Lecture 3 - Digestion, Absorption and Transport Flashcards Preview

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What are the 3 processes that food undergo when we eat it?



What is the GI tract?

Series of organs arranged as a long tube
-from the mouth to the anus


What are the 2 components that make up the GI tract?

Organs (stomach, intestines)

Sphincters (muscles that control the passage if material from one organ to the next)


What are challenges of the digestion process?

Multi-taskis of the mouth
Steady movement
Lubrication of food
Digestive Enzyme functions
Management of waste


What is digestion?

The process of breaking large food molecules down to smaller molecules


What are the 2 ways in which we can digest food?

Mechanical via chewing and peristalsis

Chemical via enzymes and acids


What re the 3 phases of digestion?

1. Cephalic Phase- mouth (the thought of food, smell taste, chewing and swallowing)

2. Gastric - Stomach

3. Intestinal - Intestines


How does digestion start in the mouth?

Chewing and grinding of food.
Saliva moistens food
Salivary amylase starts comical digestion of carbs


What are the 2 phases of swallowing you do voluntarily?

Oral preparatory phase ( formation of the bolus)

Oral transit phase ( bolus moves from the front to the back of your mouth for passage to the pharynx)


What is the Pharyngeal Phase?

Involuntary process that closes the nasal passage, tongue base to posterior pharyngeal wall contact, contraction of muscles, closure of epiglottis and opening of upper esophageal sphincter


How does the bolus move to the esophagus?

Through the upper esophageal sphincter


How does the bolus move down the esophagus?

Peristalsis moves the bolus down the esophagus to the stomach
-movement is also aided by gravity


What is peristalsis?

Waves of squeezing and pushing contractions by muscles that move food through the GI tract


What separates the stomach from the esophagus?

The lower esophageal sphincter
(cardiac sphincter, where people feel heartburn)


Why do people get heartburn?

When stomach juices get past the lower esophageal sphincter. The pH is so low i hurts and can cause damage to the tissue


Does chemical or mechanical digestion occur in the stomach?

Chemical digestion of proteins and fats

Mechanical digestion to mix food with gastric juices


Where does gastric juices come from?

Secreted by the gastric glands


What is gastric juice composed of?

HCl- denature proteins and activate pepsin
Pepsin- digest protein
Gastric lipase- digest fat
Mucus-protect stomach lining


What is Chyme?

Semi-solid product of mechanical and chemical digestion in the stomach


How does food from the top of the stomach get to the small intestine?

Peristalsis breaks down the food, mixing it with the gastric juices. When it breaks down it starts to drop to the bottom.


Why doesn't chyme burn the small intestine?

When chyme enters the small intestines, the pancreas releases bicarbonate to neutralize the acidic chyme


How does food get out of the stomach?

Slowly through the pyloric sphincter


What are the 2 different movements of peristalsis?

P: continuous steady movement 9sneak eating food)

S: starting of the mechanical squeezing of the food products to become available for digestion

-combination of the 2 breaks down the chyme into small pieces


What are the 3 accessory organs to digestion?

Liver - makes bile
Gall bladder - stores bile
Pancreas - makes digestive enzymes and bicarbonate


Why is liver bile important for digestion?

Bile acts as an emulsifier which helps digest fat


What happens when people don't have a gall bladder?

You are unable to digest higher quantities of fat


What is to note about the enzymes in the pancreas?

Pacrease produces enzymes but in the inactive form, they are only the precursors. When the enzymes hit the right pH in the intestine they are released


What are the 4 sphincters, where are they and what are they meant to do?

Upper esophageal: opens in response to swallowing

Lower esophageal: prevents reflux of stomach contents

Pyloric Sphincter: holds chyme in stomach to be mixed and prevents intestinal contents from coming back up

Ileocecal Sphincter: Allows emptying of small intestine contents into large intestine


What is absorption?

The process of taking molecules across a cell membrane and into cells of the body


Where does most absorption take place in the body?

Small intestines
-a little in the stomach (water, alcohol)