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Questions and Answers
What is the primary function of the gallbladder?
What is the primary function of the gallbladder?
Which of the following components is NOT part of the portal triad in the liver?
Which of the following components is NOT part of the portal triad in the liver?
What compound is mainly recycled in enterohepatic circulation?
What compound is mainly recycled in enterohepatic circulation?
Which condition is characterized by inflammation of the liver?
Which condition is characterized by inflammation of the liver?
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Which of the following is a function of hepatocytes in the liver?
Which of the following is a function of hepatocytes in the liver?
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What is the primary function of the muscularis externa in the stomach?
What is the primary function of the muscularis externa in the stomach?
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Which part of the stomach is responsible for the production of chyme?
Which part of the stomach is responsible for the production of chyme?
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What is the function of enteroendocrine cells in the gastric mucosa?
What is the function of enteroendocrine cells in the gastric mucosa?
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What happens if the gastroesophageal sphincter does not function properly?
What happens if the gastroesophageal sphincter does not function properly?
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Which cells in the gastric glands are responsible for secreting pepsinogen?
Which cells in the gastric glands are responsible for secreting pepsinogen?
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Which enzymes are typically released in an inactive form and activated in the small intestine?
Which enzymes are typically released in an inactive form and activated in the small intestine?
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Which of the following accurately describes a function of the alimentary canal?
Which of the following accurately describes a function of the alimentary canal?
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Which of the following enzymes is not involved in the digestion of carbohydrates?
Which of the following enzymes is not involved in the digestion of carbohydrates?
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What is not a step in the digestive processes?
What is not a step in the digestive processes?
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What facilitates the transport of monosaccharides from enterocytes into the blood?
What facilitates the transport of monosaccharides from enterocytes into the blood?
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Which accessory organ is primarily involved in the mechanical breakdown of food?
Which accessory organ is primarily involved in the mechanical breakdown of food?
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Which of the following structures is NOT a duct of the accessory organs that lead into the small intestine?
Which of the following structures is NOT a duct of the accessory organs that lead into the small intestine?
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Which of these hormones aids in regulating digestive enzyme release from accessory organs?
Which of these hormones aids in regulating digestive enzyme release from accessory organs?
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Which part of the pharynx is not involved in swallowing?
Which part of the pharynx is not involved in swallowing?
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Which statement correctly describes the anatomical structure of the esophagus?
Which statement correctly describes the anatomical structure of the esophagus?
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What is the primary function of bile salts in digestion?
What is the primary function of bile salts in digestion?
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How are lipids absorbed into enterocytes after digestion?
How are lipids absorbed into enterocytes after digestion?
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What role does the gastroesophageal sphincter play in digestion?
What role does the gastroesophageal sphincter play in digestion?
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What is the primary function of the mesentery?
What is the primary function of the mesentery?
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Which nutrient is NOT absorbed directly into blood from enterocytes?
Which nutrient is NOT absorbed directly into blood from enterocytes?
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Which of the following correctly describes the process of peristalsis?
Which of the following correctly describes the process of peristalsis?
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What is the role of the pylori bacteria in the digestive system?
What is the role of the pylori bacteria in the digestive system?
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Which phase of gastric secretion is initiated by the sight and smell of food?
Which phase of gastric secretion is initiated by the sight and smell of food?
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Which structure is primarily responsible for nutrient absorption in the small intestine?
Which structure is primarily responsible for nutrient absorption in the small intestine?
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What is the main function of the large intestine?
What is the main function of the large intestine?
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What type of cells in the small intestine are responsible for secreting mucus?
What type of cells in the small intestine are responsible for secreting mucus?
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Which structure regulates the entry of chyme from the small intestine into the large intestine?
Which structure regulates the entry of chyme from the small intestine into the large intestine?
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What type of teeth are typically absent in adults?
What type of teeth are typically absent in adults?
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What is one of the main functions of the bacterial microbiota in the large intestine?
What is one of the main functions of the bacterial microbiota in the large intestine?
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What is the primary function of brush border enzymes in the small intestine?
What is the primary function of brush border enzymes in the small intestine?
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Which process in the digestive system is characterized by rhythmic contractions to mix and propel contents?
Which process in the digestive system is characterized by rhythmic contractions to mix and propel contents?
