Flashcards
Cardiovascular System- Embryology
Cards in this deck (24)
- 1Formation of Heart TubeLateral plate mesoderm (at the cephalic area of the embryo) will split into a somatic layer and a splanchnic layer, thus forming the pericardial cavity. Precardiac mesoderm is preferentially distributed to the splanchnic layer and is now called the heart-forming regions. As lateral forming of the embryo occurs, the HFRs will fuse in the midline to form a continuous sheet of mesoderm. Hypertrophied foregut endoderm secretes vascular endothelial growth factor (VEGF), which induces the sheet of mesoderm to form discontinous vascular channels that eventually get remodeled into a single endocardial tube (endocardium). Mesoderm around the endocardium forms the myocardium, which secretes a layer of extracellular matrix proteins called cardiac jelly. Mesoderm migrating into the cardiac region from the coelomic wall near the liver forms the epicardium.
- 2Primitive Heart Tube Dilatations.Five dilatations soon become apparent along the length of the tube, the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium and sinus venosus. These five dilatations develop into the adult structures of the heart.
- 3Truncus arteriosusAorta
Pulmonary trunk - 4Bulbus cordisSmooth part of the right ventricle (conus arteriosus)
smooth part of the left ventricle (aortic vestibule) - 5Primitive ventricleTrabeculated part of the right ventricle.
Trabeculated part of the left ventricle. - 6Primitive atriumTrabeculated part of right atrium
Trabeculated part of left atrium - 7Sinus venosusSmooth part of the right atrium (sinus venarum)
Coronary sinus
Oblique vein of the left atrium - 8The Aorticopulmonary SeptumFormation- Neural crest cells migrate from the hindbrain region through pharyngeal arches 3, 4, 6 and invade both the truncal ridges and the bulbar ridges. The truncal and bulbar ridges grow and twist around each other in a spiral fashion and eventually fuse to form the AP septum. The AP septum divides the truncus arteriosus and bulbus cordis into the aorta and pulmonary trunk.
- 9Persistent truncus arteriosusIs caused by abnormal neural crest cell migration such that there is only a partial development of the AP septum. PTA results in a condition in which one large vessel leaves the heart and receives blood from both the right and left ventricls. PTA is usually accompanied by membranous ventricular septal defect (VSD) and is associated with clinically marked cyanosis, R-L shunting of blood.
- 10Transposition of the great arteriesIs caused by abnormal neural crest cell migration such that there is nonspiral development of the AP septum. D-transposition results in a condition in which the aorta arises abnormally from the right ventricle and the pulmonary trunk arises abnormally from the left ventricle, hence the systemic and pulmonary circulations are completely seperated from each other. It is incompatible with life unless an accompanying shunt exists like a VSD, patent foramen ovale or patent ductus arteriosus. It is associated clinically with marked cyanosis. (R-L shunting of blood)
- 11L-transposition of the great vesselsIn L-transposition, the aorta and pulmonary trunk are transposed and the ventricles are inverted such the anatomicaly right ventricle lies on the left side and the anatomicaly left ventricle lies on the right side. These two major deviations offset one another and such that blood flow pattern is normal.
- 12Tetralogy of FallotIs caused by an abnormal neural crest cell migration such that there is skewed development of the AP septum. TF results in a condition in which the pulmonary trunk obtains a small diameter while the aorta obtains a large diameter. TF is characterized by four classic malformations, pulmonary stenosis, right ventricular hypertrophy, overriding aorta, and ventricular septal defect. TF is associated clinically with marked cyanosis (R-L shunting of blood) in which the clinical consequences depend primarily on the severity of the pulmonary stenosis.
