The 4 most important parts of the kidney, and their functions.

A summary of the main parts of the kidney, with their characteristics and functions in the organism.

The urinary system is responsible for the formation, conduction and storage of urine, a yellowish colored liquid that is obtained as a result of the purification and filtering of the individual's blood.

This mechanism is essential for the maintenance of balance in the organic fluids, as well as for the elimination of toxic substances and even the maintenance of blood pressure. and even the maintenance of blood pressure. Therefore, it comes as no surprise to anyone to learn that humans excrete an average of one and a half liters of urine per day, depending on the food and liquids ingested.

We cannot talk about the urinary system without focusing our eyes and minds on the kidneys, since they are one of the only two components that make up this apparatus, together with the urinary tract. Although every human has an overview of this pair of interesting organs, the kidneys hold many more secrets than it might at first appear. Therefore, today we tell you about the parts of the kidney and their functions.

Parts of the kidney and its functions: beyond the formation of urine.

If we think of the urinary system, the first thing that comes to mind is the production of urine (logical, since this word is included in the first term). However, the kidneys do not limit their functionality, the kidneys do not limit their functionality to blood purification.. Therefore, in the first instance, we show you all the activities performed by the kidneys for the physiological and metabolic balance of human beings:

• Regulation of the volume and osmolarity (particle concentration) of body fluids. This is achieved by balancing the concentration of ions and water.
• Excretion of waste products, whether they are the product of normal cellular functioning or the entry of foreign agents into the body.
• Synthesis of glucose from amino acids and other precursors. It accounts for 10% of the production of this monosaccharide in the body.
• Regulation of erythropoiesis (red blood cell production) by secretion of the hormone erythropoietin.
• Regulation of Blood Pressure by secretion of vasoactive factors such as renin (involved in the formation of angiotensin II).
• Regulation of acid-base balance, mainly by excretion of acidic substances. This is essential to maintain a balanced internal pH.
• Production of 1,25-dihydroxyvitamin D3 (activated vitamin D), essential for maintaining adequate bone calcium levels.

As we can see, we are dealing with multidisciplinary organs, since they are not only responsible for the elimination of substances, but also for the synthesis of sugars such as glucose and hormones such as renin, erythropoietin or kallikrein. are also responsible for the synthesis of sugars such as glucose and hormones such as renin, erythropoietin or kallikrein, all with different functions on the organism.all of which have different functions in the body.

It is incredible to think that a couple of organs that account for no more than 1% of a person's body weight can become so key to their survival, isn't it? All this is put into perspective when we discover that, for example, kidney irrigation accounts for about 22% of cardiac output.. The volume of blood passing through these structures at any given time is, therefore, a not inconsiderable value.

Once we have established the functionality of these incredible structures, let us dive into their characteristic morphology.

1. External protective tissues

Let's start from the outside and dissect the kidney mass little by little. First of all, it is necessary to note that each of these two organs is surrounded by three different layers of tissue:

• The outermost is known as the renal capsule, a transparent, fibrous, continuous membrane that serves to protect the kidney from possible infections.
• A fatty capsule, a layer of fat of variable thickness that protects the kidney from shocks and traumas and holds it in place in the abdominal cavity.
• The renal fascia, a layer of connective tissue that separates the adipose capsule from the pararenal fat.

It is especially important to remind readers that this system, not being in direct contact with the environment, does not have a microbiome or associated bacterial agents beneficial to its functions.. For this we have these protective tissues, with the purpose of not allowing pathogens to enter and generate the dreaded urinary tract infections.

2. Renal cortex

This layer corresponds to the outermost part of the kidney. It is one centimeter thick and has a brownish red color. This area contains 75% of the glomeruli, which are a network of small blood capillaries through which the purification and filtration of the kidney takes place. through which the clearance and filtration of blood plasma takes place, as the first part of the urine-forming process.

