HUMAN TASTE TEST: Taste is the ability to respond to dissolved molecules and ions called tastants, which humans detect via taste receptor cells, which are clustered into taste buds. The tongue has about 10,000 taste buds. When these detect food particles, they send signals to the brain carrying information about their "taste." Each taste bud contains 50-100 taste cells, representing the five taste sensations: salty, sour, sweet, bitter and umami (the response to acidic salts like MSG, often used as a flavor enhancer in Asian dishes, processed meats, and processed cheeses).
Each taste cell has receptors that bond to specific molecules and ions in response to the various taste sensations, connected to a sensory neuron leading back to the brain. So taste -- like all sensations -- resides in the brain. That's the reason different people like different things. Although a single cell may have several types of receptors, one may be more active than the others, so certain tastes will be preferred by that individual. Also, no single taste cell contains receptors for both bitter and sweet tastants.
ABOUT THE TONGUE: The tongue is a versatile group of muscles anchored in the mouth and throat. It is integral to creating articulate speech and other noises. Its top surface is covered by taste buds able to detect the bitter, salty, sour, sweet, and umami (or savory) qualities of food. The tongue, which acts both as a voluntary and involuntary muscle, filters germs and also moves food around within the mouth before transferring it to the esophagus.
ABOUT THE LUNGS: The lungs are located in the chest cavity, and are protected by the rib cage. The lungs are responsible for the exchange of oxygen and carbon dioxide between the body and its surrounding environment. They are made of a spongy, elastic type of tissue filled with tiny holes or bubbles, each surrounded by a fine network of tiny blood vessels. This tissue stretches and contracts as you breathe. The total surface area of the lungs is about the size of a football field.
When you breathe in, the diaphragm and intercostals or chest wall muscles contract, causing the air to travel from your nose and mouth through the windpipe (trachea), then through large and small tubes in the lungs called bronchial tubes. At the end of these tubes are groups of tiny air sacs called alveoli. They have very thin walls filled with small blood vessels called capillaries. Oxygen passes from the air sacs into the blood vessels, and carbon dioxide -- the waste byproduct from the body's metabolism -- passes from the blood into the air sacs. The carbon dioxide is then expelled into the atmosphere when you exhale.