Pt 1 of Test 3 Flashcards
What are the main steps in the digestive process
- ingestion
- digestion
- absorption
- elimination
what is the main point in the digestive process
movement. food must be moved along the G.I. tract in order to fulfill all functions. (food must be first broken down)
explain the muscularity of the G.I. tract
highly muscular allowing to propel food stuff
what is ingestion
intake of food via the mouth
what is digestion
mechanically or chemically breaking down foods into their subunits
what would be an example of chemically digesting food into their subunits
by enzymes such as hydrolysis which is enzymatic break down using water (complex to simple)
what is absorption
movement of nutrients across the GI tract wall to be delivered to cells via blood (absorbing nutrients across membranes into bloodstream)
where does absorption mainly take place
jejunum of SMALL INTESTINE
what is elimination
removal of indigestible molecules (compaction and defecation- feces)
where does elimination usually occur
large intestine and anus
what is peristalsis
wave-like movement that propels food stuffs from one place to the next (rhythmic)
what is mechanical digestion
physical breakdown of food into smaller particles (mainly in mouth)
what are the ways to digest mechanically
cutting/grinding of teeth
churning action of stomach/small intestines
exposing more food surface to action of digestive enzymes
what does mechanical digestion do for the surface area of food stuff
increases it when bringing in to facilitate for chemical digestion and to be acted on by those enzymes
what is chemical digestion
a series of hydrolysis reactions that breaks dietary macromolecules into their monomers (residues). conducted by enzymes
how is chemical digestion carried out
by digestive enzymes produced by salivary glands, stomach, pancreas, and SMALL INTESTINE (starts in mouth, works in stomach, almost entirely done by small intestine)
what are the results of chemical digestion
polysaccharides into monosaccharides
proteins into amino acids
fats into monoglycerides and fatty acids
nucleic acids into nucleotides
do all nutrients have to be broken down?
no. some nutrients are present in a usable form in ingested food. they can be absorbed without being digested. Small things like vitamins, free amino acids, cholesterol, water
what are the 2 groups of organs in the digestive system
- alimentary canal
- accessory digestive organs
what does the alimentary canal do and what does it consist of
GI tract. mouth to anus. digests food and absorbs fragments. mouth, pharynx, esophagus, stomach, small intestine, and large intestine
what are accessory digestive organs
teeth, tongue, gallbladder
digestive glands
salivary glands
liver
pancreas
most material in the body is considered
external to the body until it is absorbed by the epithelial cells of the alimentary canal. (so basically defecated food residue was never in the body)
what is the alimentary canal order
- mouth
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
- rectum
- anus
what is the enteric nervous system
a quasi-autonomic nervous network in the esophagus, stomach, and intestines that regulate digestive tract motility, secretion, and blood flow (self regulating)
where does peristalsis mainly occur
esophagus (pushes to stomach)
what is the main thing the small intestine does
chemical digestion (enzymes) and absorption takes place
what is the main thing the large intestine does
removes water fro materials and absorbs it and salt to form feces
what is the main thing the rectum does
final storage area. dries out and becomes fecal matter. elimination
what is the main thing the anus does
where elimination occurs
what are the 4 layers of the GI tract
- mucosa- innermost lining
- submucosa- 2nd
- muscularis- 3rd
- serosa- outermost
what does the mucosa layer do
produces mucus to protect the lining and also produces digestive enzymes. has goblet cells and simple cuboidal cells
why do we want mucous and vili in the mucosa layer
to lubricate passages for food. vili increases the surface area of intestinal tract. allows for smooth movement
what does the submucosa layer do
contains blood vessels, lymphatic vessels, and nerves (loose connective tissue)
what does the muscularis layer do
consists of 2 layers of smooth muscle that move food along the GI tract
what are the 2 layers of muscularis
- circular
