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GI-1 - Exam One > Funk - GI Embryology / Development > Flashcards

Funk - GI Embryology / Development Flashcards

1
Q

How does the intraembryonic body cavity form?

A

Forms during the “folding in” of the LATERAL PLATE MESODERM…divides lateral plate mesoderm into parietal (somatic) and visceral (splanchnic) mesoderm.

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2
Q

What does the parietal mesoderm turn in to?

A

Parietal mesoderm will form parietal serous membranes.

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3
Q

What does the visceral mesoderm form in to?

A

Visceral mesoderm will form visceral serous membranes and muscles/ct of organs.

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4
Q

How long does the intraembryonic cavity keep a connection to the extraembryonic cavity in the region of the midgut?

A

Until week 12 (can be in between weeks 10-12?)

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5
Q

Cantrell’s pentology? (she didn’t mention this during lecture, but be familar with it)

A

Cleft sternum
Ectopic cordis
Gastroschisis or omphalocele
Diaphragmatic hernia (anterior)
Congenital heart defects

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6
Q

Where does the liver form, grow, and develop in the developing embryo?

A

The ventral mesentery.

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7
Q

What is the hepatic diverticulum?

A

It is an outgrowth from second portion of duodenum that grows to be the liver.

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8
Q

List derivatives of ventral mesentery

A

Lesser omentum (hepatogastric, hepatoduodenal ligaments) (stomach to liver)

Falciform ligament (liver to ventral body wall)

Coronary and triangular ligaments (extend up to the diaphragm)

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9
Q

What are the only two structures in the adult abdomen that have retained the ventral mesentery?

A

The stomach and the “first part” of the duodenum.

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10
Q

List “truly retroperitoneal” structures (aka primary retroperitoneal structures)

A

Kidneys, ureters, bladder, aorta

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11
Q

List secondary retroperitoneal organs/structures (only four of them, know them)

A

Duodenum; ascending, descending colon; pancreas

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12
Q

Fully peritonealized organs?

A

Stomach, spleen, 1st and 4th part of duodenum, jejunum, ileum, transverse and sigmoid colon

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13
Q

Describe the SEPTUM TRANSVERSUM

A

1) Forms from cervical somites 3, 4 & 5 (remember “C3, 4, & 5 keep the diaphragm alive”)
2) Plate of mesoderm which separates thoracic and peritoneal cavities.
3) Will form bulk of diaphragm; muscle and central tendon of diaphragm; “most important contributor to the diaphragm”

*4) Septum transversum does not completely separate thoracic and abdominal cavities; leaves openings on either side of the foregut called pericardioperitoneal canals (posterolaterally)

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14
Q

What other structure(s) form part of the diaphragm?

A

The pleuroperitoneal membranes / folds (forms central tendon).

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15
Q

When does the diaphragm reach the level of the LV1 (in the developing embryo)?

A

By week 8.

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16
Q

Review of innervation of diaphragm…

A

Motor: Phrenic nerves (right and left)

Sensory: Phrenic nerves to central tendon; intercostal nn. to muscular diaphragm

Spinal nerves C3,4 & 5

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17
Q

Describe the posterolateral congenital defect (Bochdalek hernia) of the diaphragm

A

(This is the more severe and more common of the two congenital hernias of the diaphragm)

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.

***Large opening can lead to compression of the lung…leading to underdevelopment / hypoplasia of the lung(s).

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18
Q

What about a parasternal hernia (Morgagni hernia)?

A

Less severe (usually asymptomatic until lateral in life).

Anterior defect in muscular portion of diaphragm.

Small, sometimes not detected until child is several years old.

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19
Q

Describe eventration of the diaphragm

A

It is a weakness (usually unilateral) of diaphram due to failure of myotome migration.

Allows abdominal viscera to ‘‘ballon’’ into the thoracic cavity.

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20
Q

Know how all 3 of the germ layers contribute to formation of the gut tube

A

Endoderm: epithelium and glands

Mesoderm: connective tissue and smooth muscle

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

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21
Q

List portions and deriatives of the foregut

A

Pharynx (described with pharyngeal arches), esophagus, stomach, parts one and two of duodenum; liver, gallbladder and pancreas, spleen

Celiac artery supplies abdominal portion of foregut

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22
Q

List the structures of the midgut and its arterial supply

A

Part three and four of duodenum, small intestine, cecum, appendix, ascending colon and proximal (right) 2/3’s of transverse colon

Superior mesenteric artery

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23
Q

And for the hindgut?

A

Distal 1/3 of transverse colon to upper anal canal

Inferior mesenteric artery

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24
Q

What do all three of these separate compartments/segments each share?

A

Same vascular supply, innervation and lymphatic drainage.

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25
Q

Define atresia

A

A complete occlusion of a lumen (can effect the entire gut, but is most common in the duodenum)

Recanalization is completely absent in atresia

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26
Q

Define stenosis

A

Incomplete occlusion (narrowing) of a lumen (also most common in the duodenum)

Partial “lack” of recanalization

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27
Q

Describe congenital hiatal hernia

A

The esophagus fails to elongate and thus pulls the cardiac portion of the stomach through diaphragm into the thorax.

