Development of the Peritoneum and Foregut Flashcards

1
Q

What kind of folding does the embryo undergo in the fourth week?

A
  • Lateral
  • Craniocaudal
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2
Q

What is the importance of lateral folding of the embryo?

A
  • Creates ventral body wall
  • Primitive gut becomes tubular
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3
Q

Draw a diagram illustrating lateral folding of the embryo.

Label the tubular primitive gut

A
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4
Q

What is the importance of craniocaudal folding of the embryo?

A

Creates cranial and caudal pockets from the yolk sac endoderm

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5
Q

What is the significance of the cranial and caudal pockets of the yolk sac endoderm?

A

It is the beginning of primitive gut development

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6
Q

Draw a diagram illustrating craniocaudal folding of the embryo

A
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7
Q

What is the primitive gut tube lined with?

A

Endoderm

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8
Q

What regions is the primitive gut tube divisible into?

A
  • Foregut
  • Midgut
  • Hindgut
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9
Q

What is the importance of the divisions of the primitive gut tube?

A

They remain fundamental to the anatomy of the adult GI tract, and determine its nerve and blood supply

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10
Q

When does the development of the primitve gut tube begin?

A

In the 3rd week

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11
Q

What is the first step in the development of the primitive fut tube?

A

It ‘pinches off’ from the yolk sac cavity

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12
Q

Where does the primitive gut tube run?

A

From the stomatodeum rostrally to the procotdeum caudally

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13
Q

What is the stomatodeum?

A

Future mouth

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14
Q

What is the proctodeum?

A

Future anusu

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15
Q

Where does the primitive gut tube have an opening?

A

At the umbilicus

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16
Q

What is the opening at the umbilicus in the primitive gut tube called?

A

The vitelline duct

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17
Q

Where does the vitelline duct lead to?

A

The yolk sac

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18
Q

Draw a diagram of the primitive gut tube

A
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19
Q

What is the internal lining of the primitive gut tube derived from?

A

The endoderm (future epithelial linings)

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20
Q

What is the external lining of the primitive gut tube derived from?

A

Splanchnic mesoderm (future musculature, visceral peritoneum)

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21
Q

What is the primitive gut tube suspended in?

A

Intraembryonic coelom

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22
Q

What suspends the primitive gut tube in intraembryonic coelom?

A

A double layer of splanchnic mesoderm

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23
Q

What are the adult derivates of the foregut?

A
  • Oesophagus
  • Stomach
  • Pancreas
  • Liver
  • Gall bladder
  • Duodenum (proximal to entrance of bile duct)
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24
Q

What is the blood supply to the foregut?

A

Celiac trunk

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25
Q

What are the adult derivatives of the midgut?

A
  • Duodenum (distal to entrance of bile duct)
  • Jejenum
  • Ileum
  • Cecum
  • Ascending colon
  • Proximal 2/3 transverse colon
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26
Q

What is the blood supply of the midgut?

A
  • Superior mesenteric artery (SMA)
  • Superior mesenteric vein
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27
Q

What is the parasympathetic innervation of the midgut?

A

Vagus nerve

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28
Q

What is the sympathetic innervation of the midgut?

A

Superior mesenteric ganglion and plexus

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29
Q

What are the adult derivatives of the hindgut?

A
  • Distal 1/3 of transverse colon
  • Descending colon
  • Sigmoid colon
  • Rectum
  • Upper anal canal
  • Internal lining of bladder and urethra
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30
Q

What is the blood supply of the hindgut?

A
  • Inferior mesenteric artery (IMA)
  • Inferior mesenteric vein (IMV)
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31
Q

What is the parasympathetic innervation of the hindgut?

A

Pelvic N. (S2/3/4)

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32
Q

What is the sympathetic innervation of the hindgut?

A

Inferior mesenteric ganglion and plexus

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33
Q

What is the mesoderm surrounding the gut split into?

A

Two layers;

  • Somatic mesoderm
  • Splanchnic mesoderm
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34
Q

What does the somatic mesoderm surrounding the gut develop into?

A

Muscles and fasciae of the abdominal wall

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35
Q

What does the splanchnic mesoderm surrounding the gut develop into?

A

The smooth muscles of the gut wall

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36
Q

What is the space created by the split in the mesoderm surronding the gut called?

A

The coelomic cavity

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37
Q

What is the significance of the coelomic cavity?

A

It is the forerunner of the pleural cavity and peritoneal cavity

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38
Q

What does the coelomic cavity surround?

A

The primitive gut

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39
Q

What happens as lateral folding of the embryo progresses?

A

The two sides of the developing anterolateral abdominal wall meet in the midline, forming the linea alba

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40
Q

How many openings are left once the linea alba has formed?

A

One, at the umbilicus

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41
Q

What is each side of the anterolateral abdominal wall formed of?

