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