NDFS 1020 - Ch. 4 Human Digestion, Absorption, and Transport
bile
A substance produced by the liver that breaks up fat particles.
pepsin
An enzyme present in gastric juice that begins the hydrolysis of proteins
villi
Fingerlike extensions of the intestinal mucosa that increase the surface area for absorption
jejunum
Middle portion of the small intestine
fascilitated diffusion
Movement of specific molecules across cell membranes through protein channels
chyme
Partially digested, semiliquid food mixed with digestive enzymes and acids in the stomach.
gut microbiota
Populations of microbes, consisting of many species of bacteria and other heterotrophic microbes, living in the gut lumen.
active transport
Some nutrients move from the lumen of the intestine and into an enterocyte against the concentration gradient; that is, the concentration of the nutrient is higher inside the absorptive cell than in the lumen. This is called what?
mucosa
The innermost layer of the human digestive tract; in some parts of the digestive system, it contains mucus-secreting cells and glands that secrete digestive enzymes
liver
This organ produces bile
hepatic portal vein
Water-soluble nutrients and certain fats pass directly from enterocytes into the capillary network of the villus. Eventually, these nutrients travel to the liver via what?
lumen
a hollow space through which food and fluids pass through the GI tract
digestive system
body system the breaks down food and absorbs nutrients
duodenum
first part of the small intestine
diarrhea
frequent passage of loose, watery stools
simple diffusion
occurs when the concentration of a particular nutrient is higher in the lumen of the small intestine than in an enterocyte
alkaline (basic)
pH greater than 7
acidic
pH less than 7
Segmentation
regular contractions of circular intestinal muscles followed by muscular relaxations to mix chyme within a short portion of the small intestine
enterocytes
specialized absorptive cells in the villi of the small intestine
hemorrhoids
swollen, twisted, varicose veins in the rectal region
accessory organs (of the digestive system)
teeth, tongue, salivary glands, liver, gallbladder, and pancreas
20-25 (feet)
the average length of the GI tract for an adult
12 (hours)
the average number of hours it takes for food to pass through your GI tract
Bioavailability
the extent to which the digestive tract absorbs a nutrient and how well the body uses it
ileum
the last and longest portion of the small intestine
mastication
the process of chewing
sphincters
thickened regions of circular muscle that function like valves to control the flow of contents at various points in the GI tract
peristalsis
waves of muscular contractions that help move material through most of the digestive tract