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Questions and Answers
What is the primary function of the gastrointestinal tract?
What is the primary function of the gastrointestinal tract?
Which process refers to the physical breakdown of food into smaller pieces?
Which process refers to the physical breakdown of food into smaller pieces?
How does chemical digestion primarily occur?
How does chemical digestion primarily occur?
Which of the following is NOT a part of the gastrointestinal tract?
Which of the following is NOT a part of the gastrointestinal tract?
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In what organ does the majority of absorption occur?
In what organ does the majority of absorption occur?
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What type of gastrointestinal system does a cow possess?
What type of gastrointestinal system does a cow possess?
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In which part of the gastrointestinal system does the absorption of nutrients primarily occur for dogs?
In which part of the gastrointestinal system does the absorption of nutrients primarily occur for dogs?
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Which of the following correctly describes hindgut fermenters?
Which of the following correctly describes hindgut fermenters?
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What is a key characteristic of herbivores' dietary habits?
What is a key characteristic of herbivores' dietary habits?
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What distinguishes monogastric animals from ruminants?
What distinguishes monogastric animals from ruminants?
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What is the primary function of mastication in the oral cavity?
What is the primary function of mastication in the oral cavity?
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Which teeth are primarily responsible for the grinding motion in herbivores?
Which teeth are primarily responsible for the grinding motion in herbivores?
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Which of the following functions does the tongue NOT perform?
Which of the following functions does the tongue NOT perform?
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What is the primary role of saliva in the digestive process?
What is the primary role of saliva in the digestive process?
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Which salivary gland is located beside the ear?
Which salivary gland is located beside the ear?
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What distinguishes a carnivore's teeth from those of an omnivore?
What distinguishes a carnivore's teeth from those of an omnivore?
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What term describes the rhythmic contraction that moves food through the esophagus?
What term describes the rhythmic contraction that moves food through the esophagus?
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Which of the following is NOT a function of the tongue?
Which of the following is NOT a function of the tongue?
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What is the primary function of hydrochloric acid in the stomach?
What is the primary function of hydrochloric acid in the stomach?
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Which process primarily occurs in the large intestine of hindgut fermenters?
Which process primarily occurs in the large intestine of hindgut fermenters?
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What is the role of mucus secretion in the stomach?
What is the role of mucus secretion in the stomach?
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What structural feature of the stomach assists in its mechanical digestion?
What structural feature of the stomach assists in its mechanical digestion?
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Which of the following is NOT a function of the stomach?
Which of the following is NOT a function of the stomach?
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Why is the process of 'chewing the cud' important for ruminants?
Why is the process of 'chewing the cud' important for ruminants?
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What is the primary characteristic of a hindgut fermenter’s stomach compared to ruminants?
What is the primary characteristic of a hindgut fermenter’s stomach compared to ruminants?
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Which statement accurately describes the function of the segmental contractions in the stomach?
Which statement accurately describes the function of the segmental contractions in the stomach?
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What is the main purpose of mechanical digestion?
What is the main purpose of mechanical digestion?
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What is the end product of protein digestion?
What is the end product of protein digestion?
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Which type of digestive system is characterized by consumption of both plant and animal material?
Which type of digestive system is characterized by consumption of both plant and animal material?
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Which process follows digestion and allows absorption of nutrients into the bloodstream?
Which process follows digestion and allows absorption of nutrients into the bloodstream?
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What is the function of defecation in the gastrointestinal system?
What is the function of defecation in the gastrointestinal system?
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Which of the following best describes chemical digestion?
Which of the following best describes chemical digestion?
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Which type of gastrointestinal system consumes only animal material?
Which type of gastrointestinal system consumes only animal material?
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What are the building blocks of fats after digestion?
What are the building blocks of fats after digestion?
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Study Notes
Gastrointestinal Tract Overview
- The gastrointestinal tract is a continuous tube running from the mouth to the anus.
- It is divided into three main sections based on function: stomach, small intestine, and large intestine.
- The GIT functions in digestion, absorption of nutrients and water, and expulsion of waste materials.
