Respiratory+System



=Respiratory system= Respiration is the process by which living organisms take in oxygen and release carbon dioxide. The human respiratory system, working in conjunction with the circulatory system, supplies oxygen to the body's cells, removing carbon dioxide in the process. The exchange of these gases occurs across cell membranes both in the lungs (external respiration) and in the body tissues (internal respiration). Breathing, or pulmonary ventilation, describes the process of inhaling and exhaling air. The human respiratory system consists of the respiratory tract and the lungs.

Respiratory tract
The respiratory tract cleans, warms, and moistens air during its trip to the lungs. The tract can be divided into an upper and a lower part. The upper part consists of the nose, nasal cavity, pharynx (throat), and larynx (voice box). The lower part consists of the trachea (windpipe), bronchi, and bronchial tree . The nose has openings to the outside that allow air to enter. Hairs inside the nose trap dirt and keep it out of the respiratory tract. The external nose leads to a large cavity within the skull, the nasal cavity. This cavity is lined with mucous membrane and fine hairs called cilia. Mucus moistens the incoming air and traps dust. The cilia move pieces of the mucus with its trapped particles to the throat, where it is spit out or swallowed. Stomach acids destroy bacteria in swallowed mucus. Blood vessels in the nose and nasal cavity release heat and warm the entering air.

Air leaves the nasal cavity and enters the pharynx. From there it passes into the larynx, which is supported by a framework of cartilage (tough, white connective tissue). The larynx is covered by the epiglottis, a flap of elastic cartilage that moves up and down like a trap door. The epiglottis stays open during breathing, but closes during swallowing. This valve mechanism keeps solid particles (food) and liquids out of the trachea. If something other than air enters the trachea, it is expelled through automatic coughing.

Words to Know

 * Alveoli:** Tiny air-filled sacs in the lungs where the exchange of oxygen and carbon dioxide occurs between the lungs and the bloodstream.
 * Bronchi:** Two main branches of the trachea leading into the lungs.
 * Bronchial tree:** Branching, air-conducting subdivisions of the bronchi in the lungs.
 * Diaphragm:** Dome-shaped sheet of muscle located below the lungs separating the thoracic and abdominal cavities that contracts and expands to force air in and out of the lungs.
 * Epiglottis:** Flap of elastic cartilage covering the larynx that allows air to pass through the trachea while keeping solid particles and liquids out.
 * Pleura:** Membranous sac that envelops each lung and lines the thoracic cavity.



**The lungs**

 * The lungs are two cone-shaped organs located in the chest or thoracic cavity. The heart separates them. The right lung is somewhat larger than the left. A sac, called the pleura, surrounds and protects the lungs. One layer of the pleura attaches to the wall of the thoracic cavity and the other layer encloses the lungs. A fluid between the two membrane layers reduces friction and allows smooth movement of the lungs during breathing.**
 * The lungs are divided into lobes, each one of which receives its own bronchial branch. Inside the lungs, the bronchi subdivide repeatedly into smaller airways. Eventually they form tiny branches called terminal**
 * bronchioles. Terminal bronchioles have a diameter of about 0.02 inch (0.5 millimeter). This branching network within the lungs is called the bronchial tree.**
 * The terminal bronchioles enter cup-shaped air sacs called alveoli (pronounced al-VEE-o-leye). The average person has a total of about 700 million gas-filled alveoli in the lungs. These provide an enormous surface area for gas exchange. A network of capillaries (tiny blood vessels) surrounds each alveoli. As blood passes through these vessels and air fills the alveoli, the exchange of gases takes place: oxygen passes from the alveoli into the capillaries while carbon dioxide passes from the capillaries into the alveoli.**
 * This process — external respiration — causes the blood to leave the lungs laden with oxygen and cleared of carbon dioxide. When this blood reaches the cells of the body, internal respiration takes place. The oxygen diffuses or passes into the tissue fluid, and then into the cells. At the same time, carbon dioxide in the cells diffuses into the tissue fluid and then into the capillaries. The carbon dioxide-filled blood then returns to the lungs for another cycle.**

