Catabolism and Anabolism are altogether known as metabolism. It is basically all the chemical reactions in a body. Catabolism is the process of breaking down of complex substances while anabolism is building up of complex substances.

Urinary System

kidney place

Kidneys are located in the back of the abdomen. There is a pair of kidneys in every animal and human. The right kidney is a little high than the left kidney. Each kidney is bean shaped and has a depression at its center. From this depression comes out the ureters. These ureters are connected to the bladder. The bladder is a thick muscular bag which collects urine from the ureters. While excreting urine The sphincter muscle, which is found under the bladder, relaxes allowing the urine to flow through the urethra.

Kidney Structure


Kidney is a bean shaped organ.

It has two sections. The outer section under the renal capsule is called the cortex while the section consisting of pyramids is called the medulla.

The inner section connecting to the ureter is called the renal pelvis.

The kidneys have tubes in it called nephrons. The nephrons are connected to the renal pelvis. All of the filtered substances are provided to the renal pelvis by the nephrons. The kidney has a rich number of capillaries present around the nephrons which provide it with water, minerals, and blood plasma. The nephrons have a cup shaped structure called Bowman’s capsule which has blood capillaries in it which are called glomurulus. From here the substances pass through the permeable membranes. The blood platelets and blood cells do not pass through here due to their large size. This process is called ultra-filtration. The substances then travel through the tube. On its ways it passes through a U-turn call the Loop of Henle and then reaches the collecting duct. nephron1_medFrom there the substances reach the renal pelvis.

While the substances move around the tubes of the nephrons lot of the substances including water, minerals and plasma are absorbed back into the blood stream. Here active transport takes place. This process is called selective re-absorption.

This is how the kidneys filter the substances in our body and excretes the waste products.

Waste Products and Excretory organs

The waste products at the end of the process includes the urea, excess water, excess minerals, sweat etc.

These waste products are excreted from the body by a number of excretory organs. The Skin is an excretory organ which excretes sweat. The urethra excretes urine, while the lungs excretes carbon dioxide. The Liver is another excretory organ which excretes bile into the small intestine.


Dialysis is a process in which blood is filtered artificially. When one kidney is damaged a human can still survive but when both kidneys are damaged a human being can die. To filter the blood doctors use the dialysis machine. The doctors inject two tubes, one into the patient’s artery and the other into his vein. Blood dialysisflows from the artery tube and flows into the dialysis machine. The machine contains permeable coiled tubes. There is a dialysis fluid present outside the tube which contains lots of salt. It flows on the opposite direction than the blood to keep a stable concentration of salts and water. If there is lower concentration of any substance or higher concentration then diffusion will take place according to the diffusion gradient.









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