1. The right atrium receives deoxygenated blood from the superior vena cava, inferior vena cava, and coronary sinus. It has a smooth posterior wall called the sinus venarum and a rough anterior wall. 2. The interatrial septum separates the right and left atria. It contains the fossa ovalis, limbus fossa ovalis, and openings for the coronary sinus and venae cordis minimae. 3. The interior of the left atrium is mostly smooth walled and receives the four pulmonary veins. Both atria pump blood into the ventricles through the atrioventricular valves.

1. INTERIOR OF HEART
.

4. RIGHT ATRIUM

6. RELATIONS

7. Right Atrium
• External features:
1.Right Auricle
2.Sulcus terminalis

8. SULCUS TERMINALIS

10. Interior Of Right Atrium
1.Smooth Posterior Part (Sinus
Venarum):
• Development: derived from right horn of sinus venosus
• Tributaries: → SVC opens at the upper end
→ IVC opens at the lower end
→Coronary Sinus……Valve of coronary sinus
→Venae cordis minimi
• Intervenous Tubercle of lower: →directs superior vena caval
blood 2 right atrium during embryonic life….

11. INTERIOR OF RIGHT ATRIUM

13. SINUS VENARUM
• occupies posterior wall and
posterior part of right wall of
atrium.
FEATURES
1. opening of svc
2. opening of ivc
3. opening of coronary sinus
4. foramina venarum minimarum
5. intervenous tubercle

15. SVC OPENING
• upper & posterior part of
atrium.
• directed downwards &
forwards.
• conveys blood from upper
parts of body.
• not guarded by valve

17. IVC OPENING
• lower & posterior part of
atrium close to septum.
• conveys blood from lower
part of body.
• opening guarded by a
rudimentary semilunar
valve [eustachian valve] -
formed by duplication of
endocardium containing a
few muscle fibres.

18. CORONARY SINUS OPENING
• Situated between opening of ivc
& right atrioventricular orifice in
lowerpart of interatrial septum.
• Guarded by incomplete semilunar
valve at its lower margin-
THEBESIAN VALVE.
• Av node lies just above the
opening of coronary sinus.

19. FORAMINA VENARUM MINIMARUM
• minute openings of venae
cordis minimi.
• more numerous in septal
wall.
• anterior cardiac veins &
sometimes right marginal
vein open in the atrium
proper through foramina
venarum.

21. INTERVENOUS TUBERCLE
• small conical muscular projection immediately
below opening of svc.
• scarcely visible in human.
• probably regulates the blood flow of svc.

23. ATRIUM PROPER
• LIES IN FRONT OF CRISTA TERMINALIS.

26. 2.Rough anterior Part:
• Development:→ derived from primitive atrial
chamber
→ Musculi Pectinati

27. CRISTA
TERMINALIS

28. MUSCULI PECTINATI

30. 3.Interatrial Septum:
• Development: →derived from Septum primum and
septum secundum
• Fossa ovalis →represents the site of embryonic
septum primum
• Annulus ovalis (Limbus fossa ovalis) →represents
the lower free edge of septum secundum

31. RT.SIDE OF INTERATRIAL SEPTUM
• FOSSA OVALIS
• LIMBUS FOSSA OVALIS
• TRIANGLE OF KOCH
[Triangular area bounded
in front by base of septal
leaflet of tricuspid
valve,behind by antero-
median margin of opening
of coronary sinus,above by
tendon of todaro-av node
lodges in the triangle]
• TORUS AORTICUS

33. TORUS AORTICUS
Elevation caused by bulging of right posterior aortic sinus
in antero-superior part of septum.

34. TRICUSPID VALVE
• Atrium proper
communicates with rt.
Ventricle through rt av.
Orifice.
• Opening – oval in
shape.Permits tips of
three fingers.
• Guarded by tricuspid
valve.
• Area of rt.Atrium - known
as vestibule of tricuspid
valve.

37. LEFT ATRIUM
• Volume - smaller than
right atrium.
• Situated behind & to
the left side of right
atrium.
• Forms 2/3rd of base of
heart.

40. LEFT AURICLE

42. INTERIOR OF LEFT ATRIUM
• Most of the wall –
smooth.
• Left auricle -network of
musculi pectinati is
seen.
• Posterior wall-receives
openings of 4
pulmonary veins.

44. CLINICAL IMPORTANCE
• POTENTIAL SITE FOR FORMATION OF
THROMBI.
• IN SURGICAL AMPUTATION OF LEFT AURICLE
DURING MITRAL VALVOTOMY OPERATION,
CIRCUMFLEX BRANCH OF LEFT CORONARY
ARTERY MAY BE INJURED.

45. CONGENITAL ANOMALIES
ATRIAL SEPTAL DEFECTS
• Probe patency of foramen
ovale.
• Persistent ostium
secundum.
• Persistent ostium
primum.
• Biventricular mono-atrial
heart.
• Pre-natal closure of
foramen ovale.

46. ASD

47. RIGHT VENTRICLE
• Generel Features:
1.Interior has 2 parts
2.Interior has 2 orifices
3.Inflowing part has 3 types of muscular ridges
→Ridges
→Bridges
→Pillars(papillary muscles)

53. TRICUSPID VALVE COMPLEX

55. PULMONARY VALVE

57. LEFT VENTRICLE

61. MITRAL VALVE

62. AORTIC VALVE COMPLEX

68. INTERVENTRICULAR SEPTUM

70. TETRALOGY OF FALLOT

71. THANK YOU

75. FEATURES
RIGHT SIDE
1. FOSSA OVALIS
2. LIMBUS FOSSA OVALIS
3. FORAMINA VENARUM
MINIMARUM
4. ATRIO VENTRICULAR
NODE[AV NODE].

76. FOSSA OVALIS
• Oval depression above
& to left of opening of
ivc.
• Floor is thin & formed
by septum primum.