With this in mind, explain why it is necessary for humans to have a digestive system but unnecessary for plants to have one. The purpose of a digestive system is break large molecules down into a small enough size so that the molecules can cross cell surfaces. This allows nutrients to be abosrobed from the digestive system into the circulatory system and allows nutrients to move out of the circulatory system and into the cells of the tissues. Animals need a digestive system because they are heterotrophs. They get their organic molecuels from other liviing organisms.
Plants are autotrophs.
Therefore, they don't need a digestive system. Discuss two different medically accepted causes and two different treatments of peptic ulcers. The HCL begins breaking apart connective tissue of the ingested food and the pepsin begins digesting protein. An ulcer results when HCL penetrates the mucous layer and begins breaking down the stomach lining. If too much acid is secreted in response to stress, this can lead to an ulcer.