The Digestive System

1. The Digestive System Stephanie Malouf

2. What is it? • Digestion is the process through which food and drink are broken down so that their nutrients can be transported throughout the body by the way of the circulatory system.

3. How does it work? • The digestive process uses both mechanical and chemical processes to breakdown food and drink to acquire nutrients.

4. Breaking down particles involves: • Movement: peristalsis • Peristalsis is the process of moving food and drink along the digestive tract. • Secretion: release of the digestive fluids • Digestion: breakdown food particles • Absorption: passage of molecules into the body’s interior • Elimination: remove waste

5. Where does it occur? • The digestive system follows a tract starting at the mouth and ending at the start of the excretory system.

6. Digestive Tract • 1) Mouth • 2) Esophagus • 3) Stomach • 4) Small Intestine • 5) Large Intestine

7. Mouth • The mouth is the very start of the digestive system. It is the entrance for both food and drink. • The mouth performs mechanical breakdown of food breaking it into smaller particles by grinding, tearing, and chewing with the teeth and jaws.

8. Mouth continued… • Chemical breakdown occurs within the mouth through the salivary glands. The salivary glands produce salivary amylase which break down starch. • The one organ in the mouth, the tongue, uses both mechanical and chemical breakdown. The tongue manipulates food particles and moves food to the back of the mouth when swallowing.

9. Esophagus • The esophagus is a long muscular tube that extends from the pharynx to the stomach. • The esophagus provides transportation for food to get to the stomach. Muscles in the esophagus propel a bolus (a mass of food) down the tube to enter the stomach.

11. Stomach • The stomach is a sac-like organ with muscular walls. Epithelial cells line the inner surface of the stomach. • The food is churned in the stomach to breakdown through mechanical breakdown. It contains gastric juices made of hydrochloric acid, pepsinogen and mucus for chemical breakdown.

12. Gastric acids purposes • Hydrochloric Acid (not directly involved) kills microorganisms, lowers the stomach’s pH level and activates pepsinogen. • Pepsinogen starts protein digestion and produces the enzyme pepsin • Enzyme pepsin is an enzyme that breaks down proteins and carbohydrates. • Mucus sets up a protective barrier between cells and the stomach acid.

13. Traveling through… • When food particles have been broken down enough in the stomach chyme ,a mixture of food and acid, moves to the small intestine.

14. Small Intestine • The small intestine is a long loose tube coiled in the abdomen. It is split into three parts. • The purpose of the small intestine is to absorb nutrients through its villi that are then transported by the bloodstream throughout the body.

15. Small Intestine continued… • Three parts: • The first part the duodenum produces mucus to protect the intestinal lining from acid in entering chyme. • Jejeunum is where the villi are in the small intestines. The villi and microvilli absorb nutrients in the chyme into capillaries because they are connected. • The ileum absorbs bile salts used to further digestion of fats.

16. Small Intestine diagram

17. Large Intestine • It is a 5-6 foot tube that encases the surrounds the small intestine. Divided into parts, it starts at the cecum and ends at the rectum. • The large intestine recovers water and electrolytes from digested food, forms and stores feces, performs microbial fermentation, and contains microbes that produce that digest indigestible molecules.

18. Other organs involved • Liver • Gall Bladder • Pancreas • Appendix

19. Liver • Seated on the right side of the stomach is the liver. It is a large, rubbery, reddish brown organ. • It produces and sends bile to the small intestine to help with digestion. • The bile contains bile salts and emulsify fats.

20. Gall Bladder • It is a pear-shaped organ positioned under the liver. • It stores excess bile. • Do we need it? • Many people have their gall bladder removed. We are able to live without our gall bladder but have to monitor what we eat more.

21. Liver and gall bladder

22. Pancreas • Located behind the stomach is the pancreas. It is an elongated and tapered organ. • The pancreas neutralizes chyme with pancreatic juice sent to the small intestine, by way of the pancreatic duct. • It also produces glucagon and insulin.

23. Pancreas diagram

24. Appendix • It is a small thin tube that sits in the lower right abdomen. • The function of the appendix is unknown. There are only theories as to its function • Theories • It reboots the digestive system after diarrheal diseases. • It is a safehouse for beneficial bacteria. • It once helped cavemen digest leaves.

25. Appendix diagram

26. How does this work with other systems? • The digestive system works with the following systems: • Circulatory system • Endocrine system • Excretory system • Nervous System

27. How? • The circulatory system transports nutrients extracted during the digestive process throughout the body. • Part of the digestive system, the liver and pancreas participate in the endocrine system function by regulating glucagon release and regulating the speed of digestion.

28. Continued… • The digestive system eventually leads to the excretory system. After the nutrients have been collected the waste is released through the excretory system. • The nervous system stimulates for us to swallow our food.

29. Homeostasis • The digestive system helps in homeostasis by supplying nutrients to the bodies cells for the cells to function correctly. • Also the liver helps in digestion by breaking down toxic substances such as alcohol by producing urea.

30. Evolving… • The digestive system for us has stayed consistent over time minus the possibility of the appendix once being useful.

31. Bibliography • Body Systems and Homeostasis (n.d.). April 3, 2013. From http://www.mhhe.com/biosci/genbio/maderbiology/supp/ho meo.html • Digestive System (n.d.). National Geographic. April 2, 2013. From http://science.nationalgeographic.com/science/health-and- human-body/human-body/digestive-system-article/ • McKie, Robin (March 3, 2012). Is the mystery of the appendix close to being unravelled?. The Observer. April 3, 2013. From http://www.guardian.co.uk/science/2012/mar/04 /appendixstore-beneficial-bacteria • Picture of the appendix (April 28, 2010). WebMD. April 2, 2013. From http://www.webmd.com/digestive-disorders/picture- of-the-appendix • Picture of the liver (April 28, 2010). WebMD. April 2, 2013. From http://www.webmd.com/digestive-disorders/picture-of-the- liver?page=2

32. Continued… • The Digestive System (March 12, 2007). Online Biology Book. April 2, 2013. From http://www2.estrellamountain.edu/faculty/farabe e/biobk/biobooktoc.html • The Pancreas: Anatomy and Functions (n.d.). Wexner Medical System. April 2, 2013. From http://medicalcenter.osu.edu/patientcare/healthc areservices/liverbiliarypancreaticdisease/pancreas anatomyfunction/Pages/index.aspx • Your Digestive System (July 25 2012). WebMD. April 2, 2013. From http://www.webmd.com/heartburn- gerd/your-digestive-system?page=2

33. Picture Credits • Picture of the appendix (April 28, 2010). WebMD. April 2, 2013. From http://www.webmd.com/digestive-disorders/picture-of-the- appendix • Picture of the liver (April 28, 2010). WebMD. April 2, 2013. From http://www.webmd.com/digestive-disorders/picture-of-the- liver?page=2 • The Digestive System (March 12, 2007). Online Biology Book. April 2, 2013. From http://www2.estrellamountain.edu/faculty/farabee/biobk/biobooktoc.html • The Pancreas: Anatomy and Functions (n.d.). Wexner Medical System. April 2, 2013. From http://medicalcenter.osu.edu/patientcare/healthc areservices/liverbiliarypancreaticdisease/pancreas anatomyfunction/Pages/index.aspx • Your Digestive System (July 25 2012). WebMD. April 2, 2013. From http://www.webmd.com/heartburn-gerd/your-digestive-system?page=2