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The kidneys are typically associated with the production of urine, however it is by far not the only function of these organs. In fact, the kidneys in the human body perform many different tasks, because they take on, among others, also involved in metabolic processes, and also have an endocrine function. How are kidneys built, what are their functions and what kidney diseases do people have?

The kidney(Latinren , English kidney) is an organ that is even in humans. The kidneys are located inside the abdominal cavity in the so-called retroperitoneal space. The average weight of a human kidney is about 150 g, the length of the organ is about 10-12 cm, the width is 5-6 cm, and the thickness is 2-3 cm.

The left kidney in humans usually extends from the 11th thoracic vertebra to the second lumbar vertebra.

The right kidney (due to the vicinity of the liver) is typically located slightly lower, namely it is usually located between the 12th thoracic vertebrae and the intervertebral discs of the second and third lumbar vertebrae.

Kidneys: external structure

The structure of the kidneys is quite complicated. In this organ there are two surfaces (anterior and posterior), two ends (poles - upper and lower) and two edges (medial and lateral). In the described division, the edges are primarily important - within the medial edge (i.e. the one located closer to the spine and the center line of the body) there is a depression that forms the so-called the kidney cavity. It is here that the renal artery, which carries blood to this organ, comes to the kidney. In addition, in the cavity of the kidney there is a renal vein (which carries blood away from this organ), as well as the ureter, lymphatic vessels and nerve fibers. The kidney is surrounded by several sheaths. The most internally is the so-called fibrous bag, above it there is a layer of adipose tissue, forming the so-called fatty pouch. The outermost sheath of the kidney, on the other hand, is the renal fascia.The kidneysare adjacent to many different organs (the right kidney, including the liver and gallbladder, and the left kidney, including the stomach and spleen), but the adrenal glands ( adrenal glands), located near the upper poles of the kidneys.

Kidneys: internal structure

There are two parts to the kidneys:

  • kidney cortex (outer part)
  • kidney core (inner part)

Wwithin the second part of the kidneys, there are conical-shaped kidney pyramids, each of which ends with a renal papilla - in this place there are the so-called openings. collective coils.

The structural and functional unit of the kidney is the nephron. A single kidney contains approximately 1-1.5 million nephrons. Within such a renal unit, two main elements are distinguished: the glomerulus and the renal tubule.

The kidney glomerulus is a structure made of a network of capillaries, in which the basic tasks of the kidney take place, i.e. filtering the blood flowing through the organ. Looking at these structures more closely, it can be said that the glomeruli are composed of:

  • endothelial cells
  • podocytes
  • basement membrane
  • mesangium (glomerular support element)
  • cells of the wall epithelium

A nephron is not only a glomerulus, but also a renal tubule. This component of the kidney also consists of several parts and includes:

  • proximal winding tubule (closer, 1st order)
  • Henle loop with its components
  • distal spiral tubule (distal, second-order)

The filtrate obtained in the nephron passes from the distal convoluted tubule to the collecting tubules, from there the urine flows to the renal pelvis, which eventually becomes the ureter that leads out of the kidney. There is one ureter from the left and right kidneys each, which ultimately ends up in the bladder.

Kidneys: vascularization and innervation

Bykidneysa very large amount of blood flows - it reaches even 20-25% of the total stroke capacity of the heart (this means that 800 to 1200 ml of blood flow through the kidneys in a minute blood). Blood flows to the kidney through the renal artery, which is a branch of the abdominal aorta. The renal vein, which flows into the inferior vena cava, is responsible for the outflow of blood from this organ.

The innervation of the kidneys comes primarily from the autonomic system. Sympathetic fibers to the kidneys are sent from the renal plexus, and the parasympathetic innervation of the kidneys is in turn responsible for, among others, vagus nerve. Sensory impulses from the kidneys are directed to the thoracic segments (Th10-Th11) of the spinal cord - it is for this reason that various kidney diseases can lead to pain in the loin area.

Kidneys: Features

The primary task of the kidneys is the production of urine, but these organs also have many other functions - they show hormonal activity, are responsible for the production of vitamins, and also participate inprocesses of maintaining homeostasis (balance) of the organism.

