Embryology of the Heart and Great Vessels Flashcards
Describe the fate of the dorsal mesocardium.
Dorsal mesocardium degenerates to form transverse sinus, separates inflow and outflow vessels.
Describe the fate of the epicardium.
Becomes visceral pericardium
Describe the fate of the splanchnic mesoderm surrounding the heart tube.
myocardium
Describe the fate of the endocardial heart tube.
endocardial lining
Name the 5 regions of the 2-chambered heart.
(sinus venosus)
- atrium
- ventricle
- bulbus cordis
- truncus arteriosus
- aortic sac
Name the opening that lies between the inflow tract and the atrium.
sinus venosus
Describe how the fused endocardial cushion forms at the atrioventricular canal.
The endocardial cushions form on the dorsal and ventral walls of the AV canal. They approach each other and fuse, dividing the AV canal into right and left AV canals. These canals partially separate the primordial atrium from the ventricle, and the cushions function as AV valves. The endocardial cushions develop from a specialized extracellular matrix related to the myocardium.
BWAB8 p196
Describe how the septation of the atrium occurs.
- -septum primum
- -septum secundum
- -foramen primum
- -foramen secundum
- -foramen ovale
- The SEPTUM PRIMUM grows toward the fusing endocardial cushions from the roof of the primordial atrium.
- As this septum develops, a large opening forms between its edge and the endocardial cushions - the FORAMEN PRIMUM - which allows oxygenated blood to go from right to left atrium.
- Foramen shrinks and disappears but before it is totally gone, the FORAMEN SECUNDUM appears in septum primum.
- The SEPTUM SECUNDUM grows from the ventrocranial wall of the atrium immediately to the right of the septum primum.
- The septum secundum doesn’t grow all the way down, and the opening left there is the FORAMEN OVALE.
- The valve of the foramen ovale is formed by the remaining part of the septum primum attached to the endocardial cushions.
Describe how the embryonic interatrial septum allows for one-way blood flow from the right to left atria.
Pressure is higher in right atrium than left atrium. Oxygenated blood flows from right atrium to left atrium through the one way valve formed by the foramen ovale/septum primum and the foramen secundum.
Describe the embryonic origin of the crista terminalis.
Where is it and what is its significance in the adult heart?
The Crista Terminalis represents the junction between the sinus venosus and the heart in the developing embryo.
- It is the line between the right atrium and right auricle (smooth part and rough part).
- It is the point of attachment for pectinate muscles.
- The SA node is located in the right atrium at the junction of the crista terminalis with venous tissue (the superior and inferior vena cava, and the intercaval region between the two great veins)
Describe how the sinus venosus contributes to the wall of the right atrium.
The smooth-walled portion of the right atrium (sinus venarum) is derived from sinus venosus.
Describe how the single pulmonary vein contributes to the wall of the left atrium.
The smooth-walled portion of the left atrium is derived from pulmonary vein.
Describe how the bulbar and truncal ridges give rise to a spiral septum that divides the outflow tract into separate aorta and pulmonary trunk.
The aorticopulmonary septum is derived
largely from neural crest cells and forms as a spiral down the truncus arteriosus and bulbus cordis. As a result, the aorta and pulmonary trunk twist around each other.
Describe how septation of the ventricle occurs.
–the 3 embryological sources of cells that make up the adult interventricular septum
Muscular part of the IV septum Membranous part of the IV septum Closure of the IV foramen due to fusion of tissue from 3 sources: 1. right bulbar ridge 2. left bulbar ridge 3. endocardial cushion
Describe how the semilunar valves develop.
Cardiac jelly and mesenchymal cells bulge, remodel, and elongate.
Name the 5 embryonic structures of the cardiovascular system that undergo a transformation after birth, and the adult structures that result.
- umbilical arteries close -> medial umbilical ligaments
- umbilical vein closes -> ligamentum teres
- ductus venosus closes -> ligamentum venosum
- foramen ovale closes -> fossa ovalis
- ductus arteriosus closes -> ligamentum arteriosum
What are the 4 basic stages of heart development?
- Specification of cardiac precursor cells
- Migration of cardiac precursor cells and fusion of the primordia
- Heart looping
- Remodeling
What are the 5 stages of heart remodeling?
- Modification of venous system
- Septation (atria. ventricles. outflow tracts)
- Valve formation
- Transformation of primitive arterial system
- Transition from fetal to adult circulation
What happens to the foramen ovale after birth?
After birth, the foramen ovale functionally closes due to higher pressure in the left atrium, and the valve of the foramen ovale fuses with the septum secundum, forming the fossa ovalis. Thus the interatrial septum becomes a complete interatrial partition.
What is the ductus venosus? What is its fate?
Ductus venosus connects the left umbilical vein and the IVC, allowing some oxygenated blood from the placenta to bypass the liver.
It becomes the ligamentum venosum.
Describe how the cusp valves develop.
The mitral and tricuspid valves, the chordae tendinae, and the papillary muscles all form by CAVITATION.
What vessels form the superior vena cava?
The right anterior cardinal and right common cardinal veins
What vessels form the inferior vena cava?
The right vitelline vein forms part of the IVC; secondary veins form the remainder
What are the portions of the left and right ventricles formed from the bulbus cordis?
Conus arteriosus (infundibulum): portion of right ventricle derived from bulbus cordis
Aortic vestibule: portion of left ventricle derived from bulbus cordis
