Digestive System, Coursework Example

Part A: Background of the Experiment

Diagram of the Digestive System

Function of Six Organs

Liver: The liver has numerous functions; however, its specific digestive function is the production of the fat emulsifier, bile (Marieb, p755). The catabolic process leads to fats that are easily accessible to digestive enzymes (Marieb, p756). The liver metabolizes the nutrient-laden blood from other organs.

Gallbladder: The gallbladder’s chief function is to store bile and augment its properties with ions and water (Marieb, p752).

Pancreas: The pancreas is essential to the creation of a broad spectrum of enzymes that are necessary for the breakdown of various food particles. The exocrine pancreatic juice through the main pancreatic duct amylase, lipases, and nucleases are secreted and join the bile in the small intestine to optimal activity (Marieb, p753) .

Large Intestine: The main function of the large intestine is to absorb the water from indigestible foods and eliminate them in semisolid feces (Marieb, p766).

Small Intestine:  The small intestine has the most significant contribution to the digestive process. Within its twisted confines, the ileum, duodenum, and jejunum have the surface area capable of maximal nutrient absorption (Marieb, p754).

Stomach: The stomach is a storage area for food in which the proteins in the food are turned into chyme (Marieb, p754).

Summary of Mechanical and Chemical Digestion

Mechanical Digestion

Mechanical digestion is the process in which food is physically prepared before the next stage of chemical digestion. The physical grinding and churning that occurs in the form of mastication, churning in the stomach and segmentation, which occurs in the intestine (Marieb, p740).

Chemical Digestion

Chemical digestion consists of catabolism of the most basic chemical constituents. Enzymes are released into the lumen of the alimentary canal (Marieb, p740). This process begins in the mouth cavity and reaches its completion in the small intestine.

Seven Examples of Enzymes

Lysozyme: Lysozyme is a bacterial enzyme that inhibits bacterial growth in the mouth cavity.

Acetyl – CoA: Acetyl CoA is used in the Kreb’s Cycle and is pertinent to the process of  aerobic respiration.

Pepsin: Chief cells are activated by the pepsinogen, which is activated by HCl before aiding in the digestion of proteins.

Rennin: A chief enzyme that works in the conversion of the milk protein, casein, converting it to the curded substance.

Lipases: Lipases break down fats.

Urease: An enzyme that breaks down urea into carbon dioxide (CO₂) and ammonia (NH₄).

Amylase: An enzyme in the mouth’s saliva that converts starch into sugar.

Two Experiments

An experiment  was completed regarding supplemental enzymes and the effects that were seen in individuals who took the supplements.  By using a computerized  gastrointestinal model (TIM), it was found that supplemental enzymes increased the availability of glucose to the whole body in the study entitled “Enzyme Supplements Could Improve Digestive Processes, New Research” (2004).

The simulation of the various enzymes that were isolated using polymerase chain reactions were  added to a experiment participant’s diet. The health effects were apparent and all beneficial in the study entitled “Digestive Enzymes and Their Importance” (2009).

Part B: Design Plan for the Experiment

Independent and Dependent Variables

This experiment will recreate the experiment completed by the Neo/Sci Digestion Kit. By adding larger amount of an enzyme to a experiment food, the effect can be recorded. The independent variable is the untreated food. The dependent variable is the food treated with the enzyme.

Hypothesis

The food treated with the enzyme pepsin will be processed much faster.

Explanation of the Procedure

The use of pepsin will be examined in one dish and the controlled petri dish of food with no treatment will be observed at room. . The procedure will last over the course of three days. Three petri dishes will be used. Each dish will have a separated category: one for carbohydrates, one for lipids, and one for proteins.

Both experiments will be kept in identical temperatures, in the same environment, and will be observed at the exact same time each day over the course of three days.

Part C: Experiment

Explanation

Using the Neo/Sci Digestion kit, different enzymes were applied to common foods to see the resulting patterns of degradation.

Conclusion

The use of separate molecules in the categories of carbohydrates, fats and proteins helped to distinguish where the primary location of digestion occurs for each enzyme. The pepsin was very effective in the degradation of proteins. This follows the hypothesis I had when I began this experiment, which sought the effects of pepsin on food when compared to a control group that had no added enzyme to it. The pepsin clearly had an affinity for proteins and worked to break them down in the component amino acid constituents.