Mechanical and Chemical Digestion
- Digestion is the process of breaking down complex nutrients into simple molecules.
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Mechanical digestion involves physically reducing the size of food.
- This increases the surface area available to digestive enzymes.
- Processes include mastication (chewing) and stomach mixing.
- Chemical digestion involves splitting apart chemical bonds between food particles using enzymes.
Ingesta
- Food consists of carbohydrates, proteins, fats, water, minerals, and vitamins.
- Complex molecules are broken down during digestion into their building blocks:
- Proteins are broken down into amino acids.
- Carbohydrates are broken down into simple sugars (glucose, fructose).
- Fats are broken down into triglycerides and fatty acid chains.
Types of Gastrointestinal Systems
- There are two ways to classify an animal's gastrointestinal system: by food type and by anatomy.
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By food type:
- Omnivores: Consume plant and animal material.
- Carnivores: Consume animal material (meat).
- Herbivores: Consume plant material.
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By anatomy:
- Monogastric: Have a simple (single-chambered) stomach.
- Ruminant/Foregut Fermenter: Have a multi-chambered stomach (rumen).
- Hindgut Fermenter: Have a simple stomach with primary digestion occurring in the large intestine.
Gastrointestinal Systems Across Species
- Pig, Rat, Human - Omnivores/Monogastric
- Cat, Dog - Carnivores/Monogastric
- Sheep, Cow, Giraffe, Buffalo - Herbivores/Ruminant
- Rabbit, Horse, Elephant, Hippo, Rhino - Herbivores/Hindgut Fermenter
The Oral Cavity
- The oral cavity is where food intake occurs.
- Some animals have prehensile lips and tongues, such as cows, horses, and sheep.
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Mastication (chewing) is the mechanical breakdown of food.
- This increases the surface area for chemical digestion.
- Saliva mixes with the food and sometimes contains digestive enzymes.
The Tongue
- Functions include ingestion of food, taste, forming a food bolus for swallowing, grooming (especially cats), and thermoregulation.
Teeth
- Incisors: Small teeth at the front.
- Canines: Large single-root teeth.
- Premolars: Multi-root teeth, majority of cheek teeth, variable size and shape.
- Molars: Single and multi-root teeth, caudal most teeth, flatter surface.
- Teeth function in mechanically breaking down food particles to increase surface area for digestive enzymes.
Salivary Glands
- Saliva lubricates food to aid swallowing and contains antibacterial enzymes.
- Omnivores have mild digestive enzymes in their saliva, but carnivores do not.
- Salivary gland anatomy is similar across species, but saliva composition differs based on diet.
- Glands include parotid, mandibular, and sublingual.
Oesophagus
- A muscular tube that transports food from the mouth to the stomach.
- Runs from the oropharynx, down the neck, through the thorax, and through the diaphragm into the abdomen.
- Upper and lower oesophageal sphincters regulate food entry into the stomach.
Movement of Food Through the Oesophagus
- Peristalsis, rhythmic contractions of longitudinal muscles, propels food along the GIT.
Stomach in Monogastric & Hindgut Fermenters (Simple Stomach)
- Located caudally to the liver.
- Functions in storage, chemical digestion with enzymes, and mechanical mixing with muscular contractions.
Chemical Digestion in the Stomach
- Hydrochloric acid (HCl) is secreted, creating an acidic environment that:
- Kills microbes.
- Denatures (unfolds) proteins for easier digestion.
- Mucus secretion protects the gastric mucosa from the acidic environment.
Mechanical Digestion in the Stomach
- The stomach lining (gastric mucosa) contains muscular layers that produce rhythmic segmental contractions for mixing digesta with digestive enzymes.
- Rugae are folds in the mucosa that increase surface area.
Ruminant Stomach (Interest Only)
- Cellulose, the primary component of plant material, is undigestible by mammals.
- Bacteria in the rumen break down cellulose into volatile fatty acids, which ruminants use for energy.
- "Chewing the cud" involves regurgitating digesta to allow further chewing and increase surface area for bacterial contact and digestion.
- The ruminant stomach consists of four chambers: rumen, reticulum, omasum, and abomasum.
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