Question

Do chylomicrons from lymphatic circulation bypass the heart and into the bloodstream (before they can even reach the heart)?

Overview of NEFA and TAG metabolism in the fed state Fed ENSUILIN Arterial blood bed Dietary fat and Skeletal Muscle Oxidation to CO2+ Reesterification of NEFAS to form TAGs for storage Small Intestine NEFAS .Reestenification of NEFAs to form TAGs Muscle poproteinas IMTG Chylomicron synthesis and secretion Portal blood MCT Lymph TAGs) DLSLDLs De novo lipogenesis high carbohydrate diet GlycerolEsterification of NEFAs to form TAGs NEFASAdipose tissue VLDL synthesis and secretion Reesterification of NEFAs and storage of TAGs (TAGS)lipoprotein Chylomicrons VLDLs TAGS) VLDLS (TAGs) Arterial blood Chylomicron remnants TDLs/LOLS Venous blood Overview of NEFA and TAG metabolism in the fasted+ statpasted GLUCAGON Artenial blood EPINEPHR Capillary VLDL remnants (IDLs and LDLs) Ketone bodies Skeletal Muscle Uptake of NEFAs and Oxidation of NEFAs and NEFAS ketone bodies VLDLS (TAGSlipproteinketone bodies to NEFAsipase CO2 + H2O Ketone bodies Lipolysis of stored IMTG Liver Glycerol DLs and LOLsEsterification of NEFAs to form TAGS VLDL synthesis and secretion Synthesis of ketone bodies Adipose tissue Lipolysis of stored TAGs Release of NEFAs and NEFAs VenousVLDLS (TAGs) blood Ketone bodies VLDLS (TAGs) VLDLS (TAGs) Ketone bodies Arterial blood Heart NEFAS NEFAs Venous blood

Answer 1

Answer. Chylomicrons consists of triglyceride(TG) and apolipoproteins. Chylomicrons helps in transport of lipids absorbed from the small intestine to adipose tissue, cardiac and skeletal muscle tissues where there TG component is hydrolyzed by the activity of an enzyme Lipoprotein lipase. If the dietary content like TG, Fatty Acids(FA) and Monoglycerides(MG) are present in free form then they are transported through the hepatic portal vein which connects the lymphatic capillary bed network of villi of small intestine to the lymphatic capillary bed network of liver. It means that liver first encounter the MGs, TGs, FAs, and other xenobiotic agents(drugs and toxins). But if fatty acids are long chain then these are absorbed through the lymphatic gaps and enters into the lymphatic system and are transported to the circulatory blood vessels(thoracic vein) in the thoracic region and Futher that are transported to the liver and the other tissues where their hydrolysis takes place by the respective enzymes. So short chain fragments of chylomicrons can be transported directly to the liver except the long chain chylomicrons. Chylomicrons contains apolipoprotein which helps the chylomicron to reach at their destination. So first of all chylomicrons are synthesized in the small intestine and then are transferred by the enterocytes. Chylomicrons can't enter into the blood directly because they are large in their size and cannot pass through the walls of blood capillaries. The lymphatic capillaries/Lacteals of small intestine have bigger gaps between their cells which allows chylomicrons to enter into the lymphatic system.