Embryonic Development Of The Cardiovascular System Spring 2024 Ross University PDF

EMBRYONIC DEVELOPMENT OF THE CARDIOVASCULAR SYSTEM SPRING 2024 María José Navarrete Talloni, DVM, MPVM, PhD...

EMBRYONIC DEVELOPMENT OF THE CARDIOVASCULAR SYSTEM SPRING 2024 María José Navarrete Talloni, DVM, MPVM, PhD Department of Biomedical Sciences, RUSVM Disclaimer: Images and information in this presentation come from different sources including Drs. I. Irimescu, O. Illanes, M. Smith, M. Zibrin, P. Hanna and H. Bogdanovic‘s notes. Dellmann’s and Junqueira’s histology books, P. Hyttel et al. and K. Moore embryology books. This presentation is for teaching purposes only, please do not distribute.  Office Hours Calendar Link on CANVAS: Book time to meet with me Email: [email protected] (Mo-Fri)  Overview 1. The basics of embryonic cardiovascular development 2. Fetal cardiac development (the partitioning of the heart) 3. Closure of the foramen ovale (functional/physiological vs. anatomical) 4. Fetal circulation – particularities and what happens after birth The cardiovascular system is the 1st functional system in the embryo Why? Because of how the embryo feeds  Early phases of the embryo – diffusion from fluid secreted by uterine glands Embryo quickly increases in size and complexity this system of nutrition becomes insufficient urgent: a circulatory system  Background Mesoderm mesenchyme (pluripotent cells) angioblastic tissue (hemangioblasts) cardiovascular system The process of blood vessel development is called angiogenesis.  Embryonic disc CR NEURAL G PLATE CD Dorsal view Cardiogenic field (1): Horseshoe-shaped structure located around the anterior and lateral portions of the neural plate. This is an area of blood-forming cavities in the visceral mesoderm that will coalesce and form the primitive heart, blood vessels and blood cells  Antero-posterior folding of the embryonic disc C D CR A B CD Lateral views E F G Cardiogenic field (A) horseshoe-shaped tubes first composed of only endothelial cells (1) and then (E) the endocardial heart tubes (3). They will make contact caudally with the developing venous system (4,5). The caudal portion (7) fuses th count withand becomes surrounded by myoblasts to form the myocardium formation of the cardiac tube. From Domestic Animal Embryology; Hyttel, Sinowatz and Vejlted, Saunders Elsevier, 2010.  G F E Lateral views CR CD H I (H) The cardiac tube at this point is composed of the bulbus cordis (10), precursor of the right ventricle, ventricle (11), and atrium (12) which joins the venous system. (I) Later on, a loop formation occurs, the process that in conjunction with a relatively complex division of the cardiac tube into 4 chambers (partitioning of the primitive heart) will result in the formation of the blood pumping organ necessary for the survival of the neonate (13). CR CD H Lateral view I CR CR CD Heart Tube after loop formation CD Dorsal view Lateral view Defects in aortic arches development defects of the great arteries of the body!  FLASH QUIZ! How many chambers does a… a) Fish 2 b) Amphibian 3 c) Reptile 3 d) Bird e) Mammal 4 … heart have? 2 - Chambered So, how do we get To here? from here… ? LA RA LV RV *Image:Medlineplus  Partitioning of the atrio-ventricular canal Primitive atrium divided into left and right atria Primitive ventricle divided into left and right ventricles Truncus arteriosus divided into outflow tracts of aorta and pulmonary trunk Heart embryology video: https://www.youtube.com/watch?v=RpZHiwkFUM4  Development provides for fetal circulation and mechanism for Normal Heart Development ultimate shift to neonatal circulation. LA LA LA RA RA RA RV LV RV LV RV LV membranous portion of Muscular portion of interventricular septum interventricular septum Figure 7-25 (Dyce) The partitioning of the atrium and ventricle, schematic. A, The primary atrial septum has formed, and development of the interventricular septum has begun. B, The primary atrial septum has fused with the endocardial cushions, and a secondary foramen (5) has been formed. C, The secondary atrial septum has formed, and a passage (foramen ovale) between primary and secondary septa connects the right and left atria. Note the fusion of the interventricular septum with the endocardial cushions. 1, Sinuatrial opening; 2, primary atrial septum (septum primum); 3, secondary atrial septum (septum secundum); 4, ostium primum; 5, ostium secundum; 6, fused endocardial cushions; 7, interventricular septum. Atrial Partitioning From body From lungs Ostium primum (4) allows the initial passage of blood from the right to the left atrium, as the primary atrial septum grows. RA LA awh mine Primary septum (septum primum) (2) AVC AVC RV LV V V Ostium (foramen) primum (4). View from the right atrium to left atrium AVC = endocardial cushion (6) To body A = atrium V = ventricle To lungs Apex of Heart  Atrial Partitioning When the ostium primum (4) closes, it is replaced by the ostium secundum (5). RA LA Blood is still passes from the RA to the LA. Primary septum (septum primum) (2) RV LV AVC Ostium (foramen) secundum (5). V Apex of Heart Atrial Partitioning The secondary septum (septum secundum) (3) grows to the right of the primary septum (2). RA LA Secondary septum (Septum secundum) (5) Border of the foramen ovale RV LV V Primary septum (Septum primum) (2) Primary septum serves as a valve for FORAMEN OVALE. Apex of Heart  sideftp.ssn.ro Atrial Partitioning of the left night sid te f The primary septum (2) serves as the VALVE for the foramen ovale in the RA LA secondary septum, preventing return of blood into the right atrium. Secondary septum (3) Border of the foramen ovale RV LV V Remember the ostium secundum (5) Primary septum (2) is still present, but hidden by the secondary septum. Apex of Heart Atrial Partitioning From Lungs From body AFTER BIRTH High Five! Lungs expand with first breaths RA LA creating a sudden blood pressure PRESSURE drop in the pulmonary circulation. DROP! This pushes the primary septum PRESSURE against the secondary one, DROP! (physiological closure of the RV foramen ovale). LV These fuse and the foramen ovale becomes the fossa ovalis (anatomical closure). To body To lungs Apex of Heart  Normal Heart Development The truncus arteriosus (most cranially) gets divided into ascending aorta and pulmonary trunk by a spiral spiral aortico- pulmonary septum. The spiral formation of the septum ensures that blood from the right ventricle flows into the pulmonary trunk and that the blood from the left ventricle flows into the ascending aorta.  Normal Heart Development Had the septum been straight, a condition known as transposition of the great vessels develops, in which deoxygenated blood from the right ventricle flows into the ascending aorta and the highly oxygenated blood from the left ventricle flows into the pulmonary trunk (lungs). This anomaly is incompatible with life.  FINALLY… How does the fetal blood flow from and to the placenta? What changes in blood circulation need to happen soon after birth, when the lungs become functional?  Prior to birth, fetal circulation is designed for the in utero aqueous environment, where the placenta oxygenates fetal blood. Follow the pathway If from placenta to umbilical arteries… Note the coloration of the different mixes of fetal i blood, depending on where one looks at the system.  Fetal blood circulation Lung Lung The lungs get little blood, as they aren’t functional yet. Three blood shunts are necessary: I Ductus venosus Ligamentum Liver venosum Foramen ovale Fossa ovalis Ductus arteriosus Ligamentum arteriosum All three must close very soon after birth! Neonate/Adult vs Fetal blood circulation Lung Lung Liver Normal heart *Image:Medlineplus