- longitudinal
what does the serosa layer do
part of the peritoneum (visceral)
what part of the mouth begins the mechanical breakdown of food (mastication- chewing)
teeth
what is the tongue covered in that assists in the mechanical breakdown and movement of food
taste buds
what is a bolus
mass of chewed food
what forms a bolus and where does it move it to
tongue forms a bolus and moves it toward the pharynx
how many pairs of salivary glands are there
3 pairs
what do salivary glands do
secrete salivary amylase and lingual lipase
what does salivary amylase do
begins carbohydrate digestion or lipid digestion
what type of tissues are tonsils and what main thing do they do
lymphatic tissues at the back of the mouth that are important for fighting disease
what contains lysozyme and later releases them
saliva
what is lingual frenulum and how does it affect tongue tied
connects tongue to lower portion of mouth when frenulum is too low/on mouth and has to be cut to free the tongue
how many teeth are there in adults
32
each tooth is made up of what 2 parts
root and crown
what covers the top part of the crown and is a hard substance
enamel and dentin (bone-like). enamel is top and dentin is secondmost top
what is the inner pulp area of a tooth
has nerves and blood vessels but no osteoblasts. it is living tissue
when do dental caries (cavities) occur and how do you prevent further decay
when bacteria metabolize sugars and produce acids which can wear away at the teeth and produce bigger holes leading to cavities that can be filled with a filling and limiting sugar intake and brushing teeth more to reduce tooth decay
what can dental cavities eventually cause
heart disease
what are the 4 oral structures of the mouth and how many are there of each on one side of the mouth (like bottom right)
- incisiors (2)
- canines (1)
- premolars (2)
- molars (3)
what are incisors
used to bite/cut food
what are canines
used for tearing apart food
what are premolars
tearing and crushing food
what are molars
largest teeth with flat surfaces, to grind, tear, and crush food
what are the 4 types of papillae
- filiform
- fungiform
- foliate
- vallate
what is filiform papillae
roughens the tongue surface, high in keratin (no taste buds)- bottom of tongue
what is fungiform papillae
red due to high blood blow- second bottom of tonugw
what is foliate papillae
form pleats on side of tongue
what is vallate papillae
over back of tongue
what do salivary glands secrete
secrete serous/watery secretion or thick/mucosal secretions
what are the 3 types of salivary glands and what do they mainly secrete
- parotid- serous
- sublingual- mucous
- submandibular- serous
why do we produce saliva
it cleanses the mouth, dissolves food chemicals for taste, moistens food to form bolus, contains AMYLASE to begin starch digestion
the salivary content is made up almost entirely but what and what is the percentage
water (97%)
pH of salivary content
around 6.75 (slightly acidic)
salivary content also contains what 2 things that assist in defending against pathogens
lysozyme and immunoglobulinsA
what is the pharynx
a muscular funnel that connects oral cavity to esophagus and allows entrance of air from nasal cavity to larynx (digestive and respiratory tracts intersect) it brings food down and dumps into esophagus by swallowing
what is misdirection of the bolus prevented by in the pharynx
tongue blocks oral cavity. soft palate blocks nasal cavity (nasopharynx). epiglottis blocks larynx (trachea) so food only goes down esophagus
what is the esophagus
a straight VERY muscular tube 25-30cm long that extends from pharynx to cardiac orifice of stomach (peristaltic motion)
what does the lower esophageal sphincter do
prevents stomach contents fro regurgitating into the esophagus; protects esophageal mucosa from erosive effect of the stomach acid
what is heartburn felt in the esophagus
burning sensation produced by acid reflux into the esophagus
what are the 2 phases of swallowing food
- buccal phase (voluntary control)
- pharyngoesophageal (involuntary phase)
what is the buccal voluntary phase of swallowing
in the beginning, using the tongue to form a bolus and move it to the back of the mouth (voluntary) and food is being swallowed from the mouth into the pharynx
what is the pharyngoesophageal involuntary phase
reflex arc! once food is in pharynx, swallowing becomes a reflex (few secs!)
