ANIMAL NUTRITION YEAR 10 CHAPTER 7 Animals get their food from other organisms – from plants or other animals. They cannot make their own food as plants do. The food an animal eats every day is called a diet. Most animals need 7 types of nutrients in their diet. A diet with correct proportions of nutrients is called a balanced diet. They are: carbohydrates proteins minerals fats water vitamins fibres ENERGY NEEDS Different types of people uses different amounts of energy which is according their sex, age, or occupation. Energy used is from the amounts of food consumed. Too much food will result the extra energy to be stored as fat and too little food would not give enough energy and makes you tired. A person’s diet changes at different times in their life. For example when a pregnant woman will need more energy for her and her baby. When we grow old, we need less energy as our metabolism will slow down at that age. NUTRIENTS Food gives you energy and other benefits as well. To eat a balanced diet, the diet must contain carbohydrate, fat and protein. You will also need each kind of vitamin and mineral, fibre and water. These substances are called nutrients. The diet has to contain all of these nutrients for the body to work properly. VITAMINS Vitamins are organic substances which are only needed in tiny amounts. If you do not have enough of a vitamin, you might get a deficiency disease. MINERALS Minerals are inorganic substances that we need to eat in just small amounts. FIBRE Fibre helps keep the alimentary canal working properly. Food moves in the alimentary canal because the muscles contract and relax to squeeze it along. This is called peristalsis. The muscles work strongly when there is harder, less digestable food like fibre in the alimentary canal. This helps prevent constipation. VITAMINS VITAMIN FOODS THAT CONTAIN IT WHY IT IS NEEDED To make stretchy protein collagen, found in skin and other tissues; keep tissues in god repair DEFIECIENCY DISEASE C Citrus fruits such as oranges, limes, raw vegetables Scurvy, which causes pain in the joints and muscles; and bleeding from gum and other places; this used to be a common disease for sailors who had no fresh vegetables D Butter, egg yolk, and it can be Helps calcium to be absorbed, Rickets. In which the bones become soft and made by the skin when for making bones and teeth deformed; this disease was common in young sunlight falls on it children in industrial areas who rarely got into the sunshine MINERALS MINERAL ELEMENT FOODS THAT CONTAIN IT WHY IT IS NEEDED DEFICIENCY DISEASE Calcium, Ca Milk and other dairy products, bread For bone and teeth,; for blood clotting Brittle bones and teeth; Poor blood clott8ig Iron, Fe Liver, red meat, egg yolk, dark green vegetables For making haemoglobin, the red pigment in blood which carries oxygen Anaemia, in which there are not enough red blood cells so the tissues do not get enough oxygen delivered to them FAT AND HEART DISEASE The fat found in animal foods is saturated fat. These foods contain cholesterol. Eating this type of fat will likely to get heart disease. This is due to the fat deposits build up inside arteries, making them stiffer and narrower. If this happens in the arteries supplying the blood to the heart, not enough blood can get through. The heart muscles will run short of oxygen and cannot work properly. This is called coronary heart disease. The deposits causes a blood clot that result in a heart attack. Examples of foods with saturated fats is dairy products like milk, cram, butter and cheese,. Unsaturated fats are better and they are vegetable oil and fish oil. OBESITY People who take in more energy than they use up get fat. Having so much fat is called obesity. Obese people are more likely to get heart disease, strokes and diabetes. The extra weight placed on the knees can cause problems with the joints, especially the knees. To control weight, this can be achieved by eating a normal, well-balanced diet and taking regular exercise. STARVATION AND MALNUTRITION In some parts of Africa, several years of drought leads to not enough harvest that would not provide enough food to feed all the people. Despite help from other countries, many people have died from starvation. Even if there is enough food, they may suffer from malnutrition. Malnutrition is caused by not eating a balanced diet. Example form of malnutrition is kwashiorkor caused by a lack of protein in the diet. This is most common among children. Kwashiorkor is caused by poverty due to having not much high-protein foods. The most severe forms of malnutrition is from the lack of energy and protein from the diet. Severe shortage of energy in the diet causes marasmus. MARASMUS AND KWASHIORKOR