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Questions and Answers
What is the approximate length of the alimentary canal from mouth to anus?
What is the approximate length of the alimentary canal from mouth to anus?
What type of epithelium is found in the mouth, esophagus, and anal canal?
What type of epithelium is found in the mouth, esophagus, and anal canal?
What is the function of the lamina propria in the GI tract?
What is the function of the lamina propria in the GI tract?
What is the role of the muscularis layer in the GI tract?
What is the role of the muscularis layer in the GI tract?
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What is the function of the submucosal plexus in the GI tract?
What is the function of the submucosal plexus in the GI tract?
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What is the primary function of the digestive system?
What is the primary function of the digestive system?
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What is the primary function of chemical digestion?
What is the primary function of chemical digestion?
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Which type of control mechanism involves sensors for expansion of the stomach?
Which type of control mechanism involves sensors for expansion of the stomach?
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What stimulates the release of gastric acid in the digestive system?
What stimulates the release of gastric acid in the digestive system?
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Which part of the oral cavity prevents food from entering the nasal cavity?
Which part of the oral cavity prevents food from entering the nasal cavity?
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What is the role of secretin in digestion?
What is the role of secretin in digestion?
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Which organ plays a role in both digestion and respiration?
Which organ plays a role in both digestion and respiration?
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Where does most absorption take place in the digestive system?
Where does most absorption take place in the digestive system?
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Which hormone initiates peristalsis in the small intestine?
Which hormone initiates peristalsis in the small intestine?
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What is the primary digestive organ in the digestive system?
What is the primary digestive organ in the digestive system?
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Which section of the small intestine has more mucosal folds, making it thicker and more vascular?
Which section of the small intestine has more mucosal folds, making it thicker and more vascular?
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What is the function of circular folds, villi, and microvilli in the small intestine?
What is the function of circular folds, villi, and microvilli in the small intestine?
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At what rate is digestion most rapid in the duodenum?
At what rate is digestion most rapid in the duodenum?
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Which organ finishes absorption, forms feces, and eliminates them?
Which organ finishes absorption, forms feces, and eliminates them?
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What is the function of the internal anal sphincter in the anal canal?
What is the function of the internal anal sphincter in the anal canal?
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Where do mass movements start and what is their purpose?
Where do mass movements start and what is their purpose?
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What is the main role of trillions of bacteria in the large intestine?
What is the main role of trillions of bacteria in the large intestine?
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Which segment of the large intestine continues absorption of water and salts?
Which segment of the large intestine continues absorption of water and salts?
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Where does carbohydrate digestion primarily begin?
Where does carbohydrate digestion primarily begin?
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How are lipids mainly broken down in the digestive system?
How are lipids mainly broken down in the digestive system?
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Which enzyme breaks down proteins into amino acids in the small intestine?
Which enzyme breaks down proteins into amino acids in the small intestine?
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What primarily buffers acidic juice and inactivates pepsin to create an optimal environment in the digestive system?
What primarily buffers acidic juice and inactivates pepsin to create an optimal environment in the digestive system?
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How are disaccharides broken down for absorption in the body?
How are disaccharides broken down for absorption in the body?
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Which part of the GI tract absorbs most of the minerals and electrolytes balanced by the sodiumpotassium pump?
Which part of the GI tract absorbs most of the minerals and electrolytes balanced by the sodiumpotassium pump?
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Study Notes
Overview of the Digestive System
- The alimentary canal, also known as the gastrointestinal (GI) tract, is a 25 ft long tube that extends from the mouth to the anus.
- The GI tract is composed of four layers: mucosa, submucosa, muscularis, and serosa.
- The digestive system breaks down food to release and absorb nutrients.
GI Tract Layers
- Mucosa: the innermost layer, composed of a mucous membrane epithelium that comes into contact with food, and a lamina propria with blood and lymphatic vessels.
- The mucosa contains epithelial cells, goblet cells, and enteroendocrine cells.
- Muscularis mucosa: a layer of smooth muscle that is always in a state of tension.
Layers
- Submucosa: a layer of dense connective tissue between the mucosa and muscularis, containing blood and lymphatic vessels, and a collection of nerves called the submucosal plexus.
- Muscularis: a layer of smooth muscle that is responsible for mechanical digestion and peristalsis.
Digestive Processes
- Mechanical digestion: the physical breakdown of food into smaller particles.
- Chemical digestion: the breakdown of complex food molecules into their building blocks using enzymes, acid, and salts.
- Absorption: the process of taking nutrients into the bloodstream or lipids into the lymphatic system.
- Defecation: the removal of undigested materials from the body.
Regulatory Mechanisms
- Neural control: the regulation of digestive processes through sensors and reflexes.
- Hormonal control: the regulation of digestive processes through hormones such as gastrin, secretin, and CCK.
Mouth, Pharynx, and Esophagus
- Mouth: the oral cavity, responsible for mechanical and chemical digestion, and respiration.
- Tongue: involved in ingestion, mechanical and chemical digestion, swallowing, and vocalization.
- Pharynx: a tube that connects the mouth to the esophagus.
- Esophagus: a muscular tube that propels food into the stomach.
The Small and Large Intestine
- Small intestine: the primary site of digestion and absorption, with a huge surface area.
- The small intestine is composed of three regions: duodenum, jejunum, and ileum.
- Large intestine: responsible for the final absorption of water and electrolytes, and the formation and elimination of feces.
Mechanical Digestion
- Peristalsis: the movement of chyme through the intestine, stimulated by the hormone motilin.
- Segmentation: the back and forth contractions of the intestine to mix chyme with digestive juices.
Chemical Digestion
- Finishes the digestion of carbohydrates and proteins.
- Most lipids are undigested and require bile and pancreatic lipase for digestion.
- Most water is absorbed through osmosis.
Large Intestine
- Composed of four regions: cecum, colon, rectum, and anal canal.
- The large intestine is responsible for the final absorption of water and electrolytes, and the formation and elimination of feces.
- Bacterial flora: trillions of nonpathogenic bacteria live in the large intestine, facilitating digestion, absorption, and synthesis of certain vitamins.
Bile and Pancreatic Juice
- Bile: stored in the gallbladder, and released into the duodenum to aid in fat digestion.
- Pancreatic juice: released into the duodenum to aid in carbohydrate, protein, and fat digestion.
Digestion and Absorption
- Digestion is accomplished through enzymes and hydrolysis, requiring ATP.
- The body absorbs monosaccharides, breaks down disaccharides and polysaccharides, but cannot break down fiber.
- Carbohydrate digestion begins in the mouth and continues in the small intestine.
- Protein digestion begins in the stomach and continues in the small intestine.
- Lipid digestion occurs mainly in the small intestine.
- Minerals are absorbed and balanced by the sodium-potassium pump, requiring ATP.
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Description
Test your knowledge on the overview of the digestive system and the layers of the gastrointestinal (GI) tract. Topics include the breakdown of food to absorb nutrients, the components of the alimentary canal, and the roles of accessory digestive organs.
