GI Journey

Ode to the Grapefruit

Almost everyday lately I have enjoyed the sweet juicy goodness of a grapefruit. After peeling it I bite into one of the slices with my teeth, using my lips and mouth to keep the juices from exploding everywhere. Thus begins the mastication and ingestion of my food. My tongue and salivary glands go to work on the grapefruit section initiating the mechanical digestion process. The papillae on my tongue and the smell of its citrusy aroma allow me to experience such delight during this process. In the meantime, the section of grapefruit is being made into a little ball or bolus to be propelled down the esophagus – the process of deglutition or swallowing.

Once my delicious grapefruit hits the stomach many hormones and enzymes go to work on it. Chemical digestion is now included with the mechanical digestion in the stomach. Waves of peristalsis pass through the stomach churning the grapefruit mixing it with gastric juices making it into a thick soup consistency called chyme. Once it is ready the pyloric sphincter relaxes and allows the chyme to head into the small intestines, starting with the duodenum. In the 3.5m of small intestines the nutrients and water from this amazing food is absorbed into my body – including Vitamin A and C and lycopene (a carotenoid pigment and antioxidant) and the soluble fiber that is found in grapefruit. The bile from the liver and gall bladder come into play here and help my body to absorb the fat-soluble Vitamin A and lycopene. The water soluble Vitamin C from the grapefruit is passively absorbed with water through the intestinal walls.

As it makes its way through the small intestine giving my body lots of good heart healthy nutrients it becomes a more porridge like chyme (of course this includes the other stuff I ate for lunch too that I didn’t mention) and enters the large intestine through the ileocecal valve.. This valve opens and the cecum relaxes during the gastrocolic reflex. The last of the water, electrolytes and vitamins are absorbed here in the colon. Mucus is secreted to help with excretion of this final product. Colonic peristalsis helps move the chyme, now feces, onto the rectum and anal canal. The internal anal sphincter relaxes giving me the urge to allow it to pass through the external anal sphincter also. But, luckily, since I’m on the bus, the external sphincter is under conscious control and I can wait until I get home to eliminate the waste from my grapefruit – the fiber from which will help this particular waste be easily eliminated.

disclaimer: don't worry, I'm not actually writing this stuff just for my blog (although that would probably be pretty cool) this was another class assignment :)