Chapter 6 Digestion Absorption Metabolism The Organs and Functions of Digestion Digestion occurs in the digestive or gastrointestinal GI tract Consists of o Series of organs o Complex outer layers of muscles o Inner mucosal layer of glands and absorptive cells Starts with mouth and ends with anus Components of GI Tract Identify the components of the gastrointestinal tract The digestive tract o Mouth o Esophagus o Stomach o Small intestine o Large intestine o Rectum Other organs assist o Salivary glands o Liver o Pancreas o Gallbladder The Organs and Functions of Digestion Define digestion and absorption Main functions of GI tract o Digestion Move food through GI Before getting it into the body breakdown of food to smaller compounds units Primary MAIN not first site for digestion is the small intestine o Absorption Cross lining of the intestine to enter the body Crosses the intestinal wall and gets into the body The period of time it takes food to travel the length of the digestive tract is called transit time when we digest food we move it through the GI tract progressively moves from the mouth all the way down move appropriately appropriate digestion and absorption o Too slow result in constipation o Too fast diarrhea The Organs and Functions of Digestion Food moved through GI tract via muscular constrictive movement o Known as peristalsis constriction relaxation constriction relaxation relaxations that moves the food through starts from first part of GI called esophagus Digestion is a combination of mechanical and chemical processes breaking down products into smaller units to be absorbed Discuss the differences between mechanical and chemical digestion and list an example of each in the mouth stomach and small intestine Two forms of digestion Mechanical o Chewing mixing and peristalsis Chemical o Mixing the food with various gestational GASTROINTESTINAL secretions and enzymes help reactions occur quicker of the GI tract o Digestive enzymes are meant to breakdown Helps break the larger macronutrients compounds into smaller forms that can be absorbed Undigested or unabsorbed substances moved through GI tract and ultimately to elimination by defecation The Organs and Functions of Digestion learning objective KNOW STRUCTURE OF GI TRACT INCLUDES the sphincters Name the location of the 3 sphincters discussed in this lecture and the purpose of each Components of GI tract separated by circular muscles called o o o o Sphincters help compartmentalize portions of the GI tract these muscles will constrict relax constrict relax 3 in particular Lower esophageal sphincter Pyloric sphincter Ileocecal valve Purpose of sphincters one way doors Prevents food from flowing backward Examples of when sphincter does not work properly Heartburn burning sensation in chest when lower esophageal sphincter doesn t close completely Vomiting Digestion Must Occur Before Absorption o Once food is broken into its smallest units it is ready to be absorbed into the body into the blood and finally into the cells where it can be used for energy or stored o Once it s absorbed used for energy Macronutrients energy yielding o Carbohydrates o Protein o Fat o Some food components do not need to be digested to be absorbed o Water macronutrient but not energy yielding o Vitamins o Minerals o Small molecules such as glucose Sum of the Parts The Process of Digestion The Sum of the Parts The Nose o Taste is 80 smell the nose ties into taste List the 5 taste sensations o Five primary tastes o Salty o Sweet o Sour o Bitter o Umami savory o There is a strong connection between our brain digestive system and sense of smell o The sight smell and thought of food can trigger the release of digestive secretions and enzymes The Sum of the Parts Mouth and Esophagus Describe the process of digestion starting in the mouth and ending at the large intestine o Digestive process begins in the mouth o Mechanical digestion Chewing Identify the digestive enzymes discussed in this lecture with the location it is secreted in the GI tract and the macronutrient it is responsible for digesting o Chemical digestion o Saliva is added to help lubricate food hard to swallow if not moistened appropriately o In saliva are digestive enzymes Enzymes are released Salivary amylase starts the digestion of the macronutrient carbohydrates o Develop nice moist Bolus formed the tongue help move food around and initiate swallowing The tongue helps with the mixing of food o Helps initiate swallowing LEARNING OBJECTIVE identify various digestive enzymes that is discussed in class and to know what they re responsible of digesting breaking apart The Sum of the Parts Stomach We swallow and the food starts traveling down the esophagus What moves the food down to the esophagus is peristalsis Peristalsis moves food down to the esophagus Esophagus is connected to the stomach The stomach is a J shaped sac that mixes food with gastric secretions and assists with digestion The esophagus is separated from the stomach by the o o o o o o o o Lower esophageal sphincter opens up and closes again Once food enters the stomach the cells of the stomach start producing gastric juices Hydrochloric acid HCL Mucus Pepsinogen The hormone gastrin Lower esophageal sphincter at the lower portion esophagus opening to stomach Bottom portion of stomach first part of the small intestine called the duodenum that is known as pyloric sphincter shuts to trap food in stomach o Lower esophageal sphincter shuts o Pyloric sphincter shuts to trap food in the stomach The stomach can act as a reservoir Keeps food in long enough to get a mix with gastric juices Three layers of muscle that face different directions all this churny motion that occurs in the stomach that is part of mechanical digestion The Sum of the Parts Stomach REVIEW List the functions of gastric secretions in the stomach for digestion o o o o o o o o o o o o o o o o FIND TABLE IN TEXTBOOK LEARNING OBJECTIVES Go back to know the functions of the gastric juices MUCUS Purpose it protects the lining of the stomach from the HCl So once we start eating we start secreting more HCl To keep the lining from being irritated by HCl we secrete mucus Do not have that ability in the esophagus Reaches esophagus causes heartburn HCl Functions denatures proteins denaturing changes shape and can unfold a protein also activates the enzymes PEPSIN and lingual lipase Also assists with neutralizing bacteria part of immune response INTRINSIC FACTOR Correlate