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A&P - Ch 23

Digestive System

alimentary canal; digests and absorbs food; mouth, pharynx, esophagus, stomach, small intestine, large intestine digestive system
teeth, tongue, salivary glands, liver, gallbladder & pancreas accessory digestive organs
taking food into the digestive tract ingestion
moving of food through gut propulsion
propulsion includes swallowing & peristalsis
alternate waves of contraction & relaxation peristalsis
chewing, mixing food with saliva by tongue, peristalsis in stomach mechanical digestion
more/less stationary alternate contractions & relaxations segmentation
in peristalsis, adjacent segments of alimentary tract organs alternately contract & relax, which moves food along tract distally
in segmentation, nonadjacent segments of alimentary tract organs alternately contract and relax moving food forward then backward
food mixing & slow food propulsion occurs during segmentation
complex food molecules are broken down into simpler ones by enzymes chemical digestion
passage of digested end products along w/water from lumen of gut into blood/lymph absorption
elimination of indigestible substances from body as feces defecation
serous membrane of abdominal cavity peritoneum
located on external surface of most digestive organs visceral peritoneum
lines the body wall parietal peritoneum
located btwn two peritoneums; fluid lubricates mobile organs peritoneal cavity
double layer of peritoneum mesentery
travel in the mesentery blood vessels, lymphatics, & nerves
functions of the mesentery include holding organs in place & storing fat
lies posterior to peritoneum retroperitoneal organs
are surrounded by peritoneum intraperitoneal organs
mucous membrane layer of alimentary canal mucosa
connective tissue layer of alimentary canal submucosa
inner circular, outer longitudinal muscle layers of alimentary canal muscularis externa
visceral peritoneum layer of alimentary canal serosa
arterial supply that supports hepatic, splenic, & gastric, and inferior & superior mesenteric abdominal aorta
drains nutrient-rich blood from digestive organs & delivers it to liver first hepatic portal vein
alimentary canal has its own __ __ neurons intrinsic enteric
in alimentary canal, this regulates glands & smooth muscle in mucosa submucosal nerve plexus
in alimentary canal, this is located btwn muscle layers & controls GI tract motility myenteric nerve plexus
sympathetic & parasympathetic nerves are the __ __ of alimentary canal nervous system extrinsic control
in alimentary canal, this inhibits secretion & motility sympathetic nerves
in alimentary canal, this stimulates secretion & motility parasympathetic nerves
oral/buccal cavity is lined with stratified squamous epithelium
area btwn lips & cheeks, then teeth & gums vestibule
area that lies within teeth & gums oral cavity proper
area of median attachment of each lip to gums labial frenulum
palatine bones & palatine processes of maxillae hard palate
fold formed mostly of skeletal muscle, within oral cavity soft palate
closes off nasopharynx during swallowing function of soft palate
uvula __ __ from soft palate free edge projects downward
taste, mixing food during chewing, formation of bolus, helps in swallowing & speech functions of tongue
has intrinsic & extrinsic muscles tongue
attachment of lips to the gums lingual frenulum
surface of tongue shows papillae
whitish, provide friction; located on surface of tongue filiform papillae
reddish, scattered over tongue surface fungiform
V-shaped row in back of tongue surface circumvallate/vallate
papillae that are associated w/taste buds fungiform & circumvallate
arterial supply from abdominal aorta & hepatic portal vein make up splanchnic circulation
gland located anterior to ear parotid
open into vestibule next to 2nd upper molar parotid duct
gland medial to body of mandible submandibular gland
each submandibular gland duct opens on each side of lingual frenulum
gland located under tongue sublingual gland
sublingual gland ducts open into floor of mouth
contains electrolytes, salivary amylase, lipase & mucin and also lysozyme, defensins saliva
part of saliva that protects against bacteria lysozyme & defensins
continuously keep mouth moist intrinsic glands
parotid, submandibular, & sublingual glands are extrinsic
produce secretions when ingested food increases salivation stimulates receptors in mouth & parasympathetic stimulation
sympathetic stimulation inhibits salivation causing dry mouth
