Heart Development PDF

Heart Development Dr. April Hatcher MN212 [email protected] Oxygen poor Oxygen rich Right Atrium Left Atrium Right Ventricle Left Ventricle  Differentiation of heart tubes...

Heart Development Dr. April Hatcher MN212 [email protected] Oxygen poor Oxygen rich Right Atrium Left Atrium Right Ventricle Left Ventricle  Differentiation of heart tubes Separation of Fusion of heart chambers heart tubes c Folding & looping of heart tubes 0  Heart Development Formation of the primitive heart and vascular system begins during week 3. Heart starts beating by the beginning of week 4. The heart initially serves as a one-way pump to transport oxygen- nutrient laden blood from the placenta to the body of the embryo via the umbilical vein, then returning the oxygen-poor blood back to the placenta via the umbilical arteries. heart of and caudal nuters and blood vestal Haves  Heart Development Primary heart field Neural plate Containing myoblasts and blood islands Cut edge of amnion 3 weeks At the rostral end of the embryonic body in an area called the primary heart field, mesodermal cells aggregate to form longitudinal cellular strands termed angioblastic cords.  Heart Development Cut line for C B. Transverse folding Cut line for B Blood islands within the splanchnic mesoderm-these will form blood cells/vessels by vasculogenesis C. Longitudinal folding Developing heart in pericardial cavity Longitudinal (cranial/caudal) folding (Figure C) positions the heart in the region of the thorax.  Heart Development Intraembryonic coelom (cavity) Blood islands within splanchnic mesoderm 17 days Endocardial tubes Myocardial cells (red dots) are located superficial to these 18 days islands. Embryonic folding brings the two endocardial tubes into the thorax where they meet along the midline and fuse to form a single tube.  Differentiation of the heart tube Ventricle Bulbis cordis tailand Sinus venosus Aortic arch vessels Truncus thad and Atrium arteriosus ---Pericardial sac  Heart Development AT Blood enters the caudal end of the tube, the sinus venosus, which receives blood from: 1. the body via the common cardinal veins 2. the placenta via the umbilical veins 3. the yolk sac via the vitelline veins From the sinus venosus, blood flows cranially into the primitive atrium. From the atrium, blood enters the primitive ventricle.  Heart Development From the ventricle, blood is pumped to the bulbis cordis which drains into truncus arteriosus. The truncus is continuous cranially with the expanded aortic sac from which the aortic arches arise. Blood flows from the aortic arches into the dorsal aortae in order to reach the embryonic body, the placenta and the yolk sac.  Heart Development Primitive ventricle moves ventrally, caudally and to the right Primitive atria moves dorsally, cranially, and to the left Folding of the primitive heart tube brings the four putative chambers of the adult heart into the correct spatial relationship with one another.  Heart Development Partitioning the primitive heart As the heart is bending and enlarging, its original single chamber begins to be partitioned in order to separate the systemic and pulmonary circulations. Four sets of partitions form simultaneously in the atrium and the ventricle during weeks 4-5. These partitions will separate: 1) the atria from the ventricles values between 2) the right and left atria 3) the right and left ventricles 4) the pulmonary trunk and ascending aorta  Heart Development Atrial Septation The division of the primitive atrium occurs in two phases. A partial partition is formed before birth allowing blood flow between atria. The partition is functionally completed at birth. Blood from the right atrium then flows to the right ventricle and pulmonary trunk for delivery to the functioning lungs.  Heart Development Atrial Septum Formation: Septum Primum Septum primum grows from the roof of the common atrium. It extends toward the endocardial cushions, which are fusing to create the AV septum. The ostium (foramen) primum is the opening between the septum primum and the endocardial cushions. Line of sight Septum primum Line of sight Region of cell death h Septum primum LA RA Ostium primum EC EC EC EC EC LV RV Ostium primum 1ˢᵗ hole endoca El  Heart Development Atrial Septum Formation: Septum Secundum The septum secundum grows down from the roof of the atrium immediately to the right of septum primum. It gradually overlaps septum primum. holy m7 Ostium secundum Ostium secundum Septum primum Septum Fr secundum EC EC EC EC Septum secundum 2nd wall  Heart Development Atrial Septum Formation: Septum Secundum The septum secundum grows down from the roof of the atrium immediately to the right of septum primum. It gradually overlaps septum primum. Fossaovalis Foramen ovale Valve of foramen ovale Membranous portion of interventricular septum Muscular portion of interventricular septum 