What is the Difference between Open and Closed Circulatory Systems?

Human body is a complex mechanism that is composed of numerous systems that are working as one. Some of the systems in the body are cardiovascular system, integumentary system, gastrointestinal system, and circulatory system. This article is solely discussing the circulatory system, the two types of circulatory system which are open and close circulatory system, and what is the difference between open and closed circulatory systems?

Humans and animals have circulatory system. This system distributes blood and lymph in the different parts of the body. Basically, there are two types of fluid that make up the circulatory system and these are the blood and the lymph. The blood, heart, and blood vessels form the cardiovascular system while the lymph, lymph nodes, and lymph vessels form the lymphatic system.

The circulatory system is seen by some as a blood distribution network which is composed of the cardiovascular system, which distributes blood and the lymphatic system, which distributes lymph. Humans and other vertebrates have closed circulatory system while some invertebrates have open circulatory system. On the other note, there are primitive animals which do not have circulatory system at all. Examples of animals that do not have a circulatory system are phyla and flatworms.

Functions of the Circulatory System

The circulatory system is made up of the heart, blood and networks of blood vessels. The heart pumps out the blood into the blood vessels wherein these blood vessels are connected into the different body organs. The blood carries with it oxygen, nutrients (amino acids, electrolytes, and lymph), hormones, gases, etc. that the cells of the body need in order to function. The oxygen and the nutrients in the blood are then exchanged with carbon dioxide and metabolic waste products. These waste products are eliminated out the body in a form of urine, stool, breath, and sweat.

The blood also helps maintain and promote stronger immune system by simply transporting antibodies and nutrients throughout the body. Without the circulatory system, the body could not attain homeostasis and maintain life.

As what is stated earlier, the circulatory system can be classified as open or close system. Below is a discussion regarding these systems as well as the benefits of each system.

Open Circulatory System

This system is a lot simpler than the other. In this system, the heart directly pumps the blood out into open cavities. That means that the blood directly bathes the organs and tissues in the body. There are no arteries or major veins that can be found in this system. With these in mind, animals with open circulatory system typically have a lot of blood and have low blood pressure.

In this system, there is no direct distinction between blood and interstitial fluid. Blood is usually combines with interstitial fluid and is referred to hemolymph. The movement of the hemoplymph is facilitated by the muscular movement of the animal during locomotion however, diverting the flow of hemoplymph from one are to the other is limited. When the heart relaxes, the blood is drawn back towards the heart through open ended pores called ostia.

Closed Circulatory System

Closed circulatory system is more complex than the other one. This system is commonly found in larger and more active animals, including vertebrates. There are two major processes that are involved in the closed circulatory system and these are pulmonary and systemic circulation. Here, the blood is first transported into the lungs (pulmonary) to get oxygen and then distributed throughout the body by passing through the blood vessels (systemic). The blood is trapped inside the blood vessels as it travels along the body. The tissues and organs are not bathed with blood as opposed to the open system. The pressure inside the blood vessel , which is created by the pumping of the heart, is the “driving force” of the blood to go in and out of the heart.
In closed system, there is a distinction between blood and interstitial fluid because the blood is separated from the interstitial fluid by the blood vessels.

Advantages of the Open System

This system is very advantageous to small animals with slower metabolism (animals that are less active in processes such as locomotion, respiration, and digestion). The open system requires less energy for distribution because of the absence of blood vessels thus suits best those animals that gain and store less energy.

Advantages of the Closed System

This system is suited for larger, more complex, and active animals. This system operates with a much higher blood pressure. It also uses much lesser blood volume to gain higher and faster levels of distribution. Oxygenated blood and nutrients in closed systems reach distal parts of the body in a short period of time thus can meet the increasing need of energy. Animals with closed circulatory system have usually high metabolic rates and the capability of the closed system to provide immediate supply of energy is very well suited for this.