Digestive system: Anatomy and Disorders Part 1

Question 1

What are the roles of teeth?

Answer 1

-Teeth (mechanical digestion)
1. Incisors = biting
2. Canines = tearing
3. Premolars = mashing
4. Molars = crushing

Question 2

What are the roles of tongue?

Answer 2

-Tongue:
1. Positions food for chewing
2. Mixes food with saliva (bolus)
3. Helps in deglutition process
4. Produces lingual lipase (enzyme)

Question 3

Describe saliva and its role

Answer 3

Saliva:
-Salivary glands (3 pairs)
-Water + mucus + molecules + ions (slightly acidic)
-Salivary amylase and lingual lipase (enzymes)
Functions:
1. Moistens food (bolus)
2. Starts chemical breakdown (starch, triglycerides)
3. Cleans mouth and has antimicrobial properties
4. Dissolves food chemicals (taste)

Question 4

What is salivary amylase?

Answer 4

-Active in mouth and stomach
-Turn starch into maltose

Question 5

What is lingual lipase?

Answer 5

-Active in mouth and stomach
-Triglycerides digestion

Question 6

What is the pharynx?

Answer 6

-Links mouth to esophagus (passage)
-Not actively participating in digestion
-Role of uvula and epiglottis during deglutition

Question 7

What is the esophagus?

Answer 7

Long muscular tube linking pharynx to stomach
Active peristalsis inside (propulsion):
-Smooth muscles
-Allows the descent of the bolus
Ends with lower esophageal sphincter
-Malfunction = acid reflux (heartburn)

Question 8

What is the anatomy of the stomach?

Answer 8

-Starts at the lower esophageal sphincter
-Ends with pyloric sphincter
-Reservoir for boluses
-Thick walls made of 3 smooth muscle layers (additional oblique layer)

Question 9

How does the stomach participate in digestion?

Answer 9

-Churning (mechanical breakdown)
-Absorption of certain lipid-soluble substances (e.g.: alcohol and aspirin)
-Chemical digestion (gastric glands produce gastric juice)

Question 10

How does chemical digestion work for proteins?

Answer 10

-Pepsinogen (inactive) and hydrochloric acid (HCL)
-Pepsinogen becomes pepsin (active)
-Proteins into peptides (still too large in size for absorption by small intestine)

Question 11

How does chemical digestion work for lipids?

Answer 11

-Lingual lipase
-Gastric lipase is activated and starts lipid digestion

Question 12

What are the pros and cons of the stomach’s acidic pH?

Answer 12

Pros:
-Killing most pathogenic bacteria
-Protein denaturation (back to primary structure)
Cons:
-It may digest itself! Causes inflammation or gastritis

Question 13

What are the disorders linked to the stomach?

Answer 13

Peptic ulcers (gastric ulcers):
-Persistent damage to the protective mucus layer
-The culprits: Helicobacter pylori and some drugs
-Treatment: antibiotics or drug change

Question 14

How does the bolus is turned into chyme?

Answer 14

Chyme exit is controlled by pyloric sphincter:
-Little quantities at a regular pace
-Peristaltic waves
In the end:
-2 to 4 hours for the stomach to empty