The Digestive System Overview

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Questions and Answers

What is the primary function of saliva in the oral cavity?

  • To absorb nutrients from food
  • To initiate protein digestion
  • To lubricate food and begin carbohydrate digestion (correct)
  • To protect the mouth from infection

Which part of the gastrointestinal tract is responsible for most chemical digestion?

  • Oesophagus
  • Duodenum (correct)
  • Jejunum
  • Ileum

What process helps move food down the oesophagus?

  • Mastication
  • Absorption
  • Segmentation
  • Peristalsis (correct)

Which type of cell in the small intestine is primarily responsible for nutrient absorption?

<p>Enterocytes (B)</p> Signup and view all the answers

Which statement about the pharynx is correct?

<p>It directs air to the larynx and food to the oesophagus. (D)</p> Signup and view all the answers

What is the final section of the small intestine called?

<p>Ileum (B)</p> Signup and view all the answers

How does the small intestine protect itself from infection?

<p>By secreting antimicrobial peptides (C)</p> Signup and view all the answers

Which function does the oesophagus NOT perform?

<p>Aid in absorption of nutrients (D)</p> Signup and view all the answers

What is the primary function of the large intestine?

<p>Absorb water and electrolytes (B)</p> Signup and view all the answers

Which type of cell in the large intestine is responsible for reabsorbing water and electrolytes?

<p>Colonocytes (C)</p> Signup and view all the answers

Which of the following hormones do enteroendocrine cells release?

<p>Digestive hormones (C)</p> Signup and view all the answers

What does the pancreas do in the digestive process?

<p>Secretes digestive enzymes into the duodenum (C)</p> Signup and view all the answers

How is bile released into the duodenum?

<p>Due to the presence of fats in the chyme (B)</p> Signup and view all the answers

What primarily occurs during carbohydrate absorption in the small intestine?

<p>Monosaccharides are absorbed directly into the bloodstream (B)</p> Signup and view all the answers

What is the role of goblet cells in the large intestine?

<p>Secrete mucus for lubrication (D)</p> Signup and view all the answers

What happens to fatty acids in the small intestine after absorption?

<p>They are reassembled into triglycerides and packaged into chylomicrons (C)</p> Signup and view all the answers

What is the primary function of leptin in the body?

<p>Signals the brain to reduce appetite and increase energy expenditure (D)</p> Signup and view all the answers

Which vitamins are classified as fat-soluble vitamins?

<p>A, D, E, and K (D)</p> Signup and view all the answers

What triggers the gastric phase of digestion?

<p>The entry of food into the stomach (B)</p> Signup and view all the answers

What does Basal Metabolic Rate (BMR) represent?

<p>Minimum energy required for basic physiological functions (B)</p> Signup and view all the answers

Which hormone is released in response to acidic chyme entering the small intestine?

<p>Secretin (C)</p> Signup and view all the answers

Which of the following accurately defines a calorie?

<p>A unit of energy that represents food energy (D)</p> Signup and view all the answers

What role does cholecystokinin (CCK) play in digestion?

<p>Stimulates the release of bile and pancreatic enzymes (D)</p> Signup and view all the answers

Which phase of digestion is characterized by the brain signaling the stomach to produce gastric juices?

<p>Cephalic Phase (A)</p> Signup and view all the answers

How is Body Mass Index (BMI) calculated?

<p>Weight in kilograms divided by height in meters squared (C)</p> Signup and view all the answers

What is the main function of gastrin in the digestive process?

<p>To promote gastric acid production (A)</p> Signup and view all the answers

Which BMI classification indicates a person is considered obese?

<p>BMI of 30 and above (B)</p> Signup and view all the answers

Which statement about calories in the body is correct?

<p>Calories are required for basic functions like breathing. (C)</p> Signup and view all the answers

How are minerals absorbed in the digestive system?

<p>Through both active and passive transport mechanisms (B)</p> Signup and view all the answers

What happens to BMR as a person ages?

<p>BMR generally decreases as a person ages. (D)</p> Signup and view all the answers

Which of the following methods can be used to increase BMR?

<p>Increasing muscle mass through resistance training (C)</p> Signup and view all the answers

What physiological functions does BMR support?

<p>All activities including digestive processing and immune function (A)</p> Signup and view all the answers

Flashcards

Digestion

The process of breaking down food into smaller molecules that can be absorbed by the body.

Peristalsis

The mechanism by which food is moved through the digestive tract.

Duodenum

The first part of the small intestine where most chemical digestion occurs.

Jejunum

The middle section of the small intestine primarily involved in nutrient absorption.

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Ileum

The final section of the small intestine, responsible for absorbing remaining nutrients and bile acids.

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Enterocytes

Cells lining the small intestine responsible for absorbing nutrients.

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Goblet Cells

Specialized cells in the small intestine that produce mucus to protect the intestinal lining.

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Paneth Cells

Cells located at the base of intestinal crypts that secrete antimicrobial peptides to defend against infections.

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Colonocytes

Specialized cells in the large intestine that absorb water and electrolytes from the remaining indigestible food matter.

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Large Intestine Function

The primary function of the large intestine is to absorb water and electrolytes from the remaining indigestible food matter and form and store feces until defecation.

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Pancreas Function

The pancreas has both endocrine and exocrine functions, producing digestive enzymes (amylase, lipase, proteases) for digestion and bicarbonate to neutralize stomach acid in the duodenum.

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Bile Function

Bile is produced by the liver and stored in the gallbladder, released into the duodenum to aid in the digestion and absorption of fats.

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Carbohydrate Absorption

Simple sugars (monosaccharides) are absorbed directly into the bloodstream through the enterocytes in the small intestine.

