Question

1. (1 pt) What's the difference between an open and closed circulatory system? How does blood return to the heart in open vs. closed circulatory systems? 2. (2 pts) Fish have a single circulation while terrestrialvertebrates have a double circulation. What's the difference between single and double circulation? b. Why do some animals need a double circulation? C. What are the two main circuits of a double circulation and what do they do? d. Whatis the third circuit and what does it do?

Answer 1

Answer 1:- In an open circulation system, the hemocoel (body cavity containing hemolymph) and the hemolymph (fluid flowing in this system) are responsible for the blood circulation to various organs and tissues of the body. This type of blood circulation system is commonly found in arthropods, snails, spiders.etc. The blood flow is comparatively slow and no gas transfer takes place. On comparison with a closed circulatory system, it is commonly found in invertebrates as well as vertebrates such as humans, cats, earthworms, etc. The circulation fluid is called as blood which carries gases such as oxygen and carbon dioxide. The heart is the main organs for pumping of the blood. The blood is carried to various body parts through blood capillaries and is returned to the heart through veins for re-oxygenation of the blood.

Answer 2a:- In a single circulation system that occurs in fish the blood flows once through the heart during one complete cycle (passage through the body). In case of double circulation, the blood flows twice through the heart during one complete cycle. Predominantly found in vertebrates such as birds and mammals.

2b:- Blood flows at a higher pressure in a double circulation system thus there is an increased supply of food and oxygen to the cell. Also, it helps in faster elimination of waste.

2c:- The two major circuits in a double circulation system are pulmonary circuit and systemic circuit. The pulmonary circuit is between the heart and the lungs i.e. it carried de-oxygenated blood to the lungs wherein gaseous exchange takes place and the blood gets re-oxygenated and systemic circuit is between the heart and other organs of the body i.e. transfer of oxygenated blood to different parts of the body.

2d:- The third circuit is the cerebral circuit that deals with the blood-brain barrier and transfer oxygenated blood to the brain and carried back de-oxygenated blood to the heart from the brain.