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From Wikipedia

Respiratory tract

In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration. The respiratory tract is divided into 3 segments: Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx Respiratory airways: voice box or larynx, trachea, bronchi, and bronchioles Lungs: respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli The respiratory tract is a common site for infections. Upper respiratory tract infections are probably the most common infections in the world. Most of the respiratory tract exists merely as a piping system for air to travel in the lungs, and alveoli are the only part of the lung that exchanges oxygen and carbon dioxide with the blood. Moving down the respiratory tract starting at the trachea, the tubes get smaller and divide more and more. There are estimated to be about 20 to 23 divisions, ending up at an alveolus. Even though the cross-sectional area of each bronchus or bronchiole is smaller, because there are so many, the total surface area is larger. This means there is less resistance at the terminal bronchioles. (Most resistance is around the 3-4 division from the trachea due to turbulence.) General histology The respiratory tract is covered in an epithelium, the type of which varies down the tract. There are glands and mucus produced by goblet cells in parts, as well as smooth muscle, elastin or cartilage. Most of the epithelium (from the nose to the bronchi) is covered in pseudostratified columnar ciliated epithelial cells, commonly called respiratory epithelium. The cilia beat in one direction, moving mucus towards the throat where it is swallowed. Moving down the bronchioles, the cells get more cuboidal in shape but are still ciliated. Cartilage is present until the small bronchi. In the trachea they are C-shaped rings, whereas in the bronchi they are interspersed plates. Glands are abundant in the upper respiratory tract, but there are fewer lower down and they are absent from the bronchioles onwards. The same goes for goblet cells, although there are scattered ones in the first bronchioles. Smooth muscle starts in the trachea, where it joins the C-shaped rings of cartilage. It continues down the bronchi and bronchioles which it completely encircles. Instead of hard cartilage, the bronchi and bronchioles have a lot of elastic tissue. Summary: Upper respiratory tract - nose, pharynx & asscociates structures Lower respiratory tract - larynx, trachea, bronchi & lungs

From Encyclopedia

The Respiratory System The Respiratory System

Breathing, controlled by the respiratory system, is a continuous process of which a person is normally unaware. If breathing stops, however, a person becomes acutely aware of the fact. An individual can go days without food and water and hours without sleep, but only five or six minutes without air. Anything beyond that would be fatal. The trillions of cells in the body need a constant and generous amount of oxygen to carry out their vital functions. As they use that oxygen, they give off carbon dioxide as a waste product. It is the role of the respiration system, working in conjunction with the cardiovascular system, to supply the oxygen and dispose of the carbon dioxide. Breathing describes the process of inhaling and exhaling air. The exchange of gases (oxygen and carbon dioxide) between living cells and the environment is a process known as respiration. The respiratory system, which controls breathing and respiration, consists of the respiratory tract and the lungs. The respiratory tract cleans, warms, and moistens air on its way 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), larynx, and upper part of the trachea (windpipe). The lower part consists of the lower part of the trachea, bronchi, and lungs (which contain bronchioles and alveoli). The nose is the only external part of the respiratory system. It is made of bone and cartilage (tough connective tissue) and is covered with skin. The two openings to the outside, called nostrils, allow air to enter or leave the body during breathing. The nostrils are lined with coarse hairs that prevent large particles such as dust, insects, and sand from entering. The nostrils open into a large cavity, the nasal cavity. This cavity is divided into right and left cavities by a thin plate of bone and cartilage called the nasal septum. The hard portion of the palate forms the floor of the entire nasal cavity, separating it from the mouth or oral cavity below. Three flat, spongy folds or plates project toward the nasal septum from the sides of the nasal cavity. These plates, called nasal conchae, help to slow down the passage of air, causing it to swirl in the nasal cavity. thick, gooey liquid. As the nasal conchae cause air to swirl in the nasal cavity, the mucus moistens the air and traps any bacteria or particles of air pollution. The cilia wave back and forth in rhythmic movement, and pieces of mucus with their trapped particles are swept along to the throat. The mucus is then either spat out or (more often) swallowed. Any bacteria present in the swallowed mucus is destroyed by the hydrochloric acid in the gastric juice of the stomach. Air is not only moistened in the nasal cavity but warmed, as well. A rich network of thin-walled capillaries permeates the mucus membrane (especially the uppermost concha), and the incoming air is warmed as it passes over the vessels. When air finally reaches the lungs, it is similar to the warm, damp air found in the tropics. The bones that surround the nasal cavity contain hollow spaces known as paranasal sinuses. The sinuses are also lined with mucous membrane containing cilia. The mucus produced in the sinuses drains into the nasal cavity. The main functions of the sinuses are to lighten the skull and to provide resonance (sound quality) for the voice. The pharynx or throat is a short, muscular tube extending about 5 inches (12.7 centimeters) from the nasal cavity and mouth to the esophagus and trachea. It serves two separate systems: the digestive system (by allowing the passage of solid food and liquids) and the respiratory system (by allowing the passage of air). The larynx, commonly called the voice box, forms the upper part of the trachea. The larynx is made of nine pieces of cartilage connected by ligaments. The largest of these cartilages is the shield-shaped thyroid cartilage, which may protrude at the front of the neck, forming the so-called Adam's apple. The upper cartilage is the epiglottis, a flaplike piece of tissue. During swallowing, the larynx rises up and the epiglottis folds down to cover the glottis, or the larynx's opening. This prevents food or liquids from passing into the lower respiratory tract. Mucous membrane lines the larynx. A pair of elastic folds in that lining form the vocal cords. During silent breathing, the vocal cords lie against the walls of the larynx. During speech, the cords are stretched across the opening of the larynx and air that passes through causes them to vibrate, generating sound waves. Various muscles produce tension on the cords, making them tighter (shorter) or looser (longer). The tighter the tension, the higher the pitch of the sound produced. Since men's larynges tend to be larger than women's, their vocal cords tend to be thicker and longer. The male voice thus tends to be lower in pitch. The trachea is a tough, flexible tube about 1 inch (2.5 centimeters) in diameter and 4.5 inches (11.4 centimeters) in length. Located in front of the esophagus, it is the principal tube that carries air to and from the lungs. The walls of the trachea are supported by 16 to 20 C-shaped cartilage rings. Elastic fibers in the tracheal walls allow the trachea to expand and contract during breathing, while the cartilage rings prevent it from collapsing. Mucous membrane containing cilia lines the trachea. The mucus produced by the membrane traps dust particles and other debris. The cilia move continuously in a direction opposite that of the incoming air, helping propel the mucus away from the lungs to the throat where it can be swallowed or spat out. The trachea divides behind the sternum (breastbone) to form a right and left branch called primary bronchi (singular: bronchus). Each bronchus passes into a lungâ€”the right bronchus into the right lung and the left bronchus into the left lung. The right bronchus is wider, shorter, and straighter than the left. As a result, accidentally inhaled objects (such as pieces of food) most often enter the right primary bronchus. By the time incoming air reaches the primary bronchi, it is warm, moistened, and cleansed of most particles or other impurities. The lungs are two broad, cone-shaped organs located on either side of the heart in the thoracic or chest cavity. They extend from the collarbones to the diaphragm, a membrane of muscle separating the thoracic cavity from the abdominal cavity. The base of each lung rests directly on the diaphragm. The rib cage forms a wall around the lungs, protecting them. At birth, the lungs are pale pink in color. As people age, their lungs grow darker. The inhaling of dirt and other particles increases this aging process, even scarring the delicate tissue of the lungs. Each lung is divided into lobes separated by deep grooves or fissures. The right lung, which is larger, is divided into three lobes. The left lung is divided into only two lobes. Combined, the two soft and spongy lungs weigh about 2.5 pounds (1.1 kilograms). A membrane sac, called the pleura, surrounds and protects each lung. One layer of the pleura attaches to the wall of the thoracic cavity; the other layer encloses the lung. A fluid (pleural fluid) between the two membrane layers reduces friction and allows smooth movement of a lung during breathing. After the bronchi enter the lungs, they subdivide repeatedly into smaller and smaller bronchi or branches. Eventually they form thousands of tiny branches called bronchioles, which have a diameter of about 0.02 inch (0.5 millimeter). This branching network of bronchial tubes within the lungs is called the bronchial tree. The bronchioles branch to form even smaller passageways that open into clusters of cup-shaped air sacs called alveoli (singular: alveolus). The average person has a total of about 700 million alveoli (which resemble clusters of grapes) in his or her lungs. These provide an enormous surface area-roughly the size of a tennis courtâ€”for gas exchange. A network of capillaries surrounds each alveolus. As blood passes through these vessels and air fills the alveoli, the exchange of gases takes place: oxygen passes from the alveoli int

