CARDIO AND RESPIRATORY EMBRYOLOGY Flashcards
What is the first major system to function in the embryo?
The CVS
What week does the CVS start to develop ?
Week 3 and 4
Why does the cardiovascular system have to develop?
Because the embryo gets to big for diffusion along to support all the cells.
How do blood vessels form?
Little islands of blood vessel form in the yolk sac, allantois and chorion creating an cardiogenic field.
Blood vessels in the splanchnic mesoderm from two heart tubes.
Heart tubes fuse and join with blood vessels to from the primordial CVS.
How do the pericardium form?
Folding moves the pericardium so that it is dorsal to the pericardial cavity.
Fibrous and parietal layer of the pericardium from from the somatic mesoderm.
The visceral layer forms from the splanchnic mesoderm.
The pericardial cavity forms from the intra-embryonic coelom.
How do heart tubes form?
From the heart bundle heart tubes start to budge and form arterial and venous ends.
How do heart tubes form loops?
The heart tube grows in the pericardium but then gets to big and so forms a loop. This is called the bulboventriclar loop.
The bulbus cordis and ventricle enlarge and loop to the right. This pushes the ventricle left and down and the atria up and back.
What abnormality can occur in the looping of the privative heart tube?
Dextrocardia - Heart tube goes to the left so the ventricles come to lie facing the right.
How is the atrioventricular canals formed?
An endocardial cushion develops to separate the left and right side of the heart
How is the interatrial septum formed?
The septum primum and septum secundum both grow down to separate the two atrium however they leave a hole called the foramen ovule which is essential for circulation before birth. After birth the Forman ovule closes as the septum primitive and the septum secundum fuse to form the fossa ovalis.
What is a common congenital defect with the formation of the interatrial septum?
Can cause a hole in the heart
How is the interventricular septum formed?
Muscular ventricular septum forms. It has a hole called the interventricular foramen.
Parts of primitive heart
Truncus arteriosus Bulbus cordis Ventricle Atrium Sinus venosus
How are the aorta and pulmonary trunk differentiated?
Aorticopulmonary septum divides the bublis cordis and the truncus arteriosus into the aorta and the pulmonary trunk.
The aorticopulmonary septum fuses with the muscular ventricular septum and endocardial cushion and the interventricular foramen is closed.
What are VSDs?
Ventricular septal defects are ‘holes on the heart’ small once’s will close naturally. Very common especially the membranous type/
How are the heart valves formed?
Develop from the ventricular wall from the subendocardial valve tissue.
What is cyanotic disease ?
Where there has been transposition of the great vessels. It allows gas exchange from the systemic to pulmonary circulation.
How is the conducting system of the heart established?
cardiomyocytes are early pacemaker cells and are found in the atrium and sinus venosus. SA node develops during week 5
What causes SIDS?
Abnormalities in the conducting tissue
When does the aortic sac develop?
Same time blood vessels start to appear.
How do the arteries from?
Ventral aorta and dorsal aorta combine and from the aortic sac which then becomes an extension of the truncus arteriosus.
What happens to the aortic sac during week 4 and 5 ?
6 Pairs of aortic arches are formed from the aortic sac.
What two ways can blood vessels develop in ?
Vasculogenic - the formation of new vascular networks
Angiogenesis - The formation of new vessels from pre-existing vessels
What happens to the 1st and 2nd pair of aortic arches?
Disappear
What happens to the 3rd pair of aortic arches?
Forms the common carotid arteries
What happens to the 4th right aortic arch?
Right subclavian artery
What happens to the 4th left aortic arch?
Aortic arch
What happens to the 5th arch ?
Disappears
What happens to the right 6th arch?
Right arch forms the right pulmonary artery
What happens to the left 6th arch?
Left arch forms the left pulmonary artery and ductus arteriosus (closes shortly after birth)
What are the abnormalities of the arch
right subclavius artery arises from the left and constricts the trachea and oesophagus
Double aortic arch where non-regression of the right arch forms the vascular ring around the trachea and oesophagus which causes difficulties in breathing and swallowing.
Patient ductus arteriosus (PDA) where the muscular wall fails to develop and so gas exchange occurs.
Cortication of the aorta where the aorta is severely narrowed.
By what processes do embryonic vessels become adult vessels ?
Vitelline vessels supply the yolk sac and become adult gut vessels
Umbilical vessels that supply the placenta becomes the internal iliac arteries
The cardinal vessels supply the rest of the body and becomes the SVC and IVC
When does the lymphatic system begin to develop ?
Week 6
How does the lymphatic system develop?
6 lymph sacs from.
Lymph vessels join the lymph sacs.
2 Thoracic duct develop from the to vessels anterior to the aorta.
The left one becomes the adult thoracic duct.
What are the three foetal circulation shunts ?
Ductus venous
The foramen ovule
The ductus arteriosus
How does the ductus venous close?
The ductus venous becomes the ligamentum venosum of the liver, the foramen ovule closes after birth to form the fossa ovalis of the heart
What is the Ductus venous
Ductus venous shunts blood in the left umbilical vein directly to the IVC bypassing the liver.
What is the foramen ovule
The foramen ovule shunts blood from the right atrium to the left atrium bypassing the lungs.
What is the ductus arteriosus
The ductus arteriosus shunts blood from the right ventricular and pulmonary arteries to the aorta bypassing the lungs
How does the foramen ovule close?
foramen ovule closes after birth to form the fossa ovalis of the heart,