20 primary teeth are called deciduous
have deciduous teeth from 6-24 month of age
deciduous teeth include 2 incisors, 1 canine, 2 molars
permanent teeth develop, when roots are resorbed & teeth fall out at 6–12 years of age
there are 32 __ teeth permanent
permanent teeth include 2 incisors, 1 canine, 2 premolars, 3 molars
oropharynx & laryngopharynx make up pharynx
functions of oropharynx & laryngopharynx allow passage of food & air
oropharynx & laryngopharynx are made up of stratified squamous epithelium lining
oropharynx & laryngopharynx have __ muscle layer wall skeletal
muscular wall of oropharynx & laryngopharynx serves to contract & propel food into esophagus
is 10-inch muscular tube extends from pharynx to stomach esophagus
esophagus pierces diaphragm at esophageal hiatus
lined by stratified squamous epithelium esophageal mucosa
glands in submucosa of esophagus, secrete mucus that helps in bolus movement
made up of skeletal muscle superiorly & smooth muscle inferiorly muscularis layer of esophagus
outermost connective tissue layer of esophagus adventitia
ingestion of food; mechanical digestion; chemical digestion; propulsion are all digestive processes of mouth
chewing is __ digestion mechanical
salivary amylase breaks up polysaccharides during chemical digestion in mouth
propulsion in mouth/swallowing is called deglutition
voluntary contraction of tongue; 1st phase of deglutition buccal phase
involuntary contraction of tongue; 2nd phase of deglutition pharyngeal-esophageal phase
cardiac region of stomach surrounds cardiac orifice
dome-shaped region of stomach fundus
mid-portion of stomach body
antrum, pyloric canal, & pylorus pyloric region
convex; greater omentum hangs from it greater curvature
concave; extends lesser omentum btwn it & the liver lesser curvature
increase surface area of stomach ruggae
omentum is __ that __ stomach mesentery; surrounds
muscularis externa is made up of inner circular, outer longitudinal, & oblique muscle layers
activates pepsin, & kills many bacteria HCl acid
required for Vit. B12 absorption (lack of intrinsic factor → pernicious anemia intrinsic factor
( inactive form of pepsin) for protein digestion pepsinogen
gastrin is a(n) hormone
prevents self digestion of stomach mucosal barrier
mucosal barrier consists of layer of __ mucus bicarbonate-rich
mucosal barrier consists of __ __ between epithelial cells tight junctions
mucosal barrier consists of __ __ cells being quickly replaced by new cells damaged epithelial
inflammation caused by anything that breaches mucosal barrier gastritis
erosion of the stomach wall gastric ulcer
important cause of gastritis & ulcers Helicobacter pylori bacteria
__ of proteins by HCl is digestive process in stomach denaturation
protein __ begins by pepsin in stomach digestion
stomach delivers __ to small intestine chyme
neural control of stomach is through parasympathetic
hormonal control of stomach is through gastrin
stimulation of gastric secretion is under neural & hormonal controls
even before food enters stomach- by the site, smell & taste of food cephalic (reflex) phase
in cephalic (reflex) phase, signals from smell & taste receptors reach brain, resulting in vagus nerve stimulating the stomach
once food reaches the stomach; phase lasts for 3–4 hours provides most of gastric juice gastric phase
neural stimulation & gastrin involved in __ of gastric secretion regulation
intestinal gastrin as partially digested food enters duodenum (brief); increase gastric secretion stimulatory effect
decreases gastric secretion inhibitory effects
inhibitory effects work through neural pathway of enterogastric reflux
inhibitory effects work through neural pathway of intestinal hormones of CCK, secretin
also causes increase in HCl secretion histamine
stomach stretches in __ of food anticipation
stomach stretches to __ food as it enters without greatly increasing tension accommodate
stomach pressure __ __ until 1.5L of food is ingested remains constant
increased by distension of stomach by food & gastrin peristalsis
stretching & peristalsis are involved in gastric motility & emptying
peristaltic waves move from the fundus toward the pylorus propulsion
most vigorous peristalsis & mixing action occur close to pylorus grinding
pyloric end of stomach acts as pump that delivers small amounts of chyme into duodenum, simultaneously forcing most of contained material backward into stomach retropulsion
pyloric valve opens slightly during retropulsion
