Gastrointestinal Physiology Flashcards
what are the four processes of digestion?
- secretion
- digestion
- motility
- absorption
what is secretion?
- enzymes being secreted in tubes of digestive tracts
- saliva in mouth and acid in stomach
- enzymes used to break down food
what is amalase?
enzyme that breaks down carbs
what are the two types of digestion?
mechanical (big to small through chewing) and chemical (uses enzymes, needed to absorbed nutrients)
what is motility?
moving food from mouth to rectum (movement at a carefully controlled speed; peristalsis)
what is absorption?
how to get nutrients into bloodstream (once small enough, moves through epithelial cells and becomes absorbed for nutrients)
what are three accessory organs of the digestive system?
gallbladder, liver and pancreas
what is the job of the oral cavity?
secretion
what does secretion do?
- lubricates
- helps with ability to taste our food
- protects mouth and teeth
- aids with speech
describe saliva composition
- mostly water and ions such as sodium and chlorine
what are the three salivary glands?
- parotid gland
- submandibular gland
- sublingual gland
where is the parotid gland found?
cheeks area
where is the submandibular gland found?
under mandible
where is the sublingual gland found?
under tongue
describe the three types of salivary glands
parotid gland = watery
submandibular gland = music and watery saliva
sublingual gland = mostly mucus
what is the term used to describe mechanical digestion through chewing?
mastication
chemical digestion in the oral cavity is done by what salivary enzyme?
amylase
is lingual lipase active when in the oral cavity?
NO, lingual lipase is activated in the stomach
(oral cavity) three steps of motility :
- mastication (chewing); mechanical motility, movement from back to front of mouth
- swallowing (only cavity to the esophagus)
- peristalsis : top to bottom of esophagus
“co-ordinate contraction of the muscles in the esophagus, involuntary control, propels bolus towards the stomach” is all used to describe…
peristalsis
what are the two “movements” of peristalsis and what does it do”?
- longitudinal (push it down)
- circular (constrict)
what is absorbed in the oral cavity (bare minimal absorption) and where does it mostly occur?
glucose / drugs and mostly occurs under the tongue
what organ acts as a reservoir for bolus before it enters the intestine?
stomach
what liquid/acid is found in the stomach?
hydrochloric acid
how does bile become chyme?
it mixes with the acid in stomach
what part of body leads into the stomach?
esophagus (through diaphragm)
where does the esophagus attach?
to the cardia
what does the lower esophageal sphincter do?
stops stomach acid from coming up?
which side of the stomach has a bigger curve?
left side (greater curvature)
what happens if too much acid is getting pushed up?
- acid reflex (sphincter isn’t closed all the way)
- increase abdominal pressure
what part of the stomach attaches to the small intestine?
antrum
what is the sphincter at the end of the stomach?
pyloric sphincter
when does the pyloric sphincter open?
only opens when food needs to go into the intestine
what are the four layers of the stomach?
- muscosa
- submucosa
- smooth muscle (muscular externa)
- serosa
describe the mucosa?
- innermost
- protect stomach from bacteria and acid
describe the submucosa? (stomach)
- neural network (info being sent)
- has submucosal plexus (helps with mucous excretion)
describe the smooth muscle?
- muscular contractions of the stomach
- circular and longitudinal muscle to change shape of stomach
contains a neural network (myenteric plexus; peristalsis)
describe the serosa?
- protective layer
- dense connective tissue
- outermost
which layer of the stomach is responsible for muscular contractions of the stomach?
smooth muscle (muscular externa)
what layer protects the stomach from bacteria and acid?
mucosa
which layer has a submucosal plexus that is responsible for helping with mucous excretion, etc.
submucosa
what are the three exocrine cells of the stomach?
- mucous neck cells
- chief cells
- parietal cells (oxyntic cells)
what is the endocrine cell of the stoamch?
G cells
what does mucus neck cells do?
secrets mucous and bicarbonate (to protect stomach)
what do chief cells do?
secretes pepsinogen and gastric lipase
what is pepsinogen?
the inactive version of pepsin
what is the endocrine cell of the stomach?
G cells
what do G cells do?
secrete the hormone gastrin
what does gastrin do?
releases HCl and stimulates gastric acid
what do parietal cells do?
secretes H+ and Cl - (HCl) and intrinsic factor
what is intrinsic factor?
helps absorb B12 and terminal ileum
what are the three movements of digestion in the stomach?
propulsion, grinding and retropulsion
describe the direction of propulsion, grinding and retropulsion …
- propulsion = moving foward
- grinding = circular contraction
- retropulsion = pushing backwards as we let little amounts move through
how does bolus become chyme through chemical digestion?
- secreted gastric juices contain HCl
- secreted pepsnogen converted to pepsin
what does pepsin do?
pepsin is the active for of pepsinogen and it is an enzyme that aids in protein digestion in the stomach
name the 6 functions of acid in the stomach
- activation of lingual lipase (lipid digestion can occur)
- activation of pepsin (from pepsinogen)
- inactivation of salivary amylases
- kills microbes (with HCl)
- denatures proteins
- stimulates secretion of hormones
where does carbohydrate digestion completely stop?
in the stomach
what are the three parts of the small intestine?
