Abdominal Embryology Flashcards
Gastrulation occurs at week ___ to create three embryonic germ layers: ___, ___, and ___.
week 3; ectoderm, mesoderm, endoderm
Cells that displace the hypoblast form the ___
endoderm
Cells that remain in the epiblast form the ___
ectoderm
Cells that lie between the endoderm and ectoderm form the ___
mesoderm
All three germ layers are derived from the ___
epiblast
What two places in the developing embryo are not a 3-layer disk, and what do they go on to form? What layer is missing?
Bucopharyngeal membrane –> forms oral cavity
Cloacal membrane –> forms anus
Missing the mesoderm
In the middle of week ___, the mesoderm differentiates into three parts: ___, ___, ___.
Week 3; paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm
The paraxial mesoderm forms ___ and ___.
Somitomers (striated muscles of face and throat) and somites (dermis, skeletal muscles, vertebrae)
The intermediate mesoderm forms the ___
urogenital system
The lateral plate mesoderm forms the ___ from fused ___, which is a ___-shaped cavity.
intraembryonic coelom from coelomic spaces; horseshoe-shaped
The curve of the intraembryonic coelom horseshoe become the ___, and the lateral extensions become the ___ and ___.
curve - pericardial cavity
lateral extensions - pleural and peritoneal cavities
What are the two layers of the lateral plate mesoderm?
Somatic (somatopleure) - parietal
Splanchnic (splanchnopleure) - visceral
What four folds does the flat trilaminar disc make to become 3D?
Head/cephalic, tail/caudal, and two lateral folds
During embryonic folding, the ___ and ___ grow, but the ___ doesn’t.
Amnion and embryonic disc grow; yolk sac doesn’t
During ___ folding, part of the yolk sac is converted into ___, forming the ___, ___, and ___.
lateral folding; gut tube; foregut, midgut, hindgut
___ causes the cranial folding
Growth of the forebrain beyond the buccopharyngeal membrane
Result of cranial folding
Pushes heart, pericardial coelom, septum transversum, and buccopharyngeal membrane in place
___ causes caudal folding
growth of spinal cord
Result of caudal folding
cloacal membrane is positioned correctly and part of yolk sac is incorporated as hindgut
Somatic mesoderm lines the embryonic ___ and becomes ___, ___, and ___
body cavity; parietal pleurae, pericardium, peritoneum
Splanchnic mesoderm covers ___ and becomes ___, ___, ___, and ___
endodermal gut tube; visceral layer of pleurae, pericardium, peritoneum, and smooth muscle of gut tube
What are the three divisions of the intraembryonic cavity, and what do they contain?
Pericardial cavity - heart
Pericardioperitoneal canals - lungs
Peritoneal cavity - gut
The septum transversum initially starts at ___
C1
By week 8, the anterior part of the septum transversum is at ___ and the posterior part is at ___
T7, T12
At weeks ___, myoblasts muscularize the septum transversum, bringing along the ___ nerve
weeks 5-6; phrenic nerve
What is a congenital diaphragmatic hernia?
Malformation of the diaphragm, usually failure of the pleuroperitoneal membranes to fuse with other diaphragmatic components, allowing abdominal contents to herniate into the thorax
Result of congenital diaphragmatic hernia
abdominal contents herniate into pleural cavities, which interferes with lung development
What are the four precursors to the diaphragm, and which part(s) do they form?
- Septum transversum - central tendon and majority of anterior diaphragm
- Esophageal mesenchyme - right and left crura (and esophageal hiatus)
- Muscular ingrowth from lateral body wall - posteriolateral part
- Pleuroperitoneal membranes - posterior diaphragm
___ is the downward indentation between the diaphragm and chest wall. That space is called the ___
Costophrenic angle; costodiaphragmatic recess
The costophrenic angle is important in detecting ___ on x-rays
small pleural effusions
Two types of congenital diaphragmatic hernias
Bochdalek and Morgagni
Bochdalek CDH
posteriolateral diaphragmatic defect, usually on the left side; majority of cases
Morgagni CDH
anterior, retrosternal, or parasternal diaphragmatic defect; rare
What is eventration, what causes it, and how does it appear on an X-ray?
It is when the abdominal cavity contents push up on (but not through) a thin part of the diaphragm; it is due to incomplete muscularization of the diaphragm; On an x-ray, the diaphragm dome/margin is still visible, but is elevated; all intestinal air bubbles are below the diaphragm
What separates the pleural and pericardial cavities?
Pleuropericardial folds
What are the three layers of the pleuropericardial folds and what do they become?
body wall mesenchyme sandwiched between two layers of somatopleuric mesoderm; one layer of the somatopleuric mesoderm joins the visceral pleura around the lung; the other layer becomes the parietal layer of the serous pericardium
Where is the phrenic nerve embedded?
The serous layer of pericardium (in between the fibrous pericardium and mediastinal pleura)
Epithelial lining of GI tract is from ___
endoderm
Smooth muscle of GI tract is from ___
splanchnic (visceral) mesoderm
The yolk sac and midgut are connected via the ___
vitelline duct
Endodermal derivatives other than GI tract epithelial lining
Parathyroid glands, thymus, thyroid glands, lungs, liver, pancreas, gallbladder