during cephalic phase of gastric motility, signals from smell & taste receptors reach brain; results in vagus nerve increase stomach motility
during gastric phase of gastric motility, distention of stomach w/food
both neural stimulation & gastrin increase stomach motility
intestinal phase of gastric motility distention of duodenum w/chyme decreased stomach motility
stomach __ 4 hours after a meal empties
as chyme enters the duodenum, receptors respond to stretch- neural reflex
fatty, acidic chyme- (by hormones & neural reflexes) chyme contents
decrease stomach motility & gastric emptying (and further duodenal filling) chyme
major organ of digestion/absorption; 20 ft long from pyloric sphincter- ileocecal valve stomach
10"; ‘C’ shaped & is retroperitoneal; bile duct & pancreatic duct open here; entry is controlled by the sphincter of Oddi duodenum
8" long; suspended from posterior abdominal wall by mesentery jejunum
12"; joins large intestine at ileocecal valve; suspended from posterior abdominal wall by mesentery ileum
structural modifications increase surface area for nutrient absorption circular folds, villi, & microvilli
1cm tall; folds of mucosa & submucosa circular folds
circular folds also called plicae circulares
finger-like extensions of the mucosa villi
projections of plasma membrane of absorptive cells ((brush border) microvilli
microvilli contain __ __ enzymes, only found in small intestines; responsible for "fine-tuning" brush border
largest gland in body; right, left, caudate, & quadrate lobes; contains falciform ligament liver
separates the (larger) right & (smaller) left lobes falciform ligament
falciform ligament attaches liver to anterior abdominal wall
hexagonal units; composed of plates of liver cells liver lobules
liver lobules filter & process nutrient-rich blood
liver lobules contain __, which are leaky capillaries btwn plates of hepatocytes that contain macrophages sinusoids
process nutrients reaching them through portal blood; store glucose as glycogen hepatocytes
hepatocytes use __ __ to form plasma proteins amino acids
hepatocytes store __ vitamins fat-soluble
hepatocytes detoxify by converting ammonia to urea
hepatocytes __ bile secrete
liver produces 500- 1000 ml __ which is conveyed to the duodenum bile/day
yellow-green solution; contains bile salts, bilirubin, & cholesterol bile
cholesterol derivatives that function in fat emulsification & absorption bile salts
pigment formed from destruction of red blood cells bilirubin
triglycerides & phospholipids in bile cholesterol
most bile salts are reabsorbed & recycled
most of bilirubin is lost in feces
stores & concentrates bile, by absorbing its water & ions gall bladder
when gall bladder muscle wall contracts it releases bile into its cystic duct, then flows into bile duct
acidic, fatty chyme causes duodenum to release cholecystokinin (CCK)
cholecystokinin (CCK) causes __ of gall bladder contraction
cholecystokinin (CCK) causes sphincter of Oddi to relax
result of cholecystokinin (CCK) release by gall bladder, bile enters into duodenum
pancreatic acini secretes pancreatic juice which breaks down all categories of foodstuff exocrine function of pancreas
release of insulin & glucagon by cells in islets of Langerhans endocrine function of pancreas
watery bicarbonate rich fluid containing enzymes (trypsinogen, chymotrypsin amylase, lipase) pancreatic juice
activated in the duodenum to trypsin trypsinogen
neutralizes acid chyme & provides optimal environment for pancreatic enzymes HCO3
when fatty/acidic chyme enters duodenum secretin & CCK are released, which then induce secretion of pancreatic juice
Vagal stimulation also stimulates release of __ & __ by duodenum secretin & CCK
as chyme enters duodenum carbohydrates & proteins are only partially digested
no fat digestion has taken place as chyme enters duodenum
digestion is __ in small intestine completed
all __ absorption takes place in small intestine nutrient
most of __ __ takes place in small intestine water absorption
delivered from liver & pancreas to small intestines bile, enzymes, & bicarbonate ions
optimal pH required for __ activity in small intestines enzyme
intestinal juice secreted by intestinal glands is __ __ enzyme poor
intestinal juice secreted by intestinal glands is __ __ with some mucous mostly water
mix chyme w/bile, pancreatic & intestinal juices, & move food residues through ileocecal valve into large intestine small intestine movements
