The lipoproteins must deliver fatty nutrients to the tissues
that need them, and then be removed from circulation (by the
liver) when spent. The cycle is continual, with new nutrients
entering into circulation by way of the liver, the skin, and
many other tissues, on a continual basis. Major inputs come from
the diet, and the ultimate disposal of broken-down fatty
nutrients occurs with excretion into the bile. Because the flow
of nutrients is continuous, the phases outlined below are broken
into arbitrary points only for the sake of clarity. The small
intestinal cells manufacture the very first lipoprotein
particles that newly ingested fats will circulate within, called
chylomicrons. Chylomicrons enter the bloodstream via the
thoracic duct, which bypasses the liver to dump directly into
the left subclavian vein. Sometimes the term nascent chylomicron
is used to describe the first lipoproteins particle manufactured
by the intestinal cells. When nascent chylomicrons circulate
through the bloodstream they encoun