Grade 7 chapter1 lesson1 - the digestive system

Lesson 2 The Digestive system
-Functions of Digestive system
-Digestion
-Types of Digestion
-Enzymes
-The role of Enzymes in Digestion
-Organs of Digestive system
-The Mouth
-the Esophagus
-Peristalsis
-The Stomach
-Chyme
-the Small Intestine
-Villi
-the Large intestine
-Bacteria and Digestion
-the Digestive system and Homeostasis
-Common Ailments and Disorders of the Digestive system

1. The Digestive System Grade 7 Biology Prepared and Presented By: Lerma P. Pendon

2. FUNCTIONS OF THE DIGESTIVE SYSTEM There are 4 main steps of digestion in the human body: 1. Ingestion is the act of eating or putting food in your mouth. 2. Digestion is the mechanical and chemical breakdown of food into small particles and molecules that your body can absorb and use. 3. Absorption occurs when the cells of the digestive system take in small molecules of digested food. 4. Elimination or excretion is the removal of undigested food and other wastes from your body.

3. TYPES OF DIGESTION There are 2 types of digestion: 1. Mechanical Digestion - food is physically broken into smaller pieces. - digestion happens when you chew, mash, and grind food with your teeth and tongue. 2. Chemical Digestion - chemical reactions break down pieces of food into small molecules.

4. ENZYMES Chemical digestion cannot occur without substances called enzymes. Enzymes are proteins that help break down larger molecules into smaller molecules. Enzymes also speed up or catalyze the rate of chemical reactions. Without enzymes , some chemical reactions would be too slow or would not occur at all.

5. The Role of Enzymes in Digestion Amylase helps break down carbohydrates into sugars or glucose. It is produced by the salivary glands and pancreas. Pepsin helps break down proteins. It is produced in our stomach. Lipase helps break down fats. It is produced in the pancreas, mouth, and stomach.

6. ORGANS OF THE DIGESTIVE SYSTEM Two Parts of the Digestive System: Digestive Tract - it extends from the mouth to the anus . - the mouth and anus are the two openings of the digestive tract. Accessory Organs - organs that help the body break down and absorb food. - these organs include the tongue, salivary glands, liver, gallbladder, and pancreas.

7. Mouth Pharynx Esophagus Stomach Small intestine Large Intestine Rectum Anus The digestive tract is made up of:

8. Mouth The teeth mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase , which helps break down starch). The mouth is responsible for mastication . Mastication is the process of chewing. Also known as mechanical digestion . Bolus is the product mechanical digestion.

9. Pharynx Also called the throat . Pharynx is the portion of the digestive tract that receives the food from your mouth. Its muscular walls function in the process of swallowing, and it serves as a pathway for the movement of food from the mouth to the esophagus. Epiglottis is a flap-like structure at the back of the throat that closes the windpipe over the trachea preventing food from entering it.

10. Esophagus A muscular tube that connects the mouth to the stomach. Approximately 10 inches long. It moves the food from the throat to the stomach using muscle movement called peristalsis . Peristalsis is a wavelike contraction from the esophagus to the large intestine. At the inferior end of the esophagus is a muscular ring called cardio-esophageal sphincter . The function of this sphincter is to close the end of the esophagus and prevent the backflow of food from the stomach to the esophagus.

11. Stomach A large and hollow organ, located on the left side of the abdominal cavity. This major organ acts as temporary storage for food so that the body has time to digest large meals properly. The stomach contains an acidic fluid called gastric juice . The gastric juice makes the stomach acidic. It mixes food with digestive juices that contain enzymes such as lipase to break down proteins and lipids, the process is called chemical digestion . The product of chemical digestion is called Chyme . Chyme is a watery liquid that passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.

12. Small Intestine It is a long, thin tube connected to the stomach. It measures about 2.5 cm long. 3 Parts of the Small Intestine: Duodenum – chemical digestion of proteins, carbohydrates, nucleic acids, and fats takes place. Jejunum - breaking down and absorbing nutrients from food. Ileum - most water and nutrients are absorbed. The folds of the small intestine are covered with fingerlike projections called villi.