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28
Q

Briefly describe the rotation of the stomach during development

A

It rotates 90 degrees clockwise around its longitudinal axis (dorsal, greater curvature is rotated to the left; ventral, lesser curvature is moved to the right).

It also rotates around its anteroposterior axis, clockwise, to make the “J shape”.

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29
Q

What creates the lesser sac (omental bursa)?

A

The rotation of the stomach (stretches the dorsal mesentery to allow the omental bursa to lie inferior and posterior to the stomach, also forms the “apron” of the greater omentum anteriorly).

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30
Q

What is the main congenital anomaly of the stomach?

A

Pyloric stenosis – hypertrophy of smooth muscle around pyloric sphincter; presents with forcible vomiting of stomach contents after feeding.

31
Q

Describe development of the spleen

A

Forms from mesenchymal cells within the two layers of dorsal mesogastrium.

Rotation of gut results in spleen being situated on left side of abdominal cavity.

32
Q

Describe the developing liver

A

Endoderm gives rise to parenchyma; mesoderm gives rise to stroma.

Functions as a hematopoietic organ during 2nd month.

Bile formation begins during 12th week.

33
Q

Describe the developing gallbladder and cystic duct

A

Forms from an evagination of bile duct.

Because of rotation of the foregut, the bile duct passes posterior to duodenum.

34
Q

Describe the developing pancreas

A

Arises from two endodermal outgrowths from the duodenum (dorsal, ventral buds). Rotation of duodenum causes fusion of buds. Most of pancreas is derived from the dorsal bud; ventral bud forms lower portion of head and uncinate process.

Main pancreatic duct derived from ventral pancreatic duct + distal dorsal pancreatic duct.

Accessory pancreatic duct is derived from proximal part of dorsal pancreatic duct.

35
Q

What pancreatic bud goes on to form the uncinate process of the pancreas?

A

The ventral pancreas bud.

36
Q

Another name for accessory pancreatic duct (formed from the dorsal bud)?

A

Santorini’s duct

37
Q

Fancy name for the pancreatic duct (formed from the ventral bud of the pancreas)?

A

Wirsung’s duct.

38
Q

Cause of abberent / accessory pancreatic tissue?

A

Abnormal migration of tissue during gut rotation (can cause degradation of surrounding tissue).

39
Q

Cause and possible consequence of annular “ring” pancreas?

A

Bifid ventral pancreatic bud ; during rotation the bifid bud encircles the duodenum.

After fusion of the pancreas, the annular tissue can constrict the duodenum.

40
Q

Duodenum is made up of which segments of the gut tube?

A

It is part foregut and part midgut. It becomes secondarily retroperitoneal.

41
Q

Most common sites of luminal stenosis?

A

1) Duodenum
2) Esophagus (stricture)
3) Pylorus

42
Q

Describe duodenal stenosis (congenital anomaly)

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 (during pregnancy).

Baby presents with failure to thrive.

43
Q

When does the midgut remain in communication with the yolk sac via the vitelline duct until?

A

Until about week 10.

44
Q

Describe physiological herniation of the midgut

A

This occurs during week 6 as space within the abdominal cavity becomes much reduced. As a result, the gut around the superior mesenteric artery herniates though the umbilical ring into the extraembryonic cavity.

45
Q

Describe midgut rotation

A

The primary intestinal loop undergoes a rotation of 270 degrees counterclockwise (this happens while the gut is herniated).

As a result of rotation, the mesentery proper becomes twisted and the ascending/descending colon become secondarily retroperitoneal.

46
Q

Describe the retraction of the herniated loops of the midgut

A

The herniated intestinal loops return to abdominal cavity during week 10 (thru early week 12).

The jejunum returns first and comes to lie on left side.

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).

47
Q

What is OMPHALOCELE?

A

“Umph-fell-o-ceel” results from failure of midgut to return to abdominal cavity. Tissue protrudes through umbilicus and is covered by the amniotic membrane.

48
Q

What is GASTROSCHISIS?

A

Ventral body wall defect, just lateral to the umbilicus.

“Gastro-keesus” 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.

49
Q

Describe the common umbilical hernia

A

These result 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.

50
Q

What is a Meckel’s (Ileal) diverticulum?

A

This results from a persistence of the vitelline duct. Rule of 2’s: Occurs in 2% of population; presents in year 2 usually, 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).

Presents similar to appendicitis (RLQ pain), but appendicitis is rare is 2 year olds.

51
Q

Malrotation of gut

A

“If the gut doesn’t rotate correctly, it won’t come back into the abdomen correctly”.

Usually asymptomatic, but may result in volvulus and potential loss of blood supply.

52
Q

Dangers of stenoses and atresias of the gut?

A

Stenoses and atresias may occur anywhere along intestine resulting from vascular compromise or failure to re-canalize.

53
Q

Large intestine atresia/stenosis?

A

Usually caused by ischemia.

54
Q

What is a retrocolic hernia?

