Digestion, Absorption, and Transport

Chapter 3

Chapter Summary

            The gastrointestinal tract is a flexible muscular tube that prepares nutrients for absorption. Food enters the mouth, where it is reduced to a coarse mash. Peristalsis passes the bolus through the esophagus to the stomach. The stomach retains the bolus, adds water, and grinds it to a suspension of small particles. The semiliquid mass (chyme) passes to the small intestine where it is further broken down. Various glands and organs work together to secrete digestive juices containing hormones and enzymes that help in breaking down foods to absorbable units. Undigested and unabsorbed nutrients pass through the large intestine to be eliminated.

            Muscular actions of digestion include peristalsis, the motions of the circular and longitudinal muscles of the stomach, segmentation, and sphincter contractions. 

            Nutrients absorbed through the microvilli of the small intestine travel to one of two systems - the bloodstream directly or the lymphatic system. Once inside the vascular system, nutrients travel freely and can be used by any cells in the body.

            Details of the gastrointestinal system are regulated by the endocrine (hormone) and nervous system. PH levels, sphincters, and digestive and enzymatic secretions help in making the digestive tract responsive to conditions in its environment. A healthy digestive tract will help to promote proper functioning of the system. Balance, variety, moderation and adequacy of the diet promotes optimal utilization of foods consumed.

            Highlight 3 reviews common digestive problems. Choking may require use of the Heimlich maneuver. Serious vomiting can cause fluid and electrolyte imbalances. Diarrhea, characterized by frequent and loose stools, requires rest and fluid replacement. Constipation, although generally not serious, may reflect a need for lifestyle changes. Belching and gas is more of a complaint than a serious problem. Heartburn and "acid indigestion" is painful and may be caused by different factors, thus the treatments vary. Ulcer treatment includes seeking medical advice and avoiding foods and beverages that cause difficulties. Many of the common digestive problems reflect hurried lifestyles rather than any particular foods eaten.

Chapter Outline                                                          

I.           Digestion                                                            

A.       Anatomy                                                   

1.        Mouth                    

2.        Esophagus/stomach         

3.        Small intestine              

4.        Large intestine (Colon)      

B.       Muscular Actions                                             

1.        Peristalsis            

2.        Stomach action         

3.        Segmentation           

4.        Sphincter contractions            

C.       Secretions of Digestion                              

1.        Saliva                 

2.        Gastric juice              

3.        Pancrestic juice and intestinal enzymes  

4.        Bile                 

5.        Protective factors            

D.       Final Stages                                            

II.          Absorption                                      

A.       Anatomy                                                   

B.       Intestinal Cells

1.        Cell capabilities

2.        Specialization

3.        Food combining “myth”

4.        Nutrient transport preparation                  

III.        The Circulatory Systems

A.       Vascular System                                           

B.       Lymphatic System                                           

IV.      Regulation of Digestion and Absorption                                              

A.       Hormones and Nerve Pathways

1.        pH level of stomach               

2.        Pyloric sphincter

3.        Alkaline pH              

4.        Pancreatic enzymes         

5.        Presence of fat          

6.        Intestinal motility              

B.       System at Its Best

V.       Highlight: Common Digestive Problems

A.       Choking                                                     

B.       Vomiting                                                    

C.       Diarrhea                                                                       

D.       Constipation                                            

E.       Belching and Gas                                         

F.        Heartburn and “Acid Indigestion”               

G.       Ulcers

The University of Texas at Brownsville & Texas Southmost College
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