ANA 221: Histology of Alimentary Canal II
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Questions and Answers

What is the main function of the mucous secreted by the lining epithelium in the stomach?

  • To aid in the digestion of food
  • To protect the gastric mucosa against acid and enzymes (correct)
  • To produce blood group factors
  • To stimulate the contraction of smooth muscles

    • What is the type of epithelium found in the lining epithelium of the stomach?

  • Cuboidal
  • Columnar (correct)
  • Squamous
  • Transitional

    • What is the name of the depressions formed by the lining epithelium dipping into the lamina propria?

  • Gastric pits (correct)
  • Gastric glands
  • Mucous membrane folds
  • Lamina propria pits

    • What is the outermost layer of the stomach wall?

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

    What is the layer of smooth muscle found in the mucous membrane of the stomach?

    <p>Muscularis mucosae</p> Signup and view all the answers

    What happens to the mucous membrane folds in the stomach when it is distended?

    <p>They disappear</p> Signup and view all the answers

    What is the function of the blood group factors produced by the mucous cells?

    <p>To determine an individual's blood type</p> Signup and view all the answers

    What is the layer of connective tissue that supports the epithelium in the mucous membrane of the stomach?

    <p>Lamina propria</p> Signup and view all the answers

    What is the primary function of the cells with a striated border in the colon?

    <p>To absorb excess water and electrolytes from intestinal contents</p> Signup and view all the answers

    What type of cells are present in the epithelium overlying solitary lymphatic follicles?

    <p>M-cells</p> Signup and view all the answers

    What is the function of mucous secreted by goblet cells?

    <p>To facilitate the passage of semisolid contents through the colon</p> Signup and view all the answers

    What is characteristic of the vermiform appendix?

    <p>It has a poorly formed crypts</p> Signup and view all the answers

    What type of cells are not present in the mucosa of the colon?

    <p>Paneth cells</p> Signup and view all the answers

    What is the function of antibodies secreted by columnar cells?

    <p>To provide protection against pathogenic organisms</p> Signup and view all the answers

    What is characteristic of the serous layer in the posterior aspect of the ascending and descending colon?

    <p>It is absent</p> Signup and view all the answers

    What are the yellow masses filled with fat that are present in the peritoneum?

    <p>Appendices epiploicae</p> Signup and view all the answers

    What is the characteristic of the mucosa in the stomach?

    <p>Thick and packed with numerous gastric glands</p> Signup and view all the answers

    What is the purpose of the circular folds in the small intestine?

    <p>To slow down the passage of contents through the small intestine</p> Signup and view all the answers

    What type of glands are present in the pyloric region of the stomach?

    <p>None of the above</p> Signup and view all the answers

    What is the shape of the main gastric glands?

    <p>Simple or branched tubular glands</p> Signup and view all the answers

    What is the name of the projections that increase the surface area of the mucous membrane?

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

    What is the orientation of the main gastric glands to the mucosal surface?

    <p>At right angles to the mucosal surface</p> Signup and view all the answers

    What is the function of the pyloric sphincter?

    <p>To regulate the passage of food from the stomach to the small intestine</p> Signup and view all the answers

    What is the most numerous type of cell in the epithelium lining the glands?

    <p>Chief cells, peptic cells, or zymogen cells</p> Signup and view all the answers

    What is the length of the small intestine?

    <p>Five meters</p> Signup and view all the answers

    What is the characteristic of the cytoplasm of chief cells?

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

    What is the name of the valves that are also known as circular folds?

    <p>Valves of Kerkring</p> Signup and view all the answers

    What is the function of the microvilli?

    <p>To increase the surface area of the mucous membrane</p> Signup and view all the answers

    What is the location of oxyntic or parietal cells?

    <p>Singly, amongst the peptic cells</p> Signup and view all the answers

    What is the characteristic of oxyntic or parietal cells?

    <p>Large and ovoid or polyhedral</p> Signup and view all the answers

    In which part of the small intestine are the circular folds most prominent?

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

    What is the number of layers that make up the wall of the small intestine?

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

    What is a characteristic of the lymphoid tissue in the submucosa?

    <p>It gradually increases and is best seen in children around 10 years old.</p> Signup and view all the answers

    What is unique about the longitudinal muscle in the rectum compared to the colon?

    <p>It forms a continuous coat.</p> Signup and view all the answers

    Which part of the rectum is devoid of a serous covering?

    <p>The lower two-thirds.</p> Signup and view all the answers

    What is the length of the anal canal?

    <p>4 cm.</p> Signup and view all the answers

    What type of epithelium lines the upper part of the anal canal?

    <p>Columnar epithelium.</p> Signup and view all the answers

    What is the purpose of the anal valves?

