The hilum is the root of the lung where that contains structures that supply the lungs with blood, lymph fluid, and innervation, such as the pulmonary vein, pulmonary artery, pulmonary nerves, and lymphatic vessels.
These structures are enclosed by pleura. There is a hilium for each of the lungs found in the mediastinum backside of the lungs. The hilium is thinner in the left lung compared to the right lung because it lies between the cardiac notch and the groove for the aorta. The hilium is important because it is the primary way in which the respiratory system links with the cardiovascular and nervous systems.
Pulmonary circulation transports oxygen-depleted blood away from the heart to the lungs and returns oxygenated blood back to the heart. Bronchial circulation by the bronchial arteries supplies blood to the tissues of the bronchi and the pleura, and is considered part of systemic circulation.
The right side of the heart deals with pulmonary circulation. At the end of systemic circulation, the veins take blood back to the heart through the vena cava.
The vena cava fills the right atrium with blood, which then ejects blood into the right ventricle by passing through the tricuspid valve. After blood fills in the right ventricle, it contracts and pumps the blood through the pulmonary valve, and into the pulmonary arteries.
There are two pulmonary arteries one for each lung that bring the deoxygenated blood to the lungs through the hilium. The arteries branch into the capillaries of the alveoli. Capillaries are the thinnest and smallest type of blood vessel, and they supply oxygen to individual tissues everywhere in the human body. Gas exchange occurs by passive diffusion in the alveoli, so that dissolved oxygen enters the capillaries, while carbon dioxide leaves pulmonary circulation.
The oxygenated blood then leaves the lungs through pulmonary veins also contained in the hilium , which return the blood to the left side of the heart, completing the cycle of pulmonary circulation. This blood then enters and fills inside the left atrium, which pumps it through the mitral valve also called bicuspid into the left ventricle.
The blood fills inside the left ventricle and is then pumped through the aortic valve into the aorta, which marks the beginning of systemic circulation. Systemic circulation and pulmonary circulation form the overall cycle of the circulatory system: transporting oxygen throughout the body. Pulmonary circuit : Diagram of pulmonary circulation. Oxygen-rich blood is shown in red; oxygen-depleted blood in blue.
While the cycle of pulmonary and systemic circulation is a well designed and effective system, it is not immune to certain problems. The most serious issue in pulmonary circulation is a pulmonary embolism, which is where a blood clot travels to the lung and causes an infarction of the lung tissue death from lack of oxygen.
These blood clots typically originate in the deep veins of the legs part of systemic circulation as a result of blood pooling from injury or immobilization. As the veins of the leg are on their way to the right side of the heart, the clots are less likely to break up before they reach pulmonary circulation.
When the clot reaches the pulmonary artery, it obstructs the flow of blood into the lung, which causes the alveoli in the effected lung to die as a result. This results in an increase in aveolar dead space and decreased perfusion, leading to shortness of breath and chest pain and can be fatal if not treated in time by fibrinolytics medications that dissolve the clot. Privacy Policy. Skip to main content. Respiratory System.
Search for:. The Lungs and Pleurae. Lungs The lungs are an essential organ which is necessary for the exchange of oxygen and carbon dioxide from the body. Learning Objectives Describe the structure, principal function, and location of the lungs. Key Takeaways Key Points The principal function of the lungs is to transport oxygen from the atmosphere into the bloodstream and to release carbon dioxide from the bloodstream into the atmosphere.
Each alveolus is tightly wrapped in blood vessels and it is here that gas exchange actually occurs. The diaphragm contracts during inhalation, and relaxes during exhaltion. The pleural cavity is the fluid-filled space between the two layers of the pluera, and provides a space for the lung to expand against during inhalation. Too little ventilation indicates a shunt lack of air supply relative to perfusion , while too little alveolar perfusion indicates alveolar dead space from damage or disease.
Key Terms pleura : The double-layered membranous lining of the thoracic cavity that covers the lungs. Its balance is an important indicator of lung function and efficiency. Lobes, Fissures, and Lobules The lungs are located on either side of the heart and are separated by fissures into lobes, three in the right and two lobes in the left.
Learning Objectives Distinguish between the right and left lungs based on their lobes, fissures, and lobules. Each lung half has its own pleura sack. This is why, when one lung is punctured, the other can go on working. The lungs are like bellows. When they expand, they pull air into the body. When they compress, they expel carbon dioxide, a waste gas that bodies produce. Lungs do not have muscles to pump air in and out, though. The diaphragm and rib cage essentially pump the lungs. As a person breathes, air travels down the throat and into the trachea, also known as the windpipe.
The trachea divides into smaller passages called the bronchial tubes. The bronchial tubes go into each lung. The bronchial tubes branch out into smaller subdivisions throughout each side of the lung.
The smallest branches are called bronchioles and each bronchiole has an air sac, also called alveoli. The alveoli have many capillary veins in their walls. Oxygen passes through the alveoli, into the capillaries and into the blood. It is carried to the heart and then pumped throughout the body to the tissues and organs. As oxygen is going into the bloodstream, carbon dioxide passes from the blood into the alveoli and then makes its journey out of the body.
This process is called gas exchange. When a person breathes shallowly, carbon dioxide accumulates inside the body. This accumulation causes yawning, according to York University. The lungs have a special way to protect themselves. Cilia, which look like a coating of very small hairs, line the bronchial tubes.
The lungs are located on either side of the heart and are separated by fissures into lobes, three in the right and two lobes in the left.
The lungs are located in two chambers of the thoracic cavity on either side of the heart. Though similar in appearance, the two lungs are not identical, nor wholly symmetrical. Fissures are double folds of pleura that divide the lung into lobes. There are three lobes in the right lung and two in the left lung.
The lobes are further divided into segments and then into lobules, which are hexagonal divisions of the lungs that are the smallest visible subdivision. The lobes are further divided into segments and then into lobules, hexagonal divisions of the lungs that are the smallest subdivision visible to the naked eye. The lobes of the lungs : The right lung has three lobes and the left lung has two. The right lung is five centimeters shorter than the left lung to accommodate the diaphragm, which rises higher on the right side over the liver; it is also broader.
The volume, the total capacity, and the weight of the right lung is greater than that of the left. The right lung is divided into three lobes. The upper lobe is the largest lobe of the right lung. It extends from the apex of the lung down to the horizontal and oblique fissures. It bears apical, anterior, and posterior bronchopulmonary segments.
The middle lobe is the smallest lobe of the right lung, located between the horizontal and oblique fissures. It bears medial and lateral bronchopulmonary segments. The lower lobe is the bottom lobe of the right lung.
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