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Questions and Answers
What is the primary function of the human digestive system?
Which organ in the digestive system is responsible for the production of intrinsic factor?
Where does absorption primarily occur in the digestive system?
Which organ is considered an accessory digestive organ despite not being part of the gastrointestinal tract?
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What is the main function of the exocrine glands in the digestive system?
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What is the basic structure present in all regions of the gastrointestinal tract?
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What is the initial breakdown product of plant starch in the mouth?
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Which enzyme completes the digestion of starch in the duodenum?
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Which enzyme is responsible for splitting sucrose into glucose and fructose?
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Which part of the digestive system has the highest capacity for absorbing sugars?
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What are the final products of oligosaccharide digestion in the duodenal and jejunal brush border?
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Which enzyme debranches α-limit dextrins for further digestion?
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What stimulates bicarbonate and water release from pancreatic duct cells?
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Which hormone stimulates pancreatic acinar cells to secrete large quantities of digestive enzymes?
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What potentiates the effects of CCK on acinar cell enzyme secretion?
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Which reflex modulates cholinergic regulation during pancreatic secretion?
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What stimulates the release of CCK from enteroendocrine I cells in the small intestine?
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Which neurotransmitter plays a critical role in vagovagal and enteropancreatic reflexes during pancreatic secretion?
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What condition may cause increased levels of unconjugated bilirubin?
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Which syndrome is a rare hereditary defect in liver enzymes involved in processing bilirubin?
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What can lead to post-hepatic jaundice due to increased conjugated bilirubin levels?
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Which condition arises from a disruption in the normal drainage of conjugated bilirubin into the intestine?
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What is a hepatic cause of jaundice that can be a side effect of certain medications?
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Which condition can cause post-hepatic jaundice by obstructing the normal drainage of conjugated bilirubin?
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What initiates a second electrical event known as the spike or action potential in gastrointestinal smooth muscle cells?
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Which region of the stomach primarily exhibits phasic contractions?
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What type of contraction maintains a constant level of contraction ('tone') without regular periods of relaxation?
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Which cells are responsible for causing slow waves or basic electrical rhythm in gastrointestinal smooth muscles?
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In which part of the gastrointestinal tract does receptive relaxation occur during peristalsis?
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What triggers the contraction of the circular muscle segment during peristalsis?
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Which type of movement allows greater mixing with the secretions of the intestines in the gastrointestinal tract?
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What is the localized contraction of circular smooth muscles that constricts the intestine into segments for mixing and exposure to nutrients?
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Which structure controls the process of peristalsis in the gastrointestinal tract?
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"Mixing movements" in the small and large intestines are primarily characterized by:
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Study Notes
Digestive System
- The human digestive system is a series of organs that converts food into essential nutrients and eliminates waste material.
Functions of the Digestive System
- Processes food into essential nutrients
- Absorbs nutrients into the body
- Eliminates waste material
- Reabsorbs water, minerals, and vitamins
- Forms feces and produces defecation
Components of the Digestive System
- Gastrointestinal (GI) tract or alimentary canal
- Accessory digestive organs (teeth, tongue, salivary glands, liver, gallbladder, pancreas)
GI Tract
- A continuous tube with two openings (mouth and anus)
- Approximately 7 meters long
- Includes mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus
Accessory Digestive Organs
- Situated outside the GI tract
- Essential for the digestive process
- Most are exocrine glands that secrete digestive juices
Basic Structure of the GI Tract
- A muscular tube lined with a special layer of epithelial cells
- The entire tract has a similar basic structure with regional variations
- The wall has four basic layers/tunics
Causes of Jaundice
- Hepatic causes (hepatitis, cirrhosis, liver cancer, rare hereditary defects)
- Post-hepatic causes (gallstone formation, pancreatic cancer, pancreatitis, biliary atresia)
Digestion and Absorption of Carbohydrates
- Complex carbohydrates broken down into monosaccharides
- Dietary carbohydrates include plant starch, animal starch, disaccharides, monosaccharides, and cellulose
- Digestion begins in the mouth with salivary amylase
- No significant digestion occurs in the stomach
- Starch digestion completed in the duodenum by pancreatic amylase
- Further digestion of oligosaccharides occurs in the duodenum and jejunum
- Absorption occurs in the duodenum and upper jejunum
Motor Function of the GI Tract
- Gastrointestinal (GI) motility refers to the movement of food from the mouth to the anus
- Motor function depends on the contraction of smooth muscle cells
- Coordinated contractions of smooth muscle cells produce motor patterns of GI motility
- Smooth muscle cells are electrically connected through gap junctions
Electrical Activity
- Slow waves or basic electrical rhythm (BER) occur in the membrane of GI smooth muscles
- Slow waves bring the membrane potential to a threshold level, eliciting a spike or action potential
- Pacemaker cells (interstitial cells of Cajal) clustered in the muscle layers of the GI tract
- Factors contributing to depolarization include distension, acetylcholine stimulation, parasympathetic stimulation, and gastrointestinal hormones
Types of Motility
- Propulsive contractions/peristalsis (moves material in the aboral direction)
- Mixing/segmentation contractions (moves material in both directions, allowing for greater mixing with intestinal secretions)
Peristalsis
- Primarily moves material in the aboral direction
- Occurs in the esophagus, stomach, small intestine, and large intestine
- Triggered by distension, chemical stimuli, or strong parasympathetic activation
- Controlled by the Auerbach's (myenteric) plexus
Segmentation/Mixing Movements
- Occur in the small intestine and large intestine
- Predominates in the small intestine
- Moves chyme in both directions, allowing for greater mixing with intestinal secretions
- Ensures that the entire volume of nutritionally important components is exposed to enzymes and absorbed by the intestine
Swallowing (Deglutition)
- Involves the movement of substances from the mouth to the stomach via the pharynx and esophagus
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Description
Test your knowledge on the functions of the human digestive system including food processing, absorption, and elimination processes. Learn about how essential nutrients are absorbed and waste material is eliminated.
