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Related to marginal sinus: marginal sinuses
Etymology: L, margo + sinus, hollow
a sinus that may encircle the placenta. Also called placental sinus.
1. Considered together, the many dilated veins or venous "lakes" that collect blood in the intervillous space of the placenta; the marginal sinus drains into the uterine veins.
2. A dural sinus along the inside of the rim of the foramen magnum; it drains into the vertebral venous plexus.
3. A blood-filled sinus in the marginal zone of the spleen. In the passage from the red pulp to the white pulp, some arterial blood flows along (and percolates through) the endothelia-lined walls of the marginal sinus before entering the arterial capillary beds of the white pulp.
See also: sinus