The following points highlight the top ten systems seen in animal body. The systems are: 1. Integumentary System 2. Muscular System 3. Skeletal System 4. Digestive System 5. Respiratory System 6. Excretory System 7. Circulatory System 8. Reproductive System 9. Nervous System 10. Endocrine System.
1. Integumentary System:
The organ involved in this system is skin and its various derivatives, i.e., hairs, scales, feathers, nails, horns and hooves. The primary function of skin is protection, but it performs several other functions.
2. Muscular System:
This is probably the largest system in an animal body which includes muscles. It is concerned with movement, which includes locomotion of the individual and also the movement of different organs, e.g., heart, alimentary canal. The muscles are made up of muscular tissues and connective tissues.
3. Skeletal System:
It is composed of skeleton. When skeleton is present outside the body it is called exoskeleton, e.g., coverings of prawn, insects, molluscs or scales, nails and claws in vertebrates. Among, the invertebrates the exoskeleton is built up of chitin, calcium, etc. This is periodically replaced by a process called moulting.
Among the vertebrates the skeleton is internal and called endoskeleton. It includes bones, cartilages and ligaments. In contrary to exoskeleton this is living, i.e., provided with blood supply and nerves. This system constitutes the framework and support of the individual. Exoskeleton has got nothing in common with endoskeleton except its hardness.
4. Digestive System:
It is responsible for nutrition. Different organs included within this system are teeth, tongue, oesophagus, stomach, intestine, liver and pancreas. They work to take in food (ingestion), to break the complex organic molecules into simpler forms (digestion) and to reject excrementitiously products (egestion).
5. Respiratory System:
This system in one hand ensures the requirement of oxygen in tissues and on the other works to evacuate the carbon dioxide from the tissues. In different animals the organs of respiration differ and following organs are generally found to carry the function of respiration gills, trachea, lungs, skin and lining of the buccal cavity.
6. Excretory System:
Metabolic activities produce waste products. These substances (which are chiefly nitrogenous) together with excess of water are removed from the body by excretory system. Within invertebrates the excretory organs are nephridia, green glands, coxal glands, Malpighian tubules. The excretory organs in vertebrates are known as kidneys.
7. Circulatory System:
For co-ordination, the important requisite is contact between different systems. This is done by circulatory system which includes (A) two sets of circulatory fluids—blood and lymph, (B) vessels for the flow of these fluids, and (C) pumping organ called the heart.
In invertebrates the circulating fluid comes out of the vessels to bathe the tissue space but within vertebrate body blood flows through a closed system of vessels.
The circulation in the former group is of open type and in the latter group it is called the closed type of circulation. This system not only works as porters of the living body but are engaged in defence against foreign invasions.
8. Reproductive System:
Reproduction or multiplication by self-duplication is an important feature of living body. In the multicellular animals organs carrying out this function are known as ovary (in females) and testis (in males).
These organs form specialised cells which pass out through definite tracts. All animals possess specialised structures to assist in bringing these two types of cells closer. Certain glands are often seen to be associated with this system to help in the process of reproduction.
9. Nervous System:
It is made up of a special kind of tissue, namely the nervous tissue. It has the same developmental origin as epidermis. Important organs, like brain and spinal cord perform the functions of response to stimuli and co-ordination of different parts of the body.
These organs are assisted by different peripheral and sympathetic nerves and many organs like eye, ear, tongue, nose and skin work as ports of entry for different stimuli.
10. Endocrine System:
It includes certain glands, e.g., Thyroid, Parathyroid, Pituitary, Adrenal, Thymus, Islets of Langerhans, etc. which pour their secretion directly within blood. The secretion is known as hormone, which acts in a magic way and takes part in the chemical control of the body.
A particular hormone is of same chemical nature in different groups of animals. Only a specific quantity of hormone is required for the proper maintenance of the body. Any deviation in quantity upsets the chemical control of the body and creates abnormality through metabolic dis-balance.