Welcome to Lesson 11 of the Human Biology Masterclass.
In this lesson, we apply everything we've learned about cells, molecules, and metabolism to one of the body's most important organ systems: the digestive system.
How does a meal become molecules that your cells can actually use? We follow the complete journey of food from the mouth to the large intestine, examining digestion, absorption, nutrient transport, and the role of the gut microbiome.
In this lesson, you'll learn:
• The complete gastrointestinal tract and the main function of each organ
• The difference between mechanical and chemical digestion
• What happens in the mouth, oesophagus, and stomach
• How gastric acid and pepsin begin protein digestion
• How the duodenum, jejunum, and ileum contribute to digestion and absorption
• The roles of pancreatic enzymes and bicarbonate
• How bile contributes to fat digestion through emulsification
• How the small intestine is adapted for nutrient absorption
• The structure and function of circular folds, villi, and microvilli
• How water-soluble and lipid-soluble nutrients enter different transport pathways
• How the liver processes nutrients absorbed from the intestine
• The functions of the pancreas and gallbladder
• How the large intestine reabsorbs water and electrolytes
• What the gut microbiome is and why it matters for human physiology
• The concept of the gut-brain axis and the relationship between the microbiome, immunity, and metabolism
The digestive system is much more than a tube that processes food. It is an integrated biological system involving mechanical forces, enzymes, hormones, transport mechanisms, immune function, and interactions with trillions of microorganisms.
Understanding digestion provides an essential foundation for studying nutrition, metabolism, energy balance, gut health, and human physiology.
Human Biology Masterclass
Lesson 11 marks the transition from molecular biology and metabolism to the study of major human organ systems.
Next lesson: Lesson 12 – The Nervous System: Electrical Communication in the Human Body
Continue the complete Human Biology Masterclass through the playlist on Human Science Academy.
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