A

Three layers of muscle;

  • External oblique
  • Internal oblique
  • Transversus abdominis
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42
Q

What is found anteriorly to the three layers of muscle forming the anterolateral abdominal wall?

A

A fourth muscle, the rectus abdominis

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43
Q

What is found deep to all the muscle layers in the anterolateral abdominal wall?

A

Transversalis fascia

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44
Q

What lies externally to the anterolateral abdominal wall?

A

Superficial fascia and skin

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45
Q

What do the muscles and fascia of the abdoinal wall develop from?

A

Somatic mesoderm

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46
Q

Label this diagram

A
  • A - Rectus abdominis
  • B - Linea alba
  • C - External oblique
  • D - Internal oblique
  • E - Transverse abdominis
  • F - Transversalis fascia
  • G - Peritoneum
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47
Q

What is the inguinal canal?

A

An oblique passage through the layers of the abdominal wall

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48
Q

What is the significance of the inguinal canal in males?

A

It allows the passage of the developing testis into the scrotum

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49
Q

Do the testis pierce the abdominal wall?

A

No

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50
Q

How do the testis get to their final position during development?

A

The abdominal wall pushes them out ahead of its passage

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51
Q

What does the abdominal wall pushing the testes out form?

A

The fascial coverings of the spermatic cord

52
Q

What is the clinical significance of the inguinal canal?

A

It remains a potential site of weakness and hernia formation throughout life

53
Q

What kind of malformation is an umbilical hernia?

A

Congenital

54
Q

What happens in an umbilical hernia?

A

The intestines protrude through the abdominal wall

55
Q

In whom are umbilical hernias common?

A

Babies

56
Q

Why are umbilical hernias common in babies?

A

Because the gut forms outside the abdomen and later returns through an opening that becomes the umbilicus. This opening is a potential site of weakness, so abdominal contents can push against it and herniate

57
Q

What is the inguinal canal?

A

A passage through the layers of the abdominal wall

58
Q

What does the mesoderm surrounding the gut split into?

A

Somatic and splanchnic mesoderm

59
Q

What does the space between the somatic and splanchnic mesoderm form?

A

The coelomic cavity

60
Q

How does the space between the somatic and splanchnic mesoderm form the coelomic cavity?

A

Via lateral folding

61
Q

As what does the intraembryonic coelom begin?

A

One large cavity

62
Q

What later subdivides the intraembryonic coelom?

A

The future diaphragm

63
Q

What does the diaphragm divide the intraembryonic coelom into?

A

The abdominal and thoracic cavities

64
Q

Draw a diagram illustrating the formation of the intraembryonic coelom

A
65
Q

What does the peritoneal membrane do?

A

Lines the abdominal cavity and invests the viscera

66
Q

What happens to the peritoneal membrane during its development?

A

It grows, changes shape, and specialises

67
Q

Why is the peritoneal ‘cavity’ a potential space only?

A

Because under normal conditions, it should contain nothing

68
Q

What is the entire developing gut attached to?

A

The roof of the abdominal cavity

69
Q

How is the developing gut attached to the roof of the abdominal cavity?

A

By a fold of mesoderm known as the dorsal mesentery

70
Q

What attaches to the floor of the abdominal cavity?

A

The foregut

71
Q

How is the foregut attached to the floor of the abdominal cavity?

A

Ventral mesentery

72
Q

Draw a diagram illustrating the attachments between the developing gut and the abdominal cavity

A
73
Q

What do the dorsal and ventral mesenteries become?

A

The various peritoneal folds and reflections that suspend the gut and give passage to the vessels and nerves in the adult

74
Q

What happens to the shape of the dorsal and ventral mesenteries?

A

They often become complex

75
Q

Why does the shape of the dorsal and ventral mesenteries often become complex?

A

Due to the complexity of the changes in shape and position undergone by the developing gut

76
Q

What do the dorsal and ventral mesenteries in the region of the foregut do?

A

Divide the cavity into left and right sacs

77
Q

What does the left sac of the preitoneal cavity contribute to?

A

The greater peritoneal sac

78
Q

What does the right sac of the peritoneal cavity contribute to?

A

The lesser peritoneal sac

79
Q

Where does the lesser peritoneal sac come to lie?

A

Behind the stomach

80
Q

Draw a diagram illustrating the greater and lesser peritoneal sacs, and the mesentery dividing them

A
81
Q

What are the greater and lesser omenta?

A

Specialised regions of peritoneum

82
Q

What is the greater omentum formed from?

A

The dorsal mesentery of the stomach

83
Q

When would the greater omentum be the first structure to be seen?

A

When the abdominal cavity is opened anteriorly

84
Q

What does the greater omentum connect?

A

The greater curve of the stomach to the transverse colon

85
Q

What is the lesser omentum formed from?

A

The ventral mesentery of the stomach

86
Q

What does the lessr omentum connect?

