The<unk>  is a section of the ascending aorta that is normally dilated (enlarged or widened) just above the<unk>  valve.
There are generally three<unk> es, the left, the right and the posterior.
The left<unk>  gives rise to the left coronary artery.
The right<unk>  gives rise to the right coronary artery.
Usually, no vessels arise from the posterior<unk> , which is therefore known as the non-coronary sinus.
Shown below is a drawing depicting the<unk>  anatomy.  Note that the<unk>  has three cusps: the left coronary cusp, the right coronary cusp and the non coronary cusp.
Aortic sinus
Coronary sinus
Coronary sulcus
Thoracic aorta
Pulmonary valve
Atrioventricular canal
Interventricular septum
Tricuspid valve