GENERAL HISTOLOGY

Detailed explanation-1: -Blood glands are present on fourth, fifth and sixth segments in annelids. Blood glands produce blood cells and hemoglobin which is dissolved in plasma. Annelids possess a closed circulatory system.

Detailed explanation-2: -Unlike all other mollusks, cephalopods have a closed circulatory system. This means that blood flows through a series of vessels to return to the heart, rather than bathing organs in the blood fluid as in open circulatory systems.

Detailed explanation-3: -Circulatory System Architecture As opposed to a closed system, arthropods– including insects, crustaceans, and most mollusks– have an ‘open’ circulatory system.

Detailed explanation-4: -Annelids have a closed circulatory system in which blood is pumped along by muscles in blood vessels (Fig. 3.48). Blood flows through the microscopic capillaries, picking up food molecules from the digestive tract and oxygen from the skin and transporting them to the cells of the body.