1. Closed Circulatory System: Unlike flatworms, which have an open circulatory system, segmented worms have a closed circulatory system. This means that their blood is enclosed within vessels, including arteries, capillaries, and veins. This arrangement allows for efficient and regulated circulation of blood throughout the body.
2. Blood Composition: The blood of segmented worms contains various components such as plasma, red blood cells, and white blood cells. Red blood cells, also known as erythocytes, contain the respiratory pigment hemoglobin, which helps in oxygen transport.
3. Blood Vessels: The circulatory system of segmented worms consists of blood vessels with well-defined structures. Arteries carry oxygenated blood from the heart to various organs and tissues, while veins transport deoxygenated blood back to the heart. Capillaries, the smallest blood vessels, facilitate the exchange of oxygen and carbon dioxide between the blood and the body tissues.
4. Hearts and Blood Flow: Segmented worms possess specialized structures called hearts or pulsating vessels. These muscular structures serve as pumps that propel the blood through the blood vessels. Blood flow is typically unidirectional, from the heart through the arteries, capillaries, and veins before returning to the heart.
5. Dorsal Blood Vessel: A prominent feature of the circulatory system in segmented worms is the presence of a dorsal blood vessel. This large blood vessel runs along the dorsal side of the worm and receives blood from the smaller vessels. The dorsal blood vessel transports oxygenated blood to various organs and tissues.
6. Paired Nephridia: Annelids have paired segmental structures called nephridia, which function in excretion. Each nephridium is associated with a blood vessel, allowing for the exchange of substances between the circulatory system and the excretory system.
7. Importance in Gas Exchange: The circulatory system in segmented worms plays a crucial role in gas exchange. As the blood flows through the capillaries, oxygen diffuses from the blood into the surrounding tissues, while carbon dioxide diffuses from the tissues into the blood. This efficient gas exchange system ensures an adequate supply of oxygen to the cells and elimination of waste gases.
Overall, the circulatory system of segmented worms exhibits advanced features, including a closed circulatory system, hemoglobin-containing red blood cells, blood vessels, hearts, and a dorsal blood vessel. These adaptations enable efficient transport of oxygen and nutrients, facilitating the growth, activity, and overall survival of segmented worms in their respective environments.