Why marine protozoa do not have contractile vacuole?

An organ system consists of a group of organs that performs specific functions necessary for the survival of an organism. humans have eleven different organ systems: integumentary, skeletal, muscular, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive. discuss the function of neurons, the brain and the spinal cord within the human nervous system while explaining the interrelationship of each organ.

Dna replication or repair occurs in a cell in all of thw following situations except when

Vessels draining the myocardium of the heart, open primarily ,into which chamber?