Lecture 14: Embryology of the Gut Flashcards Preview

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Flashcards in Lecture 14: Embryology of the Gut Deck (116):
1

What are the two foldings involved in primitive gut formation

Later folding and cephalo-caudal folding

2

What primary get layers makes up the gut?

Endoderm

3

What are structural derivatives of the ectoderm?

Skin and nervous system

4

What are structural derivatives of the mesoderm?

CT, cartilage, muscle, bone, and blood

5

What are the directions for the cephalic-caudal and lateral plate mesoderm folds?

Cepalo-caudal- inwards
Lateral plate mesoderm- lateral
*both form the body wall and body because the head and tail region become distinct from one another*

6

As these two folds in the embryo occur, a big space develops, what is that called?

Intraembryonic coelomic cavity

7

What are the 3 body cavities derived in the intraembryonic coelomic cavity in the adult

Pleural cavity, pericardial, peritioneal cavity

8

Compare the size of the embryo peritoneal cavity to the adult

Embryo is much larger than the adult due to the growth of the organs

9

Significant structures that arise from the folding of the lateral plate mesoderm in the adult

Visceral and parietal paritoneum

10

How is the primitive gut separated from the yolk sac

Lateral and cephalo-caudal folding

11

Will a connection between the yolk sac and the primitive gut still exist after folding? If so how?

Yes because the yolk stalk (vitaline duct or omphalomesenteric duct) remains connected but continues to narrow with time

12

What structures will become a part of the forgut?

Forms pharynx, esophagus, stomach, proximal half duodenum, liver, pancreas, gal bladder, lower respirtory system

13

What structures will become a part of the midgut

Forms distal duodeum, jejunum, illeum, large intestine up to proximal 2/3 of transverse colon

14

What is the midgut region connected to in the embryo

Yolk sac

15

What structures will become a part of the hindgut

Forms the lateral 1/3 of transverse colon, descending colon, sigmoid colon, rectum, gut part of anal canal

16

Allantois

Membrane that becomes incorporated into the embryo (in the hindgut region) and participates in the formation of the cloaca

17

How is the gut attaches to the back body wall?

Dorsal mesentery

18

Describe how the dorsal mesentery is formed

The cephalo-caudal and lateral foldings divides the mesoderm into the somatic (on the body) and splanchnic mesoderm (on the gut). The dorsal mesentery is a double layer fold of splanchnic mesoderm

19

Other than the dorsal mesentery, what else is derived from the splanchnic mesoderm?

Smooth muscle of GI tract

20

What organs are suspended by the dorsal mesentery

Every gut organs

21

What is the space between the somatic and splanchnic mesoderm called

Intraembryonic coelomic cavity

22

The ventral mesentery grows very early, what happens to the ventral mesentery when the liver begins to grow

The liver divides the mesentery into 2 parts- the falciform ligament and lesser omentum

23

What are two structural derivatives of the dorsal mesentery

Falciform ligament and lesser omentum

24

Where is the ventral mesentery present?

forgut (unlike dorsal mesentery)

25

What mesoderm derive the parietal and viscera paritoneum

Parietal- Somatic mesoderm
Visceral- Splanchnic mesoderm

26

What does the diaphragm separate

Thorax from abdomen

27

Describe the role of mesenchymal cells in diaphragm and ventral mesentery formation

There is a sheet of mesenchyme cells (undiff. cells) with a top and bottom
-top part forms the diaphragm and the bottom part forms the ventral mesentary.

28

How many different parts form the diaphragm

4

29

What are the different parts that form the diaphragm

1. Septum transversum
2. Pleuroperitoneal folds
3. Mesentery of esophagus
4. Skeletal muscle cells

30

What portion of the diaphragm does the septum transversum create?

The anteriolateral region of diaphragm including central tendon

31

Describe the movement of the septum transversum with spinal/vertebral cord levels

Initially lies opposite to Spinal cord levels C3,4, and 5 in the embryo then descents to vertebral level L1, taking the phrenic nerve with it

32

Does the septum transverse completely close of the thorax and abdomen

no

33

Role of the pleuroperitoneal folds

Close off the posteriolateral gaps in the diaphragm (called pericardioparitoneal canals)

34

Where do the pleuroperitoneal folds originate and where do they extend?

