THE LUNGS

A Research Work On The Internal Organs

Rhexel D. MercedoGrade IV - Trinity

Submitted to:Teacher Janet

Group 5 – The Lungs

Description of the OrganThe lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart. Their principal function is to transport oxygen from the atmosphere into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere. A large surface area is needed for this exchange of gases which is accomplished by the mosaic of specialized cells that form millions of tiny, exceptionally thin-walled air sacs called alveoli.To understand the anatomy of the lungs, the passage of air through the nose and mouth to the alveoli must be studied. The progression of air through either the mouth or the nose, travels through the nasopharynx and oropharynx of the pharynx, larynx, and the trachea (windpipe). The air passes down the trachea, which divides into two main bronchi; these branch to the left and right lungs where they progressively subdivide into a system of bronchi and bronchioles until the alveoli are reached. These many alveoli are where the gas exchange of carbon dioxide and oxygen takes place.Breathing is driven by muscular action; in early tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, which is still found in amphibians. Reptiles, birds and mammals use their musculoskeletal system to support and foster breathing.Medical terms related to the lung often begin with pulmo-, such as in the (adjectival form: pulmonary) or from the Latin pulmonarius ("of the lungs"), or with pneumo- (from Greek πνεύμων "lung").The lungs of mammals including those of humans, have a soft, spongelike texture and are honeycombed with epithelium, having a much larger surface area in total than the outer surface area of the lung itself.Breathing is largely driven by the muscular diaphragm at the bottom of the thorax. Contraction of the diaphragm pulls the bottom of the cavity in which the lung is enclosed downward, increasing volume and thus decreasing pressure, causing air to flow into the airways. Air enters through the oral and nasal cavities; it flows through the pharynx, then the larynx and into the trachea, which branches out into the main bronchi and then subsequent divisions. During normal breathing, expiration is passive and no muscles are contracted (the diaphragm relaxes). The rib cage itself is also able to expand and contract to some degree through the use of the intercostal muscles,

together with the action of other respiratory and accessory respiratory muscles. As a result, air is transported into or expelled out of the lungs. This type of lung is known as a bellows lung as it resembles a blacksmith's bellows.AnatomyIn humans, the trachea divides into the two main bronchi that enter the roots of the lungs. The bronchi continue to divide within the lung, and after multiple divisions, give rise to bronchioles. The bronchial tree continues branching until it reaches the level of terminal bronchioles, which lead to alveolar sacs. Alveolar sacs, are made up of clusters of alveoli, like individual grapes within a bunch. The individual alveoli are tightly wrapped in blood vessels and it is here that gas exchange actually occurs. Deoxygenated blood from the heart is pumped through the pulmonary artery to the lungs, where oxygen diffuses into blood and is exchanged for carbon dioxide in the haemoglobin of the erythrocytes. The oxygen-rich blood returns to the heart via the pulmonary veins to be pumped back into systemic circulation."Lung Disease & Respiratory Health Center".

Human lungs are located in two cavities on either side of the heart. Though similar in appearance, the two are not identical. Both are separated into

lobes by fissures, with three lobes on the right and two on the left. 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.[citation needed] The connective tissue that divides lobules is often blackened in smokers. The medial border of the right lung is nearly vertical, while the left lung contains a cardiac notch. The cardiac notch is a concave impression molded to accommodate the shape of the heart.Each lobe is surrounded by a pleural cavity, which consists of two pleurae. The parietal pleura lies against the rib cage, and the visceral pleura lies on the surface of the lungs. In between the pleura is pleural fluid. The pleural cavity helps to lubricate the lungs, as well as providing surface tension to keep the lung surface in contact with the rib cage.Lungs are to a certain extent "overbuilt" and have a tremendous reserve volume as compared to the oxygen exchange requirements when at rest. Such excess capacity is one of the reasons that individuals can smoke for years without having a noticeable decrease in lung function while still or moving slowly; in situations like these only a small portion of the lungs are actually perfused with blood for gas exchange. Destruction of too many alveoli over time leads to the condition emphysema, which is associated with extreme shortness of breath. As oxygen requirements increase due to exercise, a greater volume of the lungs is perfused, allowing the body to match its CO2/O2 exchange requirements. Additionally, due to the excess capacity, it is possible for humans to live with only one lung, with the one compensating for the other's loss.The environment of the lung is very moist, which makes it hospitable for bacteria. Many respiratory illnesses are the result of bacterial or viral infection of the lungs. Inflammation of the lungs is known as pneumonia; inflammation of the pleura surrounding the lungs is known as pleurisy.Vital capacity is the maximum volume of air that a person can exhale after maximum inhalation; it can be measured with a spirometer. In combination with other physiological measurements, the vital capacity can help make a diagnosis of underlying lung disease.The lung parenchyma is strictly used to refer solely to alveolar tissue with respiratory bronchioles, alveolar ducts and terminal bronchioles. However, it often includes any form of lung tissue, also including bronchioles, bronchi, blood vessels and lung interstitium.Non respiratory functionsIn addition to their function in respiration, the lungs also:

