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GI Week 3 > GI Development > Flashcards

GI Development Flashcards

1
Q

What germ layer gives rise to the epithelial lining of the digestive seystem and glands such as the pancreas, salivary glands, liver and submucosal glands of brunner?

A

Endoderm

EXCEPT the stomodeum and proctodeum which are lined by ectoderm

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2
Q

WHat germ tissues are responsible for the muscular wall of the GI tract?

A

Skeletal muscle of pharynx and upper esophagus is from branchial arch mesoderm (4th and 6th arches)

Smooth muscle and connective tissue is from splanchnic mesoderm

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3
Q

What germ tissues are responsible for the nervous component of the GI tract?

A

neural crest cells that migrate into the developing GI tract

(vagus innervates to the left colic flexure with remaining innervated by pelvic splanchnic nerves - parasympathetics at least)

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4
Q

What membrane bounds the cephalic end of the developing gut?

A

oropharyngeal membrane

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5
Q

What membrane bounds the caudal end of the developing gut?

A

cloacal membrane

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6
Q

What germ layers compose these membranes?

A

1

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7
Q

What three regions constitute the developing digestive tract?

A

the foregut, midgut and hindgut

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8
Q

What septum is responsible for the separation of the esopahgus and trachea?

A

tacheoesophageal septum

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9
Q

Why does polyhydramnios occur with esophageal stenosis and atresia?

A

the fetus can’t swallow and digest the amniotic fluid, so it builds up in the amniotic sac leading to polyhydramions

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10
Q

What is a tracheoesophageal fistula?

A

occur with incomplete separation of the trachea form the esophagus due to a defective tracheoesophageal septum

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11
Q

Why do all forms of tracheoesophageal fistulas lead to respiratory disease?

A

you either get food going down into the trachea or digestive enzymes going up into the trachea

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12
Q

What is responsible for pyloric stenosis?

A

hypertrophy of the circular lyaer of the stomach smooth muscle at the pyloric outlet, producing a narrowing of the pyloric canal

(bileless vomitus)

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13
Q

Why does duodenal (intestinal) atresia or stenosis occur?

A

Occurs due to failure of recanalization of the intestine such that the lumen is occluded by intestinal epithelial cells

(bile in vomitus)

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14
Q

What structures or parts of the digestive tract are associated with the foregut? Where does parasympathetic nerve supply come frrom? Blood?

A

pharynx, esophagus, stomach, upper duodenum, and glands of the pharyngeal pouches (thymus and parathyroid), thyroid, respiratoyr tract, liver and gallbladder, pancreas

parasympathetics form vagus

blood from celiac trunk

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15
Q

What structures or parts of the digestive tract are associated with the midgut? Where does parasympathetic nerve supply come frrom? Blood?

A

lower duodenum, jejunum, ileum cecum, appendix, ascending and right half of transverse colon

parasympathetics form vagus

blood from superior mesenteric artery

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16
Q

What structures or parts of the digestive tract are associated with the hindgut? Where does parasympathetic nerve supply come frrom? Blood?

A

left half of transverse colon, descending colon, sigmoid colo, rectum, superior part of anal canal

parasympathetics from pelvic splanchnics

blood from inferior mesenteric artery

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17
Q

How does the developing blood supply relate to the blood supply of the newobrn or adult?

A

1

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18
Q

What vascular anastomosis occurs in the area of the proctodeum?

A

1

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19
Q

WHat structures suspend the stomach from the dorsal and ventral walls respectively?

A

The dorsal mesenery suspends it from the dorsal wall and the ventral mesentery suspends it from the ventral wall

easy

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20
Q

What mesenteries of the stomach are related to the lesser and greater curvatures?

A

The ventral mesentery (lesser omentum) is related to the lesser curvature

the dorsal mesentery (greater omentum) is related to the greater curvature

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21
Q

What structure extends between the liver and the stomach/duodenum?

A

the lesser omentum

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22
Q

What are the two designated components of the lesser omentum?

A

hepatogastric and hepatouodenal ligaments

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23
Q

What two adult structures are derived form the ventral mesentery?

A

the lesser omentum and the falciform ligament

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24
Q

Why does the dorsal mesentery become located on the left and the ventral mesentery on the right?

A

a 90-degree rotation of the stomahc occurs to bring dorsal convex border (greater curvature) to the left and the ventral concave border (lesser curvature) to the right

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25
Q

What embryonic structure forms the greater omentum?

A

dorsal mesentery

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26
Q

What is the omental bursa and what accounts for its decrease in size?

A

it’s the area that forms behind the stomach after 90-degree rotation

It enlarges first as the dorsal emsentery grows to form the greater omentum, but then shrinks when it’s obliterated in the greater omentum

27
Q

What embryonic structure forms the gastrocolic ligament?

A

The dorsal mesentery (mesogastrium) and the transver mesocolon fuse to form the gastrocolic ligament that extends between the stomach and the transverse colon

28
Q

Where does the spleen develop and from what germ layer does it develop?

A

develops within the dorsal mesentery from mesodermal origin

29
Q

What germ layer is repsonsible for formation of hepatic cells?

A

Endoderm of the foregut

it grows into the ventral mesentery and mesenchyme of the transverse septum

30
Q

What developmental structures is reponsible for the CT component of the liver?

A

the transverse septum

31
Q

What developmental structure is responsible for the hepatic cells and the ducts draining the liver cells?

A

the hepatic diverticulum or liver bud

32
Q

What is the origin of the gallbladder and ventral pancreas?