They originate from the caudal border of pleural cavities then grow to meet each other and the septum transversum

35

What entraps the dorsal mesentery of the esophagus

the pleuroperitoneal folds and septum transverse

36

What is another name for the dorsal mesentery of the esophagus

mesoesophagus

37

Where does the cura of the diaphragm develop

mesoesophagus

38

Where is most of the muscle on the diaphragm located

At there periphery

39

What is the embryonic derivative of the skeletal muscle in the diaphragm

mesenchymal cells

40

Where does all of the muscle on the diaphragm attach

Central tendon

41

How do Diaphragmatic hernias result?

Failure of closing the pleuorperitoneal folds

42

What's the consequence of diaphragmatic hernias?

The pericardioperitoneal canals remain open, allowing abdominal visceral to move into the thorax interfering with lung maturation

43

What does the forgot form in the embryo

pharyngeal pouches, esophagus, trachea, lung buds, stomach, liver, bilary system, and pancreas

44

What is the blood supply for all forget organs

Celiac trunk

45

How does the esophagus develop?

Out pocketing of the respiratory or tracheobronchial divriticulum from its ventral wall

46

Why is out pocketing of the tracheobronchial divriticulum necessary

To ensure the completion of the esophagotracheal septum

47

What is the esophagotracheal septum

Separates the esophagus (pathway for food) from the trachea (pathway for air)

48

What is the last structure to form in the lungs

Alveoli (site of gas exchange)

49

How do the alveoli develop

The tracheobronchial divriticulum interacts with the mesoderm

50

Atrasia of esophagus

When the esophagus is not connected at the point where the esophagus is shut off from the trachea. Causing babies to spit up their food

51

Esophageotracheal fistula

The esophagus and trachea are not closed off from one another causing lots of gas to enter the stomach

52

Does the esophagus have a mesentary

Yes the dorsal mesentery of the esophagus or mesoesophagus

53

what structure develops in the dorsal mesentery of esophagus?

Diaphragmatic cura

54

What two mesenteries are contained within the stomach

The dorsal and ventral mesentery (called dorsal and ventral mesgastrum for stomach)

55

What is the ventral mesogastrum formed by

septum transversum

56

How is the mental bursa formed

In gut development- the rotation and uneven growth in the dorsal mesgastrum for the stomach to bend to the left making the mental bursa

57

How is the great omentum formed in embryonic development

The dorsal mesgastrum grows in the caudal direction as the stomach rotates along its anterior posterior axis to form greater omentum

58

Compare the great omentum in the embryo v.s the adult.

In the embryo the greater omentum is open to the mental bursa. In the adult the visceral layers of the greater omentum fuse and close off this connection (this occurs because the transverse colon is growing and pushes until the omental bursa is partially shut off)

59

What happens when the stomach rotates 90 degrees

Puts the left vagus n. on the anterior portion of the stomach and esophagus and the right vagus n. on the posterior esophagus and stomach (this is how it is in the adult)

60

What is the orientation of the 2 vagus nerves (left and right) on the embryonic gut?

They were on their respective sides (left and right)

61

After the stomach has undergone rotation how does it lay?

Horizontally

62

Where are the cardiac oriface and pyloric oriface oriented?

Cardiac oriface- Left
Pyloric oriface- Right

63

What does the forgot portion of the duodenum give rise to?

Hepatic diverticulum, bilary system, and pancreatic diverticulum

64

What causes the duodenum to loose its mesentery

The rotation of the gut causes the duodenum to be pushed against the posterior back wall

65

Difference between the duodenum in adult verse embryo (other than the fact that the embryo is a straight pole)

The duodenum in the adult is both forgut and hindgut- however, in the embryo that all act as a cohesive unit

66

What is another name for the hepatic diverticulum

liver bud

67

Where does the liver bud form from?

Caudal portion of forgut

68

How are liver cords formed

The liver buds invade the septum transversum

69

What gives rise to the gallbladder?

The attachment of the hepatic diverticulum to the duodenum then narrows to form the bile duct which in turn gives rise to the glalbladder

70

How is the ventral mesentery divided into the falciform ligament and the lesser omentum?

Growth of the liver into the septum transversum

71

How does the hepatic portal vein, hepatic artery, and common bile duct reach the liver?