13. The villi contain blood vessels . Nutrients in the small intestine diffused into the blood cells through these blood vessels. Then, your circulatory system passes them on to other parts of your body to store or use. V illi (villus, singular)

14. The P ancreas , L iver and Gallbladder The pancreas and the liver produce substances that enter the small intestine and help with chemical digestion. The pancreas produces an enzyme called amylase that helps break down carbohydrates and a substance that neutralizes stomach acid. The liver produces a substance called bile . Bile makes it easier to digest fats. The gallbladder stores bile until it is needed in the small intestine.

15. Large Intestine It is a long, thick tube about 1.5 meters long, it is much shorter than the small intestine. Materials that pass through the large intestine are the waste products of digestion. The waste products become more solid as excess water is absorbed. It is where the feces are formed. Large intestine is also called the “Colon”.

16. Rectum Peristalsis continues to force the remaining semisolid waste material into the last section of the large intestine called the rectum . The final straight portion of the large intestine, approximately 6 inches long. The rectum is a continuation of the large intestine and connects to the anus.   For temporary storage of feces . To expel solid and gaseous waste from the gastrointestinal tract. Anal Sphincter – prevents the release of feces/wastes.

17. Anus The anus is the last part of the digestive tract. It is a 2-inch-long canal consisting of the pelvic floor muscles and the two anal sphincters (internal and external). The lining of the upper anus is specialized to detect rectal contents . It lets you know whether the contents are liquid, gas, or solid. The internal sphincter is always tight, except when stool enters the rectum. It prevents us from pooping involuntarily when we are asleep or otherwise unaware of the presence of stool.  When we get an urge to go to the bathroom, we rely on our external sphincter to hold the stool until reaching a toilet, where it then relaxes to release the feces or wastes.

18. Bacteria and Digestion It's perfectly normal for poop to have an unpleasant odor. The smell comes from bacteria in the colon that help break down digested food. Some bacteria have an important role in the digestive system. The large intestine absorbs water and contains many symbiotic bacteria that aid in the breaking down of wastes to extract some small amounts of nutrients. Some bacteria digest food and produce important vitamins and amino acids. Bacteria in the intestines are essential for proper digestion.

19. The Digestive System and Homeostasis Homeostasis is the balance our body maintains to function properly. Recall that nutrients from the food are absorbed in the small intestine. The digestive system must be functioning properly for this absorption to occur. These nutrients are necessary for other body systems to maintain homeostasis. For example, the blood in the circulatory system absorbs the products of digestion. The blood carries the nutrients to all other body systems providing them with materials that contain energy.

20. Common Ailments and Disorders of the Digestive System Gastroesophageal reflux disease (GERD) is a condition in which the acid from the stomach enters the esophagus this is also referred to as heartburn .

21. Common Ailments and Disorders of the Digestive System Gastritis or ulcer is a sore or inflammation in the lining of the stomach that is mostly caused by the bacteria, Helicobacter pylori. It causes pain and discomfort in the lower part of the stomach. It could be an acute or chronic condition.

22. Common Ailments and Disorders of the Digestive System Diarrhea is not a disease, but a symptom characterized by the frequent passage of stools. It may be caused by contaminated food and water or an intestinal disorder like the irritation of the colon. If you have diarrhea , you must drink a lot of water to replenish the water that has been lost by the body.

23. Common Ailments and Disorders of the Digestive System Indigestion is a type of discomfort felt along the upper part of the abdomen. This happens when a person eats too much or too quickly. It can be avoided by eating slowly and regularly.

24. Common Ailments and Disorders of the Digestive System Flatulence is caused by a buildup of gas in the abdomen when you eat quickly and swallow large chunks of food without properly chewing it. Stress can also aggravate flatulence which can cause discomfort and belching.

25. Common Ailments and Disorders of the Digestive System Constipation is when you cannot move your bowels regularly and have difficulty moving them out. You are constipated. This can be remedied by ensuring regular bowel movement, drinking enough water during the day, and eating a lot of fibrous foods which serve as a broom that cleans the digestive tube.