Embro: Digestive System and Peritoneal Membranes Flashcards
1
Q
What are the 4 germ layers found in the GI system?
A
1. Endoderm
2. Splanchnic mesoderm
3. Neural crest cells
4. Ectoderm
2
Q
The digestive system is made up of endoderm, ectoderm, splanchnic mesderm and NCC.
What does the endoderm make?
A
All epithelium, except the mouth and anal canal.
3
Q
The digestive system is made up of endoderm, ectoderm, splanchnic mesderm and NCC.
What does the ectoderm make?
A
- Mouth (from the 1st arch)
- Anal canal
4
Q
The digestive system is made up of endoderm, ectoderm, splanchnic mesderm and NCC.
What does the splanchnic mesoderm make?
A
- Smooth muscle
- Connective tissue
5
Q
The digestive system is made up of endoderm, ectoderm, splanchnic mesderm and NCC.
What does the NCC make?
A
Autonomic ganglia
6
Q
The endoderm is divided into three sections, the foregut, midgut and hingut. What divides them into sections?
A
yolk sac
7
Q
What is made from foregut? (7)
A
- Pharynx
- ESO
- Respiratory system
- stomach
- Liver/pancreas
- Biliary apparatus
- Proximal duodenum
8
Q
What is made from midgut? (4)
A
- SI, starting at the major duodenal papilla of the duodenum
- Cecum and appendix
- Ascending colon
- Right half of the transverse colon
9
Q
What is made from hindgut? (5)
A
- left half of transverse colon,
- descending colon,
- sigmoid colon,
- rectum,
- superior anal canal
10
Q
What are the main vessesl for foregut, midgut and hindgut?
A
celiac
superior mesenteric artery
inferior mesenteric artery
11
Q
TE fistula abnormality: what happens?
A
-
Failure of the tracheoesophogeal folds –> midline–> and form the tracheoesophogeal septum at week 5.
*
12
Q
What are the two types of TE fistula?
A
- Esophageal atresia--> blind end ESO
- TE fistual–> abnormal passage between trachea and ESO
13
Q
Where does the skeletal and smooth muscle of the esophagus come from?
A
skeletal–> mesoderm of the pharyngeal arch 4/6
smooth–> splanchnic layer of lateral plate
14
Q
What is the best cause for TE fistula prenatally and what can be seen at birth?(6)
Remember this can be diagnosed by seeing coiling of a NG tube
A
Prenatally: polyhydramnios
Birth: coughing, gagging, cyanosis, vomiting, drooling
15
Q
During the 4th week the stomach grows, faster on the dorsal surface.
How does it rotate and what are the degrees?
A
@ wk 4:
- Stomach grows faster on the dorsal surface, growing larger and forming an out-pocket.
- Rotate 90 on its longitudinal axis
- Ventral part–> right
- Right part–> dorsal
- Dorsal part–> left
- Left part–> ventral
- Rotation occurs at the AP axis
- cranial end goes inferior and to the left
- Inferior end goes superior and to the right
16
Q
Hypertrophic pyloric stenosis is very common, is when circular and some longitudinal muscles of the pylorus hypertrophy. What is the presentation? (3)
A
- immediate PROJECTILE vomiting that is nonbilious right after eating
- Small stool
- Cannot gain weight–> may lose weight
17
Q
What vertebral level/ plane is the pylorus of the stomach at?
A
L1
18
Q
Hepatic diverticulum gives rise to what 3 things?
A
liver, gallbladder and ventral pancreatic bud
19
Q
In reference to the SEPTUM TRANSVERSUM, where do the liver and GB form?
A
Liver grows superiorly of the septum transversum.
GP splits off and will then fuse to the liver
20
Q
Stroma and other cells (cupler cells) in the liver come from where?
A
mesoderm
21
Q
Liver and biliary system all come from where?
A
SINGLE DIVERTICULUM: HEPTATIC DIVERTICULUM
22
Q
- Liver is a ______ organ: makes _____.
- Bile is made by wk ____.
- Hematopeisis: occurs during wk___- wk___
- hematopoetic cells come from ______
A
Liver is a hematopoetic organ: makes RBC.
Bile is made by wk 12.
Hemtopeisis: wk6- wk 30
hematopoetic cells come from mesoderm
23
Q
How does the pancreas form?
A
The pancreas begins as two buds: ventral pancreatic bud (from the hepatic diverticulum) and the dorsal pancreatic bud.
- Duodenum rotates right–> moving the VPB dorsally
- VPB will fuse with the DPB
- Ventral primordia will make the [head and uncinate process]
- Dorsal primordia will make [some of the head and tail]
24
Q
What does the main pancreatic duct make?
