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Human Structure - Block 3 > Embryology 7 > Flashcards

Embryology 7 Flashcards

1
Q

In what week does the primordial gut tube form?

A

week 4

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2
Q

During the formation of the primordial gut tube, the yolk sac is incorporated into the embryo via lateral folding. How does the gut tube remain connected to the yolk sac?

A

omphaloenteric duct

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3
Q

The omphaloenteric duct connects what two structures?

A

connects gut tube to yolk sac

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4
Q

What membranes are responsible for closing the primordial gut tube?

A

oropharyngeal membrane (cranial end)

cloacal membrane (caudal end)

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5
Q

What are the three distinct regions of the primordial gut tube?

A

foregut

midgut

hindgut

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6
Q

What is the arterial supply to the foregut? (4)

A

celiac trunk (to most of the foregut)

exceptions include:

derivatives of pharyngeal arches, lower respiratory system, large portion of esophagus

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7
Q

What is the arterial supply to the midgut?

A

superior mesenteric artery

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8
Q

What is the arterial supply to the hindgut?

A

inferior mesenteric artery

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9
Q

The developing gut tube lies within what cavity?

A

peritoneal cavity

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10
Q

The developing gut tube is covered by

A

peritoneum (because it lies within the peritoneal cavity)

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11
Q

What are mesenteries?

A

double layers of peritoneum that suspend the gut tube between the ventral and dorsal abdominal walls

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12
Q

The mesogastrium connects what two structures?

A

connects stomach with body wall

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13
Q

The mesocolon connects what two structures?

A

colon with body wall

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14
Q

Describe the function of the ventral mesentery.

A

suspends foregut + cranial part of midgut (up to umbilicus) from anterior body wall

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15
Q

Where is the dorsal mesentery found?

A

stretches along the entire gut tube

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16
Q

Give three examples of abdominal organs that grow between the two layers of mesentery.

A

liver

gallbladder

pancreas

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17
Q

What is a consequence of portions of the dorsal mesentery retracting during development?

A

as a result of the dorsal mesentery retracting, some organs become adhered to the dorsal wall of the abdominal cavity

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18
Q

What are secondarily retroperitoneal organs?

A

organs that become adhered to the dorsal abdominal wall because of dorsal mesentery retraction

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19
Q

In what region(s) are secondarily retroperitoneal organs covered with peritoneum?

A

secondarily retroperitoneal organs are covered with peritoneum on their anterior wall

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20
Q

What are primarily retroperitoneal organs?

A

organs that develop retroperitoneally from the beginning (in contrast to secondarily retroperitoneal organs)

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21
Q

Give an example of a primarily retroperitoneal organ.

A

kidneys

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22
Q

What are the derivatives of the foregut? (8)

A

primitive pharynx + derivatives

lower respiratory system

esophagus

stomach

part of duodenum cranial to opening of common bile duct

liver

biliary apparatus

pancreas

[PPPLLESB]

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23
Q

In what week does the esophagus begin to form?

A

week 4

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24
Q

Describe how the primitive esophagus is formed in week 4.

A

laryngotracheal tube branches off from primitive gut and is separated from gut by tracheoesophageal septum

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25
Q

Describe the muscle composition (and origin of muscle) of the growing esophagus. (2)

A

cranial part of esophagus = striated muscle from pharyngeal arches 4 and 6

caudal part of esophagus = smooth muscle from visceral lateral mesoderm

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26
Q

What provides innervation to the two types of esophageal muscle?

A

vagus nerve (CN X)

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27
Q

The stomach develops from

A

the caudal part of the foregut tube

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28
Q

Describe the positioning of the stomach during the early stages of its development.

A

stomach positioned in midline with gastro-esophageal junction cranial and pyloric-duodenal junction caudal

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29
Q

Describe the positioning of the vagus nerve during the early development of the stomach.

A

vagus nerves run laterally on both sides of developing stomach

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30
Q

What is the underlying cause for the formation of the greater and lesser curvatures of the stomach?

A

dorsal side of stomach grows faster than ventral side → greater curvature on dorsal side + lesser curvature on ventral side

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31
Q

How does the stomach further develop following the formation of the greater and lesser curvatures?

A

stomach rotates 90° clockwise around longitudinal axis → ventral border/lesser curvature moves to right side + dorsal border/greater curvature moves to left side

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32
Q

Differentiate between the right and left vagus nerves in terms of what they innervate. Why does this dichotomy arise? (3)

A

right vagus nerve → posterior wall

left vagus nerve → anterior wall

arises because of clockwise 90° rotation of stomach

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33
Q

Following the first 90° rotation, how does the stomach further develop?

