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NEET UG 2026 » NEET UG Study Material » Biology » Small Intestine
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Small Intestine

The intestines (both small and large) take up most of the area of the abdominal cavity. It is the longest part of the digestive tube, with a length of approximately 20 feet.

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A circulatory system in which blood circulates twice via the heart is referred to as a double circulation system. In this type of circulation, the pulmonary circulation is separated from the systemic circulation by a membrane. This circulation requires the separation of the heart’s right and left sides: the right side pumps deoxygenated blood into the pulmonary component of the circulation, whereas the left side pumps oxygenated blood into the systemic circulation. When it comes to both mammals and birds, this is a common occurrence. Animals having only one circulatory system, like fish, on the other hand, have a two-chambered hearing system. We, like the majority of mammals including humans, have a twofold circulatory system, which means that we have two loops in our body where the blood circulates around it. Double circulation is the movement of blood throughout the entire body, and it includes the flow of-related substances.

1. Oxygenated blood: Blood that is rich in oxygen

2. Deoxygenated blood contains little to no oxygen and a high concentration of carbon dioxide.

Circulatory System

The circulatory system is made up of the heart and the blood vessels that carry blood throughout the body. In order to deliver oxygen, nutrients, and hormones throughout the entire body, the circulatory system must be functioning properly. Among its responsibilities are the delivery of oxygen and nutrients to all cells, the elimination of carbon dioxide and waste materials, the maintenance of an optimal pH and the movement of immune system components, proteins, and cells, to name a few. The circulatory system includes the heart, blood arteries, blood, lymph and lymph vessels, all of which are components of the body. In this regard, it is crucial to highlight that the circulatory system is frequently conceptualised as the vascular network that connects the heart, which is the primary cardiac organ. Despite the fact that the vascular network immediately associated with the heart is technically composed exclusively of blood and blood vessels, the terms circulatory and cardiovascular are frequently used interchangeably.

Advantage of Double Circulation

As we consider the relevance of twofold circulation, it is vital to note that the following points demonstrate how crucial it is for our bodies to have efficient circulation.

It contributes to the maintenance of elevated blood pressure.

It makes it possible for more blood to reach the tissues.

It contributes to the creation of higher pressure to pump blood throughout the entire body’s tissues and organs. It is possible to separate oxygenated blood from deoxygenated blood, which results in the intake of oxygen-rich blood and the elimination of carbon dioxide from the blood through the lungs, respectively. It contributes to the production of a substantial amount of energy required for the maintenance of life activities. Finally, we learned about double circulation and the primary organs that are engaged in double circulation at the conclusion of the article. As a bonus, we’ve learnt about the benefits of double circulation as well.

Types of Circulatory Systems

There are two types of circulatory systems in animals: open circulatory systems and closed circulatory systems. Open circulatory systems are more common in humans than in animals. The twofold circulation system is used by the vast majority of mammals, including humans. The closed circulatory system is further divided into two groups based on the number of times blood is circulated through the heart: the first group is classified as having a high frequency of blood circulation and the second group is categorised as having a low frequency of blood circulation.

Single Circulation

If there is only one circulatory system, the blood will pass via the heart and out through the gills, where it will be purified before being dispersed to different areas of the body. Because only one heart cycle is completed, the term “single circulation” is used. For example, solitary circulation is primarily observed in birds, fish, reptiles, and other such animals.

Double Circulation

The heart is the most important organ in the body for blood circulation, and two fold circulation is an efficient method of circulation because it provides an efficient method of circulatory system maintenance. What distinguishes them is that the blood travels through two different pathways – one for oxygenated blood and another for deoxygenated blood. As a result, the term “double circulation” was coined. The majority of mammals, including humans, have a two-stage circulatory system to transport oxygen and nutrients.

The human heart is divided into four chambers:

  • Left Atria
  • Right Atria
  • Left Ventricles
  • Right Ventricles

Furthermore, the pulmonary artery and vein connect the heart to the lungs, allowing blood to flow between the two organs. Double circulation is characterised by the presence of two channels through which the blood flows. They are as follows:

Systemic circulation

  • The systemic circulation transports oxygenated blood from the left ventricles to the capillaries of the body tissues
  • The oxygen-rich blood is delivered to the aorta, where it will be circulated to the numerous organs throughout the body
  • Later, the deoxygenated blood – which is high in carbon dioxide – is collected by the veins and venules from various regions of the body and sent to the heart
  • It is necessary to pump the deoxygenated blood back into the superior vena cava and subsequently into the right atrium
  • After receiving deoxygenated blood, the right atrium transports the blood to the right ventricle, where it is used for pulmonary circulatory support

Pulmonary circulation

  • The pulmonary circulation is characterised by blood circulation that begins in the right atrium and moves to the left atrium
  • The pulmonary artery is responsible for collecting blood from the right ventricle and transporting it to the lungs for oxygenation
  • Once the purification procedure is complete, the oxygenated blood is returned to the left atrium via the pulmonary vein, which then travels to the left ventricles for storage
  • The left ventricles are responsible for pumping oxygenated blood to the aorta, which is responsible for systemic circulation
  • Both oxygenated and deoxygenated blood are kept apart by double circulation, which helps to maintain a strong separation between the two. As a result, this circulation guarantees that the body has a consistent supply of oxygen at all times, while also increasing the efficiency of the body. This is also one of the reasons why mammals are able to keep their internal body temperatures constant. A third portal system, in addition to the double circulation system, is available to improve the efficiency of the circulation system

Conclusion

Double circulation is a type of blood circulation in which the blood circulates through the heart twice in a single cycle, as opposed to the single cycle system. Blood circulates twice as fast in humans as in other animals. The blood drawn from the body contains a high concentration of carbon dioxide and hence requires oxygenation in the lungs. Your heart functions as a pump, delivering nutrients to all of your organs, tissues, and cells throughout your body. As a result, your cells excrete waste materials such as carbon dioxide into your bloodstream, which is then returned to your heart.

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How does the Gastrointestinal (GI) Track work?

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Ginger has a long history of use as a carminative and chemical that aids in digestion by removing gas and soothing the intestines. Ginger is very effective in treating digestive disorders such as colitis and dyspepsia.

The small intestine has 3 parts named Duodenum, Jejunum, and Ileum. The duodenum is connected to the stomach. Food and liquid are digested in the Duodenum. Jejunum and Ileum absorb the nutrients.

Disorder of the small intestine leads to celiac diseases, infections, intestinal cancer, intestinal blockage, ulcers, pain and bacterial overgrowth.

The GI breaks down the food and liquid that we consume and carries it through the body. It enables the digestion process, helps absorb nutrients and proteins and eventually leads the waste products to the large intestine. Once the waste products are turned into stools, we excrete them. 

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