Human Digestive System Quiz
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Questions and Answers

What is NOT a function of the digestive system?

  • Ingestion
  • Hormone regulation (correct)
  • Chemical digestion
  • Secretion

    • The largest organ of the digestive system is the stomach.

    False

    What are the three layers of the muscularis externa?

    Inner circular layer and outer longitudinal layer

    The __________ is the layer of the digestive tract that contains blood vessels, lymphatic vessels, and exocrine glands.

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

    Match the accessory organ of the digestive system with its primary function:

    <p>Liver = Production of bile Gallbladder = Storage of bile Pancreas = Secretion of digestive enzymes Salivary Glands = Production of saliva</p> Signup and view all the answers

    Which layer of the digestive tract is responsible for peristalsis?

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

    What do chief cells in the gastric glands primarily secrete?

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

    The ileum has numerous plicae and lacks lymphoid tissue.

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

    Which part of the small intestine is primarily responsible for the majority of nutrient absorption?

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

    The pH in the gastric lumen where pepsinogen is converted to pepsin ranges between _____ and _____.

    <p>1.5, 2.0</p> Signup and view all the answers

    Match the parts of the small intestine with their characteristics:

    <p>Duodenum = Few plicae, numerous villi, mucous glands Jejunum = Plicae and villi prominent in the proximal portion Ileum = Scattered villi, lacks plicae, contains Peyer's Patches</p> Signup and view all the answers

    What is the layer that connects the digestive tract to adjacent structures without a serosa called?

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

    Salivary glands produce saliva that aids only in taste.

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

    Name the four major components of saliva.

    <p>Mucus, Amylase, Lingual Lipase, Alkaline Electrolyte Solution</p> Signup and view all the answers

    The _____ is a hollow muscular tube that transfers solid food and liquids to the stomach.

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

    Match the salivary glands with their primary functions:

    <p>Submandibular Glands = Produce buffers, mucins &amp; salivary amylase Sublingual Glands = Contain mucus cells Parotid Glands = Contain only serous cells –salivary amylase</p> Signup and view all the answers

    Which function is NOT performed by saliva?

    <p>Aid in breathing</p> Signup and view all the answers

    The muscularis externa of the pharynx is composed of skeletal muscle.

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

    What stimulates an increase in salivary secretion from the PNS?

    <p>Thinking about or smelling food</p> Signup and view all the answers

    Which structure regulates the passage of bolus into the stomach?

    <p>Cardiac Sphincter Muscles</p> Signup and view all the answers

    The esophagus has a serosa layer.

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

    What type of epithelium lines the mucosa of the esophagus?

    <p>nonkeratinized stratified squamous epithelium</p> Signup and view all the answers

    The muscularis externa of the esophagus contains __________ and __________ muscle.

    <p>circular, longitudinal</p> Signup and view all the answers

    Match the following phases of swallowing with their characteristics:

    <p>Oral Phase = Voluntary phase where bolus is formed Pharyngeal Phase = Involuntary phase triggered by the bolus entering pharynx Esophageal Phase = Peristalsis moves bolus toward the stomach All phases = Involved in the process of swallowing</p> Signup and view all the answers

    Which type of muscle is found in the first third of the esophagus?

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

    Hydrochloric acid in the stomach helps activate and function pepsin.

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

    Name the two types of cells found in gastric glands and their functions.

    <p>Parietal Cells produce intrinsic factor &amp; HCl; Chief Cells produce Pepsinogen.</p> Signup and view all the answers

    The esophagus extends from the __________ to the stomach.

    <p>cricoid cartilage</p> Signup and view all the answers

    What is one of the primary functions of the stomach?

    <p>Bulk storage of ingested food</p> Signup and view all the answers

    Study Notes

    The Digestive System

    • The gastrointestinal system consists of the digestive tract and accessory organs.
    • The digestive tract includes the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.
    • Accessory organs include teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

    General Functions of the Digestive System

    • Ingestion: taking food into the body.
    • Mechanical processing: physically breaking down food.
    • Chemical digestion: breaking down food into simpler chemical units.
    • Secretion: releasing water, acids, enzymes, and buffers.
    • Absorption: taking up useful molecules into the body.
    • Egestion: removing waste from the body.

    Layers of the Digestive Tract Wall

    • Mucosa: innermost layer, composed of epithelium, lamina propria, and muscularis mucosae.
    • Submucosa: a layer of dense connective tissue containing blood vessels, lymphatic vessels, exocrine glands, and submucosal nerve plexus (Meissner's plexus).
    • Muscularis externa: layer of smooth muscle responsible for peristalsis and segmentation.
    • Serosa: outermost layer, a serous membrane found in most parts of the tract, except for oral cavity, pharynx, esophagus and rectum (these regions use adventitia instead of serosa).

