Structure of the gastrointestinal tract (GIT)

The GIT consist of three major anatomical regions  

1.    stomach

2.     small intestine include duodenum jejunum &ileum

3.     Large intestine.

The GIT is a hollow muscular tube composed of
four layers of tissue named from the innermost to the outermost as the

1.    Mucosa (The mucosa is the most important to the absorption.

            Because the mucosa of stomach contains many folds→                        ↑absorption

2.    submucosa

3.     muscularis externa

4.     Serosa  

The small intestine is the most important site of drug absorption (Why )?

                   Because small intestine has large epithelial surface area                                                     which contain

                                a) Folds in intestinal mucosa

                                b) Villi

                                c) Microvillus

The large intestine lacks villi, however the large intestine has site for the absorption of drug which has not completely absorbed in the proximal regions of the GIT.