Digestive System Study Notes
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Questions and Answers

What are the two main groups of organs that compose the digestive system?

  • Gastrointestinal (GI) tract and the oral cavity
  • Alimentary canal and the accessory digestive organs
  • Gastrointestinal (GI) tract and accessory digestive organs (correct)
  • Esophagus and the accessory digestive organs

    • Which of the following is NOT part of the gastrointestinal (GI) tract?

  • Stomach
  • Pharynx
  • Pancreas (correct)
  • Mouth

    • What is the approximate length of the gastrointestinal (GI) tract?

  • 12m
  • 3m
  • 6m
  • 9m (correct)

    • Which of the following is NOT an accessory digestive organ?

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

    What are the two types of digestion?

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

    What does NOT fall under the definition of mechanical digestion?

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

    What is peristalsis?

    <p>A wave of coordinated muscle contractions that moves food through the GI tract.</p> Signup and view all the answers

    What is the primary chemical process involved in chemical digestion?

    <p>Hydrolysis</p> Signup and view all the answers

    What are fats broken down to by chemical digestion?

    <p>Fatty acids and glycerol (B)</p> Signup and view all the answers

    Flashcards

    Name the 2 groups of organs that compose the digestive system

    1. Gastrointestinal (GI) tract or alimentary canal
    2. Accessory digestive organs

    What makes up the Gastrointestinal (GI) tract?

    Is a continuous tube that extends from mouth to anus Includes: most of pharynx, esophagus, stomach, small intestine, and large intestine GI tract is approximately 9m long

    What makes up the Accessory Digestive Organs?

    Includes: teeth, tongue, salivary glands, liver, gallbladder, and pancreas These organs NEVER come in direct contact with food (with the exception of teeth and tongue!) These organs produce or store secretions that flow into GI tract through ducts

    Is the mouth a part of the GI tract or an Accessory organ?

    Accessory

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    What are the two types of digestion?

    1. Mechanical
    2. Chemical
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    Define Mechanical Digestion:

    ❑ Mastication ❑ Swallowing ❑ Mixing ❑ Peristalsis

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    Define Peristalsis:

    a progression of coordinated contractions & relaxations of circular & longitudinal layers of muscularis which pushes bolus forward

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    Define Chemical Digestion:

    Enzymes secreted by accessory organs and cells that line the tract break down the food chemically

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    Chemical digestion is mainly accomplished by using what?

    Water to break down chemical bonds (Hydrolysis)

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    What are Fats, Carbs & Proteins broken down to by chemical digestion?

    Fats = Fatty Acids/ Glycerol Carbs = Monosaccharides Proteins = Amino Acids

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    What is Glycerol?

    Backbone of the fatty acid chain

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    What are the 6 functions of the digestive system?

    1. Ingestion: take in food/water
    2. Secretion: of water, acid, buffers, and enzymes into lumen
    3. Mixing and propulsion* (Peristalsis)
    4. Digestion* (Mechanical & Chemical)
    5. Absorption* - passing of fluids, ions, and products of digestion into the epithelial cells lining the lumen
    6. Defecation*
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    What are the 4 layers of the GI tract starting from the most superficial to the lumen?

    1. Mucosa
    2. Submucosa:
    3. Muscularis
    4. Serosa
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    Most superficial (to lumen) layer of GI tract

    Mucosa

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    What are the 3 layers of the Mucosa?

    1. Epithelium
    2. Lamina Propria
    3. Muscularis Mucosae
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    Layer of Mucosa, most superficial Serves as protection

    Epithelium

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    Middle layer of Mucosal layer Areolar CT Blood, Lymphatic vessels & MALT located here

    Lamina Propria

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    Deepest layer of Mucosal layer Thin layer of smooth mm increase surface area specifically in the stomach and the small intestine

    Muscularis Mucosae

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    What layer of the GI has the MALT?

    Lamina Propria of the Mucosa

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    2nd layer of GI tract Connective tissue binding mucosa to muscularis Contains many blood and lymphatic vessels that receive absorbed food molecules Has a network of neurons called submucosal plexus

    Submucosa

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    3rd layer of GI tract Voluntary skeletal muscle found in mouth, pharynx, upper 2/3 of esophagus, and anal sphincter (start & end) Remaining GI smooth mm Arranged in inner circular fibers & outer longitudinal fibers (except for stomach = 3 layers) Peristalsis break down food, mix with digestive secretions & propel along tract Myenteric plexus between muscle layers

    Muscularis

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    Which type of smooth muscle (circular or longitudinal) is superficial and deep in the Muscularis layer of the GI Tract?

    Superficial = Circular Deep = Longitudinal

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    Deepest layer of GI tract Outermost covering of organs suspended in abdominopelvic cavity Also called visceral peritoneum

    Serosa

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    What part of the GI tract does not have serosa?

    Esophagus -has a layer of CT called adventitia

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    Why is it called "Serosa"?

    Secretes Serous fluid to decrease friction Found in Heart, Lungs & GI

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    How is the GI tract innervated?

    1. Enteric nervous system (ENS)
    2. Autonomic nervous system (ANS)
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    Enteric nervous system (ENS)

    "brain of gut", solely responsible for GI function Neurons extending from esophagus to anus 2 plexuses

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    Autonomic Nervous system

    portion of the nervous system that act on the GI from an Extrinsic set of nerves Has parasympathetic & sympathetic action stimulation

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    Study Notes

    Digestive System 1 Study Notes

    • Two groups of organs compose the digestive system:

      • Gastrointestinal (GI) tract (alimentary canal): continuous tube from mouth to anus, approximately 9 meters long; includes pharynx, esophagus, stomach, small intestine, and large intestine
      • Accessory digestive organs: teeth, tongue, salivary glands, liver, gallbladder, and pancreas. These organs never directly touch food (except teeth and tongue); they produce or store secretions that flow into the GI tract via ducts.

