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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?

25
How does the child's vomitus compare between pyloric stenosis and intestinal atresia/stenosis?
* Pyloric stenosis → projectile vomiting, no bile * Intestinal atresia/stenosis → bile in vomitus
26
What germ layer is responsible for formation of the hepatic ducts and cells?
Endoderm
27
What forms the connective tissue component of the liver?
Transverse septum gives rise to fibrous capsule and connective tissue of the liver.
28
What is the significance of the liver in blood formation?
Liver serves as a site of hematopoietic tissue during embryonic and fetal development (occurs prior to splenic hemopoiesis).
29
What cells give rise to the gallbladder and ventral pancreas?
**Endoderm**al hepatic diverticulum
30
What germ layer gives rise to the pancreatic ducts and pancreas?
Endoderm
31
Where do the two pancreatic ducts develop?
* Ventral pancreatic bud → off of hepatic diverticulum in ventral mesentery * Dorsal pancreatic bud → off of foregut in dorsal mesentery
32
Why does the ventral pancreas become located in the dorsal wall and fused with the dorsal pancreas?
* 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
What is the source of the exocrine and endocrine pancreatic cells?
* 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
What blood vessel supplies the midgut?
Superior Mesenteric Artery
35
How does the midgut rotate to bring the intestines into the adult position?
Rotation of the midgut loop with the small intestine returning first forces the distal colon to the left.
36
During which weeks of development is the midgut herniated into the umbilical cord?
Week 6/7 - Week 10/11
37
Why does the midgut herniate into the umbilical cord?
because of rapid intestinal growth and the limited space in the abdominal cavity due to the large size of the liver and kidneys
38
What is heterotopic gastric mucosa and pancreatic tissue?
cells lining the stomach or pancreatic tissue develop at sites other than in the stomach
39
What structure gives rise to the ileal or Meckel diverticulum?
yolk stalk (duct)
40
What is the clinical significance of an ileal or Meckel diverticulum?
* can become inflamed * can result in a volvulus (twist around) * may lead to ischemia or strangulation of the bowel
41
What is a congenital omphalocele?
herniated loop of intestine covered by amnion that lies outside of the abdominal cavity
42
What is a congenital umbilical hernia?
Protruding mass of ventral abdominal musculature covered by subcutaneous tissue and skin
43
How does a congenital umbilical hernia differ from an omphalocele?
* Hernia → muscle covered by skin protruding * Omphalocele → intestines covered by amnion protruding
44
What is the difference between gastroschisis and congenital omphalocele?
* 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
What newborn/adult structures are formed by the dorsal mesentery?
* Greater omentum * Gastrocolic ligament * Gastrosplenic ligament * Transverse mesocolon * Mesentery * Sigmoid mesocolon
46
Why are some structures retroperitoneal, while other structures are suspended by a mesentery?
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
What is the most caudal portion of the hindgut?
Cloaca
48
What is the purpose of the urorectal septum?
divides the cloacal membrane into a urogenital area and an anal area
49
What two regions contribute to the formation of the anal canal?
1. Hindgut 2. Proctodeum
50
What is the significance of the pectinate or anorectal line?
* Indicates site of the anal membrane * where the **endoderm** of the hindgut becomes continuous with the **ectoderm** of the proctodeum (anal pit)
51
What vascular anastomosis occurs in the area of the proctodeum?
* Hindgut → inferior mesenteric artery * Proctodeum → inferior rectal branch of the internal pudendal artery
52
What is the clinical significance of the dual vascular supply of the proctodeum?
\*\*\*
53
Where do the lymphatics of the hindgut and proctodeum drain, respectively?
* Hindgut → inferior mesenteric nodes * Proctodeum → superficial inguinal nodes
54
What is congenital megacolon?
* 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
What accounts for an imperforated anus?
Persistence of the cloacal (anal) membrane to atresia of the anal canal/rectum
56
Why do hindgut fistulas occur? Where do they occur?
* 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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