- 13The Atrial Septum FormationThe crescent-shaped septum primum forms in the roof of the primitive atrium and grows toward the atrioventricular cushions in the AV canal. The foramen primum forms between the free edge of the septum primum and the AV cushions, it is closed when the septum primum fuses wih the AV cushions. The foramen secundum forms in the center of the septum primum. The crescent-shaped septum secundum forms to the right of the septum primum. The foramen ovale is the opening between the upper and the lower limbs of the septum secundum. During embryonic life, blood is shunte from the right atrium to the left atrium via the foramen ovale. Immediately after birth, functional closure of the foramen ovale is facilitated both by a decrease in right atrial pressure from occlusion of placental circulation and by an increase in left atrial pressure due to increased pulmonary venous return. Later in life, the septum primum and septum secundum anatomically fuse to complete the formation of the atrial septum.
- 14Clinical ConsiderationsAtrial septal defects are noted on auscultation with a loud S1 and a wide, fixed split S2 and are characterized by L-R shunting of blood.
- 15Foramen secundum defectcaused by excessive resorption of septum primum, septum secundum or both. This results in a condition in which there is an opening between the right and left atria. Some defects can be tolerated for a long time, with clinical symtpoms manifesting as late as age 30 years. it is the most common clinically significant ASD.
- 16Common atrium (cor triloculare biventriculare) is caused by the complete failure of septum primum and septum secundum to develop. This results in a condition in which there is formation of only one atrium.Probe patency of the foramen ovale is caused by incomplete anatomic fusion of septum primum and septum secundum. It is present in approximately 25% of the population and is usually of no clinical importance.
- 17Primature closure of foramen ovaleIs closure of foramen ovale during prenatal life. It results in hypertrophy of the right side of the heart and underdevelopment of the left side of the heart.
- 18The Atrioventricular SeptumThe dorsal AV cushion and ventral AV cushion approach each other and fuse to form the AV septum. The AV septum partitions the AV canal into the right AV and the left AV canal.
- 19Clinical considerations 1. persistent common AV canalIs caused by failure of fusion of the dorsal and ventral AV cushions. It results in a condition in which the common AV canal is never partitioned into the right and left AV canals, so that a large hole can be found in the center of the heart. Consequently, the tricuspid and bicuspid valves are represented by one valve common to both sides of the heart.
- 20Two common hemodynamic abnormalities are foundL-R shunting of blood from the left atrium to the right atrium, causing an enlarge right atrium and right ventricle.
Mitral valve regurgitation, causing an enlarged left atrium and left ventricle. - 21Ebstein's anomalycaused by the failure of the posterior and septal leaflets on the tricuspid valve to attach normally to the annulus fibrosus, instead they are displaced inferiorly into the right ventricle. It results in a condition in which the right ventricle is divided into a large, upper atrialized portion and small, lower functional portion. due to the small, functional portion of the right ventricle, there is reduced amount of blood available to the pulmonary trunk. It is usually associated with an ASD. The anterioposterior radiograph shows massive cardiomegaly due to enlargement of the right atrium.
- 22Foramen primum defectcaused by a failure of the AV septum to fuse with septum primum. it results in a condition in which the foramen primum is never closed and is generally accompanied by an abnormal mitral valve.
- 23Tricuspid atresia (hypoplasstic right heart)caused by an insufficient amount of AV cushion availble for the formation of the tricuspid valve. It results in a condition in which there is complete agenesis of the tricuspid valve so that no communication between the right atrium and the right ventricle exists. It is associated clinically with marked cyanosis and is always accompanied by the folllowing: patent foramen ovale, interventricular septum defect, overdeveloped left ventricle and underdeveloped right ventricle. The anteroposterior radiograph shows a normal sized heart with a convex left cardiac contour.
- 24The Interventricular Septum FormationThe muscular IV septum develops in the midline on the floor of the primitive ventricle and grows toward the fused AV cushions. The IV foramen is located between the free edge of the muscular IV septum and the fused AV cushions. This foramen is closed by the membranous IV septum, which forms by the proliferation and fusion of tissue from three sources: the right bulbar ridge, the left bulbar ridge, and the AV cushions.
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- Flashcards on Cardiovascular System- Embryology, created by Terpsichorean on 19/01/2014.
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