Chapter 23 Digestive System Flashcards
what is the difference between the alimentary canal and the accessory organs?
alimentary canal is the site of actual food passing through and nutrients being absorbed
accessory organs will not have food passing directly through, but still aid in digestion
what are the 6 organs of the alimentary canal in order?
mouth
pharynx
esophagus
stomach
small intestine
large intestine
how long is the entire alimentary canal if relaxed
30 feet
what are 6 accessory organs that assist in digestion?
salivary glands
teeth
tongue
liver
gallbladder
pancreas
describe what happens to food during ingestion
physically taking food into digestive tract via mouth
describe what happens to food during propulsion
peristalsis allows food to propel towards anus
describe the directional movement of peristalsis
waves of coordinated smooth muscle contractions leading only towards anus
describe what happens to food during mechanical digestion
physical forces break food apart
can either be from chewing or segmentation
what is another word for chewing?
mastication
describe the movement of food in segmentation
alternating contractions of nonadjacent segments allowing food to move back and forth to mix with digestive juices
describe what happens to food during chemical digestion
chemicals break down macromolecules
what are the types of chemicals used in chemical digestion
nonspecific - attacks all kinds of organic food molecules
specific - attack specific type of organic molecules
name an example of a nonspecific chemical used in chemical digestion
acid in our stomach
what do carbohydrates get broken down into?
sugar/ monosaccharides
what do proteins get broken down into?
amino acids
what do fats get broken down into?
fatty acids
describe what happens to food during absorption
intake of nutrients occur
describe what happens to food during defecation
elimination of indigestible substances through feces
what are the nutrients that get absorbed?
digested food molecules
vitamins
minerals
water
what are the four layers of the alimentary canal walls in order of inner to outer layers
mucosa
submucosa
muscularis externa
serosa
what are the three layers found within the mucosa?
epithelium
lamina propria
muscularis mucosae
what is the function of the mucosa?
secretion of mucus, enzymes, and hormones
absorption of nutrients
protection from pathogens
what is the structure/function of the epithelium within the mucosa?
simple columnar epithelium: secretion, absorption, protection
contains goblet cells: aids in secretion
what is the function of goblet cells?
exocrine glands that secrete mucus into the lumen of the alimentary canal
what is the structure/ function of the lamina propria of the mucosal layer?
loose areolar connective tissue
contains blood vessels: to deliver and collect nutrients
contains lacteals: for fat transport
contains immune cells: for immune surveillance
what is the structure/ function of the muscularis mucosae?
thin layer of smooth muscle responsible for SMALL local movements
what is the structure/function of the submucosa?
irregular connective tissue
contains blood vessels, nerves and lymphatic vessels
contains intrinsic submucosal nerve plexus to regulate glands and muscularis mucosae
what is the structure of the muscularis externa?
contains 2 layers of smooth muscle
-inner circular layer
-outer longitudinal layer
what is the function of the muscularis externa? what allows for this function?
responsible for big movements such as peristalsis and segmentation
intrinsic myenteric nerve plexus between 2 layers of smooth muscle
what is the function of the serosa?
protect and connect
what is the structure of the serosa?
2 layers
-inner areolar connective tissue
-outer simple squamous “mesothelium”
what is another name for serosa?
visceral peritoneum
what are the layers of the peritoneum?
parietal peritoneum (lines body wall)
visceral peritoneum (lines organs)
what is the structure of mesentery?
layer of peritoneum attaching some organs to the abdominal wall
what is the function of the mesentery?
route for vessels and nerves
hold organs in place
stores fat
what is the difference between intraperitoneal organs and retroperitoneal organs?
intraperitoneal - are suspended from the abdominal wall by a mesentery
retroperitoneal - are attached directly to the abdominal wall
what is the benefit of the organs being intraperitoneal?
it allows for freedom of movement during digestion
what are examples of intraperitoneal organs?
stomach
jejunum
ileum
transverse colon
sigmoid colon
what is the benefit of the organs being retroperitoneal?
organs cannot be hypermobile and twist and knot themselves
what are the examples of retroperitoneal organs?
duodenum
liver
pancreas
ascending colon
descending colon
when did retroperitoneal organs lose their original mesentery?
during fetal development
what is the structure/function of the oral cavity?
struct: is continuous with oropharynx
funct: only site of ingestion
what is the top and bottom lip called?
labium superious oris
labium inferius oris
where does our upper lip begin? our bottom lip?
