Ch. 3 Digestion, Absorption, & Transport Flashcards
Define digestion. What is the goal of digestion? What are the “absorbable units?”
Def: Process by which food is broken down into absorbable units.
Goal: break down food into absorbable units.
Absorbable Units:
- -CHO: fructose, glucose, galactose
- -PRO: dipeptides, AA
- -FAT: monoglycerides, fatty acids, glycerol
Familiarize yourself with the anatomy of the digestive tract.
So, you should go study your anatomy notes on the digestive system right now. :)
Digestive system: Mouth Stomach Small Intestine Large Intestine Liver Gallbladder Pancreas
Describe the role of the mouth in digestion.
Chews and mixes food with saliva.
Describe the role of the stomach in digestion.
Churns, mixes, and grinds food into a liquid mass: adds acid, enzymes, and fluid.
Describe the role of the small intestine in digestion.
Secretes enzymes that digest all energy-yielding nutrients to small nutrient particles; cells of wall absorb nutrients into blood and lymph.
Describe the role of the large intestine in digestion.
Absorbs water and minerals; passes waste (fiber, bacteria, and unabsorbed nutrients) along with water to the rectum.
Describe the role of the liver in digestion.
Manufactures bile salts, detergent-like substances, to help digest fats.
Describe the role of the gallbladder in digestion.
Stores bile until needed.
Describe the role of the pancreas in digestion.
Manufacture enzymes to digest all energy-yielding nutrients and releases bicarbonate to neutralize acid chyme that enters the small intestine.
How are CHO, PRO, and FAT digested in the mouth?
CHO: salivary amylase beings CHO digestion.
PRO: no digestion
FAT: lingual lipase. Little fat digestion.
How are CHO, PRO, and FAT digested in the stomach?
CHO: stomach acid inactivates salivary amylase, stops CHO digestion.
PRO: Parietal cells (secrete HCl):
–uncoils PRO (increasing surface area), activates pepsinogen to pepsin
Goblet cells (secretes mucus which helps protect stomach from HCl)
Chief Cells: secrete pepsinogen
FAT: little fat digestion
How are CHO, PRO, and Fat digested in the small intestine?
CHO: digestion resumes.
- Pancreatic amylases (from pancreatic duct to duodenum)
- brush border amylases (on surface of intestinal cells)
- ->intestinal maltase: maltose breaks down into glucose + glucose
- ->intestinal sucrase: sucrose breaks down into glucose + fructose
- ->intestinal lactase: lactose breaks down into glucose + galactose
PRO: pancreatic proteases, intestinal proteases
FAT: Bile (emulsifier), pancreatic lipases, intestinal lipases
What is the role of saliva in the digestive process?
Contains water, salts, and enzymes. Helps moisten food, begins CHO digestion.
What is the role of enzymes in the digestive process?
Catalysts, proteins.
Identified by organ they come from and compound they work on.
What is the role of bile in the digestive process?
Emulsifier:
–brings fat into suspension in water so that enzymes can break down the fat.
What is the role of bicarbonate in the digestive process?
Neutralizes acidic gastric juice
What is the role of HCl in the digestive process?
Acts primarily in protein digestion.
Define sphincter. What is the role of the esophageal and the pyloric sphincters?
Def: A circular muscle surrounding, and able to close, a body opening. Sphincters are found at specific points along the GI tract and regulate the flow of food particles
Esophageal sphincter: allow passage from mouth to esophagus and from esophagus to stomach; prevent back flow from stomach to esophagus and from esophagus to mouth.
Pyloric sphincter: allows passage from stomach to small intestine; prevents back flow from small intestine.
Explain the role of the following types of muscular action in the digestive process: peristalsis, stomach action, segmentation, & sphincter contractions.
Peristalsis: wavelike muscular contractions of GI tract that push its contents along.
Stomach Action: circular, longitudinal, and diagonal muscles.
Segmentation: circular muscles of intestines contract and squeeze contents
Sphincter Contractions: periodically open and close, allowing the contents of the GI tract to move along at a controlled pace
Describe the unique environment of the small intestine, which makes it conducive to absorption.
Folds: increase surface area of small intestine
Vili: fingerlike projections from the folds of the small intestine
Crypts: tubular glands that lie between the intestinal villi and secrete intestinal juices into the small intestine.
Microvilli: tiny, hairlike projections on each cell of every villus that can trap nutrient particles and transport them into the cells.
Unstirred water layer: around microvilli, help hold nutrients in place by microvilli in order to get absorbed
Goblet cells: cells of the GI tract (and lungs) that secrete mucus
Discuss the role of small and large intestine in absorption.
Small intestine: much of absorption occurs here; nutrients
Large intestine: reabsorption of water and electrolytes
Compare the absorption and transport of the 3 macronutrients.
Absorption: digested, waiting to be absorbed until reaching small intestine [where it’s absorbed]
Transport: Water-soluble nutrients and small fats go to liver before being transported to other cells. Fat soluble nutrients enter lymphatic system.
Where are the 3 classes of micronutrients absorbed?
Micronutrients are released from food by digestion and then absorbed mainly in the small intestines. A little bit is absorbed in the stomach and large intestines, but mainly in the small intestines.
During the process of absorption, nutrients that come from the food pass through channels in the small intestine into the bloodstream. The blood works to distribute these nutrients to the rest of the body.
Micronutrients/Macronutrients/Fiber and absorption
Macronutrients: digested, waiting to be absorbed
Micronutrients: waiting to be absorbed
Fiber: not absorbed
A modifiable risk factor to decrease ETOH absorption is….
to sip your drink
Gastric Absorption
- Limited
- Small amount of water absorbed
- ETOH: presence of food slows process of ETOH absorption
GI Bacteria and the benefits
•10 trillion bacteria, 400+ different species
•like neutral pH of small/large intestines
–> stomach not conducive, too acidic
•Important functions: digest some fiber, produce some vitamins
→ Table 3.1 (hormone regulation in GI tract)
Transportation
- Water-soluble nutrients and small fats go to liver before being transported to other cells
- Fat-soluble nutrients enter lymphatic system
Describe the role of gastrin, secretin and CCK in the digestive and absorptive process.
***hormones
Gastrin: responds to food in stomach –> stimulates the stomach glands to secrete the components of hydrochloric acid
Secretin: responds to acidic chyme in small intestine –> stimulates the pancreas to release its bicarbonate-rich juices –> to reduce acidity
CCK: responds to fat/protein in the small intestine ->
- travels by way of the blood –> gallbladder and stimulates it to contract, which releases bile into the small intestine.
- CCK –> pancreas, stimulates it to secrete its juices, which releases bicarbonate and enzymes into the small intestine
Dry Mouth: causes, consequences, and treatment
often result of decreased saliva production
Causes: meds, cancer tx (chemo, radiation), nerve damage
Consequences: tooth decay, mouth sores, poor nutrition (if chewing/swallowing impacted)
Treatment: depends on cause… o Adjust meds o Meds to stimulate saliva production o Sip water o Sugar-free gum, sugar-free candy (watch xylitol, can cause diarrhea) o Avoid caffeine and ETOH o Avoid tobacco
