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|quote = The mohel brings the baby’s organ into his mouth immediately after the [[excision ]] of the [[foreskin ]] and sucks blood from it vigorously. This action lowers the internal pressure in the tissues of the organ, in the blood vessels of the head of the organ and in the exposed ends of the arterioles that have just been cut. Thus, the difference between the pressure in the blood vessels in the base of the organ and the pressure in the blood vessels at its tip is increased. This requirement has deep religious significance as well as medical benefits....Immediately after incising or injuring an artery, the arterial walls contract and obstruct, or at least reduce, the flow of blood. Since the arterioles of the ''orlah'', or the foreskin, branch off from the dorsal arteries (the arteries of the upper side of the organ), cutting away the foreskin can result in a temporary obstruction in these dorsal arteries. This temporary obstruction, caused by arterial muscle contraction, continues to develop into a more enduring blockage as the stationary blood begins to clot. The tragic result can be severe hypoxia (deprivation of the supply of blood and oxygen) of the glans penis.28 If the arterial obstruction becomes more permanent, gangrene follows; the baby may lose his glans, and it may even become a life-threatening situation. Such cases have been known to occur. Only by immediately clearing the blockage can one prevent such clotting from happening. Performing ''metzitzah'' immediately after circumcision lowers the internal pressure within the tissues and blood vessels of the glans, thus raising the pressure gradient between the blood vessels at the base of the organ and the blood vessels at its distal end—the glans as well as the excised arterioles of the foreskin, which branch off of the dorsal arteries. This increase in pressure gradient (by a factor of four to six!) can resolve an acute temporary blockage and restore blood flow to the glans, thus significantly reducing both the danger of immediate, acute hypoxia and the danger of developing a permanent obstruction by means of coagulation. How do we know when a temporary blockage has successfully been averted? When the “blood in the further reaches [i.e., the proximal dorsal artery] is extracted,” as Rambam has stated.