most common motion of small intestine in which chyme moves backwards & forwards segmentation
during segmentation, chyme is mixed and brought it in contact with intestinal epithelium for absorption
because segmentation allows slow movement of chyme towards ileocecal valve it allows enough time for digestion & absorption
begins with each wave starting distal to previous; meal residue, bacteria, mucosal cells & debris are moved into large intestine via peristalsis after digestion in small intestines
function is to absorb remaining water & some electrolytes from food residue & to eliminate residue as feces large intestine
3 bands of longitudinal smooth muscle in large intestine muscularis teniae coli
pocket-like sacs caused by tone of teniae coli haustra
fat-filled pouches of visceral peritoneum epiploic appendages
teniae coli, haustra, & epiploic appendages are unique features of large intestines
large intestine is subdivided into cecum, appendix, colon, rectum, & anal canal
ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, & sigmoid colon distinct regions of colon
portions of colon that are anchored via mesenteries called mesocolons transverse & sigmoid
potion of colon that joins rectum sigmoid
last segment of large intestine that opens to exterior at anus anal canal
anal sphincter composed of smooth muscle internal
anal sphincter composed of skeletal muscle external
anal sphincters are __ except during defecation closed
consist of bacteria surviving small intestine that enter cecum, & those entering via anus bacterial flora of large intestine
bacterial flora of large intestine serve, without harming host, to __ __ __ ferment indigestible carbohydrates
bacterial flora of large intestine serve, without harming host, to release irritating acids & gases (flatus)
bacterial flora of large intestine serve, without harming host, to synthesize B complex vitamins & vitamin K
when __ __ is present colon becomes motile food residue
slow short lived movements of haustra occur one after another that move contents of colon segmentations
during segmentations __ & __ is absorbed water; salt
stronger & occur after eating; presence of food in stomach initiates reflex mass peristalsis
mass peristalsis force feces toward rectum
feces are forced into rectum by mass movements of colon
stretching of rectal walls by feces initiates defecation reflex
defecation reflex stimulates contraction of rectal walls
defecation reflex relaxes internal anal sphincter
defecation reflex contracts external sphincter initially
stimulate relaxation of external anal sphincter & defecation occurs under voluntary signals/conscious controls
salivary amylase, pancreatic amylase, & intestinal brush border enzymes are used to break down carbohydrates
chemical digestion of starch; begins in mouth; breaks it down into 2-8 glucose units salivary amylase
continues starch digestion, after salivary amylase pancreatic amylase
convert disaccharides to monosaccharides brush border enzymes
digests protein into polypeptides & a small number of amino acids, in stomach pepsin
break up proteins into smaller peptides, in small intestine; pancreatic enzyme trypsin & chymotrypsin
release free amino acids brush border peptidases
small intestine is sole site of fat digestion brought about by pancreatic lipases
emulsify large fat globules into tiny small droplets of fat which can easily be acted upon by lipases bile salts
bile salts convert triglycerides to free fatty acids & monoglycerides
most absorption is complete by time chyme reaches ileum
amino acids & glucose are absorbed through mucosa of intestinal villi by active transport
amino acids & glucose enter __ __ in intestinal villus & are ultimately transported to __ __ blood capillary blood; hepatic portal
fats digestion products are absorbed by __ & enter blood through __ diffusion; lacteals
lymphatic capillaries lacteals
bile salts are also needed for fat absorption
products of fat digestion associate w/bile salts to form very small __ which can come into close contact with epithelial cell surfaces micelles
lipid substances leave micelles & enter intestinal cells via diffusion
microscopic particles of emulsified fat found in the blood and lymph and formed during the digestion of fats chylomicrons
chylomicrons leave epithelial cells, in small intestines, enter __, & are transported to circulation via __ lacteals; lymph
chief cell is digestive system cell that produces an inactive enzyme
islet cell is digestive system cell that makes hormones
