Term
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Definition
| From the mesoderm, migrate through primitive streak to join splanchnic lateral plate mesoderm. End up above neural plate. |
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Term
| Factors for cardiac cell differentiation |
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Definition
1. Location and timing of migration through primitive streak. Cranial to caudal ordering: those that migrate first form outflow tracts, then RV, LV, Atrium, and Sinus venosis last.
2. Growth factors such as Nkx2.5
3. Blood flow through primitive heart structures. |
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Term
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Definition
| Cells that form in mesoderm that go on to differentiate into blood vessels and cells during vasculogenesis. |
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Term
| Myocardial cell types in splanchnic mesoderm |
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Definition
| Precursor cells for epicardium and myocardium. |
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Term
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Definition
| Blood vessels sprout from existing vessels. |
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Term
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Definition
| Created when lateral plate heart fields fuse. Within the crescent, cells that are destined to differentiate into different areas of the heart (atria, ventricles, etc.) are segregated together. |
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Term
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Definition
1. Angiogenic cells cluster together in splanchnic lateral plate mesoderm.
2. Clusters form 2 endocardial tubes (inside) and myocardial cells (outside) on either side of the neural fold.
3. Surrounding myocardial cells secrete acellular cardiac jelly around the endocardial tube, keeping them separate.
4. Embryo folding causes 2 endocardial tubes and surrounding cardiac jelly and myocardial cells to fuse into one heart tube. |
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Term
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Definition
| Suspends heart tube in pericardial space |
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Term
| Segments of Primitive Heart Tube |
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Definition
From top to bottom:
1. Truncus Arteriosus
2. Outlet
3. Inlet
4. Atrium
5. Sinus Venosus |
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Term
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Definition
| Part of primitive heart tube, gives rise to aortic and pulmonary trunks. |
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Term
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Definition
| Part of primitive heart tube, gives rise to inlet, apical right ventricle, and both outlets. |
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Term
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Definition
| Inlet and apical left ventricle |
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Term
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Definition
| Part of primitive heart tube, gives rise to atrial appendages (pectinated muscle). |
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Term
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Definition
| Part of primitive heart tube, gives rise to IVC, SVC, and smooth part of right atrium. |
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Term
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Definition
| Growth factor in cardiac development that stimulates myocyte enhancer factor that controls myocyte differentiation. Homeobox gene for vertebrates, highly conserved. Not absolutely essential in differentiation. Activated by BMP. |
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Term
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Definition
| Basal attachment of the primitive heart tube. Forms component of diaphragm and sections off embryo. |
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Term
| Looping of primitive heart tube |
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Definition
1.As heart tube grows in confined space, it undergoes right (D) looping.
2. Outer curvature cells grow faster, causes ballooning of cardiac chambers.
3. Cephalic part of tube goes ventrally, caudally, and to the right. The atrial/caudal part of the tube goes dorsocranially and to the left.
4. Results in convergence of inflow and outflow valves (ends of the primitive heart tube). |
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Term
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Definition
| Growth hormone in gastrulation that initiates and maintains the primitive streak. Also upregulates growth factors involved in creating cranial/caudal and dorsal/ventral asymmetry. |
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Term
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Definition
| bHLH (basic helix loop helix) transcription factor, expressed by primitive left ventricular segments. |
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Term
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Definition
| bHLH (basic helix loop helix) transcription factor, expressed by primitive right ventricular segments. |
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Term
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Definition
1. Septum Primum migrates downward toward endocardial cushion. Gap between the septum primum and the endocardial cushion= foramen primum.
2. As septum primum migrates, fenestrations develop within that eventually become the foramen secundum. There is never complete separation of the two atria until after birth.
3. Septum primum fuses with the endocardial cushion (end of foramen primum) and septum secundum is formed through invagination of the sinus venosus. It overlaps the foramen secundum, creating the foramen ovale.
5. After birth, the septum primum and secundum fuse to close foramen ovale to form fossa ovalis. Incomplete closure=atrial septal defect. |
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Term
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Definition
1. Initially, AV canal positioned mostly over left ventricle. Endocardial cushions form along anterior and posterior walls of canal to separate atria from ventricles.
2. Asymmetric growth enlarges Av canal in rightward direction, aligns common AV canal over both ventricles.
3. Fused endocardial cushions also serve as anchoring point for valves. |
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Term
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Definition
1. Portion of myocardium covered by endocardial tissue is undermined (Sulcus), invaginates down AV canal with chamber growth.
