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GI > Embryology > Flashcards

Embryology Flashcards

1
Q

The ventral mesentery suspends the gut tube to anterior body wall, and extends from caudal foregut to proximal duodenum. What are the three derivatives of it?

A

Lesser omentum (hepatogastric, hepatoduodenal ligaments)
Falciform ligament
Coronary and triangular ligaments

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2
Q

What are the three types of peritonealization?

A

Primary retroperitoneal

Secondary retroperitoneal

Peritonealized

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3
Q

What are three examples of primary retroperitoneal structures?

A

kidneys, ureters, bladder

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4
Q

What are four examples of secondary retroperitoneal structures?

A
  1. duodenum
  2. ascending colon
  3. descending colon
  4. pancreas
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5
Q

What are some examples of peritonealized structures?

A
  1. stomach
  2. spleen
  3. duodenum parts 1 and 4
  4. jejunum
  5. ileum
  6. transverse colon
  7. sigmoid colon
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6
Q

What is different about secondary retroperitoneal structures?

A

Originate in peritoneum and move retroperitoneally during development.

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7
Q

The septum transversum is a plate of mesoderm which separates thoracic and peritoneal cavities. What does it form?

A
  • Will form bulk of diaphragm; muscle and central tendon of diaphragm.
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8
Q

Does the septum transversum seperate the thoracic and abdominal cavities?

What does it develop from?

A

Septum transversum does not completely separate thoracic and abdominal cavities; leaves openings on either side of the foregut called pericardioperitoneal canals.

Cervical somites 3,4,5

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9
Q

What are the two openings created by the septum transversum on either side of the foregut?

A

pericardioperitoneal canals

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10
Q

Pleuropericardial membranes will separate ….

A

pleural and pericardial cavities.

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11
Q

Pleuroperitoneal membranes will separate…

A

pleural and peritoneal cavities.

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12
Q

What sources contribute to the diaphragm?

A

Septum transversum - central tendon + muscle

Pleuroperitoneal membranes: Central tendon

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13
Q

What is the motor innervation of the diaphragm?

A

phrenic nerve

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14
Q

Describe the positional changes of the diaphragm. When is the diaphragm at LV1?

A

The muscle of the diaphragm forms from cervical somites 3-5.
Differential growth of the body leads to a descent of the diaphragm into the thorax.
By week 8; diaphragm is at level of 1st lumbar vertebra.

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15
Q

What is the sensory innervation of the diaphragm?

A

– phrenic nerve to central tendon; intercostal nn to muscular diaphragm.

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16
Q

What are the congenital anomalies of the body wall?

A
  1. Congenital diaphragmatic hernias
  2. Eventration of the diaphragm
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17
Q

What are the types of congenital diaphragmatic hernias?

A
  1. Posterolateral defect (Bochdalek hernia)
  2. Parasternal hernia (Morgagni hernia)
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18
Q

Describe posterolateral defect hernia.

What is this a common cause of?

A
  • Incomplete formation of pleuroperitoneal membranes; most often on left.
  • Small intestine, and/or other viscera, herniate through defect into pleural cavity.
  • The lungs and heart are compressed ; common cause of pulmonary hypoplasia.
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19
Q

Describe parasternal hernias

A

Anterior defect in muscular portion of diaphragm.
Small, sometimes not detected until child is several years old.

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20
Q

What is eventration of the diaphragm due to? What does this lead to?

A
  • Weakness (usually unilateral) of diaphram due to failure of myotome migration.
  • Allows abdominal visceral to ‘‘ballon’’ into the thoracic cavity.
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21
Q

What does the endoderm bequeth to the GI tract?

A

epithelium and glands

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22
Q

What does mesoderm develop into for the GI system?

A

CT and smooth muscle

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23
Q

What does extoderm contribute to the GI system?

A

epithelium at ends of tube (mouth, lower 1/3 of anal canal)

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24
Q

The rostral and caudal ends of the gut tube are originally closed by what membranes? Rupture during what weeks?

A

Rostral - oropharyngeal, week 4

Caudal - Cloacal, week 7

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25
Q

What are the compoinents of the foregut?

