Principles structure

Structural principles are grounded in the notion that biological units have characteristic and defining size, shape position and character, and are connected via neurovascular bundles, ducts and lymphatics to the system at large.  

The size of gallbladder allows it to store only 50-70ccs of bile while the liver produces and delivers 500-1000ccs of bile perday.  If we approach the gallbladder with simple minded mathematics we are puzzled since if it empties its contents at three meals a day, it would empty a total of 210 ccs per day when the juice gates of Oddi are open.  One would have expected the gallbladder volume using the “three meals three empties” per day concept to have been in the order of  200ccs ie three times its volume of about 65ccs.  Where does the remaining volume of approximately 700ccs of bile go? We will attempt to unravel this puzzle as the module progresses.

The pear shaped form and position of the gallbladder has rational design.  The fundus with the largest diameter and the body with the  most volume are relatively inferior so that they act as a storage dump when the patient is in the upright position.  Additionally they act as a pump that has to process the bile for three major deliveries per day.  Unlike the heart it has the additional function to concentrate its product, and therefore it has to separate bile that has already been processed and new bile that is freshly delivered from liver.  “Old” concentrated bile is stored in the fundus and “new”  bile is located in the infundibulum.  As we progress with this module we will try and expand this concept.

The character of the gallbladder is based in its wall and its contents.  As a musculomembranous sac it has been designed with a 3 layered wall that has muscular elastic and absorbtive properties.  The lumen houses bile which is a homogeneous, relatively clear, and limpid fluid.  Bile fresh from the liver has a specific gravity that ranges between 1.010 – 1.030 being slightly greater than water, and after it has been concentrated by the gallbladder the SG is usually in the 1.040 range. (Practical Physiological Chemistry)

The connections of the gallbladder to the rest of the gastrointestinal tract are via the cystic duct which plugs into the hepatic duct to form the common bile duct. Its blood supply is via the cystic artery, venous drainage via the cystic veins, and lymphatics via hepatic system.  Parasympathetic and sympathetic systems connect it to the autonomic system, while the hormonal control is via intestinal polypeptides and CCK

The parts of the gallbladder include the fundus, body neck, and cystic duct. It has a serous capsule on its free wall.