The Digestive System

1. The Digestive System

2. Major roles of the digestive system • breaks down food into usable compounds for growth and metabolism (energy). • Neutralizes harmful chemicals from ingested food. • Maintains proper water content and chemical composition of the blood.

3. 5 Different Types of Nutrients • Proteins • Carbohydrates • Lipids • Nucleic acids • Vitamin/minerals

4. FoodisFuel • Nutrients are substances that provide the energy and raw materials the body needs to grow, repair itself, and function properly. • The 4 classes of polymers found in all living things are carbohydrates, proteins, fats, and nucleic acids.

5. Carbohydrates • Carbohydratesare energy rich organic molecules composed of carbon, hydrogen, and oxygen. Complex Carbohydrates Simple Carbohydrates starch glucose

6. Proteins • Most of the body’s structures are composed of proteins. Proteins are complex polymers composed of a specific arrangement of monomers called amino acids.

8. Proteins (cont.) • The body uses the proteins we eat to build and repair body parts. Proteins are broken down in the digestive process and the monomers are re-assembled into thousands of proteins.

9. Lipids • Like carbs, lipids are energy rich polymers made of carbon, hydrogen, and oxygen. • Lipids include fats, oils, waxes, and cholesterol. Fatty acid (saturated) Glycerol Fatty acid (unsaturated) Unsaturated fat

10. Nucleic Acids • Nucleic acids (also called nucleotides) are the molecules which make up our DNA (also our RNA). • There are only four different kinds of nucleotides that make up our DNA, which include carbon, oxygen, hydrogen, nitrogen, and phosphorus atoms.

11. Nucleic Acids • The differences among living things are determined by the order of nucleotides in the DNA.

13. Vitamins and Minerals Vitamins are natural chemicals needed by your cells to run smoothly. Although already present in most of the foods you consume, an unhealthy diet can result in vitamindeficiency. Minerals are elements you body needs, and like vitamins, they’re needed by all cells to operate properly.

14. The process of Digestion… • Digestion is really four distinct processes: • mechanical digestion • chemical digestion • absorption • elimination

15. Primary Organs (the alimentary canal) mouth esophagus Small Intestine Large Intestine Rectum/anus Accessory Organs (aid digestion) Salivary glands Pancreas Liver Gall bladder Organization of the Digestive System

16. The Oral Cavity (mouth) • Mechanical digestion involves the mashing and tearing of food with your teeth and tongue, while saliva begins breaking down starch into simple sugars.

17. Teeth

18. Did You Know?... • Streptococcus bacteria can form thick layer on your teeth if proper oral hygiene is not maintained. Over time they produce acids which lead to cavities and tooth decay.

19. Salivary Glands • Salivary glands secrete saliva (about 2 pints a day!) which starts breaking down carbohydrates with an enzyme called amylase, and more importantly, provides a liquid medium to ease the movement of food through the alimentary canal.

20. Swallowing • After mechanical digestion, your tongue pushes the bolus to the pharynx and into the esophagus where peristalsis takes over.

21. The Esophagus • Approximately 10” long • Tube moves food from the throat to the stomach (peristalsis)

22. Did you Know…. • Involuntary smooth muscle contractions called Parastalsis move food products through the gastrointestinal tract, from beginning to end! • What part of the brain regulates this autonomic process?

23. Challenge Question • What happens when excess acid from your stomach gets into your esophagus?

24. Stomach • Stores and mixes ingested food • breaks it down into tiny pieces with HCl and other powerful enzymes. • Acid in the stomach eliminates bacteria

25. The Enzymes of the Stomach • Within your stomach, a number of Digestive enzymes break down polymeric macromolecules into monomers suitable for absorption. • proteases and peptidases split proteins into their monomers, the amino acids. • lipases split fat into three fatty acids and a glycerol molecule. • carbohydrases split carbohydrates such as starch and sugars into simple sugars such as glucose, the simplest sugar on earth. • nucleases split nucleic acids into nucleotides.

