GENERAL HISTOLOGY

Detailed explanation-1: -Circulatory system is not found in Porifera, Cnidaria, Platyhelminthes, Nematodes and Echinoderms. An open circulatory system is found in arthropods, gastropods, bivalves and protochordates.

Detailed explanation-2: -As in other molluscs, the circulatory system of gastropods is open, with the fluid, or haemolymph, flowing through sinuses and bathing the tissues directly. The haemolymph typically contains haemocyanin, and is blue in colour.

Detailed explanation-3: -The circulatory system Mollusks possess an open circulatory system in which body fluid (hemolymph) is transported largely within sinuses devoid of distinct epithelial walls. The posteriodorsal heart enclosed in a pericardium typically consists of a ventricle and two posterior auricles.

Detailed explanation-4: -Bivalves have an ‘open’ circulatory system in which hemolymph is not always enclosed in vessels. Rather, circulatory fluid is carried by vessels from the heart to various parts of the body where it passes into open, spongy hemocoels (i.e., blood sinuses).

Detailed explanation-5: -The phyla in which the circulatory system is open and the body cavity is filled with blood are present in Mollusca and Arthropoda. Open circulatory systems work by pumping blood into a hemocoel. The species in the phylum Arthropoda have an open circulatory system.