Nutrition & digestive system

1. Nutrition & Digestive System By iTutor.com T- 1-855-694-8886 Email- [email protected]

2. Nutrition Living organisms need food. All food contains nutrients. Nutrients are substances that provide the energy and materials needed for growth, repair and maintenance of cells and regulation. Nutrition is the process by which organisms get food and break it down so it can be used.

3. Nutrition Nutrients include: Proteins Carbohydrates Fats Vitamins Minerals Water Water and minerals are inorganic nutrients which must be obtained from the environment. Minerals are chemical elements that organisms need for normal functioning.

4. Energy Content of Food Energy is provided by the chemical breakdown of CHO, fats and proteins. The calorie is the unit used to measure energy content of food. Calorie is defined as the amount of heat needed to raise the temperature of 1 gram of water 1 o C.

5. Nutrients Humans need the 6 basic nutrients These nutrients are obtained by eating a healthy diet from the 4 major food groups: Grains and grain products (G & GP) Dairy and dairy products (D & DP) Fruits and vegetables (F & V) Meats and alternates (M & A)

6. Nutrients Along with the 6 nutrients, humans need fibre. Fibre is made of cellulose and other indigestible materials found in the cell walls of fruits, vegetables and grains. Fibre stimulates the muscles of the digestive system to keep foods moving through it.

7. The life process of nutrition consists of two parts Ingestion: Taking food into the body (eating ). Digestion: Breaking down food into smaller particles and absorbing them into the body. Nutrition

8. Food is broken down into smaller pieces. Proteins , starches, and fats, are too big to diffuse through cell membrane. Amino acids, simple sugars, glycerol, and fatty acids are absorbed by the body and transported to cells. Digestion

9. Digestion

10. Mechanical digestion: Physical breakdown of food. Chewing, grinding and mixing food with mouth, tongue and teeth . Chemical digestion : Chemical breakdown of food using enzymes, bile, and hydrochloric acid (HCl). Digestion

11. The digestive system is a group of organs that takes in and digests food, and eliminates solid wastes. Digestive system

12. Digestive System Structure and Function Digestive system is made up of the following organs: Mouth Pharynx Epiglottis Esophagus Stomach Small intestine Large intestine Rectum Anus

13. Accessory Organs : Important in digestion, but food does not pass through these organs. Liver Gall bladder Pancreas Digestive System Structure and Function

14. Copyright reserved.  2012 The E Tutor

15. Tracing Toast Mouth Pharynx Epiglottis Esophagus Stomach Duodenum Jejunum Ileum Cecum Ascending colon Transverse colon Descending colon Sigmoid colon rectum Anus Feces Toast Tracing a piece of toast through the alimentary canal Structure and Function

16. Structure and Function Mouth The mouth is also called the oral cavity. Food is taken into the mouth and chewed with the assistance of the cheek muscles . Tongue and teeth function in mechanical digestion (chewing of food). Process of chewing is called mastication. Various tooth types (molars, incisors) make chewing more efficient. Tongue helps mix food with saliva.

17. Structure and Function The Tongue Manipulates material inside mouth Base of tongue extends to pharynx Primary functions: Mechanical processing by compression, abrasion, distortion. Manipulation to assist in chewing and to prepare material for swallowing. Sensory analysis by touch, temperature, taste receptors.

18. Structure and Function Salivary Glands Parotid Submandibular sublingual Submandibular gland Parotid gland Tongue Tooth Sublingual gland

19. Structure and Function Salivary Secretions Parotid glands Salivary amylase B reaks down starch so it can be absorbed by digestive tract. Submandibular and sublingual glands Secretion contains less enzymes but more buffers and mucus. All 3 release saliva during eating Saliva increases pH Goes from 6.7 to 7.5

20. Structure and Function

21. Stages of Swallowing Oral phase Compression of bolus against hard palate Tongue retracts Forces bolus into pharynx Elevates hard palate Only phPrevents bolus from entering nasopharynx. Pharyngeal phase Bolus in contact with sensory receptors Initiates swallowing reflex Larynx elevates, epiglottis folds (protects glottis) Contraction of pharyngeal muscles forces into esophagus.

22. Stages of Swallowing Pharynx Muscular tube about 5 inches long in adults Also known as the throat Transmits food into the esophagus The epiglottis (a flap of tissue) covers the trachea to prevent food from entering the larynx during swallowing which causes choking.

