Module 14

motility

the ability to mix contents and move them from the oral to anal end of the GI tract by muscular contractions

absorption

transport of molecules across epithelial membranes into the body fluids

chyme

mixture of partially digested food and digestive juices that passes from the stomach into the duodenum

peristalsis

* waves of smooth muscle contraction
* serves to propel the contents of the digestive tract in one direction

segmentation

major contractile activity of the small intestine

bilirubin

* yellow substance resulting from heme breakdown
* excreted in bile as a bile pigment
* gives waste its color

enterohepatic circulation

recirculation of a compound between liver and small intestine

heptocytes

liver cells

digestion

process of converting food into molecules that can be absorbed through the intestine into the blood

H/K ATPase pump

transport H+ against concentration gradient into the stomach while transport K+ in opposite direction

bile salt

act to emulsify fat in the lumen of the small intestine

micelles

colloidal particle formed by the aggreggation of numerous molecules

amylase

digestive enzyme of carbohydrates

trypsin

protein digesting enzyme

lipase

digests triglycerides

emulsification

process of producing an emulsion derived from fat globules

accessory digestive organs

* liver
* gallbladder
* pancreas

overall function of digestive system

process ingested foods into molecular forms and transfer, with water and salts, to the circulatory system

systems working with digestive

* cardiovascular
* muscular
* nervous
* respiratory
* urinary

smooth muscle function in D.S.

mix luminal content and move contents from mouth to anus

propulsion

* swallowing
* peristalsis

mechanical digestion

* chewing
* churning
* segmentation

chewing

voluntary control of jaw muscles in addition to rhythmic chewing motions caused by the pressure of food against the gums, hard palate, and roof of the mouth and tongue

chewing involves

* skeletal muscles
* smooth muscles
* neural activity

pressure receptors stimulated by food on the pharyn send…

afferent impulses to the medulla oblongata

efferent fibers tell muscles of pharynx and esophagus to

swallow

soft palate prevents

food from entering the nasal cavity

epiglottis

covers glottis to prevent aspiration

once food is in the esophagus…

upper sphincter closes and waves of muscle contractions move food downward

peristaltic waves

contraction of the muscles surrounding a tube

once food is through the esophagus….

the lower esophageal sphincter closes

stomach

* store
* dissolve
* partially digest macromolecules in food
* regulate rates entering small intestine
* acidity in stomach kills bacteria entering with food

rhythmic peristalsis in stomach are timed by

pacemaker cells

stomach cells secrete

2 liters of HCl per day

\----- gets pumped into stomach as well as -----

* H+
* Cl-

liver serves as

* secretory organ
* filter and functions in the removal of old red blood cells

liver major function

secrete bile

liver also

processes and stores nutrients

hepatic portal system

specialized vasculature that delivers absorbed nutrients to the liver for processing before they enter the general systemic circulation

nutrients are absorbed from----- and carried via capillaries to the ------

* small intestine
* hepatic portal vein

gallbladder

stores and concentrates bile

bile enters from the ---- and exits to the ----- via the -----

* liver
* duodenum
* common bile duct

when the ---- is empty of food, the ---- closes

* small intestine
* common bile duct

pancreas

* produces “pancreatic juice”
* rich in bicarbonate and digesting enzymes

bicarbonate in the pancreas functions to

neutralize acid entering duodenum from stomach

the ----- and ------ join the common bile duct from the liver before entering the duodenum

* bile duct
* pancreatic duct

most material in small intestine is digested and absorbed due to

high absorptive surface area of small intestine

enzymes in small intestine break down food into

* monosaccharides
* fatty acids
* amino acids
* nucleotides

after a meal is mostly absorbed…

the migrating myoelectrical complex replaces segmentation

the migrating myoelectrical complex

moves undigested material into large intestine

large intestine

* primarily stores/makes feces
* small amount of fluid absorption
* houses a variety of gut microflora

gut microflora

converts indigestible polysaccharides into short chain fatty acids for absorption