Glossary: The Digestive System

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

anal canal final segment of the large intestine

anal column long fold of mucosa in the anal canal

anal sinus 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

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

descending colon part of the colon between the transverse colon and the sigmoid colon

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

haustrum small pouch in the colon created by tonic contractions of teniae coli

haustral contraction slow segmentation in the large intestine

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

intrinsic factor glycoprotein required for vitamin B12 absorption in the small intestine

intestinal phase phase of gastric secretion that begins when chyme enters the intestine

jejunum middle part of the small intestine between the duodenum and the ileum

labium lip

labial frenulum midline mucous membrane fold that attaches the inner surface of the lips to the gums

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

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

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

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

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 juice  secretion of the pancreas containing digestive enzymes and bicarbonate

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

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

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

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