From Yahoo Answers

Question:Do you know some site about respiratory system? 3D

Answers:Both of these are pretty good: www.3dscience.com/3D_Images/Human_Anatomy/Respiratory/index.php www.anatomium.com

Question:please answer my questions here: 1. what are the functions of the circulatory system? 2. what is the ciculation cycle (flow of blood) throughout the heart, lungs, and body? 3. where is the blood is oxygen rich and oxygen poor? 4. which chambers blood enters the heart and leave the heart? 5. what are the different types of blood vessels and what are their functions? 6. where and how gas exchange happens? 7. what are the functions of the blood components? thanks <3 this is just circluartory

Answers:1. what are the functions of the circulatory system? to transport materials around the body 2. what is the ciculation cycle (flow of blood) throughout the heart, lungs, and body? first the deoxygenated blood enters the right side of the heart where it is pumped to the lungs, then the lungs oxygenate the blood where it is pumped to the left side of the heart. From there, it is pumped to the rest of the body and then returned to the right side of the heart. 3. where is the blood is oxygen rich and oxygen poor? rich - arteries poor- veins 4. which chambers blood enters the heart and leave the heart?enters - atriums leaves - ventricles 5. what are the different types of blood vessels and what are their functions? arteries - to supply organs with oxygen veins - to return oxygen poor blood to the heart capillaries - to have oxygen diffuse to the organs and pick up wastes from the organs 6. where and how gas exchange happens? in the lungs - oxygen diffuses into the blood from the lungs and co2 diffuses from the blood to the lungs 7. what are the functions of the blood components? hemaglobin binds oxygen to the blood cells, clotting factors clot cuts and wounds, white blood cells kill bacteria

Question:what is the right order to describe inspiration: A: the air pressure in the air tight pleural cavities decreases B: the muscles between the rib contract to move the ribs cranially and laterally C: Air is drawn down the trachea into the lungs D: the diaphragm contracts and flattens E: the lungs expand to fill the space created

Answers:B and D happen together, followed by A, C then E John H

Question:It is also the respiratory organ in an earthworm

Answers:their skin although they also have lungs but they can respire through their skin.

From Youtube

Respiratory System :Animated respiratory system with external respiration.

The Respiratory System :A podcast covering respiratory surfaces in animals and the human respiratory system. Images from 'Biology: Concepts and Connections' (6th Ed.) by Campbell, Reece, Taylor, Simon, Dickey; Pearson Education