Pathophysiology GI Review

The gastrointestinal system plays a crucial role in the digestion and absorption of food. It breaks down food into smaller molecules through mechanical and chemical processes, such as chewing and the release of digestive enzymes. These smaller molecules are then absorbed into the bloodstream through the lining of the gastrointestinal tract. This allows the nutrients to be distributed throughout the body and used for energy, growth, and repair. Therefore, the statement that the major physiologic function of the gastrointestinal system is to digest food and absorb nutrients into the bloodstream is true.

Vomiting is the sudden and forceful oral expulsion of the contents of the stomach. It is a reflex action that occurs when the body needs to expel harmful substances or when there is irritation in the stomach. Anorexia refers to the loss of appetite, while nausea is the feeling of discomfort in the stomach that often precedes vomiting. Therefore, the correct answer is vomiting.

The correct answer is "large, Large" because defecation is typically initiated by the mass movements of the large intestine. The large intestine is responsible for absorbing water and electrolytes from the remaining indigestible food, forming solid waste known as feces. When the feces accumulate and stretch the walls of the large intestine, it triggers the urge to defecate. Therefore, the large intestine plays a crucial role in the process of elimination.

Anorexia is the correct answer because it specifically refers to a loss of appetite. Nausea and vomiting, on the other hand, are related to feelings of sickness and the act of expelling stomach contents respectively, but do not necessarily involve a loss of appetite. Therefore, anorexia is the most appropriate term to describe a decrease in the desire to eat.

Chemoreceptors monitor the chemical composition of the gastrointestinal tract contents. These receptors are specialized sensory cells that are sensitive to specific chemicals and can detect changes in their concentration. In the context of the gastrointestinal tract, chemoreceptors play a crucial role in detecting the presence of various substances such as nutrients, toxins, and hormones. They provide important feedback to the body, helping regulate processes like digestion and absorption of nutrients. By monitoring the chemical composition, chemoreceptors help maintain homeostasis and ensure proper functioning of the gastrointestinal system.

Amylase is an enzyme that breaks down starch into simpler sugars. It is produced in the salivary glands and pancreas and helps in the digestion of carbohydrates. This enzyme starts breaking down starch into maltose in the mouth during the process of mastication. Therefore, amylase is the correct answer as it directly relates to the process of breaking down starch.

The statement is true because the vasovagal reflex, which involves the vagus nerve, plays a significant role in regulating the motility and secretions of the digestive tract. The vagus nerve helps stimulate the release of digestive enzymes, increases intestinal contractions, and promotes the movement of food through the digestive system. Additionally, the vasovagal reflex can also cause a decrease in blood pressure and heart rate, leading to fainting or syncope, which can be triggered by certain gastrointestinal stimuli.

Nausea is the conscious sensation resulting from stimulation of the medullary vomiting center that often precedes or accompanies vomiting. It is a feeling of discomfort in the stomach and a strong urge to vomit. Nausea can be caused by various factors such as motion sickness, food poisoning, or certain medical conditions. It serves as a warning sign that the body is preparing to expel something from the stomach, which may lead to vomiting.

Mastication refers to the process of chewing food. It is an important step in the digestion process as it breaks down food into smaller pieces, making it easier to swallow and digest. Chewing also helps to mix food with saliva, which contains the enzyme amylase. Amylase helps to initiate the breakdown of carbohydrates in the food. Therefore, mastication plays a crucial role in the initial digestion of food before it enters the stomach.

The circular layer of smooth muscle that lies between the stomach and the small intestine is called the pyloric sphincter. This muscle acts as a valve, controlling the flow of partially digested food from the stomach into the small intestine. It helps regulate the release of food into the small intestine in a controlled manner, allowing for proper digestion and absorption of nutrients. The pyloric sphincter prevents the backflow of partially digested food from the small intestine back into the stomach, ensuring that the food moves through the digestive system in the correct direction.

Triglycerides, which are a type of fat molecule, are broken down by an enzyme called lipase. Lipase is produced by the pancreas and helps to break down triglycerides into fatty acids and glycerol. This process occurs in the small intestine, where lipase is released and acts on the triglycerides present in the food we consume. The breakdown of triglycerides allows for the absorption of fatty acids and glycerol into the bloodstream for energy production and storage.

