For performing various physiological functions, such as- digestion, respiration, excretion, reproduction etc. several organs together form the organ systems in the animal body. These are:
Digestive System: This system is associated with ingestion, digestion, absorption of food and removal of undigested residues. The digestive system has two main parts as:
- Digestive Canal: This canal consists of mouth opening, mouth cavity, pharynx, oesophagus, stomach, duodenum, ileum, rectum and anus.
- Digestive Glands: In man salivary glands, liver and Pancreas work as digestive glands.
Respiratory System: This system with the help of oxygen taken from the environment produces energy by the oxidation of food present in the body cells to help the body to do everyday work. In man, the respiratory system consists of nasal aperture, pharynx, larynx, trachea, bronchus, bronchiole and a pair of lungs made of alveoli.
Nervous System: The function of this system is to receive external and internal stimuli of the body and to create the appropriate sensation. Nerve system is formed of brain spinal cord and cranial nerves and spinal nerves. Besides, the nerve system has also a part named Autonomous Nervous system. This part of the nerve system controls the involuntary works of the body.
Excretory System: Due to various physiological metabolic activities some waste materials are produced within the body as by-products. These materials are generally toxic to the body, so they need to be removed. The process of removing unnecessary waste materials from the body is called excretion. The system by which the excretion is performed is called excretory system. The excretory system of human beings consists of a pair of the kidney, a pair of the ureter, one urinary bladder and one urethra.
Reproductive System: Through this system an animal produces one or more offsprings of its type to maintain the continuation of the species. On the maturity, the child becomes capable to reproduce. Man is unisexual. Both males and females have the individual reproductive system of their own. Besides, males have a few more important systems, such as:
- Integumentary System: The membrane covering the body from outside is called integument or skin. This system covers the body, protects from external injury and control the movement of various material from outside and inside the body.
- Endocrine System: There are few endocrine glands within the body of the human beings. Secretions of these glands are known as the hormone. There are no ducts for transportation of hormone. Blood carries the hormone from one place to another. The endocrine system is formed by the endocrine glands like Pituitary, Thyroid, Parathyroid, Islets of Langerhans of Pancreas, and Suprarenal etc.