Different circulatory systems

Question

Hi!

I have a question.

What are the pros and cons of:

1. An open circulatory system
2. A closed circulatory system
3. A three-chambered heart (for example the one in reptiles)
4. A four-chambered heart (for example the one in humans)?

PS: This is not a homework question. I have read about the different circulatory systems, but I wonder if anyone could explain the pros and cons for study purposes.

Answer 1

A main purpose of a circulatory system is to distribute oxygen (required by organisms for metabolism) and nutrients from the environment, and to remove metabolic and other wastes. Any cell which is mart of a multicellular organism requires access to the environment via its cell wall or membrane. A single celled organism has full access to the environment. An open system has no specialized tissue which pumps the fluid around. Fluid moves as the organism moves in its environment, more of a sloshing around than pumping. These organisms can and do possess oxygen transport molecules, and each individual cell can exchange nutrients and waste with the fluid. This is seen in arthropods.

All vertebrates and more evolved species possess a closed system, with a dedicated pump or heart. A fish, for instance, has a single circulatory 'circuit' with a two chambered heart. Blood is pumped through the gills and throughout the body in a single circuit.

Amphibians, like a frog, have a three chambered heart with two circuits, one through the lungs and a second through the body. This is less efficient in oxygenating blood, as low oxygen blood returning from the body is mixed with oxygenated blood from the lungs.

Mammals have a 4 chambered heart, with two circulation 'circuits', one which receives blood from the body and pumps it through the lungs to pick up oxygen, and a second 'circuit' which pumps the newly oxygenated blood back to the body tissues. This is the most evolved, and most efficient method of distributing oxygen.

Closed systems, like mammals, provide a separate fluid, blood, which is solely responsible for transporting oxygen, nutrients, and metabolic waste to and from the cellular tissue environment, which is surrounded by extra-cellular fluid, which is held separate from the circulating fluid (blood).