Kidneys are the most important part of the renal system. Renal system or urinary system is a group of organs concerned with the process of excretion in the body by filtering out excess fluid along with toxins in the form of urine. Urine is a liquid produced by the kidneys and stored in the bladder and finally is excreted through the urethra. The renal system functions along with other systems of the body to perform various tasks apart from excretion such as to help maintain homeostasis and regulate water and salt balance in the blood.
Functions of the Renal System:
Various functions of the renal system are as follows :
- Eliminate waste products of metabolism and other materials from the body which are of no use
- Maintain appropriate fluid volume by regulating the amount of water excreted through urine
- Regulating the electrolyte and acid concentrations in the body
- Maintain the normal pH of the blood
- To control the oxygen level in the body with the help of erythropoietin, a hormone that stimulates bone marrow to produce more oxygen-carrying red blood cells.
- Help maintain a stable internal environment (homeostasis) in the body
The structure of renal system:
All the body parts directly participating in the filtration process fall under the renal system. The renal system comprises mainly of four parts:
- Urinary bladder
Kidneys serve as natural filters for the body. They are a pair of brown coloured, bean-shaped organs almost the size of a human fist 4 to 5 inches long. They are located in the retroperitoneal space (behind the peritoneum) asymmetrically across either side of the spine and are well protected by the rib cage. The right kidney places itself a little lower than the left in order to accommodate the liver. Each kidney weighs about 125-175 g in males and 115-155 g in females. A fibrous capsule composed of dense tissue covers the surface of kidneys to hold their shape.
Each kidney consists of about fifteen lakhs microscopic filters known as nephrons which helps in removing the waste product (urea) from the blood. As a matter of fact, a human body needs only a minimum of 300,000 nephrons to filter blood properly and one kidney is enough to fulfill the purpose.
Kidneys are connected to the aorta by renal artery while renal vein joins it to the inferior vena cava. Blood enters the kidneys through the renal artery for filtration and then the filtered blood is taken to the vena cava through the renal vein. A healthy pair of kidneys have the capacity to filter more than 150 liters of blood throughout the day.
Functions of kidneys:
They are primary functional organs of the renal system keeping us out of harm’s way. They are a multi-functional powerhouse of activities.
The various functions of the kidneys are as listed below :
- To filter blood passing through the nephrons several times a day.
- To remove the waste and toxins from the blood and process it into urine which collects in the pelvis, a funnel-shaped structure, draining down to the bladder through a tube called the ureter.
- To control the body’s fluid balance.
- To regulate the electrolyte levels in the body.
- To regulate the blood pressure constantly by producing a protein called angiotensin
- To reabsorb water, glucose and amino acids and maintain the balance of these molecules in the body.
Ureters are a pair of muscular ducts joining the kidneys to the bladder elongating about 25 cm. They carry toxins and impurities from the kidney to the bladder to be excreted out of the body.
After the blood has been filtered through the kidney, the waste retained by the kidneys is moved down to the bladder through the ureter. It is a sac-like organ with the capacity of carrying 300-400 ml of urine in healthy adults. The expulsion takes place after the storing limit has been reached.
It is a passage that carries urine from the bladder to the external opening. The male urethra is about 15-20 cm long and carries semen along with urine. The urethra in females is shorter however with a length not stretching more than 4 cm. The internal surface of the urethra is lined by stratified columnar epithelium which protects the insides from the toxins and their effect