Mechanoreceptors are sensory receptors that respond to mechanical stimuli such as pressure, stretch, and vibration. In the context of the gastrointestinal tract, mechanoreceptors are responsible for monitoring the stretch and distention of the gastrointestinal tract wall. These receptors detect changes in the size and shape of the tract, allowing the body to regulate processes such as digestion and peristalsis. By detecting the mechanical stimuli, mechanoreceptors provide important feedback to the nervous system, helping to maintain proper functioning of the gastrointestinal system.

The SMALL INTESTINE is the major site for the digestion and absorption of food.

The correct answer is gastroesophageal sphincter. This is because the question is asking for the name of the sphincter that lies just above the area where the esophagus joins the stomach. The lower esophageal sphincter is also known as the gastroesophageal sphincter, so it is the correct answer. The other options (pharyngoesophageal sphincter, stomach, jejunum) are not located in the specified area.

The stomach is located on the left side of the abdomen and acts as a food storage reservoir during the initial stages of digestion. It receives food from the esophagus and breaks it down further using stomach acid and enzymes. This allows for the absorption of nutrients and the passage of food into the small intestine for further digestion and absorption. The pharyngoesophageal sphincter and gastroesophageal sphincter are not responsible for food storage, and the jejunum is a part of the small intestine, not the stomach.

The small intestine is divided into three sections: the duodenum, jejunum, and ileum. The duodenum is the first part of the small intestine and receives partially digested food from the stomach. The jejunum is the middle section and is responsible for absorbing nutrients from the digested food. The ileum is the final section and absorbs any remaining nutrients, as well as vitamins and bile salts. These three subdivisions work together to ensure the proper digestion and absorption of nutrients in the small intestine.

Pepsinogen is the correct answer because it is an enzyme secreted by chief cells in the stomach. Pepsinogen is the inactive form of pepsin, which is responsible for the breakdown of proteins into smaller peptides. Once pepsinogen is released into the stomach, it is activated by the acidic environment and converted into pepsin, which then starts the process of proteolysis.

Enterocytes are specialized cells in the lining of the small intestine that are responsible for absorbing nutrients from digested food. They have microvilli on their surface, which are finger-like projections that increase their surface area for absorption. These microvilli are covered with brush border enzymes, which are enzymes that help break down complex molecules into smaller, more easily absorbed molecules. These enzymes adhere to the border of the villus structures, further enhancing the absorption process.

Some smooth muscle cells in the gastrointestinal tract function as pacemaker cells, similar to the self-excitable cardiac muscle cells in the heart. These pacemaker cells generate electrical impulses that coordinate the contraction and relaxation of the smooth muscle, allowing for the rhythmic movement of food through the digestive system. This rhythmic contraction and relaxation is essential for proper digestion and absorption of nutrients.

The mesentery is a fold of tissue that attaches the intestines to the abdominal wall. It contains blood vessels, nerves, and lymphatic vessels that supply the intestinal wall. This allows for the transport of nutrients and waste products, as well as the regulation of immune responses and nerve signals in the intestines.

Serous fluid forms a moist and slippery surface that prevents friction between continuously moving abdominal structures. This fluid is secreted by serous membranes, which line the abdominal cavity and cover the organs within it. The serous fluid acts as a lubricant, reducing friction and allowing smooth movement of organs such as the intestines. This helps to prevent damage and irritation to the abdominal structures during movements such as digestion or peristalsis.

Epithelial cells carry out the secretory and absorptive functions of the gastrointestinal tract, meaning they are responsible for the secretion and absorption of substances in the digestive system. They also produce mucus, which lubricates and protects the inner surface of the alimentary canal. Epithelial cells line the entire digestive tract and play a crucial role in maintaining its proper functioning. They form a barrier that helps prevent the entry of harmful substances into the body and facilitate the absorption of nutrients from the digested food.

Gastrin is secreted by G cells. It is a hormone that stimulates the release of gastric acid in the stomach. Gastrin also promotes the growth of gastric mucosa and increases gastric motility.

Digestion is the process of breaking down food into smaller, simpler molecules that can be absorbed and used by the body. It involves both mechanical and chemical processes, such as chewing, stomach contractions, and the action of enzymes. Through digestion, complex carbohydrates are broken down into simple sugars, proteins are broken down into amino acids, and fats are broken down into fatty acids and glycerol. These smaller molecules can then be absorbed into the bloodstream and transported to cells where they are used for energy, growth, and repair.