the ______ is a cavity between the mouth and esophagus that serves as a passageway for food/air. the _____ is a long muscular tube that carries food to the stomach
pharynx, esophagus
explain the steps of swallowing
- tongue compresses food against palate to form a bolus
- bolus passes into pharynx. misdirection of bolus is prevented by tongue blocking oral cavity, soft palate blocking nasal cavity, epiglottis blocking larynx
- upper esophageal sphincter constricts and bolus passes downward and closes back afterwards
- peristalsis drives bolus down esophagus. esophagus constricts above bolus and dilates and shortens below it
- lower esophageal sphincter relaxes to admit bolus to stomach
what is the stomach
a muscular sac in upper left abdominal cavity immediately inferior to the diaphragm
the stomach primarily functions as a
food storage organ
what is the volume of the stomach when empty and after a meal
internal vol of 50mL when empty
1-1.5L after a typical meal
up to 4 L when extremely full and extend nearly as far as the pelvis
how does the stomach mechanically and chemically digest things
mechanically breaks up food particles, liquefies the food, and begins chemical digestion of protein and fat
there are how many layers in the muscle in stomach that aids in mechanical digestion
3
what role does chyme play in digestion of the stomach
soupy or pasty mixture of semidigested food in the stomach
most digestion occurs after the chyme passes on to the
small intestine
the mucosa layer has deep folds called what
rugae (wrinkly internal surface when fills up it becomes flat)
the stomach empties chyme into the small intestine after how many hours
2-6 hrs
how much chyme usually moves at one time? And why?
3mL, a very small amount, moves into the duodenum at a time because we want small amounts of material moving out of the stomach and into the small intestine because smaller amount means more surface area there to increase digestions and absorptions into bloodstream
the mucosa layer of the stomach has deep folds called rugae and gastric pits that lead into gastric glands that secrete what
gastric juice
gastric juice contains pepsin that does what (and HCl and mucous and other enzymes)
enzyme that breaks down proteins
what is the pH of gastric juice
super low and acidic around 2.
what does the low acidic pH of gastric juice aid in
activated pepsin and kills bacteria. also breaks down food connective tissues
does gastric juice absorb nutrients? If not, what does
no, but alcohol is the only thing that can be absorbed into the bloodstream and pass wall of stomach
what are gastric pits
depressions in gastric mucosa lined with simple columnar epithelium and has 2 or 3 tubular glands that open into the bottom of each gastric pit
(cardiac glands in cardiac region, pyloric glands in pyloric region, gastric glands in rest of stomach)
how much gastric secretions does gastric juice make per day by the gastric glands
2 to 3 liters per day
what is the concentration of hydochloric acid being secreted
high and pH is as low as 0.8, (good at killing bacteria) mainly a mixture of water, hydrochloric acid, and pepsin
what are the 5 main secretions by gastric glands
- hydrochloric acid (HCl)
- pepsin
- gastric lipase
- intrinsic factor
- chemical messengers
what are the 4 functions of hydrochloric acid (HCl)
- activates pepsin and lingual lipase
- breaks up connective tissues and plant cell wells (helps liquefy food to form CHYME)
- converts ingested ferric ions to ferrous ions
- contributes to nonspecific disease resistance by destroying most ingested pathogens
the acidic environment of the stomach activates what
your digestive enzymes
what are zymogens (in pepsin)
digestive enzymes secreted as inactive proteins (converted to active enzymes by removing some of their amino acids)
what is pepsinogen (in pepsin)
zymogen secreted in gastric pits (hydrochloric acid removes some of its amino acids and forms pepsin (active form) that digests proteins
protein digestion is completed where
in the small intestine
pepsin digests dietary proteins into shorter peptide chains. why not just release it in active form?
