Circulatory System

The purpose of the circulatory system is to carry blood throughout the body, transporting gasses and nutrients to the organs that need it. It is also needed to carry gas waste so the respiratory system can get rid of it. There are different circulatory systems, such as open and closed ones, as we will see below.

Worm

The circulatory system of an earthworm is very similar to other mammals. Earthworms have a closed circulatory system. This means that their blood flows through blood vessels. Not to mention, their blood vessels help process oxygen from breathing through their skin. Oxygen is drawn in by the dorsal blood vessel. It travels to the five hearts it has, called aortic arches. Once there, it travels to the ventral blood vessel, and the process repeats.

Crayfish
The circulatory system of a crayfish is different from the other organisms we studied in this unit. They have an open circulatory system. In an open circulatory system, there are no veins or arteries, but instead, blood-like fluid is pumped from vessels to cavities in the body. If the blood has no oxygen, then it go to the lungs to retrieve some oxygen and returns to the heart to keep it running. If the blood is oxygenated, then the blood leaves the heart through the sinus arteriole opening and travels through the body to find a cell in need of oxygen and returns to the heart to repeat this process.

Frog

The circulatory system of the frog is a closed circulatory system. It consists of a single ventricle and two atria. The single ventricle is not splint into two, but it is apart enough so that the blood will not mix. This is a disadvantage of the evolutionary system. The blood may get caught and huge issues will occur in the frog's circulatory system. The left atrium receives oxygen-laden blood and enters the ventricle. The oxygen-poor blood at the bottom of the ventricle prevents the oxygen-laden blood from sinking to the bottom. After, the oxygen-poor blood flows into the vessels leading the the lungs and the oxygen-laden blood is forced into arteries.

Rat
The circulatory system of the rat is very similar to a human's circulatory system. It's heart is divided into 4 sections, 2 on the top and 2 on the bottom: the left atrium, the right atrium, the left ventricle, and the right ventricle. Oxygen-poor blood is carried by veins that terminate into 3 main veins: the right superior vena cava, left superior vena cava, and inferior vena cava. Oxygen-poor blood is brought to the heart by the inferior vena cava. They enter the right atrium of the heart and from the right atrium, the blood is pumped into the right ventricle. The blood circulates through the rat's body, just like a human's. It's 4-chambered heart is an advantage because the oxygen-laden blood and oxygen-poor blood are not in risk of mixing in that type of heart.