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Nutrition CH5- WK2

Digestion, absorption, and metabolism

Digestion process in which food is broken down in the GI tract, releasing many nutrients in forms the body can use
absorption process in which nutrients are taken into the cells lining the GI tract
transport movement of nutrients through the circulatory system from one area of the body to another
metabolism the sum of the vast number of chemical changes in the cell, the functional unit of life, which finally produces the essential materials necessary for energy, tissue building, and metabolic controls
GI motility peristalsis - Beginning in the mouth, muscles and nerves in the tract coordinate their actions to provide motility, an automatic response to the presence of food.
Muscles tone/tonic contraction: Ensures continuous passage of the food mass and valve control along the way; Rhythmic waves that mix the food mass and move it forward
Nerves intramural nerve plexus is the network of nerves in the GI wall extending from the esophagus to the anus; Controls muscle tone in the GI wall; in charge of peristalsis
Digestive enzymes break down nutrients
Hydrochloric acid and buffer ions Produce the correct pH necessary for enzyme activity
Mucus Lubricates and protects the GI tract tissues and helps mix the food mass
Water and electrolytes Carry and circulate the products of digestion through the tract and into the tissues
Bile Divides fat into smaller pieces to assist fat enzymes
Mechanical digestion Mastication breaks down food. Food is swallowed and passes down esophagus. Muscles at tongue base facilitate process. Gastroesophageal sphincter at stomach entrance relaxes, allowing food to enter, then constricts to retain food.
Chemical digestion Salivary glands secrete material containing salivary amylase or ptyalin. Ebner’s glands at the back of the tongue secrete a lingual lipase Salivary glands also secrete a mucous material to lubricate and bind food particles, facilitating the swallowing o
salivary amylase breaks down starch
lingual lipase secreted by Ebner's glands; breaks down fats
Mechanical digestion Under sphincter control, the food enters the upper portion of the stomach as individual bolus lumps; Stomach muscles knead, store, mix, and propel the food mass forward. By the time the food mass reaches the lower portion of the stomach, it is a semiliqu
Chyme semifluid food mass in the GI tract present after gastric digestion
Pepsin main gastric enzyme specific for proteins.
pancreatic amylase major starch-splitting enzyme secreted by the pancreas that acts in the small intestine
trypsin protein-splitting enzme formed in the small intestine. The inactive precursor trypsinogen is activated by enterokinase
chymotrypsin one of the protein-splitting and milk-curdling pancreatic enzymes activated in the small intestine
carboxypeptidase protein enzyme that splits off the chemical group carboxyl (-COOH) at the end of peptide chains
pancreatic lipase major fat-splitting enzyme produced by the pancreas and secreted into the small intestine to digest fat
Hydrochloric acid Parietal cells in the stomach lining secrete acid to promote gastric enzyme activity.
Mucus Secretions protect the stomach lining from the erosive effect of the acid and also bind and mix the food mass and help move it along.
Enzymes Pepsinogen is secreted by stomach cells and activated by acid to become pepsin, a protein-splitting enzyme.
Mechanical digestion in the small intestine Peristaltic waves slowly push food mass forward- protein breakdown in the stomach d/t pepsin; Pendular movements sweep back and forth. Segmentation rings chop food mass into successive soft lumps and mix them with secretions; Longitudinal rotation rolls
Bile Emulsifying (melting) agent produced by the liver and stored in the gallbladder aids fat digestion and absorption.
Secretin hormone that balance ph of small intestine – for everything to work – pH needs to be 8
Cholecystokinin hormone triggers release of bile from gallbladder
Bioavailability refers to how well the body can use the nutrients; It is the “gatekeeper” that determines how much of the a nutrient is used by the body.
Mucosal folds Surface of small intestine piles into folds
Villi Small, finger-like projections cover the mucosal folds, increasing the area of exposed intestinal surface
Microvilli Smaller projections cover each villi (look like bristles on a brush)
Simple diffusion The force by which particles move outward in all directions—from areas of greater to lesser concentration.
Facilitated diffusion Similar to simple diffusion but uses a protein channel to carry larger items.
Active transport The force by which particles move from areas of greater to lesser concentration using a carrier to “ferry” particles.
Pinocytosis Penetration of larger materials by attaching to the cell membrane and being engulfed by the cell.
Dietary fiber not digested Contributes bulk to food mass; Helps form feces
Vascular (blood circulatory) system transport Transports waste, such as carbon dioxide and nitrogen, to lungs and kidneys for removal; veins and arteries
Lymphatic system transport Route for fatty materials, which are not water soluble Fat molecules pass into lymph vessels in villi Portal Circulation – transports nutrients to the liver – then travels to all cells in the body
Metabolism The sum of body processes that change our food energy from the three energy nutrients; Chemical reactions within cell to maintain life; Occurs in mitochondrion of the cell
adenosine triphosphate (ATP) cellular energy.
Glycogenesis Anabolic process of converting extra glucose into glycogen Glycogen is stored in the liver and muscles for quick energy to be used at a later time
Lipogenesis The building up of triglycerides for storage in adipose tissue
Lactose Intolerance Most common disaccharidase deficiency-lactose intolerance Lactase in insufficient amounts, not absent Causes abdominal cramping and diarrhea
Created by: MarieG