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Course Objective: Unit 13 – Digestive system – State the four functions and the six steps of the digestive system
Diphyllobothrium Latum, also known as the broad fish tapeworm worm is one of the most common and largest tapeworms to infect a human. Human diphyllobothriasis is caused by the consumption of uncooked or raw fish containing the larval stage. Parasitic infections like this cause physiological problems in the digestive tract and lead to key nutrient deficiencies (MedlinePlus, 2025). The problem is a worldwide issue but is seen to be increasing in areas like Argentina, Russia, and parts of Japan (Dick 2001). The objective is to follow the disphyllobothrium latum through the 6 steps of digestion and the effect on the four functions throughout the infection.
The first step of digestion is the ingestion of food (Unit 13, Slide 8). The conscious act of putting some food into your mouth and taking a bite to eat. This is where the infection begins. As Stated earlier this is most common and even seen increasing in some areas in europe, asia, and south america (Dick 2001). The parasite does not affect this step directly or the function of taking in food, but it is the beginning of the organism’s infection of the digestive tract.
Propulsion is the second step in the digestive system and involves the swallowing and peristalsis of the food through the tract (Unit 13 Slide 8). Most people are familiar with swallowing, but peristalsis is the function of the esophagus, stomach, small intestine, and large intestine to keep the food moving through the system. Although the parasite doesn’t directly impact propulsion or swallowing, the presence of the parasite in the intestines may cause some mild discomfort or a false sense of being full from a meal (Scholz 2009). Propulsion may slow due to pain or discomfort.
Mechanical breakdown is the third step of digestion includes chewing, mixing food with saliva, churning food in the stomach, and segmentation (local constriction of the intestine that mixes food with digestive juices) (Unit 13 Slide 9). Churning and chewing that occurs in the mouth is not directly affected by the infection, but segmentation is. Just as a large tapeworm may interfere with propulsion, it also interferes with bowel motility and irritates the lining of organs.
Digestion is the fourth step of digestion and is a series of catabolic steps that involve enzymes that break down complex food molecules into building blocks (Unit 13, Slide 9). Unlike some parasites, Diphyllobothrium Latum does not release harmful digestive enzymes, but as Dr. Larson described in the parasite lecture in Unit 13, they get cozy. These parasites attach the the walls of the intestines and feast off the nutrients of their host. The small intestine also has the largest surface area of any organ deep within the gut. They have food in a warm, moist, and stable environment. Depending on the nutrient this parasite impairs, the metabolic process may begin to see effects leading to diagnoses like anemia from a B12 deficiency (Scholz 2009).
Absorption is the fifth step in digestion and is the most affected by Diphyllobothriasis. Absorption is the passage of digested fragments from the lumen of the GI tract into blood or lymph (in the small intestines and large intestines) (unit 13 Slide 9). As previously mentioned, the parasite begins to feed off the host, depriving them of critical nutrients, vitamins, and minerals. A key point is that the parasite is interfering with one of the four functions directly: absorbing nutrients. Prolonged infection just means prolonged malnutrition and fatigue that can also have neurological effects over time.
Finally, defecation is expelling the indigestible material from the body. This is often how we figure out if a mammal has a parasitic infection, as most dog owners know. The visible worm segments and eggs are easy to identify and one of the most recognizable signs of a Diphyllobothrium Latum infection (Medlineplus 2025). Diarrhea is also a common symptom of an infection, so that’s just not a fun time.
For my physical project I’ve made a scale model of the parasite’s length after feasting on the host’s nutrients. Enjoy and thanks for reading!
In this STEAM Project called Human Diphyllobothriasis by Jewelia Lecrone, she talks about Diphyllobothrium Latum. Which is also known as the broad fish tapeworm. This is one of the most common and largest tapeworms that can infect a human. In her STEAM project, she goes over the four functions and the six steps of the digestive system. This is caused when a human eats a raw or uncooked fish that contains the worm when it is in its larval stage. In this project, the first step of digestion is the ingestion of food. When we are eating, this is where the infection begins. Propulsion is the second step and this is when we swallow and peristalsis of the food through the tract. Peristalsis is the function that occurs in the esophagus, stomach, small intestine, and large intestine to keep food moving. The parasite won’t directly affect the function but it can cause some discomfort in the small intestine. The third and fourth step are mechanical breakdown, which is chewing and mixing food with saliva. With digestion working in a series of catabolic steps that involve the enzymes breakdown. The parasite will stick to the walls of the intestines and feed off the nutrients from the host. Absorption is the fifth step and this is where these worms affect the passage of the digested fragments from the lumen of the GI tract into the blood or lymph. The parasites are interfering with the body’s ability to absorb nutrients. Defecation is the final step and this is expelling food that is indigestible. It is easy to spot worm segments and eggs when they are expelled. Making something the length of the tapeworm was a really good project type! Give me the heebee jeebees.