Organs

What are organs?

Organs are specialized structures in your body that handle specific jobs. Some of the best-known organs are your heart, brain or liver. But many other structures count as organs, too. That includes some you might not think of, like your skin.

Each of your cells is like an individual worker doing a specific job. Tissues are groups of related cells teamed up in the same place. Organs consist of many tissues that work together cooperatively to accomplish a bigger job.

Organs are part of bigger systems that handle interconnected jobs. And some organs can be part of more than one system. Some examples of organ systems and the organs that are part of them include:

• Cardiovascular. Your heart is this system’s main organ. It also includes major vessels like your arteries and veins, and smaller vessels like your capillaries.
• Digestive. This includes your stomach and intestines (small and large). But it also includes structures like your esophagus and openings like your mouth and anus (butthole).
• Endocrine. This includes your pancreas and glands like your thyroid and adrenals, to name a few.
• Immune. This includes your spleen and bone marrow (which makes all kinds of blood cells, including immune-related ones).
• Musculoskeletal. This includes your muscles and all the bones of your skeleton. It also includes certain types of connective tissue like ligaments and tendons.
• Nervous. Your brain and spinal cord are the main organs, plus all the nerves in your body. Your sensory organs like your eyes, ears and nose are also part of this system.
• Reproductive. This includes the ovaries, vagina, uterus, penis, prostate and testicles.
• Respiratory. This includes your openings like your nose and mouth, plus internal organs like your lungs.
• Urinary. This includes internal organs like your kidneys and bladder, plus external genitals like the penis.

Organs can be single structures like your heart. But they can also be a group of the same type of structure. For example, your bones are technically an organ, but so is the bone marrow inside most of your bones.

How many organs are there?

You might get a different answer depending on who you ask. Before 2016, the number of organs was widely recognized as 78. But researchers continue to expand modern medicine’s understanding of how the body works. That’s why, if you ask experts today how many organs you have, the answer can range from 78 to 80.

In particular, two discoveries explained in research papers from 2016 and 2018 now have experts split on the true number. The two organs that are gaining acceptance but still have some controversy behind them are:

• The mesentery. This layer wraps around and contributes to how your immune and lymphatic systems influence your digestive tract. The 2020 printing of Gray’s Anatomy, 42nd edition recognized the mesentery as a true organ. That brought the total number of organs to 79.
• The interstitium. This is a network of fluid-filled spaces between your cells. There’s strong evidence it spans your entire body, including in and around major organs.

There’s still a lot of ongoing research into how these organs work and what they do. And advances in technology and medical science may lead to further discoveries.

What are vital organs?

Vital organs are organs that you need to survive. Your body can’t function without them. Some key examples of vital organs include your:

• Brain
• Heart
• Kidney
• Lungs
• Liver

What organs are on one side of the body?

You have several organs that are centered inside your body, while others are clearly to one side.

Some examples of centered organs in your body include your:

• Brain
• Bladder
• Heart (it’s mainly centered but slightly left, except with rare conditions like dextrocardia)

Some examples of left-side organs include your:

• Pancreas
• Stomach
• Spleen

Examples of right-side organs include your:

• Appendix
• Gallbladder
• Liver

And you have several paired organs, with one on each side of your body. They include your:

• Lungs
• Kidneys
• Eyes
• Ears
• Reproductive organs, including external ones like testicles and internal ones like ovaries

What organs can I survive without?

You can survive without several organs. They include your:

• Appendix
• Gallbladder
• Ovaries and/or uterus
• Spleen
• Testicles
• Large sections of your bowels or the entire colon

You can also survive with just one of several paired organs, like your lungs or kidneys.

While you can’t survive without your heart or at least one kidney, there are artificial versions that can do their jobs. Artificial hearts can be long-term replacements for damaged or diseased hearts. And dialysis can be a long-term substitute (but not a permanent replacement) for your kidneys.

What are accessory organs?

Accessory organs are organs that contribute to a body system, but they might not necessarily be a clear part of it. One example is your gallbladder, which contributes to your digestive system. Breasts are another example. They can contribute to your reproductive system during breastfeeding (chestfeeding).

But being an accessory organ doesn’t mean that organ isn’t important. Your liver is an accessory organ to your digestive system, but you also can’t live without it.

What is the largest organ in the body?

The largest body organ you have is your skin. It makes up about 15% of your total body weight. But for just your internal organs, the largest is your liver.