A
ventral duct
25
What is **annular pancreas,** which presents with similar symptoms as pyloric stenosis except with **bilious vomit** if it is below the bile duct, without if it is above bile duct?
there is a **_bifed ventral pancreatic bud_**,
which wraps around the duodenum and obstructs it.
many patients are asymptionic tho
26
What determines if the annular pancreas will produce bilious vommitting?
Depends on the location of the stenosis
27
1. If stenosis is superior to the major duodenal papilla—\> bile in vomit?
2. If below—\>?
3. If What if stenosis in third part of duodenum?
1. N
2. Y
3. Y
28
\*\*\*\*Spleen is made from ____________ at week \_\_\_.
What is the purpose of the spleen?\*\*\*\*\*\*
* foregut **MESODERM**
* Week 5
* hematopoeitic organ that helps make RBC from wk 9-28
29
Midgut is continouus with the \_\_\_\_\_\_\_\_\_\_\_, which later becomes obliterated extends
to the \_\_\_\_\_\_\_\_\_
**vitelline duct,** which later becomes obliterated and extends to the **umbilicis**.
30
**Development of midgut (5 steps)**
1. **At week 6**: Midgut leaves the abdomen--\> body stalk, causing the SMA to herniates to the umbilical cord d/t big LIVER and kidneys
2. Rotates 90 degrees.
3. distal part develops a bulge—\> cecum
cranial part becomes convulted—\> SI
Caudal part—\> LI
4. **At week 10**: Proximal part returns first because abdoment gets bigger
5. Rotates 180, for a total of 270 degrees
31
A distal/caudal bulge occurs where the cecum is and the proximal SI becomes convoluted. What is the final rotation back in during week 10?
180 degrees, the proximal (SI) part moves under the distal part (LI) to get to its mature spot (270 degress total)
32
What is **omphalocele** which occurs during **week 10**?
* failure of bowel to return to the body cavity,
* bowel will be covered in amnion and peritoneum (only 90 degrees rotation occurs)
33
What is **gastroschisis** which occurs during **week 4?**
**anterior abdominal wall** doesnt close, bowel exposed without peitoneum (occurs in nebraska).
usually occurs on RIGHT side
34
**_Hirschsprungs disease_ or megacolon occurs is the MOST COMMON cause of neonatal obstruction due to?**
* NCC fail to migrate to distal colon, lack ganglion cells below to enlarged segment (no parasympathetics)
* that enlarged section is normal
35
Congential umbilical hernia s different from omphalocele; because...
weaking of the abdominal wall d/t increased abdominal
pressure, umbilical contents herniate out.
36
**Midgut can under non-rotation and reversed rotation.**
**What is non-rotation?**
Midgut does not rotate 90 as it leaves the abdomen. Thus, SI is on R side and LI is on the L side. higher likelihood of obstruction
37
**Midgut can under non-rotation and reversed rotation.**
**What is reversed-rotation?**
* Reversed rotation- as herniating back into abdomen, rotating in opp direction.
* Transverse colon is behind to duodenum (not anterior).
* The duod can then cause an obstruction in the TC.
38
**How do we form the lumen of the GI tract?**
What 2 things can happen if it goes wrong?
* start with hollow gut tube—\> endothelial cells fill the tube—\> apoptosis occurs and recanilization occurs—\> forms the lumen.
* if not correctly done—\> **duplication**; pouch is formed and food can get inside. or we can get a **stenosis**, apoptosis did not occur and get a narrowing of the canal
39
**What is Meckel's diverticulum?**
* **Vitilline duct forms a persistant attachment to the umbilicis and pulls on the ileum to the abdominal wall, creating a pouch called Meckel's diverticulum.**
40
**What rule does Meckels diverticulum follow?**
**RULE OF 2s:**
## Footnote
1. 2x more likely in M
2. 2% of population
3. Pouch is 2 inches long
4. 2 feet from ileocecal junction
5. 2 types of ectopic tissue: gastric and pancreatic
6. Dx at 2 years old
41
**Sx of Meckels diverticulum**
1. **intestinal obstruction**
2. **GI bleeding**
3. **bowel sepsis**
42
The **hindgut** is going to be made from what
**1. Urorectal septum**
**2. Cloacha**
**3. Cloachal membrane**
43
**What type of tissue is urorectal septum?**
**mesoderm**
44
**how do we form our _hindgut_?**
1. **Urorectal septum** (from mesoderm) will come down and seperate the **cloachal membrane** into two things: **urogenital membrane and anal membrane.**
45
1. Urorectal septum(from mesoderm) will come down and seperate the cloachal membraneinto two things:urogenital membrane and anal membrane.
