Embriología del Sistema Cardiovascular

Question 1

Septum Formation in the Atrium.

Answer 1

The Septum primum, a sickle-shaped crest descending from the roof of the atrium, begins to divide the atrium in two but leaves a lumen, the ostium primum, for communication between the two sides.

Later, when the ostium primum is obliterated by fusion of the septum primum with the endocardial cushions, the ostium secundum is formed by cell death that creates an opening in the septum primum.

Finally, a Septum secundum forms, but an interatrial opening, the oval foramen, persists.

Only at birth, when pressure in the left atrium increases, do the two septa press against each other and close the communication between the two.

Abnormalities in the atrial septum may vary from total absence to a small opening known as probe patency of the oval foramen.

Question 2

Septum Formation in the Atrioventricular Canal.

Answer 2

Four endocardial cushions surround the atrioventricular canal.

Fusion of the opposing superior and inferior cushions divides the orifice into right and left atrioventricular canals.

Cushion tissue then becomes fibrous and forms the mitral (bicuspid) valve on the left and the tricuspid valve on the right.

Persistence of the common atrioventricular canal and abnormal division of the canal are well-known defects.

Question 3

Septum Formation in the Ventricles.

Answer 3

The interventricular septum consists of a thick muscular part and a thin membranous portion formed by

1. an inferior endocardial atrioventricular cushion,
2. the right conus swelling
3. the left conus swelling

In many cases, these three components fail to fuse, resulting in an open interventricular foramen. Although this abnormality may be isolated, it is commonly combined with other compensatory defects.

Question 4

Septum Formation in the Bulbus.

Answer 4

The bulbus (cordis) is divided into

1. the truncus (aorta and pulmonary trunk)
2. the conus (outflow tract of the aorta and pulmonary trunk)
3. the trabeculated portion of the right ventricle.

The truncus region is divided by the spiral aorticopulmonary septum into the two main arteries.

The conus swellings divide the outflow tracts of the aortic and pulmonary channels and with tissue from the inferior endocardial cushion, close the interventricular foramen.

Many vascular abnormalities, such as transposition of the great vessels and pulmonary valvular atresia, result from abnormal division of the conotruncal region; their origin may involve neural crest cells that contribute to septum formation in the conotruncal region.

Question 5

Important derivatives of the original aortic arch system

Answer 5

The aortic arches lie in each of the five pharyngeal arches . Four important derivatives of the original aortic arch system are

• the carotid arteries (third arches)
• the arch of the aorta (left fourth aortic arch)
• the right subclavian artery formed by the right fourth aortic arch, distal portion of the right dorsal aorta, and the seventh intersegmental artery.
• the pulmonary artery (sixth aortic arch), which during fetal life is connected to the aorta through the ductus arteriosus

Question 6

Sistemas venosos embrionarios

Answer 6

Venous System. Three systems can be recognized:

• the vitelline system, which develops into the portal system;
• the cardinal system, which forms the caval system
• the umbilical system, which disappears after birth.

The complicated caval system is characterized by many abnormalities, such as double inferior and superior vena cava and left superior vena cava.

Question 7

Cambios en la circulación luego del nacimiento

Answer 7

In the circulatory system, the following changes take place at birth and in the first postnatal months:

1. the ductus arteriosus closes;
2. the oval foramen closes;
3. the umbilical vein and ductus venosus close and remain as the ligamentum teres hepatis and ligamentum venosum;
4. the umbilical arteries form the medial umbilical ligaments.

Question 8

JIR

Formación del sistema linfático

Answer 8

The lymphatic system develops later than the cardiovascular system, originating from the endothelium of veins as five sacs:

• two jugular,
• two iliac,
• one retroperitoneal,
• and one cisterna chyli.

Numerous channels form to connect the sacs and provide drainage from other structures.

Ultimately, the thoracic duct forms from

1. anastomosis of the right and left thoracic ducts
2. left thoracic duct cranial part.
3. *right thoracic duct distal part *

The right lymphatic duct develops from the cranial part of the right thoracic duct.

Question 9

Cambios en las arterias vitelinas

Answer 9

The vitelline arteries initially supply the yolk sac

later form

• the celiac artery-> foregut
• superior mesenteric artery-> midgut
• inferior mesenteric artery -> hindgut

Question 10

Cambios en las arterias umbilicales

Answer 10

The paired umbilical arteries arise from the common iliac arteries.

After birth,

• the proximal portions persist as the internal iliac and vesicular arteries.
• the distal portions of these arteries are obliterated to form the medial umbilical ligaments