Excretory System: Characteristics, Parts And Operation
Of all the systems in the human body, the excretory system may be one of the least popular, especially since it is responsible for eliminating what our body does not need.
The elimination of urine is no small matter, since it is a liquid that contains substances that, if stored for too long in our body, could cause health problems such as poisoning.
Let’s see what the excretory system is in more depth which are the parts that are involved in the urine elimination process and how this liquid is formed.
The excretory system, also called the human urinary system, is a set of organs and other structures that are responsible for eliminating urine and sweat which are liquids that have diluted substances that cannot be used by the human body.
This system plays a fundamental role in excreting urine, given that the accumulation of substances present in it can lead to serious health problems, such as poisoning, infections and organ failure.
Maintain good hygiene and maintenance of this system, in addition to having healthy eating habits, guarantees optimal health, in addition to avoiding diseases such as cystitis, kidney stones, nephritis and kidney failure.
Parts of this system
Both kidneys and several excretory pathways are involved in the excretion process. Below we will detail these parts and explain their functions during the waste product removal process
Kidneys
These are two organs whose function is to filter blood and produce urine
The kidneys are located around the spine, at the level of the lumbar vertebrae, and They are surrounded by adipose or fatty tissue that keeps them at an adequate temperature in addition to protecting them from external impacts.
Its shape is similar to that of two beans, measuring 12 cm long, 5 cm long and 3 cm thick, weighing about 150 grams each.
Inside, two areas are distinguished. On the one hand we have the cortex, which is yellowish in color and is located on the periphery of this organ and, on the other hand, we have the medulla, which is located further inward and is reddish in color. Beneath the medulla and cortex is the renal pelvis, which collects urine and directs it towards the ureter. An artery enters this renal pelvis and a vein leaves.
In the outer layer of the kidneys are the nephrons, which are very small filters made up of an extensive network of blood vessels They filter blood to form urine. In each nephron there are three substructures: the Malpighian glomerulus, Bowman’s capsule and the renal tubule.
The kidneys perform two fundamental functions for the survival of the organism. They act as regulatory organs, since they maintain optimal levels of nutrients such as salts and glucose in the blood, in addition to having enough water so that they can be transported in the most efficient way possible.
In addition to its regulatory function, They serve as purifiers of the human body since they are responsible for extracting those substances that can be harmful if stored in large quantities, such as urea, the main component of urine, and uric acid.
Kidney diseases and dysfunctions can be extremely harmful conditions for humans. For this reason, they are some of the most transplanted organs, since their incorrect functioning can cause death.
Excretory pathways
They are ducts and cavities through which urine passes and is eliminated Basically there are three: ureters, bladder and urethra.
1. Ureters
They consist of two long tubes that connect the renal pelvis with the bladder They are composed of smooth muscle fiber and muscular epithelium, as well as nerve endings. These components are responsible for regulating the passage of urine towards the bladder, propelling it.
The nerve endings are very sensitive, for this reason, people who suffer from some type of obstruction such as a kidney stone feel a lot of pain.
2. Bladder
Possibly, along with the kidneys, it is the best-known part of the excretory system. It is a hollow organ where urine is stored, which arrives through the two ureters from the kidneys.
The bladder It is an elastic organ, capable of modifying its size to be able to store a large amount of liquid thanks to the fact that it is made up of muscle fiber walls, which can provide it with up to a liter of capacity.
Although the capacity of this organ can be very high, it is from 400 or 500 cubic centimeters of capacity when the urge to urinate is felt.
3. Urethra
It is the last tube through which urine passes before being eliminated. It is a tube that connects to the outside of the body and is located at the bottom of the bladder. It has two sphincters with muscular tissue which are responsible for regulating the outflow of urine.
There are differences in its structure depending on sex. The female urethra is between 3 and 4 cm in length, running from the base of the bladder to the labia minora, just in front of the vaginal opening. In the male case, the urethra can reach a length of 20 cm, distinguishing three parts: pelvic portion, membranous portion and spongy portion, the latter being the penis itself.
Sweat glands
Urea is not only excreted through urine through the process that we have explained. In addition to passing through the kidneys, ureters, bladder and urethra, urea can be eliminated through sweat, a liquid composed of water, mineral salts and a little urea. Essentially, this is more dilute urine.
In humans, the function of these glands is not only to eliminate substances. It also allows you to regulate body temperature allowing it to perspire by moistening the body surface.
These glands are spread throughout the skin, but they are especially concentrated in the head, armpits and palms of the hands, which is why they are the main places where you sweat when you do a sporting activity or get nervous.
How is urine formed?
The blood is introduced into the kidneys, where the nephrons will be responsible for remove waste products that are diluted in it, which can be harmful for the correct functioning of the body, becoming toxic.
There are three processes that occur in the formation of urine:
1. Filtration
The blood reaches the nephron, where it will be filtered by Bowman’s capsule. The substances that can be filtered here are small in size, excluding complex molecules and cells that may be found in the bloodstream such as platelets.
The liquid that remains as a result of this process is similar to blood plasma in its composition and may have beneficial substances for the body.
2. Resorption
The filtered liquid passes through nephron tubes, being reabsorbed, but selecting usable substances so that they return to the blood
If this is the case, it will be necessary to reintroduce them into the bloodstream through active transport, which implies an expenditure of energy, in addition to taking advantage of water from this plasma.
3. Secretion
Some substances that cannot be used but have been reabsorbed in the wrong way They are secreted from the blood capillaries into the nephron finally obtaining urine.
