The incomplete movement relates to systems circulation of blood in the arterial blood from the lungs is oxygenated mixed with venous blood coming from other parts of the body.
This mixing is possible in circulatory systems where the heart has only one ventricle, a place where venous and arterial blood mix.
Scheme of incomplete circulation in amphibians
The mixture is then pumped through the heart into the tissues and lungs. This type of circulatory system is known as an incomplete circulatory system.
In contrast, complete circulation is that which occurs in complete circulatory systems, characterized by the fact that arterial and venous blood never intersect. An example of complete circulatory systems is the circulatory system of fish.
Incomplete circulation is also part of closed circulatory systems. In closed circulatory systems, blood circulates exclusively within blood vessels.
In contrast, in open circulatory systems, blood is transported by blood vessels and is also irrigated through cavities into tissues.
Incomplete circulation then occurs in incomplete closed circulatory systems. Incomplete closed circulatory systems are characteristic of some fish, reptiles, and amphibians.
Incomplete circulation in reptiles and amphibians
Both reptiles and amphibians have an incomplete circulatory system with three chambers, two atria and a ventricle where blood mixes.
Reptiles can have a small separation that tries to simulate two separate ventricles by making the blood mix less than that found in amphibians.
Among reptiles, crocodiles have a heart with 4 well separated chambers, which is why they are classified as reptiles with complete blood circulation.
Many reptiles and amphibians are ectothermic animals, that is, they require external sources of heat to regulate their body temperature.
These animals are commonly known as cold-blooded animals and use incomplete circulation to help regulate their temperature.
According to studies, the specialized morphology of the heart of cold-blooded animals allows for little energy flow and fewer losses to the environment, which helps maintain temperature within the animal.
Because of the important function of thermal regulation that the incomplete circulatory system seems to fulfill in cold-blooded animals, some authors suggest that the incomplete circulatory system is a specialized system rather than a primitive system.
Incomplete circulation in humans
In the developmental stages of the human fetus, arterial blood and venous blood come to mix. It is then considered that in these stages the human being has an incomplete circulation.
This mixing of blood in the fetus occurs in two points. One is an opening between the arteries of the heart, known as the foramen ovale.
The other is a small blood vessel that connects the aorta artery with the pulmonary artery and is called the ductus arteriosus.
After birth, both mixing points are known to close. The rest of his life, the human being has a closed and complete circulatory system.
References
- Boundless. (2016). Types of Circulatory Systems in Animals. Boundless Biology Boundless, May 26 Accessed August 14, 2017. Source: boundless.com
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