Questions and Answers
What are the 4 layers of the digestive tract?
Mucosa, submucosa, muscularis externa, serosa
Define peristalsis and segmentation.
Peristalsis: a wavelike muscle contraction that moves food bolus along esophagus; Segmentation: occurs in the small intestine, involving contraction of circular muscles to break up food and move it along the gastrointestinal tract.
Briefly describe the 6 gastrointestinal activities.
1-Ingestion, 2- Propulsion, 3- Mechanical breakdown, 4- Digestion, 5- Absorption, 6- Defecation.
What are the 3 pairs of salivary glands?
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What is the function of saliva?
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What enzymes are found in saliva?
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Briefly describe the structure of a tooth.
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What are the 4 major regions of the stomach?
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What are the four different types of cells found in the stomach wall, and what does each produce?
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Summarize the digestive processes that occur in the stomach.
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What is protein allergy and what causes it?
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What are the 3 sections of the small intestine?
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How does the structure of the small intestine contribute to the efficiency of absorption?
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What are the 3 general categories of functions of the liver?
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What are the gastric glands of the fundus and body of the stomach? What do they produce?
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What is the function of bile?
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Know the following hormones and their digestive action: gastrin, somatostatin, intestinal gastrin, secretin, CCK, GIP, and VIP.
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What are the digestive roles of the pancreas, liver, and gall bladder?
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What is produced in the large intestine during the process of absorption?
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What is the bacterial flora of the large intestine? What does it do?
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What are micelles, chylomicrons, and lipoproteins?
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Know the process of emulsification, digestion, and absorption of fats.
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Study Notes
Layers of the Digestive Tract
- Four layers: Mucosa, Submucosa, Muscularis Externa, Serosa
Peristalsis and Segmentation
- Peristalsis: Wavelike muscle contraction that moves food bolus in the esophagus.
- Segmentation: Circular muscle contractions in the small intestine that further break down food and aid in movement through the gastrointestinal tract.
Gastrointestinal Activities
- Ingestion: Taking food into the digestive system.
- Propulsion: Involves swallowing and peristalsis.
- Mechanical Breakdown: Includes chewing, mixing, churning, and segmentation.
- Digestion: Enzymatic breakdown of complex food molecules into monomers.
- Absorption: Nutrient passage into blood and lymph via transport mechanisms.
- Defecation: Elimination of indigestible substances through the anus.
Salivary Glands
- Three pairs of salivary glands: Parotid (near ears), Sublingual (under tongue), Submandibular (under mandible).
Function of Saliva
- Moistens food during digestion and initiates chemical digestion using enzymes.
Enzymes in Saliva
- Salivary Amylase: Breaks down carbohydrates.
- Lingual Lipase: Aids in fat digestion.
Tooth Structure
- Top to bottom: Crown, Neck, Root.
- Inside out: Nerves and Blood Vessels, Pulp/Root Canal, Dentin with Dentinal Tubules, Enamel.
Major Regions of the Stomach
- Cardial Part: Entry area from esophagus.
- Fundus: Dome-shaped section.
- Body: Middle section of the stomach.
- Pyloric Part: Funnel-shaped, includes Pyloric Antrum, Canal, and Sphincter.
Stomach Wall Cells
- Mucus Neck Cells: Function is not fully understood.
- Parietal Cells: Secrete intrinsic factor and components of hydrochloric acid (HCl).
- Chief Cells: Produce pepsinogen, which activates to pepsin.
- Enteroendocrine Cells: Release hormones like histamine and gastrin.
Digestive Processes in the Stomach
- Mechanical digestion through churning.
- Food storage capacity of up to 1 gallon.
- Breakdown of food facilitated by pepsin, activated by HCl.
Regulation of Gastric Juice
- Neural: ACh release stimulates gastric juice secretion.
- Hormonal: Gastrin stimulates HCl secretion.
Mechanism of HCl Secretion
- Generation of H+ and HCO3- from carbonic acid dissociation.
- H+ is pumped into lumen, K+ into cells.
- Cl- exchanged with HCO3-.
- Cl- then diffuses into the lumen.
Bile Function
- Emulsifies lipids for absorption.
Digestive Hormones
- Gastrin: Increases HCl secretion, stimulates gastric emptying.
- Somatostatin: Inhibits gastric secretions and absorption.
- Secretin: Inhibits gastric activity, increases pancreatic juice output.
- CCK: Triggers bile release and stimulates pancreatic enzyme secretion.
- GIP: Inhibits HCl production, promotes insulin release.
- VIP: Increases secretions, dilates intestinal vessels.
Digestive Role of Pancreas, Liver, and Gallbladder
- Pancreas: Produces bicarbonate and digestive enzymes.
- Gallbladder: Stores bile for fat breakdown.
- Liver: Produces bile for fat emulsification.
Mechanism for Bile and Pancreatic Juice Secretion
- CCK and secretin are released in response to fatty and acidic chyme.
- CCK induces enzymes from acinar cells, while secretin stimulates bicarbonate-rich juice from duct cells.
- Bile salts prompt liver secretion, while CCK causes gallbladder contraction.
Products of Large Intestine Absorption
- Formation of feces and gas.
Bacterial Flora in the Large Intestine
- "Friendly" bacteria aid in digestion and immunity.
Lipid Transport Mechanisms
- Micelles: Transport lipids from digestion.
- Chylomicrons: Carry dietary triglycerides, made water-soluble by protein surface.
- Lipoproteins: Transport fat and lipids in blood plasma.
Processes Involved with Fats
- Lingual lipase initiates fat digestion in the mouth.
- Gastric lipase continues in the stomach.
- Bile salts emulsify fats to facilitate pancreatic lipase action.
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Test your knowledge of the digestive system with these flashcards! This quiz covers the four layers of the digestive tract and important processes such as peristalsis and segmentation. Perfect for students studying human anatomy and physiology.