MRCS PART A · APPLIED BASIC SCIENCES
Intestinal lymphatics: packaging, transport & nodes
Two selected basic-science objectives and four linked SBAs. Trace the material and its compartment before choosing a route. These physiological models do not establish a patient's diagnosis, nutritional prescription or operative plan.
2 topics · 4 original SBAs
1 · Digestion is not packaging
Your task: Separate luminal micelles, enterocyte assembly and the first lymphatic recipient.
Are a micelle and a chylomicron the same particle?
No. A bile-salt micelle helps present lipid digestion products at the intestinal surface. Enterocytes take up those products and assemble triglyceride-rich chylomicrons; a micelle is not simply renamed after crossing the brush border.
Which compartment changes the answer?
Micellar delivery is luminal. Chylomicron assembly is intracellular; export occurs from the enterocyte's basolateral side.
Does uptake alone prove successful export?
No. Digestion, uptake, assembly and onward movement are distinguishable stages.
Where does a newly exported chylomicron enter lymph?
After crossing the villus interstitium, it enters a lacteal: a specialised lymphatic capillary. The lacteal transports the particle; it is not the enterocyte that assembled it.
Is the lacteal a blood capillary?
No. Nearby blood capillaries and the lacteal are different channels. Identify the particle, not just the villus.
Does all absorbed food therefore enter lymph first?
No. Newly formed chylomicrons travel through intestinal lymph to systemic blood rather than directly through the hepatic portal vein. Absorbed glucose follows intestinal blood and portal delivery to the liver. Do not convert a particle-specific route into a rule for every nutrient.
Does bypassing initial portal delivery mean the liver never handles its lipid?
No. Initial transport and later metabolism are different questions. Chylomicron remnants can subsequently be taken up by the liver.
2 · Follow the vessel through a node
Your task: Use node-relative direction and distinguish transport from immune surveillance.
What follows the lacteal?
Intestinal collecting lymphatics convey lymph through mesenteric nodes and onward towards larger lymphatic channels. This is not the same as venous drainage into the portal system.
Must every person have an identical visible collecting trunk?
No. A simplified route teaches compartments and direction, not an individual's complete anatomy.
What do afferent and efferent mean here?
Relative to the named lymph node, afferent vessels bring lymph in and efferent vessels carry it away. These are not labels for oxygen content or nutrient concentration.
Can one connecting vessel be described both ways?
Yes: efferent from the upstream node and afferent to the downstream node. Always state the reference node.
Is a node's blood vessel automatically its efferent lymphatic?
No. Blood supply and lymph flow are distinct routes.
Is intestinal lymph only a stream of fat?
No. It also carries fluid and immune material. Nodes support immune surveillance and lymph filtration; they do not replace enterocytes as the site of chylomicron assembly.
Does passing through a node prove disease or remove all lipid?
Neither. Normal transport is not evidence of malignancy or infection. Filtration does not mean that every carried substance is completely stripped from lymph.