A

another rotation around the dorsal-ventral axis occurs → gastro-esophageal junction moves caudally + pyloric-duodenal junction moves cranially

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34
Q

What is the fate of the dorsal and ventral mesenteries that suspend the foregut tube?

A

dorsal mesentery → dorsal mesogastrium

ventral mesentery → ventral mesogastrium

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35
Q

The duodenum develops from (2)

A

the caudal portion of the foregut

the cranial portion of the midgut

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36
Q

The duodenum receives blood supply from (2)

A

celiac trunk (because it is partially derived from the foregut)

superior mesenteric artery (because it is partially derived from the midgut)

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37
Q

Describe how the duodenum changes during the rotation of the stomach.

A

duodenal loop rotates to right

becomes pressed against posterior abdominal wall

dorsal mesenterium regresses

most parts of duodenum become secondarily retroperitoneal

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38
Q

Describe the fate of the duodenal lumen.

A

in weeks 5-6, duodenal lumen is temporarily obliterated but then recanalizes by the end of week 8

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39
Q

The liver and biliary apparatus develop from

A

the caudal portion of the foregut

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40
Q

What is another name for the liver bud?

A

hepatic diverticulum

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41
Q

The liver bud originates from

A

the ventral portion of the caudal portion of the foregut, in week 4

42
Q

After the liver bud forms, it branches into (2)

A

the mesoderm of the septum transversum

the cranial portion of the ventral mesentery

43
Q

The mesoderm of the septum transversum develops into

A

the diaphragm

44
Q

Within the ventral mesentery, the liver bud divides into what two parts?

A

larger/superior portion = liver primordium

smaller/inferior portion = gallbladder

45
Q

The connection between the liver bud and foregut develops into

A

the common bile duct

46
Q

What is the origin of the common bile duct?

A

the connection between the liver bud and foregut

47
Q

The stalk that connects the gallbladder to the liver bud becomes

A

the cystic duct

48
Q

What is the origin of the cystic duct?

A

the stalk that connects the gallbladder to the liver bud

49
Q

The ventral mesentery is divided by the liver into what two structures?

A

lesser omentum

falciform ligament

50
Q

What forms the visceral peritoneum of the liver?

A

ventral mesentery

51
Q

What structures comprise the lesser omentum, and what is their anatomical function? (3)

A

hepatogastric ligament

hepatoduodenal ligament

function: connect liver with stomach + duodenum

52
Q

What is the anatomical function of the falciform ligament?

A

connects anterior body wall with liver

53
Q

What structures does the umbilical vein?

A

umbilical vein connects placenta to liver

54
Q

Where is the umbilical vein located in the embryo?

A

umbilical vein is located at free border of falciform ligament

55
Q

What is the remnant of the umbilical vein in the adult?

A

round ligament

56
Q

The pancreas develops from

A

1 dorsal + 2 ventral pancreatic bud

57
Q

Describe the growth of the pancreatic buds. (2)

A

pancreatic buds grow from foregut tube into dorsal and ventral mesenteries

two ventral buds merge into one bud

58
Q

List the steps in the formation of the pancreas. (2)

A

duodenum rotates to right

ventral and dorsal buds merge to form pancreas

59
Q

Describe how the head of the pancreas is formed.

A

after duodenal rotation, smaller ventral pancreatic bud is superior to dorsal pancreatic bud and forms the head of the pancreas

60
Q

Is the pancreas primarily or secondarily retroperitoneal?

A

rotation of the stomach + duodenum pushes pancreas in dorsal direction → secondarily retroperitoneal

61
Q

(T/F) The spleen is a derivative of the foregut.

A

False. The spleen forms in the dorsal mesogastrium from the visceral mesenchyme and is therefore not a derivative of the foregut.

62
Q

The spleen is derived from

A

the visceral mesenchyme in the dorsal mesogastrium

63
Q

Describe how the spleen forms. (2)

A

mesenchymal lobules appear at week 5

mesenchymal lobules coalesce to form spleen

64
Q

What is the final location of the spleen?

A

left upper quadrant

65
Q

What determines the final location of the spleen?

A

rotations of the stomach and its adjacent organs

66
Q

When does hematopoiesis occur in the spleen?

A

hematopoiesis occurs in the spleen until late fetal life

67
Q

List three types of anomalies of foregut derivatives.

