In aoic dissection blood enters in -

Ans. is `b' i.e., MediaAoic dissection o Aoic dissection is a catastrophic illness characterized by dissection of blood between and along the laminar planes of aoic media.o Blood enters inside the aerial wall (in the media layer) and leads to formation of blood filled channels within the aoic wall, which often ruptures outward causing massive hemmorrhage.o The most frequent preexisting histologically detectable lesion is cystic medial degeneration.o In aoic dissection, there is an intimial tear through which the blood enters into the media.o Usually, the tear is within 10 Cms of aoic valve.o The dissecting hematoma spreads characteristically along the laminar planes of the aoa, usually between the middle and outer third.Some times, blood reruptures into the lumen distally, i.e. there is a second tear distally. So that a complete new vascular channel is formed inside the media of aoic wall --> Blood enters from proximal tear into the media and comes out into the lumen from distal tear.o This is called double - barrel aoa with a false-channel in the media.Later on this false channel becomes endothelized --> chronic dissection.