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GI Week 3 - WLB > Normal & Abnormal Development of GI System - Severson > Flashcards

Normal & Abnormal Development of GI System - Severson Flashcards

1
Q

What germ layer gives rise to the epithelial lining and glands of the digestive system?

A
  • Lining + glands → ENDODERM
  • Stomodeum (mouth) + proctodeum(anus) → lined by ectoderm
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2
Q

What germ tissues are responsible for the muscular wall and nervous component, respectively?

A
  • Muscular wall → splanchnic mesoderm
  • Nervous component → neural crest cells
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3
Q

What membranes bound the cephalic and caudal ends, respectively, of the developing gut?

A
  • Cephalic → oropharyngeal membrane
  • Caudal → cloacal membrane
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4
Q

What may be responsible for the occurrence of duodenal (intestinal) stenosis or atresia?

A

failure of recanalization of intestine (usually duodenum)

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5
Q

Why does polyhydramnios occur with esophageal stenosis and atresia?

A

failure of amniotic fluid swallowing and absorption in utero

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6
Q

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

A

tracheoesophageal septum

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7
Q

What is a tracheoesophageal fistula?

A

incomplete separation of the trachea from the esophagus

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8
Q

Why does polyhydraminos lead to respiratory distress?

A
  • Intestinal atresia → regurgitate fluid
  • fluid enters trachea/aspirate → respiratory distress!
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9
Q

What three regions constitute the developing digestive tract?

A
  • Foregut
  • Midgut
  • Hindgut
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10
Q

What structures or parts of the digestive tract are associated with each developmental region?

A
  • Foregut
    • Celiac trunk
    • Vagus Nerve
    • Structures: Pharynx, Esophagus, Stomach, Upper duodenum, Liver, Gallbladder, and Pancreas
  • Midgut
    • Superior Mesenteric Artery
    • Vagus Nerve
    • Structures: Lower duodenum, jejunum, ileum, cecum, appendix, ascending colon, and right half of transverse colon
  • Hindgut
    • Inferior Mesenteric Artery
    • Pelvic Splanchnic Nerves
    • Structures: Left half of transverse colon, descending colon, sigmoid colon, rectum, and superior part of anal canal
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11
Q

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

A
  • Developing blood supply:
    • Yolk sac is first site of hematopoiesis
    • Liver serves as a site of hematopoietic tissue during embryonic and fetal deveopment
    • Spleen performs hematopoiesis during fetal life, and may revert to it in the adult
    • Bone marrow
  • Newborn
    • Bone marrow of long bones
  • Adults
    • pelvis, cranium, vertebrae, and sternum
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12
Q

What structures suspend the stomach from the dorsal and ventral walls, respectively?

A
  • Dorsal wall → Dorsal mesentary
  • Ventral wall → Ventral mesentary
    • persists as the lesser omentum
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13
Q

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

A
  • Ventral mesentery → lesser curvature
  • Dorsal mesentery → greater curvature
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14
Q

What structure extends between the liver and stomach/duodenum?

A

hepatogastric and hepatoduodenal ligaments

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15
Q

What are the two designated components of the lesser omentum?

A

hepatogastric and hepatoduodenal ligaments

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16
Q

What occurs with the stomach to bring the left and right vagus nerves into their position?

A
  • A 90-degree clockwise rotation of the stomach occurs
    • original left side of the stomach becomes the ventral surface (supplied by the left vagus nerve)
    • original right side becomes the dorsal surface (supplied by the right vagus nerve).
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17
Q

Where is each of the vagus nerves located?

A
  • Right vagus nerve → posterior trunk
    • posterior lesser curvature of the stomach
  • Left vagus nerve → anterior trunk
    • anterior lesser curvature of the stomach
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18
Q

What embryonic structure forms the greater omentum?

A

Dorsal mesentery (mesogastrium)

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19
Q

How does the omental bursa form and what accounts for its decrease in size?

A
  • Dorsal mesentery (mesogastrium) grows rapidly, enlarging the omental bursa, and forms the greater omentum.
  • Omental bursa in the greater omentum is obliterated.
  • Dorsal mesogastrium and the transverse mesocolon fuse to form the gastrocolic ligament that extends between the stomach and the transverse colon.
    • decreasing the size of the omental bursa
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20
Q

What embryonic structures form the gastrocolic ligament?

A

Dorsal mesentery + Transverse mesocolon

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21
Q

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

A
  • Where? → Dorsal mesentery
  • Germ layer? → Mesoderm
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22
Q

What is responsible for pyloric stenosis?

A

hypertrophy of the circular layer of smooth muscle in the stomach at the pyloric outlet

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23
Q

What is thought to be responsible for the occurrence of intestinal atresia and stenosis?

A

failure of recanalization of intestine

(usually duodenum)

24
Q

What is the most common site of intestinal atresia?

A

duodenum

25
Q

How does the child’s vomitus compare between pyloric stenosis and intestinal atresia/stenosis?

A
  • Pyloric stenosis → projectile vomiting, no bile
  • Intestinal atresia/stenosis → bile in vomitus
26
Q

What germ layer is responsible for formation of the hepatic ducts and cells?

