Development of Heart and Fetal Circulation PDF

DEVELOPMENT OF THE HEART Dr Eid Nassar Ali Anatomy department Taibah university the cardiovascular system is the first functioning system. the heart starts contraction by day 22 of gestation. 2 heart tubes appear first , then fuse to form single heart tube The heart tube...

DEVELOPMENT OF THE HEART Dr Eid Nassar Ali Anatomy department Taibah university the cardiovascular system is the first functioning system. the heart starts contraction by day 22 of gestation. 2 heart tubes appear first , then fuse to form single heart tube The heart tube shows 5 expansions 1. Sinus venous ( most caudal). 2. Common (primitive) atrium. 3. Common ventricle. 4. Bulbus cordis. 5. Truncus arteriosus. Cardiac looping the heart tube becomes U shape then S shape finally it takes the final shape of the heart chambers  Sinus venosus consists of body + 2 horns, each horn receives 3 veins: I. umbilical vein. II. Vitelline vein. III. common cardinal vein  Derivatives of sinus venosus PART DERIVATIVE Body and right horn Posterior wall of right atrium Left horn Coronary sinus  Development of the atria Right atrium Left atrium 1- common atrium 1- common atrium 2- right ½ of the 2- Left ½ of the atrioventricular canal atrioventricular canal 3- sinus venosus 3- pulmonary veins  Formation of the interatrial septum Derived from : 1. Septum primum 2- Septum secundum The gap between the septum secondum and the septum primum is called ' foramen ovale ". - Foramen ovale closes just before birth  Development of the ventricles. The bulbus cordis Develop from 2 sources: 1. Common ventricle. 2. The bulbus cordis. Common ventricle Interventricular septum 1. Muscular part: 2. Membranous part:  Truncus arteriosus Divided into ascending aorta and pulmonary trunk by aortico-pulmonary septum.  Summary of heart tube and its derivatives Cardiac dilatations Derivatives Truncus arteriosus - Ascending aorta - Pulmonary trunk Bulbus cordis -Smooth part of the right ventricle - Smooth part of the left ventricle Primitive ventricle - Rough part of the right ventricle - Rough part of the left ventricle Sinus venosus - Smooth part of right atrium - Coronary sinus Primitive atrium - Rough parts of right and left atria Congenital anomalies of the heart Dextrocardia: Atrial septal defects (ASD) Ventricual septal defects The apex of the heart a mixing of oxygenated and (VSD) directed to the right - Associated with transposition deoxygenated blood leading to Presence of foramen in the of the abdominal viscera ( situs muscular/membranous part cyanosis, breathlessness. inversus).  Tetralogy of Fallot 1- Ventricular septal defect. 2- Pulmonary stenosis. 3- Right ventricular hypertrophy. 4- Overriding aorta. Symptoms - Shortness of breath and rapid breathing, especially during feeding or exercise - cyanosis transposition of great arteries (TGA) aorta arises from the right ventricle and pulmonary trunk from the left ventricle FETAL CIRCULATION  Oxygenated blood passes from placenta by the left umbilical vein which joins the left branch of the portal vein and connected to inferior vena cava (IVC) by ductus venosus.  Blood brought by the IVC to the right atrium is directed through foramen ovale to the left atrium  Then through the mitral valve to the left ventricle.  ,to the aorta and so the carotid and subclavian arteries  Deoxygenated blood enters the right atrium from the upper part of the body by superior vena cava (SVC)  It and passes through tricuspid valve to the right ventricle  Then, from the right ventricle to pulmonary trunk  Droxygenated blood reaches aorta via ductus arteriosus which connects aorta and left pulmonary artery  Blood passes down to the aorta and through the umbilical arteries to the placenta to be oxygenated. Changes in circulation 1) The foramen ovale is closed 2) The ductus arteriosus is closed forming ligamentum arteriosum 3) The ductus venosus is closed and becomes ligamentum venosus 4) The left umbilical vein is closed and becomes ligamentum teres 5) Umblical arteries become obliterated  Applied anatomy Patent ductus arteriosus (PDA) causes mixing of oxygenated and deoxygenated blood leading to cyanosis.