23. Stages of Swallowing

24. Stages of Swallowing Esophageal phase Bolus enters esophagus Peristalsis Approach to stomach opens lower esophageal sphincter 9 seconds from oral cavity to stomach

25. Stages of Swallowing Esophagus Muscular tube about 9 to 10 inches long in the adult that contracts rhythmically ( peristalsis ) to propel food toward the stomach. Contains a group of muscles called the lower esophageal sphincter that closes off the entrance to the stomach to prevent reflux of food, emesis or regurgitation (vomiting).

26. Stages of Swallowing

27. The Stomach The stomach is a thick-walled, muscular sac where food is stored temporarily. The mechanical breakdown of food and partial digestion of proteins occur here. Food is broken down mechanically by contractions of the muscular stomach walls. Food is churned and mixed with acidic gastric juice secreted by glands in the stomach wall.

28. Four primary functions Temporary storage of ingested food Mechanical breakdown of resistant materials Breaking chemical bonds in food materials Acids and enzymes Production of intrinsic factor Necessary for absorption of vitamin B 12 Ingested materials mix with secretions of glands Product is highly acidic soupy mixture Product called chyme (pyloric sphincter regulates flow into small intestines) The Stomach

29. The Stomach

30. The lining of the stomach contains 2 types of glands: Pyloric glands- secrete mucus which covers the stomach lining and protects it from being digested Gastric glands- secrete gastric juice which has a pH of 1.5 – 2.5 (due to its high [HCl]) HCl kills most of the bacteria swallowed in food Gastric juice also contains pepsin , a digestive enzyme, that breaks down proteins into short chains of amino acids call polypeptides The Stomach

31. The salivary amylase, released in the mouth, continues to digest starches in the stomach. Eventually, the low pH of the acid in the stomach inactivates the enzyme and starch breakdown stops. When the stomach is empty, there is little gastric juice present. When food is eaten, the flow of gastric juice increases. The Stomach

32. Liquids pass through the stomach in 20 minutes or less. Solids must be turned into chyme , a thin, soupy liquid. The chyme passes in small amounts at a time through the pyloric sphincter , the ring of muscle that connects the stomach to the small intestine. The stomach will empty 2-6 hours after a meal. Hunger is felt when an empty stomach is churning. The Stomach

33. The Small Intestine

34. The Small Intestine About 6.5 meters long; 2.5 cm in diameter Food leaves the stomach through the pyloric sphincter Small Intestine consists of 3 parts: Duodenum (shortest of the 3 sections- 25 cm) Jejunum Ilium Most chemical digestions takes place in the S.I. Following digestion, simple sugars, amino acids, vitamins, minerals and other substances are absorbed

35. Absorption takes place through the wall of the small intestine into the blood vessels of the circulatory system . Fatty acids and glycerol are absorbed into the lacteals , vessels of the lymphatic system. Many factors allow the Small intestine to be well suited for absorption:- Very long Lining has many folds Lining is covered with millions of finger-like projections called villi. Epithelial cells that make up the intestinal lining have brush borders The Small Intestine

36. Duodenum Stomach Jejunum Cecum Appendix Ileum The Small Intestine

37. The S.I. is in constant motion when food is present. These peristaltic movements have four main effects: They squeeze chyme through the intestine. They mix the chyme with the digestive enzymes present in the small intestine. They break down food particles mechanically. They speed up absorption of digestive end products by bringing the intestinal contents into contact with them intestinal wall. The Small Intestine

38. The Large Intestine

39. Undigested and unabsorbed materials pass from the Small Intestine through a sphincter into the Large Intestine . The Large Intestine is about 1.5 meters long and 6 cm in diameter. Digestion does not occur here, but most of the water reabsorption from food mass does Water is mixed with food as it moves through the digestive system. Normally, ¾ of the water is reabsorbed. Reabsorption in the Large Intestine allows the body to conserve water. The Large Intestine

40. L.I. also absorbs vitamins produced by intestinal bacteria living in the L.I. The vitamins are absorbed with the water from the food mass. The L.I. is important in the removal or undigested and indigestible material from the digestive tract. Ex. Cellulose, large quantities of bacteria, bile, mucus, worn-out cells from the digestive tract. This material becomes feces or stool. “Poo” is stored in the last part of the L.I., rectum and passed through the anus. The Large Intestine

41. Ascending colon Rectum Anal canal Sigmoid colon Vermiform appendix Cecum Ileocecal valve Transverse colon Ileum Descending colon The Large Intestine

42. Liver Located in the right quadrant of the abdominal cavity . Divided into right and left lobes. Converts food nutrients into usable substances. Secretes a yellowish-brown to greenish substance called bile which is stored in the gall bladder. Stores glucose in the form of glycogen. Secretes bilirubin , a bile pigment that is combined with bile and excreted into the duodenum. Liver

43. Liver Inferior vena cava Left lobe Right lobe

44. The End