What is the function of kidney blood circulation

In today's social life, various diseases can be seen everywhere. But people don’t understand its symptoms and causes, so they don’t know where to pay attention and improve it. The human internal organs all play important roles. They all have their own channels to be responsible for and functions to provide for the human body. Some are responsible for detoxification, some are responsible for blood transport, so what is the role of renal blood circulation?

The blood supply to the kidneys comes from the left and right renal arteries that branch off from the abdominal aorta. The renal artery enters the kidney at the renal hilum, divides into several interrenal arteries, and then branches into interlobar arteries and interlobular arteries. It then sends out afferent arterioles along the way, enters the renal corpuscle to form a glomerulus, and then merges into an afferent arteriole to leave the renal corpuscle, and then forms a capillary network around the renal tubule, which then gathers into interlobular veins, and finally returns to the inferior vena cava through veins at all levels.

1. Characteristics of kidney blood supply

The kidneys have a rich blood supply. When a normal adult is at rest, about 1200 ml of blood flows through the kidneys on both sides per minute, accounting for about 1/5 to 1/4 of the cardiac output, of which about 90% of the blood is distributed in the renal cortex and about 10% in the renal medulla.

The blood supply to the kidneys passes through two capillary networks. Higher blood pressure in the capillaries within the glomerulus will be beneficial to glomerular filtration. The blood pressure in the capillary network around the renal tubules is lower, which is conducive to renal tubular reabsorption.

2. Regulation of renal blood flow

Renal blood flow is a prerequisite for urine formation, and the regulation of renal blood flow includes autoregulation and neurohumoral regulation.

(1) Self-regulation

Autoregulation of renal blood flow means that when the mean arterial blood pressure of the renal artery fluctuates within a certain range (80-180 mmHg), the renal blood flow remains basically constant. This phenomenon is called autoregulation of renal blood volume. The current explanation for the mechanism of renal blood flow autoregulation is based on the myogenic theory and the tubuloglomerular feedback theory.

The myogenic theory believes that: when renal perfusion pressure increases, the vascular smooth muscle is stretched due to the increased perfusion pressure, which increases the tension of the smooth muscle, reduces the caliber of the blood vessels accordingly, and increases the blood flow resistance, so that the renal blood flow does not change much; when the perfusion pressure decreases, the opposite change occurs. This keeps renal blood flow relatively constant.

The tubuloglomerular feedback theory holds that: when renal blood flow and glomerular filtration rate increase, the flow rate and sodium content of the tubular fluid reaching the macula densa of the distal convoluted tubule increase, and the macula densa sends information to restore renal blood flow and glomerular filtration rate to normal. On the contrary, when renal blood flow and glomerular filtration rate decrease, the flow and sodium amount of tubular fluid flowing through the macula densa decrease, and the macula densa sends information to increase renal blood flow and glomerular filtration rate to normal levels.

(2) Neurohumoral regulation

Generally speaking, the vasoconstrictive effect of the renal sympathetic nerves is not obvious. Epinephrine, norepinephrine, antidiuretic hormone, angiotensin, etc. have a constrictive effect on renal blood vessels; prostaglandins have a dilating effect on renal blood vessels. However, the significance of these vasoactive substances in normal renal blood flow regulation is still uncertain.

Generally speaking, under normal circumstances, when arterial blood pressure fluctuates within a certain range, the kidneys mainly rely on their own regulation to keep blood flow relatively stable and maintain normal urinary function. In an emergency, the sympathetic nerves are stimulated and the action of norepinephrine is used to redistribute blood throughout the body, reducing renal blood flow and thus ensuring blood supply to important organs such as the brain and heart.

After reading the above introduction to the role of renal blood circulation, I think everyone should have understood it. The kidneys are responsible for transporting blood and have many functions. They can regulate themselves to ensure that various organs receive blood supply. We must protect every organ in our body and seek early treatment if any problems are discovered, otherwise certain diseases may occur.