Unit 7 Human Nutrition and the Digestive System Presentation Notes PDF

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Unit 7 Human Nutrition and the Digestive System QUESTION 1 Please go to https://youtu.be/fnWWWTpq83I to view my presentation.

Presentation Notes/Script Slide 1 The digestive tract is made up of a series of structures and organs which food and liquid travel through to be absorbed and distributed for use around the body. Starting at the lips, the digestive tract consists of the oral cavity, the pharynx, the oesophagus, the stomach, the small intestine, the large intestine, and the anus. Food is prepared for its journey through the digestive tract by a mechanical process called mastication or chewing, taking place in the mouth. Inside the oral cavity, the canines and premolars cut and tear up the food. The molars at the back then crush and grind up the food. The tongue, in conjunction with the cheeks, guide the food around the vestibule between upper and lower teeth, using salvia to mould the food into a ball shape, called a bolus. Sympathetic and parasympathetic nervous systems supply a constant flow of saliva to the mouth, even when food is not present. Enzymes called lysozyme and amylase are found within the secretions of the membranes which line the oral cavity and salivary glands. These help to soften the food so the digestion process can begin after swallowing. Amylase uses a process called enzymatic hydrolysis which dissolves food and lysozyme can dissolve certain bacteria. Rogers, (2011). Once swallowed, the bolus is forced into and down the pharynx by a series of peristaltic contractions. These transport the bolus through the oesophagus to where it enters the stomach through the lower oesophageal sphincter. Slide 2 Inside the hollow muscular organ of the stomach, the bolus is churned and becomes a semiliquid mass known as chyme. The chyme is mixed with highly acidic, enzyme rich gastric juices and further digested so the particles become more soluble and can move into the small intestine. The gastric juices contain hydrochloric acid; to aid digestion and destroy bacteria, water, mineral salts, enzymes and intrinsic factor; to allow absorption of vitamin B. Bile, in particular, is used to neutralise the acid in the stomach. The chyme is then passed through to the small intestine gradually as parts become ready for further digestion. The lower digestive tract houses the small intestine and the large intestine, or colon. Inside the first section of the small intestine, the duodenum, the chyme stimulates the pancreas to release a fluid mixture of pancreatic juice and bile. The bile is used to breakdown fat globules, providing a larger surface area for the enzymes pancreatic lipase to digest fats into fatty acids and glycerol. This is called emulsification. Sucrase, lactase and maltase are secreted through the lining of the small intestine and the chyme is continually moved through the jejunum and ileum, reduced in size and composition until it can be absorbed by the intestinal wall for transportation through the bloodstream. Segmenting contractions of the smooth muscle intestine wall occur in an irregular manner to move the contents through the digestive tract. The walls of the small intestine are covered with tiny mucosa villi which increase the surface area allowing for better absorption of vital nutrients. Food material that cannot be absorbed is passed into the large intestine where bacteria break it down and other waste products are picked up. The primary functions of the large intestine

are to absorb water and store faecal matter. Once all of the nutrients and most of the water have been absorbed from the chyme, the non-digestible waste material is compacted and pushed through to the end of the large intestine to the sigmoid colon, or rectum, where it is stored as faecal matter for excretion from the body via the anal canal opening. Rogers, (2011). Slide 3 Enzymes are released into multiple organs along the alimentary canal. For example, salivary amylase is secreted from the salivary glands and pepsin and gastric lipase are secreted from the gastric glands. Enzymes catalyse reactions inside cells so their life supporting processes can be carried out efficiently. For the digestive system these are to breakdown macronutrient food molecules and speed up the digestive process. The internal environment of the digestive system must have a suitable pH level for this catalytic reaction to happen. The optimal temperature for enzymes found in humans is body temperature, around 37°C. The optimal pH conditions for each enzyme are shown in this table. The enzymes that operate best in acidic conditions are those which enter the stomach, for example, gastric lipase and pepsin. Once enzyme rich chyme leaves the stomach it enters the duodenum, and the acidic content is neutralised by alkali bile. Then we see enzymes such as trypsin and pancreatic amylase and lipase secreted from the pancreas into the duodenum. These enzymes operate best in alkaline conditions. Each enzyme molecule has an active site which allows it to bond with specific substrates. The active site has a geometrical shape and particular chemical signals which will only allow the specific substrate to bond with its complementary shape. When the substrate attaches to the enzyme’s active site, an enzyme-substrate complex is formed. Inside the complex a reaction takes place to create a product, depending on which enzymes and substrates bond together. Once the end product is released, it can be transported and stored, leaving the active site clear for the process to start over again. Slide 4 Chemical digestion is the process of digestion where large molecules are broken into smaller molecules using the enzymes, carbohydrase, protease and lipase. Amylase is a carbohydrase which is produced in the mouth and pancreas then secreted into the alimentary canal. The purpose of amylase is to digest starch to maltose. Maltose is then digested by maltase into glucose on the lining of the small intestine. Proteases, such as pepsin and trypsin, break down proteins into amino acids. Pepsin is produced when protein is digested in the stomach and trypsin is produced in the pancreas to be secreted into the duodenum with lipase enzymes. Lipase enzymes digest lipids into fatty acids and glycerol. Mechanical digestion, or catabolism, is the physical breakdown of large food structures into smaller food structures. Mostly, this takes place in the mouth before the bolus travels through the digestive system and the chemical digestion process takes place. Both mechanical and chemical digestive processes exist to breakdown food molecules and increase the surface area to allow nutrients to be absorbed effectively. Slide 5 In 2016, the Department of Health released the latest copy of the Eatwell Guide to show a healthy balanced diet and lifestyle for the average adult in the UK. It is suggested that the ideal balanced diet to provide good health and prevent disease would contain both macronutrients; carbohydrates, protein and fat, and micronutrients; vitamins and minerals.

