

what is it?-the lower 2/3 of duodenum to the upper 2/3 of the colon
arterial supply? superior mesenteric
gives rise to? the yolk stalk

Question 9

hindgut
what is it?
arterial supply?
gives rise to?

Answer 9

what is it? last 1/3 of the colon to the proctodeum
arterial supply? inferior mesenteric a
gives rise to? gives rise to the alanosis

Question 10

recanalization

what is it and what are errors called?

Answer 10

• hollowing out the primitive gut tube
• atresia- no opening
• stenosis-narrowing of gut tube

Question 11

what’s a mesentery?

Answer 11

• a double layer of peritoneum (mesoderm) formed by splanchnic mesoderm that connects organs to the body wall
• aka form fibrous sheets around organs
• 2 types- parietal peritoneum and visceral peritoneum

Question 12

in a developing embryo what becomes of the ventral mesentery?

Answer 12

-ventral- disintegrates and turns into the
A) falciform ligament (liver to ventral body wall) -therefore attached
B) coronary ligament- (liver to diaphragm) -therefore attached
c) lesser omentum (liver to stomach to duodenum) -just covered

Question 13

in a developing embryo what becomes of the dorsal mesentery?

Answer 13

-Dorsal- proliferates and covers most of our organs

Question 14

what is the difference between the parietal and visceral mesentary

Answer 14

parietal- around the body cavity

visceral -around the viscera (organs)

Question 15

intraperitoneal, primary retroperitoneal, secondary retroperitoneal

Answer 15

• intraperitoneal- organ suspended in mesentery (within the peritoneal cavity)-always-stomach, spleen and transverse colon
• primary retroperitoneal- always in the retroperitoneal space- esophagus and rectum)
• secondary retroperitoneal- organs developed in the mesentery (in the peritoneum) but due to rotation during development now are behind the mesenary in the retroperitoneal space- (distal 2/3 of duodenum and asc/dec colon)

Question 16

what are these organs- primary retroperitoneal, secondary retroperitoneal or intraperitoneal:
spleen 
distal 2/3 of duodenum
aorta and vena cava
pancreas
colon-asc and dec
transverse colon
kidneys
stomach
esophagus
rectum
gall baldder and bile duct

Answer 16

• spleen- intraperitoneal
  -distal 2/3 of duodenum: secondary peritoneum
• aorta and vena cava- primary peritoneum
  -pancreas-secondary
  -colon-asc and dec-secondary
  -transverse colon-intraperitoneal
  -kidneys-primary
  -stomach- intraperitoneal
  -esophagus- primary
  -rectum-primary
  gall bladder and bile duct-intra

Question 17

what organs are included in the foregut

Answer 17

pharnx
esophagus
stomach
proximal 1/3 of duodenum

Question 18

what outpockets are developed from the foregut

Answer 18

pharyngeal pouches, lower respiratory system, liver, pancreas and gallbladder

Question 19

how is the esophagus formed and what are 2 potential problems?

Answer 19

• the esophagus is formed by one tube that the trachea also forms from.
• they are separated by the tracheoesophageal fold
• probs-
• > atresia of esophagus causes no food to pass thru esophagus
• > fistula opening between the esophagus and trachea where consumed food actually goes to lungs

Question 20

How can you tell a baby has an esophageal atresia?

Answer 20

POLYHYDRAMIOS

• when babies are developing they pee via the alanosis to form amniotic fluid
• to prevent overfilling of sac, babies drink their own pee
• if there is an atresia, there is an increased amount of amniotic fluid

Question 21

what causes the greater and lesser curvatures of the stomach?

Answer 21

the dorsal border of the stomach growing faster than the ventral portion of the stomach
dorsal =greater curvature
ventral =lesser

Question 22

how does the stomach rotate during development and where do the lesser and greater curvatures end up because of this?

Answer 22

• turns 90 degrees
• lesser curvature (ventral side) moves to right
• greater curvature (dorsal)- left

Question 23

where does the right vagus go on the stomach? left?

Answer 23

• Right vagus- greater curvature (dorsal surface)

- Left vagus- lesser curvature (ventral surface)

Question 24

what is formed by ventral outgrowths of the duodenum

Answer 24

liver, pancreas and gall bladder (makes sense since they have contents that empty into it)

Question 25

how is the pancreas formed and what is a potential problem?

Answer 25

• the pancreas is formed by ONE ventral and ONE dorsal bud
• the ventral bud rotates 90 degrees and fuses onto the dorsal bud to create the pancreas
• prob: if there are two ventral buds that move and wrap around the intestines causing strangulation- called annular pancreas

Question 26

what is unique about the spleen

Answer 26

it is one of the only organs created by the mesoderm, not the endoderm

Question 27

parts of the small intestine

Answer 27

duodenum, jujunum, ilium

Question 28

what is the central “spindle” around which the intestines spin during development? what direction do they twist?

Answer 28

• the superior mesenteric artery

- counterclockwise

Question 29

how do secondary retroperitoneal organs come to be?

Answer 29

-due to rotations that press organs against the posterior body wall and cause fusion of the mesentaries

Question 30

volvulus

Answer 30

-when an intestine wraps around itself and causes a blockage in the intestine

Question 31

hernia sac

Answer 31

where mesenteries get tangled and cause a hernia

Question 32

cloaca

Answer 32

-“common sewer”- hole where all waste leaves the hindgut

Question 33

urorectal septum

Answer 33

divides alantosis and yolk stalk and divides the cloaca into urogenital membrane and anal membrane

Question 34

anal membrane

Answer 34

separates caudal hindgut from proctodeum (anus)

Question 35

what is the innervation below and above the pectinate line of the rectum

Answer 35

above: hindgut (endoderm)
below: abdominal wall (ectoderm)

Question 36

anoperineal fistula

Answer 36

where anal tube comes out where not supposed to (ie not where the anal pit)

Question 37

non-perforate anus (persistent anal membrane)

Answer 37

no hole where poop can exit

Question 38

rectourethral fistula

Answer 38

fistula between urethra and rectum causing poop to exit penis

Question 39

rectovaginal fistula

Answer 39

fistula between vagina and rectum causing poop to exit vagina