Digestion and Absorption Flashcards
Goal
turn food into energy
Challenges associated
Keeping the food moving
protecting the cells
suspended things in liquid
removing liquid
Excreting but not continuously
get nutrients out of food
Nutrition
process of taking in food and using it for growth, metabolism, and repair
-ingestion
-digestion
-absorption
-transport
-assimilation
-excretion
ingestion
taking food and drink into the mouth
digestion
breakdown food
-mechanical-physical breakdown of food
-chemical-enzymatic breakdown of chemical bonds from complex to simple
absorption
moving nutrients and digested products from lumen of GI tract into the circulatory system (blood and lymph)
transport
distribution of absorbed nutrients around the body via the circulatory system (blood and lymph)
assimilation
incorporation of newly acquired nutrients into body cells and tissues
-growth, metabolism, repair
-uptake from blood stream
Excretion
elimination of indigestible and waste products from body
GI tract
25-30 feet long muscular tube that makes the digestive tract
-5 organs
Sphincters
smooth muscle that opens and close regions of the tract controlling food movement from one organ to the next
-respond to stimuli from nerves, hormones, and pressure
Digestion begins in the mouth
mechanical and chemical digestion
-saliva: dissolves small food particles, contains water, mucus, electrolytes, immunoglobulins, and few enzymes (cirrus=water)
-Tongue: 5 taste buds, sense of smell helps us differentiate
-chewed food gets pushed to pharynx to be swallowed
Esophagus
-transport bolus and fluids to stomach
-upper esophageal sphincter: allows bolus to enter (not voluntary)
-Lower esophageal sphincter: allows the bolus of food to enter the stomach
-changes from skeletal to smooth muscle
Stomach
-empty 1 cup but can go to 1 gallon
-minimal absorption (water, alc, some drugs)
-3 layers of muscle allow for mashing
-secretes gastric juices (water enzymes(pepsin and lipase) HCL and mucus)
HCL: assist protein digestion, from parietal cells, acidity prevents bacterial growth and stomach enzymes work best in a low PH
Chyme
partially digested food
-leaves stomach and enters the small intestine vis pyloric sphincter
-salivary enzymes get broken down and reabsorbed
feedback loop
chyme is released.
-acidity signals small intestine cells stimulate contraction of pyloric sphincter
-bicarb neutralizes environment of small intestine
-pyloric sphincter relaxes
-chyme is released
Chemical Digestion
enzymes
-proteins that facilitate chem rxns as a catallyst but remain unchanged
-use hydrolysis
-water breaks bond
3 required conditions for enzymes
- compatible enzyme and nutrient are both present
- temp of environment is optimal
3.pH of surroundings must be in optimal range
gastrointestinal hormones
gastrin, CCK, ghrelin, leptin
-activate 2nd messenger system to carry out the task usually in form of ATP or Ca
Small Intestine
Duodenum, Jejunum, ileum
-3-10hrs
-mech and chem
-10 feet long surface is highly specialized for absorption
Absorption: SI
villi and microvilli maximize absorption
-between villi are crypts that secrete juices, goblet secrete mucus
-villi have muscles that wave
-membranes have enzymes and pump specific to select nutrients
Gastric Motility
-helps propel food along by strong muscular contractions
-peristalsis: squeezes food forward through GI tract
-Segmentation: shifts food back and forth to increase likely hood of absorption
Liver
Largest internal organ
-essential in CHO metabolism
-makes proteins
-hepatocytes make bile
-site of alc metabolism
-removes toxins and hormones
-synthesizes bile: acts as emulsifier (suspends fat so enzymes can access)
Gallbladder
-liver send bile via the common hepatic duct
-stores and concentrates bile
-releases bile to small intestine via common bile duct
-liver can still secrete if gallbladder is removed
pancreas
exocrine gland: secretes digestive enzymes into small intestines (duct)
Endocrine: releases hormones to maintain blood glucose levels, insulin and Glucagon (blood stream)
Small Intestines
-pancreas juices come into duodenum
-bicarb neutralizes stomach acid to prevent damage to absorptive surfaces of the jejunum
-enzymes for CHO, fat, PRO
Blood and Lymph receive nutrients
carbs and pros are absorbed directly into blood stream- straight to liver
-fat-soluble nutrients are absorbed into the lymp system first, then delivered to blood
illeoceal valve
controls flow from the small intestine to the large intestine,
Large Intestine
abosrbs water and electrolytes
-cecum
colon
rectum
-1 L of fluid is gradually reduced to 200g of brown fecal material
-bile being metabolized by gut bacteria turns it brown
Fiber
some fibers can not be digested and absorbed
-carry minerals, bile, additives, and contaminants out of body
-semi solid mass helps exercise the GI muscles
-bacteria in colon ferment some fibers into simpler compounds
Defecation
internal anal sphincter-smooth muscle
external sphincter-skeletal muscle