2. Myocardium retracts, replaced by connective tissue.
Myocardium near apex forms papillary muscle. |
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Term
| Muscular Ventricular Septum |
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Definition
| 1st component of the interventricular septum, forms with growth of the ventricles. |
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Term
| Truncus Arteriosis and Conus COrdis Division |
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Definition
| Mesenchymal ridges form on the inside of the truncus arteriosis, forming the initial division between the aortic and pulmonary branches. These ridges spiral in a helical manner and eventually fuse, forming the aorticopulmonary septum. |
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Term
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Definition
| Form the aortic arch arteries and the endocardial cushions in the AP septum. System wide abnormalities can result from failure of neural crest cells to migrate to correct location. |
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Term
| Formation of membranous portion of the interventricular septum |
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Definition
| Involves contributions from 1. The endocardial cushions from the AV septum 2. Upward growth of the muscular ventricular septum 3. The endocardial cushions that form the aortoventricular septum Membranous ventricular septum is the most prone to defects because requires contribution from 3 different sources. |
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Term
| Development of semilunar valves |
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Definition
Develop from endocardial cushions that septate the conis cordis, cushions swell into 3 flaps. Since the cushions are derived from neural crest cells, improper migration of neural crest cells will result in defective semilunar valves.
Cells in the flaps grow into a thin, flat plate (through programmed cell death) and elastic and collagenous fibers proliferate in response to tension caused by blood flow. |
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Term
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Definition
| Transient group of multi-potent cells found underneath the developing AV node of the heart. These cells eventually migrate and undergo epithelial to mesenchymal transformation to form all the vasculature of the heart and the epicardium.Eventually differentiate into smooth muscle, pericytes, fibroblasts, and endothelial cells. |
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Term
| Formation of conduction system of the heart |
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Definition
4 rings develop, creating junctions in the heart tube.
Consists of SA junction, AV junction, Primary (between Bulbus and Ventricle), and Arterial (between Bulbus and Truncus).
Differentiate due to signalling from ET-1 |
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Term
| Development of systemic veins |
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Definition
| Left and Right horns of the sinus venosis give rise to Cardinal, Umbilical, and Viteline veins (2 of each). These vessels absorb into each other while the right horn growth exceeds the left. Results in formation of the SVC and IVC on the right side with the coronary sinus on the left. Sometimes left anterior cardinal vein doesn't disappear, results in problems in venous return. |
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Term
| Smooth portion of right atrium |
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Definition
| Stems from the sinus venosis differentiating into the SVC and IVC. |
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Term
| Development of pulmonary veins |
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Definition
1. Lungs originally supplied by systemic veins through the splanchnic plexus.
2. The common pulmonary vein arises from endothelial evagination just cranial to the confluence of the sinus horns.
3. The splanchnic plexus then divides into individual pulmonary veins and joins the common pulmonary vein.
4. The common pulmonary vein eventually divides into four, making up the smooth portion of the left atrium. |
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Term
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Definition
| 1. Oxygen is carried from the placenta through the umbilical vein into the IVC, which drains into the right atrium. 2. Since the lungs are not yet operational, the body wants blood to be shunted from the right atrium to the left atrium. The lungs are stiff and hard to perfuse, which creates a high pressure right atrium and a low pressure left atrium. Most of the blood shunts from the right atrium to the left through the foramen ovale. 3. The blood that manages to escape to the right ventricle is mostly shunted back to the aorta via the ductus arteriosis, while some go on to perfuse the lungs. |
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Term
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Definition
| Abnormalities in cardiac looping (D looping) causes the heart to be in the opposite orientation. |
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Term
| Types of atrial septal defects (ASDs) |
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Definition
Primum ASD (Septum Primum is too short)
Secundum ASD
Primum and Secundum ASD |
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Term
| Left to right atrial shunting |
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Definition
Not cyanotic.
Volume overload in the pulmonary circuit (too much blood in the right atrium, pulmonary artery, and lungs), may cause problems later in life. |
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Term
| Ventricular septal defects |
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Definition
| Happens mostly in the intermembranous septum. Shunting happens mostly in systole. |
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Term
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Definition
Unequal division of the Truncus and Conus arteriosis results in a larger aorta and smaller pulmonary trunk. Results in:
1. Aortic Override
2. Pulmonary Stenosis
3. Right Ventricle Hypertrophy
4. Ventricular Septal Defect, causes right to left shunting due to right ventricle hypertrophy=cyanosis. |
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Term
| Results of incorrect formation of conoventricular septum |
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Definition
1. Tetralogy of Fallot
2. Aorta to right ventricle and Pulmonary trunk to left, happens if endocardial ridges don't twist in helical fashion.
3. Incomplete division of pulmonary and aortic vessels. |
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