- duodenum
- jejunum
- ileum
where does nutrient absorption occur?
small intestine
what is the job of the duodenum?
decreasing acidity of chyme
what is the job of the jejunum?
absorption (increase SA)
what is the job of the ileum?
responsible for absorption and digestion of nutrients and vitamins like B12, etc and everything else not absorbed prior
where does most absorption in the small intestine occur?
jejunum
what does villi in the jejunum do?
increases surface area for optimal absorption
what are the four layers of the small intestine?
- mucose
- submucosa
- smooth muscle (musularis)
- serosa
what’s the difference between layers of the stomach and the small intestine?
- the mucosa of small intestine is responsible for mucus secretion
- the mucosa of the stomach is responsible for protects the stomach from bacteria and acid
- serosa is opposite of each other (small intestine very thing and stomach thick)
what does the myenteric plexus do?
controls the muscles (peristalsis)
what are the two movements of motility of the small intestine?
segmentation and peristalsis
what it segmentation?
mixing back and fourth, allowing for touching (increases the interactions of particles of food in chyme with absorptive cells of the mucosa layer)
name the 7 cell types of the small intestine?
- absorptive cells
- goblet cells
- K cells
- intestinal gland cells
- paneth cells
- S cells
- CCK cells
what do absorptive cells do?
helps absorption of nutrients (epithelial cells with microvilli)
what do goblet cells do?
secretes mucus
what do intestinal gland cells do?
secretes alkaline watery mucus and helps protect from acid of stomach
what do paneth cells do?
secretes lysozyme (helps fight against pathogens)
what do S cells do?
secretes secretin
what do CCK cells do?
secretes cholecystokinin
what do K cells do?
secretes (GIP)
what does secretin tell the liver/pancrease to do and is it a hormone/enzyme?
- hormone not an enzyme
- tells liver and pancreas to separate its enzymes
what does GIP do ?
stimulates insulin to be secreted
what does cholecystokinin (CCK) do ?
tell pancreas to secrete enzymes and gall bladder to contract
where is bile created and stored?
created in the liver and stored in gallbladder
what does microvilli do?
increases surface area for absorption of nutrients
what is the very last step in regards to chemical digestion?
microvilli
what are brush border enzymes
cells on the microvilli (which have enzymes)
what are the 6 brush border enzymes?
- lactase
- sucrase
- malatase
- aminopeptidase
- dipeptidase
- enteropeptidase
what is lactose broken down by?
lactose is broken down by lactase into glucose + galactose
what is sucrose broken down by?
sucrose is broken down by sucrase into glucose and fructose
what is maltose broke down by?
maltose us broken down by maltase into glucose and glucose
where are brush border enzymes mostly found?
in duodenum
what does aminopeptidase do?
removes one amino acid from the end of a protein
what does dipeptidase do?
cuts a dipeptide into two single amino acids
what does enteropeptidase do?
cuts trypsinogen into trypsin
what does the large intestine do?
- completes absorption (usually water)
- highly populated by bacteria
- beneficial for completing nutrient extraction
- reabsorbes water
what are three points of motility of the large intestine
- gastroileal reflex
- haustraul churning
- peristalsis and mass peristalsis
what does the gastroileal reflex do?
presence of food in the stomach stimulates the opening of the ileocecal valve (neural reflex)
what does haustral churning do?
responsible for mixing of elements and allows for optimal absorption of mostly water from lumen contents
what does peristalsis and mass peristalsis do?
unidirectional movement of lumen contents out of the large intestine (into rectum) (feeling of having to go to the washroom)
what organ has both endocrine and digestion function?
pancreas
what are the names of epithelial cell clusters and the cells that form the ducts that together make exocrine secretions ?
acinar and ductal cells
where does the pancreas secrete directly into?
the duodenum
what comes from ductal cells?
bicarbonate
what does bicarbonate do?
neutralizes the acid from the stomach
what 7 enzymes come from acinar cells ?
- pancreatic amylase
- pancreatic lipase
- trypsinogen = trypsin
- chymtrypsinogen = chymotrypsin
- procarboxypeptidase = carboxypeptidase
- prophospholipase = phospohlipase
- procolipase = colipase
what type of carbohydrate is amalose?
complex carbohydrate
what is pancreatic amylase?
enzyme from pancreas breaking down
what is pancreatic lipase?
enzyme that breaks down lipids
what is trypsinogen?
inactive form that is further turned into trypsin (active form) used for the breakdown of proteins
what is chymotrypsinogen?
trypsin converts chymotrypsinogen into chymotrypsin which is used in the breaking down of proteins found in chyme
what converts procarboxypeptidase into carboxypeptidase?
trypsin converts procarboxypeptidase into carboxypeptidase
what is prophospholipase?
prophospholipase is the active form from procarboxypeptidase
what happens to the amino group during carboxypeptidase?
take off amino group @ end of carboxy
what does colipase do?
works as cofactor with pancreatic lipase
what is used to turn chymotrypsinogen, procarboxypeptidase and prophospholipse into its active form?
trypsin
what does trypsin do?
activates enzymes that cuts proteins