An organ is defined as a group of tissues working cooperatively to perform one specific job. Your lungs, liver and brain all constitute organs.
Your digestive tract and glands such as the pancreas also are key organs of health, while your skeletal system–including its largest bone, the femur bone from knee to hip — play key roles.
Many people often wonder what’s the biggest organ in the human body?, and the answer is the skin, which covers and protects the entire body.
| Organ | Type | Average Size/Weight in Adults | Key Functions |
|---|---|---|---|
| Skin | External organ | ~16% of body weight (~3–4 kg in adults) | Protects body, regulates temperature, prevents water loss, sensory reception |
| Liver | Internal organ | ~1.4–1.6 kg | Detoxifies blood, produces bile, stores nutrients, regulates metabolism |
| Brain | Internal organ | ~1.3–1.4 kg | Controls body functions, cognition, memory, emotions |
| Lungs | Internal organ (pair) | ~1.1 kg combined | Gas exchange (oxygen in, carbon dioxide out) |
| Heart | Internal organ | ~300 g | Pumps blood, supplies oxygen and nutrients throughout body |
The Lungs
The lungs are two soft, spongy organs enclosed by a thin membrane called the pleura in your chest that weigh between 4.5 to 6 ounces (125 to 170 grams) as adults, making them one of the largest organs in your body. Each lung serves a vital purpose: inhaling oxygen, filtering carbon dioxide out and pumping blood around.
The lung is composed of millions of tiny air sacs called alveoli that absorb oxygen into your bloodstream via capillaries. Pulmonary muscles also assist with breathing. Air enters through nostrils and mouth openings before passing into alveoli that have microscopic hairs called cilia that warm and humidify it before blowing it back out as you exhale.
As you breathe in, your lungs expand with each inhale. This expansion is controlled by the pressures blown onto them from breathing in air or from within airways and resistance of lung tissue elasticity or resistance; this pressure-volume relationship is graphically represented on a spirogram as Cdyn (lung compliance) curves.
At some point during forced expiration, pressure exceeds elastic limit of lung and the lung becomes flow-limited causing it to contract further than expected and eventually become ‘flow limited.’
Gray’s Anatomy of the Human Body lists your kidneys, pancreas and liver as among your heaviest organs, with your kidneys responsible for filtering out toxins from the blood and weighing between 4.5 to 6 ounces for adult males and 4 to 5.4 for females based on Gray’s Anatomy of the Human Body; pancreas secretes enzymes which assist your intestines absorb nutrients from digested food while its weight may change with menstruation, pregnancy and other factors; finally your liver helps store and use fats efficiently so could weigh anywhere between 6-8 ounces depending on individual. According to Gray’s Anatomy of the human Body
The Heart
Are You Studying Human Anatomy? If you are, then organs are specialized structures in your body designed to perform specific jobs. Organs include single structures like your heart or brain as well as groups of tissues working cooperatively towards an overall task like your circulatory system or immune system. Other structures might not come to mind immediately but nonetheless count: Your skin serves as an organ that protects from bacteria and chemicals!
Your heart is an integral component of the circulatory system and serves as the largest organ in your body, pumping blood to all parts of your body so every cell receives oxygen and nutrients while carrying away wastes.
As one of the most crucial organs, its primary duty is pumping blood around and keeping its circulation moving – this constant bloodflow ensures cell health as well as providing oxygen to brain, kidneys, livers and lungs.
The lungs are the second-biggest organ in your body, located within the thoracic cavity just beneath your heart and just left of your breastbone (sternum). They cover an approximate surface area equivalent to that of a tennis court, consisting of air sacs that store six liters of oxygen at any one time – an essential source for creating energy by cells throughout your body, as well as expelling carbon dioxide out of bloodstream.
Inside your lungs are two lobes known as the right and left pulmonary arteries, approximately the diameter of your thumb each. The right pulmonary artery receives oxygenated blood from its source before carrying it to its destination – right ventricle. Meanwhile, left pulmonary arteries transport deoxygenated blood from right ventricle back into left lung for re-oxygenation by left ventricle pumps.
Your heart’s outer layer is made up of layers of tissue and fat. The middle layer, myocardium, is responsible for pumping action while its thick innermost layer endocardium lines the chambers and valves while protecting from fatal blood clots.
The Kidneys
The kidneys serve as an intricate filter system for your blood, eliminating waste products, regulating sodium levels and producing urine. Most adults possess two bean-shaped kidneys about the size of a fist protected by fat and muscles connected via tubes to the bladder.
Each day, your kidneys process about 200 quarts of blood removing excess water waste products as well as substances before producing urine; overworking or damaging this organ may lead to chronic kidney disease symptoms.
The lungs are soft, spongy and elastic organs located within the chest cavity that provide protection from bacteria, viruses, chemicals and germs. Furthermore, they serve to regulate blood pressure; hence their reputation as one of the main blood-pumping organs in the heart.
Each lung is lined with a thin membrane known as the pleura, which helps protect them and stop air from leaking inside of them. Lungs contain over 2 million blood vessels protected by mucous membranes; together these parts make up the respiratory system which provides us with breath.
Your kidneys are located on either side of your spine in the lower back and they measure approximately the size of a large fist. Each kidney is well protected by fat tissue and your lower ribs, and contains millions of filtering units known as nephrons that work to filter your blood – each filter has both a glomerulus for filtering blood and tubules that reabsorb necessary substances and flush toxins out.
Your kidneys take their name from the Greek word for nephros, which translates to “narrow”. They are bean-shaped organs about the size and weight of a fist that weigh approximately 5 ounces each. Protected by a tough layer of tissue called the renal capsule that is enveloped by fat layers, blood flows to them through their respective renal arteries before exiting through their respective ureters – they also produce hormones like erythropoietin to promote red blood cell production as well as renin to regulate blood pressure control.
The Brain
The brain serves as the hub of your nervous system and is one of the primary components of your body, along with spinal cord. Additionally, it is the heaviest solid organ at around three pounds.
Contrary to popular belief, the brain is composed of nerve cells rather than blood vessels. These nerve cells are organized into regions called lobes; each region performs its own specific task – for instance the hippocampus helps manage memory and navigation while amygdalae are almond-shaped structures located under both halves of the brain which regulate emotions such as fear and stress responses.
Scientists used to assume that an animal’s brain size correlated directly with its overall body size, using a formula known as the “encephalisation quotient”, or EQ. A larger animal should have a higher EQ than smaller species from its species; but in recent years scientists studying animal brains discovered otherwise; instead it’s shown that brains require much more energy-intensive organs in the body for survival, forcing their size and mass distribution through special functions that maintain life itself.
In addition to regulating hormones and blood pressure, your brain serves as the organ that gives you your sense of identity and coordinates all body movement.
The heart is an organ that requires considerable energy to function effectively, pumping blood that transports oxygen to other organs while draining away waste products from them. Its weight comes from its heavy muscle fibers which drive each beat.
New research suggests that the interstitium, an array of fluid-filled spaces supported by connective tissue mesh, could be your largest organ. But until accepted by medical science, skin remains your biggest organ: adults wear on average 8 pounds.