Science · Beginner
The Human Body Explained
Skeleton, muscle, heart, lungs, brain, gut, immunity, hormones and the senses.
What you will learn
The 9 topics inside The Human Body Explained
Each topic has its own goal, its own questions and its own mastery score, so you always know which part is still weak.
Skin and the senses
Explain how skin and the sense organs gather information.
The circulatory system
Trace blood through the heart, lungs and body and explain what the numbers mean.
The digestive system
Trace how food is broken down and nutrients absorbed.
The endocrine system
Describe how hormones regulate the body's processes.
The immune system
Explain how the body detects and defeats pathogens, and what immunity means.
The muscular system
Describe how muscles contract and how they adapt to training.
The nervous system and brain
Describe how the brain and nerves control the body.
The respiratory system
Explain gas exchange and the mechanics of breathing.
The skeletal system
Explain what bones do beyond support and how the skeleton changes over life.
Example questions
Real questions from this course
These are taken straight from the course. Pick an answer, then open the explanation to see why it is right.
Sample 01
How does the stomach protect its own tissue from being eroded by its highly acidic environment?
Show the answer and why
Answer: Epithelial cells secrete a thick mucus coating that shields the wall from acid and digestive enzymes.
Foveolar cells produce a bicarbonate-rich mucus barrier that shields gastric mucosa from autodigestive acid. This refutes the misconception that spicy food permanently damages the stomach lining, which is actually caused by factors like Helicobacter pylori or NSAIDs.
Specialized epithelial cells in the stomach wall secrete a thick mucus coating that forms a protective barrier against gastric acid and pepsin. Stomach damage like ulcers is typically caused by bacterial infection or medications rather than spicy food.
Sample 02
What primary endocrine function does the pancreas perform in maintaining metabolic homeostasis?
Show the answer and why
Answer: The pancreas secretes insulin and glucagon to balance blood sugar levels in response to cellular energy needs.
This clarifies the specific hormonal role of the endocrine pancreas in blood sugar balance, contrasting it with misconceptions about stress or thyroid hormones.
The pancreas secretes insulin and glucagon directly into the bloodstream to balance systemic blood glucose levels. Insulin promotes glucose storage when blood sugar rises, while glucagon stimulates glucose release when blood sugar falls.
Sample 03
What specific role does adenosine triphosphate (ATP) play during the cross-bridge cycle of muscle contraction and detachment?
Show the answer and why
Answer: ATP binding causes myosin heads to detach from actin so the cross-bridge cycle can reset.
ATP binding is required to break the actin-myosin cross-bridge, allowing the cycle to reset. Without ATP, myosin remains firmly attached, as seen in rigor mortis.
The binding of a new ATP molecule allows the myosin head to detach from actin after the power stroke. ATP hydrolysis then re-energizes the myosin head so it can reattach to actin and repeat the cycle.
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