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36 Cards in this Set

  • Front
  • Back
What is the first system to function in the fetus?
Cardiovascular system.

It must function and develop simultaneously.
What trilaminar structure does the heart originate from?
It originates from splanchnopleuric mesoderm.
What are the two endocardial tubes that form during the initial development of the heart?
lateral endocardial tube, and dorsal aorta.

The two lateral endocardial tubes fuse to form a single endocardial tube. Fusion is facilitated by apoptosis.
What day does the heart start to beat?

When is the development of the heart complete?
Day 21.

Heart development is complete by week 7.

Remember, implantation occurs at day 21.
What are the regions of the heart tube starting rostrally?
Dorsal aorta (2)
aortic sac
truncus arteriosus
bulbus arteriosus
primitive ventricle (biggest!)
atrioventricular sulcus
primitive atria
sinus venosus.

Direction to flow if from bottom to top!
In the heart tube, describe what gives rise to the atria, left ventricle, right ventricle, outflow origin/pulmonary artery/aorta.
Right and left atria: primitive atria
Left ventricle: primitive ventricle
Right ventricle: bulbus cordis
Truncus arteriosus: outflow origin/pulmonary artery/aorta.
What are the three circulation systems of the embryo?
Common cardinal
Vitelline
Umbilical
Cardiac jelly
Substrate for cell migration in cardiac septation and valve formation.
What do endocardial cushions do?
They play a role in AV septation.
What happens to the dorsal mesocardium?
It ruptures around day 22, around the same time the heart starts beating.

Dorsal mesocardium temporarily holds the heart tube.
D-Looping
Rightward looping to change the polarity of the heart from ant/post to right/left.
Where does the SA node originate from? AV node?
SA node originates from the sinoatrial ring of the primitive atria of the heart tube.

AV node develops from atriventricular ring in the atrioventricular sulcus of the heart tube.

Problems in looping causes problems in conduction
Vitelline circulation

Where do arteries arise from? Where do they deliver blood to?

What adult arteries and veins
do they give rise to?
Arteries from dorsal aorta bring blood to yolk sac and future gut.

Coeliac, sup. and inf. mesenteric arteries.
Caudal vitelline veins later form portal and hepatic veins.
Umbilical circulation

Where do arteries originate from? Where to they lead?
Arteries arise from dorsal aorta.
Conduct 50% of caridac output to placenta.


Veins bring oxygenated blood to the heart! Vein/artery is reversed!
Cardinal (general) circulation

Where do arteries originate from?
Dorsal branches of intersegmental branches of aorta to neural tube and somite.
Lateral segmental arteries to developing kidneys and gonads.
Heart tube remodeling.

Where does the sinus venosus receive blood from?
Starts around day 24.
Sinus venosus shifts to the right, but remains a paired structure with right and left horns.

Sinus vinosus receives blood from 3 vessels:
Vitelline vein
Umbilical vein
Common cardinal vein.

The sinoatrial orifice shifts to the right.
Crista terminalis
Juntion between the sinus vinosus and the heart tube.

This forms during tube remodeling, and appears on the right venous valve.
What is incorporated in the left atrium during its development?
Primitive pulmonary vein.

Remember, the right atrium incorporates components of the sinus venosus.
Partitioning of the AV canal.

What is the communication between the common atrium and the ventricle?What happens to this opening? Describe the mechanism
Communication between common atrium and ventricle: common AV canal.

The AV canal divides.

Mechanism: endocardial cushions grown on both sides, dividing the AV canal into right and left canals. (day 42)
What do endocardial cushions consist of?

Endocardial cushions separate the AV canal into right and left AV canals.
Cardiac jelly + neural crest cells.
How is the primitive atrium partitioned? Describe the steps involved.
Septum primum appears in day 28.
This forms an opening called foramen primum.
Perforations start appearing in the septum primum (apoptosis) to form the foramen secundum. (allows blood to flow from R. to L. atrium and avoid loading the pulmonary circulation.
A new septum, septum secundum, appears to the right or septum primum and overlaps foramen secundum.

Septum secondum DOES NOT fuse with endocardial cushions. The free edge forms FORAMEN OVALE
The persistent part of septum primum now acts as a valve, called valve of foramen ovale (allows ONLY R. to L shunting).
Partitioning of primitive ventricle.

Describe the steps.
Muscular interventricular septum grow in opposition to one another.
The interventricular septum do not reach the fused AV cushions, leaving an interventricular foramen.
A membranous interventricular septum appears.
AV cushion tissue fuses with the muscular interventricular septum and aortico-pulmonary septum.
Partitioning of bulbus cordis and truncus arteriosus. Describe the steps.
Aortico-pulmonary septum (from neural crest) appear in ridges of bulbus and truncus.
Bulbus and truncus is divided spirally, forming the ascending aorta and pulmonary trunk. This participates in the membranous interventricular septum.
Where is the aortico-pulmonary septum derived from?
Neural crest mesenchyme
Which cardinal veins form anastomoses?
What forms the azygous vein?
What forms coronary sinus?
What forms inferior vena cava?
L. and R. cardinal veins form anastomoses.

Right posterior cardinal vein becomes azygous vein.

Left sinus horn becomes coronary sinus.

Right vitelline vein becomes inferior vena cava.

All of this is completed in 8th week of gestation!
Which aortic arches disappear?
1, 2, and 5.

Remember $1.25
What forms maxillary arteries?
Remnants of aortic arch 1.
What forms stapedial arteries?
Remnants of aortic arch 2.
What forms common carotid arteries and proximal portion of internal carotid artery?
3rd aortic arch.
What forms the aortic arch?

EXAM
4th aortic arch

Right side forms the proximal portion of right subclavian artery.
What forms the right and left pulmonary arteries? Ductis arteriosus?
The 6th aortic arch.
Proximal portion: right and left pulmonary aa.
Distal portion: ductus arteriosus.
What chemical is required to keep the ductus arteriosus and ductus venosus patent?
Prostaglandins.
Ductus arteriosus
In the developing fetus, the ductus arteriosus is a blood vessel connecting the pulmonary artery to the aortic arch.

It allows most of the blood from the right ventricle to bypass the fetus's lungs.

Upon closure at birth, it becomes the ligamentum arteriosum.
Ductus venosus
In the fetus, the ductus venosus shunts approximately half of the blood flow of the umbilical vein directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.
When does the pulmonary vascular bed open up?

What changes happen to the ductus arteriosus?
At first inspiratory effort at birth.

BP in the ductus arteriosus drops markedly, and it constricts within minutes after birth.

BP in the left atrium increases markedly due to blood from the lungs.

BP in the right atrium decreases markedly once the ambilical cord is cut.

End result: BP in L. atrium >> BP in R. atrium.

This pressure differences auses septum secundum and foramen secondum, and they close over several months.
Ligumentum teres hepatis (round ligament of the liver) is a remnant of what fetal blood vessel?
Umbilical vein.