Human Digestive System slides.pdf

Human Digestive System  Learning Outcomes Core Ideas Practices Values, Ethics, Attitudes explain the importance of investigate the show an appreciation of the digestive system effect of the importance of...

Human Digestive System  Learning Outcomes Core Ideas Practices Values, Ethics, Attitudes explain the importance of investigate the show an appreciation of the digestive system effect of the importance of explain how the main parts enzymes in sensible food and of the human digestive digestion lifestyle choices in the system work together to fight against diabetes perform a function (e.g., show an awareness that mouth, oesophagus, bacteria could have stomach, small intestine, beneficial or harmful large intestine, rectum and effects (e.g., bacteria in anus) the digestive tract could describe how a human help in digestion or digestive system helps in cause infections) the digestion of food state that the end-products of digestion are used for cellular processes like respiration, growth and tissue repair Why do we need food? Food provides energy for vital activities of the body This includes synthesizing new protoplasm, growth, and repair of worn out body parts. Why do we need food? In order to get energy to stay alive, the body undergoes a process called respiration. Carbon Nutrients dioxide Oxygen Water ENERGY Identifying nutrients in food Carbohydrates Identifying nutrients in food Protein Identifying nutrients in food Fat Identifying nutrients in food Fiber Identifying nutrients in food What other important nutrients does our body need to remain healthy? Water Vitamins Minerals Digestion of food When food has been consumed, it cannot be used by the body immediately. It has to be broken down into small molecules to be able to pass through the intestine walls and into the blood. This is because cell membranes are partially permeable, containing small pores. Substances that are too large are unable to pass through.  Digestion of food Partially permeable membrane In the intestines CELL Starch – too large to enter cell broken down Glucose – small enough to enter Digestion of food Definition: Digestion is the breaking down of large, complex and insoluble food molecules into small, simple and soluble molecules There are 2 types of digestion: 1) Physical 2) Chemical Physical digestion Breaking down of food is done through physical or mechanical means. For e.g. crushing, chewing, grinding, mixing. Physical digestion increases surface area to volume ratio so enzymes can access the food. Chemical digestion Breaking down of food into small molecules through the use of enzymes. This breaks the chemical bonds between the atoms in the food and will result in the simplest, smallest form of nutrients for absorption. Enzymes Are biological molecules produced by the digestive system Speed up the breakdown of large molecules into small molecules Without enzymes, the chemical reaction required to occur would take too long Enzymes speed up the rate of chemical reactions Enzyme names usually end with –ase. Maltase breaks down maltose Protease breaks down proteins Types of enzymes - carbohydrase Starch – too large to enter cell amylase maltose – still too large maltase glucose – small enough to enter cell Carbohydrates Found in starchy and sweet foods Breaks down into glucose Glucose is a source of energy for the body Recall respiration Fibre in fruits and vegetables is also a carbohydrate Cannot be digested in humans, will be passed out in feces Types of enzymes - protease Protein – too large to enter cell protease Polypeptide – still too large protease Amino acids – small enough to enter cell Proteins Found in meat, fish, eggs, beans Breaks down into amino acids Amino acids are used to grow or repair cells in the body by making required proteins Fun fact: Enzymes are made from proteins Types of enzymes - lipase lipase Fat – too large to enter cell 1 glycerol + 3 fatty acids – small enough to enter cell Fats Found in dairy products e.g. butter, cream, cheese, milk, oils, and animal fat Breaks down into glycerol and fatty acids Stored under skin to prevent heat loss, or to cushion internal organs Long term storage of energy in animals Provides twice as much energy per gram as carbohydrates How does the digestive system work?  mouth oesophagus liver stomach gall bladder large intestine small intestine rectum anus Mouth Physical digestion: Teeth chew and crush food into smaller pieces. This increases the surface area to volume ratio of the food. Allows enzymes to access the food to increase the rate of chemical digestion. Chemical digestion: Saliva contains amylase. Starch is broken down into maltose. Mouth Saliva also helps to lubricate the food, making it easier to swallow. Tongue rolls the food into a ball to swallow. Taste buds on tongue allow us to taste food. Oesophagus Chemical digestion: Starch from mouth continues to be digested by amylase to maltose while travelling down. The food travels to the stomach via gravity, as well as muscle contractions. Stomach Stomach muscles Physical digestion: The stomach churns the food into smaller pieces. Chemical digestion: Gastric Gastric juices juices containing protease is released. Proteins are broken down into polypeptides. Stomach Gastric juices contain hydrochloric acid to Kill microorganisms like bacteria Create an acidic environment for proteases to work How do you think the stomach protects itself from the acid and protease?  