The alimentary canal of a mammal is a long tube running from one end of its body to the other. For food to be used, it must first go through the alimentary canal and into the bloodstream. This is called absorption. The molecules have to be small to be absorbed through the walls of the alimentary canal. These molecules of carbohydrate, protein and fat must be broken down to become smaller molecules. This is called digestion. Large molecules like polysaccharides are broken down into simple sugars and proteins into amino acids. These very small molecules are then absorbed and do not need to be digested. MECHANICAL AND CHEMICAL DIGESTION An animal first eats in quite large pieces. These pieces of food is broken up by teeth and by churning movements of the alimentary canal. This is called mechanical digestion. Other pieces of food have been ground up, the large molecules present are then broken down into small ones. This is called chemical digestion. It involves a chemical change from one sort of molecule to another. PROTEINS FATS CARBOHYDRATES Teeth break down large pieces of food into smaller ones Teeth break down large pieces of food into smaller ones Teeth break down large pieces of food into smaller ones Bile salts break down large pieces of food into smaller ones Water in digestive juices dissolves some food. Water in digestive juices dissolves some food Proteases break down protein molecules into polypeptide molecules Amylase breaks starch molecules down to maltose molecules Peptides break down polypeptides into amino acids Maltase breaks maltose into glucose Lipase breaks down fat molecules to fatty acid and glycerol molecules glycerol Fatty acids Amino acid glucose Teeth helps with the ingestion and mechanical digestion of the food we eat. Teeth can be used to bite off pieces of food. They chop, crush or grind them into smaller pieces. This gives the food a larger surface area, which makes it easier for enzymes to work on. It also helps soluble foods to dissolve. NAME ROOT DESCRIPTION AND FUNCTION The part of tooth that is embedded in the gum CROWN The part where the tooth can be seen. It is covered with enamel. ENAMEL The hardest substance made by animals. Difficult to break or chip it. It can be dissolve by acids. DENTINE It is like bone and is quite hard but not as hard as enamel. It has channels in it which contain living cytoplasm. PULP CAVITY In the middle of the tooth. It contains nerves and blood vessels. These supply the cytoplasm in the dentine with food and oxygen. CEMENT This covers the root of the tooth. It has fibres growing out of it. These attach the tooth to the jawbone, but allow it to move slightly when biting or chewing. TEETH INCISORS CANINES PREMOLARS MOLARS In front of the mouth At the side of the incisors At the back of the mouth At the back of the mouth Features Sharp-edged, chiseled shaped Pointed teeth Wide surfaces Wide surface Function Biting pieces of food Tearing out pieces of food Grinding food Chewing food What does it look like Position in the mouth TYPES OF TEETH Mammals differ from other animals by having two sets of teeth. The first set is called the milk teeth or deciduous teeth. In humans, these starts to grow through the gum, about one or two at a time, when a child is about five months old. The first set of teeth begins to fall out when the human is about 7 years old. 20 teeth to replace the teeth that fell out plus 12 new teeth, which makes up a complete set of permanent teeth. DENTAL DECAY Tooth decay and gum disease are common problems. Both are caused by bacteria. There are lots of bacteria living inside the mouth. Some of the bacteria takes substances from saliva to form a sticky film over the teeth, especially next to the gums and in between the teeth. This is called plaque. Plaque is soft and easy to remove at first, but if it is left it hardens to form tartar, which cannot be removed. DENTAL DECAY GUM DISEASE If the plaque is not removed, the bacteria in it may infect the gums. The gums swell, become inflamed, and may bleed when brushing teeth. This is usually painless, but if the bacteria is allowed to spread they might work down around the root of the tooth. The tooth becomes loose and needs removing. DENTAL DECAY TOOTH DECAY If the sugar is left on the teeth, bacteria in the plaque will feed on it. They use it in respiration, changing it into acid. The acid gradually dissolves the enamel covering the tooth and works its way into the dentine. The dentine is dissolved away more rapidly than the enamel. If this lets on, the tooth will have to be taken out. Avoid tooth decay by eating less sugary foods and use fluoride toothpaste regularly. Drinking water also make your teeth more resistant to decay. Trips