17.3
Accessory Organs
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Q1: What role do salivary glands play in digestion?
Salivary glands secrete saliva containing amylase, a digestive enzyme that begins breaking down starches and other carbohydrates before food reaches the stomach. This early enzymatic action initiates carbohydrate digestion and facilitates the overall digestive process downstream in the small intestine.
Q2: How do the liver and gallbladder work together to digest fats?
The liver produces bile, which the gallbladder stores and releases into the duodenum when needed. Bile salts contain both hydrophobic and hydrophilic areas, allowing them to emulsify large fat globules into smaller ones. This emulsification enables lipase from the pancreas to break down fats into fatty acids and triglycerides.
Q3: What enzymes does the pancreas release and what do they break down?
The pancreas secretes lipase to hydrolyze fats into fatty acids and glycerides, trypsin and chymotrypsin to break proteins into peptides, and carboxypeptidase to catabolize peptides into amino acids. It also releases amylase to digest remaining carbohydrates and bicarbonate to neutralize stomach acid in the duodenum.
Q4: What is the composition and function of bile?
Bile is a mixture of water, bile salts, cholesterol, and bilirubin, a waste product from hemoglobin breakdown. Bile salts emulsify fats by engaging with both hydrophobic and hydrophilic substances, while bilirubin gives feces its brown color and is excreted as a waste product.
Q5: How do accessory organs differ from primary digestive organs?
Accessory organs participate in digestion by secreting enzymes and substances into the digestive tract but do not come into direct contact with food like the mouth, stomach, or intestines do. They work indirectly through the biliary tree and other channels to facilitate breakdown of nutrients.
Q6: What are gallstones and what complications can they cause?
Gallstones are bile aggregations that form in the gallbladder or bile ducts. Cholesterol stones form from bile cholesterol, while pigment stones form from bilirubin. If a stone lodges in the bile duct, severe symptoms can emerge including inflammation, fever, vomiting, and jaundice, typically requiring cholecystectomy.
Q7: Why does the pancreas secrete bicarbonate into the duodenum?
The pancreas secretes bicarbonate to neutralize chyme, the acidic mixture of food and stomach acid entering the duodenum. This neutralization protects the intestinal lining from acid damage and creates an optimal pH environment for digestive enzymes to function effectively in the small intestine.