    <p>To unite the lower ends of the anal columns.</p> Signup and view all the answers

    What is the characteristic of the mucosa in the pecten or transitional zone?

    <p>It has a bluish appearance due to a dense venous plexus.</p> Signup and view all the answers

    What is the name of the transverse line formed by the anal valves?

    <p>Pectinate line.</p> Signup and view all the answers

    Study Notes

    Stomach

    • The wall of the stomach has four basic layers: mucous membrane, submucosa, muscularis externa, and serous layer.
    • The mucous membrane shows numerous folds (rugae) that disappear when the stomach is distended.
    • The mucous membrane is composed of:
      • A lining epithelium that is columnar and mucous-secreting.
      • A layer of connective tissue, the lamina propria, that supports the epithelium.
      • A thin layer of smooth muscle called the muscularis mucosae.
    • The lining epithelium cells have apical parts filled with mucin that is usually removed during processing, making them appear empty or vacuolated.
    • Mucous secreted by the lining epithelium cells protects the gastric mucosa against acid and enzymes produced by the mucosa itself.
    • The lining epithelium dips into the lamina propria to form the walls of depressions called gastric pits, which extend for a variable distance into the thickness of the mucosa.
    • Deep to the gastric pits, the mucous membrane is packed with numerous gastric glands of three types: main gastric, cardiac, and pyloric.

    Main Gastric Glands

    • The main gastric glands are present over most of the stomach, but not in the pyloric region and in a small area near the cardiac end.
    • The main gastric glands are simple or branched tubular glands that lie at right angles to the mucosal surface.
    • The glands open into gastric pits, each pit receiving the openings of several glands.
    • The epithelium lining the glands is composed of:
      • Chief cells (peptic cells or zymogen cells) that are cuboidal or low columnar and contain prominent secretory granules in the apical parts of their cytoplasm.
      • Oxyntic or parietal cells that are large, ovoid or polyhedral, and contain a large central nucleus.

    Small Intestine

    • The small intestine is a tube about five meters long, divided into three parts.
    • The wall of the small intestine is made up of the four basic layers: mucous membrane, submucosa, muscularis externa, and serous layer.
    • The mucous membrane of the small intestine has a large surface area due to:
      • Its considerable length.
      • The presence of numerous circular folds (valves of Kerkring) in the mucosa.
      • The presence of numerous finger-like processes (villi) that project from the surface of the mucosa into the lumen.
      • The presence of numerous depressions (crypts) that invade the lamina propria.
      • The presence of microvilli on the luminal surfaces of the cells lining the mucosa.

    Large Intestine

    • The large intestine is composed of the colon, vermiform appendix, and rectum.
    • The colon has a mucous membrane with a large surface area due to:
      • The presence of numerous circular folds (valves of Kerkring) in the mucosa.
      • The presence of numerous finger-like processes (villi) that project from the surface of the mucosa into the lumen.
      • The presence of numerous depressions (crypts) that invade the lamina propria.
      • The presence of microvilli on the luminal surfaces of the cells lining the mucosa.
    • The mucous membrane of the colon is lined by an epithelium made up predominantly of columnar cells with a striated border.
    • The main function of the columnar cells is to absorb excess water and electrolytes from intestinal contents.
    • Many columnar cells secrete mucous and antibodies (IgA), providing protection against pathogenic organisms.

    Vermiform Appendix

    • The structure of the vermiform appendix resembles that of the colon with the following differences:
      • The appendix is the narrowest part of the gut.
      • The crypts are poorly formed.
      • The longitudinal muscle coat is complete and equally thick all around.
      • Taenia coli are not present.
      • The submucosa contains abundant lymphoid tissue that may completely fill the submucosa.

    Rectum

    • The structure of the rectum is similar to that of the colon except for the following:
      • A continuous coat of longitudinal muscle is present.
      • There are no taenia.
      • Peritoneum covers the front and sides of the upper one-third of the rectum, and only the front of the middle third.
      • There are no appendices epiploicae.

    Anal Canal

    • The anal canal is about 4 cm long, with the upper 3 cm lined by mucous membrane and the lower 1 cm lined by skin.
    • The area lined by mucous membrane can be further divided into an upper part (15 mm) and a lower part (15 mm).
    • The mucous membrane of the upper 15 mm of the canal is lined by columnar epithelium and shows six to twelve longitudinal folds (anal columns).
    • The lower ends of the anal columns are united to each other by short transverse folds (anal valves) that form a transverse line (pectinate line).
    • The mucous membrane of the next 15 mm of the rectum is lined by non-keratinized stratified squamous epithelium and does not have anal columns.

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    Description

    Lecture notes on the histology of the stomach, small intestine, and large intestine, covering the mucous membrane, epithelia, and muscles. Part of the ANA 221 course.

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