Alter the pH of blood by facilitating alterations in the partial pressure of carbon dioxideFilter out small blood clots formed in veinsFilter out gas micro-bubbles occurring in the venous blood stream such as those created during decompression after underwater diving.Influence the concentration of some biologic substances and drugs used in medicine in bloodConvert angiotensin I to angiotensin II by the action of angiotensin-converting enzymeMay serve as a layer of soft, shock-absorbent protection for the heart, which the lungs flank and nearly enclose.Immunoglobulin-A is secreted in the bronchial secretion and protects against respiratory infections.Maintain sterility by producing mucus containing antimicrobial compounds. Mucus contains glycoproteins, e.g., mucins, lactoferrin, lysozyme, lactoperoxidase. We find also on the epithelium Dual oxidase 2 proteins generating hydrogen peroxide, useful for hypothiocyanite endogenous antimicrobial synthesis. Function not in place in cystic fibrosis patient lungs.Ciliary escalator action is an important defence system against air-borne infection. The dust particles and bacteria in the inhaled air are caught in the mucous layer present at the mucosal surface of respiratory passages and are moved up towards pharynx by the rhythmic upward beating action of the cilia.Provide airflow for the creation of vocal sounds.The lungs serve as a reservoir of blood in the body. The blood volume of the lungs is about 450 milliliters on average, about 9 percent of the total blood volume of the entire circulatory system. This quantity can easily fluctuate from between one-half and twice the normal volume. Loss of blood from the systemic circulation by hemorrhage can be partially compensated for by shunting blood from the lungs into the systemic vesselsThermoregulation via panting (observed in some animals, but not humans).

Parts Of The Human Lungs

Did You Know…

The primary functions of your lungs are to transport oxygen from the air you breathe into your bloodstream while taking away carbon dioxide, which is released into the air when you breathe out.

Most vertebrate animals (animals with spines) have two lungs. Your left and right lungs aren’t exactly the same. The lung on the left side of

your body is divided into two lobes while the lung on your right side is divided into three. The left lung is also slightly smaller, allowing room for your heart.

Can you live without one lung? Yes you can, it limits your physical ability but doesn’t stop you from living a relatively normal life. Many people around the world live with just one lung.

People who have a large lung capacity can send oxygen around their body faster. You can increase you lung capacity with regular exercise.

When resting, the average adult breathes around 12 to 20 times a minute. An average person breathes in around 11,000 litres of air every day. The study of lung diseases is known as pulmonology. As well as other parts of your body and your general health, smoking is bad

for your lungs. Smoking can cause lung cancer among other lung affecting diseases.

Asthma is a common disease that affects the lungs. Asthma attacks happen when your airways narrow after being irritated. The narrow airways make it hard for you to breathe in air.

Pneumonia is a dangerous disease that makes it harder for your lungs to absorb oxygen from the air you breathe.

Other lung diseases include emphysema, tuberculosis and bronchitis.

Location of the Lungs in the Body

Characteristics and Functions of the Lungs

Where are the lungs found?The lungs are found in the chest on the right and left side. At the front they extend from just above the clavicle (collarbone) at the top of the chest to about the sixth rib down. At the back of the chest the lungs finish around the tenth rib. The pleura (the protective membranes which cover the lung) continue down to the twelfth rib. From front to back the lungs fill the rib cage, but are separated by the heart, which lies in between them.

Air that we breathe enters the nose, flows through the pharynx (throat) and larynx (voice box) and enters the trachea (windpipe). The trachea eventually

divides into two parts called bronchi. The right main bronchus (bronchus is the word for one of the bronchi) supplies the right lung; the left main bronchus supplies the left lung. These bronchi then go on to divide into smaller bronchi. Eventually, the bronchi become known as bronchioles – the smallest air tubes in the lungs. This system of air tubes can be thought of as an upside down tree, with the trachea being the main trunk and the bronchi and bronchioles being the branches. The medical term for all the air tubes is 'the respiratory tract'.At the end of the smallest bronchioles are alveoli. Alveoli are tiny sacs that are lined by a very thin layer of cells. They also have an excellent blood supply. The tiny alveoli are the place where oxygen enters the blood and where carbon dioxide (CO2) leaves the blood. The lungs are divided into different parts by what are known as fissures. Fissures are separations of the tissue of the lung that divide the lung into lobes. The right lung has three lobes called upper, middle and lower lobes. The left lung only has two lobes, the upper and lower

What do the lungs do?The lungs' main function is to help oxygen from the air we breathe enter red blood cells. Red blood cells then carry oxygen around the body to be used in the cells found in our organs and tissues. The lungs also help the body to get rid of CO2 gas when we breathe out. There are a number of other jobs carried out by the lungs that include:Changing the pH of blood (whether the blood is more acid or alkali) by increasing or decreasing the amount of CO2 in the body.Filtering out small blood clots formed in veins.Filtering out small gas bubbles that may occur in the bloodstream.

