MCAT Biology : Other Digestive Physiology

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #84 : Digestive System

From where does the stimulation for gastrointestinal contraction originate?

Possible Answers:

Gap junctions

Acinar cells

Cells of Cajal

Gastrointestinal neurotransmitters

Correct answer:

Cells of Cajal

Explanation:

The myenteric interstitial cells of Cajal act as the "pacemaker" of the gastrointestinal tract. They cause spontaneous smooth muscle cell contractions in the stomach, small intestine, and large intestine. These contractions play and integral role in mechanical digestion and motility of digestates.

The stimulus is spread to the gastrointestinal tract via gap junctions; however, the action potential does not originate from the junctions themselves and must be initiated by the cells of Cajal. Acinar cells are found in several regions and are defined by their clustered formation to form an exocrine gland. Acinar cells secrete pancreatic enzymes and saliva in the mouth. The cells of Cajal act via spontaneous depolarization and are not under the direct control of gastrointestinal neurotransmitters.

Example Question #85 : Digestive System

Diarrhea is often caused by improper functioning of the large intestine. What is the most likely reason for diarrhea?

Possible Answers:

Decreased killing of pathogens in the large intestine

Lack of microbes in the large intestine

Decreased water reabsorption in the large intestine

Increased water reabsorption in the large intestine

Correct answer:

Decreased water reabsorption in the large intestine

Explanation:

Diarrhea is a condition that causes living organisms to have loose bowel movements. This means that the bowel movements contain a high amount of liquid water. Recall that the main function of the large intestine is to reabsorb water back into the body. If there is a decrease in water reabsorption, then more water will be excreted via bowel movements; therefore, decreased water reabsorption in the large intestine will lead to loose bowel movements and, subsequently, diarrhea.

Most of the pathogens are not killed in the large intestine; they are killed in the acidic environment of the stomach. The E. coli found in large intestine function to release vitamins, such as vitamin B12. They do not participate in water reabsorption; lack of microbes (E. coli) in the large intestine does not cause diarrhea.

Example Question #86 : Digestive System

A researcher analyzes the large intestine of a human. He observes that the lumen of the large intestine contains large colonies of a gram negative, rod shaped bacterium. Which of the following could be true regarding this bacterium?

Possible Answers:

The identity of the bacterium is E. coli and it doesn’t require oxygen to survive

The identity of the bacterium is a E. coli and it requires oxygen to survive

The identity of the bacterium is Ebola and it doesn’t require oxygen to survive

The identity of the bacterium is Ebola and it requires oxygen to survive

Correct answer:

The identity of the bacterium is E. coli and it doesn’t require oxygen to survive

Explanation:

The large intestine contains a bacterium called Escherichia coli, or E. coli. It is not a pathogen, and instead participates in a symbiotic relationship with the human. E. coli actively synthesize and secrete essential vitamins such as vitamin B12 (required for proper functioning of the nervous system). Recall that the lumen (inside) of the large intestine does not contain any oxygen; therefore, a living organism that thrives inside the large intestine must be able to survive without oxygen. E. coli is a type of facultative anaerobe; this means that it can survive in oxygen rich conditions and in oxygen poor conditions (such as the lumen of large intestine). 

Ebola is a type of virus and is usually not found inside the large intestine. Ebola virus is very harmful because it causes hemorrhagic fever, a fatal disease that leads to excessive blood loss from the circulatory system.

Example Question #87 : Digestive System

Chyme is the semifluid food mass that enters the intestines. Which of the following is true regarding chyme?

Possible Answers:

Chyme enters the large intestine last, where it mostly consists of water and undigested nutrients

Chyme enters the small intestine last, where it mostly consists of water and waste products

Chyme enters the large intestine last, where it mostly consists of water and waste products

Chyme enters the small intestine last, where it mostly consists of water and undigested nutrients

Correct answer:

Chyme enters the large intestine last, where it mostly consists of water and waste products

Explanation:

The question states that chyme is a semifluid food mass that enters the intestines. Recall that this food mass will first enter the small intestine, where the majority of digestion will take place. In the small intestine, chyme contains large amounts of undigested nutrients. The small intestine will absorb most of the nutrients (carbohydrates, fats, and proteins) and will send the digested food mass to the large intestine.

In the large intestine, water and undigested nutrients are reabsorbed from the chyme. The remainder of chyme is considered waste and is excreted through the rectum; therefore, chyme will enter the large intestine after the small intestine and will mostly consist of water and waste products. Most of the water is reabsorbed and the remaining chyme (waste products and a small amount of water) is excreted.

Example Question #581 : Systems Biology And Tissue Types

Which of the following is false regarding the large intestine?

