Digestive Processes
1.The digestive tract can be viewed as a “disassembly line” in which food becomes less complex at each step of processing and its nutrients become available to the body. The processing of food by the digestive system involves six essential activities: ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
2. Ingestion is simply the process of taking food into the digestive tract, usually via the mouth.
3. Propulsion is the process that moves food through the alimentary canal. It includes swallowing, which is initiated voluntarily, and peristalsis, an involuntary process. Peristalsis (peri = around; stalsis = constriction), the major means of propulsion, involves alternate waves of contraction and relaxation of muscles in the organ walls. Its main effect is to squeeze food from one organ to the next, but some mixing occurs as well. From the time food enters the pharynx, its movement is completely reflexive. In fact, peristaltic waves are so powerful that food and fluids will reach your stomach even if you stand on your head.
4. Mechanical digestion physically prepares food for chemical digestion by enzymes. Mechanical processes include chewing, mixing of food with saliva by the tongue, churning food in the stomach, and segmentation, or rhythmic local constrictions of the intestine. Segmentation mixes food with digestive juices and increases the rate of absorption by repeatedly moving different parts of the food mass over the intestinal wall.
5. Chemical digestion is a series of catabolic steps in which complex food molecules are broken down to their monomers (chemical building blocks). Chemical digestion is accomplished by enzymes secreted by various glands into the lumen of the alimentary canal. The enzymatic breakdown of foodstuffs begins in the mouth and is essentially complete in the small intestine.
6. Absorption is the passage of digested end products (plus vitamins, minerals, and water) from the lumen of the GI tract into the blood or lymph. For absorption to occur, these substances must first enter the mucosal cells by active or passive transport processes. The small intestine is the major absorptive site.
7. Defecation is the elimination of indigestible substances from the body via the anus in the form of feces.
—Marieb, Elaine. Human Anatomy and Physiology. 4th ed. San Francisco: Benjamin Cummings, 1998. Print.
a)a process map
b)a time line
c)a summary
d)an organizational chart
1.The digestive tract can be viewed as a “disassembly line” in which food becomes less complex at each step of processing and its nutrients become available to the body. The processing of food by the digestive system involves six essential activities: ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
2. Ingestion is simply the process of taking food into the digestive tract, usually via the mouth.
3. Propulsion is the process that moves food through the alimentary canal. It includes swallowing, which is initiated voluntarily, and peristalsis, an involuntary process. Peristalsis (peri = around; stalsis = constriction), the major means of propulsion, involves alternate waves of contraction and relaxation of muscles in the organ walls. Its main effect is to squeeze food from one organ to the next, but some mixing occurs as well. From the time food enters the pharynx, its movement is completely reflexive. In fact, peristaltic waves are so powerful that food and fluids will reach your stomach even if you stand on your head.
4. Mechanical digestion physically prepares food for chemical digestion by enzymes. Mechanical processes include chewing, mixing of food with saliva by the tongue, churning food in the stomach, and segmentation, or rhythmic local constrictions of the intestine. Segmentation mixes food with digestive juices and increases the rate of absorption by repeatedly moving different parts of the food mass over the intestinal wall.
5. Chemical digestion is a series of catabolic steps in which complex food molecules are broken down to their monomers (chemical building blocks). Chemical digestion is accomplished by enzymes secreted by various glands into the lumen of the alimentary canal. The enzymatic breakdown of foodstuffs begins in the mouth and is essentially complete in the small intestine.
6. Absorption is the passage of digested end products (plus vitamins, minerals, and water) from the lumen of the GI tract into the blood or lymph. For absorption to occur, these substances must first enter the mucosal cells by active or passive transport processes. The small intestine is the major absorptive site.
7. Defecation is the elimination of indigestible substances from the body via the anus in the form of feces.
—Marieb, Elaine. Human Anatomy and Physiology. 4th ed. San Francisco: Benjamin Cummings, 1998. Print.
a)a process map
b)a time line
c)a summary
d)an organizational chart