Anatomy S2B3 - Cardiac Embryology
Describe the bending of the heart tube that occurs on day 23
- the cephalic portion bends ventrally, caudally and right - the caudal portion dorsally, cranially, and left - forms the cardiac loop, which is complete by day 28
Coronary arteries arise from these 3 sources
1. From angioblasts that migrate over the surface of the heart 2. From epicardial cells that undergo a transition to mesenchyme under the influence of the myocardium. 3. From neural crest cells that contribute smooth muscle cells to the proximal segments of the coronary arteries.
The heart tube consists of these 4 parts, from cranial to caudal
1. bulbus cordis 2. ventricle 3. atrium 4. sinus venosus
After the obliteration of certain vessels due to the shunting of blood from left to right during weeks 4-10, what remains of the left sinus horn?
1. oblique vein of the left atrium 2. coronary sinus
What circulatory structures close after birth (4)?
1. umbilical arteries/vein 2. ductus venosus 3. ductus arteriosus 4. foramen ovale
The superior part of the right venous valve disappears, but the inferior part forms these structures
1. valve of inferior vena cava 2. valve of the coronary sinus
The sinus horns receive blood from these 3 structures (which all eventually get obliterated)
1. vitelline vein 2. umbilical vein 3. common cardial vein
Which aortic arch is associated with the vagus nerve?
6th
Tetralogy of Fallot
Due to unequal division of the conus because of displacement of the conotruncal septum. This produces 4 alterations: i. Pulmonary infundibular stenosis ii. Large interventricular septal defect iii. Overriding aorta that arises directly above the septal defect iv. Hypertrophy of the right ventricular wall
Why do abnormalities of neural crest origin contribute to congenital malformations of the great vessels?
Neural crest cells contribute to the formation of both truncus and cordis swellings (cushions)
Coarctation of the aorta
The lumen distal to the left subclavian is narrowed. The constriction can be proximal (preductal) or distal (postductal) to the ductus arteriosus.
What becomes of the septum primum?
The upper part disappears; the remaining part becomes the valve of the foramen ovale.
Occurs when the conotruncal septum fails to follow the spiral course, and instead runs straight down. Because of this the aorta originates from the right ventricle and the pulmonary artery originates from the left ventricle. This is usually accompanied by an open ductus arteriosus.
Transposition of the Great Vessels
characterized by either the absence or the fusion of the tricuspid valves, resulting in obliteration of the right atrioventricular orifice
Tricuspid atresia
Most common congenital cardiac malformation
Ventricular septal defect involving the membranous portion of the septum
What vessels arise from the aortic arches: a) 1st b) 2nd c) 3rd d) right side of 4th e) left side of 4th f) right side of 6th g) left side of 6th
a) maxillary artery b) hyoid & stapedial arteries c) common carotid and first part of internal carotid; the external carotid branches from it d) proximal part of the right subclavian e) part of the arch of the aorta f) proximal part becomes the right pulmonary artery g) proximal part becomes the left pulmonary artery, distal part becomes the ductus arteriosus
What is formed from the different parts of the bulbus cordis: a) proximal part b) middle part: conus arteriosus c) middle part: conus cordis d) distal part (truncus arteriosis)
a) trabeculated part of the right ventricle b) incorporated into the right ventricle c) outflow tracts of both ventricles d) roots of the aorta and pulmonary trunk
a) vasculogenesis b) angiogenesis
a) vessels arise by the coalescence of angioblasts b) vessels arise by branching from existing vessels
Due to failure of the right subcardial vein to connect to the liver
absence of the IVC (blood from the lower body reaches the heart via the azygous vein)
The right superior and left inferior truncus swellings (cushions) fuse to form what structure?
aorticopulmonary septum (divides the truncus into an aortic channel and a pulmonary channel)
What is the typical abnormal origin of the right subclavian artery?
arises from aorta distal to left subclavian, then crosses behind esophagus to reach right limb
What does the right supracardinal vein become?
azygous
Veins that drain the body of the embryo
cardinal veins
Blood islands also appear in the mesoderm, they unite to form a horse-shoe shaped endothelial tube surrounded by myoblasts, forming what structure?
cardiogenic field
Cor triloculare biventriculare
complete absence of atrial septum
If present, where does a left superior vena cava drain?
coronary sinus (then right atrium)
When does the heart start beating?
day 22-23
Condition in which the right dorsal aorta persists, and the two arches form a vascular ring around the trachea and esophagus.
double aortic arch
Due to failure of the left sacrocardinal vein to lose its connection with the left subcardinal vein
double inferior vena cava
Due to failure of the left anterior cardinal vein and failure of the formation of the left brachiocephalic vein
double superior vena cava
Probe patency
failure foramen ovale to completely fuse to the septum secondum
With growth, the free edge of septum secundum begins to overlap the ostium secundum, but an opening remains. What is it called?
foramen ovale
What are semilunar valves formed from?
from tubercles on the truncus swellings (cushions) with contributions from neural crest cells
As the left sinus horn is reduced, blood from the left side of the liver is redirected to the right, causing an enlargement of the right vitelline vein. This forms the __________.
hepatocardiac part of the inferior vena cava (also forms the superior vena cava)
After birth, the proximal parts of the umbilical arteries persist as what arteries?
internal iliac & superior vesicle arteries
Ostium secundum defect
leaves a large opening between the atria - due to excessive resorption of septum primum or inadequate development of septum secundum
Due to the persistence of the left anterior cardinal vein and obliteration of the right common cardinal vein
left superior vena cava
What becomes of the foramen ovale?
obliterated at birth when the increased pressure in the left atrium pushes the septum primum against the septum secondum
The crista terminalis marks the dividing line between which structures?
original trabeculated part of the right atrium and its smooth walled part
Formed from the opening between lower rim of septum primum and endocardial cushion in atrioventricular canal
ostium (foramen) primum (later gets obliterated by growth of endocardial cushion)
Perforations formed in upper part of septum primum which then fuse; allows blood to flow from right atrium to left
ostium (foramen) secundum
Failure of fusion of the conotruncal ridges which is always accompanied by a defective interventricular septum. The undivided truncus receives blood from both side of the heart.
persistent truncus arteriosus
The smooth walled portion of the right atrium (sinus venarum) is derived from this structure
right horn of the sinus venosus
A sickle-shaped crest that grows from the roof of the atrium into the lumen at the end of the fourth week
septum primum
The sinuatrial orifice is guarded by the right and left and venous valves, which fuse dorsally, forming what structure?
septum spurium
What do the right common cardinal vein and proximal part of the right anterior cardinal become?
superior vena cava
Dextrocardia
the heart is on the right because the heart tube loops to the left instead of the right
Ectopia cordis
the heart lies on the surface of the chest due to failure of closure of the ventral body wall.
Valvular stenosis
the semilunar valves are fused for a variable distance, reducing the opening of the vessel
What space gets created when the dorsal mesocardium disappears?
transverse pericardial sinus
The primary interventricular foramen is formed from the junction of which 2 structures?
ventricle and bulbus cordis