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Questions and Answers
What is the primary function of the gallbladder?
What is the primary function of the gallbladder?
The primary function of the large intestine is to absorb nutrients from food.
The primary function of the large intestine is to absorb nutrients from food.
False
What are villi and why are they important in the digestive system?
What are villi and why are they important in the digestive system?
Villi are small finger-like projections in the small intestine that increase surface area for absorption.
The small vessels that transport fat to the circulatory system are called __________.
The small vessels that transport fat to the circulatory system are called __________.
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Match the parts of the large intestine with their functions:
Match the parts of the large intestine with their functions:
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What is the primary function of the esophagus in the digestive system?
What is the primary function of the esophagus in the digestive system?
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The jejunum is primarily responsible for the majority of digestion.
The jejunum is primarily responsible for the majority of digestion.
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What enzyme breaks down starch into glucose?
What enzyme breaks down starch into glucose?
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The organ that produces bile for digestion of fats is the ______.
The organ that produces bile for digestion of fats is the ______.
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Match the following digestive organs with their primary function:
Match the following digestive organs with their primary function:
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What is the primary role of mucus in the stomach?
What is the primary role of mucus in the stomach?
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Proteins are absorbed in their unaltered polypeptide form.
Proteins are absorbed in their unaltered polypeptide form.
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What are the four main processes of digestion?
What are the four main processes of digestion?
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The process of breaking food down into smaller pieces using teeth is called ______.
The process of breaking food down into smaller pieces using teeth is called ______.
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Which enzyme is responsible for digesting proteins?
Which enzyme is responsible for digesting proteins?
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The pyloric sphincter regulates the entry of food from the esophagus into the stomach.
The pyloric sphincter regulates the entry of food from the esophagus into the stomach.
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What are the three types of digestive enzymes mentioned?
What are the three types of digestive enzymes mentioned?
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Nutrients are absorbed into the bloodstream through the ______.
Nutrients are absorbed into the bloodstream through the ______.
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Which of the following is a type of mechanical digestion?
Which of the following is a type of mechanical digestion?
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Study Notes
Digestive System Overview
- Digestive system: Organs working together to process food, extract nutrients, and eliminate waste. Organ systems often depend on each other for function.
- Heterotrophs consume other organisms for energy and raw materials (organic compounds like carbohydrates, fats, proteins, minerals, and vitamins).
- Nutrients support body growth, maintenance, and repair.
Types of Digestion
- Physical/Mechanical Digestion: This involves breaking food into smaller pieces. Examples include chewing (mastication) and stomach contractions.
- Chemical Digestion: Enzymes and water break down food for absorption.
Four Main Processes
- Ingestion: Taking food into the body.
- Digestion: Breakdown of food.
- Absorption: Taking nutrients from digested food into the bloodstream.
- Egestion/Elimination: Removing undigested materials from the body.
Ingestion: Mouth, Pharynx, and Esophagus
- Mouth (Teeth): Incisors cut, canines tear, premolars and molars grind food.
- Mouth (Tongue): Taste buds, strong musculature aids in swallowing. Saliva, containing amylase (breaks down complex carbs), lubricates food and dissolves food particles.
- Pharynx: Passageway for air and food; contains gag/swallowing reflexes.
- Epiglottis: Prevents food from entering the trachea (windpipe).
- Esophagus: Peristalsis (wave-like contractions) moves food through.
Digestion: Stomach
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Stomach: J-shaped organ storing and digesting food. Lined with cells producing:
- Mucous cells: Protective mucus and bicarbonate ions (HCO₃−).
- Parietal cells: Hydrochloric acid (HCl).
- Peptic cells: Pepsinogen (turns into pepsin, a protein-digesting enzyme).
- Sphincters: Regulate food movement in/out of the stomach (esophageal/cardiac and pyloric).
- Gastric juice: HCl, mucus, pepsinogen, other components. Pepsinogen is activated at low pH (1–3).
- Chyme: Partially digested food mixture produced in the stomach. Acid reflux occurs when stomach contents return to the esophagus.
- Mucus: A protective layer produced by epithelial cells, alkaline in nature, protecting the stomach lining against HCl and pepsin. Damage to the mucus layer leads to ulcers.
Absorption: Small Intestine
- Small Intestine (Structure): Long, folded tube with three sections (duodenum, jejunum, ileum); high surface area for absorption.
- Small Intestine (Digestion): Duodenum is the primary site of digestion; jejunum absorbs proteins/carbohydrates; ileum absorbs remaining nutrients.
- Pancreatic Hormones: Prosecretin (inactive) converts to secretin (activated by acidic chyme entering the small intestine) which signals pancreas to release bicarbonate (HCO₃−) to neutralize acids (adjusting pH to 2.5–8, inactivating pepsin).
- Pancreatic Enzymes: Amylases (carbs), proteases (trypsin, erepsins – proteins), lipases (fats).
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Nutrient Breakdown:
- Carbohydrates: Amylase breaks down complex carbs into simple sugars (absorbed as monosaccharides into capillaries of villi).
- Fats: Bile (produced by liver, stored in gallbladder) physically breaks down fats into smaller droplets. Lipase (produced by pancreas) chemically digests fats. Absorption into lacteals(small vessels carrying fats to the circulatory system).
- Proteins: Enzymes (e.g., trypsin) break down proteins into amino acids (absorbed into capillaries of villi).
Accessory Organs
- Liver: Produces bile; removes/stores excess sugar; detoxifies blood; recycles old red blood cells.
- Gallbladder: Stores bile, releases it into the small intestine when needed. -Villi: finger-like projections on the small intestine wall increasing surface area for absorption. -Microvillli: microscopic projections on the surface of cells in the small intestine wall increasing the surface area for absorption. -Lacteals: small vessels that absorb fats.
Large Intestine
- Large Intestine: Wider and shorter than small intestine; four sections (cecum, colon, rectum, anus) stores waste, absorbs water, some inorganic salts, vitamins, and minerals.
- Bacteria: Anaerobic bacteria synthesize vitamin K and some B vitamins.
Elimination
- Rectum: Stores waste.
- Anus: Controls waste discharge (feces).
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