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KNH 102 CH3

Nutrition CH3; Digestion, Absorption, and Transport

What is digestion? The body's way of breaking down foods into nutrients in preparation for absorption.
Summarize some challenges of this process (digestion) -throat must preform breathing & swallowing -food must pass through diaphragm to reach stomach -everything must constantly move forward -foods must be lubricated with right amt of fluid -digestive enzymes must not digest cells of GI tract -control BM
What composes GI tract? -it is a flexible muscular tube that extends from: mouth, esophagus, stomach, small/large intestine, rectum & anus.
What is the lumen? The inner space in the GI tract.
Summarize what happens in the mouth chewing: breaks down food & mixes w/ salivary glands to be tasted by tongue & swallowed. taste buds: taste sweet, sour, salty, bitter --when food is swallowed, passes thru pharynx (shared by digestive & respiratory sys)
What is the pharynx? a short tube shared by digestive & resp sys's. The passageway from nose/mouth to larynx & esophagus. Directs food from mouth to esophagus.
What is the epiglottis? Epiglottis closes off entrance to the lungs so choking doesn't happen when swallowing.
What is the role of the esophagus? Passes food from the mouth to the stomach.
What is a bolus? A portion of food swallowed at one time.
What is a sphincter & why is it important? a circular muscle that constricts a passage/closes an orifice. When relaxed, allows materials to pass through. When contracted, closes the opening. Four main sphincter muscles: the cardiac sphincter, the pyloric sphincter, and two anal sphincters.
What is a chyme & where does it go? A semiliquid mass transferred by the stomach to the remainder of the GI tract [small/large intestine(colon)/rectum]
What are the 3 sections of the small intestine? (in order) 1. Duodenum 2.Jejunum 3. Ileum (makes up about 10 ft of tubing!)
What is the ilocecal valve & its purpose? Where is it located? -it is a sphincter; opens/closes passage to large intestine. -located @ the beginning of large intestine.
What is the appendix? Where is it located? -It is at the beginning of the large intestine past the ilocecal valve. -Store lymph cells; is a narrow blind sac extending from the beginning of the colon that stores lymph cells.
What happens in the large intestine (Colon)? -Chyme passes through a sphincter(ilocecal valve) to enter, passes appendix, travels up right side to front left & down. -Withdraws water, leaving semisolid waste.
What is the rectum? The muscular terminals part of the intestine, extending from the sigmoid colon to the anus; stores waste.
What is the anus? The terminal outlet of the GI tract; it holds rectum closed & opens to allow elimination.
What is peristalsis & why is it important? How is it created? Wave-like muscular contractions of the GI tract's CIRCULAR & LONGITUDINAL muscles that push its contents along. -when rings TIGHTEN & long relax = tube constricted -when rings RELAX & long tighten = tube is bulged.
What can interfere with normal GI contractions? -stress (IBS), medicines & medical conditions.
List actions that occur in the stomach -Thickest walls/strongest muscles of GI -Circular, longitudinal & diagonal muscles force the chyme down while pyloric sphincter stays closed; churns chyme while gastric juices are released. -When contents are liquefied the pyloric sphincter opens 3x mi
What is segmentation? What is its purpose? -When the circular muscles contract to squeeze their contents; this mixes the chyme & promotes close contact w/ digestive juices & the absorbing cells of the intestinal walls before letting the contents move along.
Important sphincters? -Esophageal sphincter [top] -Lower esophageal/cardiac sphincter -Pyloric sphincter -Ileoceal valve -Rectal muscles
Lower esophageal sphincter/cardiac sphincter @ bottom of esophagus; prevents reflux of stomach contents.
Pyloric Sphincter @ bottom of stomach; holds chyme in stomach long enough to be liquefied. Prevents intestinal contents from backing up into stomach.
Ileocecal valve @ end of small intestine; allow contents of small intestine to empty into large intestine.
