The stomach is an organ of digestion. It has a sac like shape and is located between the esophagus and the intestines. Almost every animal has a stomach.

The human stomach is a muscular, elastic, pear-shaped bag, lying crosswise in the abdominal cavity beneath the diaphragm. It changes size and shape according to is position of the body and the amount of food inside. The stomach is about 12 inches (30.5 cm) long and is 6 inches. (15.2 cm) wide at its widest point. The stomach's capacity is about 1 qt (0.94 liters) in an adult.

Food enters the stomach from the esophagus. The connection between the stomach and the esophagus is called the cardiac sphincter. The cardiac sphincter prevents food from passing back to the esophagus. Heart burn is the sensation when stomach juices (gastric juice) is allowed to seep through the sphincter into the esophagus. Once the food enters the stomach, gastric juices are used to break down the food. Some substances are absorbed muscle lining of the stomach. One of the substances the stomach absorbs is alcohol.

The other end of the stomach empties into the duodenum. The duodenum is the first section of the small intestine. The pyloric sphincter separates the stomach from the duodenum.

The stomach is composed of five layers. Starting from the inside and working our way out, the innermost layer is called the mucosa. Stomach acid and digestive juices are made in the mucosa layer. The next layer is called the sub mucosa. The sub mucosa is surrounded by the muscular is a layer of muscle that moves and mixes the stomach contents. The next two layers, the sub serosa and the serosa are the wrapping for the stomach. The serosa is the outermost layer of the stomach.
The stomach is very important role of a body.stomach digest the undigested food & bag like shape .

Human Heart

The human heart is very important role of the human body.The heart is one of the most important organs in the entire human body. It is really nothing more than a pump, composed of muscle which pumps blood throughout the body, beating approximately 72 times per minute of our lives. The heart pumps the blood, which carries all the vital materials which help our bodies function and removes the waste products that we do not need.
The human heart pump blood & distributed of all parts of the body.The human heart is consist of four parts or chambers.The two auricles & the two ventricles.the auricles are called accepter & ventricles are called distributer.There are two veins to collect the deoxygenated blood to the heart.the two veins name is superior vena cava & the other name is inferior vena cava.the superior vena cava collect deoxygenated blood upper parts of the heart & inferior vena cava collect deoxygenated blood lower parts of the heart.
when superior vena cava & inferior vena cava collect deoxygenated blood to to heart & transfer to the right auricles.when heart pump the blood transfer to right auricle to right ventricles through tricuspid valve.when blood transfer to right ventricles then again the heart pump & deoxygenated blood transfer to the lungs through the pulmonary artery & then deoxygenated blood to the lungs & to foam a oxygenated blood & then transfer to the left auricle through pulmonary vein.
The oxygenated blood to the left auricle & again heart pump the oxygenated blood transfer to the left ventricles through mitral valve & again heart pump the oxygenated blood transfer to the aorta & again heart pump transfer oxygenated blood to all parts of the body.the veins is collected the deoxygenated blood to all parts of the body back to the heart with out pulmonary vein .& the artery is collected oxygenated blood to heart to all parts of the body with out pulmonary artery.

Cell

The cell is define as "The cell is a basic structure & function of all living organism "
The first scientist who discovered a cell "robert hooke " in 1665 .He says that the cell mean "little room"
NCBIScience :
Cells are the structural and functional units of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, or have many cells—an estimated 100,000,000,000,000 cells! Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary.

Biology

Biology is a Greek word . bio mean "life"& logy mean "study" the simple biology definition is "the study of life is called biology
The biology is many branches but there are three main branches
Zoology:
The branch of biology which deals with the study of animals is called zoology. zoo mean animals & logy mean study
Botany:
The branch of biology which deals with the study of plants is called botany
Microbiology:
The branch of biology which deals with the study of microscopic organisam e.g ameoba ,virus ,bacteria etc is called microbiology