pepsin is a potent catalyst that is good at breaking down proteins and is too powerful and to prevent from deadly pepsin to later be activated
explain the production of pepsinogen
chief cells will produce pepsinogen (inactivated form of pepsin) that will enter into a gastric gland and leave out into the stomach where it comes in contact with HCl acid and becomes activated into pepsin
what is gastric lipase (another factor of gastric production of gastric glands)
produced by chief cells: gastric lipase and lingual lipase play a minor role in digesting dietary fats (digests 10-15% of dietary fats in the stomach, rest digested in small intestine)
what are intrinsic factors (another factor of gastric production of gastric glands)
a glycoprotein secreted by parietal cells. helps absorb B12 (essential)- need B12 for synthesizing hemoglobin and oxygen carriers (prevents pernicious anemia)
secretion of what is the only indispensable (absolutely necessary) function of the stomach
intrinsic factor
gastric glands in kids may release renin which does what
helps coaggulate (make or thicken) milk
digestion takes place mostly where
small intestine
living stomach is protected in what 3 ways from the harsh acidic and enzymatic environment it creates
- mucous coat
- tight junctions
- epithelial cell replacement
how does the mucous coat protect the stomach
thick gel of mucous (basic) resists action of acid and enzymes. gastric glands have mucosal neck to produce mucous released into stomach lining
how does the tight junctions protect the stomach
between epithelial cells prevent gastric juice from seeping between them and digesting the connective tissue. keeps gastric material from being able to meander in between cells
how does the epithelial cell replcement protect the stomach
stomach epithelial cells live only 3-6 days. it is then sloughed off into the chyme and digested with the food. replaced rapidly by cell division in the gastric pits.
what can breakdown of these protective measures result in
inflammation and peptic ulcer
pepsin and hydrochloric acid erode the stomach wall and can result in
ulcer ((damage to stomach wall= ulcer))
a bacterium, helicobacter pylori, lives in the mucous and might cause gastric ulcers. how does it live there
can handle acidity of the stomach
what are the 3 accessory organs that contribute to the small intestine
- pancreas
- liver
- gallbladder
what is the pancreas
spongy organ behind the stomach (endocrine and exocrine)
what are the 3 functions of the pancreas
- secretes insulin (endo)
- secretes enzymes (exo)
- amylase (carbs)
- trypsin (proteins)
- lipase (lipids) - secretes bicarbonate into the small intestine to neutralize stomach acids (augments pH acidity)
what is the liver
a large metabolic organ under the diaphragm (has lots of lobule)
what does the liver do
filters blood from GI tract, thus acting to remove poisons and detoxify the blood (breaks down hemoglobin). removes harmful substances and break down RBCs and blood sugar levels)
the liver removes iron, vitamins A, D, E, K, and B12 from the blood and
stores them
what does the liver store glucose as
glycogen and breaks it down (blood sugar levels)
what does the liver make
bile (contains bilirubin)
what does the gallbladder do for bile
stores it until emulsified to be able to dissolve
why is bile made in the liver and stored in the gallbladder
to be secreted into the small intestine to emulsify fats
how does the liver help regulate cholesterol
by making bile salts (HDL vs LDL)
what are bile canaliculi
narrow channels into which the liver secretes bile
what is the flow of bile from canaliculi to small intestine
- bile passes into bile ductules of the triads, ultimately into the right and left hepatic ducts which merge to form common hepatic duct
- cystic duct coming from gallbladder joins common hepatic duct
- bile duct: formed from union of cystic and common hepatic ducts
- near duodenum, bile duct joins duct of pancreas
- forms expanded chamber: hepatopancreatic ampulla (terminates in a fold of tissue- major duodenal papilla on duodenal wall)
what does the major duodenal papilla contain and what does it do
muscular hepatopancreatic sphincter (sphincter of ODDI).
