Problem 150 - Objective Biology for NEET

Question

The blood circulation, which starts and ends into capillaries is (a) Portal circulation (b) Renal circulation (c) Hepatic circulation (d) Lymphatic circulation

Step-by-Step Solution

Answer

The correct answer is (a) Portal circulation.

Step 1: Recognition of the Definitions

Firstly, the definitions of the provided options should be recognized. 'Portal circulation' is the movement of blood from digestive organs to the liver. 'Renal circulation' refers to the blood supply to the kidneys. 'Hepatic circulation' is the circulation of blood in and out of the liver. 'Lymphatic circulation' involves the circulation of lymph fluid around the body.

Step 2: Comparison

Once the definitions of the different types of circulation are understood, we can compare them with the characteristics given in the question - which is about the circulation that starts and ends in the capillaries. Out of the given options, only Portal circulation matches this characteristic as it starts in the capillaries of the gut and ends in the capillaries of the liver.

Step 3: Conclusion

Given that the question asks about the type of circulation that starts and ends into capillaries and based on the comparison of all the definitions, it's clear that the portal circulation is the correct answer.

Key Concepts

Blood Circulation

The human body has a remarkable system known as blood circulation, which plays a crucial role in maintaining life. This system involves the flow of blood through two primary circuits: the systemic and the pulmonary circuits. The systemic circuit carries oxygenated blood from the heart to the rest of the body while returning deoxygenated blood back to the heart. On the other hand, the pulmonary circuit deals with the transportation of blood to the lungs for oxygenation.

Blood circulation involves several key components, including the heart, arteries, veins, and capillaries. The heart acts as the pump, driving the blood through the arteries that branch out into smaller arterioles and eventually into capillaries. In this intricate network of capillaries, the exchange of gases, nutrients, and waste products occurs.

• Arteries carry oxygen-rich blood away from the heart.
• Veins return oxygen-poor blood back to the heart.
• Capillaries facilitate the exchange between blood and tissues.

This continuous flow of blood ensures that every cell in the body receives the oxygen and nutrients it needs while simultaneously removing waste products like carbon dioxide.

Capillaries

Capillaries are tiny blood vessels that form a network throughout the body's tissues. They connect arterioles and venules and are crucial for the exchange of oxygen, carbon dioxide, nutrients, and waste. The walls of capillaries are extremely thin, consisting of just a single layer of endothelial cells, which allows for efficient diffusion of substances.

The capillary network is vital for tissue health as it ensures that all body parts are adequately supplied with nutrients and oxygen. Here is how capillaries work:

• Oxygen and nutrients diffuse out of the capillaries and into surrounding tissues.
• Carbon dioxide and waste products move from the tissues into the capillaries for removal.

Since capillaries are so numerous and widespread, they have an enormous collective surface area, greatly enhancing their ability to exchange substances between blood and tissues. This makes them a fundamental part of the circulatory system and vital for the body's metabolic processes.

Hepatic Circulation

Hepatic circulation is an essential component of the body's blood flow focused on the liver. This circulation is unique because it involves two types of blood supply: oxygen-rich blood coming from the hepatic artery and nutrient-rich blood coming from the hepatic portal vein.

The hepatic portal vein carries blood from the digestive organs and spleen to the liver. This blood is rich in nutrients absorbed from digested food. Inside the liver, this blood undergoes processing, where toxins are detoxified, and nutrients are stored or metabolized.

• The liver receives approximately 75% of its blood supply from the hepatic portal vein.
• The remaining 25% is supplied by the hepatic artery, carrying oxygenated blood.
• This dual blood supply supports the liver’s metabolic and detoxifying functions.

Moreover, the blood from the liver eventually drains into the hepatic veins, which then empty into the inferior vena cava, returning to the heart. This circulation is vital as the liver plays key roles in metabolism, detoxification, and regulation of biochemical levels in the blood.