to the dentist is also important to prevent dental problems. The alimentary canal is a long tube that runs from the mouth to the anus. It is part of the digestive system that also includes liver and pancreas. The wall of the alimentary canal contains muscles, which contract and relax to make food move along. This movement is called peristalsis. Special muscles can close the tube in certain places that are called sphincter muscles. To help the food to slide along easily, it is lubricated with mucus. Mucus is made in the goblet cells which occur along the alimentary canal. Each section of the alimentary canal has its own part to play in ingestion, absorption and egestion. THE MOUTH Food is ingested using the teeth, lips and tongue. The teeth then bite or grind the food into smaller pieces, increasing its surface area. The tongue mixes with saliva, forms it into a bolus. The bolus is then swallowed. Saliva is made in the salivary glands. It is a mixture of water, mucus and enzyme amylase. • Water Dissolves substances in the food, allowing us to taste the food. • Mucus Helps the chewed food to bind together to form a bolus, lubricates it so that it slides down easily into the oesophagus when it is swallowed. • Amylase digest starch in the food into the sugar maltose. There are 2 tubes leading down from the back of the mouth. The one in front is the trachea or windpipe, which takes air down to the lungs. Behind the trachea is the oesophagus that takes food down to the stomach. When you swallow, a piece of cartilage covers the entrance to the trachea. It is called the epiglottis, and it stops food from going down into the lungs. The entrance to the stomach from the oesophagus is guarded by a ring of muscle called a sphincter. This muscle relaxes to let the food pass into the stomach. The stomach has strong, muscular wall. The muscles contract and relax to churn the food and mix it with the enzymes and the mucus. The mixture is called a chyme. The stomach wall contains goblet cells that secretes mucus. It also contains other cells which produce protease and other enzymes to make hydrochloric acid. These are situated in the pits of the stomach wall. The main protease enzyme is pepsin. It digests proteins by breaking down into polypeptides. Pepsin works best in acid conditions. The acid also helps to kill any bacteria in the food. Renin is only produced in the stomach of young mammals. It causes the milk from their mothers to clot. The milk proteins are broken down by pepsin. The stomach can store food for quite a long time. After 1 or 2 hours, the sphincter at the bottom of the stomach opens and lets the chyme into the duodenum. The small intestine is part of the alimentary canal between the stomach and the colon. It is called small intestine because it is narrow. Different parts of the small intestine have different names. The first part, nearest to the stomach, is the duodenum and the last part, nearest to the colon, is the ileum. Several enzymes are secreted into the duodenum. These enzymes are made in the pancreas which is a cream-coloured gland, lying underneath the stomach. A tube called the pancreatic duct leads from the pancreas into the duodenum. Pancreatic juice, a fluid made from pancreas flows along this tube. This fluid contains many enzymes, such as amylase, protease, and lipase. • Amylase breaks down starch to maltose • Trypsin, a protease enzyme, breaks down proteins to polypeptides. • Lipase breaks down fats into fatty acids and glycerol. These enzymes would not live in acidic conditions but the hydrochloric acid from the chime will be neutralized by pancreatic juice as it contains sodium hydrogencarbonate. BILE Bile is a yellowish green fluid that also flows into the duodenum. It is an alkaline, watery liquid that helps neutralize the acidic mixture from the stomach. It is made in the liver, and then stored in the gall bladder. It flows to the duodenum along the bile duct. Bile does not contain any enzymes but helps to digest fats by breaking up the large drops of fat into very small ones, making it easier for the lipase in the pancreatic juice to digest them into fatty acids and glycerol. This is called emulsification and is done by salts in the bile called bile salts. Emulsification is a type of mechanical digestion. Bile also contains yellowish bile pigments. These are made by the liver when it breaks down old red blood cells. The bile pigments are made from haemoglobin and will eventually excreted by the body. As well as receiving enzymes made in the pancreas, the small intestine makes some enzymes itself. They are made by the cells in its walls. The inner walls of all parts of the small intestine – the duodenum and ileum – is covered with