Gastrointestinal System Quiz

The rhythmic contractions that move food through the digestive tract.

The release of substances such as water, digestive enzymes, and hormones into the digestive tract.

The chemical breakdown of large food molecules into smaller ones that can be absorbed.

The uptake of nutrients from the digestive tract into the bloodstream or lymph.

The elimination of waste products from the digestive tract.

The innermost layer of the GI tract responsible for absorption and secretion.

The layer of the GI tract containing blood vessels and nerves.

The muscular layer of the GI tract responsible for movement.

The first part of the small intestine, responsible for digestion and secretion of digestive enzymes.

The middle portion of the small intestine, primarily responsible for absorption of nutrients.

The final segment of the small intestine, playing a crucial role in absorbing nutrients.

Finger-like projections that increase the surface area of the small intestine, enhancing nutrient absorption.

Microscopic projections extending from the surface of villi, further increasing surface area for optimal nutrient absorption.

A specialized muscle layer in the large intestine responsible for its characteristic segmented appearance.

A network of nerves in the digestive system, acting as a 'second brain' and controlling motility.

Specialized cells in the liver responsible for filtering and detoxifying blood.

The gallbladder stores bile, a fluid that aids in fat digestion. It's stimulated to release bile, which flows through the cystic duct to the common bile duct and then into the duodenum.

The pancreas has both endocrine and exocrine functions. Exocrine function involves secreting digestive enzymes into the pancreatic duct, which eventually reaches the duodenum.

Pancreatic enzymes are mostly secreted in an inactive form called zymogens. These are activated in the small intestine, preventing the enzymes from digesting the pancreas itself.

Enterokinase, an enzyme from the small intestine's epithelial cells, activates trypsinogen into trypsin, the key activator for other pancreatic enzymes.

Trypsin, once activated, activates other pancreatic enzymes like chymotrypsin, elastase, and carboxypeptidase, breaking down proteins into smaller peptides.

Pepsin, secreted in the stomach, breaks down proteins into short chains of amino acids. Further breakdown occurs in the small intestine with the help of endopeptidases and exopeptidases.

Carbohydrates like starches (glucose polymers), sucrose (glucose + fructose), and lactose (glucose + galactose) are primarily ingested. Salivary amylase starts breaking down starch in the mouth, but pancreatic amylase takes over in the small intestine.

In the final stages of carbohydrate digestion, the small intestine's brush border enzymes break down all sugars into monosaccharides (glucose, galactose, fructose), which can then be absorbed and enter the bloodstream.

The gastric phase of digestion is initiated by the presence of food in the stomach and is characterized by the release of gastric juices to aid digestion.

The gastric phase is triggered by distention of the stomach, which means stretching of the stomach wall due to food entering it.

The type of food ingested in terms of its composition influences the gastric phase. The presence of proteins and amino acids in the stomach activates the release of gastrin, a hormone that stimulates further gastric secretion.

The intestinal phase of digestion is the stage that begins when food passes from the stomach to the small intestine. It involves a complex interplay of signals and hormones that aim to regulate further digestion and absorption.

When food enters the small intestine, it stretches the intestinal wall. This distension activates a neural reflex, which in turn stimulates both the small intestine and the pancreas.

The presence of fats in the food stimulates the release of cholecystokinin (CCK), a hormone produced in the small intestine. CCK plays a crucial role in the regulation of pancreatic enzymes and gallbladder function.

Secretin, a hormone released from the small intestine, is crucial for the regulation of pancreatic secretion. When chyme, the partially digested food mixture, enters the duodenum, it can be acidic. Secretin helps neutralize this acidity by stimulating the pancreas to release bicarbonate.

The pancreas plays a crucial role in digestion by releasing pancreatic enzymes and bicarbonate. Fat in the chyme triggers the release of cholecystokinin (CCK) by the duodenum, stimulating the pancreas to produce and release digestive enzymes.

Di- and tripeptides are transported across the apical surface of the small intestine by specific transporters. Cellular dipeptidases and tripeptidases break them down further into single amino acids. These amino acids are then transported across the basal surface of the intestinal epithelium by amino acid transporters and enter the bloodstream.

Exopeptidases are enzymes that break down peptides from the ends (either amino or carboxyl terminus). Endopeptidases, on the other hand, cleave peptide bonds within the peptide chain.

The brush border of the small intestine is lined with a layer of microvilli, which increase the surface area for absorption. Brush border enzymes, including dipeptidases and tripeptidases, play a crucial role in digesting dipeptides and tripeptides.

The absorption of amino acids across the intestinal epithelium often involves co-transport with sodium or hydrogen ions. This process is called active transport, requiring energy to move molecules against their concentration gradient.

Fat digestion primarily occurs in the small intestine. Bile salts emulsify fat droplets, creating smaller droplets with increased surface area. Pancreatic enzymes, like lipase, break down triglycerides into monoglycerides and fatty acids, which form micelles with bile salts.

Micelles are tiny spheres formed by bile salts, cholesterol, and lecithin. They act as transport vehicles for digested fats, transporting them into the epithelial cells of the small intestine.

Once absorbed, triglycerides are reassembled in the smooth endoplasmic reticulum of intestinal epithelial cells. These triglycerides are packaged into chylomicrons, which are lipoprotein particles that are then transported to the bloodstream via the lymphatic system.

Apolippoproteins are protein components of lipoproteins, including chylomicrons. They play a crucial role in regulating the transport and metabolism of lipids in the bloodstream.