Embryology Flashcards
Splanchnic Mesoderm
The tissue layer just anterior to the endoderm
Cardiogenic field
Appearing in the 3rd week, this field is formed as a horseshoe around the cranial neural folds.Offically called the cardiogenic region ones blood islands have formed a cohesive tube.
What is the crista terminalis?
What are blood islands
Blood islands form around the 4th week in the Primary Heart Field. They unite into a horseshoe shaped endothelial-lined tube surrounded by myoblasts to form the cardiogenic region.
other islands on the palallel axis will for the dorsal aorta
What is the dorsal mesocardium
A fold of mesodermal tissue that attaches the developing heart tube to the dorsal side of of the pericardial cavity. I looks like the I of an I beam at this point.
becomes the transverse sinus
What is the transverse pericardial sinus
The later stage of development of the Dorsal Mesocardium, connecting the myocardium to the pericardial cavity.
What is the epicardium?
The outer layer or developing heart tissue that is derived from the proepicardium moving down from the caudal end.
**Is responsible for formation of the coronary arteries, including their smooth muscle. **
What is the cardiac loop
the loop created as the developing heart tube grows and folds over itself.
Bending begins on day 23, complete by day 28
What is the bulbus cordis
Part of the developing heart in the cardiac loop, it lies between the developing ventricle and aortic roots.
It has several differnt parts, some of which become part of the right ventricle, the conus cordis which forms the outflow tracts of both ventricles, and the truncus arteriosus which forms the roots and proximal portions of the aorta and pumonary artery.
what is the conus cordis,
mentioned with the bulbus cordis, this portion of the developing heart tube will beome the outflow tracts of both ventricles.
What is the primitive ventricle
The developing portion of the ventricle and the bulbus cordis that will eventually form the ventricles.
What is NKX-2.5
A transcrition factor that is induced by the endoderm to cause the splanchnic mesoderm to form the heart.
what are BMP 2 and 4
They are secretions from the endoderm, that carry the signal to induce NXK2.5
What are WNT proteins, and what does their inhibition do?
WNT proteins inhibit heart development. Inhibitors to the proteins within the heart forming mesoderm alllow BMP to function and activate NKX2.5 to start heart development.
What is the Sinus Venosus
The term for the area that receives blood from the right and left sinus horns, which in turn recieve blood from the vitelline veints and the umbilical vein. Communicates directly with the developing atrium, but then is shifted two the right and lost.
What are the vitelline, cardinal and umbilical veins?
Veins that feed into the left and right sinus horns. around the fifth week the left portions of these veins are lost and the left sinus horn becomes the oblique left atrial vein and the coronary sinus.
What are the Sinus Horns
THe sinus horns collect blood from the Cardinal, umbilical, and vitelline veins and deliever it to the sinus venosus.
The left side degrades in the 5th week, eventually becoming the oblique vein of the left atrium and the coronary sinus.
The right horn enlarges, shifts further right and becomes the smooth wall of the right atrium.
The dividing line for this merger is known as the Crista Terminalis.
What is the Crista Terminalis
The dividing line between the trabeculated part of the right atrium, and the encorporated smooth wall formed by the absorption of the right sinus horn.
What are Endocardial Cushions
Active growth of a single tissue mass that continues to expand until it reaches the opposite side of the lumen. The primary concern for us is the cousion that seperates the atrium and ventricle.
These are major sites for defects to develop like VSD and ASD
What is the ostium primum
The roof of the common atrium decends towards the endocardial coushion. The septum that remains (albiet temporarily) is the ostium primum. It will eventually be closed by other advancing tissues.