The base of the food pyramid shows the foods that should dominate our meals, which are all sources of carbohydrates. Carbohydrates are essential macronutrients which must be ingested. Macronutrients found in starchy foods, such as these, increase energy and strength for physical exercise, produce heat within the body, build muscle and help improve concentration and stamina. Unrefined complex carbohydrate variations such as wholemeal bread and whole grain rice are recommended for maximum nutrient benefit. The next food group shown is Group 3; fruit and vegetables. Fruit and vegetables are also carbohydrates but contain a number of nutrients, antioxidants, fibre and have a high-water content. As the main source of micronutrients, fruit and vegetables should make up the next biggest portion of our meals. Micronutrients are essential in a balanced diet, even though they do not provide energy or calorific value, as they are used in the digestion of proteins, carbohydrates and fats. Towards the top of the pyramid are Group 1; meat, fish and alternatives, and Group 4; dairy and alternatives. These are sources of protein. Most of the products in Group 1 are animal products, but there are some plant-based protein sources such as beans and pulses, which also provide dietary fibre. Protein is a macronutrient which contains amino acids and is essential for metabolism and muscle development. There are 20 amino acids required by the body, 9 of which must be ingested as food as the human body cannot manufacture them. Foods in Group 4 provide a source of calcium, protein, vitamins and minerals and, therefore, should be consumed daily. Calcium is a micronutrient mineral, along with chloride, magnesium, sodium, sulphur, potassium and phosphorus. At the top of the pyramid, is Group 5; oils and spreads, which should take up only a small portion of our daily intake of calories as they are often high in saturated fat. However, fats are essential to a balanced diet. The best ingredients to consume would be avocados, nuts and/or olive oil, which contain unsaturated fats.

References Rogers, K., (2011). The Digestive System. [ebook] Britannica Digital Learning. Available at: https://www.perlego.com/book/1639264/the-digestive-system-pdf (Accessed on 03/02/2021)

QUESTION 2 1. Michaels BMI is 30.9 which puts him in the obese category for his age and height. NHS, (2018). The data for Michael’s typical day show that he is consuming over 2700 kilocalories per day, 200 kilocalories per day over the recommended amount for men. NHS, (2019). Almost half of Michaels daily intake (1359 kilocalories) is coming from fat, which is an excessively high amount and puts him at risks of developing atherosclerosis. Looking at his fibre intake, we can assume Michael is not eating enough fruit and vegetables suggesting he may be suffering from nutrient deficiencies. At his current weight and with this high fat diet, Michael is at risk of developing chronic heart disease, type 2 diabetes, cancer and high blood pressure. Vitamin B12, vitamin D, vitamin E and magnesium deficiencies have all been linked to diabetes, in particular. To decrease the risk of developing any of these conditions, Michael should increase the number of fresh fruits and vegetables in his diet and lower his intake of fatty foods. Incorporating healthy protein sources is also vital to achieve a balanced diet, also helping him to feel fuller for longer. To boost his vitamin B12 levels, Michael should consume moderate amounts of fish, meat and eggs. To increase his vitamin E levels, Michael should

