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Questions and Answers
What is the primary purpose of the gastrointestinal system?
What is the primary purpose of the gastrointestinal system?
To break down food and absorb nutrients needed for an animal's survival.
What type of stomach do most species have?
What type of stomach do most species have?
Ruminants have a simple stomach.
Ruminants have a simple stomach.
False
What is the role of goblet cells in the stomach?
What is the role of goblet cells in the stomach?
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What initiates chemical digestion in herbivores and omnivores?
What initiates chemical digestion in herbivores and omnivores?
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Where does chemical digestion occur in animals with a simple stomach?
Where does chemical digestion occur in animals with a simple stomach?
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The first part of the large intestine is called the ______.
The first part of the large intestine is called the ______.
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The main function of the large intestine is nutrient absorption.
The main function of the large intestine is nutrient absorption.
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What process is triggered by the presence of fat in the duodenum?
What process is triggered by the presence of fat in the duodenum?
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Match the following parts of the gastrointestinal system with their functions.
Match the following parts of the gastrointestinal system with their functions.
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Study Notes
Gastrointestinal System Overview
- The gastrointestinal (GI) system starts at the mouth and ends at the anus.
- Its primary roles are breaking down food (digestion) and absorbing essential nutrients.
- Most animals have a simple stomach with a single outpouching.
- The simple stomach is lined with mucosa containing goblet cells that secrete mucus for protection.
Complex Stomachs
- Ruminants and camelids have a complex stomach with four chambers: rumen, reticulum, omasum, and abomasum.
- These chambers are designed to break down complex carbohydrates through bacterial fermentation.
- The rumen, reticulum, and omasum are the "orad" chambers.
- The abomasum functions like the simple stomach in other species.
- Equine stomachs are unique, with the orad portion covered in squamous mucosa and the aboral portion covered in glandular mucosa.
Digestion
- Digestion occurs through mechanical and chemical processes.
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Mechanical digestion:
- Starts in the oral cavity with mastication (chewing).
- Molars grind food into smaller pieces.
- The tongue mixes food with saliva.
- Herbivores and omnivores secrete amylase in saliva, initiating carbohydrate digestion.
- Carnivores do not secrete amylase and chew their food less.
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Chemical digestion:
- Occurs in the stomach for all species.
- In animals with a simple stomach, parietal cells secrete hydrochloric acid, breaking down proteins into smaller units.
- In ruminants, carbohydrates are circulated through the rumen and reticulum for fermentation by bacteria.
- Ingesta is regurgitated and chewed again for continued mechanical digestion and fermentation.
- After fermentation, ingesta moves to the abomasum for protein digestion by hydrochloric acid.
Digestion in the Small Intestine
- After the stomach, food (now called chyme) enters the duodenum.
- The presence of food triggers the release of pancreatic enzymes (amylase and lipase) from the pancreas.
- Fats in the duodenum stimulate gall bladder contraction, releasing bile into the duodenum.
- Bile breaks down larger fat pieces into smaller lipid droplets.
- Amylase continues carbohydrate digestion.
- Lipase breaks down fat droplets into fatty acids for absorption.
- By the jejunum, all major food components are fully digested.
Absorption and the Large Intestine
- The jejunum is the main site for nutrient absorption.
- Jejunal mucosa folds into villi, and cell membranes are folded into microvilli, increasing surface area for absorption.
- After the jejunum, the chyme moves into the ileum, connecting the small intestine to the large intestine.
- The cecum is an outpouching at the junction of the small and large intestines.
- In most animals, the cecum is simply for water absorption.
- In equids, the cecum is responsible for carbohydrate fermentation.
- The large intestine includes the ascending, transverse, descending colon, and rectum.
- The large intestine's primary roles are water absorption, storage of fecal matter, and bicarbonate secretion for acid-base balance.
- In equids, the large intestine works with the cecum for complex carbohydrate digestion.
Defecation
- Once feces accumulates, defecation is triggered, and feces pass through the anal sphincter.
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Description
Explore the fascinating structure and function of the gastrointestinal system, including the differences between simple and complex stomachs. Learn about the roles of various stomach chambers in digestion and nutrient absorption across different animal species.
