Urinary System

 Urinary System in Human Beings

Human Excretory System

The human body has specialized organs for the removal of waste products from the body. These organs include lungs and kidneys. The major waste products produced by humans are carbon dioxide urea and undigested food particles. The decomposition of unused protein in the liver results in the production of urea and the oxidation of food during respiration results in the production of carbon dioxide. When these waste materials get accumulated in the body, they become poisonous and harmful. Thus, our lungs excrete carbon dioxide and our kidneys excrete urea.

Sectional View of a Kidney

Kidneys

These are reddish-brown, bean shaped structures lying towards the back of our body above the waist on either side of the vertebral column. The left kidney lies higher than the right kidney. The blood in our body constantly passes through our kidneys. The dirty blood from aorta enters into kidneys through renal artery and the clean blood is carried away from kidneys by the renal veins. Thus, the renal artery brings deoxygenated blood from which waste products are removed. The function of kidneys is to remove the waste products and form of yellowish liquid called urine.

Ureter

These are a pair of whitish, narrow tubes, which open from both the kidneys to urinary bladder. In other words, ureter connects kidneys to the urinary bladder.

Urinary Bladder

It is a bag which stores urine for some time.

Urethra

It is a tube through which the urine is passed out from the body. The opening of urinary bladder into urethra is guarded by muscle called sphincter muscle.

Nephron

Internally, a kidney is made up of numerous, microscopic units called nephrons. Nephron is the structural and functional unit of excretion. Each kidney has millions of nephrons.

Structure of Nephron

Each nephron has a cup-shaped cavity called the Bowman's Capsule, at its upper end. The lower end of the Bowman's capsule is a tube called the tubule. The tubule is connected to the Bowman's capsule there at one end while the other end is connected to the urine collecting duct of the kidney. Within the Bowman's capsule there is a bundle of blood capillaries called the glomerulus. One end of the flomerulus is attached to the renal artery which brings the dirty blood containing urea into it. The other end of the glomerulus exits the Bowman's capsule in the form of a blood capillary, surrounds the tubule of the nephron and finally joins the renal vein, supplying it with urea free blood.