paneth cell is digestive system cells that produces lysozyme
parietal cell is digestive system cells that makes intrinsic factor
Kupffer cell is digestive system cells that is phagocytic
ingestion is taking food into the digestive system
mechanical digestion is chewing, mixing, churning, & segmentation of food
chemical digestion is enzymatic degradation of foodstuffs into simpler molecules
absorption is passage of digested materials from lumen of GI tract into blood/lymph
defecation is elimination of indigestible food stuffs
mucosa is in __ __ w/ingested food direct contact
submucosa is __ __ with many elastic fibers dense CT
muscularis is composed of longitudinal & circular layer of __ __ smooth muscle
serosa is same structure as __ __ visceral peritoneum
paratoid gland is large salivary gland lying behind ear
sublingual gland is salivary gland below tongue
submandibular gland is smaller salivary gland located under jaw
lingual frenulum secures tongue to floor of oral cavity
rugae are folds of mucosal layer
pyloric sphincter is located at inferior end & controls stomach emptying
gastroesophogeal sphincter lies at superior end & regulated movement of food from esophagus
body of stomach is able to stretch & hold large amounts of food
cephalic phase is stimulated by sight/smell of food
gastric phase is stimulated by distention of stomach & low acidity
intestinal phase is stimulate by partially digested proteins & fats
inhibits gastric gland secretions secretin
increases the secretions of enzyme rich pancreatic juice CCK
stimulated by partially digested proteins in the stomach and increases gastric gland secretions gastrin
inhibits gastric gland secretions; released in response to presence of fatty chyme in the small intestine GIP
contains openings for bile and pancreatic ducts duodenum
deep permanent folds of the mucosa and submucosa plicae circulars
contains valve that connects to large intestines ileum
finger-like projections of the mucosa villi
AKA brush border microvilli
most is ingested in the form of starch carbohydrates
triglycerides are the most common in diet lipids
built of long chains of amino acids proteins
made up of ribose/deoxyribose sugars & nitrogenous bases nucleic acids
begins carbohydrate digestion in the mouth salivary amylase
digests proteins in small intestines trypsin
emulsifies fats for digestion bile
brush border enzyme that act on disaccharides sucrase, lactase, maltase
in order to prevent self-digestion of the pancreas, activation of pancreatic proteases occurs in duodenum
during deglutition, bolus passes into stomach from esophagus through gastroesophageal sphincter
during the intestinal phase of gastric regulation stomach is initially stimulated and later inhibited
protective collections of lymphocytes and macrophages occur in Peyer's patches
proteins are main organic molecule digested in the stomach
peristalsis propulsive function that occurs in the esophagus
characteristic of the large intestine contains a large number of bacteria
gastrin regulatory chemical stimulates gastric gland activity and motility
layering of the wall of the GI tract, starting from the layer next to the lumen mucosa, submucosa, muscularis externa, serosa
hepatopancreatic ampulla is formed from the union of bile duct and main pancreatic duct
effect of stripping the small intestines of their villi decreased surface area for absorption would cause weight loss to occur
stomach produces HCl & intrinsic factor
final product of carbohydrate digestion monosaccharides
short reflexes in the digestive system are stimulated by enteric plexus
most common cause of peritonitis burst appendix
myxovirus causes mumps
increased activity of anaerobic bacterial activity at the back of the tongue causes halitosis
condition directly associated with an increased risk for heart disease and stroke periodontitis
only stomach function that is essential to life is secretion of intrinsic factor
phase of gastric secretion is considered a conditioned reflex cephalic
hollow organs, like the stomach, that act as reservoirs exhibit plasticity
many of the early food allergies seen in infants are caused by absorption of whole proteins
condition that affects the large bowel and has no physiological or anatomical cause irritable bowel
bile is a(n) emulsifying agent
defecation is mediated by sympathetic spinal cord reflex
three excitatory gastric hormones gastrin, serotonin, histamine
stomach produces serotonin and histamine to __ smooth muscle contraction regulate
