Podcast
Questions and Answers
What initiates gastric emptying from the stomach into the small intestine?
What initiates gastric emptying from the stomach into the small intestine?
- Release of gastrin hormone
- Peristalsis of smooth muscle contractions (correct)
- Presence of fat in the stomach
- High acidity in the stomach
Which group of cells in the stomach is responsible for releasing hydrochloric acid (HCl)?
Which group of cells in the stomach is responsible for releasing hydrochloric acid (HCl)?
- Chief cells
- G cells
- Mucous cells
- Parietal cells (correct)
What effect does high levels of fat in the small intestine have on gastric emptying?
What effect does high levels of fat in the small intestine have on gastric emptying?
- Inhibits gastric emptying (correct)
- Stimulates gastric emptying
- Has no effect on gastric emptying
- Delays gastric emptying temporarily
What is the primary function of the duodenum in the small intestine?
What is the primary function of the duodenum in the small intestine?
Which of the following is NOT an exocrine cell type found in the gastric pits?
Which of the following is NOT an exocrine cell type found in the gastric pits?
Where does the majority of nutrient absorption occur in the small intestine?
Where does the majority of nutrient absorption occur in the small intestine?
What is the primary role of chief cells in the stomach?
What is the primary role of chief cells in the stomach?
Which structure primarily functions to neutralize stomach acid entering the duodenum?
Which structure primarily functions to neutralize stomach acid entering the duodenum?
What is the role of Peyer's Patches found in the ileum?
What is the role of Peyer's Patches found in the ileum?
What is segmentation in the context of the small intestine?
What is segmentation in the context of the small intestine?
What is the main function of saliva in the oral cavity?
What is the main function of saliva in the oral cavity?
Which type of teeth is primarily responsible for tearing food?
Which type of teeth is primarily responsible for tearing food?
What is the primary enzyme found in saliva that aids in carbohydrate digestion?
What is the primary enzyme found in saliva that aids in carbohydrate digestion?
What structural feature of the oral cavity helps in guiding and containing food during chewing?
What structural feature of the oral cavity helps in guiding and containing food during chewing?
What process is described as mechanical digestion in the oral cavity?
What process is described as mechanical digestion in the oral cavity?
How many deciduous teeth does a human typically have?
How many deciduous teeth does a human typically have?
Which component of saliva primarily helps to clean the mouth?
Which component of saliva primarily helps to clean the mouth?
What is the role of the tongue in the oral cavity?
What is the role of the tongue in the oral cavity?
What is the primary function of the pharynx?
What is the primary function of the pharynx?
What type of muscle is present in the upper third of the esophagus?
What type of muscle is present in the upper third of the esophagus?
During which phase of swallowing does the epiglottis fold to close off the windpipe?
During which phase of swallowing does the epiglottis fold to close off the windpipe?
What triggers the opening of the lower esophageal sphincter?
What triggers the opening of the lower esophageal sphincter?
What kind of muscle is found in the lower third of the esophagus?
What kind of muscle is found in the lower third of the esophagus?
What is the duration of the swallowing process, from beginning to end?
What is the duration of the swallowing process, from beginning to end?
Which phase of swallowing can be initiated voluntarily?
Which phase of swallowing can be initiated voluntarily?
What mechanism primarily moves the bolus toward the stomach during the esophageal phase?
What mechanism primarily moves the bolus toward the stomach during the esophageal phase?
What is the primary function of the intestinal phase during digestion?
What is the primary function of the intestinal phase during digestion?
Which hormones are released from the duodenum and inhibit gastric secretions?
Which hormones are released from the duodenum and inhibit gastric secretions?
What triggers the activation of the pancreas to release bicarbonate in the intestinal phase?
What triggers the activation of the pancreas to release bicarbonate in the intestinal phase?
What is the role of stretch and chemoreceptors in the duodenum during the intestinal phase?
What is the role of stretch and chemoreceptors in the duodenum during the intestinal phase?
Which reflex is responsible for increasing motility and secretion throughout the small intestine due to stomach distension?
Which reflex is responsible for increasing motility and secretion throughout the small intestine due to stomach distension?
What is the primary function of villi in the small intestine?
What is the primary function of villi in the small intestine?
What is the effect of the gastroileal reflex in the digestive process?
What is the effect of the gastroileal reflex in the digestive process?
What structural feature of the small intestine helps further increase the surface area for absorption beyond villi?
What structural feature of the small intestine helps further increase the surface area for absorption beyond villi?
What is the primary function of the cephalic phase of digestion?
What is the primary function of the cephalic phase of digestion?
What sensory triggers can initiate the cephalic phase?
What sensory triggers can initiate the cephalic phase?
Which nerve is primarily involved in the signaling of the cephalic phase?
