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Key Terms Chapter 23: The Digestive System

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    62675
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    absorption
    passage of digested products from the intestinal lumen through mucosal cells and into the bloodstream or lacteals
    accessory digestive organ
    includes teeth, tongue, salivary glands, gallbladder, liver, and pancreas
    accessory duct
    (also, duct of Santorini) duct that runs from the pancreas into the duodenum
    acinus
    cluster of glandular epithelial cells in the pancreas that secretes pancreatic juice in the pancreas
    alimentary canal
    continuous muscular digestive tube that extends from the mouth to the anus
    aminopeptidase
    brush border enzyme that acts on proteins
    anal canal
    final segment of the large intestine
    anal column
    long fold of mucosa in the anal canal
    anal sinus
    recess between anal columns
    appendix
    (vermiform appendix) coiled tube attached to the cecum
    ascending colon
    first region of the colon
    bacterial flora
    bacteria in the large intestine
    bile
    alkaline solution produced by the liver and important for the emulsification of lipids
    bile canaliculus
    small duct between hepatocytes that collects bile
    bilirubin
    main bile pigment, which is responsible for the brown color of feces
    body
    mid-portion of the stomach
    bolus
    mass of chewed food
    brush border
    fuzzy appearance of the small intestinal mucosa created by microvilli
    cardia
    (also, cardiac region) part of the stomach surrounding the cardiac orifice (esophageal hiatus)
    cecum
    pouch forming the beginning of the large intestine
    cementum
    bone-like tissue covering the root of a tooth
    central vein
    vein that receives blood from hepatic sinusoids
    cephalic phase
    (also, reflex phase) initial phase of gastric secretion that occurs before food enters the stomach
    chemical digestion
    enzymatic breakdown of food
    chief cell
    gastric gland cell that secretes pepsinogen
    chylomicron
    large lipid-transport compound made up of triglycerides, phospholipids, cholesterol, and proteins
    chyme
    soupy liquid created when food is mixed with digestive juices
    circular fold
    (also, plica circulare) deep fold in the mucosa and submucosa of the small intestine
    colon
    part of the large intestine between the cecum and the rectum
    common bile duct
    structure formed by the union of the common hepatic duct and the gallbladder’s cystic duct
    common hepatic duct
    duct formed by the merger of the two hepatic ducts
    crown
    portion of tooth visible superior to the gum line
    cuspid
    (also, canine) pointed tooth used for tearing and shredding food
    cystic duct
    duct through which bile drains and enters the gallbladder
    deciduous tooth
    one of 20 “baby teeth”
    defecation
    elimination of undigested substances from the body in the form of feces
    deglutition
    three-stage process of swallowing
    dens
    tooth
    dentin
    bone-like tissue immediately deep to the enamel of the crown or cementum of the root of a tooth
    dentition
    set of teeth
    deoxyribonuclease
    pancreatic enzyme that digests DNA
    descending colon
    part of the colon between the transverse colon and the sigmoid colon
    dipeptidase
    brush border enzyme that acts on proteins
    duodenal gland
    (also, Brunner’s gland) mucous-secreting gland in the duodenal submucosa
    duodenum
    first part of the small intestine, which starts at the pyloric sphincter and ends at the jejunum
    enamel
    covering of the dentin of the crown of a tooth
    enteroendocrine cell
    gastric gland cell that releases hormones
    enterohepatic circulation
    recycling mechanism that conserves bile salts
    enteropeptidase
    intestinal brush-border enzyme that activates trypsinogen to trypsin
    epiploic appendage
    small sac of fat-filled visceral peritoneum attached to teniae coli
    esophagus
    muscular tube that runs from the pharynx to the stomach
    external anal sphincter
    voluntary skeletal muscle sphincter in the anal canal
    fauces
    opening between the oral cavity and the oropharynx
    feces
    semisolid waste product of digestion
    flatus
    gas in the intestine
    fundus
    dome-shaped region of the stomach above and to the left of the cardia
    G cell
    gastrin-secreting enteroendocrine cell
    gallbladder
    accessory digestive organ that stores and concentrates bile
    gastric emptying
    process by which mixing waves gradually cause the release of chyme into the duodenum
    gastric gland
    gland in the stomach mucosal epithelium that produces gastric juice
    gastric phase
    phase of gastric secretion that begins when food enters the stomach
    gastric pit
    narrow channel formed by the epithelial lining of the stomach mucosa
    gastrin
    peptide hormone that stimulates secretion of hydrochloric acid and gut motility
    gastrocolic reflex
    propulsive movement in the colon activated by the presence of food in the stomach
    gastroileal reflex
    long reflex that increases the strength of segmentation in the ileum
    gingiva
