fetal heart development Flashcards
development of the cardiovascular system
Is the first thing that develops after fertilisation, begins to develop at the end of the third week and starts to beat at the beginning of the fourth week.
first stage of heart devlopment
the heart starts as 2 epithelial tubes, the right endocardial tube and the left endocardial tube. the two tubes merge together to form a single chambered heart and starts to show indetifyable features of the heart. it starts pumping blood around the 4th week.
simple epithelial heart tube cross section
made up of cardiac jelly, which is mass of cells containing little nuclei and cardiac mantle, which gives rise to the myocardium. this tube sits in the embryos pericardial cavity.
3 specific areas of the heart tube
cranial portion, caudal portion and bulbus cordis. The cranial one third of the tube dilates to form the aortic sac. The caudal one third to one half also dilates to form the atria.
3 areas of development of the bulbus cords
the proximal one third gives rise to the body of the right ventricle, the remaining two thirds is split into two sections. the distal- most section is the truncus arteriosus which develops in the aortic root and the ascending aorta. the remaining mid portion is called the cornus cordis which connects the primitive right ventricle to the cornus arteriousus.
what happens to the cardiac jelly
cardiac jelly is still in the tubes and starts to act as a valve to prevent backflow. there is a forward flowing circulation at this point.
24th day
primitive ventricles start to expand, cardiac jelly develops a scaffolding,(some of it is valves and some of it is scaffolding) the scaffolding is called trabecula.
fetal circulation and the lungs
the blood doesn’t go to the lungs as it isnt a breathing fetus. we need the lungs to grow, so there’s only a limited amount of blood that goes to the lungs. the pressure in the lungs is higher to prevent blood flow from going into the lungs. The ductus arteriosus stops all the blood from going to the lungs. most of the blood will go down the descending aorta to the boy.
how does blood flow from the mother to the fetal heart
bound to the maternal circulation. oxygenated blood is transferred via umbilical vein. Usually blood goes straight to the left side of the heart, however blood goes to the right side and the oval foramen has an opening allowing oxygenated blood to flow to the left side.