Which nerve is primarily involved in the signaling of the cephalic phase?
During the gastric phase, which of the following physiological changes occurs in the stomach?
During the gastric phase, which of the following physiological changes occurs in the stomach?
Which receptors are stimulated during the gastric phase due to the distension of the stomach?
Which receptors are stimulated during the gastric phase due to the distension of the stomach?
What role does the myenteric plexus play during the gastric phase?
What role does the myenteric plexus play during the gastric phase?
What type of cells in the stomach secrete hydrochloric acid (HCl)?
What type of cells in the stomach secrete hydrochloric acid (HCl)?
What is the primary consequence of the stimulation of secretory cells during both the cephalic and gastric phases?
What is the primary consequence of the stimulation of secretory cells during both the cephalic and gastric phases?
Flashcards
Sphincter
Sphincter
A circular muscle that controls the opening and closing of a body passage.
Peristalsis
Peristalsis
Waves of muscle contractions that move food along the digestive tract.
Gastric Mixing
Gastric Mixing
The churning motion of the stomach that mixes food with gastric juices.
Gastric Emptying
Gastric Emptying
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Chief cells
Chief cells
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Intestinal Phase
Intestinal Phase
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Enterogastric Reflex
Enterogastric Reflex
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Hormones in the Intestinal Phase
Hormones in the Intestinal Phase
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CCK (Cholecystokinin)
CCK (Cholecystokinin)
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Secretin
Secretin
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GIP (Gastric Inhibitory Polypeptide)
GIP (Gastric Inhibitory Polypeptide)
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Plicae Circulares
Plicae Circulares
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Villi
Villi
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Pharynx
Pharynx
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Esophagus
Esophagus
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Swallowing (Deglutition)
Swallowing (Deglutition)
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Buccal Phase
Buccal Phase
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Pharyngeal Phase
Pharyngeal Phase
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Esophageal Phase
Esophageal Phase
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Lower Esophageal Sphincter
Lower Esophageal Sphincter
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Cephalic Phase
Cephalic Phase
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Role of Vagus Nerve in Cephalic Phase
Role of Vagus Nerve in Cephalic Phase
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Submucosal Plexus Role in Cephalic Phase
Submucosal Plexus Role in Cephalic Phase
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Gastric Juice Components
Gastric Juice Components
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Gastric Phase
Gastric Phase
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Gastric Phase Stimuli
Gastric Phase Stimuli
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Role of Myenteric Plexus in Gastric Phase
Role of Myenteric Plexus in Gastric Phase
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Gastric Secretion Regulation
Gastric Secretion Regulation
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Duodenum
Duodenum
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Jejunum
Jejunum
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Ileum
Ileum
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Brunner's glands
Brunner's glands
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Segmentation
Segmentation
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What are the four main parts of the mouth?
What are the four main parts of the mouth?
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What is mastication?
What is mastication?
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What is saliva?
What is saliva?
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What are the functions of saliva?
What are the functions of saliva?
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What's the difference between deciduous and succedaneous teeth?
What's the difference between deciduous and succedaneous teeth?
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What are the functions of the tongue?
What are the functions of the tongue?
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What are the types of teeth?
What are the types of teeth?
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What is a bolus?
What is a bolus?
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Study Notes
Digestive System - Part 2
- The digestive system, Part 2, covers the oral cavity, pharynx, esophagus, stomach and small intestine.
Oral Cavity/Mouth
- Structures: Hard palate, soft palate, teeth, tongue, salivary glands, uvula, palatine tonsil.
- Functions: Mechanical breakdown (chewing), some chemical breakdown (enzymes begin digestion), no absorption.
Mechanical Digestion
- Oral cavity: Lips, cheeks, and palate guide and contain food.
- Mastication: Mechanical digestion by teeth.
- Saliva: Produced by salivary glands and released into the mouth (99.5% water, electrolytes, mucus).
- Salivary Amylase: Enzyme for carbohydrate digestion.
- Lysozyme: Antibacterial enzyme.
- Saliva also aids in motility, taste, cleaning the mouth, and speaking.
Tongue
- Structure: Skeletal muscle.
- Function: Mechanical breakdown; mixes food with saliva and compacts it into a bolus.
Teeth
- Two sets: Deciduous (primary) teeth - 20, Permanent teeth - 32
- There are different types of teeth (incisors, canines, premolars, molars).
Pharynx
- Structure: Shared passageway for air and food.
- Function: Food travels from the mouth through the oropharynx and laryngopharynx to the esophagus. It aids in swallowing.
Esophagus
- Structure: Muscular tube from the pharynx to the stomach.
- Layers: Upper 1/3 – skeletal muscle, middle 1/3 - mixed, lower 1/3 - smooth muscle
- Path: Posterior to the trachea, travels through the diaphragm before entering the stomach.