Part D: Interdependency of the Digestive, Respiratory and Cardiovascular Systems

Flow Chart of Carbohydrates, Proteins, and Lipids Absorption

Steps in Absorption of Carbohydrates, Proteins, and Lipids

Explanation of Diagram

The majority of the metabolism of nutrients occurs in the small intestine. Depending on the complexity of the carbohydrates, some components may be absorbed in the stomach, but the majority of its components are absorbed in the small intestine. After the lipids, carbohydrates and proteins are absorbed, they enter capillary beds through diffusion. From there, the nutrients go to the hepatic portal vein, where most nutrients are sorted. Some nutrients are broken down through catabolism so they can be delivered easily to organs in need of the components. Other nutrients are used to build the necessary particles through anabolism.

Metabolism of Proteins

Proteins must be broken down into their amino acid components while they are still viable. Afterward, they must be replaced before deterioration of the molecules occur. When amino acids are ingested, they are moved into cells via active transport where they replace proteins at a rate of 100 grams per day (Marieb, p889). When proteins are in excess of the demand of a particular process, amino acids are oxidized for energy use or converted to fats.

Metabolism of Carbohydrates

Absorbed carbohydrates are transported to the liver where fructose and galactose are converted to the more efficient glucose. Glucose is then converted to glycogen or fat. Glycogen is stored in the liver, while the fats are exported to the blood for transport to adipose tissues.

Metabolism of Fats

Nearly all fats are chylomicrons which are hydrolyzed. This creates fatty acids and glycerol, which are easily absorbed into capillary beds. Adipose tissue, skeletal muscle tissue, and liver cells use triglycerides as the main source of energy.

Delivery of Nutrients from Cells to Capillaries

The nutrients are broken down into the smallest possible components before the capillaries are able to absorb them.  Oxygen is exchanged through the erythrocytes, moving from the cells to the capillary beds. In the process of diffusion, the oxygen and nutrients move from the red blood cells to the tissues through the capillaries.  The natural homeostatic tendencies of nutrients moving from a greater concentration to a lower concentration.

Likewise, when carbon dioxide and metabolic waste are built up in the bodily tissues, capillaries with a lower concentration will take in the waste through diffusion. At that point, the waste and carbon dioxide will diffuse from the tissues and be carried to the venous system. The venous system contains de-oxygenated blood and carries it back toward the heart. Once the carbon-dioxide-rich blood reaches the lungs, the carbon dioxide moves from the blood into the alveoli of the lungs before it is exhaled.

Movement of nutrients from the cells to the capillaries occurs through the passive process of diffusion. Diffusion involves the exchange of gases that occurs naturally as a homeostatic mechanism in the body. Perfusion is the process by which the cardiovascular system s send blood to the lungs.

Hepatic Portal

The liver stores various nutrients – most notably glycogen. When an area of the body needs more of any of those nutrients, the liver delivers them through the hepatic portal vein. This large vein carries blood from the digestive organs to the liver. At this point the nutrients are converted by hepatocytes before entering the systemic circulatory process.

The circulatory system within the liver is unique from all the other organs of the body. Most of the blood supply that is transported to the liver is venous blood, which means the blood is de-oxygenated. Almost three-fourths of all the blood entering the liver comes from the hepatic portal vein. The hepatic portal vein takes the returning blood from the small intestine, stomach, pancreas and the spleen. All of the nutrients that are taken in by the stomach and small intestine go immediately to the liver.

The remaining one-fourth of blood that reaches the liver is oxygenated blood from the hepatic artery. Both venous and arterial channels converge in the sinusoids of the liver. Sinusoids are surrounded by hepatocytes and are aligned with endothelial cells. Blood flow through sinusoids allows a large amount of plasma to be filtered into the small space between the endothelium and the liver cells. This provides the majority of the body’s lymph fluids.