- regulates passage of bile and pancreatic juice into duodenum
explain what happens to the sphincters if you havent eaten in a while
theres nothing being moved into small intestine so no reason to release pancreatic juice/bile so you store it and close sphincter
what is the gallbladder
a pear-shaped sac on underside of liver, green
what does the gallbladder do
serves to store and concentrate bile by absorbing water and electrolytes. does NOT produce bile
what is bile
yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids. EMULSIFYING AGENT TO HELP ABSORB DIETARY FAT
what is bilirubin (of bile from hemoglobin)
pigment from the decomposition of hemoglobin
what causes the brown color in bilirubin
bacteria in large intestine metabolize bilirubin to urobilinogen
what are bile acids (bile salts)
steroids synthesized from cholesterol
bile acids and lecithin, a phospholipid aids in what
fat digestion and absorption
when would gallstones form
if bile becomes excessively concentrated and forms small nodules
what is evidence of a liver that isn’t fully functional
jaundice (build up of bilirubin)
what is the endocrine portion of the pancreas
pancreatic islets that secrete insulin and glucagon
what is the exocrine gland of the pancreas
99% of pancreas that secretes 1200-1500 mL of PANCREATIC JUICE per day
what is pancreatic juice
alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes (basic)
what does bicarbonate do for the stomach (also in pancreatic juice)
buffers HCl from the stomach (balances pH)
how does the pancreatic duct run lengthwise
through the middle of the gland (hepatopancreatic sphincter)
what is the accessory pancreatic duct
smaller duct that opens independently into the duodenum
what are the 3 things in the pancreas that ALL HELP WITH PROTEIN DIGESTION and where are they released
- trypsin
- chymotrypsin
- carboxypeptidase
- release via pancreatic juices
how are the enzymes released in the pancreas to help with protein digestion
as zymogens (activated inside duodenum) and first inactive
what are the other 3 pancreatic enzymes
- pancreatic amylase
- pancreatic lipase
- ribonuclease and deoxyribonuclease
what does pancreatic amylase do
digests starch
what does pancreatic lipase do
digests fat
what does ribonuclease and deoxyribonuclease do
digest RNA and DNA respectively
the pancreas makes enzymes which break down all ______ of ______ ______-
categories of food items
what are the 3 stimuli that are mainly responsible for the release of pancreatic juice and bile
- acetylcholine (ACh)
- cholecystokinin (CCK)
- secretin
what does acetylcholine do
from vagus and enteric nerves. stimulates secretion during the cephalic phase of gastric control even before food is swallowed (RELEASED WHEN BODY IS GETTING READY TO DIGEST FOOD OR SALIVATING)
what does cholecystokinin (CCK) do
secreted by mucosa of duodenum in response to arrival of fats in small intestine. strongly stimulates gallbladder
released as a result of eating fatty foods (stimulates pancreas and gall bladder)
cholecystokinin (CCK)
what does secretin do
released from duodenum in response to acidic chyme arriving from the stomach. stimulates ducts of both liver and pancreas to secrete more sodium bicarbonate (buffering action)
the small intestine is _____ and ______ diameter while the large intestine is _______ and _______ diameter
long and small diameter. short and large in diameter
enzymes secreted by the pancreas into the small intestine digest what
carbs (amylase), proteins (protease), fats (lipase)
what is secreted by the gallbladder into the small intestine to emulsify fats
bile
absorption of digested food in the small intestine depends on what
large surface area to increase your capacity for the absorption of nutrients
what increases the surface area of the small intestine
villi and microvilli
amino acids and sugars enter the _______ while fatty acids and glyerol enter the _____ (which help absorb lipds)
capillaries; lacteals
the small intestine is where ____ is completed, and ________ are absorbed
digestion; nutrients
what gives rise to the brushy border of the small intestine
cells themselves also have microvilli that give rise to the brushy border (furry brush like appearance)
where are brunnner’s glands located
duodenum
where are the peyer’s patches located
ileum of small intestine
what does the duodenum do
short, neutralize the stomach acids and emulsify fat (bicarbonate-rich mucous)
what happens in the jejunum
8ft, where most all nutrient absorption takes place. most digestion. products of digestion are absorbed into the bloodstream
what happens in the ilium
immune surveillance; longest
where are brush border enzymes
contained in the plasma membrane of microvilli (NOT RELEASED INTO THE LUMEN)
what does the brush border enzymes do
carry out some of the final stages of enzymatic digestion. they stay attached to microvilli and break materials down as they go and do not move into lumen they stay still
what is contact digestion of the brush border
chyme must contact the brush border for digestion to occur. intestinal churning of chyme ensures contact with the mucosa
what are the 3 functions that intestinal motility contractions of small intestine serve
