Embryology - CVS 1 Flashcards
(22 cards)
What happens in week 3?
- lateral plate splanchnic mesoderm forms circulatory system + other viscera
- Mesoderm cells move through the midline towards embryo’s head.
- Endoderm cells releases VEGF which signals the mesoderm cells of the limbs coalesce into 2 primitive heart tubes.
When does the heart start to function?
Week 4
Describe the formation of the heart tubes and blood vessels
- Blood vessels appear in wall of yolk sac, allantois connecting stalk and chorion.
- Appearance angioblastic cords appears in the mesoderm in week 3.
- Angioblastic cords canalize to form heart tubes and the tubular heart now joins BVs in other areas to form the primordial cardiovascular system
Describe the formation of the pericardium
- cranial folding of embryo ( reorientation of heart tube dorsal to perocardial cavity)
- Parietal + fibrous pericardium = somatic mesoderm
- visceral layer of serous pericardium = splanchnic mesoderm
Where is the pericardium derived from?
-intra-embryonic coelom
Describe the venous end (sinus venosus) of the heart tube + what is the sinus venosus
VENOUS end - ( inflow tract)
- consists of Two horns ( right and left)
- each get venous blood via the viteline vein from the yolk sac and placenta ( via umbillican vein)
- body of the embryo ( via common cardinal vein)
Describe the truncus arteriosis ( arterial end)
ARTERIAL END - ( outflow tract)
- aortic arches arises from aortic sac
- pumps blood through aortic sac into aortic arches
Describe the formation of the cardiac ( bulboventricular) loop
- Heart tube loops to the right side and lies facing the left. First part of bulbus cordis grows right ventricle + they form U-shaped bulboventricular loop
- during development, growing ventricle moves to left + visceral pericardium = epicardium. ??? OSMOSIS
Bulboventricular loop consists of bulbis cordis and ventricle(s?)
What does abnormal cardiac looping lead to and how?
- dextrocardia
- heart tube loops to the left hand side ( instead of the right ) thus coming to lie facing the right
- associated with situs inversus ( visceral organs are reversed or mirrored from their normal positions.)
Describe the formation of the endocardial cushion
- occurs 27th-37th day
- Endocardial cushion formation + septum formation
Endocardial cushion formation
- Mesoderm proliferates + forms endocardial cushion. This forms the L/R AV canals.
- On ventricular side of AVC, endocardial cells proliferates to form the mitral/tricuspid valves. Atria is now divided from ventricles.
Causes of ASD and VSD
ASD( atrial septal defect) and VSD are associated with defective formation of endocardial cushion and septum formation
Partitioning of primordial heart -Describe the septum formation in the atria
- In atrium, septum primum ( between L/R atria) grows downwards towards the endocardial cushion(fuses) closing the gap ( ostium primum). A hole(apoptosis) then appears in ostium primum = ostium secundum.
- The septum secundum grows downwards to the right of septum primum + covers the ostium secundum + leaves another opening = foramen ovale. This creates valve that allows blood to move from RA>LA
Partitioning of primordial heart -Describe the septum formation in the ventricles + PA/aorta
- Muscular ventricular septum forms + opening = intraventricular foramen.
- Bottom of spiral aorticopulmonary septum fuses with muscular ventricular septum = forming membranous interventricular septum, closing interventicular foramen.
- Aorticopulmonary septum divides bulbis cordis + truncus arteriosus =aorta + pulmonary trunk
- The growth of the endocardial cushions will also contribute to the membranous portion of the interventricular septum.
Describe the role of the foramen ovale before/after birth
Before birth
- allows most of blood to pass from right atrium to left atrium ( non functioning lung)
- prevents backflow of blood, blood mixes
After birth
- it closes ( increased pulmonary blood flow and shift of pressure to left atrium
- septum primum ( valve of the oval foramen ) fuses with the septum secundum
- oval fossa ( fossal ovalis) of the adult heary is a remnant of foretal oval foramen
- non-closure results in PFO ( patient foramen ovale ) = atrial septal defect (ASD) «_space;hole in heart
Features of atrial septal defect
- common females>males
- common - patent foramen ovale-4 typrd
VSD ( ventricular septal defect
- M>F
- appears in any part of semptum
- membranous type of VSD most common
- small VSDs closes spontaneously
Cot death/sudden infant death syndrome cause
abnormalities of conducting tissue
VSD ( ventricular septal defect
- M>F
- appears in any part of semptum
- membranous type of VSD most common
- small VSDs closes spontaneously
Transporisiton of great vessels
- most common cause of cyanotic disease in infants
- associated with ASD/VSD
- permits exchange of systemic + pulmonary circulation
Caises
- Failure of aorticopulmonary septum to take a sprial course
- Defective migration of neural crest cells
Eg. Teratology of the fallot
Teratoloy of the fallot
Made up of 4 cardiac defects:
- Pulmonary stenosis ( obstruction of right ventricular outflow)
- Ventricular septal defect (VSD)
- Dextroposition of aorta ( override of aorta)
- Right ventricular hypertrophy
Causes of teratology of the fallot
-unequal division of the conus due to anterior displacement of aorticopulmonary septum
Transporisiton of great vessels
- most common cause of cyanotic disease in infants
- associated with ASD/VSD
- permits exchange of systemic + pulmonary circulation
Causes
- Failure of aorticopulmonary septum to take a sprial course
- Defective migration of neural crest cells
Eg. Teratology of the fallot