26. Key Stomach Enzymes • Pepsinogen is the primary gastric enzyme produced specialized "chief cells" lining the stomach wall. Present in its inactive form pepsinogen is called zymogen. It is activated by stomach acid into its active form, pepsin. Pepsin breaks down the proteins into their constituent amino acids. • When the stomach expands, G-cells secrete gastrin, an endocrine hormone, into the bloodstream. I elicits a cascade of responses throughout the body which includes feeling ‘full,’ and the secretion of additional HCl.

28. Small Intestine • Long, narrow, winding, tube. • Insides are covered with microscopic ‘fingers’ called villi to maximize surface area. • Nutrients from the food (chyme) pass into the bloodstream through the small intestine walls. (absorption)

30. Inside the Small Intestine

31. Specialized Cells of the Small Intestine • Absorptive cells, or enterocytes, comprise the predominant epithelial cell type lining the lumen of the small intestine and colon. These cells make up the villi seen earlier. • Specialized for secretion of mucus, unique Goblet cells can be found scattered among the absorptive cells in the epithelium of the small intestine (and colon). These epithelial facilitate passage of material through the bowel.  

32. Did you know… • If you could stretch out your small intestine it would be 22 feet long!

33. Large Intestine • 4-5 feet long • Separated from the small intestine by the iieocecal valve (prevents backflow) • Ascending colon accepts unabsorbed material from small intestine. • Absorbs water and various minerals from the remaining material, effectively solidifying waste for elimination in the descending colon. Sigmoid colon cecum

34. Gut Flora: The Forgotten Organ • Making up as much as 60% of feces by mass, you have hundreds of trillions of bacteria living in your intestines. About 500 different species are represented, although the majority are E coli. • metabolic activities performed by these bacteria resemble those of an organ, leading some to liken gut bacteria to a "forgotten" organ. • the microorganisms perform a host of useful functions, such as fermenting unused polysaccharide substrates, training the immune system, preventing growth of pathogenic bacteria, and producing vitamins K and B7 for the host.

35. Liver • The liver is the largest organ in the body. It resides below the diaphragm in the RUQ of the abdominal cavity. The adult liver weighs approximately 3 pounds. • The liver is separated into right and left lobes, separated by the falciform ligament. The right lobe is much larger than the left lobe. The functional cells of the liver are known as hepatocytes.

36. Liver Function • Metabolism of fats, proteins, and carbohydrates • Enzyme synthesis and activation • Storage of glycogen, vitamins, and minerals • Synthesis of plasma proteins, such as albumin, and clotting factors • Blood detoxification and purification • Production of bile, an alkaline compound which aids in digestion via the emulsification of lipids.

38. Gallbladder • The gallbladder is a small pouch positioned under the right lobe of the liver. It stores bile produced by the liver. • After you eat, the gallbladder is empty and flat, (imagine a deflated balloon). Before a meal, the gallbladder may be full of bile and approximately the size of a small pear. • When lipids are present, the gallbladder squeezes stored bile into the duodenum through the common bile duct. Emulsifying them for absorption and processing.

39. Did You Know That? • Fatty diets can cause gallstones!

40. Pancreas • Secretes additional protease and lipase enzymes into S.I. to aid in absorption. • Neutralizes acids that enter small intestine by secreting HCO3– ion. • Regulates blood sugar by producing insulin and glucagon.

41. The Anus and Rectum • Storing solid waste before elimination, the final straight portion of the large intestine is called the rectum. • Controlled by sphincter muscles, the external opening of the rectum is called the anus.

42. Did you Know?... • Suspended in transparent box above the Thames in London, Magician David Blaine shocked the world by fasting for 44 days; losing 54 pounds (25% of his body mass) in the process. • Physiologically speaking, how did he remain alive for this length of time? What organs were likely damaged?

43. Pop Quiz!

44. Name each colored organ • Green: • Red: • Pink: • Brown: • Purple: • Dark Green: • Yellow:

45. 2 • In this picture, what digestive organ does each # represent? 1 3 4 5

46. “That’s All Folks!” More to come…