What Is The Digestive System?

    Published: 06-16-2009
    Views: 11,497
    Science expert Emerald Robinson explains what the Digestive system is.

    Emerald Robinson: Hi! I am Emerald Robinson and in this What is? Video, we discuss the human bodys digestive system. The digestive system is the organ system that physically and chemically breaks down food, so that nutrients can be observed into the blood stream for use by the body cells.

    Organs like the liver and pancreas are important to the digestive system, but are not technically part of it. The digestive system is really a tube about 30 feet in length that extends from the mouth where food is ingested to the anus where waste is eliminated. Digestion begins in the mouth.

    Our teeth grind and mash food into smaller pieces; while saliva produced by the glands under the tongue starts to bio-chemically break down the carbohydrates. When we swallow, our tongue pushes a ball of food called a bolus in to the esophagus, the tube that leads to our stomach.

    The esophagus uses a series of wavelike muscle contractions called peristalsis to move the food forward. Once the bolus reaches our stomach its mixed with chemicals like gastric acid and pepsin which kill any microorganisms that might be present in the food and break protein down into smaller units. The stomachs muscular walls churn the food which is now a thick fluid called chyme and propel it into the first part of the small intestine, the duodenum.

    In the duodenum the chyme mixes with several bio-chemicals that break down fats, neutralize stomach acid and continue to chemically break down food into molecular particles. As the chyme is transported through the remaining parts of the small intestine, the jejunum and the ileum nutrients are absorbed into the blood stream through many fingers like projections called villi. The remaining material passes into the large intestine where bacteria ferments the remaining nutrient preparing them for absorption. The large intestine also absorbs water and forms solid waste where it is held until it is expelled.