Development of GI system Flashcards

1
Q

outer tube of flat trilaminar disk

A

ectoderm, covers outer surface of embryo (except umbilical region)

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2
Q

central tube of flat trilaminar disk

A

endodermal primary gut tube

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3
Q

middle tube of flat trilaminar disk

A

mesoderm

contains coelom or body cavity

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4
Q

How does the midgut remain in communication with the yolk sac?

A

vitelline duct

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5
Q

what forms the epithelial lining of GI tract and parenchyma of derivative glands

A

endoderm

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6
Q

what forms the smooth muscular components of the GI tract

A

splanchnic (visceral) mesoderm

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7
Q

cranially, foregut terminates in

A

buccopharyngeal membrane

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8
Q

caudally, hindgut terminates in

A

cloacal membrane

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9
Q

at the buccopharyngeal and cloacal membranes –> what fuses?

A

endoderm fuses w/ ectoderm excluding the mesoderm

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10
Q

double-layered connection between splanchnic mesoderm and somatic mesoderm

A

dorsal mesentery

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11
Q

organ completely covered by peritoneum (having a mesentery) is called

A

intraperitoneal

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12
Q

organ covered by peritoneum, only on anterior surface

A

retroperitoneal

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13
Q

ventral mesentery

A

liver develops between this

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14
Q

pharyngeal gut (or pharynx)

A

from buccopharyngeal membrane –> respiratory diverticulum

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15
Q

respiratory diverticulum

A

out pouching of upper part of foregut, first rudiment of lung

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16
Q

tracheoesophogeal septum

A

separates upper part of foregut into ventral trachea and dorsal esophagus

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17
Q

upper 2/3 of trachea n. supply

A

vagus n.

striated muscle

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18
Q

lower third of esophagus n. supply

A

autonomic n.

smooth muscle

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19
Q

lung bud appears from ventral surface of foregut when?

A

4th week of devel

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20
Q

bronchial buds –>

A

R main bronchi –> forms 3 secondary bronchi

L main bronchi –> forms 2 secondary bronchi

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21
Q

pulmonary agenesis

A

lung bud fails to split into R and L bronchi and continue growing (bronchial morphogenesis)

result: abnormal number of lobes/bronchial segments, complete absence of lung, abnormal number of alveoli

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22
Q

possible CXR findings for pulmonary angenesis

A

complete opacity of R hemithorax
displacement of heart and mediastinum
tracheal displacement to R

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23
Q

esophageal atresia

A

congenital malformation
failure of esophagus to develop continuous passage into stomach

infants exhibit choking, coughing, aspiration pneumonia

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24
Q

trachea-esophageal fistula

A

trachea and esophagus fail to separate into distinct structures, passage created between them

infants exhibit choking, coughing, aspiration pneumonia, cant pass catheter thru esophagus to stomach

often assoc w. other anomalies like ventricular septal defect/patent ductus arteriosus/tetralogy of fallout

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25
Q

stomach at 4th/5th weeks

A

stomach is a dilatation of foregut, rotates 90 degrees clockwise, vagus n. follows rotation

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26
Q

stomach at 7th and 8th weeks

A

rotate santeroposteriorly

caudal (pyloric end) moves up and to R

cranial (cardiac end) moves down and to L

overal, axis of stomach runs from above L to below R

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27
Q

what forms lesser sac/omental bursa

A

dorsal mesogastrium being pulled to L, forming space behind stomach

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28
Q

two ligaments next to spleen in dorsal mesogastrium

A
lienorenal ligament (splenicorenal ligament)
gastrolienal ligament (gastrosplenic ligament)
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29
Q

iliorenal ligament contains

A

splenic vessels

tail of pancreas

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30
Q

gastrolienal ligament contains

A

short gastric vessels

L gastroepiploic vessels

31
Q

congenital hypertrophic pyloric stenosis

A

thickening of pylorus

narrowing of pyloric canal and obstruction to passage of food

stomach –> markedly distended, infants expel food w/ nonbilious projectile vomiting

progressive loss of fluid, H, Cl –> metabolic alkalosis and dehydration

32
Q

bilious vomiting

A

obstruction distal to entrance of bile duct via ampulla of water (2nd pt of duodenum)

33
Q

nonbilious vomiting

A

obstruction proximal to entrance of bile duct

34
Q

duodenum develops from

A

caudal part of foregut and cranial end of midgut

35
Q

Error in which part of duodenum development can lead to duodenal stenosis or atresia

A

5th/6th week, lumen of duodenum becomes smaller and temporary obliterated bc of proliferation of epithelial cells

If no recanalization –> stenosis/atresia

36
Q

most duodenal atresia involve which parts of the duodenum?

which comorbidity these pts have 25% of time?

A

2nd/3rd part duodenum distal to opening of bile duct

results in bilious projectile vomiting

25% of cases have Down Syndrome

37
Q

duodenal atresia

A

complete occlusion of duodenal lumen

in infants, vomiting begins a few hours after birth, almost always CONTAINS BILE

prenatal ultrasound shows double-bubble sign

can lead to polyhydramnios

38
Q

double-bubble sign

A

prenatal ultrasound of pt w/ duodenal atresia

results from overfilled stomach and superior part of duodenum

39
Q

polyhydramnios

A

xs amniotic fluid bc fluid cant pass to stomach and intestines for absorption and transfer thru placenta to mother’s blood for disposal

can be due to duodenal atresia or esophageal atresia

sx: dyspnea, edema, abd distension, preterm labor

40
Q

oligohydramnios

A

deficiency of amniotic fluid

41
Q

liver bud

A

aka hepatic diverticulum

appears day 22 from caudal end of foregut (midway thru 2nd pt of duodenum)

penetrates septum transverse and divides ventral mesentery

connection w/ duodenum narrows to form hepatic bile duct

outgrowth of ventral wall of bile duct –> cystic duct and gallbladder

42
Q

hepatocytes are formed from which germ layer

A

endoderm

43
Q

connective tissue of liver gallbladder is derived from which germ layer

A

splanchnic mesoderm

44
Q

visceral peritoneum
hemopoietic cells
Kupffer cells (macrophages)

derived from?