Through caudal margin of lesser omentum

72

What action displaces the stomach to the left

The downward growth of the liver

73

How many pancreatic diverticula develop and where

2 develop in the duodenal region

74

What are the names of the 2 pancreatic diverticulum

dorsal and ventral pancreatic buds

75

What embryonic events cause the dorsal and ventral pancreatic buds to fuse together

Growth of liver and stomach causes the duodenum to get pushed back to the posterior body wall (forming C-shaped loop) causing the buds to come together and fuse on to back wall (thus the pancreas becomes secondarily retroperitoneal)

76

What parts of the pancreas are derived from the ventral pancreatic bud

The head and uncinate process

77

What is the uncinate process

A part of pancreas that the superior and inferior mesenteric arteries pierce

78

What are the ventral and dorsal pancreatic buds attached to

Ventral- Common bile duct
Dorsal- Duodenum

79

What derives from the dorsal pancreatic bud

the body and tail of pancreas

80

Annular pancreas

When the ventral pancreatic bud constricts the duodenum by forming a ring around it

81

Is the spleen a forgot derivative?

No

82

How does the spleen develop

Forms from cells in the dorsal mesentery

83

Since the dorsal mesentery pushes the spleen against the posterior wall is it secondarily retroperitoneal?

No, it remains in the dorsal mesentery

84

How is the spleen suspended by the back wall?

Leinorenal ligament (splenorenal ligament)

85

How is the spleen attached to the stomach

Gatsrosplenic ligament

86

What ligaments for the lateral wall of the dorsal mesentery

The leinorenal (splenorenal) ligament and gastrosplenic ligament

87

Where does the midgut region begin

Just caudal to where the common bile duct enters the duodenum

88

Where does the midgut initially develop

In the extraembryoic coelomic space in the umbilical cord

89

Why does the midgut form in the umbilical cord?

Because of the rapid growth of the liver (needs more room)

90

What is it called when a structure (such as the intestines) leave the body (into say the umbilical cord)

Herniation

91

Midgut rotation sequence

The midgut rotates 90 degrees counterclockwise about the superior mesenteric a. allowing the cecum to develop at the junction of the large and small intestine (remains attached to yolk sac during this)

92

When is the connection between the midgut and yolk sac gone?

When the midgut is retracted into the abdomen

93

If the connection between the midgut and yolk sac is not eradicated properly, what abnormalities occur

Meckel's Diverticulum, Vitelline fistula, and Vitelline cyst

94

What is the disorder vitelline fistula?

Persistent connection between the ileum and vitelline

95

What are Meckel's Diverticulum and Vitelline cyst?

Presence of vitelline ligaments to umbilicus

96

When the midgut returns to the abdominal cavity, how many more degrees does it rotate

180 degrees counterclockwise around SMA

97

What portion of the midgut returns to the abdomen first

small intestine

98

Where does the small intestine go once it reaches the abdomen

To the left and under the SMA

99

Where does the cecum go once the small intestine has entered the abdomen

To the left (initially) then to the right to sit in the right iliac fossa

100

Omphalocoele

Results from the failure of the gut to return to the abdomen

101

Malformation in midgut rotations

Duodenum could be infront of the transverse colon, v.s behind

102

Where does the mesentery proper attach

Back wall in a left right fashion

103

Where does the terminal portion of the hindgut enter

cloaca

104

What is the cloaca

Common changer for feces and urine in the embryo

105

What are the 2 divisions of the cloaca

urogenital sinus and anorectal canal (purpose: urine and feces are separated)

106

What is the structure that divides the cloaca into its 2 divisions

urorectal septum

107

List the forgut derivatives

Pharynx, lungs, bronchi, trachea, esophagus, stomach, superior and descending duodenum, gallbladder, and pancreas

108

Arterial supply for all forget organs?

Celiac trunk

109

List all midgut derivatives

Horizontal and Ascending duodenum, jejunum, ileum, ascending colon, proximal 2/3 transverse colon

110

Arterial supply to midgut organs

Superior mesenteric a

111

List all hindgut derivatives

Lateral 1/3 of transverse colon, descending colon, sigmoid colon, rectum, anal canal to pectinate line

112

Arterial supply to hindgut

inferior mesenteric a

113

Derivatives of ventral mesentery

lesser omentum and falciform ligament

114

What are the two ligaments that make up the lesser omentum?

Hepatoduodenal ligament and hepatogastric ligament

115

Derivatives of the dorsal mesentery

-Greater omentum
-Lienorenal (splenorenal) ligament
-Mesentery of jejunum and ileum
-Transverse and Sigmoid mesocolon
-Mesoduodenum (lost in adult)

116

What are the 3 different ligaments that make up the greater omentum

Gastrocolic, gastrosplenic, Gastorphrenic ligaments