What organ secretions are required for digestion? (5 different organs) 1.Salivary glands: exocrine glands 2.Stomach: adds acid, enzymes, fluid 3.Pancreas: exocrine sec. of enzymes + bicarbonate 4.Liver: via gallbladder 5.Small instest
What are enzymes & what are their functions? -A protein that facilitates a chemical rxn. -In digestion they facilitate hydrolysis(addition of H2O) to break molecule into smaller pieces. -"ase" denotes an enzyme
Purposes of saliva? What does it contain? -from salivary glands -contains H2O, salts, mucus, enzymes -Initiates digestion of carbohydrates, protects teeth & lining of mouth/esophagus/stomach
What is in gastric juice? Water, enzymes, hydrochloric acid (protein digestion)
Why does the stomach have strong acidity? What pH is maintained? -Prevents bacterial growth & kills most bacteria that enter w/ food. -below 2 on the pH scale [gastric juice]
How does body protect stomach? The cells of the stomach wall secrete mucus.
[In the stomach] What happens to salivary enzymes? other enzymes? Sal. enzymes do not work in acid this strong [pH: 2], they become other proteins to be digested. -Stomach enzymes work best in strong acid.
As food leaves stomach what happens to pH? How is this done? Pancreatic juice neutralizes the acidic chyme arriving in the small intestine from the stomach; from then on, chyme is neutral or slightly alkaline pH.
After food leaves stomach what other enzymes are provided? What are their sources? -Pancreas gives pancreatic juice contains enzymes -Cells of intestinal wall also produce digestive enzymes on their surfaces
What is bile? What is its source & purpose? -Bile is an EMULSIFIER; brings fats into suspension in H2O so that enzymes can break them down into components. -Liver produces bile - stored in gallbladder
What happens to fiber? What is its function? Some fibers are not absorbed; continue through tract carrying minerals, bile acids, additives & contaminants out of the body. Also retains H2O, accounting for consistency of stools.
What happens in the colon? Intestinal bacteria ferment some fibers, producing water, gas & small fragments of fat
What is absorption? -The retrieval of carbohydrates, protein, fats, vitamins & minerals from digesting food.
How do the nutrients get across the intestinal wall/describe anatomy of intestinal wall -Hundreds of folds in intestinal wall, contoured into thousands of finger-like projections. These are villi. -A single villus is composed of hundreds of cells - each covered in microscopic hairs [MICROVILLI]
Crypts Crevices btwn villi lie in the crypts: tubular glands that secrete intestinal juices into the small intestine.
Goblet cells -secrete mucous -glandular simple columnar epithelial cells whose sole function is to secrete mucin, which dissolves in water to form mucus. They use both apocrine and merocrine methods for secretion.
What nutrients are absorbed into the capillaries of the blood stream where they are sent? -water soluble nutrients & smaller products of fat digestion & guided to liver -larger fats & fat-soluble vitamins insoluble in H2O cluster to form CHYLOMICRONS.
What nutrients are absorbed into the lymph system? Where are they sent? -large fats & fat soluble vitamins -once inside vascular system, nutrients travel freely to any destination.
What is the purpose of the vascular system? - closed system of vessels through which blood flows continuously, with the heart as the pump. as blood moves thru system it picks up & delivers materials as needed
What happens to blood leaving the digestive system? Blood leaving goes thru the hepatic portal vein- which directs blood to the liver - branches into capillaries then collects into the hepatic vein- returns blood to the heart.
What organ first receives nutrients absorbed from the GI tract? The liver first receives the nutrients
What are some of the roles of the liver? -bodys major metabolic organ, defends body by detoxifying substances, preparing waste products for excretion
What is the purpose of he lymphatic system? How does it ultimately enter the blood stream? -1-way route for fluid from tissue spaces to enter blood. Lymph circulates between cells & collects into tiny vessels. -Fluid moves thru body as muscles contract/create pressure; lymph ends in thoracic duct behind heart which opens to subclavian vein
What factors can affect normal GI functions? -bacterial/hormonal regulation/peristalsis and sphincter action poorly coordinated/ diseases/ lack of nourishment/young age/ aging/illness/nutrition
GI tract health depends on.. -adequate nutrition
What is homeostasis? How does body maintain/regulate it? -the maintenance of constant internal conditions by the body's control systems. -hormonal (endocrine) & nervous system
what are hormones? -chemical messengers secreted by a variety of glands in response to altered conditions of the body - travels to specific areas where it elicits a specific response to maintain homeostasis.
What are the roles of secretin? stimulates the pancreas to release bicarbonate rich juices that neutralize the chyme.
What is the role of CCK? Cholecystokinin hormone -when fat is present in the intestine, CCK is the messenger that tells gallbladder to squirt bile to emulsify fat.
Created by: bgodbey