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digestive
n/a
29
Physiology
Undergraduate 2
12/02/2010

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Term
what is the process of moving the food in a wave-like contractions toward the esophagus called?
Definition
Peristalsis
Term
can you describe the difference between peristalsis and segmentation? where along the alimentary canal do these processes occur?
Definition
peristalsis is a one way smooth muscle contraction for propultion of food from the esophagus to the anus. segmentation is back and forth smooth muscle contraction in the small intest. only for mechanical digestion
Term
where is the gastroesophageal sphincter is and what does it do?
Definition
its at the junction of the esophagus and the stomach. it opens to allow the passage of bolus into the stomach from the esophagus but also remains shut in between to keep stuff in the stomach from getting into the esophagus
Term
what mechanical process does the stomach perform
Definition
churning. which is twisting, shortening and constricting motion of the stomach
Term
in what ways is the stomach stimulated when a bolus enters it
Definition
stretch and pH increase
Term
what is the average pH in the stomach
Definition
pH- 2.0
Term
how does pH change when the bolus enters the stomach? which cells does this change in ph stimulate? what is the response of these cells
Definition
the bolus causes a rise in the pH (more alkaline). -it stimulates the G cells, which will secrete gastrin to activate parietal cells
Term
list the various functions of the digestive system
Definition
ingestion, digestion, propulsion, absorption, elimination.
Term
ingestion
Definition
introduction of food into the mouth
Term
digestion
Definition

breaking large food particle into absorbable molecules by chemical or mechanical digestion.

chemical- uses chemicals like acid and enzymes

mechanical- physical process of breaking food down (chewing and stuff)

Term
propulsion
Definition
movement of food stuff through the alimentary canal by muscular contractions
Term
absorption
Definition
nutrient molecules crossing the mucosal cells and entering the blood circulation
Term
elimination 
Definition
the removal of indigestable foods by defication
Term
what is the difference between elimination and excretion
Definition
elimination rids the alimentary canal of matter that was never part of the body. excretion is the act of removing waste that was produced in the body
Term
can you list the two mechanisms of digestion and the three phases
Definition

mechanisms- chemical and mechanical

phases 3- 1.cephalic phase: everything that happens from mouth to stomach including CNS activity. 2 gastric phase: actions preformed in the stomach. 3 intestinal phase: small and large intestines 

Term
can you list and describe the various stimuli that can cause a response by the alimentary canal 
Definition

-change in ph due to acidity change

-change in osmolarity, incoming food brings increased concentration of solute

-stretch to accommodate the size of the food

-CNS the brain can stimulate parts of the canal like churning and secretion HCl by Ach of the vegas nerve 

Term
when sensory information regarding food/eating reaches the brain, what responses will occur under parasympathetic direction?
Definition
salivation, stomach motility and secretion of gastric juices. cephalic phase, since these activities are directed by the brain via Parasympathetic nervous system
Term
can you describe which mechanical process occur in the cephalic phase
Definition
chewing (mastication) performed by the teeth to grind the food and the tongue to mix the food with saliva
Term
can you describe the function of saliva in the mouth
Definition
cleanses the mouth, moisten the food to form a bolus, chemical digestion of starches by salivary armylase, dissolves tastants to bind to their receptors and provides immunity in the mouth
Term
do you know the composition of saliva and which cells secrete these components 
Definition
serous cells secrete the majority of the slightley acidic saliva, which is mostly water with ions, antibody, lysozymes and mucin. mucous cells secrete additional mucus to help ease the passage of food through the tract
Term
what is a bolus and how is it formed 
Definition
it is masticated foodstuff mixed with saliva by the tongue
Term
can you describe the general process of swallowing. what is the scientific name of this process
Definition
it is a voluntary action performed by the skeletal muscle of the teeth, soft palate, pharynx and upper esophagus to propel the bolus into the esophagus from the mouth, called-deglutition 
Term
can you describe the make up of the muscular layer of the esophagus and how the make up changes from top to bottom. how does this make up allow the esophagus to function.
Definition
the first third of the esophagus is skeletal muscle and plays a role in the voluntary action of swallowing. the second third is half skeletal and half smooth so voluntary action is completed and involuntary paristolsis begins. the 3rd is smooth continues paristolsis waves
Term
how are G cells turned off
Definition
the HCl production causes the pH to decrease again (more acidic) which stimulates D cells. these ceslls secrete somatostatin, a hormone that enters the blood and inhibits G cells
Term
what is the function of parietal cells 
Definition
produce HCl
Term
can you list the three things that stimulate the parietal cells? and where do these three stimulants come from
Definition

Gastric (from G cells)

Ach (from vagus nerve)

histamine (from ECL cells)

Term
what kind of acid is stomach acid? what is this acid good for as far as digestion is concerned
Definition
HCl, it denatures protien and CT digestion
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