ROUNDWORMS - Ascaris lumbricoides

The specimen shows three adult worms; these are usually grey in colour, but have been discoloured during preservation. The adults range in length from 15 - 30cm, and from 0.3 to 0.5cm in diameter. The eggs are deposited in the soil, where they undergo a period of incubation. The infection is acquirted by ingestion of the fully embryonated ova. The larvae are hatched in small intestine, and penetrate the wall, reaching the lungs by way of venules, or lymphatics. They pass into the alveoli from the alveolar capillaries, and migrate up to the main bronchial tree and down the oesophagus with swallowed saliva. In the small intestine, they grow into adults of male or female sex. The most frequent complications are caused by the adult parasite producing intestinal obstructions.