    Mucosa (Epithelial and Lamina Propria)

    • The epithelium layer is folded to create a large surface area for digestion. The epithelium can be stratified (e.g., oral cavity, pharynx, esophagus, and anal canal) or simple (e.g., stomach and most of the large intestine).
    • Lamina propria is a layer of loose connective tissue. Its composition includes blood vessels, lymphatic vessels, sensory nerve endings, smooth muscle cells, and scattered lymphoid tissues, and secretory cells of mucus glands.

    Submucosa

    • This layer lies below the mucosa, made up of dense connective tissue.
    • Contains blood vessels, lymphatic vessels, exocrine glands, and nerve plexuses (Meissner's plexus).
    • Sensory neurons, parasympathetic ganglionic neurons, and sympathetic postganglionic fibres innervate this layer and the mucosa.

    Muscularis Externa

    • This layer is primarily composed of smooth muscle cells.
    • Composed of inner circular and outer longitudinal layers.
    • Its contraction is essential for peristalsis and segmentation.
    • The enteric nervous system (ENS) coordinates muscle movements.
    • The ENS is innervated by the autonomic nervous system (ANS), with sympathetic and parasympathetic fibers.
    • Parasympathetic stimulation increases muscle tone and activity.

    Serosa

    • Serous membrane that covers most parts of the muscularis externa.
    • Exceptions include oral cavity, pharynx, esophagus, and rectum, which are covered by adventitia (a dense network of collagen fibres).

    Oral Cavity

    • Analysis of material before swallowing.
    • Mechanical processing by teeth, tongue, and palate surfaces.
    • Lubrication with mucus and salivary secretions.
    • Limited digestion of carbohydrates and lipids (salivary amylase and lingual lipase).

    Salivary Glands

    • Submandibular glands produce buffers, mucins, and salivary amylase.
    • Sublingual glands contain mucus cells.
    • Parotid glands contain only serous cells and salivary amylase.

    Salivary Functions

    • Keeps oral surfaces clean.
    • Moistens and lubricates mouth and food.
    • Aids in tasting.
    • Aids in swallowing.
    • Helps in the metabolism of carbohydrates.
    • Helps maintain the calcium phosphate matrix of the teeth, and saliva contains thiocyanates and lysozymes that destroy oral bacteria.

    Teeth

    • Permanent teeth eruption chart includes the age at which various teeth come in.

    Pharynx

    • The muscularis externa is composed of skeletal muscle.

    Esophagus

    • A hollow muscular tube transferring solid food and liquids to the stomach.
    • Extends from the cricoid cartilage, along the posterior surface of the trachea, and through the diaphragm.
    • Cardiac sphincter muscles regulate the passage of bolus into the stomach.

    Histology of Esophagus

    • Mucosa: non-keratinized stratified squamous epithelium (with mucus-secreting glands in the submucosa) .
    • Submucosa: contains mucus-secreting glands.
    • Muscularis externa: first third skeletal muscle, middle third contains both skeletal and smooth muscle, inferior third smooth muscle.
    • No serosa but adventitia of connective tissue.

    The Cardiac Sphincter/ Lower Esophageal Sphincter

    • Regulates the passage of bolus from the esophagus into the stomach.

    Mechanism of Swallowing

    • Consists of three phases: oral, pharyngeal, and esophageal.

    Oral Phase of Swallowing

    • Voluntary phase.
    • Hard palate compresses the bolus (food).
    • Tongue forces bolus into oropharynx.
    • Soft palate elevates to protect airway.

    Pharyngeal Phase of Swallowing

    • Involuntary phase.
    • Tactile receptors on palatal arches/uvula are stimulated, which triggers the swallowing centre in the medulla oblongata.
    • Pharyngeal muscles contract to push bolus into esophagus.
    • Larynx elevates to block the trachea. - Respiratory centre inhibited.

    Esophageal Phase of Swallowing

    • Bolus enters the esophagus.
    • Peristalsis occurs (wave-like muscle contractions), pushing the bolus to the stomach.
    • Cardiac sphincter muscles open.
    • Bolus enters the stomach.

    The Stomach

    • Functions include bulk storage of ingested food, mechanical breakdown of ingested food, disruption of chemical bonds in food, and production of intrinsic factor.