  • Kidney function: urine production

The blood reaching the kidneys is filtered in the structures of the glomerulus - this applies to about 10% of all blood flowing through this structure, which (taking into account the previously given values) means that 80- 120 ml of liquid. This parameter is known as the glomerular filtration rate (GFR) and is one of the primary indicators that physicians can use to conclude that kidney function is normal. it is completely excreted - if it were so, then in a day the human body would produce even about 180 liters of urine. The first filtrate is called primary urine and it undergoes various processes within the remaining elements of the nephron. These include such phenomena as, for example, resorption (reabsorption of various substances into the blood), but also the excretion of various metabolic products and electrolytes into the urine.

The previously described parts of the renal tubules that make up the nephron have different functions:

  • absorption takes place in the proximal tubule, incl. sodium, potassium and calcium ions, as well as glucose, amino acids and urea, in addition, along with these substances in the proximal tubule, water absorption also takes place (here the primary urine volume is reduced by up to 70%); in this part of the nephron, for example, drugs taken by the patient (e.g. antibiotics) are secreted into the urine,
  • in the Henle loop, urine is further concentrated - this is due to the complex processes of transporting sodium, chlorine and water ions,
  • in the distal tubule there is mainly reorption of sodium ions into the blood, absorption of which is associated with the excretion of potassium ions into the urine.

The urine produced in the course of the described processes enters the collecting tubules, from which it finally goes to the ureter, from where it is transported to the bladder and excreted from the body. How much work has to be donekidneyscan be convinced by the fact that the large - because it reaches much more than 100 liters - amount of primary urine produces an average of about 1.5 liters of final urine per day .

  • Other Kidney Functions

The kidneysalso have endocrine activity: they produce renin (primarily involved in the regulation of blood pressure) as well as erythropoietin (the hormonestimulating the production of red blood cells). These organs also produce prostaglandins and kinins (which have a vasodilating effect), and in addition, the kidneys synthesize the active form of vitamin D. The kidneys' task is to regulate the water and electrolyte balance, but not only - they also affect the acid balance - basic. This is due to the fact that these organs are responsible for the processes of regulating blood concentrations, including hydrogen ions, but also bicarbonate ions.

The kidneys are also responsible for regulating blood pressure. The hormone they produce - renin - is one of the elements of the so-called the renin-angiotensin-aldosterone system (RAAS). These organs are also sensitive to the action of many different hormones involved in the regulation of blood pressure, such as vasopressin (an antidiuretic hormone, ADH) or atrial natriuretic peptide (ANP). The kidneys are also involved in the course of various metabolic processes - for example, during periods of fasting, these organs may produce glucose (referred to as gluconeogenesis).

Kidneys: diseases

Kidney development begins as early as the 4th week of fetal life - so it is probably not surprising that the course of these developmental processes may be disturbed and may lead to the appearance of congenital kidney diseases and defects. It can be, for example :

  • horseshoe kidney
  • agenesis (missing) kidneys
  • congenital hydronephrosis
  • duplication of the ureter
  • congenital cystic kidney

The above-mentioned units are treated as defects in the development of the kidneys. Among the diseases affecting these organs, however, many other and different problems are mentioned, which may be related both to inherited genetic mutations and may be acquired in the course of life. The most famous kidney diseases are:

  • urolithiasis
  • glomerulonephritis
  • Diabetic Nephropathy
  • pyelonephritis
  • Lupus Nephropathy
  • Alporta team
  • polycystic kidney disease
  • renal hypertension
  • kidney cancer (there are both primary tumors, such as clear cell carcinoma of the kidneys in adults or Wilms' tumor in children, as well as metastatic tumors from other organs)
  • kidney abscess
  • renal failure (both acute and chronic)

There are many other pathologies within the kidneys. Probably for this reason, in the field of internal diseases, their specialist department dealing with kidney diseases stands out - we are talking here about nephrology and aboutdoctors dealing with kidneys, or nephrologists. Kidney diseases and their symptoms are worth mentioning primarily in connection with one aspect. Well, the kidneys have a large functional reserve - it is estimated that before a patient develops any symptoms of kidney disease, about 3/4 of the entire volume of the parenchyma of these organs must be damaged. Before that, yes - the patient may experience some symptoms, but they may be subtle and poorly expressed. This is why regular urine tests are so important and that you visit your doctor if you suspect any abnormalities - early diagnosis of renal dysfunction will allow for faster treatment, and therefore there is a good chance that the possible disease can be stopped before it has time. she can lead to irreversible kidney damage.

  • Kidney pain - causes
  • Symptoms of a sick kidney
  • Artificial kidney (dialyzer): how does it work? Types of dialyzers
  • Kidney injuries - classification, symptoms, treatment
  • Mobile (wandering) kidney - causes, symptoms, treatment

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