The Digestive System

1. The Digestive System By: Antony Sanisidro & Tracy Ibezim

2. What is the Digestive System? The digestive system consists of several organs and four digestive glands in which its function is to convert the food that we ingest, into absorbable nutrients that the body needs for growth and survival.

3. How has it evolved? Early vertebrates evolved in the ocean, making their way to freshwater habitats and continuing on through the evolutionary cycle until they transitioned from water habitats to dry land. Over time these animals have undergone internal changes to help the body fulfill the requirements to sustain life.

4. Any adaptations? • As Omnivores our dental structure consists of 32 teeth; we have two blade-like incisors for biting, a pointed canine for tearing, two premolars for grinding, and four molars for crushing.

5. Any other ones? • Our cecum and intestines must be long enough so our body can have enough time to break through the plant’s cell wall and absorb all the nutrients it has to offer. An increase in surface area leads to an increase in the amount of time for digestion and absorption of nutrients.

6. How does this system help us survive? • The digestive system helps to breakdown food so the extracted nutrients can be absorbed into the blood stream, allowing us to maintain homeostasis. It also help maintain a healthy immune system by removing bad bacteria during the process of defection.

7. Nutritional Requirements • The human body has 3 main nutritional requirements: • Needs “fuel” to perform cellular work. • Needs all the raw organic materials needed for biosynthesis. • Needs essential nutrients. • Such as essential amino acids, essential fatty acids, vitamins, and minerals

8. How does the body manage “fuel”? • Our body obtains chemical energy or “fuel” from the oxidation of carbohydrates, proteins, and fats that are used to help cells function properly. • Excess calories are stored in the liver and muscle cells as a form of glycogen.

9. What happens if the glycogen stores are filled? • The body then stores the excess calories as fat, this is what we call over nourished. • You are undernourished when your body doesn’t intake enough calories so it has to extract the already stored calories for use. • Appetite is controlled by the leptin hormone.

10. What is biosynthesis? • The formation of complex chemical compounds through the combination of simpler compounds or elements in a living organism. • As food molecules are broken down into their simplest form, organic precursors such as carbon skeletons use those elements to build our own molecules.

11. Essential Amino Acids • Amino acids are essential to the body because it’s a source of energy and plays a key role in building and repairing muscles. • Animals require 20 amino acids to make proteins in which eight of them are essential to the adult diet. Any diet that lacks one or more essential amino acid is considered to be malnourished due to protein deficiency. • The best way to obtain protein is by eating meat, cheese, eggs, and other animal products.

12. How do vegetarians get protein? • Vegetarians need to balance out their diet in order to obtain the correct proportion of amino acids. • For example, corn is missing the amino acid known as lysine but it contains the amino acid methionine, and beans contain methionine but they are lacking lysine. Both need to be consumed to avoid protein deficiency.

13. Essential Fatty Acids • These are the certain unsaturated fatty acids that the body cannot make. • Fatty acids play a key role in the production of some phospholipids found in the cell membrane. • These fatty acids can be found in foods and oil that contain omega such as olive oil, vegetable oil, soy beans, walnuts, fish, chicken, and many more.

14. Vitamins • Two types: Water-soluble and Fat-soluble • The B complex contains several compounds that function as coenzymes for metabolic processes, and vitamin C is required in the synthesis of connective tissue. • Vitamin A is used in the visual pigments of the eye. Vitamin D is in the formation of bone as well as in the absorption of calcium. Vitamin E is used to help protect membrane phospholipids from oxidation and vitamin K is used for blood clotting.

15. Some of the uses for these vitamins

16. The Process of Digestion. . . Finally! • There are four main stages in the digestive process: 1) Ingestion 2) Digestion 3) Absorption 4) Elimination

17. The Mouth • Uses salivary glands to produce saliva. • Saliva contains the enzyme Amylase • Food is mechanically broken down by the grinding, chewing, and smashing of the teeth. • The tongue then shapes the chewed up food into a ball. • This ball is know as bolus.

18. The Pharynx • The region in the throat where the intersection that leads to the trachea and the esophagus is guarded by a cartilaginous flap known as the epiglottis. • When breathing, the epiglottis moves upward and the larynx moves downward, opening the breathing tube and contracting the esophageal sphincter muscle. • When swallowing, the epiglottis moves downward and the larynx moves upward, closing the glottis and relaxing the esophageal sphincter muscle.

19. The Esophagus • The tube that transports food from the pharynx to the stomach. • As the bolus passes through the involuntary waves of contraction, salivary amylase continues to hydrolyze the bolus for a smooth and slippery transition into the stomach.

20. The Stomach • The epithelium in the walls of the stomach produce gastric juice. • Gastric juice contains hydrochloric acid with a ph of 2, meaning it’s acidic enough to dissolve iron nails. It also contains the enzyme pepsin which is used to split proteins into smaller polypeptides. • Over a 2-6 hour period the bolus turns to acid chyme due to enzymatic action and mixing within the stomach.

21. The Small Intestine • The longest section of the alimentary canal and is where most of the nutrients are absorbed into the bloodstream. • Chyme is mixed with the digestive juices produced from the pancreas, liver, and gall bladder. • The pancreas produces several hydrolytic enzymes that are used to alter the acidity of the chyme. • The liver produces bile which is stored in the gall bladder until it’s needed to help the digestion and absorption of fats. • Chyme undergoes the digestion of proteins, carbohydrates, Nucleic acids, and fats. The small intestine breaks everything down to the simplest form so all of the nutrients can be absorbed into the blood stream by the villi.

22. What it looks like

23. Some of the types of digestion

24. The Large Intestine • Major function is to reabsorb the water that has acted as a solvent of the digestive juices. • Once the chyme enters the large intestine, it falls into a small pouch known as the cecum. • Attached to the cecum is our appendix, the appendix acts as a “safe house” where it protects good bacteria and produces it when the bacteria has died in the intestines. • Chyme solidifies by a process called peristalsis and becomes feces. The feces then take 12-24 hours to reach the end of the large intestine and pass through the rectum and out the anus.

25. 6.1.1. Explain why digestion of large food molecules is essential • Food molecules are too big to pass through membranes and enter cells, if they can’t enter cells then the nutriments won’t be able to transport through the bloodstream to the areas of the body where they are needed. • Our macromolecules aren’t identical to the ones in food which means food molecules are broken down into a simpler form known as monomers. • Enzymatic hydrolysis breaks bonds by using the addition of water. Once this is done, the body is now able assemble its own molecules in a form that our bodies can use.

26. 6.1.7 Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion. • There are four parts to the structure of the villus; there is the microvillus, the thin layer of epithelial tissue, the blood capillaries, and the lacteal. • The villi absorbs nutrients and transfers them into the blood stream so they can be transported throughout the body. • The microvilli help to speed up the process of absorption through the use of protein channels and pumps. • The blood capillaries receive the absorbed nutriments and release them into the blood stream. • The lacteal is a branch located in the core of the villus and is used to gather and carry off fats after absorption.

27. What is looks like

28. Thanks for listening!