Describe the
physiolgy of digestion of
various types of food
the human system
Answers
Answer:
Digestion Definition
The process by which food is broken down into simple chemical compounds that can be absorbed and used as nutrients or eliminated by the body is called digestion.
Explanation:
1. Ingestion
The entry of food into the alimentary canal through the mouth is called ingestion. Simply put, the act of eating and drinking is called ingestion.
2. Propulsion
Propulsion refers to the movement of food through the digestive tract.
It includes both the voluntary process of swallowing and the involuntary process of peristalsis.
Peristalsis consists of sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food along.
These waves also play a role in mixing food with digestive juices. This both mixes and moves the contents along the alimentary tract.
Also, the act of swallowing, the last voluntary act until defecation, is an example of propulsion.
3. Mechanical Digestion
Digestion is a purely physical process that does not change the chemical nature of the food.
Instead, it makes the food smaller to increase both surface area and mobility.
It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with saliva.
The mechanical churning of food in the stomach serves to further break it apart and expose more of its surface area to digestive juices, creating an acidic “soup” called chyme.
Segmentation, which occurs mainly in the small intestine, consists of localized contractions of circular muscle of the muscularis layer of the alimentary canal. These contractions isolate small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents.
By moving food back and forth in the intestinal lumen, segmentation mixes food with digestive juices and facilitates absorption.
4. Chemical digestion
Chemical digestion of food by enzymes present in secretions produced by glands and accessory organs of the digestive system.
In chemical digestion, starting in the mouth, digestive secretions break down complex food molecules into their chemical building blocks (for example, proteins into separate amino acids).
These secretions vary in composition but typically contain water, various enzymes, acids, and salts. The process is completed in the small intestine.
5. Absorption
This is the process by which digested food substances pass through the walls of some organs of the alimentary canal into the blood and lymph capillaries for circulation around the body.
It takes place primarily within the small intestine.
There, most nutrients are absorbed from the lumen of the alimentary canal into the bloodstream through the epithelial cells that make up the mucosa.
6. Elimination
Food substances that have been eaten but cannot be digested and absorbed are excreted by the bowel as feces.
Physiology of Digestion
In the Oral Cavity
After ingestion, the food is chewed and mixed with saliva, which contains enzymes that begin breaking down the carbohydrates in the food plus some lipid digestion via lingual lipase.
Saliva contains the enzyme amylase that begins the breakdown of complex sugars, reducing them to the disaccharide maltose.
Chewing by the teeth increases the surface area of the food and allows an appropriately sized bolus to be produced.
Food leaves the mouth when the tongue and pharyngeal muscles propel it into the esophagus.
Pharynx and Esophagus
The presence of the bolus in the pharynx stimulates a wave of peristalsis
By slowing the emptying rate of the stomach, the contents of the duodenum become more thoroughly mixed with bile and pancreatic juice.