The gi tract wall has a specific organization of layers associated with it. the smooth muscle cells of the produce peristalsis to assist in the physical breakdown of foodstuff and to propel foodstuff from one portion of the tract to the next.

The smooth muscle cells of the mascularis externa produce peristalsis to assist in the physical breakdown of foodstuff and to propel foodstuff from one portion of the tract to the next.

The gastrointestinal tract consists of the mouth, oesophagus, stomach, small and large intestines, anus. The smooth muscles of the oesophagus, stomach, small intestine and the large intestine contract in a sequence producing a perstaltic wave called the peristalsis.

The cells of the muscularis externa are responsible for the movement of the food from one portion of the GI tract to the other by the process of peristalsis. They help in the movement and the churning of the food. The muscularis externa consists of a inner circular layer and a longitudinal outer muscular layer. The inner layer prevents the food from travelling back and the outer layer shortens the tract and the coordination of both results in the peristalsis.

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."