Biology: Digestive System

Study Notes

The digestive system is a complex process by which the body breaks down and absorbs nutrients from food
Involves mechanical and chemical breakdown of food, absorption of nutrients, and elimination of waste products

Mouth:
- Food is chewed and mixed with saliva that contains enzymes to break down carbohydrates
- Swallowing transports food to the esophagus
Esophagus:
- Muscular tube that propels food to the stomach through peristalsis
Stomach:
- Food is mixed with stomach acid and digestive enzymes to break down proteins and fats
- Gastric juices contain pepsin and hydrochloric acid
Small Intestine:
- Most nutrient absorption occurs here
- Walls are lined with finger-like projections called villi, increasing surface area for absorption
- Nutrients are absorbed into bloodstream and transported to liver for processing
Pancreas:
- Produces digestive enzymes and bicarbonate-rich fluids to neutralize stomach acid
Liver:
- Processes and filters nutrients from small intestine
- Regulates glucose levels and stores glycogen
Large Intestine (Colon):
- Water and electrolytes are absorbed, and waste is prepared for elimination
- Houses trillions of microorganisms, the gut microbiome

Mechanical Breakdown:
- Chewing and grinding of food in the mouth
- Contractions of stomach muscles to mix food with digestive enzymes
Chemical Breakdown:
- Enzymes break down carbohydrates, proteins, and fats into simpler molecules
- Hydrolysis reactions cleave chemical bonds, releasing nutrients
Absorption:
- Nutrients are absorbed into bloodstream through intestinal walls
- Transported to liver for processing and distribution to the body

The digestive system is responsible for breaking down and absorbing nutrients from food, involving mechanical and chemical breakdown, absorption, and waste elimination.

Mouth:
- Breaks down carbohydrates through chewing and mixing with saliva containing enzymes
- Food is swallowed, transporting it to the esophagus
Esophagus:
- Propels food to the stomach through peristalsis, a muscular tube action
Stomach:
- Mixes food with stomach acid and digestive enzymes to break down proteins and fats
- Gastric juices contain pepsin and hydrochloric acid
Small Intestine:
- Most nutrient absorption occurs here, with walls lined with villi for increased surface area
- Absorbed nutrients are transported to the liver for processing
Pancreas:
- Produces digestive enzymes and bicarbonate-rich fluids to neutralize stomach acid
Liver:
- Processes and filters nutrients from the small intestine
- Regulates glucose levels and stores glycogen
Large Intestine (Colon):
- Absorbs water and electrolytes, preparing waste for elimination
- Houses trillions of microorganisms in the gut microbiome

Mechanical Breakdown:
- Involves chewing and grinding food in the mouth
- Stomach muscles contract to mix food with digestive enzymes
Chemical Breakdown:
- Enzymes break down carbohydrates, proteins, and fats into simpler molecules
- Hydrolysis reactions cleave chemical bonds, releasing nutrients
Absorption:
- Nutrients are absorbed into the bloodstream through intestinal walls
- Nutrients are transported to the liver for processing and distribution to the body