A

Endoderm

27
Q

What forms the connective tissue component of the liver?

A

Transverse septum gives rise to fibrous capsule and connective tissue of the liver.

28
Q

What is the significance of the liver in blood formation?

A

Liver serves as a site of hematopoietic tissue during embryonic and fetal development (occurs prior to splenic hemopoiesis).

29
Q

What cells give rise to the gallbladder and ventral pancreas?

A

Endodermal hepatic diverticulum

30
Q

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

A

Endoderm

31
Q

Where do the two pancreatic ducts develop?

A
  • Ventral pancreatic bud → off of hepatic diverticulum in ventral mesentery
  • Dorsal pancreatic bud → off of foregut in dorsal mesentery
32
Q

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

A
  • Because the stomach and duodenum rotate to the right → the ventral pancreas and common bile duct end up behind where they fuse with the dorsal pancreas in the dorsal mesentery
33
Q

What is the source of the exocrine and endocrine pancreatic cells?

A
  • Acini (secretory units) develop from the terminal ends of the duct system and form the exocrine pancreas.
  • Budding of cells from the ducts gives rise to the endocrine pancreas (contain beta-cells, delta-cells, etc).
34
Q

What blood vessel supplies the midgut?

A

Superior Mesenteric Artery

35
Q

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

A

Rotation of the midgut loop with the small intestine returning first forces the distal colon to the left.

36
Q

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

A

Week 6/7 - Week 10/11

37
Q

Why does the midgut herniate into the umbilical cord?

A

because of rapid intestinal growth and the limited space in the abdominal cavity due to the large size of the liver and kidneys

38
Q

What is heterotopic gastric mucosa and pancreatic tissue?

A

cells lining the stomach or pancreatic tissue develop at sites other than in the stomach

39
Q

What structure gives rise to the ileal or Meckel diverticulum?

A

yolk stalk (duct)

40
Q

What is the clinical significance of an ileal or Meckel diverticulum?

A
  • can become inflamed
  • can result in a volvulus (twist around)
    • may lead to ischemia or strangulation of the bowel
41
Q

What is a congenital omphalocele?

A

herniated loop of intestine covered by amnion that lies outside of the abdominal cavity

42
Q

What is a congenital umbilical hernia?

A

Protruding mass of ventral abdominal musculature covered by subcutaneous tissue and skin

43
Q

How does a congenital umbilical hernia differ from an omphalocele?

A
  • Hernia → muscle covered by skin protruding
  • Omphalocele → intestines covered by amnion protruding
44
Q

What is the difference between gastroschisis and congenital omphalocele?

A
  • Gastroschisis
    • herniation of intestines from the abdominal cavity with NO overlying sac/peritoneum
  • Omphalocele
    • herniation of intestines from the abdominal cavity WITH overlying amnion
45
Q

What newborn/adult structures are formed by the dorsal mesentery?

A
  • Greater omentum
  • Gastrocolic ligament
  • Gastrosplenic ligament
  • Transverse mesocolon
  • Mesentery
  • Sigmoid mesocolon
46
Q

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

A

Dorsal mesentery (mesoduodenum and mesocolon) fuse with the peritoneal lining of the dorsal body wall, causing the duodenum and ascending/descending colons to be retroperitoneal.

47
Q

What is the most caudal portion of the hindgut?

A

Cloaca

48
Q

What is the purpose of the urorectal septum?

A

divides the cloacal membrane into a urogenital area and an anal area

49
Q

What two regions contribute to the formation of the anal canal?

A
  1. Hindgut
  2. Proctodeum
50
Q

What is the significance of the pectinate or anorectal line?

A
  • Indicates site of the anal membrane
    • where the endoderm of the hindgut becomes continuous with the ectoderm of the proctodeum (anal pit)
51
Q

What vascular anastomosis occurs in the area of the proctodeum?

A
  • Hindgut → inferior mesenteric artery
  • Proctodeum → inferior rectal branch of the internal pudendal artery
52
Q

What is the clinical significance of the dual vascular supply of the proctodeum?

A

***

53
Q

Where do the lymphatics of the hindgut and proctodeum drain, respectively?

A
  • Hindgut → inferior mesenteric nodes
  • Proctodeum → superficial inguinal nodes
54
Q

What is congenital megacolon?

A
  • absence of parasympathetic ganglia in the wall of the colon (usually distal colon)
    • due to failure of neural crest cells to migrate into the splanchnic mesoderm
  • AKA = Hirschsprung’s disease or Aganglionic Megacolon
55
Q

What accounts for an imperforated anus?

A

Persistence of the cloacal (anal) membrane to atresia of the anal canal/rectum

56
Q

Why do hindgut fistulas occur? Where do they occur?

A
  • Incomplete division of the cloaca by the urorectal septum into the rectum/anal canal and urogenital sinus
  • They occur:
    • Connect the hindgut + vagina → rectovaginal fistula
    • Connect the hindgut + urethra → rectourethral fistula
    • Connect the hindgut + bladder → rectovesical fistula

GI Week 3 - WLB (8 decks)

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