- Function: Aids in swallowing.
Swallowing (Deglutition)
- Total time: ~9 seconds.
- Phases: Buccal, pharyngeal, esophageal.
- Each phase, with specific steps, is discussed in detail.
Esophageal Sphincters
- Function: Regulate the flow of food/liquid and prevents backflow or air entering wrong pathways
- Pharyngoesophageal sphincter: Between the pharynx and esophagus - Prevents air from entering when food is not being swallowed.
- Gastroesophageal sphincter: Between the esophagus and stomach – Controls the entry of food and prevents stomach acid backflow.
Stomach Functions
- Storage: Large volume (50ml empty; 1000ml full), Chyme = partially digested food.
- Movement: Peristalsis.
- Secretion: Gastric juices.
- Digestion: Mostly proteins and some carbohydrates.
- Absorption: Alcohol and Aspirin.
Anatomy of the Stomach
- Curvatures: Lesser (medial concave), Greater (lateral convex).
- Parts: Cardia, Fundus, Body, Pylorus.
- Muscle layers: Longitudinal, circular, oblique
- Rugae: Folds in the stomach lining that allow expansion.
- Pyloric Region: Funnel-shaped, continuous with the small intestine via the pyloric sphincter
Peristalsis
- Mechanism: Waves of smooth muscle contractions.
- Role: Mechanically breaks down food, and moves food to the small intestines.
- Regulation: Controlled by factors including food volume, fluidity, fat, acid; stress.
Gastric Juices: Gastric Pits & Glands
- Gastric Pits: Extension of epithelium into the lamina propria
- Gastric Glands: Contain 4 types of cells that make gastric juices.
Stomach Cells (in Gastric pits)
- Exocrine cells: Mucous cells (protective mucus), Chief cells (pepsinogen), Parietal cells (HCl and intrinsic factor).
- Endocrine cells: G cells (gastrin), ECL cells (histamine), D cells (somatostatin).
Stomach: HCI Functions
- Main functions: Activates pepsin for protein digestion, breaks down tough fibers, denatures proteins, kills bacteria.
The Stomach Mucosa and the Gastric Glands (Table)
- Tables provide detailed information on the type of secretory cell, product secreted, stimuli for secretion, and its functions.
Regulation of Gastric Activity
- Controls: CNS & ENS; hormones.
- Phases: Cephalic, gastric, intestinal.
Cephalic Phase
- Duration: Short (2-10 minutes).
- Stimuli: Sight, smell, taste, or thoughts of food.
- Response: Increased gastric juice production (approximately 500ml/hour), preparation of stomach to receive food. The vagus nerve (N X) plays a key role.
Gastric Phase
- Duration: 2-4 hours.
- Stimuli: Arrival of food (stretch & pH) leads to increased gastric juice production and stomach motility.
- Response: The submucosal and myenteric plexuses signal to secretory cells/smooth muscle to prepare digestion.
Intestinal Phase
- Function: Controls the rate of gastric emptying.
- Stimuli: Food entering the duodenum—especially its duodenal stretch and pH (chemoreceptors).
- Response: Release of hormonal signals that inhibit gastric motility/secretion.
Small Intestine Anatomy
- Structure: Plicae circulares (circular ridges), Villi (finger-like projections), Microvilli (tiny projections on epithelial cells), located between the stomach and large intestine.
Three Regions of Small Intestine
-
Parts: Duodenum (first part-10 inches), Jejunum (middle part - 8 feet), Ileum (last part - 12 feet).
-
Duodenum: Chemical digestion (enzymes from pancreas, bile), Brunner's glands—alkaline mucus (neutralizes stomach acid).
-
Jejunum: Primary site of nutrient absorption.
-
Ileum: Major site of vitamin B12 absorption, returns bile salts to the liver.
-
Peyer's patches: MALT (mucosa-associated lymphatic tissue).
Small Intestine: Movement by Segmentation
- Mechanism: Ring-like contractions using circular muscle, mixes and propels chyme.
- Cycles: 9-12 cycles per minute; moves food completely through in 3-5 hours.
Small Intestine: Secretions
- Hormones: Enterogastrones (inhibit stomach secretions, motility).
- Examples: Cholecystokinin (CCK), Secretin, Gastric Inhibitory Polypeptide (GIP).
Small Intestine: Absorption
- Passive diffusion: Fatty acids and triglycerides (after micelles delivery), Vitamins.
- Active transport: H+ and Na+ actively transported by sodium-hydrogen antiporter. Water follow Na+
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Description
Test your knowledge of the human digestive system with this quiz. Covering topics from gastric emptying to nutrient absorption, this quiz assesses your understanding of key functions and structures involved in digestion. Perfect for students studying biology or health sciences!
