Cardiac Embryology (Dustin) Flashcards
When do the primordial heart and vascular system appear?
The middle to end of the 3rd week (18-19 days)
At this point, the rapidly growing embryo can no longer satisfy its
nutritional and oxygen requirements by diffusion alone
From which part of the embryo does the cardiovascular system derive?
The Cardiogenic Area, a part of the intraembryonic mesoderm anterior to the oropharyngeal membrane and posterior to the septum transversum
What stimulates early formation of the heart?
**Inductive Signals **from the anterior endoderm
What is the earliest sign of the heart forming?
What happens with this structure?
The appearance of the angioblastic cords (paired endothelial strands) in the cardiogenic mesoderm (leaves from the splanchnic mesoderm, moves medially) during 3rd week
These cords form canals and become two thin heart tubes. As lateral embryonic folding occurs, the endocardial heart tubes approach each other and fuse to form a single heart tube
When does the heart begin to beat?
When does blood begin to flow?
The heart begins to beat at 22 to 23 days.
Blood flow begins during the fourth week and can be visualized
by Doppler ultrasonography
What 3 veins drain into the tubular heart (~4 weeks)?
- Vitelline veins return poorly oxygenated blood from the umbilical vesicle (yolk sac).
- Umbilical veins carry well-oxygenated blood from the chorionic sac.
- Common cardinal veins return poorly oxygenated blood from the body of the embryo.
What happens with the umbilical veins as the embryo/fetus develops?
The umbilical veins run on each side of the liver and
carry well-oxygenated blood from the placenta to the
sinus venosus. As the liver develops, the umbilical veins
lose their connection with the heart and empty into the
liver. The right umbilical vein disappears during the
seventh week, leaving the left umbilical vein as the only
vessel carrying well-oxygenated blood from the placenta
to the embryo.
What special structure develops to help oxygenated blood bypass the liver?
A large venous shunt—the ductus venosus (DV)—
develops within the liver and connects the
umbilical vein with the inferior vena cava. The
DV forms a bypass through the liver, enabling most of
the blood from the placenta to pass directly to the
heart without passing through the capillary networks
of the liver.
What two ways do embryotic folding further the development of the heart?
What are their axes?
“flexion” around transverse axis – this will explain how the heart primordium moves from “above the head” into the chest occupying its final position.
“rolling” around the longitudinal axis – this will mainly explain the fusion of the structures originally developing on the two sides of the embryo.
(Remember: embryotic folding occurs during 4th week)
What part of the heart develops from the splanchnic mesoderm?
What forms from the thickening of the splanchnic mesoderm?
The Splanchnic Mesoderm forms the endocardial tubes, that become the endocardium
Thickening of the splanchnic mesoderm gives the myoepicardial mantles from which the myocardium, and the visceral layer of the pericardium (epicardium) develop
What part of the embryo develops into the pericardial cavity?
the **intraembryonic colem, **originally bound by the lateral plates
What part of the heart develops from the somatic layer of mesoderm?
the parietal layer of of pericardium
