Lecture 14: Embryology of the Gut Flashcards

(116 cards)

1
Q

What are the two foldings involved in primitive gut formation

A

Later folding and cephalo-caudal folding

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2
Q

What primary get layers makes up the gut?

A

Endoderm

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3
Q

What are structural derivatives of the ectoderm?

A

Skin and nervous system

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4
Q

What are structural derivatives of the mesoderm?

A

CT, cartilage, muscle, bone, and blood

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5
Q

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

A

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

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6
Q

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

A

Intraembryonic coelomic cavity

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7
Q

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

A

Pleural cavity, pericardial, peritioneal cavity

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8
Q

Compare the size of the embryo peritoneal cavity to the adult

A

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

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9
Q

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

A

Visceral and parietal paritoneum

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10
Q

How is the primitive gut separated from the yolk sac

A

Lateral and cephalo-caudal folding

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11
Q

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

A

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

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12
Q

What structures will become a part of the forgut?

A

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

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13
Q

What structures will become a part of the midgut

A

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

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14
Q

What is the midgut region connected to in the embryo

A

Yolk sac

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15
Q

What structures will become a part of the hindgut

A

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

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16
Q

Allantois

A

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

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17
Q

How is the gut attaches to the back body wall?

A

Dorsal mesentery

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18
Q

Describe how the dorsal mesentery is formed

A

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

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19
Q

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

A

Smooth muscle of GI tract

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20
Q

What organs are suspended by the dorsal mesentery

A

Every gut organs

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21
Q

What is the space between the somatic and splanchnic mesoderm called

A

Intraembryonic coelomic cavity

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22
Q

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

A

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

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23
Q

What are two structural derivatives of the dorsal mesentery

A

Falciform ligament and lesser omentum

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24
Q

Where is the ventral mesentery present?

A

forgut (unlike dorsal mesentery)

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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