What Is the Largest Organ in the Human Body? Skin or Liver?
What's the largest organ in the human body, and the largest internal organ? Learn about the skin and liver and what they do, plus a table of amazing body records.
If someone asked you for the largest organ in the human body, you might think of the liver, the lungs or the intestines. But the right answer is closer than you think. It’s covering you right now from head to toe: your skin.
The skin: the largest organ in the human body
We may not think of skin as an organ, but scientifically it is a complete organ made of several tissues that carry out vital jobs. And it is by far the body’s largest:
- In adults it covers about 1.5 to 2 square metres.
- It weighs several kilograms, depending on body size.
- It has three main layers: the outer epidermis, then the dermis, then the fatty subcutaneous layer.
What the skin does
- Protection: a shield that keeps germs and harmful substances out.
- Temperature control: through sweating and widening or narrowing blood vessels.
- Sensation: millions of nerve endings sense touch, heat and pain.
- Making vitamin D: when exposed to sunlight.
- Preventing water loss from the body.
Did you know? Your skin constantly renews its outer layer, shedding huge numbers of dead cells every day without you noticing. The surface of the epidermis is renewed roughly every few weeks.
The liver: the largest internal organ
If the question is about the largest internal organ, the answer is the liver. In adults it weighs about 1.5 kilograms and sits in the upper right part of the abdomen, just under the diaphragm.
The liver is also the largest gland in the body, and it performs hundreds of functions, including:
- Filtering the blood of toxins and breaking down medicines.
- Producing bile, which helps digest fats.
- Storing sugar as glycogen, along with some vitamins and iron.
- Making important proteins, including ones that help blood clot.
One of its most remarkable abilities is regenerating itself: it can regrow even after a large part is removed, which is why a living person can donate part of their liver.
Human body records
| Record | Body part |
|---|---|
| Largest organ overall | Skin |
| Largest internal organ and largest gland | Liver |
| Longest bone | Thigh bone (femur) |
| Smallest bone | Stirrup (stapes) in the middle ear, about 3 mm |
| Largest muscle | Gluteus maximus (in the buttocks) |
| Longest nerve | Sciatic nerve, from the lower back to the foot |
| Largest artery | Aorta |
What about the brain and lungs?
- The brain weighs about 1.3 to 1.4 kilograms in adults, a little less than the liver, yet it uses about a fifth of the body’s energy.
- The lungs are large in volume but light, because they’re full of air. The right lung is slightly bigger than the left, which leaves room for the heart.
How to look after your skin and liver
- For your skin: drink water, use sunscreen, and avoid too much midday sun.
- For your liver: keep a healthy weight, cut down on sugar and processed fats, don’t take medicines without advice, and avoid alcohol.
Frequently asked questions
Is skin really an organ?
Yes. In biology, an organ is a group of tissues working together to perform a specific function, and the skin fits that definition perfectly.
What is the largest internal organ in the human body?
The liver, which weighs about 1.5 kilograms in adults.
What is the largest gland in the human body?
Also the liver: it’s both the largest internal organ and the largest gland.
Key takeaway
The largest organ in the human body is the skin, and the largest internal organ is the liver. Both work quietly every day to protect and clean our bodies, so they deserve some care through simple healthy habits.