**Breathing**

 * Breathing exchanges gases between the outside air and the alveoli of the lungs. Lung expansion is brought about by two important muscles, the diaphragm (pronounced DIE-a-fram) and the intercostal muscles. The diaphragm is a dome-shaped sheet of muscle located below the lungs that separates the thoracic and abdominal cavities. The intercostal muscles are located between the ribs.**
 * Nerves from the brain send impulses to the diaphragm and intercostal muscles, stimulating them to contract or relax. When the diaphragm contracts, it moves down. The dome is flattened, and the size of the chest cavity is increased. When the intercostal muscles contract, the ribs move up and outward, which also increases the size of the chest cavity. By contracting, the diaphragm and intercostal muscles reduce the pressure inside the lungs relative to the pressure of the outside air. As a consequence, air rushes into the lungs during inhalation. During exhalation, the reverse occurs. The diaphragm relaxes and its dome curves up into the chest cavity, while the intercostal muscles relax and bring the ribs down and inward. The diminished size of the chest cavity increases the pressure in the lungs, thereby forcing air out.**



Respiratory System, in anatomy and physiology, organs that deliver oxygen to the [|circulatory system]for transport to all body cells. Oxygen is essential for cells, which use this vital substance to liberate the energy needed for cellular activities. In addition to supplying oxygen, the respiratory system aids in removing of carbon dioxide, preventing the lethal buildup of this waste product in body tissues. Day-in and day-out, without the prompt of conscious thought, the respiratory system carries out its life-sustaining activities. If the respiratory system’s tasks are interrupted for more than a few minutes, serious, irreversible damage to tissues occurs, followed by the failure of all body systems, and ultimately, death.

While the intake of oxygen and removal of carbon dioxide are the primary functions of the respiratory system, it plays other important roles in the body. The respiratory system helps regulate the balance of acid and base in tissues, a process crucial for the normal functioning of cells. It protects the body against disease-causing organisms and toxic substances inhaled with air. The respiratory system also houses the cells that detect smell, and assists in the production of sounds for speech.

The respiratory and circulatory systems work together to deliver oxygen to cells and remove carbon dioxide in a two-phase process called respiration. The first phase of respiration begins with breathing in, or inhalation. Inhalation brings air from outside the body into the lungs. Oxygen in the air moves from the lungs through blood vessels to the heart, which pumps the oxygen-rich blood to all parts of the body. Oxygen then moves from the bloodstream into cells, which completes the first phase of respiration. In the cells, oxygen is used in a separate energy-producing process called [|cellular respiration], which produces carbon dioxide as a byproduct. The second phase of respiration begins with the movement of carbon dioxide from the cells to the bloodstream. The bloodstream carries carbon dioxide to the heart, which pumps the carbon dioxide-laden blood to the lungs. In the lungs, breathing out, or exhalation, removes carbon dioxide from the body, thus completing the respiration cycle. =__A smokers lung (left) and a healthy lung ( right)__=

=**Random but relevent interesting INFO / QUESTIONS**__:__=

**Why Do I Yawn?**

When you are sleepy or drowsy the lungs do not take enough oxygen from the air. This causes a shortage of oxygen in our bodies. The brain senses this shortage of oxygen and sends a message that causes you to take a deep long breath---a YAWN.

[|Contents] **Why Do I Sneeze?**

Sneezing is like a cough in the upper breathing passages. It is the body's way of removing an irritant from the sensitive mucous membranes of the nose. Many things can irritate the mucous membranes. Dust, pollen, pepper or even a cold blast of air are just some of the many things that may cause you to sneeze. **What Causes Hiccups?**

Hiccups are the sudden movements of the [|diaphragm]. It is involuntary --- you have no control over hiccups, as you well know. There are many causes of hiccups. The diaphragm may get irritated, you may have eaten to fast, or maybe some substance in the blood could even have brought on the hiccups. amazing facts:
 * The right lung is slightly larger than the left.
 * Hairs in the nose help to clean the air we breathe as well as warming it.
 * The highest recorded "sneeze speed" is 165 km per hour.
 * The surface area of the lungs is roughly the same size as a tennis court.
 * The capillaries in the lungs would extend 1,600 kilometres if placed end to end.
 * We lose half a litre of water a day through breathing. This is the water vapour we see when we breathe onto glass.
 * A person at rest usually breathes between 12 and 15 times a minute.
 * The breathing rate is faster in children and women than in me.