gastrointestinal tract Flashcards
what is the GI tract composed of? (7)
mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum
what does accessory digestive organs mean?
the organs that HELP the digestive organs do their job
what are the accessory digestive organs in the digestive system? (5)
teeth and tongue
salivary glands (amylase)
gallbladder- store bile (breaks fats) produced by liver
liver
pancreas
where does most absorption occur in the digestive system?
small intestine
what does bile do?
emulsifies fats into smaller molecules
what does the pharynx do?
stops food from entering respiratory system
what is the function of the GI tract?
to digest, absorb nutrients and provide protection.
what happens to the ph of your body when you vomit?
body becomes alkaline as you lose acid, need to go through homeostasis to restore
what’s the opposite of secretion?
absorption
what does active absorption require
ATP
what’s the difference between the GI tracy and the rental system?
GI system absorbs everything and doesn’t regulate concentration of each ion whereas the renal system maintains homeostasis of ions
what are 4 major activities of the GI TRACT?
- motility - moves (propels) ingested food from mouth to rectum
- secretion- aids in digestion and absorption process
- digestion- chemical and mechanical breakdown of food into absorbable units
- absorption- active or passive transfer of substances from lumen to the extracellular fluid
where do absorbed nutrients go for more processing?
liver takes In the absorbed nutrients after coming out of small intestine
what is chyme?
what the digested food in the stomach Is called after
what are the 2 patterns of gastrointestinal smooth muscle contractility?
- segmentation contractions
2.peristaltic contractions
what do peristaltic contractions do?
move food along gut in oral to anal direction
orchestrated waves of contraction and relaxation that move wave like along gut
mainly happens in oesophagus and small intestine
in peristaltic contractions what is the ball of broken food called
bolus
which is propulsive and non-propulsive contractions?
peristaltic contractions are propulsive (movement)
segmentation contractions are non-propulsive
what happens in segmentation contractions?
mixing of food and keeping it in contact with epithelium
where does segmentation contractions mainly occur?
small intestine
why does the food stay in contact with the epithelium?
they have small microvilli which increase surface area to aid absorption of nutrients
where are enzymes secreted from? (2)
endocrine glands (salivary glands and pancreas)
epithelial cells in mucosa
why does mucus line the stomach?
so acid doesn’t burn away lining of stomach
what’s digested in the mouth
mainly starch
what’s digested in the stomach
mainly proteins
what is digested in the small intestine? (3)
proteins, starch, fats
what is happens in the large intestine in terms of bacteria?
some fermentation of carbs and proteins by bacteria
what happens in the large intestine?
proteins stach and fats broken down into smaller molecules for absorption
what vitamin is absorbed in large intestine
b12
what is the scientific term for chewing food
mastication
what happens in mechanical digestion
mastication, creates boils of food that can be easily swallowed
what happens in chemical digestion?
salivary amylase digests starch to maltose
breaks down proteins …
4 stages of reflex action of swallowing ?
1.closure of epiglottis (little bit that closes so it blocks trachea)
2.opening of her oesophageal sphincter (top of esophagus)
3.peristaltic wave down esophagus (bolus contraction and relaxation)
- opening of lower oesophageal sphincter into stomach
what is the function of the esophagus (2)?
- secrete mucus (goblet cells)
- moves food from throat to stomach using muscle movement called peristalsis
what happens when acid from the stomach gets into the esophagus?
heart burn/ acid reflux
how long is the esophagus?
10 inches long
what is the food found in the stomach called?
chyme
what does the stomach (j shaped muscular bag) do ?
breaks down food into tiny pieces especially protein
mixes food with digestive juices that contain enzymes to break down proteins (pepsin, protease) and lipid.
what is the role of acid in the stomach?
kills bacteria
how long is the small intestine ?
7 metres long
what is the role of villi in the small intestine walls?
increase surface area for absorption
what are the villi covered in to further increase sa?
microvilli
what digestive enzymes does the small intestine release?
protease, amylase, lipase
what does the small intestine absorb?
vitamins, minerals, carbs, proteins, lipids, 80% ingested water
what is the 1st stage of the 3 stages to the gastric (stomach) phase?
- neuronal response: stomach stretch and chemoreceptors in stomach stimulate parietal cells to produce hcl and chief cells to release pepinsogen which is activated and converted to pepsin by hcl
what is the 2nd stage of the 3 stages to the gastric (stomach) phase?
- hormonal response: enteroendocrine cell responses (specialised cells in gi tract)
chyme peptides trigger gastrin (hormone SECRETES gastric juice by stomach wall released from G(ASTRIC) CELLS
STIMULATES GASTRIC ACID PRODUCTION
what is the 3rd stage of the 3 stages to the gastric (stomach) phase?
mast cells release histamine to fight infection etc..
where are gastrin cells
stomach and duodenum
where are chief cells found? what does it produce?
in the stomach: release pepsinogen and chymosin. pepsinogen is activated into the digestive enzyme pepsin when it comes in contact with tcl reduced by gastric parietal cells
what do mast cells release and when?
histamine: when mast cells detect allergy, infection in the body
how does histamine work?
histamine boosts blood flow in the area of your body the allergen affected. WBC in the brain tackle it.
what is the 1st intestinal phase ?
- NEURONAL RESPONSE: ENTEROGASTRIC REFLEX
Stimulated by increased acid levels in the duodenum : causes pyloric sphincter (opening to duodenum) to close so no more acid goes into duodenum
-Suppresses gastric acid secretion: gastrin cells stop secreting gastrin hormone >gastric juices
-decreases gastric motility.(propels/moves ingested food)
what is the 2nd intestinal response ?
hormonal response: I cells in the small intestine secrete CHOLECYSTOKININ (CCK),
released after meal and stimulates the digestion of fat and protein
Secretin (S cells in the duodenum and jejunum secrete) triggered by drop in pH (<4.5)
Gastrin triggered by partially digested food
how long is the large intestine?
5 feet long
what are the main functions of the large intestine (colon)?
-ferment carbs
-protein breakdown
what is haustration?
slowing down of propulsion (movement of food)
what is the role of the liver?
produces bile which helps digest fat
-filters out toxins and waste including drugs and alcohol
-PLASMA PROTEIN SYNTHESIS
cholesterol synthesis
breakdown of erythrocytes
what are liver cells called?
HEPATOCYTES
what do hepatocytes look like?
cuboidal cells
arranged in plates- lobules
what are phagocyte cells in the liver that breakdown RBC called?
KUPPFER CELLS
WHAT do hepatocytes absorb and store?
excess nutrients in the blood like :
glucose (glycogen)
iron
retinol (vit a)
CALCIFEROL (vit d)
what are nutrients stored by the hepatocytes released?
when levels are too low (fasting)
what does the gallbladder do?
stores bile from liver, releases it into small intestine
what forms in the gall bladder as a relic of fatty diets?
gallstones
what happens when bile is stored in the gallbladder?
concentrated
acidified
what stimulates bile and what triggers its release?
stimulated: secretin
released: parasympathetic ns and cck
what is bile composed of?
Contents:
HCO3- (Bicarbonate)
cholesterol,
bile salts
bile pigments(green colour)
what is the role of pancreas?
(2)
- produce digestive enzymes: fats, carbs, proteins
- regulates blood sugar by producing insulin
what is the pancreatic juice composed of? (6)
lipase
amylase
chymotrypsinogen: activated by trypsin
nuclease
trypsinogen: activated by enterokinase
buffer (HCO3-)
2 main pathways in the body for reabsorption materials?
- hepatic portal system (carries nutrients to liver)
- enterohepatic circulation (recycles bile salts)