A

mesoderm of septum transversum

45
Q

serial membrane of septum transverse becomes _____, which covers most of the surface of the liver except _____

A

serial membrane of septum transverse becomes VISCERAL PERITONEUM, which covers most of the surface of the liver except BARE AREA OF LIVER

46
Q

zone of reflection of visceral peritoneum becomes

A

coronary ligament

47
Q

remnant of ventral mesentery connecting liver to anterior wall becomes

A

falciform ligament

48
Q

liver divides ventral mesentery into 3 parts…

A

thin peritoneal lining

falciform ligament

lesser omentum

49
Q

extra hepatic biliary atresia

A

blockage of bile from liver to gall bladder

rare

due to failure of ducts to recanalize or liver infection during fetal development

jaundice occurs soon after birth

50
Q

ventral mesentery gives rise to

A

lesser omentum

falciform ligament

visceral peritoneum of liver

hepatogastric ligament

51
Q

uncinate process

A

of pancreas

hook-like

superior mesenteric a. and v. pass over this

52
Q

pancreas develops from 2 buds

A

dorsal bud of duodenum

ventral bud from origin of liver bud

53
Q

pancreas becomes _________ _________ as its mesentery fuses w/ the posterior abd wall

A

secondarily retroperitoneal

54
Q

annular pancreas

A

occurs when two lobes of ventral pancreas migrate around the duodenum in opposite directions to fuse w/ dorsal bud

infant sx: feeding intolerance, bilious vomiting, abd distension

adult sx: abd pain, nausea, vomiting, upper GI bleed (stomach ulceration), acute or chronic pancreatitis

55
Q

cephalic limb of primary intestinal loop forms

A

rest of duodenum
jejunum
part of ileum

56
Q

caudal limb of primary intestinal loop forms

A
rest of ileum
cecum
appendix
ascending colon
proximal 2/3 of transverse colon
57
Q

Physiological umbilical herniation

A

physiological herniation of the primary intestinal loop into the umbilicus due to continued midgut elongation and pressure from abdominal organ growth

week 6

58
Q

midgut rotation

A

week 6

herniated primary intestinal loop rotates 270 counterclockwise about its long axis while the jejunum and ileum form, creating jejunal-ileal loops

59
Q

midgut retraction

A

week 10

intestinal loops retract into the abd with the jejunum entering first, and the cecum (with its new vermiform appendix) entering last

60
Q

absent or incomplete secondary rotation of midgut can lead to

A

small intestine located on R side of abd cavity

61
Q

reversed secondary rotation of midgut

A

net rotation is 90 clockwise

viscera in normal location, but duodenum ANTERIOR to transverse colon –> can compress/obstruct colon

62
Q

subhepatic cecum/appendix

A

cecum initially lies below the liver then descends to the right iliac fossa

failure to descend –> sub hepatic cecum/appendix

63
Q

how do ascending and descending colons become secondarily retroperitoneal

A

they are pushed against posterior body wall causing fusion of their mesentery with the parietal peritoneum

64
Q

structures that were intraperitoneal that become secondarily retroperitoneal during development

A

duodenum
pancreas
ascending colon
descending colon

65
Q

midgut volvulus

A

malrotation of gut causes narrowed mesenteric line of attachment of midgut

ligament of treitz in abnormal position (lower, to R of midline)

small intestine loops can twist (corkscrew sign)

dilatation of proximal duodenum

66
Q

gut atresia and stenoses

commonly occur where?
as a result of what?

A

can occur anywhere along intestine
mostly duodenum
fewest in colon

caused by “vascular accidents” due to malrotation and volvulus

blood supply torsion is comprised, segment dies

67
Q

Meckel’s diverticulum

A

persistent vitelline duct (or yolk stalk)

small outpouching of ileum connected to umbilicus by fibrous cord fistula, cyst

98% cases: asymptomatic

can mimic appendicitis

sx: painless rectal bleeding, intestinal obstruction, volvulus, intussusception (collapsing in on itself)

68
Q

omphalocele

A

failure of umbilicus to close completely

hernial sac from epithelium of umbilical cord (peritoneum)

69
Q

ectopia cordis

A

failure of abd wall closure more superiorly, GI protrudes out

most cases –> death shortly after birth (infection, hypoxemia, cardiac failure)

70
Q

gastroschisis

A

abd wall does not involve umbilicus

incomplete closure of lateral folds during 4th week

GI system does not function properly - protrudes out

71
Q

congenital umbilical hernia

A

protrusion of intestines through IMPERFECTLY CLOSED umbilicus

hernia covered by subcutaneous tissue/skin

defect through linea alba, protrudes during crying/straining/coughing

~15-20% infants affected

72
Q

which part of pancreas is derived from ventral pancreatic bud?

A

part of head of pancreas and uncinate process

73
Q

smooth m. of GI tract is derived from

A

lateral plate somatic mesoderm

74
Q

rotation of primitive intestinal loop occurs in a _______ direction and amounts to approx _____ degrees

A

counterclockwise direction

270 degrees