Purification of blood: Lungs help in the purification of blood. Arteries carry pure oxygenated blood from the heart to other parts of the body. ... When breath is inhaled, oxygen from the air comes in contact with the impure blood and the blood takes up oxygen.

The purification of blood takes place in the kidneys.

Introduction:
The kidneys are essential organs responsible for the purification and filtration of blood in our body. They play a crucial role in maintaining homeostasis by removing waste products, excess water, and toxins from the bloodstream. This process is known as urine formation or renal filtration.

Functions of the kidneys:
1. Filtration: The kidneys receive approximately 25% of the cardiac output, ensuring that all the blood in our body passes through them multiple times a day. They filter the blood to remove waste products such as urea, uric acid, and creatinine, as well as excess water and electrolytes. These waste products are then excreted as urine.

2. Reabsorption: After filtration, the kidneys selectively reabsorb essential substances such as glucose, amino acids, and electrolytes back into the bloodstream. This ensures that these vital substances are not lost during urine formation.

3. Secretion: The kidneys also secrete certain substances, such as hydrogen ions and potassium ions, into the urine. This process helps maintain the acid-base balance and electrolyte levels in the body.

Anatomy of the kidneys:
The kidneys are bean-shaped organs located in the abdominal cavity, on either side of the spine. Each kidney is made up of millions of microscopic units called nephrons, which are responsible for the filtration and purification of blood.

Within each nephron, there are several key structures involved in urine formation, including:
- Glomerulus: It is a network of capillaries that filters the blood under high pressure. The glomerulus allows small molecules and waste products to pass through while retaining larger molecules like proteins and blood cells.
- Bowman's capsule: It surrounds the glomerulus and collects the filtered fluid from the blood.
- Renal tubules: These tubules reabsorb essential substances and regulate the concentration of various substances in the urine.

Conclusion:
In conclusion, the kidneys are responsible for the purification of blood in our body. They filter waste products and excess water from the bloodstream, reabsorb essential substances, and regulate electrolyte levels. Understanding the role and anatomy of the kidneys helps us appreciate the importance of these organs in maintaining overall health and wellbeing.

Purification of blood take place in Lungs with the help of Alveoli....