Large Intestine Structure and Function
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Large Intestine Structure and Function

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Questions and Answers

What is the structure located at the junction of the small intestine and large intestine?

  • Rectum
  • Cecum (correct)
  • Sigmoid colon
  • Transverse colon

    • Which part of the large intestine is shaped like an S?

  • Sigmoid colon (correct)
  • Descending colon
  • Cecum
  • Ascending colon

    • What is primarily transported to the large intestine from the small intestine each day?

  • Bile fluid
  • 500 ml of chyme (correct)
  • Waste products only
  • Nutrient-rich blood

    • What is the role of the gastrocolic reflex?

    <p>Triggering bowel contractions</p> Signup and view all the answers

    Which of the following describes the configuration of the colon?

    <p>Straight portions</p> Signup and view all the answers

    What type of muscle composes the internal anal sphincter?

    <p>Smooth muscle</p> Signup and view all the answers

    Hirschprung’s disease primarily affects which part of the body?

    <p>Large intestine</p> Signup and view all the answers

    What is a common cause of constipation?

    <p>Low fiber diet</p> Signup and view all the answers

    Where does intestinal gas primarily come from?

    <p>Bacterial fermentation</p> Signup and view all the answers

    The rectum is the terminal part of which structure?

    <p>Large intestine</p> Signup and view all the answers

    What is primarily absorbed by the large intestine?

    <p>Water and salt</p> Signup and view all the answers

    What structure in the large intestine is responsible for forming pouch-like sacs?

    <p>Taeniae coli</p> Signup and view all the answers

    Which of the following statements about the mucosa of the large intestine is true?

    <p>It contains a higher density of goblet cells.</p> Signup and view all the answers

    What role do the goblet cells in the large intestine play?

    <p>Secretion of mucus</p> Signup and view all the answers

    What is the composition of the material entering the large intestine daily?

    <p>Unabsorbed biliary compounds and some fluid</p> Signup and view all the answers

    How much fluid is typically absorbed by the large intestine per day?

    <p>350 ml</p> Signup and view all the answers

    Which segment does NOT completely surround the large intestine?

    <p>Transverse colon</p> Signup and view all the answers

    What is the primary function of the large intestine's smooth muscle?

    <p>Facilitating excretion</p> Signup and view all the answers

    Which of the following correctly describes haustral contractions?

    <p>They are responsible for the segmentation of the colon.</p> Signup and view all the answers

    What is primarily eliminated from the large intestine on a daily basis?

    <p>150 ml of solid waste</p> Signup and view all the answers

    What is the primary role of the large intestine?

    <p>Storage and elimination of waste</p> Signup and view all the answers

    Which of the following best describes the cecum?

    <p>A blind-ended pouch located below the small intestine</p> Signup and view all the answers

    What region of the large intestine forms an S-shape?

    <p>Sigmoid colon</p> Signup and view all the answers

    What is one characteristic of the large intestine's structure?

    <p>It has haustra that form pouch-like sacs</p> Signup and view all the answers

    Which muscle type constitutes the internal anal sphincter?

    <p>Smooth muscle</p> Signup and view all the answers

    What is one function of the taeniae coli in the large intestine?

    <p>Facilitating contraction and movement</p> Signup and view all the answers

    What facilitates the defecation reflex?

    <p>Nerve endings in the sigmoid colon</p> Signup and view all the answers

    Which statement regarding intestinal gas is accurate?

    <p>It arises mainly from bacterial fermentation in the colon.</p> Signup and view all the answers

    Hirschprung’s disease primarily affects which portion of the gastrointestinal system?

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

    Constipation may result from which of the following?

    <p>Lack of dietary fiber</p> Signup and view all the answers

    What primarily drives the absorption of sodium ions in the large intestine?

    <p>Active transport</p> Signup and view all the answers

    What is the primary content that the large intestine absorbs?

    <p>Water and salts</p> Signup and view all the answers

    What causes the large intestine to form pouch-like structures called haustra?

    <p>Shorter longitudinal muscle bands</p> Signup and view all the answers

    What role do goblet cells in the large intestine perform?

    <p>Mucus secretion</p> Signup and view all the answers

    What is the daily volume of fluid that typically enters the colon?

    <p>500 ml</p> Signup and view all the answers

    What is the layer of muscle that forms the outer longitudinal structure of the colon known as?

    <p>Teniae coli</p> Signup and view all the answers

    Which of the following best describes the condition of the mucosal surface in the large intestine?

    <p>Smooth and less absorptive</p> Signup and view all the answers

    What is the main function of the large intestine?