bottom border of nose
border of chin
what is the red/pinkish part of our lips called?
vermillion of the lips
what tissue is the vermillion composed of?
nonkeratinized stratified squamous epithelium
what is the labial frenulum? how many do we have?
flap of tissue connecting lips to gums
2: superior and inferior labial frenulum
what is the only skeletal muscle we have that has only one attachment point called?
the tongue
what is the lingual frenulum?
connects tongue to floor of oral cavity
what is the function of the tongue?
licking, tasting, food bolus formation
what is a bolus?
chewed up food
what was wrong with sawa’s lingual frenulum?
it was shorter than normal (she had a tongue-tie)
what are the four types of papillae called
filiform papillae
fungiform papillae
vallate papillae
foliate papillae
what is the structure/function of the filiform papillae?
conical in shape
contains keratin (white)
roughens surface to be able to lick semisolids
what is the structure/function of the fungiform papillae?
round (like a mushroom)
houses taste buds for tasting
where are filiform and fungiform papillae found?
anterior surface of tongue
which papillae is most abundant?
filiform papillae
what is the structure/function of vallate papillae?
V-shape
“wall” between body and root of tongue
houses taste buds for tasting
where is the location of vallate papillae?
back of tongue
what is the structure and location of the foliate papillae?
ridges on lateral sides of posterior tongue
what is the function of foliate papillae?
house taste buds BUT only in use during infancy and early childhood
what are the taste bud containing papillae?
fungiform
vallate
foliate (but only active in childhood)
what are the 2 types of salivary glands?
extrinsic salivary glands
buccal (intrinsic) salivary glands
which Type of salivary gland produces the most saliva?
extrinsic salivary glands
where are extrinsic salivary glands located? how many are there?
outside oral cavity
3 main pairs
where are buccal salivary glands located? what is their size in comparison to extrinsic?
inside oral cavity mucosa
smaller
what are the four functions of saliva?
- dissolves food which allows for tasting
- cleans mouth (innate immunity)
- lubricates for swallowing
- contains enzymes which begin chemical digestion
Is saliva hypertonic or hypotonic?
99% water, making it hypotonic
what protective proteins are found in saliva?
IgA
lysozyme
what digestive proteins are found in saliva?
mucin
alpha amylase
lingual lipase
what is the function of alpha amylase in our saliva
break down carbohydrates
what is the function of lingual lipase in our saliva?
break down fats
what is the function of mucin in our saliva?
protein that makes mucus allowing for lubrication
how much saliva do we make?
1 liter of saliva per day
which nervous system is responsible for activation of parotid glands?
parasympathetic nervous system
what are the factors that increase saliva production?
sensory input (seeing/smelling food)
chemoreceptors in mouth
mechanoreceptors in mouth
what is xerostomia?
dry mouth
what causes xerostomia?
activation of sympathetic nervous system
dehydration
what is halitosis?
bad breath
what does xerostomia cause?
increased cavities
difficulty talking and swallowing
slow food digestion
what is the function of teeth?
mechanical digestion
mastication
what are the three main parts of a tooth?
crown (exposed part of tooth)
neck
root (embedded in jaw)
what are the three layers of the teeth?
enamel
dentin
cementum
which layer of teeth is the hardest?
enamel
can enamel be replaced?
no
what is the structure/function of cementum?
calcified connective tissue
covers entire root
helps to anchor tooth inside socket
what is the structure/ function of dentin?
bone-like material (not as hard as enamel)
surrounds pulp cavity
can new dentin be made?
yes
what is within the pulp cavity?
blood vessels and nerves
Without sufficient, saliva mouth won’t be washed out, allowing for bacteria to accumulate causing cavities
how is a bolus formed?
tongue mixes chewed up food and saliva
what is another word for swallowing?
deglutition
how is the bolus swallowed?
2 phases
- buccal phase
- pharyngeal-esophageal phase
which phase of deglutition is voluntary? involuntary?
buccal
pharyngeal-esophageal
what is involved within the buccal phase of deglutition?
tongue forces food through isthmus of the fauces
what is involved within the pharyngeal-esophageal phase of deglutition?
peristalsis pushing food toward stomach
describe the structure of the types of muscle found in the esophagus?
