Digestion and respiration

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Oxygen needs to be transported around the body from the lungs to the body cells via the blood vessels because it is needed by the body cells (as are the products of digestion) to carry out the process of aerobic respiration. • Digested nutrients are absorbed into the blood stream surrounding the small intestine and transported to the cells for respiration and energy production. Some cells have a higher-level energy requirement e.g., muscle cells, therefore need more glucose to produce this energy. A combination of oxygen with digested food products enables cells to carry out cell processes for survival. (need to make links to both systems and survival due to cells needing energy). • Respiration is an essential process in the body because it releases energy from the digested food molecules, so that it can be used for other life processes such as movement and growth. Without the circulation of oxygen and delivery of digested food molecules to the body cells, aerobic respiration would be unable to occur, and thus there would be no energy for other essential life processes, such as movement and growth, and the mammal would not survive. The products of digestion are absorbed into capillaries through the walls of microscopic finger-like projections called villi, which line the walls of the intestine. The villi greatly increase the surface area available for the absorption of the products of digestion because each is inter-fused with capillaries, reducing the diffusion distance, thus allowing the process of absorption to occur with increased speed and efficiency. • The digestive system works so that food is broken up into very small molecules. This occurs through the processes of both physical and chemical digestion. Chemical digestion involves the use of biological catalyst or enzymes which, in optimal conditions, break the food molecules down, so they as small as possible. This is important, because they need to be small enough to move through the capillary walls, which are one-cell thick (assimilation maybe mentioned). • The capillaries in the microvilli feed into the hepatic portal vein (HPV). These capillaries have absorbed nutrients from the small intestine. HPV transport nutrient-rich blood where the nutrients are offloaded to the liver for processing before being distributed by the heart to the body cells via a network of arteries and capillaries where the nutrients are used in cellular respiration. • The heart provides the pump to move the blood around the body. The arteries are needed so that blood can be transported. This blood is pumped at a huge volume in the capillaries and microvilli to absorb nutrients. The concentration gradient created in the walls of intestines and the capillaries in the microvilli which allows for effective and efficient absorption of nutrients The heart provides the pump to move the blood around the body. This is required because the products of digestion need to be transported from the intestine to cells around the body that require the product, e.g. glucose needs to be moved to the muscle cells as they have a high energy demand to allow movement. The arteries, capillaries, and veins form a network that can transport materials throughout the body. The arteries are needed so that blood can be transported, with the nutrients, to the body cells from the intestines where digestion occurs, to places in the body that the nutrients are used. In order for this to happen, the arteries direct blood into the much smaller and finer capillaries. These allow the products of digestion, e.g. glucose, to enter the individual cells, where they are used in cellular processes, e.g. respiration, which releases energy for life processes. •

cells blood absorbed respiration energy glucose oxygen energy digested movement growth aerobic energy survive capillaries villi surface area capillaries molecules chemical enzymes capillary thick vein liver pump volume digestion glucose muscle capillaries digestion nutrients capillaries individual cellular