Converting a chemical in the blood called angiotensin I to angiotensin II. These chemicals are important in the control of blood pressure.How do the lungs and breathing work?Breathing in is called inhalation. For air to flow into the lungs there must be a difference in the air pressure in the lungs and the pressure outside. Air is made up of tiny particles including oxygen. If these particles are held together, in a bottle for example, they push on the sides of the bottle. This ‘push’ is what is known as pressure. If the size of the bottle and the amount of air in it stay the same, the pressure in the bottle will stay the same. But the pressure in the bottle can change. If the size of the bottle increases without allowing more air in, the pressure in the bottle goes down. This is because there are fewer particles inside than outside. If you then removed the lid, air would flow into the bottle. This would make the pressure on the inside the same as the outside. Getting fresh air into the lungs works on a similar principle. For inhalation to happen, the lungs must get bigger. This lowers the pressure inside the lungs in comparison to the outside. Air rushes into the lungs to make the pressure equal – a breath in. The size of your lungs varies according to what you are doing. The body has a special set of muscles that help to make the lungs increase in size. The most important muscle of inhalation is the diaphragm. Found beneath the lungs, the diaphragm is a dome-shaped muscle. When this muscle contracts (gets tighter), it flattens and the lungs increase in size. During exercise the diaphragm flattens more than when you are resting. This causes the lungs to expand more, causing more air to flow in.

Exhalation is the process of breathing out. Essentially, this is the opposite of inhalation, except that it is usually a passive process. This means that muscle contractions are not generally required. Exhalation also relies on the difference in pressure between the inside and outside of the lungs. However, in this case, the pressure on the inside is greater than on the outside. This causes air to flow out of the lungs. The lungs receive deoxygenated blood (blood that has lost its oxygen) from the heart through blood vessels called the pulmonary arteries. The deoxygenated blood is then sent to the alveoli. Here, oxygen that has been funnelled through the bronchi and bronchioles can pass across the thin membranes found in the alveoli. A chemical substance within red blood cells, called haemoglobin, has a great attraction to oxygen. Haemoglobin binds oxygen tightly within red blood cells, allowing oxygen to be carried in the

bloodstream. At the same time as oxygen is going into the bloodstream, CO2 is coming out. CO2 moves out of the blood and enters the alveoli. This allows the CO2 gas to be exhaled. Once the blood passing through the lungs picks up oxygen, it is known as oxygenated blood. This blood returns to the heart in the pulmonary veins. Once in the heart, the oxygenated blood is then pumped around the body. The oxygen carried by the red blood cells can then be used in the body’s cells. The basic rhythm of breathing is controlled by the brain. Part of the brain called the brain stem has a special area dedicated to maintaining your breathing pattern. Nerves originating in this area generate electrical impulses. These impulses control the contractions of your diaphragm and the other muscles of breathing. This is all done without thinking. However, other parts of the brain can temporarily overrule the brain stem. This is how we are able consciously to hold our breath or change our pattern of breathing. While the brain controls the basic rhythm, it also receives information from sensors in the body. These sensors are nerve cells and provide information that influences the rate and depth of breathing. The main sensors monitor levels of CO2 in the blood. When the level of CO2 rises, the sensors send electrical impulses to the brain. These impulses cause the brain to send more electrical signals to the muscles of breathing. Breathing gets deeper and faster and more CO2 is exhaled. The blood level of CO2 then decreases and the sensors stop sending signals to the brain.

Heart and lungs showing normal bloodflow

Important Parts of the Lungs

Function of the Important Parts

References:

1. Wikipedia.com2. SlideShare.com3. Science Kids.com4. Patient.info5. Healthline.com6. Answers.com

The bronchial tree consists of branched tubes

leading from the trachea to the alveoli.

The bronchial tree begins with the two

primary bronchi, each leading to a lung.

The branches of the bronchial tree from the trachea

are right and left primary bronchi; these further subdivide until bronchioles

give rise to alveolar ducts which terminate in alveoli.

It is through the thin epithelial cells of the alveoli

that gas exchange between the blood and air occurs

The right lung has three lobes.

The left lung has two lobes. Each lobe is composed of

lobules that contain air passages,

alveoli, nerves, blood vessels, lymphatic

vessels, and connective tissues.