Oxygen Delivery

Oxygen is delivered through the Iron-rich blood which contains hemoglobin – an oxygen carrier.  Red blood cells carry the hemoglobin which binds to oxygen and escorts it throughout the circulatory system. The nutrients are broken down into their basic elements before the capillaries can easily absorb them from the cells.  Oxygen is exchanged through the erythrocytes, moving from the cells to the capillary beds. In the process of diffusion, the oxygen  move from the erythrocytes to the tissues through the capillaries.  The natural homeostatic tendencies of oxygen or carbon dioxide moving from a greater concentration to a lower concentration.

Likewise, when carbon dioxide is built up in the bodily tissues, capillaries with a lower concentration will take in the deoxygenated blood and carbon dioxide through diffusion. At that point, the carbon dioxide will diffuse from the tissues and be carried to the venous system. The venous system contains de-oxygenated blood and carries it back toward the heart. Once the carbon-dioxide-rich blood reaches the lungs, the carbon dioxide moves from the blood into the alveoli of the lungs before it is exhaled.

Movement of nutrients from the cells to the capillaries occurs through the passive process of diffusion. Diffusion involves the exchange of gases that occurs naturally as a homeostatic mechanism in the body. Perfusion is the process by which the cardiovascular system s send blood to the lungs.

Urinary System

Simple cuboidal epithelial tissues function in absorption and secretion – two essential functions for the kidneys. The kidneys’ role is to provide homeostatic mechanisms via the excretion of urine. In the process, the kidneys gauge the levels of different nutrients and eliminate the excess from the body via urine. Any nutrients the kidney recognizes as necessary are reabsorbed into the bloodstream where they can travel to the rest of the body. The human body relies so heavily on the proper function of the kidneys in maintaining its homeostasis that even mild damage to one of the kidneys can have devastating effects on the rest of the body.

Water intake must equal the amount of water output in order for the human body to remain properly hydrated. Most water intake is derived from ingested liquids (60%) with 30% of the intake from solid foods and the last 10% from cellular metabolism. Water output has several routes. Approximately 28% of the water leaves the body via the vaporization expelled by the lungs and the skin. 8% is lost through perspiration, 4% of water intake leaves the body via feces, and remaining 60% is lost via the kidneys.

On a macroscopic level, the water enters the oral cavity, it travels down the muscular tube known as the esophagus. The act of swallowing causes a flap known as the epiglottis to close over the opening to the trachea, and keeps the water on the right course, passing down into the stomach via peristalsis. After settling in the stomach for awhile, the water – mixed now with acids and other food in the stomach – is churned into chyme and sent to the duodenum.  From there it travels through the small intestine via the small villi that push it through the 22 feet of small intestine before it enters the large intestine. In the large intestine where the majority of the water is absorbed via the osmotic gradient in the wall of the intestine. At this point the water flows into the intracellular place where it is absorbed by the blood vessels in the vicinity.

From there, the water travels in the blood vessels  to the liver then to the heart and from there it becomes oxygenated by the lungs and then back to the heart through the aorta back down to the kidneys where the liquid is filtered in the glomerulus. Approximately 10% of the water is turned into urine and collects in the kidney; the other 90% is reabsorbed into the bloodstream after proper filtration (Rubin,543). From the kidney the urine travels down into the ureters and empties into the bladder. From the bladder, the urine travels into the urethra before exiting the body.

Microscopically, when the nephron takes in the water, the water flowed into the glomerulus and filters the fluid in a process controlled by Starling forces of ultrafiltration (Rubin, 544). Afterward, the filtrated fluid is passed into Bowman’s capsule from which it will descend into a proximal tubule of the Loop of Henle and ascend the distal tubule before entering a series of ducts that collect urine (545). If reabsorption takes place at this point, then the filtrated fluid returns to the blood vessels for the second time (the first time being the absorption from the large intestine.)

References

Marieb, Elaine N..Anatomy and Physiology. San Francisco: Pearson Education, Inc Benjamin Cummings, 2002

Niles, James. “Enzyme Supplements Could Improve Digestive Processes, New Research”. (2004). Retrieved on October 11, 2010 from Nutaingredients-USA.com: http://www.nutraingredients-usa.com/Research/Enzyme-supplements-could-improve-digestive-processes-new-research

Vogel, Marijke. “Digestive Enzymes and their Importance”. (2009). Retrieved on October 11, 2010 from wholisticresearch.com: http://www.wholisticresearch.com/info/artshow.php3?artid=328