Central lacteal
Also known as: lacteal, lacteals
The central lacteal is a blind-ended lymphatic capillary in the core of each intestinal villus. It takes up chylomicrons and other large particles that cannot enter blood capillaries.
Overview
The lacteal's endothelium is joined by discontinuous "button-like" junctions that leave flap-valve openings. Chylomicrons, which measure up to about a micrometre, can pass through these, whereas the continuous basement membrane around blood capillaries keeps them out. After a fatty meal the lymph in the lacteals becomes milky (chyle), which gives the vessels their name.
Lacteals drain into a lymphatic plexus in the submucosa. From there lymph runs through the mesentery and its mesenteric lymph nodes, the intestinal lymph trunk and the cisterna chyli, then up the thoracic duct to enter the blood at the left venous angle, the junction of the left internal jugular and subclavian veins. Absorbed long-chain fats therefore reach the systemic circulation, and adipose tissue and muscle, before they reach the liver. Rhythmic contraction of smooth-muscle strands in the villus core helps propel the chyle.
- Location
Centre of the lamina propria core of every small-intestinal villus.
Anatomy
- Histology
A single layer of oak-leaf-shaped lymphatic endothelial cells with button junctions and no continuous basement membrane, surrounded by smooth-muscle strands.
Function
- Absorbs dietary long-chain lipids as chylomicrons, along with fat-soluble vitamins.
- Returns interstitial fluid and protein from the villus.
- Carries antigens and immune cells to the mesenteric lymph nodes.
Clinical significance
Intestinal lymphangiectasia
Dilated, obstructed lacteals leak lymph into the gut lumen. The result is a protein-losing enteropathy with hypoalbuminaemia, oedema, lymphopenia and fat malabsorption.
Chylous ascites and chylothorax
Injury to or obstruction of the intestinal lymphatics or thoracic duct (from trauma, surgery or lymphoma) releases milky, triglyceride-rich chyle into the peritoneal or pleural cavity.
Test yourself
Dietary long-chain triglycerides leave the enterocyte mainly as:
- Free fatty acids bound to albumin in portal blood
- Chylomicrons entering the central lacteals
- Micelles entering villous capillaries
- VLDL secreted into the hepatic sinusoids
Answer: Chylomicrons entering the central lacteals
Inside the enterocyte, fatty acids and monoacylglycerol are re-esterified and packaged with apoB-48 into chylomicrons. These are too large for blood capillaries, so they enter the lacteals and reach the blood via the thoracic duct. Micelles never cross the epithelium; they only carry lipids to the brush border.
Compiled from standard anatomy and physiology references — see the Digestive System sources. For education only; not medical advice.