2. FORMATION OF ATRIA
It involves following process:-
1. Formation of septum spurium
2. Septation of atrio- ventricular canal
1. Formation of septum spurium:-
3. Contd….
2. Septation of atrio- ventricular
canal:-
Atrio-ventricular canal divides
into right & left halves as
follows:-
- Two thickening, the atrio-
ventricular cushion appear on
its dorsal & ventral walls.
- They grow towards each other
& fuse . The fused cushions
form the septum intermedium.
5. Development of Right Atrium
• Right half of primitive atrium:-
- form the main part of musculi pectinati & right auricle.
• Enlarge right horn of sinus venosus:-
- incorporated into right atrium forms the posterior smooth part
(sinus venarum).
- superior venacava & inferior venacava open in this part.
• Right half of atrio-ventricular canal:-
- also called tricuspid valve , which allow flow of blood from
right atrium to right ventricle.
- right A-V canal is guarded by tricuspid valve.
• Interatrial septum:-
- separates right atrium from the left atrium.
7. Fate of right and left venous valve
Rt venous valve:-
crista terminalis,
valve of IVC& coronary
sinus
8. Foramen Ovale
• The oval foramen closes at birth
• Anatomical closure is due to adhesion of the
septum primum (the valve of the foramen ovale)
to the left margin of the septum secundum..
• The septum primum forms the floor of the fossa
ovalis.
• The inferior edge of the septum secundum
forms a rounded fold, the limbus fossae ovalis
(anulus ovalis).
9.
10. Development of Left Atrium
• Left half of primitive atrium
- forms the main parts of musculi pectinati & left auricle.
• Absorbed proximal part of pulmonary veins
- forms the smooth part.
- four pulmonary veins bringing oxygenated blood from lung
and drain into left atrium.
• Left half of atrio-ventricular canal
- also called mitral valve (bicuspid valve), which allow flow of
blood from left atrium to left ventricle.
- left A-V canal is guarded by mitral valve which are formed by
proliferation of connective tissue under endocardium of
left A-V canal.
12. DEVELOPMENT OF VENTRICLES
• Fate of bulbus cordis:-
Bulbus cordis is divisible into
3 parts:-
1. Truncus arteriosus.
2. Conus cordis.
3. proximal parts of
bulbus cordis.
13. Contd….
• Truncus Arterious:-
A spiral septum appears within truncus arterious and
subdivided it into ascending aorta & pulmonary trunk.
it is formed by the fusion of right superior & left
inferior truncus swelling or cushion.
14. Formation of interventricular septum
• The bulboventricular cavity
formed after the conus cordis
& proximal part of bulbus
cordis have merged into
primitive ventricle has to be
subdivided into right & left
halves of ventricle in such
way that:-
a. Each halves communicate
with the corresponding
atrium
b. Right ventricles open into
pulmonary trunk & left
ventricle into the aorta.
15.
16. Valves of the Heart
Function :-The valves of the heart maintain unidirectional flow
of blood & prevent regurgitation in the opposite direction.
• There are 2 pair of valves in the heart:-
1. A pair of atrioventricular valve
- mitral(bicuspid) & tricuspid valves are proliferation of
connective tissue under endocardium of the right & left
atrioventricular canals.
2. A pair of semilunar valve
- aortic & pulmonary valves derived from endocardial cushion
that are formed at the junction of the truncus arteriosus &
conus cordis.
18. CONGENTIAL MALFORMATIONS
• ACARDIA
– Absence of heart
• Only occurs in conjoined monozygotic twins
• 1:35,000
• ECTOPIC CORDIS
– Heart is located through a sternal fissure into:
• Into the neck
• Down through a diaphragmatic hernia into a
exomphalocoele
• Protruding outside chest
–Dextra thoracic ectopia
»Limited life expectancy
20. CONGENITAL MALFORMATIONS
• DEXTRACARDIA
– Heart is located in right hemithorax
– Most cases associated with situs inversus
• Heart, great vessels, other thoracic & abdominal
organs may present a mirror image of the norm.
• 1:10,000
– Known to occur with other anomolies
• Duodenal atresia
• Agenesis of spleen
• Spina bifida
– Isolated cases rare (1:900,000)
21. NORMAL : Loop to the RIGHT: LEVOCARDIA
ABNORMAL: Loop to the LEFT: DEXTROCARDIA
22. Defective formation of septa
• Interatrial septal defect:-
3 types:- A. septum primum defect.
B. septum secundum defect
C. patent foramen ovale.
• Interventricular septal defect.
25. • Taussing- Bing syndrome:-
Aorta arises from right ventricle; & pulmonary
trunk overrides both the right &left ventricle, there
being an interventricular septal defect.
• Eisenmergers complex:-
is a combination of pulmonary hypertension due to
- hypoplasia of pulmonary complex
- dilatation of pulmonary trunk,
- hypertrophy of right ventricle.
when associated ASD,VSD,& PDA the condition is
termed Eisenmergers complex.
29. Conducting system of Heart
Formation
1. SA node :-
it is formed from pacemaker which occupies
following position.
- initially lies in the caudal part of left tube .
- after fusion of two tube, it lies in the sinus venosus,
- when the sinus venosus incorporated into right atrium, it
comes to lie near the opening of SVC.
2. AV node & bundle of His:-
are formed from 2 source :-
I. left wall of sinus venosus
II. Atrioventricular canal.
- after incorporation of sinus venosus into the right
atrium, the final position taken by these cells is at the
base of interatrial septum.
30. THE DEFINITIVE RIGHT ATRIUM
**NOTE: In 25% of normal population, the
foramen ovale remains ‘probe patent’.
