Podcast
Questions and Answers
Which function of the GI tract is primarily concerned with the immune system?
Which function of the GI tract is primarily concerned with the immune system?
In which species is the snout primarily used for prehension during feeding?
In which species is the snout primarily used for prehension during feeding?
What is the primary difference in mastication between carnivores and herbivores?
What is the primary difference in mastication between carnivores and herbivores?
What is one function of the motility movements in the GI tract?
What is one function of the motility movements in the GI tract?
Signup and view all the answers
What is the first motility pattern in the GI tract after feeding?
What is the first motility pattern in the GI tract after feeding?
Signup and view all the answers
What initiates the involuntary phase of deglutition?
What initiates the involuntary phase of deglutition?
Signup and view all the answers
Which structure prevents food from entering the trachea during swallowing?
Which structure prevents food from entering the trachea during swallowing?
Signup and view all the answers
Which type of dysphagia is associated with malfunction of the upper esophageal sphincter?
Which type of dysphagia is associated with malfunction of the upper esophageal sphincter?
Signup and view all the answers
Which molecule is known to inhibit hunger and increase energy consumption?
Which molecule is known to inhibit hunger and increase energy consumption?
Signup and view all the answers
What is the role of Cholecystokinin (CCK) in the regulation of food intake?
What is the role of Cholecystokinin (CCK) in the regulation of food intake?
Signup and view all the answers
During which stage of deglutition does breathing temporarily stop?
During which stage of deglutition does breathing temporarily stop?
Signup and view all the answers
Which area of the hypothalamus is primarily known as the hunger center?
Which area of the hypothalamus is primarily known as the hunger center?
Signup and view all the answers
What effect does Leptin have on Neuropeptide Y (NPY) release?
What effect does Leptin have on Neuropeptide Y (NPY) release?
Signup and view all the answers
Which mechanism is responsible for the stimulation of gastric acid secretion during the cephalic phase?
Which mechanism is responsible for the stimulation of gastric acid secretion during the cephalic phase?
Signup and view all the answers
What is the role of histamine in gastric acid secretion?
What is the role of histamine in gastric acid secretion?
Signup and view all the answers
Which species produces chymosine to aid in the digestion of milk proteins?
Which species produces chymosine to aid in the digestion of milk proteins?
Signup and view all the answers
During gastric motility, which phase is primarily induced by the presence of food in the duodenum?
During gastric motility, which phase is primarily induced by the presence of food in the duodenum?
Signup and view all the answers
What hormone is released primarily in response to fasting and is known to increase appetite?
What hormone is released primarily in response to fasting and is known to increase appetite?
Signup and view all the answers
Which of the following substances is primarily responsible for stimulating mucus secretion in the gastric mucosa?
Which of the following substances is primarily responsible for stimulating mucus secretion in the gastric mucosa?
Signup and view all the answers
Which of the following glands is primarily responsible for producing serous saliva?
Which of the following glands is primarily responsible for producing serous saliva?
Signup and view all the answers
Which type of secretion is characterized by a mixture of both mucous and serous fluids?
Which type of secretion is characterized by a mixture of both mucous and serous fluids?
Signup and view all the answers
Which function of saliva is directly related to the initiation of carbohydrate digestion?
Which function of saliva is directly related to the initiation of carbohydrate digestion?
Signup and view all the answers
Which component is added to saliva in the ducts, enhancing its regulatory function?
Which component is added to saliva in the ducts, enhancing its regulatory function?
Signup and view all the answers
In which species is saliva involved in thermoregulation primarily through behavior like panting?
In which species is saliva involved in thermoregulation primarily through behavior like panting?
Signup and view all the answers
What is a common consequence of disturbances in saliva production?
What is a common consequence of disturbances in saliva production?
Signup and view all the answers
What is the primary role of bicarbonate in salivary gland secretions?
What is the primary role of bicarbonate in salivary gland secretions?
Signup and view all the answers
What process is primarily involved in the production of carbonic acid within parietal cells?
What process is primarily involved in the production of carbonic acid within parietal cells?
Signup and view all the answers
Which component is actively transported into the canaliculus during HCl production?
Which component is actively transported into the canaliculus during HCl production?
Signup and view all the answers
Intrinsic factor is necessary for the absorption of which vitamin?
Intrinsic factor is necessary for the absorption of which vitamin?
Signup and view all the answers
What is the primary role of enteroendocrine cells in the gastrointestinal tract?
What is the primary role of enteroendocrine cells in the gastrointestinal tract?
Signup and view all the answers
What happens to H+/K+ ATPase when parietal cells are not stimulated?
What happens to H+/K+ ATPase when parietal cells are not stimulated?
Signup and view all the answers
Which hormone is secreted by enteroendocrine cells?