    • Digestion Types:

      • Mechanical digestion: processes that physically break down food; includes mastication (chewing), swallowing, mixing, and peristalsis (wave-like muscular contractions pushing food down).
      • Chemical digestion: enzymes secreted by accessory organs and cells in the digestive tract break down food chemically via hydrolysis (using water to break chemical bonds).

    • Digestion End Products:

      • Fats are broken down to fatty acids and glycerol.
      • Carbohydrates are broken down to monosaccharides.
      • Proteins are broken down to amino acids.

    • Functions of the Digestive System:

      • Ingestion: taking in food and water
      • Secretion: releasing water, acid, buffers, and enzymes into the digestive tract
      • Mixing and propulsion: moving food along the GI tract via peristalsis
      • Digestion: mechanical and chemical breakdown of food
      • Absorption: moving digested nutrients into the bloodstream
      • Defecation: eliminating waste products

    • Layers of the GI Tract (superficial to lumen):

      • Mucosa: innermost layer, with three sublayers:
        • Epithelium: protective outer layer
        • Lamina Propria: areolar connective tissue containing blood vessels, lymphatic vessels, and MALT (Mucosa-Associated Lymphoid Tissue).
        • Muscularis Mucosae: thin smooth muscle layer increasing surface area in stomach and small intestine.
      • Submucosa: connective tissue layer with blood and lymphatic vessels and submucosal plexus (network of neurons)
      • Muscularis: smooth muscle layer (in most parts), with inner circular and outer longitudinal fibers; responsible for peristalsis (movement of food). The stomach has three layers. UES (upper esophageal sphincter) & LES (lower esophageal sphincter) are crucial parts of this layer.
      • Serosa: outermost layer, also called visceral peritoneum. Secretes serous fluid to reduce friction in the abdominal cavity; some parts of the GI tract don't have serosa and have Adventitia (e.g. esophagus).

    • GI Tract Innervation:

      • Enteric Nervous System (ENS): the "brain of the gut" responsible for regulating gut function via two sets of interconnected neurons:
        • Myenteric plexus: located between the circular and longitudinal smooth muscle layers of the muscularis; regulates motility (movement).
        • Submucosal plexus: located within the submucosa; regulates secretions.
      • Autonomic Nervous System (ANS): Extrinsic innervation; parasympathetic (increases secretions and motility) and sympathetic (decreases secretions and activity) divisions affect the ENS. The vagus nerve supplies the parasympathetic fibers to most of the GI tract, excluding part of large intestine, which receives innervation from sacral spinal cord. Sympathetic fibers originate from the thoracic and lumbar regions of the spinal cord.

    • Mouth (Oral Cavity):

      • Cheeks, hard and soft palates, tongue form the mouth.
      • Salivary glands produce saliva to lubricate, dissolve, and begin chemical digestion of food.
      • Saliva is primarily water (99.5%) and contains enzymes like amylase (to digest starch) and lipase (to digest fats).

    • Pharynx:

      • Passageway for both air and food. Three parts: nasopharynx (respiration only), oropharynx, and laryngopharynx (both respiration and digestion).

    • Esophagus:

      • Muscular tube connecting pharynx to stomach; no digestion or absorption occurs here.
      • Upper Esophageal Sphincter (UES) and Lower Esophageal Sphincter (LES) control movement of food.
      • The superior 1/3 of the esophagus muscularis has skeletal muscle, middle 1/3 has both smooth and skeletal muscles, and the inferior 1/3 has only smooth muscle. The esophagus has an adventitia layer instead of serosa.

    • Swallowing (Deglutition) Stages:

      • Voluntary: tongue pushes bolus into oropharynx
      • Pharyngeal: involuntary, bolus moves through pharynx, epiglottis closes over larynx
      • Esophageal: involuntary, bolus moves through esophagus to stomach via peristalsis

    • Peritoneum:

      • Largest serous membrane lining the abdominal cavity; two layers: visceral (covers organs) and parietal (lines the abdominal wall).
      • The space between these layers (peritoneal cavity) is filled with lubricating fluid.

    • Retroperitoneal organs do not have visceral peritoneum; only their anterior surface.

      • Retroperitoneal organs include the kidneys, pancreas, duodenum, ascending and descending colon.

    • Peritoneal folds:

      • Greater omentum, falciform ligament, lesser omentum, mesentery, and mesocolon stabilize the digestive organs and contain blood vessels.
      • Greater omentum is the largest, drapes over intestines, and can accumulate adipose tissue.
      • Falciform ligament attaches the liver to the abdominal wall and diaphragm.
      • Lesser omentum connects the liver to the stomach and duodenum.
      • Mesentery anchors the small intestine
      • Mesocolon anchors the large intestine

    Additional Notes

    • GERD (Gastroesophageal Reflux Disease) is a condition that arises when the lower esophageal sphincter fails to close properly allowing stomach contents to reflux into the esophagus.

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    Description

    Explore the anatomy and functions of the digestive system with this quiz. Learn about the gastrointestinal tract and accessory organs, as well as the processes of mechanical and chemical digestion. Test your understanding of how food is broken down into essential nutrients.

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