07. Human Nutrition

• State what is meant by the term balanced diet for humans

• Explain how age, gender and activity affect the dietary needs of humans including during pregnancy and whilst breast-feeding

• Describe the effects of malnutrition in relation to starvation, constipation, coronary heart disease, obesity and scurvy

• List the principal sources of, and describe the dietary importance of:

– carbohydrates

– fats

– proteins

– vitamins, limited to C and D

– mineral salts, limited to calcium and iron

– fibre (roughage)

– water

• Explain the causes and effects of vitamin D and iron deficiencies

• Explain the causes and effects of protein-energy malnutrition, e.g. kwashiorkor and marasmus

• Define ingestion as the taking of substances, e.g. food and drink, into the body through the mouth

• Define mechanical digestion as the breakdown of food into smaller pieces without chemical change to the food molecules

• Define chemical digestion as the breakdown of large, insoluble molecules into small, soluble molecules

• Define absorption as the movement of small food molecules and ions through the wall of the intestine into the blood

• Define assimilation as the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells

• Define egestion as the passing out of food that has not been digested or absorbed, as faeces, through the anus

• Describe diarrhoea as the loss of watery faeces

• Outline the treatment of diarrhoea using oral rehydration therapy

• Describe cholera as a disease caused by a bacterium

• Identify the main regions of the alimentary canal and associated organs, limited to mouth, salivary glands, oesophagus, stomach, small intestine (duodenum and ileum), pancreas, liver, gall bladder and large intestine (colon, rectum, anus)

• Describe the functions of the regions of the alimentary canal listed above, in relation to ingestion, digestion, absorption, assimilation and egestion of food

• Explain that the cholera bacterium produces toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of salts from blood

• State the significance of chemical digestion in the alimentary canal in producing small, soluble molecules that can be absorbed

• State the functions of enzymes as follows:

– amylase is secreted into the alimentary canal

– protease breaks down protein to amino acids and breaks down starch to maltose

– lipase breaks down fats to fatty acids and glycerol

– maltose is broken down by maltase to glucose on the membranes of the epithelium lining the small intestine

• State where, in the alimentary canal, amylase, protease and lipase are secreted

• State the functions of the hydrochloric acid in gastric juice, limited to killing bacteria in food and giving an acid pH for enzymes

• Describe the digestion of starch in the alimentary canal:

– amylase breaks down starch to simpler

– maltose is broken down by maltase to glucose on the membranes of the epithelium lining the small intestine

• Describe pepsin and trypsin as two protease protease and lipase are secreted enzymes that function in different parts of the alimentary canal:

– pepsin in the stomach

– trypsin in the small intestine

• Explain the functions of the hydrochloric acid in gastric juice, limited to killing bacteria in food

gastric juice, limited to the low pH:

– denaturing enzymes in harmful microorganisms in food

– giving the optimum pH for pepsin activity

• Outline the role of bile in neutralising the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action

• Outline the role of bile in emulsifying fats to increase the surface area for the chemical digestion of fat to fatty acids and glycerol by lipase

• Identify the small intestine as the region for the absorption of digested food

• State that water is absorbed in both the small intestine and the colon, but that most absorption of water happens in the small intestine

• Explain the significance of villi and microvilli in increasing the internal surface area of the small intestine

• Describe the structure of a villus

• Describe the roles of capillaries and lacteals in villi