Physics | Biology | Medicine | Anatomy | Chemistry
Anatomy
The plain idea
Anatomy is the study of the structure of living bodies: what parts there are, where they sit, and how they are built. Its partner, physiology, studies how those parts work. Anatomy is the map; physiology is the traffic.
The word comes from the Greek anatome, “cutting up”, because for most of history the only way to learn it was dissection. Today we also look inside living people with X-rays, ultrasound, CT and MRI, without cutting at all.
Why it matters
You live in your body every day and most of us know astonishingly little about it. Knowing the basic layout helps you understand what a doctor tells you, notice when something is wrong, train and stretch without injuring yourself, and see through health claims that make no anatomical sense.
Historically, anatomy was where medicine became a science. For over a thousand years European doctors followed Galen (2nd century CE), much of whose anatomy came from dissecting animals. In 1543 Andreas Vesalius published De humani corporis fabrica, based on careful human dissection, and corrected hundreds of Galen’s errors. In 1628 William Harvey showed the blood circulates, pumped by the heart. Looking carefully beat trusting authority. That is a lesson far beyond medicine.
An everyday analogy: a city
Think of the body as a city.
- Skeleton – the buildings’ steel frames (206 bones in an adult).
- Muscles – the cranes and engines, over 600 of them.
- Circulatory system – roads and delivery trucks: heart, arteries, veins, capillaries.
- Respiratory system – the air supply: lungs and airways.
- Digestive system – the food markets and processing plants.
- Nervous system – the telecoms network, with the brain as the control centre.
- Endocrine system – the postal service: hormones carried in the blood.
- Immune and lymphatic systems – police and sanitation.
- Kidneys and urinary system – water treatment.
- Skin – the city wall, and the body’s largest organ.
A worked example: the spleen
Since the spleen is where my own curiosity started (see below), let’s do it properly.
- Where: upper left abdomen, tucked under the ribs behind the stomach, roughly the size of your fist (about 12 cm long, around 150 g in an adult).
- What it does: it filters the blood. Its red pulp removes worn-out red blood cells (which live about 120 days) and recycles their iron. Its white pulp is immune tissue, full of lymphocytes, that recognises bacteria in the blood, especially encapsulated bacteria such as pneumococcus. It also holds a reserve of platelets and monocytes.
- Can you live without it? Yes. After a splenectomy (often due to injury, since its position and blood supply make it vulnerable in car crashes and contact sports) the liver and other tissues take over much of the filtering. But the risk of serious infection rises for life, which is why people without a spleen are given extra vaccinations.
So: an organ most people can’t locate, quietly helping recycle the two million or so red blood cells your body retires every second.
- The Spleen
Silly me, never knew what the spleen is. Click the link above to find out! The spleen is an organ in the upper far left part of the abdomen, to the left of the stomach. Old red blood cells are recycled in the spleen, and platelets and white blood cells are stored there. The spleen also helps fight certain kinds of bacteria that cause pneumonia and meningitis.
Some numbers worth knowing
- The heart beats roughly 100,000 times a day and pumps about 5 litres of blood a minute at rest.
- Laid end to end, the body’s blood vessels would stretch something like 100,000 km, mostly capillaries.
- The small intestine is about 6–7 m long in a living adult; its folds and villi give it a surface area of roughly 30 m², about half a badminton court.
- The brain is about 2% of body weight but uses about 20% of resting energy.
Common misconceptions
- “We only use 10% of our brain.” Brain scans show activity throughout the brain; there is no idle 90%.
- “The appendix is useless.” It appears to act as a reservoir for helpful gut bacteria and has immune tissue. You can live without it, as with the spleen, but “useless” is wrong.
- “Blood is blue inside the body.” It is always red: bright when oxygen-rich, darker when not. Veins look blue because of how skin scatters light.
- “Each part of the tongue tastes one flavour.” The “tongue map” came from a mistranslation of a 1901 German paper. All taste areas detect all basic tastes.
How it connects
The truth revealed: you carry the most intricate machine you will ever own, and it comes with no manual. Anatomy is the manual.