Development of the Cardiovascular System Flashcards
What are the main stages of heart development?
Bilateral heart primordia
Primitive heart tube
Heart Looping
Atrial and Ventricular septation
Outflow tract septation
When the CVS start functioning in the embryo?
4th week
Why does the CVS function first in an embryo?
Rapidly growing embryo needs nutrition but diffusion is not sufficient to satisfy
What is the cardiogenic field?
Blood vessels (islands) first appear in the yolk sac, allantois, connecting stalk and chorion
What happens to blood vessel in lateral plate splanchnic mesoderm at 3 weeks?
Form 2 heart tubes
What happens in the 3rd week?
Blood vessels (islands) appear
2 heart tubes form
These heart tube fuse and join blood vessel in other areas to form the primordial CVS
Where does the parietal and fibrous layer of pericardium form from?
Somatic mesoderm
Where does the visceral layer of the pericardium form from?
Splanchnic mesoderm
Where does the pericardial cavity form form?
Intraembryonic coelom
Where does embryo heart tube lie to the pericardial cavity?
Dorsal to pericardial cavity
With the cranial folding of embryo heart tube
Describe the fused primitive heart tube?
Heart tube starts to bulge and differentiate into arterial (cranial) and venous (caudal) ends
What are the sections of the fused primitive heart tube from outlets to inlets?
Truncus arteriosus has outlets
Bulbus cordis
Primitive Ventricle
Primitive Atrium
Sinus Atrium
Sinus Venosus has the inlets
What happen when growing heart tube becomes too large for pericardium?
Needs to fold/loop to become the bulboventricular loop
What does G. Cephalic end of heart tube supply?
Arteries
What does the caudal end of the heart tube supply?
Veins
Describe the formation of the bulboventricular loop?
Bulbous cordis and ventricle enlarge and loop to the right
Ventricle pushed left and inferiorly
Atria pushed superiorly and posteriorly
When does the heart begin and end enlarging and looping to the right?
Begins at 23 days
24 days is when ventricle pushed eft and inferior
35 days is when ends
What does abnormal cardiac looping lead to?
Dextrocardia
Explain dextrocardia
Heart tube loops to the left side instead of right so ventricles come to lie facing the right
Most frequent positional abnormality of the heart
What is actively grown to produce partitions in the heart?
Endocardial cushions and heart septae
What does endocardial cushion growth causes?
Separates the right atrium and ventricle from left atrium and ventricle to form left and right AV canals
Describe the formation of the foramen ovale
Formation of septum primum and ostium primum first
Then ostium secundum begins to form as apoptosis of part of septum primum
Formation of septum secundum and ostium secondum is complete
Closure of ostium primum as spetum primum meets endocardial cushion
What is the purpose of the foramen ovale before birth?
Allows one-way shunt allowing blood to move from right atrium to left atrium
Prevents the passage of blood in opposite direction
What happens to foramen ovale after birth?
Normally closes due to the increase pressure in left atrium
Septum primum fuses with septum secundum
Becomes the fossa ovalis (a depression)
What happens if there is non-closure of the foramen ovale?
Patent foramen ovale
A common form of congenital atrial septal defect
What happens when muscular septum forms?
Creates opening called the interventricular foramen
What does the aorticopulmonary septum divide?
Divides the bulbis cordis and truncus arteriosus into the aorta and pulmonary trunk
What happens when bottom of aorticopulmonary septum fuses with muscular ventricle septum and endocardial cushion?
Forms membranous interventricular septum which closes the interventricular foramen
Explain ventricular septal defect (VSD)
Most common type of congenital heart disease
Can appear in any part of the septum
Small VSDs close spontaneously
Membranous type of VSD is most common
What week does the aorticopulmonary septum divide Bulbous cortis and truncus arteriosus?
5th week of development
What does the aorticopulmonary septum divide the BC and TA into?
Aorta and pulmonary trunk
Explain transposition of great vessels?
Common cause of cyanotic disease in newborn infants
Associated with ASD and VSD
Permit exchange between systemic and pulmonary circulation - tetralogy of Fallot
What are the causes of transposition of great vessels?
