All systems of the human body

The smallest functional unit of the human being is the cell. These are grouped together forming tissues, which in turn, make up the organs, and the different organs that perform the same function form a system.

Therefore, a system could be defined as the set of organs and structures that work together to fulfill a specific physiological function in humans. In this eHealth article we explain what the different systems of the human body are , the parts that compose it and their functions within the human body.

The human body is made up of 12 systems and devices that perform specific functions , necessary for the proper functioning of the body.

The systems of the human body are :

• Circulatory system
• Respiratory system
• Digestive system
• Excretory system or urinary tract
• Endocrine system
• Immune system
• Lymphatic system
• Nervous system
• Reproductive system
• Muscular system
• Skeletal system
• Integumentary system

Systems of the human body and their functions

Circulatory system

The circulatory system is made up of the blood vessels and the heart. It works as a motor, so it propels oxygen-rich blood through the arteries to all parts of the body.

The veins are responsible for the return of oxygen-poor blood back to the heart. Its function is to move blood, nutrients and oxygen to nourish each and every one of the body’s cells thanks to the capillaries.

Respiratory system

The respiratory system works together with the circulatory system. The minor circulation links the heart with the lungs. It allows the oxygen from the lungs to pass to the heart and it is in charge of distributing it. In addition, the blood rich in carbon dioxide and poor in oxygen that reaches the heart is directed to the lungs so that they are responsible for expelling the carbon dioxide to the outside.

It is formed mainly by the trachea, the lungs and the diaphragm, and allows respiration through gas exchange.

Digestive system

The digestive system is made up of the mouth, esophagus, stomach, small intestine, ascending, transverse, and descending colon, rectum, and anus. The liver and pancreas work together with the rest of the organs and viscera of the digestive system, as they produce juices that are involved in digestion.

All these organs are in charge of crushing the food so that it can pass through the digestive tract and break down into smaller molecules.

The small intestine is a tube 2 to 4 centimeters in diameter and 6 to 7 meters long. It is responsible for absorbing nutrients thanks to the intestinal microvilli to nourish the cells. However, the large intestine is a cylinder 5 to 10 centimeters in diameter and 1.60 to 1.70 meters in length. Its function is to absorb the liquid that has been generated after the digestive process in order to compact the stool and prepare it to be expelled outside.

Urinary system

The urinary or excretory system is made up of a set of organs, ducts, nerves and muscles that produce, store and transport urine. It consists of two kidneys, two ureters, the bladder, sphincters, and the urethra.

Once the body has absorbed the nutrients it needs from food, waste products remain in the blood and intestines. The kidneys are responsible for removing waste from the blood.

The nephron is the functional unit of the kidney . It is a very complex microstructure in which the blood is filtered to remove waste products through the urine. It is here that the blood circulation and the small tubes through which the newly formed urine circulates come into contact. In each kidney there are millions of nephrons.

The urinary system works together with the lungs, skin, and intestines to keep chemicals and water in the body in balance. Adults usually excrete a quantity of one and a half liters of urine per day.

Endocrine system

For its part, the endocrine system is made up of eight glands that secrete hormones into the blood. These are the pineal, hypothalamus, pituitary, thyroid and parathyroid, thymus, adrenal glands, pancreas, ovaries, and testes. Hormones travel to different tissues regulating body functions such as metabolism, growth or reproductive processes.

Immune system

Responsible for defending the body against bacteria, viruses and other microorganisms is the immune system . It is responsible for combating and destroying invading infectious agents so that they do not cause harm to the human body.

But when it does not work properly, it does not distinguish its own cells from those of others, producing so-called autoimmune diseases. That is, the organism attacks itself.

Lymphatic system

The lymphatic system includes the lymph nodes, ducts, and vessels. It also plays an important role in the body’s defenses. Its function is to create and move lymph, a fluid that contains white blood cells and, together with the spleen, helps the body fight infection.

The bone marrow and the thymus gland are responsible for making the cells found in lymph. When this system does not work properly, fluid builds up in the tissues causing a swelling called lymphedema .

Nervous system

The nervous system is the most complex. It controls both the voluntary actions of the body and the involuntary ones, including breathing, for example.

The central nervous system is made up of the brain and spinal cord. It receives the information and processes it to control bodily functions.

The peripheral nervous system is made up of nerves that connect each of the parts of an individual’s body to the central nervous system. Its function is to transmit information to the brain and lead its orders to the organs in charge of executing them.

The autonomic nervous system has the mission of regulating the functioning of the internal viscera. It is not connected to the cerebral cortex, so, unlike the rest of the nervous system, it does not generate or perceive sensations that can be consciously perceived.

Nor is it responsible for voluntary movements, since it acts involuntarily and autonomously.

Female and male reproductive system

The reproductive system is made up of a set of organs that allow the human being to reproduce. In women (read: female reproductive system ) it is made up of the uterus, the ovaries that make eggs, the fallopian tubes and the vagina. In men (visit our article: male reproductive system ) they are made up of the testicles that make sperm, the vas deferens and the penis.

For the conception of a new life, a sperm unites with an egg forming the zygote that will develop in the woman’s uterus.

Muscular system

The muscular system is made up of 650 muscles that allow movement. There are different types of muscles. Skeletal muscle attaches to bone helping voluntary movement. The smooth found within the organs facilitates the movement of substances. The cardiac is located in the heart and contributes to the pumping of blood.

Skeletal system

The skeletal system is made up of 206 bones that are connected by tendons, cartilage and ligament. The skeleton allows movement, but it is also involved in the creation of blood cells and the storage of calcium. Together with the nervous, articular and muscular systems, it forms the locomotor system.

The skin is the organ of the integumentary system , and the largest in the human body. Its function is to protect the external world and is the first defense barrier against viruses, bacteria and other pathogenic microorganisms. It also helps regulate the body’s temperature and eliminate waste through perspiration. This system also includes, in addition, hair and nails.

Interrelation between the different systems and devices

All the systems of the human body are related to each other . The organism is a whole in which each organ works both separately and in conjunction with other organs or devices.

The correct functioning of all systems allows the individual to live in health . Similarly, when one of them is damaged and does not work well, it negatively affects the rest.

The endocrine system , for example, has full control over all other systems . These respond to signals sent by the brain through the spinal cord.

The respiratory system is also in close collaboration with the other systems . It provides oxygen to all parts of the body and removes carbon dioxide from the digestive, muscular, bone, circulatory, urinary and nervous systems.

The circulatory system works closely with the respiratory system . It performs a transport function of moving oxygen and carbon dioxide throughout the body. But also with the digestive system, since in addition to the transport of gases, the nutrients also travel through the bloodstream.

For its part, the endocrine system is closely linked to the nervous system . In fact, the combination of both is called the neuroendocrine system. But also the immune system is related to these two through the multiple chemical messengers that reside in the body.

The neuroendocrine is a group of nerves and endocrine glands that secrete chemicals. Both work together in order to produce temporary or chronic changes in the body. Thanks to nerve signals and hormones, this system produces changes, for example in cellular activities.

These modify the diameter of the blood vessels as well as the heart rate and the amount of fluid that the body holds. Therefore, the neuroendocrine system is also related to the circulatory and urinary systems .