Nutrition Test 2 (Chapter 3) - Shannon Crosby
how food travels through GI tract
- Food moves from one organ to the next by propulsion. Various sphincters along the way allow food to pass 1) begins in mouth 2) once chewed (mastication), the tongue rolls it into a bolus 3)tongue thrusts it into the pharynx to be swallowed, it then enters the esophagus through the upper esophageal sphincter 4) it then enters the stomach through the lower esophageal sphincter by peristaltic movements 5) LES keeps food in stomach
gastric juice
- HCL: destroy active proteins & harmful bacteria & viruses, and converts pepsinogen to pepsin - Protease: protein digesting enzyme that attacks bonds and breaks them into shorter chains - Pepsin: digests protein - Gastric lipase: digests fats - GIP: slows down emptying of stomach
diarrhea
abnormally frequent passage of watery stools
amylase
an enzyme that converts starch and glycogen into simple sugars
sphincter
circular rings of muscle that open and close in response to nerve input
where FAT is digested and absorbed
gastric lipase (stomach), pancreatic lipase (pancreas), lipase
Where does digestion and absorption occur?
gastrointestinal tract
constipation
infrequent passage of dry, hardened stools
accessory organs
liver, gallbladder, pancreas, salivary glands
pH of stomach
lower than that of other organs because of HCL; acidity is higher
organs of GI tract
mouth, pharynx, esophagus, stomach, and small/large intestines
passive diffusion (absorption in SI)
movement from high to low concentration
where PRO is digested and absorbed
pepsin (stomach), pancreas, di/tripeptidase
absorption
process of moving nutrients from GI tract into circulatory system
active absorption (in SI)
protein carrier & energy is used to move nutrients against a concentration gradient
facilitated diffusion (absorption in SI)
protein carriers move nutrients
where CHO is digested and absorbed
salivary amylase (saliva), maltase, lactose
role of mucus
secretion produced throughout the GI tract that moistens and lubricates food and protects membranes
Chyme
semiliquid, partially digested food mass that leaves the stomach and enters the small intestine
Bolus
soft mass of chewed food
ulcer
sore or erosion of the stomach or intestinal lining
ileocecal valve
sphincter that separates the small intestine from large intestine
Feces (stool)
- waste produced in the large intestine - consists of the undigested food residue, as well as sloughed-off cells from the GI tract and a large quantity of bacteria - 75% water, 25% solids
segmentation v. peristalsis
- Segmentation: muscular contractions of the small intestine that move food back and forth, combining it with digestive juices - circular muscles - Peristalsis: forward, rhythmic motion that moves food; mechanical digestion- longitudinal muscles
Endocytosis (absorption in SI)
- absorptive cell engulfs particles or fluid to form a vesicle which is taken in by the cell - 2 types 1) phagocytosis (solid) 2) pinocytosis (liquid)
pepsin
- active form of pepsinogen - begins the digestion of proteins in the stomach
colon
- another name for large intestine - subdivided into ascending, transverse, descending, sigmoid
cecum
- beginning of large intestine - receives waste from small intestine
heartburn
- burning sensation in the middle of the chest; involves esophagus - occurs in lower esophageal sphincter - acidic gastric juice from stomach flows back into esophagus (GERD - 2x or more a week) - 50% US adults
liver
- carbohydrate metabolism, produces proteins, and manufactures a yellow-green bile to break down fat (bile makes the feces a color) - removes and degrades toxins
protease
- classification of enzymes that catalyze the hydrolysis of proteins - protein-digesting enzymes
lipase
- digests fat - secreted by chief cells
nutrients in lymph system
- fat soluble nutrients and long chain fatty acids - later enter blood stream via lymph to thoracic duct which connects to the blood; then to liver/body tissues
rectum
- final 8 inch portion of large intestine - mass is pushed into rectum by peristaltic waves
celiac disease - treatments and symptoms
- genetic disease in which a hyperimmune response damages the villi of the small intestine when gluten is consumed - treatment: gluten-free diet symtoms: reoccurring abdominal bloating, cramping, diarrhea, gas, fatty and foul-smelling stools, weight loss, anemia, fatigue, bone or joint pain, and even a painful skin rash called dermatitis herpetiformis
Bile
- helps digest dietary fat - made in liver - absorbs A, D, E, K
gastrin
- hormone triggered by thoughts and presence of food - Prepares body for protein digestion - Increase HCl and pepsin to act upon the protein - released from stomach and upper duodenum
GIP (Gastric Inhibitory Peptide)
- inhibits the secretion of stomach acid and enzymes - slows down gastric emptying (1tsp. at a time) to prevent ulcers - realize in small intestine
small intestine - 3 parts & functions
- long, coiled chamber that is the major site of food digestion and nutrient absorption - 3 parts: duodenum (most digestion - 10in), jejunum (most absorption - 8ft), ileum (prepare food to be waste; bile reabsorbed here - 12 ft) - extends from pyloric splinter to valve at the beginning of the large intestine
large intestine - parts
- lowest portion of the GI tract, where water and electrolytes are absorbed and waste is eliminated; forms fecal matter; houses beneficial bacteria - parts: cecum, ileocecal valve, colon (ascending, transverse, descending, sigmoid), rectum
pancreas
- makes bicarbonate (neutralizes acidity), digestive enzymes (lipase, protease) - pancreatic amylase digests starch - pancreatic lipase digests fat - proteases digest protein
stomach - functions & layers
- mix food with various gastric juices to chemically break it down into smaller and smaller pieces - 4 layers: goblet cells and gastric pits, parietal cells, chief cells, and mucus - gallon size when full, cup size when empty
Digestive System
- movement, secretion, digestion, absorption, transportation, storage, elimination -role in immunity - 23 ft long muscular tube with primary and accessory organs
upper esophageal sphincter
- muscular ring located at the top of the esophagus - opens once food passes through the pharynx; allows bolus to enter into the esophagus
lower esophageal sphincter
- muscular ring located between the base of the esophagus and the stomach - where the esophagus ends - relaxes to allow the bolus to enter into the stomach
bacterial functions
- produces vitamins, ferments undigested and unabsorbed carbs (causes gas), breaks down undigested fiber into amino acids, lubricant for fecal matter, controls pathogens
Gastriontestinal tract
- purpose: digestion (breaking down foods into a form the body can use - mechanical and chemical) - mouth > anus
digestive enzymes
- recreated along GI tract, but most are produced in pancreas
secretin
- release in small intestine - act upon bicarbonate and digestive enzymes
enzymes
- speed of chemical reactions - most important role: accelerate hydrolysis (water breaks the bonds of digestible carbs, fats, proteins, and alcohol) - can be used over and over again - conditions for it to be present 1) compatible enzyme and nutrient must both be present 2) the pH of the environment must fall in the appropriate range 3) the temp of the environment must fall within the appropriate range (98.6)
CCK (cholecystokinin)
- stimulates the release of pancreatic enzymes and bile from the gallbladder - slows GI motility to give digestive enzymes time to aid absorption of nutrients - released in small intestine
gallbladder
- storage center for bile
Villi
- tiny folds and small, fingerlike projections that line the lumen of the small intestine - increase surface area to maximize absorption and help mix the partially digested chyme with intestinal secretions - lined with goblet cells that make mucus
Microvilli
- tiny projections on the villi in the small intestine - "brush border" - trap nutrients and absorb them into the enterocyte interior
nutrients in CV system
- water soluble nutrients (CHO, PRO, Vitamin B, Vitamin C) - short and medium chain fatty acids - absorbed directly into bloodstream - taken to liver via portal vein; leftovers from liver is transported to cells via blood