Annelida: Circulation
Circulation
Characteristics of the circulatory system vary within the phylum. The blood usually contains hemoglobin, a red oxygen-carrying pigment; some annelids have a green oxygen-carrying pigment, and others have unpigmented blood. The circulatory system is usually closed, i.e., confined within well-developed blood vessels; in some polychaetes and leeches the circulatory system is partly open, with blood and coelomic fluid mixing directly in the sinuses of the body cavity. Blood flows toward the head through a contractile vessel above the gut and returns to the terminal region through vessels below the gut; it is distributed to each body compartment by lateral vessels. Some of the lateral vessels are contractile and serve as hearts, i.e., pumping organs for driving the blood.
Sections in this article:
- Introduction
- Leech Reproduction
- Leech Predation and Digestion
- Leech Anatomy
- Class Hirudinea
- Oligochaete Reproduction
- Oligochaete Circulation and Respiration
- Oligochaete Digestion
- Oligochaete Anatomy
- Class Oligochaeta
- Archiannelida and Myzostomaria
- Polychaete Reproduction
- Polychaete Anatomy
- Sedentary Polychaetes
- Errant Polychaetes
- Class Polychaeta
- Reproduction
- The Nervous System
- Respiration
- Circulation
- Digestion
- The Body Wall
- Segmented Bodies
- Bibliography
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.
See more Encyclopedia articles on: Zoology: Invertebrates
