Fantastic Voyage [hs130, section: ____ ]

Today, on the twentieth of August, I will take you on a trip inside the gastrointestinal tract, and beyond in the human body to observe the process of digestion and excretion. As simple as it may seem, this process is more than just moving down a hollow tube. To understand this more deeply, let's begin our journey!

REVIEW OF THE VIDEO TAPE:

Being reduced to eight microns in a hamburger holds the possibility of being chewed, grinded and dissolved in gastric acid. Even though I used special shield defenses, the slight possibility can still be a scary thought. Despite the risk, I felt motivated enough to allow myself to be amazed by the human body.

In about a moment, I was in the mouth of a 55-year-old man. Mixed with me, were fries, meat, lettuce, cheese, burgers and bear. Staying away from the teeth was a difficult job since the tongue was constantly working to bring me and other contents to teeth. The teeth, mainly the molars, were busy grinding and crushing the food, breaking them into smaller pieces. With every bite, a gush of secretions was produced by minute pores at different places in the oral cavity. These secretions enveloped the food, making them smoother. They also seemed to help in breaking them into smaller pieces. The major enzyme produced by these salivary glands is the amylase. This helps break down proteins, such as the meat and lettuce in this elderly man's diet. (Barrett et al., 2010)

Eventually, the food and I were rolled into a ball, or a bolus, and pushed to the back by the tongue and squeezed against the oral part of the pharynx. At this brief moment, I experienced an important reflex, called swallowing. This process is mediated by the involvement of 55 muscles of the oropharyngeal, laryngeal and esophageal regions, 6 cranial nerves, and 2 cervical nerve roots. My extra vigilance helped me appreciate the two sets of muscles that worked concomitantly to allow this man to swallow his bite. One set of muscles were involved in keeping the mouth closed, and the other helped create positive pressure...

(Leonard & Kendall, 2008)
Once, in the pharynx, the remaining part of the swallowing process happened pretty quickly. As one set of muscle contracted, the other relaxed, propelling us lower down into the esophagus. These muscles are the longitudinal, namely, the stylopharyngeus, salpingopharyngeus, palatopharyngeus, and the palatothyroideus, and the circular. (Hansen, Koeppen & Netter, 2002) With the contraction of the former group, the pharynx was squeezed laterally, shortening the pharynx and assisting the opening of the upper esophageal sphincter. (Barrett et al., 2010)

At this point in time, the opening to the trachea was closed by the epiglottis. The epiglottis is a muscle that acts like a gateway, directing the food to the esophagus and protecting the airway from aspiration. As the man sipped his bear, it trickled down past us much faster, making me slightly envious of its faster transit time. (Barrett et al., 2010)

The ride through the esophagus was nothing like a water slide. Each muscular contraction squeezed us against its walls and forcefully pushed us lower down. This squeeze-push cycle was strongest at the lower esophageal sphincter, after which we dropped down into the stomach. Reaching the stomach made me feel like an unwelcomed guest. The squeeze-push cycle started just as soon as we reached, but this time, it did not push us further down. The stomach was sealed at the lower end by the pyloric sphincter. A gush of acidic secretion bathed us and almost completely dissolved my fellow food particles, especially the protein molecules. Some particles, such as the starch molecules from the bread component, were larger than the others. At the end of the gastric phase, the food particles resembled a paste, and I was mixed in this slime. (Barrett et al., 2010)

It was interesting to see the work going on in the stomach. Some glands in the stomach were secreting liquid secretions which are supposed to contain acid and the enzyme pepsin, responsible for protein digestion. On the other hand, some glands were secreting a thicker…