Biology · MU Sofia

52. Phylum Nematoda: important evolutionary changes. Ascaris lumbricoides.

Covers the general features of the phylum Nematoda, or roundworms, including body plan, digestive and nervous system outline, health impact and a general life cycle. It then turns to Ascaris lumbricoides, describing ascariasis, its symptoms, transmission through contaminated food or water, morphology and a detailed stage-by-stage life cycle from egg to adult worm, with egg output, cycle duration and adult lifespan.

Inside: 2 sections · 2 labelled pictures · 12 flashcards · 2 min

Topic 52 of 64 in the MU Sofia syllabus for Biology (Dental Medicine, Year 1). The free AceMed note covers it in 2 sections, about 304 words (2 min of reading), with 12 flashcards.

In this note

  1. Introduction
  2. Ascaris Lumbricoides (Large Roundworm)

Introduction

Phylum Nematoda (Roundworms)

  • General Characteristics
  • Also known as roundworms.
  • Definitive Host: Humans.
  • Morphology
  • Roundworms feature a bilaterally symmetrical body.
  • They have a complete digestive system with openings at both ends.
  • The nervous system includes four peripheral nerves.
  • Health Impact
  • Roundworm infections can cause heavy infections in children, leading to malnutrition and stunted growth.
  • Symptoms in infected individuals can include fever, cough, and bloody sputum.
  • Lifecycle
  • Egg Release: Eggs are released in the feces, fertile with a single cell, and develop into embryos once in the soil.
  • Ingestion: Embryonated eggs are then ingested by humans.
  • Internal Development: Larvae are released into the intestine and travel through the bloodstream to the lungs.
  • Maturation and Reproduction: They continue to the trachea and pharynx, where adults form and reproduce, completing the cycle.

Ascaris Lumbricoides (Large Roundworm)

  • Disease
  • Causes ascariasis.
  • Symptoms
  • Infected individuals may experience abdominal pain, diarrhea, nausea, and weight loss.
  • Transmission
  • Transmission occurs through the ingestion of contaminated food or water.
  • Morphology
  • Large, cylindrical worms, measuring up to 35 cm in length.
  • Lifecycle
  • Egg Production: Adult worms reside in the small intestine, where a female may produce up to 200,000 eggs per day. These eggs are passed with the feces.
  • Embryonation: Fertile eggs embryonate and become infective after several weeks in the soil.
  • Ingestion and Hatching: The eggs are swallowed, and larvae hatch, invade the intestinal mucosa, and are carried via the bloodstream to the lungs.
  • Lung Maturation: The larvae mature in the lungs over 10 to 14 days, penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed.
  • Intestinal Development: Once back in the small intestine, they develop into adult worms.
  • Cycle Duration: It takes between 2 to 3 months from the ingestion of infective eggs to the onset of new egg production.
  • Lifespan: Adult worms can live between 1 to 2 years in the host.

Read the full note free

The whole note, all 2 sections, is free with an AceMed account, with its 12 flashcards. Premium adds flashcard recall, highlights and Ask AI.

Start freeAlready a member? Open the note