1/3 skeletal muscle
1/3 skeletal and smooth muscle
1/3 smooth muscle
what is the function of the esophagus?
transport food from the pharynx to the stomach via peristalsis
what is the function of the two esophageal spincters?
upper and lower keep stomach acid out of pharynx
also keep air out of stomach
what is the esophageal hiatus?
gap in diaphragm where esophagus enters abdominal cavity
what does GERD stand for?
gastroesophageal reflux disease
what is gastroesophageal reflux disease?
Open lower esophageal sphincter allows acid reflux causing inflammation of esophagus
what can extreme GERD cause?
Barrett’s disease
what are symptoms of Barrett’s disease?
hardening of esophagus
cancer
bad breath (acid rots teeth)
what is a sliding hiatal hernia?
stomach is forced up into thoracic cavity through the esophageal hiatus which raises the lower esophageal sphincter above the diaphragm disabling it from closing well
what is a common cause of sliding hiatal hernia?
late pregnancy
what is Schatzki’s rings?
rings of fibrous connective tissue surrounding esophagus
prevents stretching causing bolus to get stuck
what is the cause of Schatzki’s rings? treatment?
inherited in families
eat smaller bites
what is the function of the stomach?
expandable site of food storage
mechanical and chemical digestion
what allows the stomach to expand? how much?
rugae
50 to 4000 ml
what structures in the stomach allow for mechanical digestion and the production of chyme?
3 layers of smooth muscle mix food with gastric juices producing chyme
what directions do the 3 layers of smooth muscle within the stomach go?
longitudinal, circular, and oblique
how does peristalsis occur in the stomach to aid in mechanical digestion?
3 times per minute, waves push food toward pylorus
grinding then occurs near pylorus (stronger contractions)
retropulsion occurs causing small particles to squirt into duodenum past slightly open pyloric valve
what is emesis?
vomiting
what controls emesis?
emetic center in the medulla oblongata
what causes emesis?
extreme stretch
bacterial toxins
excessive alcohol
what are bezoars?
mass of indigestible material too big (>2 inches) to pass through pylorus
what are causes of bezoars?
hair
gum
seeds
plant fibers
medications
what are the four cells of the gastric gland?
Chief cells
parietal cells
enteroendocrine cells
stem cell (mucous neck cells)
what is the function of chief cells?
secrete pepsinogen
pepsinogen then travels up gastric gland and out of gastric pit and pepsin is formed when pepsinogen is exposed to low pH of stomach acid
what is the function of pepsinogen?
turns into pepsin which is a protease (an enzyme that breaks down protein)
which is the parietal cell?
the blue
what is the function of parietal cells? How does its appearance help with its function?
produce HCl
has unique curves covered in microvilli which creates a large surface area for HCl secretion
how do parietal cells form HCl? include the reaction
CO2 is produced by mitochondria in parietal cell
uses carbonic anhydrase as the catalyst to produce carbonic acid
bicarbonate moves into blood vessel while chloride moves into parietal cell
hydrogen ion combines with chloride to for hydrochloric acid which is excreted out the gastric gland and gastric pit
what is the function of enteroendocrine cells?
secrete chemical signals to regulate digestion (histamine and acetylcholine)
what is the function of mucus neck cells?
stem cells which replace dead cells
how often is the entire surface of stomach replaced by mucous neck cells?
3-6 days
what are the functions of low pH in stomach?
activate pepsinogen
break down organic material and microbes
aids in iron absorption
how does enteroendocrine cells aid parietal cells to do its job in producing HCl?
enteroendocrine release histamine and acetylcholine which bind to parietal cells in order to regulate them
how does pepsid and zantac aid in the decrease acid production?
they are antagonists to histamine receptors to the parietal cells so the parietal cells never get triggered to release pepsinogen
how does Prilosec and Prevacid aid in being an antacid?
they are proton pump inhibitors which slow H+ release
what are the cells of the rest of the stomach? function?
mucus cells
secrete mucus
how do mucus cells protect us?
outer layer of mucus is viscous and traps particles
inner layer of mucus is alkaline witch protects against stomach acid
what are the two causes of stomach ulcers?