Which hormone is secreted by enteroendocrine cells?
Signup and view all the answers
What is the function of mucous neck cells in the gastric epithelium?
What is the function of mucous neck cells in the gastric epithelium?
Signup and view all the answers
Which of the following correctly describes the role of carbonic anhydrase?
Which of the following correctly describes the role of carbonic anhydrase?
Signup and view all the answers
When enteroendocrine cells release their secretions, where do they primarily release them?
When enteroendocrine cells release their secretions, where do they primarily release them?
Signup and view all the answers
Which type of channel is involved in the transport of Cl- into the canaliculus?
Which type of channel is involved in the transport of Cl- into the canaliculus?
Signup and view all the answers
Which statement accurately describes the role of gastric pits in the stomach?
Which statement accurately describes the role of gastric pits in the stomach?
Signup and view all the answers
What is the primary stimulus for the secretion of CCK (Cholecystokinin)?
What is the primary stimulus for the secretion of CCK (Cholecystokinin)?
Signup and view all the answers
In terms of gastric acid production, which animal has the highest daily production?
In terms of gastric acid production, which animal has the highest daily production?
Signup and view all the answers
Which hormone is responsible for stimulating bicarbonate secretion and inhibiting acid secretion in the stomach?
Which hormone is responsible for stimulating bicarbonate secretion and inhibiting acid secretion in the stomach?
Signup and view all the answers
What is the primary action of parasympathetic stimulation on salivary gland secretion?
What is the primary action of parasympathetic stimulation on salivary gland secretion?
Signup and view all the answers
Which type of secretion involves substances that act locally and diffuse through the interstitial space?
Which type of secretion involves substances that act locally and diffuse through the interstitial space?
Signup and view all the answers
Which of the following cell types is responsible for producing hydrochloric acid (HCl) in the gastric glands?
Which of the following cell types is responsible for producing hydrochloric acid (HCl) in the gastric glands?
Signup and view all the answers
The stimulation of saliva secretion purely through contact with the oral mucosa is categorized as which type of reflex?
The stimulation of saliva secretion purely through contact with the oral mucosa is categorized as which type of reflex?
Signup and view all the answers
Which hormone acts primarily to inhibit gastric secretion and stimulate insulin release in response to fats and glucose?
Which hormone acts primarily to inhibit gastric secretion and stimulate insulin release in response to fats and glucose?
Signup and view all the answers
In the context of GI tract motility, what role does acetylcholine play during fasting?
In the context of GI tract motility, what role does acetylcholine play during fasting?
Signup and view all the answers
What is the primary mechanism by which parietal cells produce gastric acid?
What is the primary mechanism by which parietal cells produce gastric acid?
Signup and view all the answers
Which hormone plays a crucial role in stimulating the secretion of gastric acid in the stomach?
Which hormone plays a crucial role in stimulating the secretion of gastric acid in the stomach?
Signup and view all the answers
How does the digestive system of herbivores typically differ from that of carnivores?
How does the digestive system of herbivores typically differ from that of carnivores?
Signup and view all the answers
Which of the following best describes the phases of motility movements in the GI tract during digestion?
Which of the following best describes the phases of motility movements in the GI tract during digestion?
Signup and view all the answers
What defines the role of enteroendocrine cells in the gastric mucosa?
What defines the role of enteroendocrine cells in the gastric mucosa?
Signup and view all the answers
Which factor primarily influences the composition of saliva produced by salivary glands?
Which factor primarily influences the composition of saliva produced by salivary glands?
Signup and view all the answers
Which aspect of gastric secretion is primarily regulated by the presence of food in the stomach?
Which aspect of gastric secretion is primarily regulated by the presence of food in the stomach?
Signup and view all the answers
What is the primary function of mucus secreted in the stomach?
What is the primary function of mucus secreted in the stomach?
Signup and view all the answers
In terms of energy source specialization, how do ruminants adapt their digestive systems?
In terms of energy source specialization, how do ruminants adapt their digestive systems?
Signup and view all the answers
What is primarily responsible for the reflection of satiety in the digestive system?
What is primarily responsible for the reflection of satiety in the digestive system?
Signup and view all the answers
Study Notes
GI Tract Function
- The GI tract is composed of concentric muscle cylinders lined with an epithelium, and functions in the transport, digestion, absorption of food.
- The GI tract also plays a role in water and electrolyte balance, provides an immunologic barrier through the Gut Associated Lymphoid Tissue (GALT), and regulates thermoregulation.
Prehension (Food Intake)
- Prehension involves the process of taking food into the mouth. Different species have different methods of feeding.
- Horses use their lips when eating from a manger or their incisors when grazing.
- Cattle use their tongue to wrap around forage and their incisors.
- Goats and sheep use their tongue and lips.