A

The lesser curve of the stomach to the liver

87
Q

What are the greater and lesser sacs, and the omenta formed by?

A

The rotation of the stomach

88
Q

What is the widest part of the foregut?

A

The stomach

89
Q

How does the shape of the stomach change during development?

A

Initially, it is symmetrical, and then as it enlarges in expands unevenly, mainly towards the left

90
Q

What creates the greater curvature of the stomach?

A

The faster growth of the dorsal border

91
Q

In what manner does the primitive stomach rotate?

A

In two directions, around the longitudinal axis and around the anteroposterior axis

92
Q

What is the result of stomach rotation?

A
  • The original left side becomes anterior
  • The original right side becomes posterior
  • Vagus nerves lie anterior and posterior instead of left and right
  • Shifts cardia and pylorus from the midline, pushing the greater curve inferiorly
  • Moves the lesser sac behind the stomach
  • Creates the greater omentum
93
Q

Draw a diagram illustrating the longitudinal rotation of the stomach

A
94
Q

Draw a diagram illustrating the anteroposterior rotation of the stomach

A
95
Q

What is peritoneal reflection?

A

A change in direction, from parietal peritoneum to mesentery, from mesentery to visceral peritoneum etc

96
Q

Draw a diagram illustrating peritoneal reflection

A
97
Q

Give two parts of the GI tract that remain suspended from the posterior abdominal wall?

A
  • The jejenum
  • The ileum
98
Q

How do some parts of the GI tract remain suspended from the posterior abdominal wall?

A

By mesentery

99
Q

What is the consequence of some parts of the GI tract remaining suspended from the psoterior abdominal wall?

A

They remain mobile

100
Q

What are structures that are not suspended within the abdominal cavity called?

A

Retroperitoneal

101
Q

What is meant by retroperitoneal?

A

Were never in the peritoneal cavity and never had mesentery

102
Q

Give 3 examples of structures that are retroperitoneal

A
  • Aorta
  • Vena cava
  • Kidneys
103
Q

What is meant by secondary retroperitoneal?

A

Began development invested by peritoneum, and had mesentery, but with successive growth and development, the mesentery is lost through fusion with the posterior abdominal wall

104
Q

Give three examples of structures that are secondary retroperitoneal

A
  • Ascending colon
  • Descending colon
  • Duodenum
105
Q

What happens to the duodenum and its mesentery during development?

A

It is pushed against the posterior abdominal wall

106
Q

Why is the duodenum and its mesentery pushed against the posterior abdominal wall during development?

A

Due to the rotation of the stomach and the large size of the liver

107
Q

What produces fusion fascia?

A

The peritoneum of posteiror abdominal wall is ‘squished together’ with the duodenum and its mesentery, growing over it

108
Q

Is fusion fascia vascular or avascular?

A

Avascular

109
Q

What is the consequence of fusion fascia being avascular?

A

You can remove it to make the duodenum mobile again without causing any damage

110
Q

When does a respiratory diverticulum form?

A

In the 4th week

111
Q

Where does a respiratory diverticulum form?

A

In the ventral wall of the foregut at the junction with the pharyngeal gut

112
Q

What does the respiratory diverticulum become?

A
  • The respiratory primordium ventrally
  • The oesophagus dorsally
113
Q

What divides the respiratory primordium and the oesophagus?

A

The tracheoesophageal septum

114
Q

Draw diagrams illustrating the formation of the respiratory primordium and the oesophagus

A
115
Q

What is the prevelance of oesophageal abnormalities?

A

Up to 1 in 3,000 live births

116
Q

Draw a diagram illustrating the potential consequences of abnormal positioning of the tracheoesophageal septum?

A
117
Q

Where are the foregut derived glands formed?

A
  • In the ventral mesentery
  • In the dorsal mesentery
118
Q

What foregut derived glands are formed in the ventral mesentery?

A
  • Liver
  • Biliary system
  • Part of pancreas (ucinate process and inferior head)
119
Q

What foregut derived glands are formed in the dorsal mesentery?

A

Pancreas (superior head, neck, body, and tail)

120
Q

What is the earliest GI tract associated gland?

A

The liver

121
Q

What does the liver develop from?

A

The hepatic bud within the ventral mesentery

122
Q

What is the significance of the liver during development?

WIth regards to space

A

It occupies a large proportion of the abdomen

123
Q

Draw a diagram illustrating the development of the liver

A
124
Q

What happens to the lumen of the duodenum in the 5th and 6th weeks?

A

It is obliterated due to the lining growing so quickly

125
Q

What happens to the duodenum by the end of the embryonic period?

A

It is recanalised

126
Q

What is the effect of the rotation of the stomach on the duodenum?

A

It pushes it to the right, then back against the posterior abdominal wall

127
Q

Label this diagram

A
  • A - Bare area
  • B - Falciform ligament
  • C - Lesser omentum