    <p>Store waste and absorb water</p> Signup and view all the answers

    How much fluid is typically eliminated daily from the large intestine?

    <p>150 ml</p> Signup and view all the answers

    What characterizes haustral contractions in the large intestine?

    <p>They are involuntary muscle contractions.</p> Signup and view all the answers

    Study Notes

    Large Intestine Structure and Role

    • The large intestine (LI) is responsible for drying out the contents of the digestive tract and storing waste.
    • The LI consists of the colon, cecum, appendix, and rectum.
    • The cecum is a blind-ended pouch where the small intestine (SI) meets the LI at the ileocecal valve.
    • The appendix is a fingerlike projection at the bottom of the cecum, containing lymphoid tissue.
    • The colon is the longest portion of the LI and is divided into three straight sections: the ascending, transverse, and descending colon.
    • The terminal part of the descending colon becomes S-shaped, forming the sigmoid colon.
    • The sigmoid colon straightens out as the rectum.

    LI Motility

    • The LI receives approximately 500 ml of chyme per day from the SI.
    • Haustral contractions are slow, segmental contractions that occur every 30 minutes.
    • These contractions mix and propel the contents of the colon.
    • The haustral contractions create pouch-like sacs called haustra.
    • The longitudinal smooth muscle of the LI does not completely surround the colon, but forms three separate bands known as the taenia coli.
    • The taenia coli are shorter than the underlying circular smooth muscle layer, causing the LI to bunch up and form the haustra.

    Gastrocolic Reflex

    • The gastrocolic reflex is a reflex that is stimulated by the presence of food in the stomach.
    • This reflex intensifies colonic motility and promotes defecation.
    • The reflex is mediated by the autonomic nervous system.

    Defecation Reflex

    • The defecation reflex is triggered by distention of the rectum.
    • This reflex causes relaxation of the internal anal sphincter and contraction of the rectum.
    • The external anal sphincter is a voluntary muscle that can be consciously controlled to delay defecation.

    Luminal Surface of the LI

    • The luminal surface of the LI is smooth and has a decreased absorptive capacity.
    • The colon absorbs water and salt.
    • Sodium (Na+) is actively absorbed, followed by chloride (Cl-) passively.
    • Water follows osmotically.

    LI Secretion

    • The LI secretes mucus.
    • Goblet cells are abundant in the LI and are responsible for mucus secretion.
    • Mucus provides lubrication and protection from the contents of the colon.

    LI Pathophysiology

    • Hirschsprung's Disease: A congenital defect where there is a lack of ganglion cells in a portion of the colon.
    • Constipation: Characterized by infrequent bowel movements, hard stools, and difficulty passing stool.
    • Causes of Constipation: Lack of fiber, insufficient water intake, stress, medications, and certain medical conditions.

    Intestinal Gas

    • Intestinal gas is produced by bacterial fermentation in the colon.
    • Common sources of intestinal gas include carbohydrates, fiber, and proteins.

    Large Intestine Structure

    • The large intestine (LI) consists of the colon, cecum, appendix, and rectum.
    • The cecum is a blind-ended pouch at the junction of the small intestine (SI) and LI.
    • The appendix is a finger-like projection at the bottom of the cecum containing lymphoid tissue.
    • The colon makes up most of the LI and has three straight portions: ascending, transverse, and descending colon.
    • The sigmoid colon is S-shaped and straightens out to form the rectum.

    Large Intestine Function

    • The LI receives approximately 500 ml of chyme from the SI per day.
    • The major role of the LI is to dry the intestinal contents and store them.
    • The LI absorbs water and salt, primarily sodium (Na+) actively, which is followed by passive chloride (Cl-) absorption. Water follows osmotically.
    • The LI forms firm fecal matter through absorption, with 500 ml entering and 350 ml being absorbed daily, resulting in 150 ml being eliminated daily.

    Large Intestine Histology

    • The LI's luminal surface is smooth with a reduced absorptive capacity.
    • The LI mucosa lacks villi but has thicker crypts with a higher concentration of goblet cells.
    • Goblet cells secrete mucus providing lubrication and protection.

    Large Intestine Motility

    • The outer longitudinal smooth muscle (SM) in the LI does not completely surround the structure.
    • Three separate bands of muscle form the taeniae coli.
    • The taeniae coli are shorter than the underlying circular SM layer causing bunching-up and pouch-like sacs known as haustra.

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    Large Intestine Lecture Notes Fall 2024 PDF

    Description

    Explore the anatomy and role of the large intestine in digestion. This quiz covers the various components of the large intestine, including the colon, cecum, appendix, and rectum, as well as its motility and contractions. Test your knowledge on this essential part of the digestive system.

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