The upper esophageal sphincter, known as the pharyngoesophageal sphincter, is made up of a circular layer of striated muscle. This muscle helps to control the opening and closing of the esophagus, allowing food and liquids to pass from the pharynx into the esophagus and preventing them from flowing back up into the throat. The pharyngoesophageal sphincter plays an important role in the process of swallowing and helps to protect the airway from aspiration.

Chyme is the correct answer because it refers to the result of the chemical breakdown of proteins in the stomach. After proteins are broken down by enzymes, such as pepsin, in the stomach, they form a semi-fluid mixture called chyme. Chyme is then gradually released into the small intestine for further digestion and absorption of nutrients.

Secretin is a hormone that is released by the small intestine in response to the presence of acidic chyme. It acts on the stomach to inhibit gastric acid secretion, which helps to regulate the pH balance in the digestive system. This hormone plays a crucial role in maintaining the proper functioning of the digestive system by preventing excessive acid production in the stomach.

Absorption in the gastrointestinal (GI) tract is accomplished through active transport and diffusion. Active transport refers to the movement of molecules against their concentration gradient, requiring energy. This process allows the GI tract to absorb nutrients such as glucose and amino acids. On the other hand, diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration. This process allows the GI tract to absorb molecules such as water, vitamins, and minerals. Together, active transport and diffusion ensure efficient absorption of nutrients and other substances in the GI tract.

Parietal cells secrete hydrochloric acid and intrinsic factor, which is necessary for the absorption of vitamin B12.

Chief cells secrete pepsinogen, an enzyme that initiates the breakdown of proteins. Pepsinogen is converted into pepsin in the presence of hydrochloric acid in the stomach. Pepsin is then responsible for further breaking down proteins into smaller peptides. Therefore, it is the chief cells that play a crucial role in the initial digestion of proteins in the stomach.

Absorption is the process by which nutrients and other materials are transferred from the external environment of the gastrointestinal tract to the internal environment. This process allows the body to take in essential nutrients, such as vitamins, minerals, and carbohydrates, from the food we consume. Absorption occurs primarily in the small intestine, where nutrients are absorbed into the bloodstream and transported to various cells and tissues throughout the body to support growth, energy production, and overall physiological functions.

Haustrations refer to the contractions and relaxations of the circular muscles in the large intestine, which create pouch-like structures called haustra. These movements help to mix and propel the contents of the large intestine, allowing for further absorption of water and electrolytes. Haustrations also aid in the formation of feces by promoting the movement of waste material through the colon.

The peritoneum is the largest serous membrane in the body. It lines the abdominal cavity and covers the organs within it. It is composed of two layers, the parietal peritoneum which lines the abdominal wall, and the visceral peritoneum which covers the organs. The peritoneum helps to protect and support the organs, as well as provide a smooth surface for them to move against each other during digestion. It also plays a role in the immune response and the absorption of nutrients.

The correct order is:
1. Oral phase
2. Pharyngeal phase
3. Esophageal phase

Cholecystokinin is a hormone that regulates gallbladder contraction and gastric emptying. When food enters the duodenum, cholecystokinin is released by the small intestine and acts on the gallbladder to stimulate the release of bile, which helps in the digestion and absorption of fats. Cholecystokinin also acts on the stomach to slow down gastric emptying, allowing for proper digestion and absorption of nutrients. Therefore, cholecystokinin plays a crucial role in the regulation of gallbladder contraction and gastric emptying.

The jejunum and ileum are segments of the small intestine, where most of the digestion and absorption of nutrients from food occurs. The stomach primarily acts as a storage and mixing chamber for food, while the colon is responsible for reabsorbing water and electrolytes from undigested food. Therefore, the jejunum and ileum are the correct answer as they are the main sites of digestion and absorption in the gastrointestinal tract.

The myenteric and submucosal plexuses are located in the wall of the gastrointestinal tract and are part of the enteric nervous system. This system is responsible for regulating the movements and secretions of the digestive system, independently from the central nervous system. It controls various functions such as peristalsis, secretion of enzymes and hormones, and blood flow to the digestive organs. Therefore, the correct answer is "enteric."

