Discovery Science: Human – Metabolism and Hormones – Digestion

Earth Science: Human – Metabolism and Hormones – Digestion

The utilization of food mainly takes place in the small intestine. The required nutrients are then distributed through the body. Nutrition should be as varied as possible in order to assure an optimal supply of all “fuels.”

After nutrients from the stomach have entered the small intestine, the breakdown of relatively large food molecules into smaller units continues. This takes place principally under the influence of various enzymes that break up proteins, fats, nucleic acids, and large sugar molecules such as starch into smaller building blocks.

These nutrients leave the small intestine and are resorbed into the bloodstream, which enables the body to utilize them as energy suppliers for body functions. To facilitate this the wall of the small intestine consists of numerous intestinal villi, which enlarge the surface area of the small intestine to about 2,152 square feet (200 m2).

In each intestinal villus there is a network of tiny blood vessels as well as a central lymph vessel. Amino acids and small sugar molecules enter the small blood vessels, which join into a portal vein that transports the nutrients from the intestine to the liver.

Fats are broken down into glycerin and fatty acids, which are sur- rounded by special proteins. As tiny balls they then enter the lymph vessel from where they than reach the bloodstream.

Function of large intestine

The 4.2-foot (1.3-m)-long large intestine follows the small intestine. The remaining material yet to be digested from the digestive tract moves through the large intestine in about 12 to 24 hours.

During this process the material becomes firmer, since water given off into the digestive tract, as a base substance in various digestive juices, is now being removed again. In total about 99 percent of the water added during the digestive process is resorbed by the small and large intestine.

The rest is excreted as feces.

Essential nutrients

In addition to the “fuels” (such as fats, carbohydrates, proteins) required by the human body for conversion into energy and as raw material for many biosynthetic processes, there are also a number of important nutrients that must be provided in completed form.

These include some amino acids, vitamins, trace elements (for example, potassium and phosphorous), and fatty acids, such as linolenic acid. If these nutrients are not provided to the body in sufficient quantities, malnutrition can occur which can cause dangerous physical and mental effects.


Probiotic yogurts belong to a new generation of food products, sometimes called ‘functional food these products are supple merited with ingredients that are claimed to have health benefits.

Probiotics are microorgamisms that improve the natural intestinal flora and strengthen the immune system Probiotics should not. however, be confused with medications.


DIABETES affects over 180 million people worldwide. It disrupts the absorption of sugar from the bloodstream—a process normally carried out by insulin produced in the pancreas.

Diabetes can be controlled by diet, oral medication, or self administered injections of artificial insulin.