Through which vessel do chylomicrons ultimately enter the bloodstream?

Through which vessel do chylomicrons ultimately enter the bloodstream?

• A. Portal vein
• B. Aorta
• C. Inferior vena cava
• D. Thoracic duct

Answer: (D)

Chylomicrons start their journey in the intestinal mucosa and are too large to enter blood capillaries, so they first enter the lymphatic system through lacteals in the villi. They travel up the lymphatic network to the cisterna chyli and then into the thoracic duct. The thoracic duct delivers its lymphatic contents into the bloodstream at the left venous angle, where the left subclavian and left internal jugular veins join, returning chylomicrons to the systemic circulation. This route explains why fats reach the blood after passing through lymph, not directly via the portal vein. The portal vein doesn’t carry chylomicrons; the aorta is an artery, and the inferior vena cava collects venous blood but after chylomicrons have entered the bloodstream through the thoracic duct.

Chylomicrons start their journey in the intestinal mucosa and are too large to enter blood capillaries, so they first enter the lymphatic system through lacteals in the villi. They travel up the lymphatic network to the cisterna chyli and then into the thoracic duct. The thoracic duct delivers its lymphatic contents into the bloodstream at the left venous angle, where the left subclavian and left internal jugular veins join, returning chylomicrons to the systemic circulation. This route explains why fats reach the blood after passing through lymph, not directly via the portal vein. The portal vein doesn’t carry chylomicrons; the aorta is an artery, and the inferior vena cava collects venous blood but after chylomicrons have entered the bloodstream through the thoracic duct.