The lungs are the essential organs for respiration in air-breathing animals. In humans, the trachea divides into the two main bronchi that enter the roots of the lungs, continuing to branch into bronchioles and alveolar sacs made up of clusters of alveoli where gas exchange occurs. The principal function of the lungs is to transport oxygen into the bloodstream and release carbon dioxide, with differences in lobe structure between human and pig lungs.

1. THE LUNGS

2. The lung is the essential respiration organ in all air-breathing animals, including most tetra pods. In mammals and the more complex life forms, the two lungs are located in the chest 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. This exchange of gases is accomplished in the mosaic of specialized cells that form millions of tiny, exceptionally thin-walled air sacs called alveoli. In 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.

3. 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.

4. THE RESPIRATORY SYSTEM (PIG) The respiratory system of the pig commences at the nostrils which lead into two nasal passages. These contain the dorsal and ventral turbinate bones. The ventral turbinate's consist of four thin main bones, two on each side separated by a cartilaginous septum. You can imagine these as four hair curlers placed inside the nose.

6. Parts of Lungs Trachea The trachea, also called that takes air to the lungs. The trachea, which is connected at the nose and mouth, is a bony, hollow tube in the front of the neck. This tube continues down the chest where it branches to the left and right lung. Lobes The lungs are sectioned in lobes. The right lung is larger than the left, so it has more lobes. The right lung has three lobes, while the left lung only has two lobes. The left lung is smaller to compensate for the space taken by the heart. The heart rests between the right and left lung but is situated more on the left. Bronchioles Bronchioles are structures that branch in the lungs. The bronchioles connect on one side at the trachea and terminate at the alveoli. The bronchioles carry the air to the alveoli, where gas exchange occurs. They are also the first step after the alveoli in bringing carbon dioxide out of the lungs when you exhale.

7. Alveoli The alveoli are tiny sacs responsible for gas exchange. These sacs hold air, but they are also surrounded by capillaries. The capillaries have a tiny wall and are filled with blood. The alveoli supply the blood with the oxygen that is inhaled. When you exhale, the blood exchanges carbon dioxide for oxygen. The carbon dioxide is then removed from the body. Diaphragm The diaphragm is the muscle responsible for inflating and expanding the lungs. When your inhale, the diaphragm muscle contracts and presses the bottom parts of the left and right lung, causing the lungs to inflate. When you exhale, the diaphragm relaxes and the lungs are returned to their original shape.

8. FUNCTIONS OF LUNGS The lung is a magnificent organ that performs a multitude of vital functions every second of our lives. Breathing is the most essential of these functions. With each breath, the lungs take in oxygen and remove carbon dioxide. The lungs are also important in the body's defense against infection and other harmful environmental factors. While the nose is the first line of defense against inhaled harmful materials, the lungs provide the second line of defense. Inhaled particles (smoke, pollution) or infectious agents (bacteria, viruses) pass through the mouth or nose and lodge in the lungs.

9. DIFFERENCES HUMAN LUNGS AND PIG The lungs of mammals have a spongy texture and are honeycombed with epithelium, having a much larger surface area in total than the outer surface area of the lung itself. The lungs of humans are a typical example of this type of lung. Pigs have 4 lobes in the right lung and 2 lobes in the left lung. Humans have 3 lobes in the right lung and 2 lobes in the left lung.

10. DISEASES Diseases of the human lung belong to respiratory diseases. The following is a list of important medical conditions involving the lung. Many of these are caused or worsened by smoking. Lung disorders are generally handled by general practitioners, although patients may be referred to a pulmonologist. Lung cancer Emphysema is an enlargement of the air spaces in the lung, making it hard to breathe. Asthmais an immunological disease which causes the bronchioles to narrow by inflammation and spasm of the lining of the airway wall. Cystic fibrosis is a hereditary disease which causes the lung to produce abnormally viscous mucus. A pulmonary embolismoccurs when a blood clot obstructs an artery leading to the lung. Tuberculosisis a transmittable bacterial infection of the lung, the most common infectious disease today. Pneumonia is an infection of the lung, caused by bacteria, viruses or fungi. Pneumoconiosis, an occupational lung disease caused by the inhalation of dust. Bronchitisis an inflammation of the bronchi. A collapsed lung (pneumothorax) can occur when one or both walls of the pleural cavity are penetrated by injury, allowing air to enter. In pulmonary edemafluid from the capillaries enters the alveoli. This can be caused by weakness of the left side of the heart (resulting in a blood holdup in the lung), altitude sickness, or rarely inhaling toxic gases. Lung pinprick condition is a hereditary disease which results in decreased lung capacity and occasional shortness of breath.

11. LUNG CANCER