- to mix chyme with intestinal juice, bile, and pancreatic juice (to neutralize acid, digest nutrients more effectively)
- to churn chyme and bring it in contact with the mucosa of bursh border for contact digestion and nutrient absorption
- to move residue toward large intestine
what is segmentation (intestinal motility)
movement in which stationary ringlike constrictions appear in several places long the intestine
what are the 2 types of intestinal motility
- segmentation
- peristalsis
what type of cells instigate segmentation deal with and what are they
pacemaker cells in muscularis externa set rhythm of segmentatione
what happens in segmentation when most nutrients have been absorbed
when most nutrients have been absorbed and little remains but undigested residue, segmentation declines and peristalsis behinds
what is the purpose of segmentation
to mix and churn, NOT to move material along as in peristalsis
what is persistalsis and describe the persistaltic wave
gradual, wave-like movement of contents toward the colon. peristaltic wave begins in duodenum, travels 10-70cm and dies out. followed by another wave starting further down. these are successive, overlapping waves of contractions. milk chyme toward colon over a period of 2 hours
how often do haustral contractions occur
every 30 mins
what are haustral contractions in the large intestine
kind of colonic motility form of segmentation. it is the slow transportation of materials across the large intestine. enlargement of a haustrum stimulates it to contract (in 30 mins cycles)
how often do we have mass movements
1-3 times a day
what are mass movements triggered by and what happens during it
triggered by gastrocoloc and duodenocolic reflexes. filling of the stomach and duodenum stimulates motility of the colon. moves residue for several centimeters with each contraction. (CRAMPING WE FEEL across intestinal tract around eating, intestine is making room)
what 4 things are included in the large intestine
- cecum
- colon
- rectum
- anal canal
what projection does the cecum have
appendix
what is the appendix of the cecum play a role in
fighting infections and retaining good bacteria (so we dont get rid of it)
what type of muscle is the external anal sphincter of the large intestine and why
skeletal to push?
what are the main functions of the large intestine
absorb water to prevent dehydration (not nutrients)
absorb vitamins (B) produced by intestinal flora
form and rid body of feces through the anus
describe the neural control of defecation
when you build feces and have solid lump ready to move, itll fill the rectum and when that fills up, it sends a message to the brain and brain responds causing rectum to contract and open 1 of 2 anal sphincters (internal) and pushes feces against external sphincter to tell you to go to the bathroom. where defecation will occur ONLY if voluntary relaxed by external anal sphincter
digestive tract receives about how much water per day
9 Liters (water must be reabsorbed or youll die of dehydration)
when does diarrhea occur
when large intestine absorbs too little water (feces pass through too quickly if intestine is irritated, feces contain high concentrations of a solute (lactose))
when does constipation occur
when fecal movement is slow, too much water gets reabsorbed and feces become hardened (fluid is pulled out and eventually becomes rocks)
what accounts for the smell and color of feces
bacterial action and gases released causes smell. oxidized iron is the brown coloration
what gives a yellow-orange pigmentation of feces and what is green stool
yellow: bilirubin broken down hemoglobin
green stool: moving too fast or chlorophyll (salads) too fast is bile still
what are the 3 main digestive disorders
- hepatitis
- cirrhosis
- heartburn
what is hepatitis and what is it caused by
inflammation of the liver. causes by Hep A,B,C. treatable by vaccines. can lead to liver damage, cancer, etc
what is cirrhosis
liver becomes fatty and eventually the liver tissue is replaced by fibrous scar tissue. seen in alcoholics and obese people. can lead to liver failure where liver cannot regenerate as fast as its being damaged
what is heartburn
burning sensation produced by acid reflux into esophagus. large meal, pregnancy, obesity, etc (bicarb can relieve)
what is diarrhea disorder of the colon and rectum
increased peristalsis and failure to reabsorb water, due to either an infection or nervous stimulation. rid the body of potential big problems. can lead to dehydration
what is constipation disorder of the colon and rectum
feces are dry and hard; condiiton may be controlled with water and fiber
what can constipation lead to
hemorrhoids (enlarges and inflamed blood vessels of the anus due to chronic constipation, pregnanacy, aging, etc)
what is diverticulosis disorder of the colon and rectum
occurence of pouches of mucosa from weak spots in the muscularis layer than can become infected; often occur in descending colon (MUCOSAL HERNIA PUSHING THROUGH MAKING THIS)
what is polyps and cancer disorder of the colon and rectum
small growths found in epithelial lining that can be benign or cancerous (procedure is camera going in looking for polyps and can go ahead and remove with wire wrapping around it)