triads have a branch of hepatic artery & portal vein, and bile duct
begins in the stomach under the action of pepsin protein digestion
pancreas does NOT have a serosa layer, making it retroperitoneal
pyloric sphincter regulates passage of __ from the stomach into the duodenum chyme
absorbed into lymphatic lacteals digested fats
myenteric plexus controls motility of digestive tract
continuous hollow tube extending from the mouth to the anus; its walls are constructed by the oral cavity, pharynx, esophagus, stomach, and small and large intestines alimentary canal/GI tract
oblique layer allows stomach to churn/mix food, reducing into smaller pieces modification of muscularis externa
muscularis externa differs from that of other GI organs in that it has three layers of smooth muscle instead of two
nonkeratinized stratified squamous epithelium transitions to simple columnar epithelium at gastroesophageal junction
non keratinized stratified squamous epithelium of esophagus relates to its function in that it is abrasive resistant
simple columnar epithelium of stomach relates to its function in that it is specialized for secretion
differentiation of colon from large intestine, is that colon is where food exits after passing through large intestine
structure that suspends small intestine from posterior body mesentery
villi are finger-like extensions of intestinal mucosa that increase surface area for absorption
Peyer's patches are large collections of lymphoid tissue found in submucosa of small intestine
circular folds are deep folds of mucosa & submucosa that extend completely/partially around circumference of small intestine
stomach & oral cavity are regions that break down foodstuffs mechanically
pharynx is conduit for both air & food
lesser/greater omentum & mesentery are structures continuous w/and representing modifications of peritoneum
esophagus/gullet has no digestive/absorptive function
rugae are folds of gastric mucosa
haustra are sacculations of large intestine
microvilli are projections of plasma membrane of a mucosal epithelial cell
ileocecal valve at junction of small/large intestine
small intestine is primary region of food/water absorption
frenulum is membrane securing tongue to floor of mouth
large intestine absorbs water & forms feces
vestibule is area btwn teeth & lips/cheeks
appendix is worm-like sac that out-pockets from cecum
stomach initiates protein digestion
lesser omentum is structure attached to lesser curvature of stomach
small intestine is organ distal to stomach
pyloric valve controlling food movement from stomach to duodenum
soft palate is posterosuperior boundary of oral cavity
small intestine/duodenum is location of hepatopancreatic sphincter through which pancreatic secretions & bile pass
parietal peritoneum is serous lining of abdominal cavity wall
large intestine is principal site for synthesis of Vit K by microorganisms
anus is region containing 2 sphincters through which feces are expelled from body
hard palate is bone-supported anterosuperior boundary of oral cavity
visible portion of tooth in situ clinical crown
material covering tooth root dentin
hardest substance in body enamel
periodontal ligament attaches tooth to bone & surrounding alveolar structures
root portion of tooth embedded in bone
cementum forms major portion of tooth structure; similar to bone
odontoblast produces dentin
pulp site of blood vessels, nerves, & lymphatics
anatomical crown entire portion of tooth covered w/enamel
produces mucus; found in submucosa of small intestine gastric glands
produces product containing amylase that begins starch breakdown in mouth salivary glands
produces whole spectrum of enzymes & alkaline fluid that is secreted into duodenum pancreas
produces bile that secrete into duodenum via bile duct liver
produces HCl & pepsinogen intestinal crypts
found in mucosa of small intestine; produces intestinal juice duodenal glands
paratoid secretions are mainly serous
role of gallbladder is to store & concentrate bile
hepatic artery, portal vein, & common bile duct are three structures always found in portal triad regions of liver
Kupffer cells are found on lining of sinusoids in liver
Kupffer cells functions is to remove debris from blood
liver is dark red in living animal because this is where hemoglobin from dead RBCs are broken down & recycled
secretory cells of pancreas that serve digestive process acinar cells
Created by: lfrancois



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