99% caused by Helicobacter pylori
1% caused by NSAIDS
what is a stomach ulcer?
erosions of stomach wall caused by loss of protective mucus which allows stomach acid to eat away at stomach wall
Most microbes die in the stomach, why is Helicobacter pylori able to survive? what do they do when they arrive?
they use their flagella and unique shape to burrow in the mucus layer which is protective to them from the stomach acid.
they then break down the mucus layer which is what causes the capability for an ulcer to form
stomach is lined with mucus cells which secrete mucus to form the protective mucus layer
where is the location of the pancreas?
deep to greater curvature of stomach
head is nestled in curvature of duodenum of small intestine
what is the function of the pancreas?
produce pancreatic juice which neutralizes HCl from stomach and contains enzymes for chemical digestion of proteins, lipids, carbohydrates, and nucleic acids
what are examples of the enzymes found in pancreatic juice?
protein digestion: proteases such as Trypsin, Carboxypeptidase, and Chymotrypsin
carbohydrate digestion: amylase
nucleic acid digestion: nucleases
lipid digestion: lipases and phospholipases
how does pancreatic juice neutralize HCl?
it is hypotonic with bicarbonate as its main electrolyte
bicarbonate is basic which neutralizes HCl
what is the location of the liver?
inferior to diaphragm
located in most of right hypochondriac and epigastric abdominal regions
what duct does the pancreas use to transport juices to small intestine?
pancreatic duct
what ducts does liver use to transport bile to small intestine?
leaves common hepatic duct, then bile duct, then enters small intestine. If sphincter to small intestine is closed, bile travels back up trough bile duct to cystic duct to gallbladder
how is it that bile emulsifies fat?
bile salts break fats into small droplets which increases access for lipase to digest fats. fats are then absorbed and transported into lacteals
bilirubin is found in kidneys, where does it come from?
heme from hemoglobin
what color is bilirubin?
yellow
how is bilirubin processed to turn into urobilinogen?
conjugated bilirubin is metabolized in small intestine into urobilinogen which is reabsorbed by kidneys and is then excreted in urine (giving it its yellow color)
how is bilirubin processed into stercobilin?
conjugated bilirubin is metabolized in small intestine into urobilinogen. then is metabolized further into stercobilin which turns feces brown
what is the location of gallbladder?
deep to right lobe of liver
what is the size of a gallbladder?
kiwi
what is the function of the gallbladder?
store and concentrate bile (10x more concentrated than from liver)
contracts to release bile as needed
why is it that we can live without gallbladder?
liver continuously releases dilute bile (but would make it difficult to digest fatty meals)
what are gallstones?
crystallized bile salts which can block ducts and prevent the release of bile
what symptoms can having gallstones cause? how?
jaundice - because bilirubin accumulates
gray feces - gray because of lack of stercobilin from bilirubin
fatty streaks in feces - fatty deposits from being unable to fully digest
what are the three sections of the small intestine?
duodenum
jejunum
ileum
what is the function of small intestine?
chemical digestion is completed
nutrients absorbed
waste is pushed into large intestine
what happens to chyme in each of the sections of small intestine?
segmentation (if there are a lot of nutrients present)
once absorption is over (nutrients decrease) peristalsis occurs (MMC)
what is MMC?
migrating motor complex - peristalsis that occurs specifically in small intestine
what initiates MMC? how often?
initiated by duodenum every 90-120 minutes
primarily, where does digestion mostly occur?
within duodenum
what are brush boarder enzymes?
enzymes coming from small intestine that aid in chemical digestion
after enzymes, like pancreatic amylase, break down macromolecules, like starch, what further breaks those subunits down?
pancreatic amylase breaks down starch into maltose disaccharides. brush boarder enzymes like maltase, then further break down maltose molecules and allows for them to be absorbed through epithelial cells of small intestine
what are all the types of brush boarder enzymes found and their general function?
enteropeptidase - activates pancreatic proteases (like amylase)
lactase, maltase, trehalase - carbohydrate digestion
why is brush boarder cells called “brush boarder”?
looks velvety like a paint brush
where does absorption mostly occur?
jejunum
how is it that the structure of small intestine, increases absorption?
circular folds that then contain many villi which then contain multiple microvilli
what is another name for circular folds in small intestine?
plicae circulares
how deep does the circular folds go?
mucosa and submucosa layers
how deep do the villi go? what tissue is it made of
folds of the mucosa (not submucosa)
how tall is each villi?
1 mm
(is visible)
what does each villi contain?
capillary beds and lacteals
what tissue is microvilli?
projections of plasma membrane (is microscopic)
many located on each individual enterocyte
where are brush boarder cells specifically located?
on each individual microvilli
how do enterocytes of brush boarder absorb nutrients?
they only absorb the smallest nutrients (digested brush boarder enzymes) through their apical side and leave basolateral side to capillary beds
what are examples of the smallest nutrients able to be absorbed by enterocytes?
amino acids
monosaccharides
fatty acids
nucleotides
what is the purpose of chylomicrons?
transport lipids (fatty acids/cholesterol)
what are the names of three types of chylomicrons we discussed in class?