A

endodermal hepatic diverticulum (why they’re so close to the liver)

33
Q

What is the significance of the liver in blood formation?

A

It serves as a site of hematopoietic tissue during emryonic and fetal development - occurs prior to splenic hemopoiesis

34
Q

What germ layer gives rise to the pancreatic ducts and pancreas?

A

Endoderm - forms ventral and dorsal pancreatic buds

35
Q

Where do the two pancreatic ducts develop?

A

1

36
Q

Why does the ventral pancrease become located in the dorsal wall and fused with the dorsal pancreas?

A

because it gets pulled along as the stomach and duodenum rotate to the right

37
Q

What usually occurs between the ventral and dorsal pancreatic ducts?

A

They fuse

38
Q

Based on the adult duct system, how can on remember that the ventral pancreatic duct usually becomes the main pancreatic duct?

A

The dorsal duct generally degenerates and the duct of the ventral pancreas becomes the definitive pancreatic ducts

we can remember this because the bile duct joins the main pancreatic duct and both the bile duct and the ventral pancreatic ducts develop from endoderm of the hepatic diverticulum

39
Q

How do the cells of the exocrine and endocrine pancreas develop?

A

Exocrine - acini develop from the terminal ends of the duct system

endocrine - budding cells off of the ducts give rise to them

40
Q

What is heteroptoic gastric mucosa and pancreatic tissue?

A

when gastric mucosa or pancreatis tissue develop at sites other than in the stomach or pancreas

41
Q

What structure gives rise to the ileal or Meckel diverticulum?

A

heterotopic pancreatic tissue

42
Q

What blood vessel supplies the midgut?

A

superior mesenteric - serves as the pivot point for the rotation

43
Q

How does the midgut rotate to bring the intestines into the adult position?

A

It herniates out and the cephalic limb of the midgut loop grows rapidly (to form small intestine) while caudal limb unergoes little change (large intestine)

then the midgut loop rotates 270 degrees counter-clockwise around the SMA with the caudal limb going around the cephalic limb to bring the colon across the small intestine

44
Q

During which weeks of development is the midgut herniated into the umbilical cord?

A

6th-7th it herniates out

10-11th it comes back in

45
Q

Why does the midgut herniate into the body stalk?

A

There isn’t enough room int he abdominal cavity for the rapidly rowing cephalic limb of the midgut

46
Q

What is responsible for the ileal or Meckel diverticulum?

A

remains of the omphaloenteric duct (yolk stalk)

47
Q

What is the clinical significance of a Meckel diverticulum?

A

The diverticulum can become inflamed, be a site for ectopic stomach or pancreatic tissue or contribute to a vovulus leading to ischemia or strangulation of the bowel

48
Q

What is a complex omphalocele?

A

Represents failure of the intestinal loops to return from the umbilical cord tot he abdominal cavity during the 10ths week and the ventral bdominal wall to close

49
Q

What normal developmental process took place but failed to be completed with a congenital omphalocele?

A

Physiologic herniation took place approrpiately, but reduction doesn’t take place

50
Q

What is a congenital umbilical hernia?

A

Occurs when the ventral abdominal musculature fails to close the umbilical ring

the protruding mass is covered by subcutaneous tissue ans skin

51
Q

How does a congenital umbilical hernia differ from an omphalocele?

A

WIth a hernia, the gut contents do return to the abdominal cavity, so they’re covered by skin instead of amnion

52
Q

What in the developing embryo is responsible for formation of the mesentery?

A

1

53
Q

Why are some structures retroperitoneal while other structures are suspended by a mesentery?

A

Dorsal mesentery fuse with the peritoneal lining of the dorsal body wall, causing the duodenum and ascending/descending colons to be retroperitoneal - it just fuses around them

54
Q

What is the most caudal portion of the hindgut?

A

the cloaca

55
Q

What structure separates the cloaca form the proctodeum?

A

the cloacal membrane - made of ectoderm and endoderm

56
Q

WHat is the purpose of the urorectal septum?

A

it grows and divides the cloaca into a urogenital sinus and a rectum/anal canal so the urogenital syste and the rectum is separate in humans

the perineal body forms the area where the urorectal septum approaches the cloacal membrane

57
Q

What two regions contribute to formation of the anal canal?

A

the upper two thirds is derived from hindgut

the lower one-third is derived from proctodeum

(separated by the pectinate or anorectal line(

58
Q

Why does the anal canal have a dual blood supply?

A

Because the arterial and venous systems for the two areas differ: hindgut is supplied by inferior mesenteric while proctodeum is supplied by the inferior rectal branch off the internal pudendal

59
Q

What is the clinical significance of that dual blood supply?

A

1

60
Q

Where do the lymphatics of the hindgut and proctodeum drain?

A

lymphatics from the hindgut drain to the inferior mesenteric nodes while the lymphatics in the proctodeum drain to the superficial inguinal nodes

61
Q

What is a congenital megacolon?

A

Hirschsprun’s diasease or aganglionic megacolon

you don’t get parasympathetic ganglia in the wall of the colon (usually distal colon) leading to a constriction and then proximal dilation

62
Q

What developmental defect is repsonsible for megacolon?

A

neural crest cells fail to migrate into the splanchnic mesoderm

63
Q

What accounts for an imperforated anus?

A

persistence of the cloacal membrane to atresia of the anal canal/rectum

64
Q

Why do hindgut fistulas occur and where do they occur?

A

Connection between the hingut with the vagina, urethra or bladder

they occur because of incomplete division of the cloaca by the urorectal septum into the rectum/anal canal and urogenital sinus

GI Week 3 (15 decks)

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