A

esophageal atresia

duodenal atresia = stenosis

atresia of upper GI tract = polyhydramnios

68
Q

What is a common term for esophageal atresia?

A

blind-ended esophagus

69
Q

Esophageal atresia is caused by

A

abnormal development of laryngotracheal tube

70
Q

Abnormal development of the laryngotracheal tube can lead to (2)

A

esophageal atresia

esophageal stenosis

71
Q

Duodenal atresia or stenosis is cuased by

A

insufficient recanalization of the duodenum at the end of the embryonic period

72
Q

Duodenal atresia/stenosis is commonly found in what grouping of patients?

A

commonly found in children with Down syndrome or other chromosome abnormalities

73
Q

What is polyhydramnios?

A

excess of amniotic fluid in the amniotic cavity

74
Q

What causes polyhydramnios?

A

atresia of upper GI tract

75
Q

List the derivatives of the midgut. (4)

A

small intestine (including most of duodenum)

cecum + vermiform appendix

ascending colon

right 1/2 to 2/3 of transverse colon

76
Q

The midgut derivatives are supplied by

A

the superior mesenteric artery

77
Q

Describe the formation of the midgut loop.

A

midgut elongates and forms ventrally-oriented hairpin loop with cranial + caudal limb

78
Q

Describe the positioning of the superior mesenteric artery with respect to the midgut loop.

A

superior mesenteric artery runs down long axis of midgut loop

79
Q

The cranial portion of the midgut loop develops into

A

most of the small intestine

80
Q

The caudal portion of the midgut loop develops into

A

ascending colon

transverse colon

81
Q

Where does the cecal diverticulum form?

A

forms at apex of caudal portion of midgut loop

82
Q

What is physiologic umbilical herniation?

A

when both limbs of the midgut loop get pushed into the proximal part of the umbilical cord because the abdominal cavity can’t accommodate the fastly-growing midgut

83
Q

In what week does physiologic umbilical herniation occur?

A

week 6

84
Q

Describe the rotations of the midgut loop.

A

while herniated to umbilical cord, midgut loop rotates 90° CCW (viewed from anterior) along axis of superior mesenteric artery

in week 10, midgut returns to abdomen and makes an additional 180° CCW rotation

85
Q

How do the jejunum and ileum form from the midgut loop?

A

during its first 90° CCW rotation, the cranial part of the midgut further elongates to form the jejunum and ileum

86
Q

How does the 180° rotation of the midgut loop affect the cecal diverticulum?

A

180° CCW rotation places cecal diverticulum below the right lobe of the liver

87
Q

Describe the fate of the cecal diverticulum.

A

cecal diverticulum extends caudally and becomes cecum + vermiform appendix

88
Q

What is the most common position of the appendix relative to the cecum?

A

posterior to the cecum (an arrangement called retrocecal appendix)

89
Q

What is a retrocolic appendix?

A

appendix posterior to colon

90
Q

What is a pelvic appendix?

A

appendix positioned ventrally over pelvic brim

91
Q

Describe whether the duodenum, jejunum, ileum, transverse colon, and ascending colon are primarily retroperitoneal, secondarily retroperitoneal, or intraperitoneal. (@)

A

secondarily retroperitoneal = most of duodenum + ascending colon (mesentery resorbed)

intraperitoneal = jejunum + ileum + transverse colon (all retain mesenteries)

92
Q

What is omphalocele? (2)

A

protrusion of abdominal contents through umbilicus into umbilical cord

protruding bowel covered by membranes of umbilical cord

93
Q

What causes omphalocele?

A

occurs when physiological umbilical hernia (forms by week 6 and should retract by week 10) persists

94
Q

How is omphalocele treated?

A

surgery

95
Q

How are umbilical hernias different from omphaloceles?

A

in umbilical hernias, herniating abdominal contents covered by skin

umbilical hernias resolve without surgery

96
Q

What is gastroschisis?

A

protrusion of abdominal contents through defect in (most typically, right) abdominal wall, lateral to the umbilicus

no protective membrane around abdominal contents

97
Q

What is a common consequence of gastroschisis?

A

gangrene (death of tissue due to infection)

98
Q

What is the genetic predisposition of omphalocele? What diseases is omphalocele associated with?

A

minimal genetic predisposition

associated with syndromes, such as trisomy 18

99
Q

What is the genetic predisposition of gastroschisis? What diseases is gastroschisis associated with?

A

minimal genetic predisposition

rarely occurs in syndromes

100
Q

What is malrotation?

A

when midgut rotation is less than a total of 270°

Human Structure - Block 3 (1 decks)

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