**What tissue is our urogenital membrane and anal membrane from?**
**ectoderm and endoderm**
46
**What does the urogenital membrane and anal membrane make?**
1. Urogenital membrane--\> bladder and urethra
2. anal membrane--\> anal canal
47
***_Anal canal_* comes from what embroyological sources?**
* **2 different embryo sources with different BS, nerves and lymphatics**
* **1. _Hindgut_ makes the first 2/3**
* **2. _Ectoderm_ makes the lower 1/3**
48
First 2/3 of anal canal is from hindgut and located above the **pectinate line.**
BS
Nerves
lymphatics
* *BS:** inferior mesenteric a
* *nerves:** Autonomics. no pain felt here.
* *lymphatics-** inferior mesenteric LN
49
**Last 1/3 of anal canal is from _ectoderm from PROCTODEUM_ located below the pectinate line.**
BS
Nerves
lymphatics
* *BS:** middle and inferior rectal a
* *N:** pudendal n (a somatic nerve under voluntary control. pain can be felt here.
* *lymphatics:** superficial inguinal LN
50
**To form the anal canal, what 2 things must happen?**
**what happens if they dont?**
1. endoderm and ectoderm layers must meet at the right place to form the anal canal
2. urorectal septum must migrate and separate the cloaca
if they dont: anorectal malformations
51
To form the **peritoneal cavity**, what must occur?
**septum transversum** fuses with the **pleuroperitoneal membrane** (somatic layer of the lateral plate), forming the diaphragm.
52
To close the **pericardioperitoneal canal**, what occurs?
* after the septum transversum and pleuroperitoneal membrane fuse, tissue body from the wall is pulled into the diaphragm to close the pericardiperitoneal canal.
* We now have our diaphragm :)
53
The **septum transversum** makes the central tendon of the diaphragm.
The **body wall** makes the peripheral muscles and the
**dorsal mesentery of the esophagus** makes what?
**_right and left crus of the diaphragm._**
**Pleuroperitoneal memabranes have no adult strucures.**
54
What occurs due to failure of fusion between s**eptum transversum and pleuroperitoneal membranes**... occuring on the _L side_ and causing
* herniation of the guts
* hypoplastic lungs
* polyhydramnios
**Congenital diaphragmatic hernia**
55
**What is a _mesentary_?**
**double layer of serous membrane** or **double layer of splanchnic mesoderm**
## Footnote
**that allows BV and nerves to reach the organs.**
56
What is the difference between
## Footnote
**dorsal and ventral mesentery?**
* **dorsal mesentary**--\> attached to the posterior wall
* **ventral** (which degenerate except for forgut) **mesentary**--\> attached to the anterior wall
57
**visceral peritoneum** (surrounds the organs) is from \_\_\_\_\_\_\_\_\_\_\_
**splanchnic mesoderm**
58
**_parietal peritoneum_** (lines the abdominal cavity) comes from the \_\_\_\_\_\_\_\_\_
**somatic layer.**
59
What does the **_dorsal mesentary_** divide into?
**1. Dorsal mesogastrium**
**2. Ventral mesogastrium**
**-stomach divides the two-**
60
**What is the dorsal mesogastrium?**
* dorsal mesogastrium goes from [**posterior body wall—\> stomach]**
* 3 division:
* **splenorenal L,**
* **gastroslienal L (between spleen and stomach),**
* **greater omentum**
61
**What is the _ventral mesogastrium_?**
* Ventral mesogastrum is located in between the **stomach--\> liver.**
* Forms the **lesser omentum.**
62
**What is the ventral mesentary?**
Ventral mesentary forms our **_falciform L,_**
from liver-\> anterior abdominal wall.
63
**What are the mesentaries in the _midgut and hindgut?_**
**1. _Mesoduodenum-_ mesentary around duodenum**
**2. _Mesentary proper_- mesentary around the jejenum and ileum**
**3. _Mesocolon_- mesentary around the transverse and sigmoid colon**
**4. _Mesorectum_- mesentary around the rectum**
64
How do we form the **greater omentum** (made from the dorsal mesogastrium, from the dorsal mesentary?
* **Dorsal mesogastrium** is a double layer of splanchnic mesoderm.
* As stomach rotates, itpulls dorsal mesentary until we have long dorsal mesentary going to stomach. it will fuse.
* Form the greater omentum (thus, it is the fusion of 2 double layers= 4 layers)
65
**What is the _omental bursa_?**
**nickname?**
AKA **lesser sac**
**- space between stomach and posterior body wall formed by the
rotation of stomach and growth of liver.**
66
What are the intraperitoneal organs? (7) comepletely covered in visceral peritoneum
1. stomach
2. tail pancreas
3. 1st part duodenum
4. Jejunum,
5. ileum
6. transverse colon
7. sigmoid colon
67
Fusion of the mesentaries with body walls results in secondary retroperitoneal structures. What are they?
**1. Mesogastrium dorsal to the spleen**
**2. mesoduodenum**
**3. Ascending mesocolon**
**4. Descening mesocolon**