    gum
    haustral contraction
    slow segmentation in the large intestine
    haustrum
    small pouch in the colon created by tonic contractions of teniae coli
    hepatic artery
    artery that supplies oxygenated blood to the liver
    hepatic lobule
    hexagonal-shaped structure composed of hepatocytes that radiate outward from a central vein
    hepatic portal vein
    vein that supplies deoxygenated nutrient-rich blood to the liver
    hepatic sinusoid
    blood capillaries between rows of hepatocytes that receive blood from the hepatic portal vein and the branches of the hepatic artery
    hepatic vein
    vein that drains into the inferior vena cava
    hepatocytes
    major functional cells of the liver
    hepatopancreatic ampulla
    (also, ampulla of Vater) bulb-like point in the wall of the duodenum where the bile duct and main pancreatic duct unite
    hepatopancreatic sphincter
    (also, sphincter of Oddi) sphincter regulating the flow of bile and pancreatic juice into the duodenum
    hydrochloric acid (HCl)
    digestive acid secreted by parietal cells in the stomach
    ileocecal sphincter
    sphincter located where the small intestine joins with the large intestine
    ileum
    end of the small intestine between the jejunum and the large intestine
    incisor
    midline, chisel-shaped tooth used for cutting into food
    ingestion
    taking food into the GI tract through the mouth
    internal anal sphincter
    involuntary smooth muscle sphincter in the anal canal
    intestinal gland
    (also, crypt of Lieberkühn) gland in the small intestinal mucosa that secretes intestinal juice
    intestinal juice
    mixture of water and mucus that helps absorb nutrients from chyme
    intestinal phase
    phase of gastric secretion that begins when chyme enters the intestine
    intrinsic factor
    glycoprotein required for vitamin B12 absorption in the small intestine
    jejunum
    middle part of the small intestine between the duodenum and the ileum
    labial frenulum
    midline mucous membrane fold that attaches the inner surface of the lips to the gums
    labium
    lip
    lactase
    brush border enzyme that breaks down lactose into glucose and galactose
    lacteal
    lymphatic capillary in the villi
    large intestine
    terminal portion of the alimentary canal
    laryngopharynx
    part of the pharynx that functions in respiration and digestion
    left colic flexure
    (also, splenic flexure) point where the transverse colon curves below the inferior end of the spleen
    lingual frenulum
    mucous membrane fold that attaches the bottom of the tongue to the floor of the mouth
    lingual lipase
    digestive enzyme from glands in the tongue that acts on triglycerides
    lipoprotein lipase
    enzyme that breaks down triglycerides in chylomicrons into fatty acids and monoglycerides
    liver
    largest gland in the body whose main digestive function is the production of bile
    lower esophageal sphincter
    smooth muscle sphincter that regulates food movement from the esophagus to the stomach
    main pancreatic duct
    (also, duct of Wirsung) duct through which pancreatic juice drains from the pancreas
    major duodenal papilla
    point at which the hepatopancreatic ampulla opens into the duodenum
    maltase
    brush border enzyme that breaks down maltose and maltotriose into two and three molecules of glucose, respectively
    mass movement
    long, slow, peristaltic wave in the large intestine
    mastication
    chewing
    mechanical digestion
    chewing, mixing, and segmentation that prepares food for chemical digestion
    mesoappendix
    mesentery of the appendix
    micelle
    tiny lipid-transport compound composed of bile salts and phospholipids with a fatty acid and monoacylglyceride core
    microvillus
    small projection of the plasma membrane of the absorptive cells of the small intestinal mucosa
    migrating motility complex
    form of peristalsis in the small intestine
    mixing wave
    unique type of peristalsis that occurs in the stomach
    molar
    tooth used for crushing and grinding food
    motilin
    hormone that initiates migrating motility complexes
    motility
    movement of food through the GI tract
    mucosa
    innermost lining of the alimentary canal
    mucosal barrier
    protective barrier that prevents gastric juice from destroying the stomach itself
    mucous neck cell
    gastric gland cell that secretes a uniquely acidic mucus
    muscularis
    muscle (skeletal or smooth) layer of the alimentary canal wall
    myenteric plexus
    (plexus of Auerbach) major nerve supply to alimentary canal wall; controls motility
    nucleosidase
    brush border enzyme that digests nucleotides
    oral cavity
    (also, buccal cavity) mouth
    oral vestibule
    part of the mouth bounded externally by the cheeks and lips, and internally by the gums and teeth
    oropharynx
    part of the pharynx continuous with the oral cavity that functions in respiration and digestion
    palatoglossal arch
    muscular fold that extends from the lateral side of the soft palate to the base of the tongue
    palatopharyngeal arch
    muscular fold that extends from the lateral side of the soft palate to the side of the pharynx
    pancreas
    accessory digestive organ that secretes pancreatic juice