A
  1. Pharynx
  2. Esophagus
  3. Stomach
  4. ½ duodenum
  5. Spleen
  6. Pancreas
  7. Liver
  8. gallbladder
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26
Q

What are the components of the midgut?

A
  1. ½ duodenum
  2. Jejunum
  3. Ileum
  4. Cecum/appendix
  5. Ascending colon
  6. 2/3 transverse colon
27
Q

What are the components of the hind gut?

A
  1. 1/3 transverse colon
  2. Descending colon
  3. Sigmoid colon
  4. Rectum
  5. Proximal anal canal
28
Q

What artery supplies the foregut?

A

celiac artery

29
Q

What artery supplies the midgut?

A

superior mesenteric artery

30
Q

What artery supplies the hindgut?

A

Inferior mesenteric artery

31
Q

What are the congenital anomolies of the esophagus we covered?

A
  1. atresias
  2. stenoses
  3. hiatal hernia
32
Q

What are atresias and stenoses caused by?

A
  1. malformation of tracheoesophageal septum.
  2. Or incomplete recanalization of the gut tube.
33
Q

What happens if recanalization of the esophagus is incomplete? Absent?

A

Incomplete = stenosis

absent = atresia

34
Q

How does a congenital hiatal hernia occur?

A

esophagus fails to elongate, pulls stomach through diaphragm.

35
Q

Describe the rotation of the stomach

A

Stomach rotates 90° clockwise around longitudinal axis. Dorsal part (greater curvature) is now to left, ventral part (lesser curvature) is now to right.
Stomach also rotates around its anteroposterior axis – the pyloric part moves upward and to the right; the cardiac portion moves downwards and to the left.

36
Q

What happens to the dorsal mesentery as the stomach rotates? What happens to the omental bursa in later development?

A

Omental Bursa

As the stomach rotates, it stretches the dorsal mesentery. The omental bursa comes to lie inferior and posterior to stomach.
During later development, the layers of the greater omentum fuse.

37
Q

What is the one congenital anomoly of the stomach we discussed?

A

Pyloric stenosis

38
Q

Describe pyloric stenosis

A

hypertrophy of smooth muscle around pyloric sphincter; present with forcible vomiting of stomach contents after eating.

39
Q

Frome what ends of the foregut and midgut does the duodenum arise?

A

Arises from the caudal end of the foregut (parts 1 and 2) AND the rostral end of the midgut (parts 3 and 4); (how does this correlate to blood supply ?).

40
Q

As the stomach rotates, so the duodenum… With the pancreas we get a?

A

is pulled superiorly and to the right; together with the rapid growth of the pancreas, results in a C-shaped duodenum.

41
Q

What are duodenal stenosis caused by?

What happens to the infant?

What would the mother present with?

A
  • most often caused by failure to recanalize; mostly affects 3rd and 4th portions;
  • digested food + bile are forcibly vomited (green-colored); distended epigastrium due to overfilled stomach.
  • Due to fact that infant is not swallowing amnionic fluid, mother often presents with polyhydramnios.
42
Q

Describe the formation of the midgut!

A
  1. Midgut loop forms around week 5
  2. mudgut loop physiologically herniates at week 6
  3. Midgut loop rotates, 270 degrees - counterclockwise
  4. Midgut loop retracts around weeks 10-12
43
Q

Describe midgut rotation

A

The primary intestinal loop undergoes a rotation of 270 degrees counterclockwise.
As a result of rotation, the mesentery proper becomes twisted and the ascending/descending colon become secondarily retroperitoneal.

44
Q

Describe the retraction of the herniated loops.

A
  1. The herniated intestinal loops return to abdominal cavity during week 10.
  2. The jejunum returns first and comes to lie on left side.
  3. The cecum returns last and lies in upper right quadrant; the cecum then descends to lie in the lower right quadrant. The appendix forms after the midgut returns to the abdomen as the cecum is descending (thus retrocecal postion).
45
Q

What is an omphalocele?

A

results from failure of midgut to return to abdominal cavity. Tissue protrudes through umbilicus and is covered by the amniotic membrane.

46
Q

What is Gastroschisis caused by?