Failure of aorticopulmonary septum to take a spiral course
Defective migration of neural crest cells to the heart
What develops from the ventriclar walls?
Cusps, chordae tendineae and papillary muscles
What develops from the subendocardial valve tissue?
Semilunar valves
When does the SA node develop?
5th week
What does AV node and bundle develop from?
Cells of AV canal and sinus venosus
What are early pacemakers called?
Cardiomyocytes in primitive atrium and sinus venosus
What can cause clot death or sudden infant death syndrome?
Abnormalities in conducting tissue
What are the derivatives of the aortic sac?
Aortic arches
What are the derivatives of the Bulbous cordis?
Right ventricle and parts of the outflow tract
What are the derivatives of the primitive ventricle?
Left ventricle
What are the derivatives of the primitive atrium?
Parts of right and left atria
What are the derivatives of the sinus venosus?
Superior vena cava and right atrium
What are the first arteries to appear in the embryo?
Right and left primitive aorta
What does each primitive aorta have?
Ventral part and dorsal part
How is the aortic sac formed?
Fusion of 2 ventral aortae
Becomes extension of truncus arteriosus
Aortic arch branches arise from aortic sac
What happens during weeks 4 and 5?
6 pairs of aortic arches are formed from the aortic sac and these unite with the dorsal aortae
Aortic arches give rise to the great arteries of the neck and head
How do blood vessels develop?
Vasculogenesis and Angiogenesis
What does vasculogenesis mean?
Defined by the new formation of a primitive vascular network
What does angiogenesis mean?
Defined as the growth of new vessels from pre-existing blood vessels
What happens to the 1st and 2nd arches formed from aortic sac?
Disappear early
What does the 3rd aortic arch form?
Common carotid artery
What does the 4th right arch form?
Right subclavian artery
What does the left 4th arch form?
Aortic arch
What happens to the 5th arch?
Disapears
What does the 6th left arch form?
Left pulmonary artery and ductus arteriosus
What does the 6th right arch form?
Right pulmonary artery
What can cause an aortic arch abnormality?
Arise as result of persistence of aortic arches that either normally should regress or regression of arches that shouldn’t
Ex. right subclavian sometimes has abnormal origin on the left which may constrict trachea and oesophagus
What happens in a double aortic arch?
Occurs with non-regression of the right aortic arch forming a vascular ring around the trachea and oesophagus which usually causes difficulty in breathing and swallowing
Explain Patent Ductus Arteriosus (PDA)
Associated with rubella infection in early pregnancy
Causes failure of muscular wall to contract and causes resp. distress and lack of surfactant
Can lead to congestive heart failure in later life
What can PDA be associated with?
ASD, VSD and coarctation of the aorta
Explain coractation of the aorta
Congenital condition where aorta is narrow, usually where the ductus arteriosus inserts
Most common in aortic arch
Can be proximal to ductus arteriosus, preductal or postductal
What embryonic vessels change to adult vessels?
Vitelline vessels supply yolk sac - adult gut vessels
Umbilical vessels supply placenta - internal iliac
Cardinal vessels supply rest of body - SVC and IVC
When does the lymphatic system develop?
End of 6th week around main veins
Explain the development of the lymphatic system
6 primary lymph sacs develop at end of embryonic period
Lymphatic vessels join these later
How does the thoracic duct develop?
from 2 vessels anterior to the aorta
These become left and right embryonic thoracic ducts
Left gives rise to upper 3rd of adult thoracic duct and lower 2/3rds of adult duct are formed by right embryonic thoracic duct
What are the 3 types of foetal circulation?
Ductus venosus
Foramen ovale
Ductus arteriosus
Explain the function of the ductus venosus
Shunts blood in left umbilical into IVC which allows oxygenated blood from placenta to bypass the liver
Describe the function of the ductus arteriosus
Shunts blood from right ventricle and pulmonary arteries to aorta which allows the blood to bypass the lungs
What happens after birth to ductus venosus?
Ligamentum venosum of the the liver
What happens to the ductus arteriosus after birth?
Becomes the ligamentum arteriosum between left pulmonary artery and aorta
What happens to the umbilical arteries after birth?
Medial umbilical ligaments of anterior abdominal wall