VLDL
LDL
HDL
which is good/bad cholesterol?
bad: LDL
good: HDL
what is VLDL, LDL, and HDL stand for?
very low density lipids (full of fat)
low density lipids
high density lipids (contain mostly protein/ not much fat)
the weight loss drug Alli works by preventing lipase from digesting fats. Do you think people who are taking Alli will have more VLDLs or more HDLs than average. Explain your logic
how long does Migrating motor complex take to use peristalsis through duodenum and jejunum to get to ilium?
2 hours
how does bariatric surgery allow for weight loss?
stomach is bypassed which means smaller portions of food are required to be consumed. (stomach is normally a temporary reservoir for food)
besides stomach, what else is bypassed in bariatric surgery that allows for weight loss?
duodenum is bypassed = less chemical digestion = less absorption
name the main function of the large intestine
absorb water and electrolytes
how do microbiota in large intestine aid us?
digest remaining material
produce vitamins
release gas
how long does waste take to move through large intestine?
12 hrs
why is large intestine not necessary for life? why does it make our life easier?
most nutrients have already been absorbed
we would be dehydrated without it/
it acts as a reservoir until defecation. defecation would be immediate without it
what is the teniae coli of the large intestine?
line that runs down middle of large intestine (Longitudinal layer of muscularis reduced to three bands of smooth muscle)
what is the haustra of the large intestine?
pouches of large intestine
formed by contraction of teniae coli
keep food from sliding backwards
what are the epiploic appendages of the large intestine
fat filled pouches of visceral peritoneum that serve no function
where is the cecum?
Nestled in right iliac fossa
Below ileocecal valve
name all the names of the colon
ascending colon
transverse colon
descending colon
sigmoid colon
what is hanging off the cecum?
vermiform appendix
how does inflammation of appendix occur?
bacteria filling appendix
what are flexures of the colon?
bends in colon:
hepatic flexure
splenic flexure
what is the function of the rectal valves?
located in the rectum - to separate feces from flatulence
what happens when rectal valves fail?
sharting
what is a digital rectal exam?
palpate (feel around) abdominal organs
what is the function of the anal sinuses?
excrete mucus when stretched (by feces)
what are the two sphincters that guard the anus?
internal (smooth muscle/involuntary)
external (skeletal muscle/voluntary)
what digestive processes occur within the pharynx and esophagus
propulsion by peristalsis
what is the hole in the diaphragm that the esophagus drops through?
esophageal hiatus
what digestive processes occur within the stomach
chemical and mechanical digestion
secretion of stomach acid by gastric gland
what is responsible for chemical digestion within the stomach
pepsin and HCl
what is ileal break triggered by?
high nutrient content in ileum
what is the effect of ileal break reflex?
slow contractions in stomach, duodenum, jejunum, and ileum
triggers feelings of satiety in CNS
what is the defectation reflex triggered by?
feces in rectum
what is the effect of the defecation reflex?
contraction of sigmoidal colon and rectum
opening of internal anal sphincter
closing exterior anal sphincter (until voluntarily opened)
what is the sampling reflex triggered by?
flatulence and feces in rectum
what is the effect of the sampling reflex?
internal anal sphincter relaxes
allows passage of gas but not feces
how often does the sampling reflex occur?
4x per hour
what triggers gastrocolic reflex?
presence of high nutrients in stomach and small intestine
what is the effect of gastrocolic reflex?
increase large intestine motility (need to poop)
signals travel via Vagus nerve
what stimulates the release of gastrin?
response to presence of protein in pyloric region
what effect does gastrin have?
stimulates acid release
stimulates pepsinogen release
stimulates gastric emptying
what stimulates the release of motilin?
in response to fasting
what effect does motilin have?
stimulates migrating motility complex (MMCs)
MMCs are initiated in the proximal duodenum causing peristalsis waves
what makes the hormone gastrin?
enteroendocrine cells in pyloric region (g cells)
what makes the hormone motilin?
m cells in duodenal mucosa
what makes the hormone cholecystokinin (CCK)
i cells in duodenum
what triggers cholecystokinin (CCK)?
in response to proteins and fats in duodenum
what effect does CCK have?
pancreas to secrete
gallbladder to contract
slows stomach emptying