millions of tiny projections. They are called villi. Cells covering the villi make enzymes. The enzymes do not come out into the lumen of the small intestine, but stay close to the cells which make them. These enzymes complete the digestion of food. The carbohydrase enzyme maltase breaks down maltose to glucose. Proteases finish breaking down any polypeptides into amino acids. Lipase completes the breakdown of fatty acids and glycerol. FEATURES OF THE SMALL INTESTINE FEATURE It is very long, about 5 m in an adult human. HOW THIS HELPS ABSORPTION TAKES PLACE This gives plenty of time for digestion to be completed, and for digested food to be absorbed as it slowly passes through. It has villi . Each villus is covered with This gives the inner surface of the small intestine a very large surface cells which have even smaller projections area. on them, called microvilli. The larger the surface area, the faster nutrients can be absorbed. Villi contain blood capillaries. Monosaccharides, amino acids, water, mineral and vitamins, and some fats, pass into the blood, to be taken to the liver and then round the body. Villi contain lacteals, which are part of the lymphatic system. Fats are absorbed into lacteals. Villi have walls only one cell thick. The digested nutrients can easily cross the wall to reach the blood capillaries and lacteals. ABSORPTION OF DIGESTED FOOD By now most carbohydrates have been broken down to simple sugars, proteins into amino acids and fats into fatty acids and glycerol. These molecules are small enough to pass through the wall of the small intestine and into the blood. This is called absorption. The small intestine is especially adapted to allow absorption to take place very efficiently. Water, mineral salts and vitamins are also absorbed in the small intestine. The colon and rectum are sometimes called the large intestine, because they are wider tubes than the duodenum and ileum. Not all the food that is eaten can be digested, and this undigested food cannot be absorbed into the small intestine. It travels on, through the caeccum, past the appendix and into the colon. In humans, the caecum and appendix have no function. In the colon, more water and salt are absorbed. However, the colon absorbs much less water than the small intestine. By the time the food reaches the rectum, most of the substances which can be absorbed have gone into the blood. All the remains of the bacteria, and some dead cells for the inside of the alimentary canal. This mixture forms the faeces, which are passed out at intervals through the anus. This process is called egestion. DIARRHEA Diarrhea is the loss of watery faeces. It happens when not enough water is absorbed from the faeces. It may seem like an annoyance but if its severe and goes on for a long time, it is a dangerous illness. Diarrhea is the second largest cause of death in children in the world. Severe diarrhea means that your body will lose dangerous amounts of water and salt from the body, causing the organs in the body to stop working. To treat diarrhea, oral rehydration therapy is needed as it involves drinking water with a small amount of salt and sugar dissolved in it. One of the causes of diarrhea is by a bacterium which causes cholera. Cholera bacterium can spread through water and food that has been contaminated with faeces from an infected person. In places where people are forced to live in unhygienic conditions such as refugee camps, cholera can spread rapidly. Cholera bacterium lives and breeds in the small intestine. The bacteria produce a toxin (poison) that stimulates the walls lining the intestine to secrete chloride ions. These ions accumulate in the lumen of the small intestine. This increases the concentration of the fluid in the lumen, lowering its water potential. Once this water potential become lower than the water potential of the blood flowing through the vessels in the walls of intestine, water moves out of the blood and into the lumen of the intestine, by osmosis. With enough fluids almost every person suffering with cholera will recover. After they have been absorbed into the blood, the nutrients are taken to the liver, in the hepatic portal vein. The liver processes some of them, before they can go any further. Some of these nutrients can be broken down, some converted into other substances, some stored and the remainder left unchanged. The nutrients, dissolved in the blood plasma, are then taken to other parts of the body where they become assimilated as part of a cell. The liver has an especially important role in the metabolism of glucose. If there is more glucose than necessary in the blood, the liver will convert some of it to the polysaccharide glycogen, and store it.
