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The transport of chylomicrons is into the lacteals mainly because they are too big to get into the capillaries and yet they later supply triglycerides in the extra hepatic tissue by traversing in the capillary bed. This seems utterly illogical and self contradicting. So something seems to have gone wrong in this line of thought.

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  • $\begingroup$ chylomicrons travel via the lacteals into the lymphatic vasculature that forms the cisterna chylii and thoracic duct...chylomicrons and other large molecules that are unable to pass into the fenestrated capillaries of the intestinal tract use this route into the thoracic duct, which ultimately drains lymph directly into the left subclavian vein - completely bypassing any first pass metabolic effects of the liver $\endgroup$ – Vance L Albaugh Mar 8 '16 at 20:23
  • $\begingroup$ But they use the capillaries later to deliver triglycerides to the tissues. So I mean to say, they are anyway able to get there (in the capillaries) so why not absorb into capillaries initially itself? $\endgroup$ – Polisetty Mar 8 '16 at 20:37
  • $\begingroup$ I have asked my self that as well - though the triglycerides and the particles that carry them (VLDL, chylomicrons) are huge... see this question for some related comments: biology.stackexchange.com/q/30883/16299 $\endgroup$ – Vance L Albaugh Mar 8 '16 at 20:40
  • $\begingroup$ also - note that the chylomicrons and VLDL particles do not traverse the capillaries - the lipases that hydrolyze the triglycerides are located within the capillary endothelium - so when free fatty acids are released they are able to traverse the endothelium and be taken up by the adipocyte or other cell on the other side of the capillary. $\endgroup$ – Vance L Albaugh Mar 9 '16 at 4:12
  • $\begingroup$ @vance hey! I get it all now. Chylomicron size ranges around 300nm but the capillary diameter is around 40um. So the diameter is very much bigger. So they can very well traverse the capillaries, though they keep getting smaller due to lipoprotein lipase. On some further thought it occurred to me that while absorption in the gut it has to travel BETWEEN CELLS and here it has to travel WITHIN the lumen. So that happens to make all the difference!correct me if I happen to be wrong :) $\endgroup$ – Polisetty Mar 9 '16 at 7:17

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