Introduction to Excretory System
As we know, among many other organ systems in our body, the human excretory system also is a member. It conducts a vital life process that is helping the body to get rid of liquid wastes (solid wastes are generally handled by the digestive system itself). The excretory system collects liquid blood, processes it and then gets it rid of the wastes, i.e. it purifies the blood.
The human excretory system comprises of some organs which are as follows -
The kidneys are the chiefs of the settlement called the human excretory system. The two kidneys are the sites where the main processing of the impure blood takes place and the blood is purified once again. It separates the wastes such as urea and unwanted salts from the impure blood and makes it pure. The wastes segregated are in liquid form and are called urine. The kidney is connected to two ureters (each with one) which are tubes connected with the urinary bladder. Through the ureter, the waste aka the urine is sent to the urinary bladder. The urinary bladder is basically a bag where the urine is stored for a while, until we feel an urge to urinate. Then the urine is parted of the body through an organ called urethra (connected to the urinary bladder).
In the upcoming chapters, the kidney is dealt in more detail.
Kidneys – The Filters in the Human Body
As the title speaks, kidneys are the filters of the human body. Kidneys are in the pair of two. However, a human body can survive with one kidney too because it alone has the ability to handle the filtration work of the whole body.
Kidneys are two bean shaped organs situated at the back of our body just above the waist of the person. The prime function of the kidney is to collect impure blood and purify it and return it back to the rest of the body. The flow of impure blood is constant to the kidney.
The functioning of the kidneys goes like this – The kidneys consist of a number of excretory units called nephrons (also discussed in the latter part of this project), which act as the functional units of the kidneys.
The impure blood is brought to the kidney by an artery called the renal artery. The nephrons inside the kidney are connected to this artery (which divides into capillaries inside the kidneys) and after the impure blood is processed and wastes are segregated, the pure blood is transferred back to the body by the renal veins, which as well are connected to the nephrons from the other end. The wastes thus collected are sent to the urine collecting ducts which open into the ureter. This is how the kidneys function.
Let us now discuss about the functional units of the kidneys, the nephrons in the next chapter.
Nephrons – Functional Units of the Kidneys
Nephrons, as also mentioned earlier are the functional units, which are present inside the kidneys.
The dirty blood containing wastes like urea is brought to the nephrons by the renal artery (divided into capillaries) and it enters the glomerulus (plural glomeruli) which is an intertwined group of capillaries. The glomerulus filters this blood. During filtration, the substances of small molecules present in the blood like amino acids, glucose, salts, urea and excess water present in the blood pass into the Bowman's capsule through the glomerulus, which is extremely thin and permeable. The blood cells and the proteins etc. are left with the blood itself in the glomerulus.
Through the Bowman's capsule, the substances (both useful and harmful) which come out through the glomerulus enter the tubule of the nephron. The useful contents like all the glucose, all amino acids, the useful salts and excess water are reabsorbed back by the help of the capillaries which surround the tubule. However, harmful substances like urea, some unwanted salts and excess water are left in the tubule in the form of liquid. This liquid, which contains those bad substances, is known as urine. Urine is then carried into the urine collecting duct which enters the ureter and then to the urinary bladder and get out of the body through the urethra. This is how the nephrons function.
Dear Gyandeep, please remove the line "In the upcoming chapters, the kidney is dealt in more detail." in the last part of first paragraph.