module 3 Flashcards
(20 cards)
two types of digestion
- mechanical/physical eg)grinding, chewing, stomach chruning. the bulk of it it done in the mouth
- chemical digestion-use of enzymes
hydrolysis vs condensation
Hydrolysis: Water is added to break a bond, splitting a molecule (e.g., breaking down a polymer).
Condensation: Water is removed as two molecules bond together, forming a larger molecule (e.g., synthesizing a polymer).
hormones
hormones are chemical messengers that are required fo digestion for example. they are released from one area of body and travel to diff prts
Key facts about the digestive tract
Long tube-like structure, technically starts outside the body (mouth → anus)
Sphincters regulate movement between sections
Takes ~2+ days for material to pass through
Food spends the most time in the large intestine
Transit time depends on activity, fiber intake, and medications
layers of the digestive tract
-mucosa – innermost layer, absorbs nutrients and secretes mucus
-submucosa – contains blood vessels, nerves, and lymph to support the mucosa
-muscularis – smooth muscle layer, controls movement and changes the diameter of the tract
-serosa – outermost layer, anchors and protects the digestive tract
first part of digestive tract: mouth
First part of the digestive tract
Teeth rip food apart, tongue pushes food & mixes it with saliva
Salivary glands secrete:
-Amylase (digests starch)
-Lingual lipase (digests lipids)
-Mucus (lubricates food)
-Lysozyme (antibacterial)
Food leaves the mouth as a bolus
bolus
chewed up food when it leaves the mouth
second part of digestive tract: the pharynx
Also called the throat, a common passageway for food and air. (posterior is esophagus)
Epiglottis directs food into the esophagus, preventing it from entering the trachea
No active digestion or absorption happens here
third part of digestive tract: the esophagus
-No active digestion or absorption
-Peristalsis moves food down (wave-like contractions of circular smooth muscle)
-Contracts behind the bolus to push it forward
fourth part of digestive tract: stomach
-Temporary reservoir for food (stays ~4-5 hours)
-Three muscle layers churn food
-Lower esophageal sphincter closes to prevent backflow
-Pyloric sphincter regulates food entry into the small intestine
-Mixes with gastric juices → becomes chyme (semi-liquid)
gastric juices
-Secreted by stomach cells
Contains:
-Mucus (lubrication & protection)
-Gastric lipase (breaks down lipids)
-HCl acid (creates acidic environment)
-Pepsinogen (inactive form of pepsin, activated by HCl in the stomach to break down proteins)
fifth part of digestive tract: small intestine
Primary site of digestion and absorption
Three sections: duodenum, jejunum, ileum
6 meters long
Villi and microvilli increase surface area (villi are large folds, microvilli secrete digestive enzymes)
Help with nutrient absorption and enzyme secretion
How do different nutrients get absorbed in the small intestine?
Water: Absorbed via osmosis
Lipids and fat-soluble vitamins: Use diffusion
Sugars (like glucose) and amino acids: Use protein transporters
Glucose and amino acids need energy because they use active transport
Lipids enter the lymph, while other nutrients enter the blood
What happens in the large intestine during digestion?
-1.5 meters long
-Colon is the main part (most of water absp happens here)
-Unabsorbed material is either:
–Packaged for removal (feces)
–Acted on by bacteria (fermentation of some materials)
What is the microbiome, and what roles do microbiota play in the body?
Microbiome: Genetic material of nonhuman organisms (bacteria, fungi, etc.) in our body
Microbiota: All nonhuman organisms living in our body, especially in the large intestine
Roles of microbiota:
-Vitamin synthesis (e.g., vitamin K, B vitamins)
-Energy harvesting (breaking down complex carbs)
-Immune health (modulating immune response)
-Disease prevention (barrier against harmful pathogens)
-Appetite regulation (influences hunger and food preferences
What are the accessory structures of the digestive tract, and what do they do?
Liver, gallbladder, and pancreas are accessory structures
They secrete materials into the duodenum of the small intestine
the pancreas
The pancreas secretes pancreatic juice into the small intestine
Pancreatic juice contains:
-Amylase (breaks down starch)
-Lipase (breaks down lipids)
-Protease (breaks down proteins)
-Bicarbonate (neutralizes acidic chyme from the stomach)
What is the role of the liver, gallbladder, and bile in digestion?
Liver: Produces bile
Gallbladder: Stores and releases bile
Bile: A lipid emulsifier, breaks down fats into smaller droplets to be suspended in a watery environment (aids in fat digestion)
How does bile help with fat digestion?
Bile contains bile salts with hydrophobic tails that surround lipids and hydrophilic heads that face water
This forms small fat droplets suspended in water, making it easier for lipases to break down the fats in the small intestine
Bile acts like a lipid emulsifier
cholecystokinin (cck) is released by the _________ and acts on the _________.
brain, stomach
small intestine, brain and stomach and accessory digestive organs
small intestine, accessory digestive organs
brain, small intestine and accessory digestive organs
Small intestine, brain and stomach and accessory digestive organs