Small intestine Physical digestion: Bile is produced by the liver. It is then accumulated and secreted by gall bladder. Bile emulsifies fat from large fat globules to small fat droplets.  Bile Fats do not mix well in water and tend for form large globules, or clumps. Bile emulsifies the fat by surrounding it, allowing it to mix with water. Alcohol works in a similar way (recall: ethanol- emulsion test for fats) Emulsification increases surface area to volume ratio of fats, allowing it to be exposed to lipase. (digestive enzyme)  Small intestine Chemical digestion: Main site for chemical digestion. Amylase, maltase, proteases and lipases are present here. All nutrients are completely digested. Digested nutrients are absorbed into bloodstream here. Large intestine, rectum, anus Large intestine mainly absorbs water and mineral salts from food. Rectum temporarily stores faeces (undigested food) Anus is a ring of muscle that releases faeces out of the body.  Digestion summary Enzymes Secreted Nutrients digested secreted into amylase Mouth starch → maltose protease Stomach proteins → polypeptides amylase Small starch → maltose → glucose maltase intestine protease proteins → polypeptides → amino acids lipase fats → fatty acids + glycerol How do products of digestion (glucose) affect the body? Excessive simple sugars When the levels of glucose in the blood is too high, this is a condition known as diabetes. The body regulates the concentration of glucose in the blood by releasing insulin, a hormone. Diabetes When the body produces insufficient insulin or does not respond to insulin, it will result in diabetes. Diabetes is dangerous because it is often linked to other serious health conditions like obesity, heart attacks, kidney problems, high blood pressure, blindness and stroke. Diabetes symptoms  Diabetes monitoring Blood glucose concentration can be measured using: Blood sugar meter: Finger is Continuous monitoring: pricked and drop of blood is sensor is stuck to arm for read by the machine about 2 weeks each time Reducing risk of diabetes Have regular health screenings Have a healthy and balanced diet Eat more whole grains, vegetables, fruits, lean meat Avoid foods high in salt, sugar and saturated fats Exercise for at least 30 mins a days, at least 5 days a week Avoid smoking and drinking alcohol What are some issues that affect the human digestive system? Constipation When a person undergoes stress, consumes certain medicines, not having enough fibre or water, they may experience constipation. Constipation Recall: what is the function of the large intestine? It absorbs water and mineral salts from undigested food to form faeces. When one has constipation, faeces moves through the large intestine slowly. This gives the large intestine more time to absorb more water. This results in the faeces becoming hard and dry Gastric pain One common cause of gastric pain (stomach pain) is gastritis. This is the painful swelling or inflammation of the stomach lining. Gastric pain Gastritis may be caused by bacteria, virus or lifestyle habits like skipping meals and consuming alcohol, caffeine or oily foods. This increase stomach acid content which irritates and hurts the stomach lining. Symptoms may include upper abdominal pain, nausea and bloating.  Food poisoning Eating food contaminated by bacteria can lead to diarrhoea or vomiting. These bacteria can cause life-threatening diseases such as cholera and salmonella infections. Fun fact: Even though cooking may kill the bacteria, but bacteria may produce toxins that cannot be broken down by heat, still causing food poisoning, even if the food was well cooked.  Food poisoning Avoiding food poisoning: 1) Handle food safely Use separate utensils and crockery for raw and cooked food Check that vendors handle food appropriately Cover food before placing in the refrigerator Store cook and ready-to-eat food above raw food in the refrigerator Keep raw foods below 5 C Food poisoning Avoiding food poisoning: 2) Choosing food carefully Check that bottled milk or drinks are sealed tightly Select foods with an expiry date that has not passed Do not consume food from cans that are dented or bloated Do not buy chilled or frozen food that is not stored at the appropriate temperature. Chilled food should be between 0-4 C, frozen food should be below -18 C Do not consume food that is mouldy Beneficial bacteria But not all bacteria are bad! There are good bacteria living in our intestines! Up to half of the dry mass of feces is made up of bacteria! Bacteria in our intestines help our immune systems, digestion and absorption of nutrients, and produce certain enzymes, vitamins and amino acids. Beneficial bacteria Some food items that are produced by (and contain) bacteria: Coffee, chocolate, yoghurt, cheese, vinegar, kombucha, miso, sourdough bread, smelly tofu, kimchi and belacan. These foods involve a fermentation process that involves bacteria, and sometimes even fungi. Extension: Science behind healthcare Endoscopy This is a procedure where the gastroenterologist examines a patient’s digestive tract using various methods. Endoscopy The patient may sometimes be sedated or awake with use of anesthesia. The tube inserted has a camera and light in order to send video to the monitor. Endoscopy An alternative is the capsule camera. Endoscopy The capsule camera moves through the digestive system slowly and the patient returns after 1-2 days to upload the video and retrieve that capsule from the feces. You may watch a video about the process here: https://youtu.be/5ufESc1bK78