## TL;DR
Human anatomy studies the structure of the body. 11 organ systems — skeletal, muscular, nervous, circulatory, respiratory, digestive, endocrine, urinary, reproductive, lymphatic, integumentary — work in coordinated integration.

## Core Explanation
Major systems: nervous system (brain, spinal cord, nerves — rapid electrical signaling), cardiovascular (heart pumps blood through arteries → capillaries → veins), respiratory (lungs exchange O₂/CO₂ across 70 m² of alveolar surface), digestive (mouth to colon, ~9m tract).

## Detailed Analysis
The brain (~1.4 kg, 86 billion neurons) consumes 20% of the body's oxygen. Neurons communicate via synapses — electrical signals trigger neurotransmitter release. The liver (~1.5 kg) performs 500+ functions including detoxification, protein synthesis, and glycogen storage.

## Further Reading
- Visible Body: 3D Anatomy Atlas
- Khan Academy: Human Anatomy
- NIH: Visible Human Project