Passage 2 (Questions 6 - 10)The human digestive tract is fundamentally a long tube running through the body, with dedicated sections that are capable of digesting material put in at the proximal end, extracting any useful components from it, then expelling the waste products at the distal end.The small intestine is the site where most chemical digestion is carried out, and where virtually all the absorption of useful materials occurs. The intestines also have a smooth muscle wall with two layers of muscle, which enables the generation of rhythmic contractions that force products of digestion through the intestine. To allow for absorption and secretion, specialized zones known as macula communicans exist between the muscle cells. These directly connect the cytoplasm of two cells, which allows various molecules and ions to pass freely between them.In the large intestine, these connections allow for the movement of ions and fluids. For example, if waste is too solid, it cannot move fluidly and can result in blockage. To prevent this, Cl- ions can be secreted into the lumen. Cations and water will follow the chloride into the lumen by passing through intercellular spaces. This method of transport contrasts typical transcellular transport, where substances travel through the cell membrane.Diseases of the intestines are often due to chronic inflammation, which can arise from imbalances in the regulation of fluids and solute movement. Elevated levels of enzymes like thymidine kinase are often used to predict the risk of colon cancer. Question 10The muscle of the dual-layered system described in the passage is: A.striated.B.multinucleated.C.regulated by the parasympathetic nervous system.D.innervated by the somatic nervous system.