Right atrium

The right atrium , atrium dextrum, is located on the right side of the base of the heart, has the shape of an irregular cube.

In the cavity of the right atrium, the following walls are distinguished: the outer wall, which is facing to the right, the inner one directed to the left, which is common for the right and left atriums, as well as the upper, posterior and anterior ones. The lower wall is absent, here is the right atrioventricular opening. The thickness of the atrium walls reaches 2-3 mm.

The more expanded part of the right atrium, which is the site of the confluence of large venous trunks, is called the sinus of the hollow veins, sinus venarum cavarum. The narrowed part of the atrium to the front passes into the right ear, auricula dextra.

On the outer surface, both these parts of the auricle are separated by a border groove, the sulcus terminalis, an indistinctly sloping arcuate recess that begins under the inferior vena cava and ends in front of the superior vena cava.

The right ear, auricula dextra, looks like a flattened cone directed to the left toward the left, towards the pulmonary trunk. With its internal curved surface, the eye is attached to the bulb of the aorta. Outside, the upper and lower edges of the tab have slight irregularities.

Two right into the right atrium - upper and lower - hollow veins, coronary sinus and small own veins of the heart.

Upper hollow vein, v. Cava superior, opens on the border of the upper and anterior walls of the right atrium with the opening of the superior vena cava, ostium venae cavae superioris.

Lower hollow vein, v. Cava inferior, opens on the border of the upper and posterior walls of the right atrium with the opening of the inferior vena cava, ostium venae cavae inferioris.

On the anterior edge of the mouth of the inferior vena cava from the side of the atrium cavity there is a semilunular form of the inferior vena cava flap, valvula venae cavae inferioris, which goes to the oval fossa ovalis, on the atria septum. With this damper, the fetus sends blood from the inferior vena cava through the oval aperture into the cavity of the left atrium. The flapper often has one large outer and several small tendon threads.

Both hollow veins form an obtuse angle, with the distance between their mouths reaching 1.5-2.0 cm. Between the place of confluence of the upper and lower hollow veins, on the inner surface of the atrium, there is a small intervenous tubercle, tuberculum intervenosum.

The relief of the inner surface of the right atrium is heterogeneous. The inner (left) and posterior atrium walls are smooth. The outer (right) and front walls are uneven, since here the crural muscles appear in the atrium cavity in the form of ridges, mm. Pectinati. Distinguish between the upper and lower muscle tufts of these muscles. The upper bundle follows from the mouths of the hollow veins to the upper wall of the atrium, the lower one goes along the lower border of the right wall, upward from the coronal sulcus. Between the fascicles there are small muscle shafts, going up and down. The cranial muscles begin in the region of the border crest, the crista terminalis, which corresponds to the border groove on the outer surface of the atrium.

The inner surface of the right abalone is covered with crestal muscles that intersect in different directions, mm. Pectinati.

On a relatively smooth inner wall, that is, on the septum between the atria, there is an oval flat depression - the oval fossa, fossa ovalis, is an overgrown oval hole, foramen ovale, through which the cavities of the right and left auricles communicate in the embryonic period. The bottom of the oval fossa is very thin and in adult people quite often has a slit-shaped shape, the size of the pin-shaped hole is the remainder of the oval hole of the fetal heart and is well distinguishable from the left atrium.

The margin of the oval fossa, limbus fossae ovalis, formed by a small muscular roller, surrounds it in front and below; The medial end of the flap of the inferior vena cava is attached to the anterior margin.