Gastrointestinal System 2

What is the main digestive function of the liver?

To produce bile.

What is bile, and what is its role in digestion?

Bile is a detergent-like fat emulsifier that mechanically breaks down fats.

What are the two primary functions of the pancreas?

Exocrine function: produces pancreatic juice; Endocrine function: produces hormones controlling blood glucose levels.

Where is the liver located in the body?

Below the diaphragm in the upper right portion of the abdomen.

What is the structural division of the liver?

The liver is organized into lobes and lobules.

What are the primary components of a liver lobule?

Each liver lobule consists of hepatocytes arranged around a central vein.

What is the role of the central vein in a liver lobule?

The central vein collects blood from the lobule and drains into the hepatic vein.

What is the significance of portal triads in liver lobules?

Portal triads contain a bile duct, a portal vein, and a hepatic artery which supply blood and bile to the liver.

What surrounds the liver lobules?

Liver lobules are surrounded by connective tissue known as the Glisson's capsule.

How many lobes comprise the liver, and what are they called?

The liver has four lobes: right, left, caudate, and quadrate.

What type of sinusoids are found in the liver lobules?

The liver contains specialized capillaries called sinusoids that allow for the exchange of substances between blood and hepatocytes.

What is a liver lobule?

The structural and functional unit of the liver, composed of hepatocytes.

What are hepatocytes?

Liver cells that filter and process nutrient-rich blood.

What does the portal triad of a liver lobule consist of?

A hepatic arteriole, a portal venule, and a bile ductule.

What is the function of the hepatic artery?

The hepatic artery supplies oxygen-rich blood to the liver.

How does blood from the portal vein differ from that from the hepatic artery?

Blood from the portal vein is nutrient-rich and deoxygenated, while blood from the hepatic artery is oxygen-rich.

What is the connective tissue framework in the liver responsible for?

It supports the structural integrity of the liver and houses blood vessels and bile ducts.

What is the role of bile canaliculi in liver lobules?

Bile canaliculi collect bile produced by hepatocytes and direct it towards bile ducts.

What is the function of the falciform ligament?

Anchors the liver to the anterior abdominal wall.

What is the round ligament of the liver a remnant of?

An umbilical remnant (ligamentum teres).

What is the porta hepatis?

The area of entrance and exit of the liver.

What is the bare area of the liver?

An area on the superior portion of the right lobe not covered by visceral peritoneum.

What are the main metabolic functions of the liver?

Carbohydrate metabolism, lipid metabolism, protein metabolism, detoxification, synthesis of bile acids.

Define glycogenesis.

The process of converting glucose into glycogen for storage.

What is glycogenolysis?

The process of breaking down glycogen into glucose for energy.

Explain gluconeogenesis.

The process of creating glucose from non-carbohydrate sources for energy.

What are some plasma proteins synthesized by the liver?

Albumin and blood clotting factors.

What is the role of Kupffer cells in the liver?

They are a type of phagocyte that filters out toxins and waste products.

How does the liver activate vitamin D?

Activates vitamin D in conjunction with the kidneys.

How does the liver receive oxygen-rich blood?

Through the hepatic arteries that branch from the celiac trunk.

What is the function of the portal vein?

Carries deoxygenated, nutrient-rich blood from the digestive organs to the liver.

Where does the nutrient and oxygen-poor blood from the liver eventually return to?

The heart via the inferior vena cava.

What happens to bile produced by hepatocytes?

It is secreted into bile canaliculi, then to bile ductules, and finally stored in the gallbladder.

What is the main function of the gallbladder?

To store and concentrate bile.

What is the structure of the gallbladder?

The gallbladder is a muscular sac that stores and concentrates bile, with a mucosal lining that can absorb water.

What are the major layers of the gallbladder wall?

The gallbladder wall consists of three layers: the mucosa, muscular layer, and serosa.

What is the function of the muscular layer in the gallbladder?

The muscular layer contracts to release bile into the cystic duct during digestion.

What type of epithelium lines the gallbladder?

The gallbladder is lined with simple columnar epithelium that facilitates absorption.

What is the role of the cystic duct?

The cystic duct connects the gallbladder to the common bile duct, allowing bile to flow into the duodenum.

How does the gallbladder concentrate bile?

The gallbladder concentrates bile by absorbing water and electrolytes.

What is a common bile duct?

The duct that transports bile from the gallbladder and liver to the duodenum.

What is unique about bile in terms of its composition?

It is alkaline with a pH of 7.6 to 8.6 and contains bile salts, cholesterol, and bilirubin.

How does bile aid in lipid digestion?

Bile contains bile salts that emulsify fats, breaking them into smaller droplets to increase the surface area for digestive enzymes.

What is the process through which bile salts emulsify fats?

Emulsification involves the mechanical breakdown of large lipid globules into smaller, more manageable droplets.

What is the purpose of emulsification in fat digestion?

To break down large lipid globules into smaller droplets

Why is emulsification important for lipid digestion?

Emulsification makes it easier for lipase enzymes to access and digest

What elements are primarily absorbed in the small intestine?

