Gastrointestinal Anatomy and Physiology: The Essentials

Intestinal fluid secretion affects the viscosity of the mucous-gel layer, which can alter the drug's cellular uptake at the site of action.

“Moreover, intestinal fluid secretion affects the viscosity of the mucous-gel layer,81,93 which can alter the drug’s cellular uptake at the site of action.”

pH is influenced by fluid-to-matter ratios, which can potentially alter drug absorption and delivery, especially in the lower gastrointestinal tract.

“The pH is influenced by fluid-to-matter ratios, which can potentially alter drug absorption and delivery, especially in lower GIT.”

Controlling fluidity is crucial for gastrointestinal function.

“Controlling fluidity is crucial for gastrointestinal function.81”

Diet can have a large impact on gastrointestinal free fluid volume, bile salts, and digestive enzyme levels.

“For instance, diet can have a big impact on the GIT free fluid volume, bile salts, and digestive enzyme levels.81”

The daily water balance in a healthy adult human gastrointestinal tract is determined by secretion from saliva (1.5 L), gastric juice (2.5 L), pancreatic and other intestinal components (~2.5 L), and absorption from the small and large intestine (7 L and 1.9 L, respectively).

“The daily water balance in a healthy adult human GIT is determined by the secretion from saliva (1.5 L), gastric juice (2.5 L), pancreatic, and other intestinal components (~2.5 L), and absorption from the small and large intestine (7 L and 1.9 L, respectively).81”

Gastric transit time can vary from 0 to 6 hours based on fasted or fed state.

“The transit time in gastric can vary from 0 to 6 h based on fast/fed state,81”

The major sites of enzymes involved in food digestion are the mouth (salivary amylase) and stomach (pepsin).

“The major site of the enzymes that are involved in food digestion is mouth (salivary amylase), stomach (pepsin).81”

The fluid environment allows digestive enzymes to contact food, aids transit of intestinal contents without damaging the epithelial lining, and facilitates nutrient and drug solubility and absorption.

“The fluid environment allows digestive enzymes to contact with food, and this aids in transit the intestinal contents along the GIT without damaging the epithelial lining and it facilitates the nutrients and drugs solubility and absorption.81”