I. The majority of digestion occurs in the large intestine

II. The large intestine contains microbes that have a symbiotic relationship with humans

III. The large intestine has a lower concentration of hydrogen ions than the stomach

Possible Answers:

II and III

I and III

I only

III only

Correct answer:

I only

Explanation:

The large intestine is the last organ in the digestive tract. The food mass exits the stomach as chyme and enters the small intestine, where 90% of chemical digestion occurs. The digested chyme is transported to the large intestine where most of the water and undigested nutrients in the chyme are reabsorbed; therefore, the majority of the digestion occurs in the small intestine, while the majority of water reabsorption occurs in the large intestine. This makes statement I false.

The large intestine also contains E. coli, a bacterial species that thrives in the anaerobic environment of the large intestine. Presence of E. coli is beneficial to humans because the bacteria synthesize vital vitamins such as vitamin B12. This makes statement II true.

Recall that the stomach is characterized by its highly acidic environment. This means that the lumen of the stomach contains a low pH and, therefore, a high concentration of hydrogen ions. Other organs involved in digestion, such as the large intestine, do not contain a highly acidic environment. The pH of the large intestine is higher than that of the stomach and, consequently, it has a lower concentration of hydrogen ions than stomach. This makes statements III true.

Example Question #582 : Systems Biology And Tissue Types

Which answer gives the correct order of food passing through a human's digestive system?

Possible Answers:

Mouth, esophagus, pharynx, cardiac sphincter, stomach, pyloric sphincter, small intestine, large intestine, anus

Mouth, pharynx, esophagus, cardiac sphincter, stomach, pyloric sphincter, large intestine, small intestine, anus

Mouth, pharynx, esophagus, pyloric sphincter, stomach, cardiac sphincter, small intestine, large intestine, anus

Mouth, larynx, esophagus, cardiac sphincter, stomach, pyloric sphincter, small intestine, large intestine, anus

Mouth, pharynx, esophagus, cardiac sphincter, stomach, pyloric sphincter, small intestine, large intestine, anus

Correct answer:

Mouth, pharynx, esophagus, cardiac sphincter, stomach, pyloric sphincter, small intestine, large intestine, anus

Explanation:

The correct answer shows the proper order, and you should pay special attention to the names of the two sphincters.  The cardiac sphincter is by the heart, and comes before the stomach.  The pyloric sphincter is at the bottom of the belly and comes after the stomach.  Food does not pass through the larynx, which is used in breathing and speaking.

Example Question #11 : Other Digestive Physiology

The digestive system begins in the __________.

Possible Answers:

large intestine

stomach

small intestine

mouth

Correct answer:

mouth

Explanation:

The digestive system begins in the mouth with fragmentation. Mucous helps roll the food into a bolus and salivary amylase begins the process of chemical breakdown.

Example Question #91 : Digestive System

Where does lipid digestion begin in the body?

Possible Answers:

Large intestine

Small intestine

Stomach

Mouth

Correct answer:

Mouth

Explanation:

Lipid digestion begins to occur in the mouth because of the enzyme lipase. Saliva in the mouth incorporates both lipase, to begin lipid digestion, and amylase, to being carbohydrate digestion. Lipids are also broken down later in the digestive pathway by lipase in the small intestine. Protein digestion does not begin until food enters the stomach.

Example Question #585 : Systems Biology And Tissue Types

A lack of fat ingestion or fat absorption in the body can lead to a deficiency in what vitamin?

Possible Answers:

Vitamin B6

Vitamin B12

Vitamin C

Vitamin A

Correct answer:

Vitamin A

Explanation:

Vitamins A, D, E, and K (ADEK) are fat soluble vitamins, and require the ingestion and absorption of fat in order to maintain adequate stores of the vitamins in the body. Any problems with bile salt function or absorption of bile salt and fat miscelles in the small intestine can lead to a deficiency in vitamins A, D, E, and K. All other vitamins can be absorbed without the help of fat.

Example Question #601 : Biology

Which of the following is not a function of the human gastrointestinal system?

Possible Answers:

Digestion

Catabolism

Absorption

Filtration

Correct answer:

Filtration

Explanation:

The gastrointestinal, or digestive, system is primarily designed to break down (catabolize) nutrients and absorb them into the blood for use by the body. Digestion of nutrients by stomach and pancreatic enzymes allows for their absorption in the small intestine. The large intestine is responsible for water absorption.

Filtration occurs in three primary areas in the body: the kidney, the liver, and the spleen/lymph nodes. The kidney is part of the excretory system, in which fluids are filtered from the blood to remove solute waste from the body. The liver filters the blood in circulation, and is responsible for removing toxins that may have been absorbed during digestion. It is not, however, part of the gastrointestinal tract. The spleen and lymph nodes filter the interstitial fluid to screen for antigens and pathogens.

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