Digestive System

1. Digestive System

2. 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

3. Digestion • All throughout the digestive tract, mechanical digestion occurs. • Chemical digestion of specific types of molecules occurs in different organs.

4. 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.

5. 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.

6. 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.

7. 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)

8. 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.

9. 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 down chemically. The juices of the pancreas and liver enter the small intestine via the common bile duct. The gallbladder serves as a bile storage unit.

10. Small Intestine Villi • 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

11. 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.

12. Time for Digestion

13. 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.

14. 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.