The Digestive System
The digestive system is responsible for collecting the nutrients essential for our survival. From ingestion, to digestion, to absorption and elimination, the digestive system integrates many organs. In the alimentary tract, we have the stomach, small intestines and colon; as accessory organs, we have the liver pancreas and gall bladder. This section focuses on methamphetamine’s adverse effects on the digestive system.
The Alimentary Canal (Gastrointestinal Tract):
When foods or drinks are ingested, they enter through the mouth and once swallowed, travel through the esophagus into the stomach. Digestion begins in the mouth with salivary amylase, continues with pepsin in the stomach, and ends with lipases, proteases, nucleases and pancreatic amylase in the intestines. In the small intestines, previously digested and broken-down monomers diffuse into capillaries through microvilli while fats are absorbed into lacteals. The colon absorbs water as needed, and finally undigested wastes and unabsorbed nutrients are eliminated from the body through the anus.
When methamphetamine is ingested, it effects the entire digestive system. This begins in the mouth. Meth mouth is a term used to describe a meth user’s the rotten and decayed teeth. There are multiple reasons why methamphetamine causes meth mouth. One reason is that methamphetamine is such an intense psycho-stimulant (a drug that stimulates mental and physical activity) it causes users to neglect their dental hygiene. As referenced in the nervous system section, methamphetamine usage lowers cerebral function. Therefore, it correlates with an increase in impulsive and less logical behaviors because of decreased frontal cortex activity. Because of this, methamphetamine users feed all of their desires and addictions, and frequently binge eat sugary foods.
In addition to this, chemicals used to synthesize methamphetamine such as anhydrous ammonia remain in the crystal meth after production. When ingested or smoked, they and can cause corrosion of tooth enamel (PBS 2008). The drug itself also causes major changes in the body by stimulating the sympathetic nervous system. Prolonged usage of methamphetamines and large doses of the drug can keep the sympathetic nervous system running too long. When the body is constantly strained, decreased blood flow to the mouth can cause gums to deteriorate and cause teeth to fall out.
When the sympathetic nervous system is activated, the digestive system is mostly shut down and energy is diverted to power a fight or flight response (University of Georgia, 2010). This causes a severely decreased metabolism and a lack of absorbed nutrients due to decreased digestive functions. This in turn causes other negative health issues such as extreme loss in weight and malnutrition. Depending on what few foods are consumed, methamphetamine users commonly experience constipation or diarrhea. Decreased thirst can cause dry mouth and further the severity of meth mouth (MileHighMethProject 2012).
The Accessory Organs of the Digestive System:
From storing glycogen to hormone production, the liver plays a major role in the human body. The liver is necessary for survival; there is currently no way to compensate for the absence of liver function long term (Medicine Plus). Thus, this section will explore methamphetamine’s adverse effects on the liver.
In Denver, home-cooked meth is only 10 to 20% crystalized methamphetamine, and the majority of the substance is saturated with toxins and byproducts of the dangerous and hazardous cooking process. If the drug is ingested, the substance will be absorbed in the gastrointestinal tract, mainly through the small intestines. As we have learned in class, these small molecules can passively diffuse through microvilli in the small intestines.
Once they are through the microvilli, they can passively diffuse through the simple squamal epithelial cells of capillaries and pass through the bloodstream. Their first stop in the blood stream, however, is the liver, through the Hepatic Portal veins. Here in the liver, the methamphetamine molecules as well as the toxins from the cooking process are absorbed into individual liver cells where the endoplasmic reticulum of each cell processes these chemicals.
As shown in the diagram above, the hepatocytes (liver cells) are the functional units of the liver and process the detoxification of drugs and toxins. The liver is able to breakdown methamphetamines into smaller and simpler chemicals so that they can be filtered out by the kidneys and excreted. With each cycle of circulation through the bloodstream, more and more of the drug is broken down, filtered out and excreted.
Crystal meth carries many extremely toxic chemicals from the cooking process including: chloroform, ether, hydrochloric acid, lithium, and many more.
These chemicals are extremely harmful to the liver, and cause immense stress on the body because nutrients, vitamins, minerals and energy are expended during the process of detoxifying these toxins.
Although the liver and pancreas are classified as “accessory organs” of the digestive system, they are critical for the health and wellbeing of a person. The pancreas, although small in size when compared to many other organs, plays a vital role in the digestive system as well as the endocrine system. This section focuses on methamphetamine’s adverse effects on the pancreas.
The pancreas secretes numerous fluids that aid the digestion of food in the intestines including the following: bicarbonate to neutralize the pH of chyme (digested food from the stomach), proteases to breakdown proteins into amino acids, lipases to breakdown complex fats into simpler fats and glycerol and fatty acids, pancreatic amylase to break down sugars into monosaccharides, and nucleases to break down DNA and RNA into nucleotides.
As discussed in Dr. Ferguson’s General Biology I Lecture, organs are composed of two or more tissues, and tissues are composed of two or more cells. But what happens when drugs such as methamphetamine disrupt and damage the tissues of the pancreas? According to a study by Ito in 1997, the chronic stimulus of methamphetamine in rats causes significant changes in pancreatic tissues and may cause deterioration of vessels supplying the pancreas with blood; therefore introducing a risk of hypoxia, or lack of oxygen. This study was conducted in 1997 at Saga Medical School in Japan. The abstract can be found at this link: A Histopathological Study of Pancreatic Legions After Chronic Administration of Methamphetamine to Rats.
If the pancreas ceases to function properly, digestion can slow down and become less efficient, thus causing a vicious cycle of malnutrition and weight loss for methamphetamine users.