37 days 7 weeks  Heart Development Before birth: foramen ovale shunts most blood entering right atrium to the left atrium and prevents passage of blood in the opposite direction since septum primum closes against the relatively rigid septum secundum. After Birth: functional closure of foramen ovale is facilitated by decreased right atrial pressure (occlusion of placental circulation) and increased left atrial pressure (due to increased pulmonary venous return). Septum primum is pressed against septum secundum and they adhere, forming fossa ovalis. Anatomical closure occurs within the 1st postnatal year. Septum secundum Foramen ovale (opening) (---) Peering through this to the red valve of foramen ovale (formerly septum primum)  Heart Development Once foramen ovale closes following birth, it is renamed fossa ovalis and is representative of an embryological remnant of heart development.  Heart Development Partitioning the primitive heart As the heart is bending and enlarging, its original single chamber begins to be partitioned in order to separate the systemic and pulmonary circulations. Four sets of partitions form simultaneously in the atrium and the ventricle during weeks 4-5. These partitions will separate: 1) the atria from the ventricles 2) the right and left atria 3) the right and left ventricles 4) the pulmonary trunk and ascending aorta  Partitioning bulbis cordis and truncus arteriosus: Formation of the pulmonary trunk and ascending aorta Without partitioning, there would be only B one outflow path from the fused ventricles. More specifically, the Yas Development of the aorticopulmonary upper portion of septum creates two outflow paths, aorta bulbis cordis is called and pulmonary trunk. Development is the conus cordis timed to coincide with completion of the interventricular septum so that when two separate ventricles are formed, there will Aorta be an outflow path for each. Aorticopulmonary septum Truncus arteriosus Conus cordis Pulmonary trunk  Heart Development During week 5, the aorticopulmonary septum develops from swellings in the walls of the truncus arteriosus and the upper region of the bulbis cordis, known as the conus cordis. These conotruncal ridges are populated by neural crest cells that have migrated to these regions. The ridges are continuous with one another, forming a complete septum, dividing the bulbis and truncus into two arterial channels, the aorta and the pulmonary trunk. toward calls growing No  Heart Development Formation of the aorticopulmonary septum begins at the inferior end of the truncus and proceeds superiorly and inferiorly. The aorticopulmonary septum forms a spiral, due to the position of the truncal and conus swellings and their specific pattern of growth. The free edges of each ridge unite in the center of the truncus lumen to form a spiraling wall, effectively separating the ascending aorta and pulmonary trunk, and aligning these structures with their respective ventricles. 4 Has to spiral  Heart Development Partitioning the primitive heart As the heart is bending and enlarging, its original single chamber begins to be partitioned in order to separate the systemic and pulmonary circulations. Four sets of partitions form simultaneously in the atrium and the ventricle during weeks 4-5. These partitions will separate: 1) the atria from the ventricles 2) the right and left atria 3) the right and left ventricles 4) the pulmonary trunk and ascending aorta  Heart Development Ventricular septation Left Pulmonary Right conotruncal channel conotruncal Aortic ridge channel ridge R L Muscular portion of the Endocardial cushions interventricular septum contributing to the membranous portion of the interventricular septum The interventricular septum consists of a muscular and membranous portion. Complete closure of the interventricular septum is dependent on fusion of the endocardial cushions with the downward spiraling aorticopulmonary septum—these two components form the membranous portion of the interventricular septum.  Interventricular Septum Thick portion— the muscular interventricular septum. Thin portion— R L located where the valves attach and known as A A the membranous portion of the interventricular septum RV L membranous V =Fibrous atrioventricular septum Coronal view of heart  Heart Development Embryonic Adult Derivative/s structure Primitive atria Auricles of right and left atria Right horn of Smooth part of the right atrium (sinus venarum) sinus venosus Left horn of sinus Coronary sinus venosus Primitive Smooth part of left atrium pulmonary veins Conus cordis Outflow tract for both ventricles: conus arteriosus (infundibulum) for (upper bulbis right ventricle and aortic vestibule just below aortic valve for left cordis) ventricle Bulbis cordis Trabeculated right ventricle Primitive ventricle Trabeculated left ventricle Truncus Ascending aorta and pulmonary trunk arteriosus