What is haemocoelome?

The haemocoelome, also called the open circulatory system, is a body cavity filled with blood or haemolymph. It is often found in invertebrates, particularly arthropods and mollusks. In the haemocoelomic system, the blood flows freely throughout the body cavity rather than being confined within closed vessels as in the closed circulatory system found in vertebrates and some invertebrates.

Here's a more detailed explanation:

1. Body Cavity:

The haemocoelome is the primary body cavity in haemocoelomic animals. It surrounds and bathes the internal organs, providing support and facilitating the transport of nutrients, oxygen, and waste products.

2. Blood or Haemolymph:

The fluid that fills the haemocoelome is called blood or haemolymph. It is a complex mixture composed of plasma, various types of blood cells, immune cells, and dissolved substances such as nutrients, hormones, and waste products.

3. Open Circulatory System:

In the haemocoelomic system, the circulatory system is open, meaning the blood flows directly into the body cavity rather than being confined within vessels. As the heart pumps, the haemolymph is expelled into the haemocoelome and circulates freely among the organs and tissues.

4. Heart and Pumping Mechanism:

Haemocoelomic animals typically have a simple heart or a series of pulsating vessels that function as pumps. These structures generate pressure to propel the haemolymph through the body cavity. In arthropods, the heart is usually a dorsal vessel located in the thorax or abdomen.

5. Exchange of Substances:

The free flow of haemolymph in the haemocoelome enables efficient exchange of substances. Nutrients, oxygen, and hormones can easily diffuse out of the haemolymph and into the surrounding tissues, while waste products are collected and transported back to the heart for elimination.

6. Lack of Vessels and Capillaries:

Unlike the closed circulatory system, the haemocoelomic system lacks a network of vessels and capillaries. Instead, the haemolymph flows freely through the open spaces of the body cavity.

The haemocoelome provides a flexible and efficient circulatory system for many invertebrates, allowing for the transport of vital substances and facilitating overall physiological functions.