Kidneys are one of the vital organs of our body. These are available in pairs and if one of it is not functioning properly, the other one can take care of it. The Kidneys filter the waste and act as disposal system of the body. Approximately 1/3 of all blood exiting the heart flows into the kidneys for filtration before it flows to the rest of the body’s tissues.

What are Kidneys?

Kidneys are a pair of organs located below our ribs, in the back of the abdomen. It has purplish-brown colour and is solely responsible for removing liquid waste from blood, which is later excreted in the form of urine.

What is the structure of Kidney?

The Kidneys are bean-shaped and their concave sides known as renal hilus, face each other and these are connected to the blood vessels – renal artery and renal vein, and also to the ureter that takes urine out of the Kidney. The Kidney is covered by a fibrous layer of connective tissue and the layer is called renal capsule. Under this layer is a soft inner layer of tissues known as renal cortex, which covers another layer known as renal medulla. This renal medulla is made of seven cone-shaped tissues known as renal pyramids. The bases of the renal pyramids are towards the renal cortex and the apexes are facing towards the center of the Kidney. Each of the apexes is connected to a small hollow tube known as calyx which collects urine. These small calyces join together forming 3 large calyces. These 3 calyces merge together to form the funnel-shaped hollow renal pelvis which is connected to the ureter outside the Kidney.

What are its functions?

The most important function of Kidney is the formation of urine from the waste product in the blood and passing it on to the ureters to excrete. After extracting all the necessary nutrients from the food that we eat, the waste product that gets mixed with blood is urea. When the urea-mixed blood enters the Kidneys, the urea is removed through tiny filtering units of the Kidney known as nephrons and after mixing with water, it becomes urine. Kidneys also produce a hormone known as erythropoietin which helps in the formation of red blood cells and also helps in the regulation of blood pressure. It also regulates the salt, potassium and acid content of our body.

How do Kidneys process urine?

The Kidneys have the filtering units known as nephrons which are present in millions. The nephrons have two parts; renal corpuscle and renal tubules. The renal corpuscles are made up of blood capillaries known as glomerulus and the cap-like sac known as glomerulus capsule (Bowman’s capsule) that encloses the glomerulus. While the glomerulus separates urea from the blood and forms urine, the Bowman’s capsule holds the urine passed on from the glomerulus. The urine is then transferred to the renal tubules which carry it to the renal pelvis that finally goes out of the Kidney connecting to the ureters.

How does blood circulate in the Kidneys?

From the abdominal aorta, the renal arteries enter the Kidneys and are divided into smaller arterioles which carry the blood towards the renal cortex. In the renal cortex, the arterioles are bundled up into glomerulus. Then, there are arterioles that diverge out from the glomerulus and get into the renal medulla. From there, the arterioles are separated into tiny blood vessels known as peritubular capillaries surrounding the renal tubules. These peritubular capillaries merged together to form renal veins which make exits from the Kidney joining the inferior vena cava (vein carrying de-oxygenated blood) carrying blood to the heart.

What are the disorders related to Kidneys?

Chronic Kidney disease is the most common form of Kidney disorder. In this the Kidneys are damaged and they stop filtering the blood for the waste products. This may lead to accumulation of waste products from the blood in our body.
Other Kidney-related diseases are as follows:
Kidney cancer: Herein, the cancer grows in the inner linings of the Kidney tubes. The most common type of Kidney cancer in adults is renal cell carcinoma. Although even other rare types of Kidney cancer can occur. Wilms’ Tumor is a kind of Kidney cancer that mostly young children are likely to develop. Polycystic Kidney disease has the fluid-filled sac of Kidneys known as cyst in place of the normal tissue. Due to this, the Kidneys enlarge and function poorly which may eventually lead to Kidney failure. Kidney stones are the solid pieces formed inside the Kidney due to the accumulation of small particles or dietary minerals in the urine.

What are the causes of these diseases?

Chronic Kidney disease is mainly caused by diabetes and high blood pressure. Kidney cancer may cause because of smoking, genetic conditions and excessive intake of painkiller medicines. Polycystic Kidney disease is mostly genetic and Kidney stones are mainly because of the grains we consume along with our food which remains in the blood and later on accumulates together forming a solid particle in the Kidney.

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