Nutrition Chapter 4

Gut microbiota

Bacterial populations that reside in the human large intestine

gastroesophageal reflux disease (GERD)

Chronic condition characterized by frequent heartburn that can damage the esophagus

hemorrhoids

Clusters of small veins in the anal canal

diarrhea

Condition characterized by frequent bowel movements and watery stools

Secretin

Hormone secreted by the duodenum and first part of the jejunum that stimulates the pancreas and liver to release a bicarbonate rich solution into the small intestine

jejunum

Middle segment of the small intestine that aids with some nutrient absorption

gastroesophageal reflux

Pain generally felt in the upper chest that results from the passage of acidic contents from the stomach into the esophagus

Prebiotics

Substances in foods that support the growth of probiotics

Microvilli

Tiny hairlike projections that form the brush border of an enterocyte

digestive system

body system that breaks food down to its components, absorbs nutrients, and eliminates waste

Chemical Digestion

breakdown of large nutrient molecules in food into smaller components, primarily by the action of stomach acid and various enzymes

diverticulosis

condition characterized by the presence of diverticula

salivary amylase

enzyme in saliva that begins starch digestion

cecum

first segment of the large intestine

ileum

last segment of the small intestine

oral cavity

mouth

esophagus

muscular tube that extends about 10 inches from the pharynx to the upper portion of the stomach

mucous cells

secrete mucin

bolus

the mass of food that has been chewed as well as moistened and mixed with saliva

digestion

the process of breaking down large food molecules into nutrients that the body can use

pharynx

the section of the alimentary canal that connects the nasal cavity with the top of the esophagus

Absorption

uptake and removal of nutrients from the digestive tract

Enterocytes

Absorptive cells that form the outer layer of villus

Two major components of the digestive system

GI tract and accessory organs

Constipation

Infrequent bowel movements and feces that are difficult to eliminate

ileocecal sphincter

Region of ileum that controls the rate of emptying undigested material into the large intestine

Diverticula

Small pouches that form in the wall of the colon

external anal sphincter

Sphincter that allows feces to be expelled from the anus and is under voluntary control

Villi

Tiny, fingerlike projections of the small intestinal mucosa that are involved in digestion and nutrient absorption

mucin

a carbohydrate- rich substance that forms mucus when combined with water

enzyme

a protein that speeds up the rate of a chemical reaction without being altered in the process

pepsin

active enzyme that begins the enzymatic digestion of proteins

gastric juice

digestive secretions of the stomach glands consisting chiefly of hydrochloric acid and mucin and the digestive enzymes pepsin and rennin and lipase

dumping syndrome

disorder that occurs when a large amount of chyme flows too rapidly into the small intestine

lysozyme

enzyme in saliva that can destroy some bacteria that are in food or the mouth

mucosa

innermost layer of the digestive tract wall

lower esophageal sphincter (LES)

region of the lower part of the esophagus that controls the flow of material into the upper part of the stomach; also known as the gastroesophageal sphincter

upper esophageal sphincter (UES)

region of the pharynx that opens to allow a mass of food to enter the esophagus

parietal cells

stomach cells that secrete intrinsic factor and the components of hydrochloric acid into the lumen of the stomach

hepatic portal vein

vein that transports absorbed nutrients to the liver

duodenum

First segment of the small intestine where the acidic stomach contents mix with alkaline fluids secreted by the pancreas and gallbladder

Bile

Fluid that is produced in the liver and stored in the gallbladder until it is needed for fat digestion and absorption

goblet cells

Intestinal cells that secrete mucus

Gut microbiota transplantation (GMT)

Introduction of fecal material from one person into another person's colon; "fecal transplant"

Rectum

Last section of the large intestine

Probiotics

Live microbes that promote good health for their human hosts; products that contain beneficial microbes

Segmentation

Regular contractions of circular intestinal muscles followed by muscular relaxations that mix chyme within a short portion of the small intestine

Bioavailability

The extent to which the digestive tract absorbs a nutrient and how well the body uses it

ulcerative colitis (UC)

Type of IBD that chases ulcers to form in the mucosa of the colon and rectum

Chrohn's disease

Type of IBD; the body's immune system cells attach normal intestinal cells, damaging parts of the intestines

Digestive Tract

alimentary canal or gut

inflammatory bowel disease (IBD)

condition that is characterized by chronic inflammation of the GI tract

lingual lipase

enzyme secreted into saliva that begins fat digestion

epiglottis

flap of tough tissue that prevents the food from entering the larynx and trachea

lumen

hollow space through which foods and fluids can pass

Cholecystokinin (CCK)

hormone secreted by the mucosa of the small intestine that stimulates the gallbladder to contract and the pancreas to release pancreatic juice into the small intestine

mastication

physical activity that prepares solid foods for swallowing and chemical digestion

Mechanical digestion

refers to physical treatments that food undergoes while it is in the intestinal tract, such as being chewed into smaller pieces and mixed with various secretions

pyloric sphincter

region of the stomach that regulates the flow of chyme into the small intestine

chyme

semiliquid mass that forms when food mixes with gastric juice

acidic

solutions with a ph less than 7

alkaline (basic)

solutions with a ph more than 7

chief cells

stomach cells that secrete some chemically inactive digestive enzymes

salivary glands

structures that produce saliva and secrete the fluid into the oral cavity

intrinsic factor

substance that is necessary for absorbing vitamin B-12

Accessory organs

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

sphincters

thickened regions of circular muscle that function like valves to control the flow of contents at various points in the GI tract

saliva

watery fluid that contains mucus and a few enzymes

mucus

watery slippery fluid secreted by special cells

peristalsis

waves of muscular contractions that help move material through most of the digestive tract