Gastrointestinal Tract Water and Electrolytes Transport
• REGULATION of FLUID TRANSPORT in GI tract is CRITICAL for NORMAL INTESTINAL FUNCTION
• The REGULATION of ELECTROLYTE BALANCE is therefore a KEY PRINCIPLE to UNDERSTANDING INTESTINAL
FLUID BALANCE IN HEALTH AND DISEASE
• In HEALTHY state, only 100mL of FLUID EXITS the GI tract (via stool) PER DAY
• ECF contains mainly Na+; ICF contains mainly K+
• WATER DISTRIBUTION DEPENDS ON OSMOLARITY OF ECF AND ICF
• Water and electrolytes in GI tract lumen INTERCHANGE with ECF
• After eating (postprandial period)- high content of nutrients in GI tract lumen
• Na+ ENTER THE CELLS VIA COUPLED CO-TRANSPORTERS WITH NUTRIENTS
SUCH AS GLUCOSE; AMINO ACIDS; FATTY ACIDS; BILE ACIDS
• Na+ gradient created by the electrogenic Na+/K+ pump creates Na+ electrochemical
gradient between cells and lumen --> allows Na+ coupled co-transport from lumen
into cell
• Several mechanisms for absorption, but the primary one involves COUPLED TRANSPORT to MOVEMENT of GLUCOSE,
AMINO ACIDS AND FATTY ACIDS after a meal
• Na+/glucose TRANSPORTER is the most EFFICIENT MECHANISM for Na+ ABSORPTION
• It remains intact even in infectious diseases- induced diarrhoea
• DIORALYTE = is essential for the efficacy of oral rehydration solution
• The ACTIVITY of the Na/H (NHE) ANTIPORT
• Na+ ABSORPTION into enterocytes in EXCHANGE for EXTRUSION H+ into small intestine
lumen
• H+ SECRETIONS contribute to the GENERATION and MAINTENANCE of the MICRO
Integration of Physiological Systems Page 1
• REGULATION of FLUID TRANSPORT in GI tract is CRITICAL for NORMAL INTESTINAL FUNCTION
• The REGULATION of ELECTROLYTE BALANCE is therefore a KEY PRINCIPLE to UNDERSTANDING INTESTINAL
FLUID BALANCE IN HEALTH AND DISEASE
• In HEALTHY state, only 100mL of FLUID EXITS the GI tract (via stool) PER DAY
• ECF contains mainly Na+; ICF contains mainly K+
• WATER DISTRIBUTION DEPENDS ON OSMOLARITY OF ECF AND ICF
• Water and electrolytes in GI tract lumen INTERCHANGE with ECF
• After eating (postprandial period)- high content of nutrients in GI tract lumen
• Na+ ENTER THE CELLS VIA COUPLED CO-TRANSPORTERS WITH NUTRIENTS
SUCH AS GLUCOSE; AMINO ACIDS; FATTY ACIDS; BILE ACIDS
• Na+ gradient created by the electrogenic Na+/K+ pump creates Na+ electrochemical
gradient between cells and lumen --> allows Na+ coupled co-transport from lumen
into cell
• Several mechanisms for absorption, but the primary one involves COUPLED TRANSPORT to MOVEMENT of GLUCOSE,
AMINO ACIDS AND FATTY ACIDS after a meal
• Na+/glucose TRANSPORTER is the most EFFICIENT MECHANISM for Na+ ABSORPTION
• It remains intact even in infectious diseases- induced diarrhoea
• DIORALYTE = is essential for the efficacy of oral rehydration solution
• The ACTIVITY of the Na/H (NHE) ANTIPORT
• Na+ ABSORPTION into enterocytes in EXCHANGE for EXTRUSION H+ into small intestine
lumen
• H+ SECRETIONS contribute to the GENERATION and MAINTENANCE of the MICRO
Integration of Physiological Systems Page 1
