Development of Heart Flashcards
Define what gastrulation is
Process by which single layered blastocyst turns into multi-layered structure
Describe the first part of the formation of the endocardial tube
Day 17 - lateral plate mesoderm divides into visceral and somatic layers. IN visceral layer, angiogenic cell clusters named blood islands appear.
What is the function of blood islands?
They will differentiate into primordial vascular system, heart tube, vessels and primordial erythrocytes.
What occurs after the formation of blood islands?
The blood islands coalesce to give right and left endocardial tubes and dorsal aortae. Part of mesoderm differentiates into cardiomyocytes and visceral lateral plate mesoderm approach eachother (day 20)
Describe the events that occur after formation of endocardial tubes and dorsal aortae?
The folds of embryo fuse along ventral midline and the space between the visceral and somatic mesoderm becomes the intraembryonic coelom. Myocardium forms deep to visceral lateral plate mesoderm
What is the function of the intraembryonic coelom?
It will become the paricardial cavity in the thoracic cavity.
Describe the events that occurs after the formation of the intraembryonic coelom
Cephalo-caudal and lateral folding (meet at the umbilicus). Lateral folding allows Right and Left endocardial tubes fuse to form the primary heart tube, anterior to gut tube. The myocardium invests into the cardiac jelly and endocardial heart tube.
On what day does the heart start to beat?
Day 22
What does cephalo-caudal folding cause?
The heart tube to effectively migrate from head end, through the neck to the thorax
Name the parts of the endocardial tube
Aortic arch, aortic sac, bulbus cordis, primordial ventricle, primordial atrium, sinus venosus.
What is the function of the sinus venosus?
At the caudal end and it receives the blood from the umbilical, vitelline and cardinal veins
What is the function of the vitelline vein?
Drain the yolk sac
What is the function of the cardinal vein?
Drain the trunk and head region
Describe features of the bulbus cordis
It is the outflow tract and has two parts; Conus cordis - aorta and the truncus arteriosus - pulmonary trunk
Describe the looping and folding of the heart tube
Starts at about 22 days. The two ends fold towards each other and to the right which pushes the apex to the left. It rotates slightly so right side is more anterior. Atrium bulges out on each side of bulbis cordis
Describe how dextrocardia develops?
It the ends of the heart tube fold to the left then the heart is pushed to the right
Describe what parts of the bulbis cordis will form?
Proximal part - Right ventricle, Middle part - Outflow of venticles. Distal part - Pulmonary trunk and aorta
What is the narrowing between the atrium and ventricles called? What is it surrounded by?
The avioventricular canal. This is the lumen of the heart tube. It is surrounded by dense mesenchymal tissue called cardiac jelly which is produced by and replaced by myocardium.
What is the myocardium derived from?
Splanchnic mesoderm
What are endocardial cushions derived from and what do they form?
Derived from neural crest cells, they form the interatrial septum, the membranous part of IV septum, the AV valves and form the PT and aorta from the truncus arteriosus.
Describe the formation of the tricuspid and mitral valves, the papillary muscles and chordae tendineae
The tissue in the narrowing between the atrium and ventricle swells to form endocardial cushion that grow and meet in the middle and divide the AV canal into right and left channels. Endocardial cushion growth and cavitation form papillary muscles and chordae tendineae.
Describe the formation of the interatrial septum
Septum primum grows towards AV cushions, but blood can still flow from the right atrium to left atrium via the foramen primum
Describe the formation of the foramen secundum
Before the septum primum completely builds up the IA septum and the foramen primum closes, a second hole appears high up on the septum primum, called the foramen secundum
Describe the formation of the foramen ovale
A second septum begins to grow from the sinus venosus but does not fuse with the endocardial cushion and so it forms the foramen ovale
What are the conus cordis and truncus arteriosus? What are their functions?
Neighbouring sections of a single tube. The conus cordis becomes the aortic vestibule on the left side and the infundibulum on the right side. The Truncus arteriosus forms the aortic arch and pulmonary trunk.
Describe the formation of the aortico-pulmonary septum
Within the conus cordis and truncus arteriosus, two selling appear and grown from the sides of the bulbis cordis. They meet and spiral together forming the septum.
What would occur if there was no spiral to the aortico-pulmonary septum
The left ventricle would pump blood to the pulmonary artery and the right ventricle would pump blood to the aorta
Name the three structures must fuse to separate the ventricles
Endocardial cushions, IV septum and spiral septum.
What causes a patent foramen ovale?
Failure of fusion of the foramen ovale or the foramen secundum
What completes the formation of the IV septum?
Endocardial cushions sending an extension towards the muscular part of the IV septum
