Test: Gastrointestinal System - 1 - MCAT MCQ

The stomach serves as a temporary storage site for food and performs mechanical breakdown through muscular contractions. It churns and mixes food with gastric juices to form a semi-liquid mixture called chyme.

The small intestine is responsible for the majority of nutrient absorption in the gastrointestinal system. Its lining contains specialized structures called villi and microvilli, which increase the surface area for efficient absorption of nutrients into the bloodstream.

The primary function of the large intestine is to absorb water and electrolytes from the remaining indigestible food materials, forming feces. It also houses beneficial bacteria that aid in the synthesis of vitamins.

The liver is responsible for the production and secretion of bile, which is stored in the gallbladder before being released into the small intestine. Bile aids in the emulsification and digestion of fats.

Gastrin is a hormone produced by the stomach in response to the presence of food. It stimulates the secretion of gastric acid and promotes stomach contractions, aiding in the digestive process.

The pancreas develops from the endoderm, one of the three primary germ layers formed during embryonic development. The endoderm gives rise to various organs and tissues of the digestive and respiratory systems, including the pancreas.

The stomach is least likely to be the cause of steatorrhea. While the stomach plays a role in digestion by secreting gastric juices and mixing food with stomach acid, the majority of fat digestion occurs in the small intestine. The liver produces bile, which aids in the emulsification and absorption of fats in the small intestine. The pancreas produces pancreatic enzymes, including lipase, which help break down fats. Therefore, dysfunction of the liver, small intestine, or pancreas is more likely to result in steatorrhea than the stomach.

SGLT1 (Sodium-Glucose Linked Transporter 1) is a symporter that is primarily found in the small intestine and plays a crucial role in the absorption of glucose and galactose from the lumen of the small intestine into the enterocytes. It uses the energy from the sodium gradient created by the Na+/K+ ATPase pump to transport glucose and galactose against their concentration gradient into the intestinal cells. Therefore, SGLT1 is responsible for the uptake of monosaccharides (glucose and galactose) from the intestinal lumen into the bloodstream for further distribution and utilization by the body.

 found in milk and dairy products. It is primarily located in the brush border of the duodenum, which is the first part of the small intestine. The brush border refers to the microvilli-covered surface of the intestinal epithelial cells, which greatly increases the surface area available for absorption and digestion. Lactase is produced by the cells of the small intestine and is embedded in the brush border membrane. It catalyzes the hydrolysis of lactose into glucose and galactose, which can then be absorbed into the bloodstream for energy utilization. In individuals with lactose intolerance, there is a deficiency or decreased activity of lactase, leading to the inability to digest lactose properly, resulting in symptoms such as bloating, diarrhea, and abdominal discomfort after consuming lactose-containing foods.

Gastroesophageal reflux disease (GERD) is a condition characterized by the backflow of stomach acid and other stomach contents into the esophagus. This can occur due to a weakened lower esophageal sphincter (LES), which normally acts as a barrier to prevent the reflux of gastric contents. When the LES is weakened, the acidic contents of the stomach, including gastric acid and digestive enzymes, can enter the esophagus, leading to irritation and inflammation.

Pepsin is a digestive enzyme produced by the chief cells in the stomach. It is responsible for the breakdown of proteins into smaller peptides. In GERD, the refluxed stomach acid can carry pepsin into the esophagus, where it can cause damage to the esophageal lining and contribute to symptoms such as heartburn, chest pain, and regurgitation.

The other enzymes mentioned, trypsin, chymotrypsin, and carboxypeptidase, are pancreatic enzymes involved in protein digestion. They are not typically found in the esophagus and their presence there would not be associated with GERD.