- Pigs use their snout and mandible.
- Carnivores utilize their canines, incisors, and forelimbs.
Mastication (Chewing)
- Mastication is the first step in digestion. It involves the teeth, jaws, tongue, and cheeks.
- Carnivores chew sparsely, with vertical movements of the mandible.
- Herbivores spend a significant amount of time masticating, with large upper and lower jaws that accommodate teeth with wide chewing surfaces.
GI Tract Motility
- After mastication, motility of different GI tract segments is activated.
-
Functions of GI tract movements:
- Propelling ingested feed from one location to the next.
- Retaining ingested feed at a specific site for digestion, absorption, or storage.
- Physically breaking up food material and mixing it with digestive secretions.
- Circulating ingested feed to ensure all portions come in contact with the absorptive surfaces.
Deglutition (Swallowing)
- Deglutition is the first motility pattern in the GI tract.
- Voluntary phase (oral phase): Food is molded into a bolus in the oral cavity and pushed back into the pharynx.
- Involuntary phase (swallow reflex): The pharynx and esophagus direct food into the digestive system, away from the upper airways.
Deglutition Mechanisms
- During deglutition, breathing momentarily stops.
- The soft palate elevates, blocking the pharyngeal opening of the nasopharynx.
- The tongue is pressed against the hard palate, closing off the oral opening.
- The epiglottis moves backwards, covering the entrance to the trachea.
- The upper esophageal sphincter opens, and food is transported through the esophagus by peristaltic contractions.
Deglutition Disorders
- Difficulty in swallowing (dysphagia) can result from neuromuscular disorders or mechanical obstruction.
- Oropharyngeal dysphagia arises from malfunctions in the pharynx and upper esophageal sphincter.
- Esophageal dysphagia is caused by malfunctions in the esophagus.
Aspiration
- Aspiration occurs when food particles, fluids, or stomach contents reach the upper airways.
- This can be a result of dysphagia.
Regulation of Food Intake
- The hypothalamus regulates energy homeostasis.
- Hunger center: Located in the paraventricular nucleus, lateral hypothalamus fields, and perifornical region.
- Satiety center: Located in the ventromedial nucleus.
Neuropeptides in the Hypothalamus
- Stimulatory: Neuropeptide Y (NPY) and Orexin.
- Inhibitory: Melanocyte-stimulating hormone (MSH) inhibits hunger and increases energy consumption.
Non-Hypothalamic Hormones
- Stimulatory: Ghrelin.
- Inhibitory: Cholecystokinin (CCK), Peptide YY (PYY), Leptin (secreted by fat cells, inhibits NPY release and activates MSH activity), and Insulin (secreted by the pancreas, regulated by glucose availability).
Ghrelin
- Produced in the stomach by endocrine cells in the gastric fundus
- Increases during fasting and decreases after eating (postprandially)
- Helps increase appetite and food intake
- Capromorelin is a ghrelin receptor agonist used to stimulate appetite in dogs
Salivary Glands
- Major salivary glands: Parotid, Mandibular, Sublingual
- Small salivary glands: Ventral jaw, Palate, Pharyngeal, Lip, Zygomatic
- Classified based on secretion type: Serous, Mucous, Seromucous
Saliva Functions
-
Primary (Digestive)
- Protects oral mucosa and teeth
- Facilitates swallowing (deglutition)
- Initiates carbohydrate digestion (via amylase)
- Regulates pH through bicarbonate (HCO3¯) secretion
-
Secondary
- Immunological (Lysozyme, Immunoglobulins)
- Thermoregulation (panting in dogs)
- Defense mechanism (llamas, alpacas, guanacos)
Saliva Composition
- Water (99%)
- Electrolytes (Na+, K+, Cl-, HCO3¯)
Salivary Gland Components
- Acini: Basic secretory unit of salivary glands; produces primary saliva (H2O, Cl-, Na+)
- Ducts: Add K+ and HCO3¯ to form secondary saliva
Saliva Production Disturbances
- Dry mouth (xerostomia)
- Buccal ulcers
- Dysphagia (difficulty swallowing)
- Increased bacterial growth, leading to dental caries
Saliva Secretion Regulation
-
Parasympathetic System:
- Nerves: Facial and Glossopharyngeal
- Act through M3 receptors
- Contracts myoepithelial cells
- Increases dilute saliva secretion
-
Sympathetic System:
- First three thoracic segments
- Act through alpha-1 receptors
- Secretes small volumes of viscous (mucous) saliva
Saliva Secretion Stimulation
- Innate (Reflex): Contact with oral mucosa (mechanoreceptors)
- Conditioned: Sight, smell, or imagination of food
Gastric Secretion Types
- Endocrine: Secretions enter blood and act on distant targets
- Paracrine: Local action through interstitial space, affecting nearby cells
