Digestion, Absorption, And Transport Part 1 PDF

10/31/2023 1 DIGESTION, ABSORPTION, AND TRANSPORT Part 1 Dr. Hala Nawaiseh 10/31/2023 2 The Digestive System 1. Human beings breathe, eat, and drink through their mouths. Air taken in through the mouth must go to the lung...

10/31/2023 1 DIGESTION, ABSORPTION, AND TRANSPORT Part 1 Dr. Hala Nawaiseh 10/31/2023 2 The Digestive System 1. Human beings breathe, eat, and drink through their mouths. Air taken in through the mouth must go to the lungs; food and beverages must go to the stomach. The throat must be arranged so that swallowing and breathing don’t interfere with each other.. 2. Positioned below the lungs is the diaphragm, a dome of muscle that separates the upper half of the torso from the lower half. The body needs a passageway that will allow food from the mouth to pass through the diaphragm to reach the stomach below 10/31/2023 3 The Digestive System 3. The contents of the digestive tract should be kept moving forward, slowly but steadily, at a pace that permits all reactions to reach completion. 4. To move through the system, food must be lubricated with fluids. Too much would form a liquid that would flow too rapidly; too little would form a paste too dry and compact to move at all. The amount of fluids must be regulated to keep the intestinal contents at the right consistency to move along smoothly. 10/31/2023 4 The Digestive System 5. For digestive enzymes to work, foods must be broken down into small particles and suspended in enough liquid so that every particle is accessible. Once digestion is complete and nutrients have been absorbed from the GI tract into the body, the remaining waste must be excreted. Excreting all the water along with the solid residue, however, would be both wasteful and messy. Some water must be withdrawn, leaving a solid waste product that is easy to pass 10/31/2023 5 The Digestive System 6. The digestive enzymes are designed to digest carbohydrate, fat, and protein. The cells of the GI tract are also made of carbohydrate, fat, and protein. These cells must be protected against the powerful digestive juices that they secrete. 7. Once waste matter has reached the end of the GI tract, it must be excreted, but it would be inconvenient and embarrassing if this function occurred continuously. Evacuation needs to occur periodically. 10/31/2023 6 The Digestive System Digestive system All the organs and glands associated with the ingestion and digestion of food. Function Of The Digestive System Ingestion. Mechanical breakdown. Digestion ( chemical breakdown). Secretion. Absorption. Excretion. 10/31/2023 7 Anatomy of the Digestive Tract Tract is a flexible muscular tube that extends from the mouth, through the esophagus, stomach, small intestine, large intestine, and rectum to the anus. The human body surrounds the GI tract. The inner space within the GI tract, called the lumen, is continuous from one end to the other. A nutrient or other substance must pass through the GI tract’s wall to enter the body proper; some materials pass through the GI tract without being digested or absorbed. 10/31/2023 8 Anatomy of the Digestive Tract Mouth : The process of digestion begins in the mouth. During chewing, teeth crush large pieces of food into smaller ones, and fluids from foods, beverages, and salivary glands blend with these pieces to ease swallowing. Fluids also help dissolve the food so that the tongue can taste it; only particles in solution can react with taste buds. 10/31/2023 9 10/31/2023 10 10/31/2023 11 10/31/2023 12 Anatomy of the Digestive Tract Pharynx: Short tube that is shared by both the digestive system and the respiratory system. To bypass the entrance to the lungs, the epiglottis closes off the airway so that choking doesn’t occur when swallowing. After a mouthful of food has been chewed and swallowed, it is called a bolus. 10/31/2023 13 Anatomy of the Digestive Tract Esophagus: Hollow muscular tube ( approx. 25 cm long, 2 cm wide). Move food into stomach through peristalsis.. No absorption. 10/31/2023 14 Anatomy of the Digestive Tract Esophagus The esophagus has a sphincter muscle at each end. During a swallow, the upper esophageal sphincter opens. The bolus then slides down the esophagus, which passes through a hole in the diaphragm to the stomach. The lower esophageal sphincter at the entrance to the stomach closes behind the bolus so that it proceeds forward and doesn’t slip back into the esophagus. 10/31/2023 15 10/31/2023 16 Anatomy of the Digestive Tract Stomach A muscular, elastic, saclike portion of the digestive tract that grinds and churns swallowed food, mixing it with acid and enzymes to form chyme. The stomach retains the bolus for a while in its upper portion before transferring it to the lower portion. As the stomach churns and adds digestive juices, the bolus becomes a semiliquid mass called chyme. Then, little by little, the stomach releases the chyme through the pyloric sphincter, which opens into the small intestine and then closes behind the chyme. 10/31/2023 17 Anatomy of the Digestive Tract Small Intestine At the beginning of the small intestine, the chyme bypasses the opening from the common bile duct, which is dripping fluids into the small intestine from two organs outside the GI tract—the gallbladder and the pancreas. The chyme travels down the small intestine through its three segments—the duodenum, the jejunum, and the ileum—almost 10 feet of tubing coiled within the abdomen. 10/31/2023 18 10/31/2023 19 Anatomy of the Digestive Tract Large Intestine (Colon) Absorbs water and minerals; passes waste (fiber, bacteria, and unabsorbed nutrients) along with water to the rectum. Having traveled the length of the small intestine, the remaining contents arrive at another sphincter: the ileocecal valve, located at the beginning of the large intestine (colon) in the lower right side of the abdomen. 10/31/2023 20 Anatomy of the Digestive Tract Large Intestine (Colon) Upon entering the colon, the contents pass another opening. Should any intestinal contents slip into this opening, it would end up in the appendix, a blind sac about the size of your little finger. Normally, the contents bypass this opening, however, and travel along the large intestine up the right side of the abdomen, across the front to the left side, down to the lower left side, and finally below the other folds of the intestines to the back of the body, above the rectum. 10/31/2023 21 Anatomy of the Digestive Tract Large Intestine (Colon) As the intestinal contents pass to the rectum, the colon withdraws water, leaving semisolid waste.The strong muscles of the rectum and anal canal hold back this waste until it is time to defecate. Then the rectal muscles relax ,and the two sphincters of the anus open to allow passage of the waste. 10/31/2023 22 THE END