Embryology of the CVS Flashcards
Describe the formation of the heart tube and the vessels associated with it
- Lateral plate splanchnic mesoderm (inner C-shaped ring) forms circulatory system (and other viscera)
- Angiogenic cells collect there
- They move towards the midline
- Angioblastic cords coalesce to form two primitive heart tubes
Lateral plate splanchnic mesoderm forms…
The circulatory system.
Name the two primitive heart tubes
- Cranial end: trunks arteriosus
- Caudal end: sinus venosus
When does the primordial heart start to function?
By the 4th week - it is the first major system to form.
Where do blood vessels first appear?
- Yolk sac
- Allantois
- Connecting stalk
- Chorion
Where does the sinus venous receive blood from?
- Yolk sac (vitelline)
- Placenta (umbilical)
- Body of embryo (common cardinal)
Describe cephalic folding
Pericardial cavity: dorsal –> ventral
Cardiac tube: ventral –> dorsal
Describe the formation of the pericardium
- Derived from intraembryonic coelom
- Parietal layer of serous and fibrous pericardium derived from somatic mesoderm
- Visceral layer of serous pericardium derived from splanchnic mesoderm
Describe the formation of the bulboventricular loop
Bulbis cordially and ventricle grow faster that other regions forming U-shaped bulboventricular loop.
Describe dextrocardia
Abnormal heart looping.
- Loops to left instead of right
- Associated with situs inversus
Describe the development of the right and left atrium
Endocardial cushion: separates RA + V from LA + V
Septum: separates RA from LA and RV from LV
- Foramen secundam formed at upper end of septum primum (due to cell death).
- Septum secundum forms to the right of septum primum.
- Septum secundum grows and overlaps the foramen secundum (incomplete due to foramen ovale).
4.
Describe the developmental defects associated with the right and left atrium
Atrial septal defect;
- F>M
- Patent foramen ovale
- Causes;
1. foramen secundam
2. Endocardial cushion with foramen primum
3. Sinus venous
4. Common atrium
Describe the development of the special conducting system of the heart
- Early pacemakers: primitive atrium then sinus venosus
- SA node develops in 5th week
- AV canal and sinus venosus –> AV node and Bundle of His
- Clinical: cot death/SIDS
Describe the development of the right and left ventricle
- Musclar ventricular septum forms (opening is called interventricular foramen)
- Bottom of spiral aorticopulmonary septum + muscular ventricular septum = membranous interventricular septum
- Growth of endocardial cushion also contributes
Describe the developmental defects associated with the right and left ventricle
Ventricular septal defect;
- M>F
- Can appear in any part
- 30% close spontaneously
- Most common: membranous type
Describe the role of the foramen ovale
Before birth;
- Allows blood to pass from right to left atrium
- Prevents blood flowing back
After birth;
- Usually closes
- Become fossa ovale
- Septums fuse
- Non-closure results in ASD
What does the aorticopulmonary septum divide?
The bulbus cordis and trunks arterioles into the aorta and pulmonary trunk.
Describe the aortic arches
- 6 develop from aortic branches and pharyngeal arch arteries
- Not all present at same time
- All terminate in dorsal aorta
Describe the common abnormalities of the aortic arches
Aberrent subclavian;
- 4 regresses
- Right subclavian originates on left
- Forced to go behind trachea and oesophagus
Double aortic arch;
- Abnormal right aortic arch
- Difficulty swallowing
Patent ductus arteriosus;
- Increased work of breathing, not thriving
- May lead to congestive heart failure
Coarctation of aorta;
- Narrowing of aorta proximal or distal to DA
Primitive ventricle –>
Left ventricle
Primitive atrium
Parts of right and left atria
Sinus venosus
- Superior vena cava
- Right atrium
Describe the risk factors of congenital heart disease
- Rubella infection in pregnancy
- Maternal alcohol abuse
- Maternal drug treatment and radiation
- Genetic
- Chromosomal (Down’s, Turner’s)
Describe the transposition of the great vessels
- Common cause of cyanotic disease in newborn infants
-
Describe the transposition of the great vessels
- Patent ductus arteriosus: permits exchange of pulmonary and systemic circulation
- Common cause of cyanotic disease in newborn infants
- Causes;
1. Failure of aorticopulmonary septum to spiral
2. Defective migration of neural crest cells
Describe the transposition of the great vessels
- Patent ductus arteriosus: permits exchange of pulmonary and systemic circulation
- Common cause of cyanotic disease in newborn infants\
- F>M
- Associated with rubella in pregnancy
- Causes;
1. Failure of aorticopulmonary septum to spiral
2. Defective migration of neural crest cells
Describe the formation of the aortic sac
- First arteries to form: right and left primitive aorta
- Each has a ventral and dorsal part
- They partially fuse to form aortic sac
- Aortic branches arise from this
Describe the development of the pharyngeal arch arteries
- Develop during 4th and 5th week
- Each arch has its own nerve and blood supply
- Pharyngeal arteries communicate with aortic arches
- 6 aortic arches form on each side
Describe the fate of the aortic arches
-
Describe the fate of the aortic arches
- 1 and 2: maxillary
- 3: common carotid and first part of internal carotid
- 4 left: arch of aorta
- 4 right: right subclavian
- 6 left: left pulmonary and ductus arteriosus
- 6 right: right pulmonary
Describe the development of the lymphatic system and the thoracic duct
- Develops at end of 6th week
- 6 primary lymph sacs
- Lymphatic vessels will join later
Umbilical arteries supply…
- Dorsal aorta to chorionic villi of placenta
- Proximal persists as internal iliac and superior vesicle branches to bladder
Cardinal veins drain…
- Body of embryo
- Forms vena cabal system by anastomosis of all cardinal veins
Ductus arteriosus –>
Ligamentum arteriosum
Ductus venosus –>
Ligamentum venous of the liver
