Digestive System Digestion Three main functions: Ingest food Break it down into nutrients the body can use Eliminate waste 2 Types of Digestion: Mechanical: physically breaking food down into smaller pieces Chemical: chemically altering food, breaking things down into their chemical components: Starches simple carbohydrates Proteins amino acids Digestion All throughout the digestive tract, mechanical digestion occurs. Chemical digestion of specific types of molecules occurs in different organs. Mouth/Esophagus In the mouth, mechanical breakdown occurs with the help of the tongue and teeth. Saliva in the mouth contains an enzymes called amylase, which starts to break starches down into simple sugars. As food is broken down, it is shaped into small semi-circular chunks called a “bolus” which is swallowed down into the esophagus. Esophagus The esophagus is a tube that connects the mouth to the stomach. It is lined with smooth muscle (you can’t control this type of muscle). The muscle rhythmically contracts, pulling the food towards the stomach. This process is known as peristalsis. Before food enters the stomach, it encounters a ring of smooth muscle known as the cardiac sphincter. Choking Area before the esophagus called the pharynx splits! Esophagus stomach Trachea lungs To prevent food from entering the lungs and people choking, flap of tissue called epiglottis covers the trachea when we swallow. Stomach The environment of the stomach is very acidic, pH of about 2, due to gastric glands secreting stomach acid. •In the stomach 3 layers of smooth muscle control its contraction mechanical breakdown of food. •Also enzymes pepsin is released here which breaks down proteins. (chemical breakdown) Small Intestine The pyloric sphincter separates the stomach from the small intestine. The small intestine is 7m long and 2.5cm wide. Smooth muscle continues peristalsis and mechanical digestion of food. Chemical digestion relies on 3 accessory organs: liver, pancreas and gallbladder. Small Intestine The pancreas has 2 functions in digestion: secretes enzymes that break down sugars, proteins and fats. Raises the pH to above 7, allowing intestinal enzymes to work properly. The liver produces bile, which breaks fats as down The gallbladder serves a chemically bile storage unit.. The juices of the pancreas and liver enter the small intestine via the common bile duct. Small Intestine As food is chemically digested the particles are absorbed by the walls of the small intestine into the bloodstream. Finger-like projections called villi line the walls of the small intestine, to increase the surface area, maximizing nutrient absorption. Villi Villi Large Intestine Large intestine is 6.5cm in diameteer and about 1.5m long. Includes the colon, rectum, and appendix. As food enters the colon it is called chyme. The function of the large intestine is to absorb water from the chyme. The leftover, undigested material is known as feces. This material is expelled through anus. Time for Digestion Structure Function Time of food in structure Mouth Mechanical/chewing Some chemical digestion 5-30 seconds Esophagus Transport (swallowing) 10 seconds Stomach Mechanical and Chemical digestion 2-24 hours Small Intestine Mechanical and chemical digestion 3-4 hours Large Intestine Water absorption 18 – 48 hours Malfunctions Stomach problems: Ulcers in the stomach are often caused by a bacteria infection. Ulcers are holes in the stomach’s lining. Acid reflux occurs when some acid gets regurgitated into the esophagus. Large intestine problems: Diarrhea is a result of not enough water absorbed from undigested material in the large intestine. Constipation occurs when too much water is removed. Your Turn Create a fairytale story about the digestive system. Your main character must be a type of food that can be successful digested. Make it interesting, choose something that has fats, protein, and carbs in it! Tell the story of this items adventures through digestion.