Anatomy & Organs

Kidney – structure, function & diseases


The kidneys perform important functions in the human organism. Kidney disorders impair physical regulatory processes that are vital.

What is the kidney

The kidney is an internal organ that is duplicated in all vertebrates. In science, the kidney is assigned to the so-called urinary system; The urinary system is a group of organs involved in the production and excretion of urine.

The kidneys assume important functions within this group of organs. The Greek term for kidney is nephros ; against this background, a medical branch dedicated to the kidneys is also called nephrology .

In its outer shape, the kidney resembles a bean. The organ in a healthy adult has an approximate length of 12 centimeters. A kidney weighs around 150 grams.

Anatomy & Structure

In humans, the two brown -red kidneys are on the right and left of the spine . The kidney is to be localized at about the level of the lowest ribs and behind the peritoneum.

On top of each kidney is a comparatively smaller adrenal gland , which is roughly crescent-shaped. The kidney consists of the renal medulla and a renal cortex that encloses the medulla. The renal cortex contains, among other things, renal corpuscles and parts of the renal tubules (tubular elements).

The kidney is connected to the human bloodstream via the renal vein and renal artery. For example, while the stomach , spleen and pancreas are adjacent to the left-hand kidney , the kidney on the right-hand side of the body is overlapped by the liver – which is why the right-hand kidney is usually slightly lower than the left-hand organ.

Different nerves cross each kidney on the back, which can cause kidney pain to radiate to the lower abdomen.

Functions & Tasks

In the human body, the kidney functions in particular as a filter organ. For example, blood is filtered in the renal corpuscles of the renal cortex.

The product of this filtering by the kidneys is the so-called primary urine (unconcentrated urine ). The primary urine contains, among other things, components (such as toxins) that are to be excreted – these are now filtered out in a further step by the kidneys to such an extent that the end urine (urine) is formed.

Other components of the primary urine that the organism still needs (such as water and sugar) are fed back into the bloodstream in parallel through the kidneys (or the renal tubules). The urine eventually collects in the renal pelvis and from here travels to the ureters and bladder to be excreted.

The kidneys are also involved in the water balance of the organism via urine production – the kidneys therefore also have an influence on the regulation of blood pressure .

Last but not least, the kidneys also support the body’s electrolyte balance (salts, for example, belong to the electrolytes ) by controlling the concentration of urine.

Other tasks of the kidneys include, for example, the production of hormones that are required for blood formation and the formation of vitamin D3.


Complaints and diseases that can affect the kidneys are of a diverse nature. Impairments of the kidneys often lead to disorders of the kidney functions. As a result, various regulatory processes of the organism are affected.

A distinction can initially be made, for example, between diseases that affect the renal corpuscles and those that affect the renal tubules. Impairments of the kidney corpuscles are often caused by autoimmune reactions – in this case the immune system turns against the body’s own tissue by mistake.

Diseases of the renal tubules, on the other hand, are often caused by acute infections (bacterial inflammation of the renal pelvis should be mentioned here ) or the influence of harmful substances.

Congenital impairments of the kidneys can be expressed, for example, in various malformations; for example, only a single kidney can be formed. Other possible kidney diseases also include malignant enlargements (tumors) or metabolic diseases (such as gout , which causes deposits of uric acid crystals).

Loss of function of the kidneys with possible subsequent kidney failure is finally referred to as renal insufficiency .

Typical & common diseases

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.