The Fantastic Voyage Part II
Hello everyone, we are back for another exciting adventure, this one a little more appetizing than the last! Today’s Fantastic Voyage will follow the path of one tasty hamburger, some fatty french fries, and a cold and sweet root beer through a fifty-five year old man’s digestive, circulatory and urinary systems. I will be narrating all structures and functions as we explore; some imagery may be a little graphic, so hold on tight if you have a weak stomach!
Here we commence our journey straight into the mouth of our hungry friend, making our descent into the first part of this nine meter ...view middle of the document...
You can feel the strong contraction of the walls as the stomach continues to break down the heavy meal while the glands begin to release a highly acidic concoction of enzymes, hydrochloric acid and mucus to digest proteins and fats into their respective building blocks, amino acids and fatty acids (Cleveland Clinic, 2014). This creates a soupy consistency called chime, which once partial digestion is complete, the smooth muscle fibers of the pyloric sphincter relax and allow us to continue to the first part of the small intestine.
We are now entering the duodenum, which continues the digestion process. The mucus lining of the intestines contains thousands of microscopic glands that secrete intestinal digestive juices such as amylase, bile, and a combination of intestinal and pancreatic enzymes (“Digestive System,” 2014). The amylase is secreted from the neighboring pancreas and it’s alkalinity helps further digest carbohydrates. The bile you see around us comes from the liver and gallbladder and it works to emulsify the fat and allow it to mix with water (“The Human Digestion,” 2014). The pancreatic and intestinal enzymes are working hard to finish breaking down proteins into amino acids. Get comfy and have a seat-we will be here for a while considering the small intestines measure approximately seven meters (Thibodeau & Patton, 2008). Now that the nutrients have been reduced to their basic building blocks, we continue down the jejunum and ileum, where more nutrient absorption takes place. If you look very closely at the lining of the walls around us, you will notice it is not really as smooth at it looks. The walls are sorted into many tiny circular folds called plicae, which then each of these folds can be further inspected to find millions of villi, tiny hair-like fingers filled with a complex net of capillaries (“Digestive System,” 2014). This complex structure allows for an increased surface area where the capillaries aid in the absorption of digested nutrients. Now that we are at the distal ileum, we will be crossing the mucosal membrane along with all of the nutrients and here we find our way into the superior mesenteric vein which as you would have guessed, drains blood from the small intestine.
The superior mesenteric vein lies just behind the pancreas and combines with the splenic vein to form the hepatic portal vein which is how we will be entering the liver. The liver takes up the entire upper right quadrant of the abdominal cavity, well into the left side. It is the largest exocrine gland, meaning the cells in the liver secrete bile into ducts that drain outside of the liver (Thibodeau & Patton, 2008). As we continue our venous pathway to the heart, we are now entering the hepatic veins which drain into the inferior vena cava. Notice that now we are following the flow of hepatic portal circulation, which means before returning to the heart we will have to travel through a second capillary bed in the liver where the high...