Embryology 6 - Digestive System

Front 1

Through what kind of foldings is the primitive gut tube formed?

Back 1

Longitudinal - Head & Tail foldings

Transverse folding

Front 2

When is the primitive gut tube formed (the week of development)?

Back 2

4th week of development

Front 3

What are the subdivisions of the primitive gut?

Back 3

- foregut, midgut, hindgut

Front 4

What are two kinds of mesenteries and what parts to they connect?

Back 4

- Ventral and Dorsal mesentery

- Ventral: connects only the FOREGUT to the anterior abdominal wall

- Dorsal: connects the foregut, midgut and hindgut to the posterior abdominal wall

Front 5

What is cloaca?

Back 5

Cloaca is the part at the end of the primitive hindgut.

Front 6

What separates the cloaca (sewer) and proctodeum?

Back 6

cloacal membrane

Front 7

What does cloacal membrane separates?

Back 7

cloaca and proctodeum

Front 8

What is vitelline duct?

Back 8

- this develops into the yolk stalk, which connects primitive mesoderm (endoderm) to the yolk sac

Front 9

What is another name for ventral mesentery?

Back 9

Septum transversum

Front 10

What lines and supports the primitive gut tube?

Back 10

- endoderm

- splanchnic mesentery

Front 11

What does splanchnic mesentery provide to the primitive gut tube?

Back 11

- blood vessesls, connective tissue and smooth muscles associated with the gut

Front 12

What does endoderm forms in the gut tube?

Back 12

- lining of the digestive tract (epithelium )

- lining of the outgrowth of the digestive tract (respiratory system)

- parenchyma cells (secretory cells) that outgrows from the digestive system - lung, pancreas, and gall bladder

Front 13

When does vellitine duct disappears?

Back 13

5th - 6th week of development

Front 14

What is the remnant of the vellitine duct, when it does not disappear?

Back 14

Meckel's diverticulum

Front 15

Tell me about the Meckel's diverticulum (numeric)

Back 15

2% in population

twice as common in males

2 feet from the ileocecal junction

2 inches long

Front 16

What are four uncommon conditions due to vetelline duct being remained?

Back 16

1. opened tube -> umbilical fistula

2. distal part is opened -> deep belly button; this traps the bacteria causing infection

3. medial part is opened -> forms a cyst

4. all collapsed but still connected to ileum -> limits the movement of the ileum

Front 17

What is SO special about the endoderm and what is the problem of that being special?

Back 17

- endoderm can form into anything

- When endoderm remains in the digestive tract, such as Meckel's diverticulum, this develops into anything (pancreatic or gastric tissues) that secrete HCl and pancreatic tissue. However, the ileum is not grown to stand HCl and pancreati

Front 18

What other diverticulae and cysts are formed other than Meckel's diverticulum? How are they formed?

Back 18

- when the notochord (mesoderm) fails to separate from the endoderm, the vertebral column and gut tube are connected to each other.

- This forms a diverticulae. If only the distal and proximal part of the diverticulae are collapsed, it forms a cyst.

- This cyst becomes a tumor

Front 19

What are the derivatives of the foregut?

Back 19

- Respiratory tree from larynx and alveoli

- esophagus

- stomach

- duodenum before the cystic duct

- liver, pancreas, gall bladder

Front 20

What are the 8 steps of the foregut development?

Back 20

1. outgrowth of the larynotracheal ligament to from the respiratory system

2. foregut dilation

3. elongation of foregut to push the forgut into the abdominal cavity from the heart

4. proliferation of the endoderm at the proximal and distal part of the dilated foregut

5. recanalization occurs by the cavitation of the proximal and distal part of the foregut

6. Shaping of the stomach - the dorsal border of the stomach moves to LEFT.

- dorsal mesentery forms the greater omentum (horizontal), splenorenal ligament, gastrosplenic ligament (vertical)

- ventral mesentery forms the lesser omentum, Glisson's capsule, peritoneal lining of the liver and liver's ligament (coronal, triangular and falciform ligament)

7. the dorsal part of the stomach elongates more rapidly to from greater curvature

8. outgrowth of liver, pancreas and gall bladder

Front 21

What happens if the cavitation does not occur properly?

Back 21

- the foregut is partially (stenosis) or fully closed (atresia)

Front 22

The derivatives of the midgut?

Back 22

1. duodenum distal to the common bile duct

2. jejunum & ileum

3. cecum & appendix

4. ascending colon

5. proximal part of the transverse colon

Front 23

The steps of the midgut formation?

Back 23

1. umbilical herniation - the midgut elongates and moves into the umbilical cord (6th week)

2. Elongation of the proximal part of the midgut forms the coils of the small intestine & 90 degree counter-clockwise rotation

3. The proximal part of the midgut returns to the abdominal cavity and pushes the hindgut to the LEFT & 180 degrees counter-clockwise rotation puts the duodenal-jejunal junction in the adult position. (10th week)

4. Elongation of the distal part of the midgut pushes the cecum from sub-hepatic position to the right iliac fossa.

Front 24

When is the umbilical herniation occur?

Back 24

6th week

Front 25

When do the proximal part of the midgut returns to the abdominal cavity?

Back 25

10th week of the development

Front 26

in total of what angle, does the midgut turn?

Back 26

270 degrees counter-clockwise rotation

Front 27

How is the cecum moved from the sub-hepatic position to the right iliac fossa?

Back 27

Through further elongation of distal part of the midgut

Front 28

Due to further elongation of the distal part of the midgut, where does cecum end up in?

Back 28

right iliac fossa

Front 29

What happens if the midgut fails to rotate at 180 as it returns to the abdominal cavity?

Back 29

The SI stays in the right side and LI stays in the left side but this does not cause a problem

Front 30

What is omphalocele?

Back 30

This is a condition when the midgut fails to return. The midgut is covered with the amniotic membrane.

Treatment: the surgeon moves the midgut back to the abdominal cavity. However, the surgery has to be done several times to wait until the abdominal cavity grows enough to receive the midgut.

- If the surgery was done at once, the baby's diaphragm starts to fall and makes the baby hard to breathe.

Front 31

What is the gastroschisis? Treatment?

Back 31

When the midgut comes out of the umbilical cord and exposed to the amniotic fluid. This causes the midgut to be fibrous, which limits the mobility of the midgut

Treatment: the surgeon cuts part of the midgut and anastomoses with a good fit -> this cause the baby to have a short gut