Monosaccharides, amino acids, fatty acids, glycerol, and electrolytes.

What is reabsorption in the small intestine?

Reabsorption in the small intestine is the process where nutrients, water, and electrolytes are absorbed back into the bloodstream from the gastrointestinal tract.

How is glucose reabsorbed in the small intestine?

Glucose is reabsorbed through active transport mechanisms, often using cotransport with sodium ions.

What role do villi and microvilli play in reabsorption?

Villi and microvilli increase the surface area of the intestinal lining, enhancing the efficiency of nutrient absorption.

What is the significance of the brush border in the small intestine?

The brush border, formed by microvilli, contains enzymes that aid in the final stages of digestion and absorption.

How much fluid is absorbed in the small intestine daily?

Approximately 7-8 liters of fluid is reabsorbed in the small intestine daily.

What mechanisms facilitate the reabsorption of water in the small intestine?

Water is primarily reabsorbed through osmosis, which follows the reabsorption of solutes like glucose and sodium.

What does pancreatic juice help to neutralize?

The acidic gastric juice in chyme.

How does the autonomic nervous system manage digestion?

Through the sympathetic (decreases motility) and parasympathetic (increases motility) systems.

What are the two types of control over food movement through the gastrointestinal tract?

Hormonal influences and neural influences.

What factors control appetite?

Hormonal signals, emotional state, and metabolic needs regulated by the hypothalamus.

What happens during the absorptive state?

Nutrients like glucose, amino acids, and fatty acids are absorbed for energy and storage.

What is the main hormone regulating the absorptive state?

Insulin.

What is the primary source of energy for brain and kidney metabolism during the post-absorptive state?

Glucose.

What is the function of chylomicrons?

To transport dietary lipids from the intestines to the bloodstream.

What are the four types of lipoproteins?

Chylomicrons, low-density lipoproteins (LDL), very low-density lipoproteins (VLDL), high-density lipoproteins (HDL).

How does the body regulate cholesterol levels?

By synthesizing new bile acids from cholesterol when some are lost through feces.

What are the primary sources of cholesterol?

Exogenous sources from food and endogenous synthesis from the liver.

What happens if there is too much saturated fat in the diet?

It can lead to elevated cholesterol levels in the blood, increasing the risk of atherosclerosis.

What are the main sections of the large intestine?

The large intestine is divided into the cecum, colon (ascending, transverse, descending, sigmoid), rectum, and anal canal.

What is the primary function of the cecum?

The cecum receives waste material from the small intestine and begins the process of compaction.

What are haustrae and their role in the large intestine?

Haustrae are small pouches that allow for expansion and contraction in the colon, facilitating the movement of waste.

What is the function of the teniae coli?

Teniae coli are three bands of muscle that run along the length of the colon, aiding in peristalsis and maintaining the shape of the colon.

Describe the mucosal layer of the large intestine.

The mucosal layer is lined with simple columnar epithelium that contains goblet cells, which secrete mucus to lubricate the passage of feces.

What is the role of the rectum in the large intestine?

The rectum stores feces until it is ready to be expelled from the body.

What is the main process accomplished by gut bacteria in the large intestine?

Fermentation of undigested nutrients, producing gas and simpler substances.

What role does mucus play in the large intestine?

To facilitate the smooth movement of stool.

What happens to bilirubin in the large intestine?

It is converted into stercobilin, giving stool its brown color.

What happens during the defecation process?

Rectal stretch receptors signal the nervous system to contract rectal muscles and relax the internal sphincter.

How much fluid is deposited into the GI tract daily?

Around 9 liters.

What is the role of water in digestion?

It helps in the chemical breakdown of food through hydrolysis and is necessary for producing digestive juices.

What distinguishes between hunger and appetite?

Hunger is a physiological need for food; appetite is a psychological desire for food.

What hormone is produced by fat cells to regulate food intake?

Leptin.

What role does the vagus nerve play in digestion?

It stimulates the parasympathetic system to enhance digestion and absorption.

What is the tens of colon peristalsis?

The slow muscular contraction that moves content through the colon.

What is the relationship between triglycerides and chylomicrons?

Triglycerides are packaged into chylomicrons for transport from the small intestine.

What is the primary function of bile salts in digestion?

To emulsify fats for easier enzymatic action.

How does the body eliminate excess cholesterol?

By excreting bile acids in feces.

What physiological change occurs when the gallbladder contracts?

Bile is released into the cystic duct and then into the common bile duct.

Describe the process of nutrient absorption in the intestinal cells.

Nutrients enter via active or facilitated transport, then reach capillaries to circulate in the bloodstream.

What is the outcome of too rapid food movement through the GI tract?

Excess secretions leading to incomplete digestion and absorption.

What are haustrae in the large intestine?

Pockets in the intestinal wall formed by contractions of the teniae coli.

What is the difference between short-term and long-term regulation of food intake?

Short-term regulation manages immediate hunger; long-term regulation is influenced by fat mass and energy reserves.