= Aortic root
The \b[aortic root] is the proximal <aorta> associated with the <aortic valve>, extending from the basal leaflet reference toward the <sinotubular junction>. It includes the leaflet-bearing region and the bulges called <aortic sinuses>, and gives origin to the <coronary arteries>. It connects the <left ventricular outflow tract> to the tubular <ascending aorta>.<Surgical anatomy of the aortic valve and root—implications for valve repair by Ruggero De Paulis and Andrea Salica>[General considerations; Figures 1–2]{ref}
The boundaries answer different anatomical questions. The <virtual basal ring> is constructed from basal leaflet attachment landmarks, whereas the <sinotubular junction> marks the distal transition. The three-dimensional leaflet attachments are crown-shaped, so the word <aortic annulus> requires a stated convention. The anatomical account by <Robert H. Anderson> emphasizes this terminology problem.<The surgical anatomy of the aortic root by Robert H. Anderson>[Abstract, differing annulus and ventriculo-aortic-junction definitions]{ref}
An original volume balance shows why the <aortic root> is more than a named length of <Pipe>. Let $Q_{\rm in}$ enter through the <aortic valve>, $Q_{\rm out}$ leave toward the <ascending aorta>, and $Q_{\rm cor}$ denote total outflow into the <coronary arteries>. For <blood> treated as incompressible,
$$
\frac{dV_{\rm root}}{dt}=Q_{\rm in}-Q_{\rm out}-Q_{\rm cor}.
$$
Stipulated mean rates over 0.1 s of 100, 80 and 5 mL/s give a 1.5 mL increase in stored volume. Over a repeating <cardiac cycle>, zero net accumulation instead requires equal integrated inflow and total outflow. Instantaneous equality is unnecessary if the region changes volume.
Measurement likewise requires a named level. The primary anatomical exposition illustrates separate basal, sinus and <sinotubular junction> diameters in an <echocardiography> view.<Surgical anatomy of the aortic valve and root—implications for valve repair by Ruggero De Paulis and Andrea Salica>[Figure 1 and its legend]{ref} Reporting only an unspecified root diameter discards that spatial information. The level, direction and phase of the <cardiac cycle> connect a number to a reproducible part of the <aortic root>.
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