Sinus Venosus, Atria, IAS, Pulmonary Veins, Valves, Arches

Question 1

The sinus venosus receives 3 pairs of veins. The are____, ____, and _____.

Answer 1

The vitelline veins, the umbilical veins, and the cardinal veins.

Question 2

What happens to the left sinus horn and the transverse portion of the sinus venosus?

Answer 2

They become more separated from the left side of the atrium by a deep fold.

Question 3

As the heart grows, what happens to the right sinus horn?

Answer 3

It becomes more vertical and incorporated into the floor of the RA.

Question 4

How are folds produced within the atrial cardiac wall?

Answer 4

By the incorporation of the sinus venosus and the right and left sinus horns.

Question 5

What arises at the sinoatrial junction?

Answer 5

A right sinus (venous) valve forms on the right, and a left sinus (venous) valve forms on the left.

Question 6

Superiorly, what do the R/L sinus (venous) valves join to form?

Answer 6

The septum spurium

Question 7

What does the left sinus (venous) valve fuse with?

Answer 7

The atrial septum

Question 8

What does the inferior portion of the right sinus (venous) valve form?

Answer 8

The valve of Eustachii, the Ostia of the coronary sinus, and the valve of Thebesii.

Question 9

What produces a depression on the roof of the common atria?

Answer 9

The truncus arteriosus

Question 10

How is the septum primum formed?

Answer 10

It is formed passively by the deepening of the depression created by the truncus arteriosis on the roof of the common atria.

Question 11

What is the ostium primum?

Answer 11

It is the foramen between the right and left primitive atria.

Question 12

As a result of the tissue of the septum primum growing and fusing with the endocardial cushions, the _______.

Answer 12

Ostium primum becomes smaller, and finally closes.

Question 13

Before the ostium primum closes, what appears?

Answer 13

Perforations appear in the septum primum, posterosuperiorly.

Question 14

What do the tiny perforations in the septum primum form?

Answer 14

They coalesce to form the ostium secundum to keep communication between the RA and LA.

Question 15

What is the name of the second tissue layer which grows between the atria?

Answer 15

Septum secundum

Question 16

How is the septum secundum formed?

Answer 16

It is formed by the continuous folding of the interseptovalvular space and it is thicker and more muscular than the septum primum.

Question 17

At this point there are 2 septums. What are they? And how are they growing?

Answer 17

The septum primum is growing towards the endocardial cushions.
The septum secundum is growing inferiorly and posteriorly.

Question 18

What is the foramen ovale?

Answer 18

It is an opening in the interatrial septum allowing communication between the RA and LA.

Question 19

What vessel arises from the wall of the LA, and what does it connect with?

Answer 19

A single pulmonary vein that connects to the splanchic plexus of vasculature behind the LA at the level of the lung buds.

Question 20

How are the remaining 3 pulmonary veins formed?

Answer 20

By magic!

Question 21

What lines the AV canal and the R/L atrioventricular orifices?

Answer 21

Mesenchymal tissue

Question 22

Each AV orifice contains small ________.

Answer 22

Protuberances from the lateral endocardial cushions.

Question 23

What valves do these endocardial cushions give rise to?

Answer 23

The ALMV and the major portion of the ALTV only.

Question 24

Where does the major component of leaflet formation come from?

Answer 24

The ventricular wall

Question 25

What covers the atrial surface of the valve area?

Answer 25

Endocardial tissue

Question 26

Where is the skirt of ventricular muscle located?

Answer 26

Within the right ventricle.

Question 27

From where and how do the TV leaflets arise?

Answer 27

They are undermined (delaminated) away from the ventricular myocardium and attached to the chordae.

Question 28

How is the left ventricular skirt divided?

Answer 28

Into 2 sections: 2 anterior (derived from the left halves of the endocardial cushions) And 2 posterior.

Question 29

How do we end up with an anterior and posterior leaflet in the Mitral valve?

Answer 29

2 of the valve skirts fuse to form each leaflet.

Question 30

How are the AO and PA valves formed?

Answer 30

From truncal swellings and a third cushion which is called the intercalated valve swelling.

Question 31

What is formed from the intercalated valve swellings?

Answer 31

The cusps of the AO and PA as well as the sinuses.

Question 32

What vessels arise from the first arch?

Answer 32

The Maxillary arteries

Question 33

What vessels arise from the second arch?

Answer 33

The Stapedial arteries

Question 34

What vessels arise from the third arch?

Answer 34

Common, internal and external carotid arteries

Question 35

What vessels arise from the fourth arch?

Answer 35

On the left: Part of Aortic arch

On the right: Part of R. Subclavian artery

Question 36

What vessels arise from the fifth arch?

Answer 36

No known deviations. Transient, not well developed

Question 37

What vessels arise from the sixth arch?

Answer 37

On the left: Ductus arteriosus and L. Pulmonary artery

On the right: R. Pulmonary artery

Question 38

What vessels arise from the seventh arch?

Answer 38

On the left: L. Subclavian

On the right: Part of R. Subclavian

Question 39

What vessels arise from the dorsal aortas?

Answer 39

L Dorsal Aorta: DTAo;

R Dorsal Aorta: part of R. Subclavian. Remainder disappears.