The lungs are one of the primary organs in the respiratory system. With the lungs, we can breathe, speak, sing, hold our breath, and obtain energy for our bodies. The lungs are located in the chest, along with the heart, and are protected by the ribs. The lungs are responsible for the uptake of oxygen and supplying it to the rest of the body. The oxygen, which travels down the trachea and through the bronchi, is delivered into the bloodstream at the alveoli, where carbon dioxide is also taken out of the bloodstream and breathed back out into the atmosphere. Many different kinds of diseases can be contracted in the lungs. Some of the most common and serious ones include asthma, pneumonia, and lung cancer. Smoking, a practice that has been common in society for many years, harms the lungs directly and increases the risk of developing some form of a disease, including one of the worst cancers possible. Lungs are a vital part of the body's health and must be cared for, as they weaken with age.
There are two sections to the respiratory system: the upper respiratory tract and the lower respiratory tract. The upper respiratory tract consists of the nasal cavity, paranasal sinuses, and pharynx. The lower respiratory tract consists of the larynx, trachea, bronchi, and lungs. The lungs start at the nasal cavity and the throat. Then comes the larynx, which is the start of the windpipe (trachea). The windpipe branches into the lungs, separating into bronchi and alveoli. 
The lungs are pinkish spongy sacs filled with air that are split into two segments, the right lung and the left lung. They are located in the thoracic cavity (chest), beginning at the collar bone and stretching down to the diaphragm. Each lung includes several different sections. The section of the lung that is the uppermost tip is called the apex, which extends just above the first rib and up to the base of the neck. Located opposite of the apex is what's known as the base, which rests on top of the diaphragm. The edges of the lungs are known as the borders. Both lungs also each have three different surfaces. The first surface is the costal surface, which is smooth and faces the front of the chest. The second surface, the mediastinal surface, faces the midline. On the base of the lungs is the third surface, the diaphragmatic surface.
The trachea is the long tube extending down from the nostrils. Near the middle of the lungs, the trachea separates into two smaller tubes known as bronchi, which further branch off in both sides of the lungs. These extensions of the bronchi are called bronchioles, and they split into alveoli, which are tiny sacs connected to the bloodstream where carbon dioxide and oxygen is exchanged. The bronchi are vital portions of the lungs, serving as the passageways that allow for the entry of oxygen and the removal of carbon dioxide. Positioned roughly in the gap between each lung is the heart. As a result of this, the right lung is somewhat larger than the left.
The primary purpose of the lungs is to take air into the body. Their flexible structure allows them to inflate as oxygen is inhaled and delivered to the bloodstream, and then shrink back to their original size as excess carbon dioxide is exhaled. Oxygen is the transparent gas in the atmosphere of the earth that enters the lungs through the trachea. From the trachea it travels down the bronchial tubes to the alveoli. The alveoli are the microscopic portions of the lungs where the oxygen infiltrates the blood by crossing a membrane, and is replaced with carbon dioxide that travels back out of the lungs. Due to the fact that lungs themselves possess no form of muscles, this process of breathing requires the diaphragm, the stomach muscles, and other surrounding muscles in order to be effective. The lungs lengthen and expand when the diaphragm, which is attached to the base, pulls them down by compressing and shortening itself.
Aside from breathing, the lungs play a part in other vital roles in the body. One of these roles involves maintaining blood pressure levels. This process occurs when the lungs convert an enzyme called Angiotensin l into Angiotensin ll, which is necessary for regulation. Other important functions of the lungs include filtering the bloodstream of clots, stabilizing pH levels by removing excess gas, and providing the air pipe necessary for speaking.
When you inhale through your nose, the air is warmed and conditioned. It goes down the trachea, which forks into either lung. The beginning of the forking tube is called a bronchi, which splits into a second bronchi, which splits into an even smaller tertiary bronchi, which splits into bronchioles, which go on to eventually split into little cavity sacs called alveoli. The alveoli play the final part in the respiration sequence. First, the alveoli exchange the oxygen inside of it for the carbon dioxide in the blood. The carbon dioxide is exhaled out of the lungs, while the now-oxygenated blood goes out to the heart and the rest of the body and deposits the oxygen. As the oxygen is being deposited, the blood cells pick up the carbon dioxide in exchange, and then go to the lungs where it can be exhaled. And the cycle continues. 
The diaphragm is a large muscle that is key in pushing air out of the lungs and bringing it in. To inhale, it contracts and pushes the organs below it downward. This makes the lungs expand which brings in oxygen. To exhale, the diaphragm relaxes and rises up, pushing the lungs, making them contract and exhale. 
Speaking is controlled through the vocal cords. There are two kinds of vocal cord, true vocal cords, and false vocal cords. Both are ligaments, covered in mucosa, and are in the larynx. They each have different functions. The false vocal cords close the larynx, preventing swallowed food from entering the lungs, as well as holding a breath. The true vocal cords produce sound by moving its folds together as air passes through. This causes them to vibrate, making sounds. 
There is a wide variety of different kinds of diseases in lungs, from those that impact the aveoli to those that impact the airways and more. Lung diseases are among the most widespread ailments in humans. Some common types include asthma, pneumonia, and lung cancer. 
Asthma is a condition in the bronchial tubes as a result of swollen or constricted airways. This is usually caused by allergies or poor environmental conditions and starts at a young age. The symptoms of asthma include wheezing, coughing, and difficulty breathing. While asthma can prove to be a serious disease, treatments and medicines exist that can reduce the intensity of the symptoms.
Pneumonia, a temporary condition, occurs when the lungs contract an infection in the alveoli as a result of a fungus or bacteria. This disturbance in the air sacs can cause difficulty breathing, chronic coughing, a fever, and sometimes chills. Pneumonia can be fatal, however it can also be prevented through medical treatments and vaccines.
Lung cancer exists in many different forms and most commonly occurs in the alveoli, however it can develop in any part of the lungs. Tumors grow in the lungs as a result of the uncontrollable growth of atypical cells, interrupting the organ's normal function. This can cause symptoms such as insistent coughing, an aching in the chest, and a raspy voice. Because lung cancer can take up to a year to produce any visible symptoms, it is a very dangerous disease.
The practice of smoking, while it is not a disease itself, can induce any type of lung disease and cause major damage. Smoking is the inhalation of carbon monoxide into the respiratory system. The chemicals, which enter the airways and bloodstream, can cause the lungs to become infected and inflamed, harming its immunity and ability to clean itself. As a result the consumption of oxygen is decreased. Smoking also possesses the potential to create cancerous cells out of healthy ones, thus increasing the risk of contracting a lung disease.
Anatomy of the human lungs
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