use vegetable oils in cooking, and add leafy green vegetables to salads. Almonds, peanut butter and spinach are great sources of magnesium, so he should consume these also. Adopting a balanced diet, with these ingredients in particular, would help Michael to lose weight, increase his energy and decrease his chances of developing diabetes. An increase in energy may encourage him to exercise more, although he has an injury, he could opt for low impact exercise such as walking. Walking for a minimum of 30 minutes daily could burn in excess of 90 calories per day, or 630 calories per week. Makofsky, (2019). Getting outside would also increase Michaels vitamin D levels. 2. Stephanie’s BMI is 18.7 which puts her in the underweight category for her age and height. NHS, (2018). It is likely Stephanie’s ovulation cycle is affected by her low level of body fat. Oestrogen is produced in fat cells and low levels of oestrogen may stop the ovaries from releasing an egg, which means there would be nothing for the sperm to fertilise. As a healthy weight for Stephanie would be between 107.8lbs and 145.1lbs, we can assume that Stephanie is not meeting her recommended caloric intake of 2000 calories for women and she is likely severely undernourished. NHS, (2019). To increase her chances of conceiving and to help her reach a healthy weight, Stephanie should aim to eat at least 2000 calories per day, including a variety of fruit and vegetables, starchy carbohydrates; such as pasta and rice, and a healthy source of protein; such as lean meats, beans and pulses. It is recommended that women who are trying to conceive take a vitamin supplement with added folic acid. Stephanie is also diagnosed with anaemia. Iron deficiency anaemia is caused by a lack of iron, symptoms include tiredness and shortness of breath. Stephanie should make sure that she takes a supplement which contains iron to treat this, but she could also eat beef, eggs, brown rice, chickpeas, apricots or quinoa, which are great sources of iron. 3. Imran’s symptoms suggest he has Rickets or is developing this disease. Rickets affects the bone development in children and is caused by a lack of vitamin D or calcium. It is vital that Imran improves his diet and spends more time outside. In particular, he can increase his calcium levels by eating more dairy products such as cheese, milk and yoghurt. Tofu and canned fish also contain around 200mg of calcium per portion. Various fish contain vitamin D as well so these would be fantastic for Imran. The NHS has a resource named “Live Well” which provides parents with vital information and suggestions to help children achieve a healthy balanced diet and lifestyle. NHS, (2019). Imran’s mother could show Imran this website to help him understand how he will need to change his diet and spend more time outside. Imran should be introduced to active games he could play with his sister, once he has recovered. Getting more time outside will help Imran to get more vitamin D, coupled with the supplement provided by the doctor. The key to improve Imran’s health will be a change in diet. He will need at least 2500 kilocalories per day from fresh fruit and vegetables, carbohydrates such as pasta and rice and healthy protein sources such as lean meats, beans and pulses. His calcium intake should be at least 2000mg per day. References Makofsky, N, “How Many Calories…”, (2019), Available at https://www.livestrong.com/article/414178-how-many-calories-will-i-burn-walking-briskly-for-30minutes-a-day-7-days-a-week/ (Accessed 04/02/2021) NHS, “BMI healthy weight calculator”, (2018), Available at https://www.nhs.uk/live-well/healthyweight/bmi-calculator/ (Accessed 04/02/2021)

NHS, “Physical activity guidelines for children and young people”, (2019), Available at https://www.nhs.uk/live-well/exercise/physical-activity-guidelines-children-and-young-people/ (Accessed 04/02/2021) NHS, “What should my daily intake of calories be?”, (2019), Available at https://www.nhs.uk/common-health-questions/food-and-diet/what-should-my-daily-intake-ofcalories-be/ (Accessed 04/02/2021)

QUESTION 3 Method Weight and height measurement

Description Uses a simple graph to establish if a person is a suitable weight for their height.

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Physical measurement: Callipers

Hydrostatic weighing

Measures underlying fat by pinching areas of the skin.

Used to measure body fat by submerging the person underwater.

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Strengths Can be used in own home with no assistance. Simple to use, takes less than 2 minutes to calculate. Aids weight management with regular use to measure progress. Highlights specific problem areas. Aids weight management with regular use to measure progress. Highly accurate. Safe test with no side effects.

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Limitations Not suitable for adults with a muscular build. Cannot identify specific problem areas.

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Requires assistance for most accurate results.

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Not widely available. Cannot highlight specific problem areas. Not often free, costing around £40 per assessment. Not suitable for the elderly or children. Some people may find the assessment uncomfortable.

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Accuracy Low accuracy.

More accurate than weight and height measurements but less accurate than hydrostatic weighing. Highly accurate with a margin of error of approximately 2%....