Cardio Embryology (Khan ?'s only) Flashcards
These are Khan's questions.
Where is the first evidence of heart formation?
Splanchnic layer of lateral plate mesoderm (just said splanchnic layer in class)
What type of cells are within splanchnic mesoderm?
Cardiac Myoblasts
What are Cardiac Myoblasts derived from?
Cardiac Progenitor cells induced by underlying pharyngeal endoderm
What do blood islands in the Splanchnic layer form?
Endothelial lined tubes and transitory blood vessels, definitive blood cells come from mesoderm around aorta later from liver even later from bone marrow
Where does the future heart begin?
Cranial part of embryo, Buccopharyngeal membrane is landmark for this, it its just cranial to the buccopharyngeal membrane
What is the cardiogenic field?
Endothelial lined tubes and myoblasts formed by the previous blood islands, just cranial to the buccopharyngeal membrane
What is above the cardiogenic field?
Pericardial cavity which is derived from the embryonic cavity
What brings the heart into its natural anatomical position?
Cranial and caudal folding of the embryo brings the heart into the thoracic region
What forms the two endothelial lined tubes on both sides of the heart?
Blood islands produce angiogenic cells that dissolve into endothelial lined tubes, they eventually become endocardial regions of the heart
What happens to endothelial tubes?
Fold into the midline and fuse to form a single endocardial tube
What surrounds endocardial tube (cell type)?
Myoblasts that will become the myocardium of the heart
What surrounds endocardial tube and eventually disappears, & serves no function?
Cardiac Jelly
List the invaginations of the endocardial tube.
What will each of these invaginations ultimately form?
Truncus arteriosus -> aorta and pulmonary trunk, Bulbus cordis ->inf. Part of aorta and pulmonary trunk & adjacent parts of two ventricles, Primordial ventricles -> ventricles, primordial atria -> atria, sinus venosus-> Right horn becomes right atrium, left becomes coronary sinus
How does blood enter the primitive heart ? (Before Atria/Ventricle portioning)
Sinus venosus
How are the atria and ventricles partitioned?
Endocardial cushions grow towards each other, partitions atria from vessels and ventricles (produces a pattern with two holes penetrating septum that divides atria from ventricles)
Describe the formation of the AV valves
Dense mesenchyme and myoblasts present, cavitation occurs and cells die, some are replaced by connective tissue which becomes chordate tendinae
What direction is blood originally shunted in atria?
From right to left (mix of oxygenated and deoxygenated blood)
What is the crescent shape fold that grows down from the roof of the atria (initially in atrial Septation)? What related structure is formed?
Septum primum
Osteum primum
What happens after Osteum primum is formed at the top of the crescent shape fold?
Osteum secundum (maintains shunting after closure of osteum primum)
What is the second structure that grows downward from the roof of the atria?
Septum secundum
What develops in this structure?
Foramen ovale
What causes blood to be shunted from RA to LA, after heart is divided into R/L V/A?
Pressure in RA is higher than L, pushes blood through foramen ovale to LA
How is blood shunted after birth, and why?
Pressure changes , LA is higher and maintains valve closure if it already has not fused
What is the function of the ductus arteriosus?
Short circuits lungs, sends oxygengated blood from RA directly into aorta
What is the muscular part of the two ventricles derived from?
Develops from a ridge between the two ventricles
What forms the membranous part of the two ventricles?
Cotruncal (spiral ) septum descending to meet the endocardial cushion in the muscular ridge
What is probe patency of foramen ovale?
Foramen ovale did not fuse, no effect because it is a one way valve, present in 25% of pop.
Describe the condition of excessive resorption of septum primum.
Causes L to R shunt
Describe the condition of absence of septum secundum.
L to R shunt
What is a common atrium?
No attempt at partitioning of atria at all, causes L to R severe shunting
Describe defects in ventricular septum.
Occur in membranous part of septum:
- systemic blood goes back into pulmonary circuit, too much blood pushing through pulmonary trunk
- increased resistance
- hypertrophy of RV
- shunts blood from R to L
- cyanosis called Eisenmenger complex
Defects in Septation of truncus arteriosus , describe Tetralogy of Fallot.
Aortic arch and pulmonary trunk are shifted to R
pulmonary trunk is smaller and aorta is much larger
*eisenmenger complex + cyanosis
Describe persistent truncus arteriosus
No Septation of aorta and pulmonary trunk, only one vessel leaving heart
causes cyanosis
*always accompanied by membranous ventricular defect (otherwise would be a closed system)
Describe transposition of the great vessels.
Open into wrong chambers; causes R to L shunt and cyanosis occurs when AP septum fails to spiral
Describe patent ductus arteriosus.
Blood goes into pulmonary trunk and gets into aorta from ductus arteriosus, can lead to eisenmenger syndrome leads to cyanosis more quickly than atrial defects
Before birth the ductus arteriosus provides communication between what two structures?
Pulmonary Trunk and Aorta
The initial two endothelial tubes that fuse to form the heart develop in what layer?
Splanchnic mesoderm
Before birth, what structure overlaps the ostium secundum and appears to close it?
Septum secundum
What causes tetralogy of fallot?
A misaligned AP septum
Which of the aortic arches gives rise to the pulmonary arteries?
6th aortic arch
Just before birth, all blood from the placenta goes through the liver. Describe its course.
Passes directly through via the ductus venosus
How many aortas does a developing embryo have ?
Two pairs of dorsal aortas
How does blood exit the heart?
Through an aortic sac ( has L and R divisions, forms 6 arches)
Describe the aortic arches
Anteriorly they communicate with a horn like structure and loop out from dorsal aorta to this structure
What does arch 3 give rise to? 4? 6?
3 -> common carotid and internal carotid a.
4-> R. subclavian, and arch of aorta from l. common carotid to l. subclavian,
6-> L and R pulmonary arteries and ductus arteriosus
Why is the r. recurrent laryngeal n superior to the L?
A portion of aortic arch 6 disappears on the R side, on the L side the ductus arteriosus remains
What is preductal coartication of aorta?
Narrowing of aorta prior to the ductus arteriosus, => ductus arteriosus remains patent, if post ductal ductus arteriosus atrophies
What forms the common cardial vein?
Anterior and post. Cardinal veins, the common cardinal vein also receives umbilical veinand two vitelline veins, sinus venosus receives common cardinal v.
What do the vitelline veins form?
Hepatic sinusoids, hepatic portal v. , hepatic veins, hepatic IVC
What happens to the R. umbilical vein?
Atrophies
What does the L. umbilical vein extend through the liver as?
Ductus venosus
What does the sinus venosus become?
Hepatic portion of IVC (later he says that the vitelline veins actually forms this, somewhat misleading from his lecture)
What do the sup. + inf. parts of vitelline veins form?
Hepatic and renal veins, respectively
Describe pre-natal circulation.
Path 1: Umbilical v-> ductus venosus -> IVC -> foramen ovale -> LA,LV -> aorta -> systemic -> umbilical a.
Path 2:
SVC -> RA -> RV -> Aorta (mixes oxygenated from path 1 with deoxygenated ) -> systemic -> umbilical a.
What does the umbilical arteries and veins atrophy to?
Umbilical v. -> ligamentum teres hepatis Umblicial artery -> medial umbilical ligaments
