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The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier. The lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, which receive air breathed in via the conducting zone. These divide until air reaches microscopic alveoli, where gas exchange takes ...
The next addition to the historical understanding of pulmonary circulation arrived with the Ancient Greeks. Physician Alcmaeon (520 – 450 BCE) proposed that the brain, not the heart, was the connection point for all of the vessels in the body. He believed that the function of these vessels was to bring the "spirit" ("pneuma") and air to the ...
The lungs expand and contract during the breathing cycle, drawing air in and out of the lungs. The volume of air moved in or out of the lungs under normal resting circumstances (the resting tidal volume of about 500 ml), and volumes moved during maximally forced inhalation and maximally forced exhalation are measured in humans by spirometry. [12]
The diaphragm is the main muscle of respiration and functions in breathing. During inhalation, the diaphragm contracts and moves in the inferior direction, enlarging the volume of the thoracic cavity and reducing intra-thoracic pressure (the external intercostal muscles also participate in this enlargement), forcing the lungs to expand.
Breathing is the repetitive process of bringing air into the lungs and taking waste products out. The oxygen brought in from the air is a constant, on-going need of an organism to maintain life. This need is still there during sleep so that the functioning of this process has to be automatic and be part of the autonomic nervous system. The in ...
Lung transplantation – the replacement of either a single lung or both (bilateral) – may be considered in end-stage disease. A bilateral transplant is the preferred choice as complications can arise in a remaining single native lung; complications can include hyperinflation, pneumonia, and the development of lung cancer. [60]
Information about the structure and function of the human brain comes from a variety of experimental methods, including animals and humans. Information about brain trauma and stroke has provided information about the function of parts of the brain and the effects of brain damage. Neuroimaging is used to visualise the brain and record brain ...
The brain and central nervous system reside in an area protected from the rest of the body by the blood brain barrier. The lungs sit in the pleural cavity. The intestines, liver, and spleen sit in the abdominal cavity. Height, weight, shape and other body proportions vary individually and with age and sex.