    Stomach Histology

    • The stomach has four regions: cardia, fundus, body, and pylorus.
    • The muscularis externa has an additional oblique layer of smooth muscle to enhance mixing and churning.
    • Stomach mucosa contains gastric pits which open to the gastric glands containing parietal, chief, mucous neck, and enteroendocrine cells.

    Gastric Glands

    • Parietal cells produce intrinsic factor and HCl.
    • Chief cells produce pepsinogen.
    • Other components of stomach lining include mucous neck cells and enteroendocrine cells which produce hormones (e.g. gastrin).
    • HCl kills microbes, denatures proteins, and activates pepsin.
    • Pepsinogen converts to pepsin within a low pH.
    • Renin and gastric lipase are present in infant stomachs.

    Pyloric Glands

    • Produce mucus and hormones (e.g. gastrin, somatostatin).
    • Some enteroendocrine cells regulate parietal and chief cell function, promoting gastric mixing..

    Small Intestines and Accessory Organs

    • Extends from the pyloric sphincter to the cecum (approximately 7 meters long).
    • Divided into three parts: duodenum, jejunum, and ileum.
    • 90% of absorption takes place in the small intestines.

    Small Intestine Enzymes

    • Pancreas secretes pancreatic amylase (carbohydrates), pancreatic lipase (lipids), nucleases (nucleic acids), and proteolytic enzymes (proteins) into the small intestine.
    • The liver and gallbladder secrete bile into the small intestine.

    Small Intestine Histology

    • Structural features of the small intestines include folds (plicae circulares), villi (finger-like projections), and microvilli (tiny projections on the surface of each cell).
    • The lamina propria has capillaries for nutrient and gas transport to the hepatic portal vein, and lacteals (lymphatic vessels) transport larger substances (e.g., chylomicrons).

    Intestinal Secretions

    • Intestinal secretions contain mucus and brush border enzymes (e.g., enterokinase, maltase, sucrase, lactase, dipeptidases, and peptidases).

    Digestion in the Small Intestine - The Pancreas

    • Pancreatic juice contains sodium bicarbonate (pH 7.5–8.8) which neutralizes acidic chyme in the duodenum.
    • Pancreatic enzymes are released when chyme enters the duodenum and when the hormone secretin is produced.
    • Pancreatic enzymes (e.g., amylase, lipase, nucleases, proteolytic enzymes) complete digestion of food.

    Digestion in the Small Intestine - The Liver

    • The liver produces bile, which is stored in the gallbladder.
    • Bile is released into the duodenum and contains water, various ions, bilirubin, cholesterol, and bile salts.
    • Bile salts increase the surface area for fat digestion by pancreatic lipase.
    • Bile also helps facilitate the absorption of lipids by intestinal epithelium.

    Bile Salt Emulsification

    • Bile salts emulsify fats, increasing the surface area for lipase to act upon.

    Absorption in the Small Intestine – General

    • Absorption of monosaccharides occurs along the duodenum and upper jejunum with sodium.
    • Absorption of amino acids occurs along the end of the jejunum with sodium.

    Absorption in the Small Intestine – Lipids

    • Fatty acids and monoglycerides diffuse into epithelial cells.
    • They combine to form triglycerides, which combine with cholesterol, lipoproteins, and phospholipids to form chylomicrons.
    • Chylomicrons diffuse into lacteals.

    Absorption in the Small Intestine – Vitamins

    • Vitamins (C, B) are absorbed through passive diffusion.
    • B12 requires intrinsic factor for active transport.
    • Vitamins A, D, E, and K are absorbed with micelles.

    Large Intestine

    • Parts of the large intestine are the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.
    • Large intestine's job is to reclaim water and electrolytes, and to hold fecal matter.
    • The muscosa layer has goblet cells which secrete mucus, which protects the intestinal wall and holds fecal matter together.
    • It also contains sodium bicarbonate produced by bacteria to neutralize acidity.
    • Parts of the large intestine include cecum, ascending, transverse, descending, sigmoid, colon, rectum, and anal canal.

    Bacteria in the Large Intestine

    • Bacteria in the large intestine helps break down indigestible materials and produce B vitamins and vitamin K, which is required for blood clotting.

    Movement in the Large Intestine

    • Movement of fecal matter in the large intestine is due to peristalsis, segmentation, and contraction of longitudinal muscle bands.

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    Description

    Test your knowledge on the functions and components of the human digestive system. This quiz covers various aspects including the organs involved, their roles, and anatomical features essential for digestion. Perfect for students of biology or health sciences!

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