- Position of right atrium
- External features
- Internal features
It is the upper right chamber of heart.
It forms the right border, upper border, the sternocostal surface & base of heart.
- The chamber is elongated vertically.
- Receives superior vena cava at upper end & inferior vena cava at lower end.
- Upper end is slightly prolonged to the left to form right auricle.
- A shallow vertical groove passes from SVC to IVC along right border – SULCUS TERMINALIS .
This is produced by an internal muscular ridge – CRISTA TERMINALIS
- Superior vena cava
- Inferior vena cava
- Coronary sinus
- Anterior cardiac veins
- Thebesian veins
- Sometimes, right marginal vein
The interior is divided into 3 parts –
- Smooth posterior part – sinus venarum
- Rough anterior part – pectinate part
- Interatrial septum.
- Sinus venarum –
- Developmentally derived from right horn of sinus venosus.
- Superior vena cava opens at upper end.
- Inferior vena cava opens at lower end.
The opening of IVC is guarded by a valve – Eustachian Valve.
- Coronary sinus opens between opening of inferior vena cava & right atrioventricular orifice.
The opening is guarded by Thebesian valve.
- Venae cordis minimae . These are small numerous veins that open into right atrium through small foramina.
- The intervenors tubercle of Loweris a small projection on the posterior wall below the opening of superior vena cava.
- Pectinate part –
- Developmentally it is derived from primitive atrial chamber.
- There are a series of transverse muscular ridges – Musculi pectinate.
They arise from crista terminalis & run downwards forwards towards the atrioventricular orifice giving the appearance of Honey comb.
- Interatrial septum –
- Developmentally it is derived from septum primum & septum secundum .
- It represents a swallow saucer shaped depression – fossa ovalis.
- The prominent margin of fossa ovalis –annulus ovalis or limbus fossa ovalis.
Soumya Khot – GMC Kolhapur.