INTRODUCTION

PHYSIOLOGY
Physiology is the science of life. It is a broad science which aims to understand the mechanisms of living, from the molecular basis of cell function to the integrated behaviour of the whole body. Reference http://www.understanding-life.org Physiology is the branch of biology that deals with the normal functions of living organisms and their parts.
Organ system
Organ system is a group of organs that work together to perform a certain task or complex function.
We have 10 (Ten) major organ systems of the body and they are listed below, along with several organs that are associated with each system.
Circulatory System

The circulatory system is the body's transport system. It is made up of a group of organs that transport blood throughout the body. The heart pumps the blood and the arteries and veins transport it. Oxygen-rich blood leaves the left side of the heart and enters the biggest artery, called the aorta. The aorta branches into smaller arteries, which then branch into even smaller vessels that travel all over the body. When blood enters the smallest blood vessels, which are called capillaries, and are found in body tissue, it gives nutrients and oxygen to the cells and takes in carbon dioxide, water, and waste. The blood, which no longer contains oxygen and nutrients, then goes back to the heart through veins. Veins carry waste products away from cells and bring blood back to the heart , which pumps it to the lungs to pick up oxygen and eliminate waste carbon dioxide.
Reference – thefactmonster.com and http://en.wiki.org

Diagram of the Heart( Reference http://commons.wikimedia.org)
Digestive System
The Digestive system consists of oral cavity, esophagus, stomach, liver, gallbladder, pancreas, small and large intestine, and rectum.
The digestive system is made up of organs that break down food into protein, vitamins, minerals, carbohydrates, and fats, which the body needs for energy, growth, and repair. After food is chewed and swallowed, it goes down the esophagus and enters the stomach, where it is further broken down by powerful stomach acids. From the stomach the food travels into the small intestine. This is where your food is broken down into nutrients that can enter the bloodstream through tiny hair-like projections. The excess food that the body doesn't need or can't digest is turned into waste and is eliminated from the body.
Reference – thefactmonster.com and http://en.wiki.org

Human Digestive System Diagram (Reference healthfavo.com)
Endocrine System
The endocrine system is a widespread group of glands and organs that acts as the body's control system for producing, storing, and secreting chemical substances called hormones.
The endocrine system is made up of a group of glands that produce the body's long-distance messengers, or hormones. Hormones are chemicals that control body functions, such as metabolism, growth, and sexual development. The glands, which include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, thymus gland, pineal body, pancreas, ovaries, and testes, release hormones directly into the bloodstream, which transports the hormones to organs and tissues throughout the body.

Thyroid gland
The thyroid gland is composed of two sections in front of the windpipe and below the voice box. It produces two hormones, thyroxine (T4) and tri-iodothyronine (T3), which together are called the thyroid hormones. They help regulate growth and development and help in childhood brain development. The thyroid also contains cells that produce the hormone calcitonin, which helps to maintain normal calciumlevels in the blood.
Reference – thefactmonster.com and http://en.wiki.org

Diagram of the immune System (Reference http://commonsensehealth.com)

Immune System
The immune system is our body's defense system against infections and diseases. Organs, tissues, cells, and cell products work together to