Gastrin is a hormone that plays a crucial role in stimulating the secretion of gastric acid in the stomach. It is produced by specialized cells in the stomach lining called G cells. When food enters the stomach, gastrin is released and it acts on parietal cells in the stomach lining to increase the production and release of gastric acid. This acid helps in the digestion of food and the breakdown of proteins. Therefore, the primary function of gastrin is to stimulate gastric acid secretion.

The colon is home to a diverse range of bacteria, and their main metabolic function is the fermentation of undigestible dietary residue. This process helps break down complex carbohydrates and fiber that cannot be digested by the human body. Through fermentation, these bacteria produce short-chain fatty acids, which provide energy for the colon cells and have various health benefits. This metabolic function is crucial for maintaining a healthy digestive system.

The correct answer is enterocytes. Enterocytes are cells that line the villi in the small intestine. They are responsible for absorbing nutrients from digested food and transporting them into the bloodstream. Additionally, enterocytes play a role in the digestion of carbohydrates and proteins. The presence of goblet cells on the villi also contributes to the secretion of mucus, which helps protect the intestinal lining and aids in the movement of food through the digestive tract.

Cholecystokinin is a hormone that stimulates the secretion of fluid and bicarbonate in the bile. Bile is produced by the liver and stored in the gallbladder, and it plays a crucial role in the digestion and absorption of fats. Cholecystokinin is released in response to the presence of fatty acids and amino acids in the small intestine. It acts on the gallbladder to cause it to contract and release bile into the small intestine, and it also stimulates the secretion of bicarbonate from the pancreas. This helps to neutralize the acidic chyme that enters the small intestine from the stomach, creating a more favorable environment for digestion and absorption.

Brunner glands secrete large amounts of alkaline mucus that protect the duodenum from the acid content in the gastric chyme and from the action of the digestive enzymes.

The mesentery is a fold of tissue that attaches the intestines to the abdominal wall. It contains blood vessels, nerves, and lymphatic vessels that supply the intestinal wall. This allows for the transportation of nutrients and waste products to and from the intestines. The mesentery also helps to support and stabilize the intestines within the abdominal cavity.

Ghrelin is a hormone that has potent growth hormone releasing activity. It also stimulates food intake and digestive function, while reducing energy expenditure.

The myenteric plexus is responsible for motility along the length of the gut. It is a network of nerves located between the circular and longitudinal muscle layers of the gastrointestinal tract. The myenteric plexus controls the contraction and relaxation of the muscles in the gut, which allows for the movement of food and waste materials through the digestive system. It plays a crucial role in regulating peristalsis, the rhythmic contractions that propel food through the intestines.

Saliva serves multiple functions in the body. It acts as a protective barrier, helping to prevent damage and infection in the mouth. Saliva also provides lubrication, aiding in the swallowing and digestion process. It has antibacterial properties, helping to control the growth of harmful bacteria in the mouth. Additionally, saliva contains enzymes that initiate the digestion of starches, breaking them down into simpler sugars. Therefore, the functions of saliva include protection, lubrication, antibacterial action, and initiation of starch digestion.

Cholecystokinin potentiates the action of secretin, increasing the pancreatic bicarbonate response to low circulating levels of secretin. This means that when cholecystokinin is present, it enhances the effect of secretin on the pancreas, causing it to release more bicarbonate. This is important because bicarbonate helps to neutralize stomach acid, and the increased release of bicarbonate can help to maintain the pH balance in the digestive system.

Ghrelin is the second hormone secreted by the stomach. It is primarily known for its role in stimulating appetite and regulating energy balance. Ghrelin is released when the stomach is empty and signals the brain to increase hunger and food intake. It also promotes the release of growth hormone and plays a role in regulating glucose metabolism.

The pudendal nerve controls the external sphincter. The external sphincter is responsible for voluntary control of defecation, allowing us to hold or release stool as needed. The pudendal nerve innervates the muscles of the pelvic floor, including the external sphincter, and provides motor control to these muscles.

Interstitial cells of Cajal are specialized cells found in the gastrointestinal tract that generate slow waves of electrical activity. These electrical waves are essential for coordinating the contractions of the smooth muscles in the digestive system, allowing for proper movement of food through the intestines. These cells act as pacemakers, setting the rhythm and frequency of the contractions. Without the interstitial cells of Cajal, the smooth muscles would not contract in a coordinated manner, leading to digestive issues such as slowed transit time or bowel obstruction.