A

results when gut herniates through weakness in body wall; typically occurs lateral to umbilicus (to right).

Usually results from incomplete fusion of ventral body wall during folding. Herniated bowel is not covered by amniotic membrane; bathed in amniotic fluid.

47
Q

Does the gut form normally in gastrochisis?

A

Yes, problem is a defect in abdominal wall

48
Q

Which has better prognosis…

omphalocele or gastrochisis?

A

Gastroschisis

49
Q

How does an umbilical hernia occur? How do you treat?

A

results when gut herniates into umbilical cord after returning to abdominal cavity. Loops of bowel herniate through an imperfectly closed umbilicus; along midline. Herniated tissue covered by skin, subcutaneous tissue.

Typically will self reduce within months

50
Q

What does Meckel’s (Ileal) diverticulum result from?

A

persistent vitelline duct

51
Q

Describe the rule of 2’s for Meckel’s duct.

A

Rule of 2’s: Occurs in 2% of population; 2x more likely in males; found within distal 2 feet of ileum; usually about 2 inches long; 2% become symptomatic usually before the age of 2; 2 types of tissue (gastric, pancreatic).

52
Q

How does Meckel’s diverticulum present?

How is this repaired?

A

Fecal matter draining out of umbilicus.

Surgically with good outcomes usually

53
Q

What does malrotation of the gut potentially result in?

A

may result in volvulus and potential loss of blood supply.

54
Q

Where do stenoses and atresias occur along the intestine? What causes this? (2 things)

A

Stenoses and atresias may occur anywhere along intestine resulting from vascular compromise or failure to re-canalize (most common in small intestine).

55
Q

Failure of ascending colon to become retroperitoneal results in a long mesocolon which may allow for?

A

abnormal movements and potentially volvulus of the colon. Retrocolic hernia (entrapment of small intestine behind colon) may also result.

56
Q

Describe the hindgut development

A
  1. Cloaca – distal most portion of gut tube; endoderm lined cavity which will contribute to formation of the hindgut and urogenital system.
  2. Urorectal septum devides cloaca divides into urogenital sinus and anorectal canal.
  3. Cloacal membrane ruptures during week 7.
  4. Pectinate Line – marks division between ectoderm/endoderm.
57
Q

What is the pectinate line representative of?

A

Marks where the endoderm and ectoderm came together during development

58
Q

How does hirschprings disease occur? What is it?

A

Congenital megacolon

failure of neural crest cells to migrate into caudal large intestine or rectum; absence of parasympathetic ganglia.

NEURAL CREST CELL ALERT!!!!!!!!!!!

59
Q

Gut postganglionic parasympathetic innervation arises from what kind of cells?

A

Neural crest cells

60
Q

What do rectourethral and rectovaginal fistulas result from?

A

Rectourethral and rectovaginal fistulas result from an anterior displacement of the hindgut.

61
Q

What causes a rectoanal atresia?

A

Rectoanal atresias result from loss of vascular supply or failure of recanalization.

62
Q

What causes an imperforate anus?

A

failure of cloacal membrane to degenerate.

63
Q

A newborn male presents with a portion of jejunoileum protruding from his abdomen just lateral to the umbilicus (the herniated bowel is not covered with amniotic membrane). The infant’s anomaly most likely resulted from a:

A.failure of the midgut to retract into the peritoneal cavity.
B.failure of the ventral body wall to fuse.
C.failure of the vitelline duct to degenerate.
D.malrotation of the midgut.
E.weakness in the umbilicus.

A

A newborn male presents with a portion of jejunoileum protruding from his abdomen just lateral to the umbilicus (the herniated bowel is not covered with amniotic membrane). The infant’s anomaly most likely resulted from a:

this is gastroschisis

A.failure of the midgut to retract into the peritoneal cavity (omphalocele).
B.failure of the ventral body wall to fuse.
C.failure of the vitelline duct to degenerate (ileal diverticulum).
D.malrotation of the midgut (can cause volvulus; no hernia though).
E.weakness in the umbilicus (umbilical hernia; covered with skin also).

64
Q
A

GI (26 decks)

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