    pancreatic amylase
    enzyme secreted by the pancreas that completes the chemical digestion of carbohydrates in the small intestine
    pancreatic juice
    secretion of the pancreas containing digestive enzymes and bicarbonate
    pancreatic lipase
    enzyme secreted by the pancreas that participates in lipid digestion
    pancreatic nuclease
    enzyme secreted by the pancreas that participates in nucleic acid digestion
    parietal cell
    gastric gland cell that secretes hydrochloric acid and intrinsic factor
    parotid gland
    one of a pair of major salivary glands located inferior and anterior to the ears
    pectinate line
    horizontal line that runs like a ring, perpendicular to the inferior margins of the anal sinuses
    pepsinogen
    inactive form of pepsin
    peristalsis
    muscular contractions and relaxations that propel food through the GI tract
    permanent tooth
    one of 32 adult teeth
    pharynx
    throat
    phosphatase
    brush border enzyme that digests nucleotides
    porta hepatis
    “gateway to the liver” where the hepatic artery and hepatic portal vein enter the liver
    portal triad
    bile duct, hepatic artery branch, and hepatic portal vein branch
    premolar
    (also, bicuspid) transitional tooth used for mastication, crushing, and grinding food
    propulsion
    voluntary process of swallowing and the involuntary process of peristalsis that moves food through the digestive tract
    pulp cavity
    deepest portion of a tooth, containing nerve endings and blood vessels
    pyloric antrum
    wider, more superior part of the pylorus
    pyloric canal
    narrow, more inferior part of the pylorus
    pyloric sphincter
    sphincter that controls stomach emptying
    pylorus
    lower, funnel-shaped part of the stomach that is continuous with the duodenum
    rectal valve
    one of three transverse folds in the rectum where feces is separated from flatus
    rectum
    part of the large intestine between the sigmoid colon and anal canal
    reticuloendothelial cell
    (also, Kupffer cell) phagocyte in hepatic sinusoids that filters out material from venous blood from the alimentary canal
    retroperitoneal
    located posterior to the peritoneum
    ribonuclease
    pancreatic enzyme that digests RNA
    right colic flexure
    (also, hepatic flexure) point, at the inferior surface of the liver, where the ascending colon turns abruptly to the left
    root
    portion of a tooth embedded in the alveolar processes beneath the gum line
    ruga
    fold of alimentary canal mucosa and submucosa in the empty stomach and other organs
    saccharolytic fermentation
    anaerobic decomposition of carbohydrates
    saliva
    aqueous solution of proteins and ions secreted into the mouth by the salivary glands
    salivary amylase
    digestive enzyme in saliva that acts on starch
    salivary gland
    an exocrine gland that secretes a digestive fluid called saliva
    salivation
    secretion of saliva
    segmentation
    alternating contractions and relaxations of non-adjacent segments of the intestine that move food forward and backward, breaking it apart and mixing it with digestive juices
    serosa
    outermost layer of the alimentary canal wall present in regions within the abdominal cavity
    sigmoid colon
    end portion of the colon, which terminates at the rectum
    small intestine
    section of the alimentary canal where most digestion and absorption occurs
    soft palate
    posterior region of the bottom portion of the nasal cavity that consists of skeletal muscle
    stomach
    alimentary canal organ that contributes to chemical and mechanical digestion of food from the esophagus before releasing it, as chyme, to the small intestine
    sublingual gland
    one of a pair of major salivary glands located beneath the tongue
    submandibular gland
    one of a pair of major salivary glands located in the floor of the mouth
    submucosa
    layer of dense connective tissue in the alimentary canal wall that binds the overlying mucosa to the underlying muscularis
    submucosal plexus
    (plexus of Meissner) nerve supply that regulates activity of glands and smooth muscle
    sucrase
    brush border enzyme that breaks down sucrose into glucose and fructose
    tenia coli
    one of three smooth muscle bands that make up the longitudinal muscle layer of the muscularis in all of the large intestine except the terminal end
    tongue
    accessory digestive organ of the mouth, the bulk of which is composed of skeletal muscle
    transverse colon
    part of the colon between the ascending colon and the descending colon
    upper esophageal sphincter
    skeletal muscle sphincter that regulates food movement from the pharynx to the esophagus
    Valsalva’s maneuver
    voluntary contraction of the diaphragm and abdominal wall muscles and closing of the glottis, which increases intra-abdominal pressure and facilitates defecation
    villus
    projection of the mucosa of the small intestine
    voluntary phase
    initial phase of deglutition, in which the bolus moves from the mouth to the oropharynx
    α-dextrin
    breakdown product of starch
    α-dextrinase
    brush border enzyme that acts on α-dextrins
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