23.8: Key Terms

Example and Directions

Words (or words that have the same definition)	The definition is case sensitive	(Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages]	(Optional) Caption for Image	(Optional) External or Internal Link	(Optional) Source for Definition
(Eg. "Genetic, Hereditary, DNA ...")	(Eg. "Relating to genes or heredity")		The infamous double helix	https://bio.libretexts.org/	CC-BY-SA; Delmar Larsen

Glossary Entries

Word(s)	Definition	Image	Caption	Link	Source
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