Nutrition Ch. 4

Gastroesophageal reflux disease (GERD)

A chronic condition characterized by frequent heartburn that can damage the esophagus

Gastric juice

A collection of stomach secretions that includes mucus, HCl, intrinsic factor, and digestive enzymes. Mucus cells secret mucus

Irritable bowl syndrome

A condition characterized by intestinal cramps & abnormal bowel function -Cause unknown

Inflammatory bowel disease (IBD)

A condition that is characterized by chronic inflammation of the GI tract -Crohn's disease -Ulcerative colitis

Dumping syndrome

A disorder that occurs when chyme flows too rapidly into the small intestine -Caused by chyme containing large particles mixed with gastric juices -Results in poor nutrient absorption

Epiglottis

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

Stomach

A muscular sac that stores and mixes food. Gastric glands located in the stomach synthesize and secrete gastric juice

Chyme

A semiliquid mass that forms when food mixes with gastric juice -Occurs in lower stomach

Mucus

A slippery secretion that protects the stomach from being damaged by its acid and digest enzymes -Produced by mucus cells Destruction of tissue of stomach wall can cause gastric or peptic ulcers to form

Peptic ulcer

A sore that occurs in the lining of the stomach or the upper small intestine Symptoms: Deep, dull upper abdominal pain Feeling of fullness 2 hours after eating Factors that increase risk: Infection w/ H.pylori Alcohol consumption Genetics Smoking Emotional stress Excess acid production

External anal sphincter

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

Intrinsic factor

A substance necessary for absorbing vitamin B-12

Ulcerative colitis (UC)

A type of IBD that causes ulcers to form in the mucosa of the colon and rectum

Crohn's disease

A type of IBD; The body's immune system cells attack normal intestinal cells, damaging parts of the intestines

Enterocytes

Absorptive cells that form the outer layer of a villus The end of the enterocyte exposed to chyme contains microvilli Remove nutrients from chyme & enable them to enter the intestinal blood or lymph vessels

Pepsin

Active enzyme that begins the enzymatic digestion of protein

Large Intestine

After moving through the ileocecal sphincter unabsorbed water & undigested remains of chyme enter the: cecum -First segment of the large intestine Ascending colon Transverse colon Descending colon Sigmoid colon rectum -Last segment of the large intestine Anus Little absorption takes place in the large intestine -Some water & minerals Healthy large intestine contains microflora

Nutrient Absorption

Can occur by: simple diffusion facilitated diffusion active transport osmosis endocytosis

Core of he villus

Contains: arteriole capillary network venule lacteal -Vessel of the lymphatic system Nutrients from chyme are absorbed into either the capillary network or the lacteal

Mouth/Oral cavity

Digestion begins here -Teeth masticate food -Prepares food for swallowing and chemical digestion -Tongue helps direct food into pharynx

Small Intestine

Duodenum -First segment of the small intestine Jejunum -Middle segment of the small intestine Ileum -Last segment of the small intestine Chyme moves out of the ileum into the large intestine, passing through the ileocecal sphincter Major site of chemical and mechanical digestion -Enzyme activity -Peristalsis -Segmentation The mucosa of the small intestine is highly folded and covered by villi -Each villus has enterocytes

Salivary amylase

Enzyme in saliva that begins starch digestion

Lysozyme

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

Lingual Lipase

Enzyme secreted in saliva that begins fat digestion

Bile

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

Prebiotics

Food components that beneficial bacteria in the the large intestine use for fuel Health benefits: Alleviate constipation and allergy symptoms Improved immune function Protection against colon cancer Prevention of obesity

Diarrhea

Frequent, watery bowel movements -More water secreted into GI tract -Less water absorbed by GI tract Most cases are caused by bacterial or viral infections

Two major components of digestive system

GI tract: Hollow, muscular tube Accessory Organs: Assists GI tract

Vomiting

Generally doesn't last longer than 24 hours Repeated vomiting can lead to dehydration Danger signs: Accompanied by - Blood in vomit (coffee grounds) Fever Diarrhea Fever Weakness Headache or stiff neck Severe abdominal pain Confusion

Gastrin

Hormone secreted by G cells that stimulates stomach motility & gastric gland secretions

Secretin

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

Cholecystokinin

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

Constipation

Infrequent bowel movement and feces that are difficult to eliminate Can be caused by: Lack of dietary fiber Low water intake Anxiety Depression Changes in typical routine

