## TL;DR

Human anatomy is the study of body structure. Systems: skeletal (206 bones, support), muscular (600+ muscles, movement), nervous (brain, spinal cord, nerves), cardiovascular (heart, blood vessels), respiratory (lungs, gas exchange), digestive, endocrine (hormones), immune, urinary, reproductive.

## Core Explanation

Brain: ~86 billion neurons, consumes 20% of body's energy. Heart: pumps 7,000 liters of blood daily, beats ~100,000 times. Lungs: 300 million alveoli for gas exchange, surface area ~75 m². Bones: strongest is femur (can support 30x body weight), smallest is stapes (ear, 3mm). DNA in each cell: ~2 meters if stretched — body contains ~70 round trips to the sun of DNA. Liver: only organ that can regenerate.

## Further Reading

- [Gray's Anatomy (41st Edition)](https://www.elsevier.com/books/grays-anatomy/standring/978-0-7020-5230-9)