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Protein Absorption

Amino acids and small peptides are absorbed into the bloodstream via active transport mechanisms in the enterocytes.

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Fat Absorption

Fatty acids and monoglycerides are absorbed into the enterocytes, reassembled into triglycerides, packaged into chylomicrons, and transported into the lymphatic system before entering the bloodstream.

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Fat-Soluble Vitamins

Vitamins A, D, E, and K are absorbed with dietary fats in the small intestine. They are stored in the body for longer periods.

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Water-Soluble Vitamins

Vitamins B and C are absorbed directly into the bloodstream. They are not stored in the body for long and need to be replenished regularly.

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Minerals

Minerals, such as calcium, iron, and zinc, are absorbed through various mechanisms depending on the mineral. They are essential for many bodily functions.

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Cephalic Phase of Digestion

The cephalic phase is initiated by sensory cues (sight, smell, taste, thought) and prepares the digestive system for food intake.

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Gastric Phase of Digestion

The gastric phase begins when food enters the stomach and involves the secretion of gastric juices (including hydrochloric acid and pepsin) to break down food.

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Intestinal Phase of Digestion

The intestinal phase begins when chyme (partially digested food) enters the small intestine. It involves hormone release to regulate digestion and nutrient absorption.

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Leptin

Leptin signals the brain to decrease appetite and increase energy expenditure, helping to regulate body weight. It is produced by adipose tissue.

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Ghrelin

Ghrelin stimulates appetite by signaling the brain when the stomach is empty. It is primarily produced by the stomach.

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What is Basal Metabolic Rate (BMR)?

The minimum amount of energy required to maintain basic life functions when at rest in a neutral environment.

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What is a calorie?

A unit of energy. Calories in nutrition represent the amount of energy provided by food and drinks.

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What is Body Mass Index (BMI)?

A measure of body fat based on height and weight that applies to adult men and women. Calculated by dividing weight in kilograms by the square of height in meters (kg/m²).

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What is a healthy body mass index (BMI)?

A normal BMI falls between 18.5 and 24.9.

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Define underweight BMI.

A BMI under 18.5 indicates a person is underweight.

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Define overweight BMI.

A BMI between 25 and 29.9 indicates a person is overweight.

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Define obese BMI.

A BMI of 30 or above indicates a person is obese.

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What is digestion?

The process of breaking down food into smaller molecules that the body can absorb and use.

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Study Notes

The Digestive System

  • The digestive system breaks down food, absorbs nutrients, and eliminates waste.
  • The gastrointestinal (GI) tract is a continuous tube, extending from the mouth to the anus.

Components of the GI Tract

  • Oral Cavity (Mouth):

    • Mechanical digestion begins with chewing (mastication).
    • Chemical digestion starts with saliva (containing amylase to break down starch).
    • Saliva lubricates food, aiding in digestion.
  • Pharynx:

    • Pathway for food from the mouth to the oesophagus.
    • Plays a role in respiration, directing air to the larynx.
  • Oesophagus:

    • Connects the pharynx to the stomach.
    • Peristalsis (coordinated muscle contractions) moves food to the stomach.
  • Peristalsis:

    • Rhythmic contractions of smooth muscles in the GI tract.
    • Propels food through the digestive system.
  • Small Intestine:

    • Divided into three parts: duodenum, jejunum, and ileum.
    • Duodenum: Main site for chemical digestion, receiving bile and enzymes.
    • Jejunum: Absorbs nutrients.
    • Ileum: Absorbs remaining nutrients and bile acids.
  • Differentiated Cells: various specialized cells in the intestines have specific functions (e.g., Enterocytes absorb nutrients).

Accessory Organs of Digestion

  • Pancreas:

    • Produces digestive enzymes (amylase, lipase, and proteases), aiding in digestion of carbs, fats, and proteins.
    • Secretes bicarbonate to neutralize stomach acid.
  • Liver:

    • Produces bile, essential for fat emulsification and digestion.
    • Plays a vital role in metabolism, detoxification, and nutrient storage.
  • Gallbladder:

    • Stores bile produced by the liver.
    • Releases bile into the duodenum in response to fats in food.

The Process of Absorption

  • Absorption mainly occurs in the small intestine.
    • Nutrients pass through the intestinal wall into the bloodstream or lymphatic system.
  • Carbohydrate Absorption: Simple sugars are absorbed directly into the bloodstream.
  • Protein Absorption: Amino acids and small peptides are absorbed via active transport.
  • Fat Absorption: Fatty acids and monoglycerides are absorbed, reassembled into triglycerides, and transported to the lymphatic system.
  • Vitamins and Minerals: Fat-soluble (A, D, E, K) absorbed with fats; water-soluble (B, C) and minerals absorbed through different mechanisms.

Phases of Digestion

  • Cephalic Phase: Digestive system preparation triggered by sight, smell, taste of food, stimulating gastric juice production and salivation.
  • Gastric Phase: Initiated by food entering the stomach, with stomach expansion stimulating gastric juices to further digest proteins and fats.
  • Intestinal Phase: Chyme entering the small intestine triggers hormones that slow gastric emptying further stimulating digestive enzyme and bile release.

Hormones Involved in Digestion

  • Leptin: Regulates appetite and energy expenditure.
  • Ghrelin: Stimulates appetite.
  • Gastrin: Promotes gastric acid production.
  • Secretin: Neutralizes stomach acid and stimulates bicarbonate release.
  • Cholecystokinin (CCK): Stimulates release of bile and pancreatic enzymes.

Basal Metabolic Rate (BMR) and Body Mass Index (BMI)

  • BMR: Energy expenditure at rest.
  • BMI: Measure of body fat based on height and weight (kg/m²).

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