Blood and defense system
Blood is also called a “liquid organ” and fulfils many different and important tasks in the body. Blood supplies all body tissues with oxygen from the lungs and transports carbon dioxide back to the lungs so that it can be breathed out. Blood also supplies the tissues with nutrients from the digestive tract and frees them from metabolic and waste products.
These are transported to the internal organs, kidney and intestine, to be excreted. Last but not least, blood serves as an important medium for the transport of messenger substances (hormones), components of the body’s own defense and blood clotting between the individual organ systems. In an adult person, about 70 to 80 milliliters of blood per kilogram of body weight (about 5 to 6 liters of blood in total) flow through the blood vessel system.
The body’s own defense system or immune system prevents tissue damage caused by pathogens. The immune system is a network of different organs, cell types and molecules, which ensures that the body’s own cells that have become defective are destroyed and microorganisms or foreign substances that have entered the body are removed. The immune system includes, for example, mechanical barriers that are intended to prevent the penetration of pathogens, such as the skin and mucous membranes, the respiratory tract or the stomach with gastric acid.
The immune system also includes certain cells that circulate in the blood vessels and lymphatic system. These defense cells can fight pathogens if they have already entered the body (e.g. granulocytes, T-lymphocytes, natural killer cells). In addition, there are certain proteins in the body that serve as messenger substances or to defend against pathogens.These include antibodies that recognize and bind to certain foreign substances in order to mark them so that the foreign substance can be recognized and eliminated by the body.
Endocrine System
The endocrine system or hormone system is an organ system that controls many bodily functions, from growth to reproduction to digestion. Hormones are messenger substances that are transported via the bloodstream to their target organs. Endocrine organs include two glands (pituitary gland and pineal gland), which are located in the skull and are therefore not listed here.
The endocrine glands belonging to the internal organs are the thyroid gland, the parathyroid glands, the adrenal glands, the sex glands and the islets of Langerhans of the pancreas. The thyroid gland produces the two thyroid hormones thyroxine and triiodothyronine, which are responsible for the energy metabolism of the cells and for protein production. If the energy metabolism is increased, the thyroid gland is overactive, if it is slowed down, it is called underactive.
The four parathyroid glands are located at the back of the thyroid gland and produce the hormone parathyroid hormone. This regulates the body’s calcium balance, which is important for the formation of bones and teeth, for the function of nerve and muscle cells, and for blood clotting. The islets of Langerhans of the pancreas produce insulin and glucagon.
These hormones regulate the blood sugar level. The adrenal glands are organs that regulate the body’s water and salt balance and help the body to cope with stress or emergency situations. This is where the hormones adrenaline and noradrenaline are produced, which are released into the bloodstream in dangerous or stressful situations.
This increases the heart rate, causes the blood vessels of the skin and internal organs to constrict and provides the body with more energy. Steroid hormones are also produced in the adrenal gland: Aldosterone to regulate the salt and water balance, cortisol to increase the blood sugar level and reduce the body’s resistance to infections. In women, the sex glands are arranged in pairs as ovaries, in men they form the testicles in the scrotum.
In both sexes the sex hormones estrogen, progesterone, testosterone and androsterone are produced in these organs. The effect of the hormones is different in women than in men because they are produced in different proportions. Female sexual characteristics such as the development of breasts and the widening of the hips are influenced by the hormones estrogen and progesterone.
In contrast, the male sex hormones testosterone and androsterone, for example, cause beard growth and a deeper voice in men. The respiratory tract includes all internal organs that are responsible for breathing. These include the nose, throat, larynx, windpipe, main branch of the trachea, bronchi, bronchioles and alveoli.
In humans, the lung consists of two lobes, which are divided into two (left lung) or three (right lung) lobes. The lobes of the lungs are located in the chest cavity and the lung volume of an adult person is about 5 to 6 liters. The gas exchange, i.e. the exchange of oxygen and carbon dioxide, takes place in the alveoli.
The remaining organs of the respiratory tract are the so-called air conducting system (bronchial system). When inhaled, air flows through the mouth or nose into the body and enters the trachea via the pharynx. Here the air is cleaned by small cilia.
At the end are the approximately 300 million pulmonary alveoli. These have only a very thin dividing wall (blood-air barrier) to the blood vessels. Here the blood is loaded with oxygen (oxygenated) and in the opposite direction carbon dioxide can be released from the blood into the air, which is then exhaled.
The lung medicine or the science of lung diseases is called pneumology. A pneumonologist (lung specialist) deals with the prophylaxis, detection and conservative treatment of diseases of the lung, bronchial tubes, mediastinum and pleura (lung skin). These include bronchial asthma, bronchitis, sleep apnoea syndrome, pneumonia or pulmonary fibrosis.