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Study Notes
Digestive System
- Alimentary canal/gastrointestinal (GI) tract/digestive tract/gut: Digests food, absorbs nutrients, open to the outside
- Accessory organs: Teeth, tongue, gallbladder, glands (salivary glands, liver, pancreas)
- Digestive processes: Ingestion, mechanical breakdown, propulsion (swallowing/deglutition, peristalsis, segmentation), digestion (3 major steps: sensory receptors detect stimuli, smooth muscle and glands respond, neurons and hormones regulate actions), absorption, defecation
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Peritoneum: A serous membrane that lines the abdominal cavity
- Mesentery: Holds organs in place (greater omentum, lesser omentum, transverse mesocolon)
- Retroperitoneal vs peritoneal: Retroperitoneal organs are located behind the peritoneum, while peritoneal organs lie within the peritoneum
Major organs of the alimentary canal
- Mouth: Ingestion and mastication, contains stratified squamous epithelium, salivary amylase, palate (hard and soft), uvula, vestibule, gingivae, labial frenula
- Pharynx: Nasopharynx, oropharynx, laryngopharynx
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Esophagus: Stratified squamous epithelium, submucosa, muscularis externa, adventitia, lumen usually closed, gastroesophageal sphincter/lower esophageal sphincter/cardial sphincter
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Deglutition (swallowing) process:
- Buccal phase
- Pharyngeal-esophageal phase
- Peristalsis
- Gastroesophageal sphincter (issues arise when this sphincter doesn't function correctly)
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Deglutition (swallowing) process:
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Stomach: Cardia, fundus, body, pyloric parts (pylorus), greater curvature, lesser curvature, rugae, muscularis externa has an additional layer (oblique layer), produces chyme
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Histology: Gastric pits, gastric glands
- Parietal cells: Produce HCl and intrinsic factor
- Chief cells: Produce pepsinogen (and some lipases), pepsinogen to pepsin reaction, pepsin enzyme function
- Enteroendocrine cells: Produce gastrin, histamine, and other hormones
- Gastric ulcer: H.pylori bacteria
- Mechanical processes: Mixing and churning of food
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Regulation of digestive activities:
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Gastric secretions (neural and hormonal controls):
- Cephalic phase
- Gastric phase
- Intestinal phase
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Gastric motility & emptying:
- Stretch
- Peristalsis
- Duodenum
- Type of food consumed
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Gastric secretions (neural and hormonal controls):
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Histology: Gastric pits, gastric glands
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Small intestine: Duodenum, jejunum, ileum, circular folds, villi, microvilli (brush border)
- Brush border enzymes: Important for digestion
- Histology: Enterocytes, goblet cells, enteroendocrine cells, Paneth cells (intestinal crypts), stem cells
- Lymphatic system: MALT/Peyer’s patches, lacteals
- Digestive activities: Digestion and absorption of most nutrients
- Regulation of activities: Chyme entry, motility
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Large intestine: Ileocecal valve, cecum, appendix, colon (ascending, transverse, descending, sigmoid), rectum, anus
- Histology: Thick mucosa, big crypts with many goblet cells (lots of mucus), bacterial microbiota
- Processes of movement: Segmentation, peristalsis (mass movements), defecation
Accessory organs of the digestive system
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Mouth:
- Tongue: Tastebuds
- Teeth: Deciduous/milk/baby/primary teeth, permanent teeth (incisors, canines/eyetooth/cuspids, bicuspids/premolars, molars)
- Enamel, dentin, pulp: Components of teeth
- Crown, root, neck, gingiva: Parts of a tooth
- Lips & cheeks: Help with food manipulation
- Salivary glands: Parotid salivary gland, sublingual salivary gland, Submandibular salivary gland
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Liver & gallbladder:
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Liver: Many functions, produces bile (digestive function)
- Lobes: Right, left, caudate, quadrate
- Falciform ligament: Separates right and left lobes
- Bare area: Located on the posterior side of the liver
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Liver lobules:
- Portal triad: Bile duct (transports bile), portal vein, portal arteriole
- Central vein: Carries blood away from the lobule
- Liver sinusoids: Capillary-like channels that carry blood
- Bile: Contains bile pigments (bilirubin), bile salts (recycling), phospholipids
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Gallbladder: Stores bile
- Cystic duct: Connects gallbladder to the bile duct
- Homeostatic imbalances of the liver and gallbladder: Hepatitis (viruses, alcohol, drugs, wild mushrooms, non-alcoholic fatty liver disease - NAFLD), cirrhosis, gallstones, jaundice
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Liver: Many functions, produces bile (digestive function)
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Pancreas:
- Acini: Acinar cells produce enzymes (proteases, amylase, lipases, nucleases)
- Duct cells: Secrete bicarbonate
- Enzymes usually released in inactive form and activated in the small intestine
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Ducts of accessory organs:
- Right and Left hepatic ducts (Liver), common hepatic duct (liver), cystic duct (gallbladder), bile duct (bile from liver and gallbladder), main pancreatic duct
- Hepatopancreatic ampulla & sphincter, major duodenal papilla
- CCK and secretin: Hormones that regulate digestive enzyme, bile, and bicarbonate release
Physiology of digestion & absorption
-
Carbohydrates:
- Salivary amylase, pancreatic amylase: Break down starch into simpler sugars
- Brush border enzymes: Break down disaccharides into monosaccharides
- Poly-, oligo-, disaccharides vs monosaccharides: Types of carbohydrates, polymers vs monomers
- Transport of monosaccharides: Into enterocytes and out of enterocytes into the blood/body tissues
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Proteins:
- Pepsinogen → pepsin: Pepsin breaks down proteins
- Pancreatic proteases: Trypsin, chymotrypsin
- Carboxypeptidases: Break down proteins
- Brush border enzymes: Aminopeptidases, carboxypeptidases, dipeptidases
- Amino acids: Monomers, transport into and out of enterocytes and into the blood
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Lipids:
- Lipases: Found throughout the digestive tract
- Emulsification: Bile salts break down fat globules
- Digestion: Pancreatic lipase breaks down fats
- Micelle formation: Enhances fat absorption
- Diffusion: Into enterocytes
- Chylomicron formation and transport: Transport lipids through the lymphatic system
- Lipoprotein lipase: Breaks down chylomicrons
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Absorption:
- Vitamins: Diverse mechanisms depending on their solubility
- Electrolytes: Na+, Cl-, HCO3-, K+, iron, Ca2+
- Water: Absorbed primarily in the small intestine
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Description
Test your knowledge on the digestive system, including the structures and functions of the alimentary canal and accessory organs. This quiz covers the major processes involved in digestion, absorption, and the role of the peritoneum and its components.