- Autocrine: Acts on the same cell that produced it
- Neurocrine: Secretions from enteric neurons affecting muscle, glands, and blood cells
Digestive Hormones
-
Secreted by one cell and affect another
-
Transported in blood
-
Stimulated by food and mimicable by synthetic analogs
-
The "Big Five" GI Hormones:
Secretin
- Produced in duodenum (primarily) and jejunum
- Stimulates bicarbonate secretion
- Inhibits acid secretion
- Stimuli: Acids, fats, proteins
Gastrin
- Produced in stomach (antrum) and duodenum
- Stimulates acid secretion
- Stimuli: Protein, high pH
CCK (Cholecystokinin)
- Produced in duodenum, jejunum, and ileum
- Stimulates pancreatic enzyme secretion
- Stimulates gallbladder contraction
GIP (Glucose-dependent Insulinotropic Peptide)
- Produced in duodenum and jejunum
- Inhibits gastric secretion
- Stimulates insulin secretion
- Stimuli: Fats, glucose
Motilin
- Produced in duodenum and jejunum
- Induces intestinal motility during fasting (migrating motor complex - MMC)
- Stimuli: Acetylcholine
Monogastric Stomach
- Regions: Esophageal part, cardia, fundus, corpus, pylorus
-
Glandular Zones:
- Cardia: Mucus production dominant
- Fundus: HCl and enzyme production dominant
- Pylorus: Mucus production dominant
-
Gastric Acid Secretion: Varies by species
- Dogs: 0.2-0.5 liters/day
- Humans: 1.0-2.0 liters/day
- Pigs: 2.0-3.0 liters/day
- Horses: 6.0-8.0 liters/day
Monogastric Stomach Cells
- Surface Mucous Cells: Produce thick mucus to protect stomach from acid
- Gastric Pits: Lined with mucus-secreting cells, leads to gastric glands
-
Gastric Glands:
- Parietal cells: Produce HCl and intrinsic factor (IF)
- Chief cells: Produce pepsinogen (inactive), prochymosine (in calves and labs)
- Mucous Neck Cells: Produce thin mucus and serve as progenitor cells for gastric mucosa
- Enteroendocrine Cells: Produce hormones (gastrin, histamine, somatostatin)
- Stem Cells: Located in the neck of the gland, differentiate into various gastric pit cells
Gastric Acid Production in Parietal Cells
- Carbonic acid dissociates to produce protons (H+)
- H+/K+ ATPase pumps on the apical membrane actively pump 2H+ and Cl- into the lumen of the canaliculus
- Intrinsic factor (IF) is secreted by parietal cells and is essential for vitamin B12 absorption
Gastric Enzyme Secretion
- Stimulated by:
- Neural (acetylcholine, noradrenalin)
- Hormonal (secretin, CCK)
- Release of CCK and secretin from the small intestine is triggered by food particles and pH
- Amino acids and fatty acids stimulate CCK release
- Low pH stimulates secretin release
Gastric Secretion Regulation
-
Three Phases:
- Cephalic Phase: Before food enters the stomach (sight, smell, thought, taste)
- Gastric Phase: Induced by vagovagal reflexes and food in the stomach
- Intestinal Phase: Induced by food in the duodenum (feedback mechanism)
Gastric Ulcer
- Mucus secretion is less affected by food compared to acid and enzyme secretion
- Acetylcholine (Ach) and prostaglandin E (PGE) stimulate mucus secretion
- Non-steroidal anti-inflammatory drugs (NSAIDs) block prostaglandin synthesis, compromising mucus production and increasing ulcer risk
Learning Objectives
- Understand the functions of the GI tract
- Differentiate food and water intake between species
- Describe deglutition (swallowing) and its phases
- Explain the control of hunger and satiety
- Describe salivary gland structure and function
- Understand the composition and regulation of saliva production
- Compare endocrine, paracrine, neurocrine, and autocrine actions
- Describe the synthesis, function, and regulation of key digestive hormones (gastrin, GIP, secretin, CCK, motilin)
- Analyze the different parts of the monogastric stomach
- Identify cell types in the stomach and their functions
- Explain the production of gastric acid, enzymes, hormones, and mucus
- Understand the regulation of gastric secretion and enzyme production
- Explain the effects of NSAIDs on gastric mucosa
- Recognize causes of gastric ulcer in animals
Digestive System
- GI tract + Liver, pancreas, gallbladder (accessory organs)
- GI tract consists of a concentric muscle cylinder lined with epithelium
- Species have specialized digestive systems based on their diet
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the key functions of the GI tract, including digestion and absorption, as well as its role in maintaining homeostasis. Learn about various prehension methods used by different animal species during food intake and the importance of mastication in the digestion process.
