The urinary system is one of the cleansing systems of the body. It removes excess water, salts, and nitrogenous wastes via urine. Urine is one of the three primary mala or wastes from the body along with the feces and the sweat.
Urine helps to maintain the electrolytes balance within the body fluids. Both the functioning, amount, and appearance of urine depends upon the water intake, kind of foods, temperature of the surroundings, mental state, and physical condition of the individual.
Functions of the Urinary System
- The urinary system has a very important blood cleansing function from the wastes. In fact, the quality of blood tissues depends much more on proper functioning of the urinary system than the diet itself.
- Elimination of cellular metabolic wastes and toxins.
- Elimination of excess nutrients and excess hormones.
- It regulates blood pressure and also maintains the normal pH of the blood via electrolytic balance.
- The kidney acts as an endocrine system organ and secretes erythropoietin hormone that stimulates red blood cell formation from bone marrow.
- The kidney also plays a role in the final activation of Vitamin D.
Ayurvedic View of Urinary System
In Ayurveda generation of the urine is regulated by the Pitta Dosha while its elimination is regulated by Vata Dosha. Any imbalances in either of the two Doshas can result in urinary disorders such as Urinary Tract Infections, Bladder inflammation, and Kidney Disorders.
Perspiration and Urination – A delicate Balance
Perspiration or sweating happens via the skin. As stated earlier, sweat is also one of the three primary body wastes along with urine and feces. Adequate sweating is essential to keep the water and electrolyte balance within the skin tissues and to regulate the temperature of our body.
The kidneys and the skin function in tandem as both are responsible for the excretion of excess water and the electrolyte waste products. Perspiration increases significantly when one is exposed to high-temperature surroundings. It is essential to prevent our body from overheating in hot environment and hence prevent damage to our body systems.
Excess sweating results in reduced urine volume as the waste products are eliminated through sweat channels. Similarly, in cold weather conditions, one tends to sweat less as our body tries to preserve heat and maintain body temperature. This results in increased urine volume and frequency.
Excessive sweating or urination leads to coldness and dehydration. Any imbalance between perspiration and urination leads to health disorders. Some of the examples are Diabetes, psoriasis, dermatitis, and ascites (dropsy).
Urinary System Organs
There are two kidneys. The smallest structural and functional unit of the Kidney is the nephrons. There are about 2 or 3 million nephrons disturbed in both Kidneys.
The kidneys are highly vascularized organs. Around 1.2 L of blood flows through the kidneys per minute. This is almost one-fifth of the cardiac throughput. On a per weight basis, the kidneys handle the highest blood flow. Much more than the heart, brain, or liver.
At the end of each Kidney, there is a funnel-like shape called Ureter. Urine passes from the Kidneys into the Ureters with peristaltic contractions pushing it towards the Urinary Bladder.
Urinary Bladder collects urine from both Ureters and passes it to the Urethra. In a female, it is found anterior to the Uterus. Urinary Bladder is affected during pregnancy especially in the last trimester as Uterus enlargement presses against it making the sense of frequent urgency and frequent urination.
The urethra transports urine from the bladder to the outside of the body for disposal. The Urethra is the only urologic organ that shows the significant anatomic differences between males and females.
The female urethra is shorter, which is more exposed to Urinary Tract Infections (UTIs).
Urine Formation – Functioning of the Urinary System
After food gets completely digested, the liquid slurry enters the large intestine, where further extraction of nutrients happens. An additional function of the large intestine is to absorb out the water resulting in drier fecal matter, which will be excreted via the anal canal.
This absorbed water is reintroduced into circulation, where it picks up metabolic cellular wastes. This precursor of urine then enters the kidneys for filtration and removal of the excess water and waste products.
Filtration of blood occurs in the nephrons of the kidneys starting with tiny capillaries called glomeruli. These glomeruli filter very tiny blood components, excluding large particles out as blood cells, platelets, antibodies, and albumen.
All other solutes, such as ions, amino acids, vitamins, and wastes, are filtered to create a filtrate composition very similar to plasma. The glomeruli create about 200 liters of this filtrate every day, yet you excrete less than two liters of waste you call urine, as 99% of the filtrate is reabsorbed in the tubules.
The glomerulus continues as a highly specialized tubular structure responsible for creating the final urine composition. The filtrated blood passes through glomeruli surrounding with Bowman’s capsule to be collected in the tubules, firstly at proximal convoluted tubules (PCT) where absorption and secretion of electrolytes, glucose, and water occur.
Continuing in the same tubule, the filtered blood passes to the descending and ascending portions of the loop of Henle (U-shaped loop). Then the filtrated blood passes to distal convoluted tubule (DCT), which is shorter than PCT. Absorption and excretion of electrolytes and water occur but to a lower extent.
Finally, the remaining filtrate, which contains 18 Liters of water is collected in collecting ducts, where each duct receives filtrate from several nephrons. In collecting ducts, the final water reabsorption occurs under the effect of the anti-diuretic hormone (ADH). So, the remaining water and electrolytes are concentrated forming urine.