Therefore, the renal cortex receives 90% of the blood flow entering these organs and has a filtration, reabsorption and secretion function. It should be noted that this outermost layer is not separated longitudinally from the renal medulla, since a series of protrusions called renal columns are produced towards them.

3. Renal medulla

The renal medulla, on the other hand, is located in a deeper point of the kidney and presents a greater morphological complexity, since it is composed of conical units (with a base directed to the cortex) called renal pyramids.It is composed of conical units (with the base facing the cortex) called renal pyramids, which are divided by renal columns and their number varies between 12 and 18. These are divided by renal columns and their number varies between 12 and 18. Therefore, we can say that the human kidney is a multilobed organ.

The vertex of each renal pyramid ends in a minor calyx, and the union of several of them give rise to the major calyces, which unite to generate the renal pelvis.. We have to imagine this structure as if it were a tree: the renal pelvis is the trunk, and the calyces are each of the branches that lead to large leaves (the renal pyramids).

Finally, it should be noted that the renal pelvis corresponds to the section of the ureter.Therefore, the urine will travel through here to the bladder, where it will accumulate until it is emptied by the well-known process of urination.

4. The nephron

It seemed that this moment was not going to come, but we cannot leave out the nephron: the basic structural and functional unit of the kidney, where the blood is filtered and purified.. To put things in perspective, there are an average of 1.2 billion nephrons in each kidney, which filter a whopping 1.1 liters of blood per minute.

As much as it is extremely difficult to make a mental picture of this complex structure, we will describe its parts briefly:

• Glomerulus/ renal corpuscle: already named above, it is the set of capillaries where the clearance and filtration of blood plasma takes place.
• Bowman's capsule: Hollow sphere in which the filtration of the substances to be excreted takes place. It surrounds the glomerulus.
• Proximal convoluted tubule: its function is to increase the surface area for reabsorption and secretion of substances.
• Loop of Henle: a forked tube leading from the proximal convoluted tubule to the distal convoluted tubule.
• Distal convoluted tubule: an ion-permeable tube that collects waste substances that were not initially filtered into Bowman's capsule.

As confusing as all this terminological conglomerate may seem, the idea to be clear is that the nephron is a highly specialized functional unit for the purpose of blood filtration. This is captured in four simple steps: filtration, tubular secretion, tubular reabsorption (recycling of nutrients and substances such as glucose, amino acids, 60-70% potassium and 80% bicarbonate), and excretion, i.e., the emptying of the blood.i.e. the emptying of the nephron.

It should be noted that, after the age of 40, an average of 10% of nephrons are lost every 10 years. This happens because the kidneys are not able to regenerate them. Even so, it has been seen that the remaining nephrons adapt to maintain adequate renal function within the limits of normality.

Conclusion

As we have seen, not only are the parts of the kidney and their functions highly complex, but each of these organs is made up of millions of tiny individual filtering machines: the nephrons.

We should view the process of filtration and urine generation as a tree-like machinery.From the small capillaries called glomeruli, where blood filtration takes place at the most microscopic level possible, to the renal pelvis (the place where the urine is collected from the kidneys to the bladder), the urine undergoes a series of changes and reabsorptions that result in the yellowish liquid to be expelled.

Bibliographic references:

• Rodrigues, C. F. S., Olave, E., Gabrielli, C., & Sousa, L. M. C. (1997). Anatomical considerations on renal fusion: a case report. Revista chilena de anatomía, 15(1), 51-55.
• Cachofeiro, V., Lahera, V., & Tresguerres, J. A. (1999). Anatomofunctional aspects of the kidney. HUMANA, 374.
• Anatomy of the urinary system, stanfordchildrens.org. Retrieved September 9 at https://www.stanfordchildrens.org/es/topic/default?id=anatomyoftheurinarysystem-85-P04568.
• Urinary system, Laboratory of Physical Anthropology and Human Anatomy. Picked up on September 9 at http://www.anatomiahumana.ucv.cl/morfo2/ren.html.