Goblet-cells

Intestinal cells that secrete mucus -Primary secretion of the large intestine

Probiotics

Live microorganisms that promote good health for their human hosts -Lactobacillus Bifidobacterium Health benefits: Prevention & treatment of diarrhea, inflammatory bowel disease and lactose intolerance Improved blood fat levels Protection against ulcers

Accessory organs

Liver, gallbladder, pancreas -Chyme does not pass through them -Play a major role in digestion

Wall of the GI tract

Mucosa: -Innermost layer of the digestive tract wall -Mucus, a watery slippery fluid, is secreted from special cells here -Surrounds the lumen -Hollow space through which food and fluids can pass Muscular layer: -Circular -Longitudinal By relaxing and contracting, the muscles can mix substances in the lumen & control movement through the tract The walls of the stomach is the thickest & strongest of the GI tract -Third type of muscle -Diagonal muscle

Esophagus

Muscular tube that extends about 10 inches from the pharynx to the upper portion of the stomach. Entrance is near the larynx and opening of trachea

Microflora

Population of several kinds of bacteria -Metabolizes undigested food -Synthesizes certain fats used for energy by cells of colon -Produces vitamin K, folate, B-6, B-12, & biotin and gas Beneficial to human host

Pancreas

Produces digestive enzymes and bicarbonate ions

Enzymes

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

Ileocecal sphincter

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

Segmentation

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

Pyloric sphincter

Regulates the flow of chyme into the small intestine

Parietal cells

Secrete intrinsic factor and the components of HCl acid into the lumen of the stomach

Chief cells

Secrete some chemically inactive digestive enzymes -Pepsinogen -Gastric lipase

Pharynx

Section of alimentary canal that connect the nasal cavity with the top of the esophagus

Gallbladder

Stores and concentrates bile

Liver

Stores and process nutrients Synthesizes cholesterol Makes bile

Salivary glands

Structures that produce saliva and secrete the fluid in the oral cavity

Hemorrhoids

Swollen veins in the anal canal

Primary roles of digestive system

The breakdown of food into nutrients Absorption of nutrients Elimination of solid waste products

Chemical digestion

The breakdown of large molecules in food into smaller components, primarily be the action of enzymes

Bolus

The mass of food that has been chewed, moistened, mixed with saliva, and swallowed -Travels through the esophagus

Heartburn

The pain generally felt in the upper chest that results from the passage of acidic contents from the stomach into the esophagus Factors that contribute to or worsen heartburn: Excess body fat Drinking alcohol, coffee, carbonated drinks, citrus juices Overeating Smoking Reduce the Risk of Heartburn Lose excess body weight Don't overeat Avoid smoking Don't lie down within 2 hours after meal

Mechanical digestion

The physical treatments that food undergoes while it is in the intestinal tract

Digestion

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

Lower Esophageal Sphincter (LES)

The region of the lower part of the esophagus that controls flow or material into the upper part of the stomach -Gastroesophageal sphincter -Prevents back flow of stomach contents

Upper Esophageal Sphincter (UES)

The region of the upper part of the esophagus that opens to allow a mass of food to enter the esophagus

Absorption

The uptake and removal of nutrients from the digest tract (gastrointestinal tract, alimentary canal, or gut)

Peristalsis

The waves of muscular contractions that help move material through most of the digestive tract -Involuntary response to swallowing -Mixes food with gastric juices -Some protein & fat is broken down

Sphincters

Thickened regions of circular muscle that controls the flow of contents at various point in the GI tract -Contracted -Passageway closed -Flow is restricted -Essential for normal digestion and absorption

Diverticula

Tiny pouches that form in the wall of colon -Diverticulosis: The condition characterized by the presence of diverticula -Diverticulitis: The condition characterized by inflamed diverticula

Villi

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

Microvilli

Tiny, hairlike projections that form the brush border of an enterocyte -Contain brush border enzymes -Help digest protein & carbs

Hepatic portal vein

Vein that transports absorbed nutrients to the liver

Saliva

Water fluid that contains mucus and a few enzymes

Hormone

a chemical messenger secreted by organs of the endocrine system that convey information to target cells

Alkaline Solutions

pH value higher than 7

Acidic Solutions

pH value lower than 7 -pH of chyme is 2.0 Acidic environment of stomach causes: -Salivary amylase to cease -Pepsinogen to be converted to pepsin

Five basic tastes

sweet, sour, salty, bitter, umami Distinguished by taste buds