The urinary system is responsible for the formation, conduction and storage of urine, a yellowish-coloured liquid by all known to be obtained due to the purification and filtering of the individual’s blood.
This mechanism is essential for maintaining balance in organic fluids and the elimination of toxic substances and even the maintenance of blood pressure. Therefore, it is no surprise for anyone to know that humans excrete an average of one and a half litres of urine per day, depending on the food and liquids ingested.
We cannot speak of the urinary system without posing the eyes and mind in the kidneys, because they are one of the only two components that form this system, along with the urinary tract. Although every human has an overview of this pair of interesting organs, the kidneys keep many more secrets than they might initially seem. That’s why today we talk to you about the parts of the kidney and its functions.
Parts of the kidney and its functions
If we think about the urinary system, the first thing that comes to mind is urine production (logical, because this word is included in the first term). Still, the kidneys do not limit their functionality to blood purification. Therefore, in the first instance, we show you all the activities that the kidneys perform for the physiological and metabolic balance of humans:
- Regulation of the volume and osmolarity (concentration of particles) of bodily fluids. This is achieved by balancing the concentration of ions and water.
- Excretion of waste products, whether as a result of normal cellular functioning or by foreign agents’ entry into the body.
- Glucose synthesis from amino acids and other precursors. It accounts for 10% of the production of this monosaccha arid at the body level.
- Regulation of erythropoiesis (red blood cell production) by secreting the hormone erythropoietin.
- Regulation of blood pressure by secreting vasoactive factors such as renin (involved in the formation of angiotensin II)
- Regulation of acid-base balance, mainly by excreting acidic substances. This is essential to keep the internal pH balanced.
- Production of 1.25-dihydroxy vitamin D3 (vitamin D activated), essential to maintain calcium levels in the proper bones.
As we can see, we are dealing with multidisciplinary bodies, because not only are they responsible for the elimination of substances, but they are also responsible for the synthesis of sugars such as glucose and hormones such as renin, erythropoietin or calibre in, all with different functions on the body.
It’s amazing to think that a pair of organs that don’t account for more than 1% of a person’s body weight can become so key to their survival, right? All of this is put more into perspective when we discover that, for example, kidney irrigation accounts for approximately 22% of cardiac output. The volume of blood passing through these structures at any given time is, therefore, a value for nothing to be despicable.
Once we have cemented the functionality of these incredible structures, let’s immerse ourselves in their characteristic morphology.
External protective fabrics
Let’s start from the outside and gradually dissect the kidney mass. First, it is necessary to narrow that each of these two organs is surrounded by three different layers of tissue:
- The outerest is known as the renal capsule, a clear, fibrous and continuous membrane that serves to protect the kidney from possible infections.
- An adipose capsule, that is, a layer of fat of variable thickness that protects the kidney from shock and trauma and that keeps it in place in the abdominal cavity.
- Renal fascia, a layer of connective tissue that separates the adipose capsule from pararennal fat.
It is of particular importance to remind readers that this system, because it is not in direct contact with the environment, does not have a microbiome or bacterial agents associated beneficial to its functions. To do this we have these protective tissues, so that pathogens do not sneak in and generate the dreaded urine infections.
This layer responds to the outer side of the kidney. It is one centimeter thick and has a brownish red coloration. This area contains 75% of glomericals, which are a network of small blood capillaries through which blood plasma purification and filtration occurs, as the first part of the urine forming process.
Therefore, the renal cortex receives 90% of the blood flow that enters these organs and has a function of filtration, reabsorption and secretion. It should be noted that this outerr layer is not longitudinally separated from the renal marrow, as a series of protrusions called renal columns occur towards them.
The renal marrow, on the other hand, is located at a deeper point in the kidneyand has a greater morphological complexity, as it is composed of conical-looking units (with the base directed at the cortex) called renal pyramids. 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 apex of each renal pyramid flows into a smaller chalice, and the union of several of them give rise to the major calyxes, which come together 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 calyxes each of the branches that lead to large leaves (the renal pyramids).
Finally, it is necessary to narrow that the renal pelvis corresponds to the section of the ureter,therefore, the urine will travel here to the bladder, where it will accumulate until its emptying by the urination process by all known.
It seemed that this moment was not going to come, but we cannot leave ourselves in the inkwell to the nephron: the basic structural and functional unit of the kidney, where the blood is filtered and purified. To put things into perspective we will say that there is an average of 1.2 billion nephrons in each kidney, which filter the refrigerator of 1.1 liters of blood per minute.
As much as it is extremely difficult to make a mental image of this complex structure, we will describe its parts briefly:
- Glomerrulo/ renal corpuscle: already named above, is the set of capillaries where the clearance of the blood plasma and filtration occurs.
- Bowman capsule: Hollow sphere in which the filtering of the substances to be excreted is performed. It envelops the glomerrulo.
- Proximal contoured tubulum: its function is to increase the surface area of reabsorption and secretion of substances.
- Henle Handle: A fork-shaped tube that leads from the proximal contoured tubulum to the distal contoured tubulum.
- Distal contoured tubulum: ion-permeable tube that collects waste substances that were not initially filtered into Bowman’s capsule.
As smooth as all this terminology conglomerate may seem, the idea to be clear is that nephron is a highly specialized functional unit in order to perform blood filtering. This is reflected 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 nephron.
It should be noted that, from the age of 40, an average of 10% of nephrons are lost every 10 years. This happens as the kidneys are not able to regenerate them. Still, the remaining nephrons have been seen to adapt to maintain proper kidney function within the limits of normal.