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Questions and Answers
Which of the following statements about keto acids is correct?
Which of the following statements about keto acids is correct?
Which component is absent in saliva?
Which component is absent in saliva?
What is the main function of the enzyme amylase?
What is the main function of the enzyme amylase?
Which duct is responsible for delivering pancreatic juice to the small intestine?
Which duct is responsible for delivering pancreatic juice to the small intestine?
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Which of the following substances is NOT secreted in the stomach?
Which of the following substances is NOT secreted in the stomach?
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Where does chemical and mechanical digestion begin?
Where does chemical and mechanical digestion begin?
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What is formed in the mouth after food is moistened and chewed?
What is formed in the mouth after food is moistened and chewed?
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What cell produces an acidic environment in the stomach?
What cell produces an acidic environment in the stomach?
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How many sphincters does the anus contain?
How many sphincters does the anus contain?
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What is the primary function of saliva in the digestive process?
What is the primary function of saliva in the digestive process?
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What role does the liver play in protein metabolism?
What role does the liver play in protein metabolism?
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Which part of the digestive system is primarily responsible for nutrient absorption?
Which part of the digestive system is primarily responsible for nutrient absorption?
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Which of the following components are synthesized in the urea cycle?
Which of the following components are synthesized in the urea cycle?
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Study Notes
Digestive System Overview
- The digestive system is responsible for breaking down food, absorbing nutrients, and eliminating waste.
- The process involves ingestion, mastication (chewing), digestion, secretion, absorption, compaction, and defecation.
- Key structures include the oral cavity, esophagus, stomach, small intestine, large intestine, and anus.
- Accessory organs such as salivary glands, liver, pancreas, and gall bladder support digestion.
Digestive System Functions
- Ingestion: Intake of food.
- Mastication: Chewing food.
- Digestion: Breaking down food into smaller molecules.
- Secretion: Release of digestive enzymes and other substances.
- Absorption: Uptake of nutrients.
- Compaction: Consolidation of indigestible material.
- Defecation: Elimination of waste.
Digestive System Structures
- Oral cavity: Mouth, teeth, tongue. Digestion begins here via both mechanical and chemical processes.
- Esophagus: Tube connecting mouth to stomach.
- Stomach: Food storage and initial protein digestion (acidic environment).
- Small intestine: Major site of nutrient absorption. Divided into duodenum, jejunum, and ileum.
- Large intestine: Absorbs water and electrolytes; stores waste as feces. Subdivided into ascending, transverse, descending and sigmoid colon
Accessory Organs
- Salivary glands: Produce saliva.
- Liver: Produces bile for fat digestion.
- Pancreas: Creates pancreatic juices with enzymes for digesting carbs, proteins, and fats.
- Gall bladder: Stores bile
Histology of the Alimentary Canal
- The alimentary canal has four layers, the innermost being mucosa, followed by submucosa, muscularis, and serosa.
- Mucosa contains epithelial cells, lamina propria, and muscularis mucosae. The submucosa contains connective tissue, glands, and blood vessels.
- Muscularis includes circular and longitudinal muscle layers for movement.
- Serosa is the outermost layer, with connective tissue and epithelium.
Digestion of Food in the Mouth
- Saliva starts digestion, lubricating food, using digestive enzymes to breakdown carbohydrates and providing immune function.
Chemical and Mechanical Digestion
- Chemical digestion starts in the mouth with amylase.
- Mechanical digestion also begins in the mouth through chewing.
Bolus Formation
- Formed after food is moistened (masticated and secreted) in the mouth.
Acidic Environment in the Stomach
- Parietal cells secrete acid.
Stomach Structure
- Various parts of the stomach include the fundus, cardia, body, and antrum.
- The stomach contains folds (rugae) for expansion. Stomach lining has gastric glands with different cell types and important functions including mucous cells, parietal cells, chief cells, and G cells.
Liver, Pancreas, and Gall Bladder
- The liver produces bile. It is stored in the gall bladder.
- The pancreas produces juices with digestive enzymes.
Small Intestine Parts and Functions
- Small intestine has three parts (duodenum, jejunum, ileum). The bulk of chemical digestion and absorption happens in the small intestine.
- Chemical digestion continues, and most nutrient absorption happens here.
Intestines and Skeletal Muscle
- The intestines are not composed of skeletal muscle.
Large Intestine Functions
- Reabsorbs water and electrolytes from indigestible food.
- Compacts indigestible material into feces.
- Vitamins created by bacteria are absorbed.
Number of Anus Sphincters
- The anus contains two sphincters.
Carbohydrate Digestion Process
- Dietary carbohydrates are ingested and digested in the mouth by salivary amylase.
- Digestion continues in the stomach and small intestines with the help of pancreatic amylase, lactase, sucrase, and maltase.
- Monosaccharides (glucose, galactose, and fructose) are absorbed into the blood stream via active transport.
Fate of Glucose
- High blood glucose stimulates insulin release, leading to glycogen storage in the liver and tissues.
- Low blood glucose stimulates glucagon release, leading to glycogen breakdown in the liver and tissues, raising blood sugar levels.
Protein Digestion Process
- Begins in the stomach with denaturation
- Proteases like pepsin, trypsin, and chymotrypsin continue digestion into peptides.
- Amino acids are absorbed into blood (active transport).
Fate of Proteins
- Proteins are broken down into amino acids.
- Amino acids can be used to form glucose or ketone bodies during fasting.
- Urea is produced in the liver from ammonia.
- Amino acids may be converted into other amino acids, or used for fatty acid/lipid synthesis, or broken down for energy/ATP.
- Proteins are built (anabolism via amino acids)
Lipid Digestion Process
- Lipids are emulsified by bile salts in the small intestine.
- Enzymes like pancreatic lipase break down fats into monoglycerides and fatty acids.
- These are absorbed into the lymphatic system, forming chylomicrons.
Saliva Composition
- Saliva contains amylase and antibodies, but not pepsinogen (pepsinogen is an enzyme not found in saliva).
Pancreatic Juice Delivery
- Pancreatic juice is delivered to the small intestine via the pancreatic duct.
Amylase Enzyme Function
- Amylase chemically digests carbohydrates.
Protein Component Not Secreted in the Stomach
- Amylase is not a substance secreted by the stomach.
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Description
Test your knowledge on the digestive system with this quiz covering its functions and key structures. From ingestion to defecation, explore how the body processes food and absorbs nutrients. Challenge yourself and learn about the accessory organs that support digestion.
