Human Anatomy Vol 1

Tilbutories or Inlets of lhe Right Atrium

L Superior vena cava.

(^2) Inferior vena cava.
3 Coronary sinus.
4 Anterior cardiac veins.
5 Venae cordis minimi (thebesian veins).
6 Sometimes the right marginal vein.
Right Atilovenlriculor Orifice
Blood passes out of the right atrium through the right
atrioventricular or tricuspid orifice and goes to the right
ventricle. The tricuspid orifice is guarded by the
tricuspid valve which maintains unidirectional flow of
blood (Fig. 18.11).
lnlelnol Feolures
The interior of the right atrium can be broadly divided
into the following three parts.
$moofft FosferfcrFarfor$emus ff#r&,irn
1 Developmentally it is derived from the right horn of
the sinus venosus.
2 Most of the tributaries except the anterior cardiac
veins open into it.
a The superior oena cara opens at the upper end.
b The inferior z)ena cara opens at the lower end.
The opening is guarded by a rudimentary valve
of the inferior vena cava or eustachian aalue.Dtrring
embryonic life the valve guides the inferior vena
caval blood to the left atrium through theforamen
oaale.
c. The coronary sinus opens between the opening of
the inferior vena cava and the right atrioven-
tricular orifice. The opening is guarded by tl:re rsakte
of the coronary sinus or thebesian aalae.
PERICARDIUM AND HEART
d, The venae cordis minimi are numerous small veins
present in the walls of all the four chambers. They
open into the right atrium through small foramina.
3 The interutenous tubercle of Lower is a very small pro-
jection, scarcely visible, on the posterior wall of the
atrium just below the opening of the superior vena
cava, During embryonic life it directs the superior
caval blood to the right ventricle.
fheAurusfe

1. Developmentally it is derived from the primitive
   atrial chamber.
   2 It presents a series of transverse muscular ridges
   called musculi pectinati (Fig. 18.11).
   They arise from the crista terminalis and run for-
   wards and downwards towards the atrioventricular
   orifice, giving the appearance of the teeth of a comb.
   In the auricle, the muscles are interconnected to form
   a reticular network.

Jffifersfrisl $epfum

L Developmentally it is derived from tl:.e septum

primum and septum secundum.

2 It presents the fossa oaalis, a shallow saucer-shaped

depression, in the lower part. The fossa represents

the site of the embryonic septum primum.

3 T}ne annulus oaalis or limbus (Latin a border) fossa oaalis

is the prominent margin of the fossa ovalis. It

represents the lower free edge of the septum

secundum. It is distinct above and at the sides of the

fossa ovalis, but is deficient inferiorly. Its anterior

edge is continuous with the left end of the valve of

the inferior vena cava.

Superior vena cava

Right pulmonary artery

Rlght pulmonary veins

Limbus fossa ovalis

Crista terminalis

Fossa ovalis

Valve of inferior vena cava

Ascending aorta

Pulmonary trunk

Right auricle

Musculi pectinati

lnteratrial septum

Right atrioventricular

orifice and valve

Opening of coronary sinus

Fig. 18.11: lnterior of right atrium