A

An entrapment of small intestine behind colon

55
Q

Describe hindgut development

A

Cloaca – distal most portion of gut tube; endoderm lined cavity which will contribute to formation of the hindgut and urogenital system.

Urorectal septum devides cloaca divides into urogenital sinus and anorectal canal.

Cloacal membrane ruptures during week 7.

56
Q

What is the pectinate (dentate) line?

A

Marks division between ectoderm/endoderm (base of anal columns/sinuses), where the cloacal membrane attached developmentally.

57
Q

Cause of Hirschprung’s Disease (congenital megacolon)?

A

Failure of neural crest cells to migrate into caudal/distal large intestine or rectum –> absence of parasympathetic ganglia

(Fecal matter accumulates due to paralyzed bowel / decreased parastalsis)

Sx: constipation, uncomfortable toddler, distended belly

Tx: Surgery

58
Q

Rectourethral and rectovaginal fistulas cause?

A

Malformation of urorectal septum

59
Q

Cause of imperforate anus?

A

Failure of cloacal membrane to degenerate (sx: no stool production, fix = surgery).

60
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.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).

61
Q
  1. The greater omentum is formed from:

a. a single layer of ventral mesentery
b. a double layer of ventral mesentery
c. a single layer of dorsal mesentery
d. a double layer of dorsal mesentery

A

d. a double layer of dorsal mesentery

62
Q
  1. What statement is TRUE about the lesser sac?

a. it is the space located anterior to the stomach
b. it communicates with the greater sac via the epiploic foramen
c. it is the structure that develops into the lesser curvature of the stomach
d. two of the above are true

A

b. it communicates with the greater sac via the epiploic foramen

63
Q
  1. The stomach forms as a fusiform (spindle shaped) dilation of the foregut during the ____ week of development.

a. 3rd
b. 4th
c. 5th
d. 6th

A

b. 4th

64
Q
  1. When the stomach rotates_________ about a longitudinal axis, the right vagus nerve becomes the __________.

a. 90 degrees clockwise, anterior vagal trunk
b. 90 degrees counterclockwise, anterior vagal trunk
c. 90 degrees clockwise, posterior vagal trunk
d. 90 degrees counterclockwise, posterior vagal trunk

A

c. 90 degrees clockwise, posterior vagal trunk

65
Q
  1. Which statement is TRUE about the greater curvature of the stomach?

a. a structure formed from dorsal mesentery attaches to it
b. it is located superior to the lesser curvature of the stomach
c. it forms from the embryonic ventral (anterior) border of the stomach
d. the left vagus nerve lies directly along this curvature

A

a. a structure formed from dorsal mesentery attaches to it

66
Q
  1. The midgut is supplied by branches of the __________________ artery.

a. celiac trunk
b. splenic
c. superior mesenteric
d. inferior mesenteric

A

c. superior mesenteric

67
Q
  1. This condition occurs when the intestines fail to return to abdominal cavity in the 10-11th week of development. This condition also is associated with other congenital abnormalities.

a. volvulus
b. ileal (Meckel’s) diverticulum
c. hiatal hernia
d. omphalocele

A

d. omphalocele

68
Q
  1. Which of the following statements is true about the rotation of the intestine?

a. After rotation, the cranial limb of the primary intestinal loop is pulled back into the abdominal cavity first, followed by the caudal limb
b. when the intestine returns to the abdominal cavity, the transverse colon and the sigmoid colon become secondarily retroperitoneal
c. total net rotation of the intestine is 270 degrees clockwise, as viewed from the front of the body
d. the primary intestinal loop herniates into the umbilicus beginning the 8th week of development

A

a. After rotation, the cranial limb of the primary intestinal loop is pulled back into the abdominal cavity first, followed by the caudal limb

69
Q
  1. What adult structure is formed from the caudal limb of the primary intestinal loop?

a. jejunum
b. cecum
c. descending colon
d. sigmoid colon

A

b. cecum

70
Q
  1. Which statement is FALSE about the vitelline duct?

a. it connects to the apex of the primary intestinal loop
b. it connects to the yolk sac
c. adult remnants of this duct never are of clinical significance
d. it normally regresses and disappears during the fetal period

A

c. adult remnants of this duct never are of clinical significance

71
Q

Mneumonic for Bochdalek hernias

A

Mnemonic

B: Bochdalek
B: big
B: back
B: baby
B: bad

“BBBBB”

72
Q

Timeline in development (know these):

1) Diaphragm reaches level of LV1
2) Midgut detaches from yolk sac / the vitelline duct
3) When can omphalocele occur?
4) physiological herniation of the midgut?
5) primary intestinal loop?
6) ascending and descending colon become 2ndary retroperitonealized and fuse to posterior body wall?

A

1) week 8
2) 11th week on
3) This condition can occur when the intestines fail to return to abdominal cavity in the 10-11th week of development
4) around week 6
5) during week 5
6) 11th week on

73
Q

What are the lamina propria, muscularis mucosa, submucosa, muscularis externa, and adventitia/serosa all derived from?

A

Mesoderm

GI-1 - Exam One (9 decks)

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