Anatomy/Respiratory System

The respiratory system is a topic of the event Anatomy.

Mechanics
The Respiratory system is controlled in mammals by the diaphragm muscle. When the diaphragm relaxes, the thoracic cavity decreases in size. However, when the muscle contracts, it pulls downward, adding size to the thoracic cavity. While this happens, the intercostal muscles pull upwards on the ribcage, adding more space to the thoracic cavity. When the diaphragm relaxes, it pushes upward on the lungs, along with the intercostal muscles pushing downward on the ribcage. These muscles decrease the volume while increasing their internal pressure. When the diaphragm contracts, the lungs gain volume and lose pressure, causing a partial vacuum. Having no choice at this point but to follow the laws of nature, air follows the pressure gradient and rushes into the lungs.

There are two main breathing patterns: quiet breathing and forced breathing.

In quiet breathing, muscles contract voluntarily to let air in the lungs (an active process), but muscles relax when you exhale (passive process).

In forced breathing, muscles contract voluntarily in both inspiration and expiration.



Parts of the Respiratory System
Nasal Cavity- The network of air space in the nose, filled with mucus to trap dust and particles.

Pharynx- The pharynx is a shared passageway between the respiratory and the digestive system. It is located in the throat.

Larynx- The entrance to the airway. Has an epiglottis to prevent food from entering, and vocal cords to produce sound.

Trachea- The tube that connects to the bronchi.

Bronchi- The tubes that branch out to bronchioles.

Bronchioles- The tubes that connect to terminal bronchioles.

Terminal Bronchioles- The bronchioles that connect to alveoli.

Lungs- Expands and deflates to control breathing, contains alveoli and bronchioles.

Alveoli- The site of gas exchange between the airway and the blood. Diaphragm- Contracts and relaxes to expand/deflate the chest cavity. The lungs are on top of the diaphragm.

Measures of Pulmonary Ventilation
Minute ventilation 	= tidal volume * respiratory rate

the total volume of gas entering the lungs per minute.

Alveolar ventilation 	= (tidal volume - dead space) * respiratory rate

the volume of gas per unit time that reaches the alveoli, the respiratory portions of the lungs where gas exchange occurs.

Dead space ventilation 	= dead space * respiratory rate

the volume of gas per unit time that does not reach these respiratory portions, but instead remains in the airways (trachea, bronchi, etc.).

Control of Breathing
Unlike digestion, pupil contraction, and the beating of your heart, breathing is controlled both unconsciously and consciously. Few other actions are like this, blinking being another example. When you are not thinking about your breathing, such as when you are at rest, you will unconsciously regulate your air intake. However, when performing activities such as exercise, talking, or swimming, you are consciously deciding when to breathe. When not being actively controlled, breathing is controlled by the brain stem. The brain stem will automatically regulate breathing as needed by the body. For instance, when you exercise, you need ATP for muscle contraction to occur. When you strength train, you enter the zone called anaerobic exercise. This triggers anaerobic metabolism, which causes a buildup of lactic acid in the body. This lowers blood pH, which can be fatal. The brain stem then increases the rate of breathing.

Gas Exchange and Transport
Gas exchange

1. Oxygen in air dissolves into fluid lining the alveolus and diffuses through alveolar wall and capillary wall.

2. Oxygen enters blood plasma inside capillary. Gas exchange occurs in the capillary beds.

3. Oxygen binds to oxyhemoglobin in red blood cells.

4. Carbon dioxide diffuses out of blood plasma and into air in alveolus.

5. Oxygenated blood leaves heart and circulates through capillaries to tissue.

6. Red blood cells arrive at tissue, rich in oxygen that binds to the hemoglobin in the tissue.

7. Oxygen leaves hemoglobin in red blood cells and diffuses across blood capillary walls and into tissue cells.

8. Carbon dioxide diffuses out of tissue into blood plasma, which carries red blood cells into lungs. Completely dissociated hemoglobin enters the lung in red blood cells ready to be oxygenated.

Transport of gases in the blood is essential to life. The gases are carried in the blood in one of two ways: in the blood plasma or combined with hemoglobin.

Diseases of the Respiratory System
Hypoxia Hypoxia is a condition where the whole body or a certain region of the body is deprived of oxygen. The oxygen content within the arterial blood is extremely low. Hypoxia is normally caused by flying above altitudes of 10,000 feet in unpressurized airplanes. Hypoxia is usually a slow-developing sickness, starting with symptoms such as headache, fatigue, and nausea. Severe symptoms include seizures, discoloration of skin, and death.

Oxygen Toxicity Oxygen Toxicity is a result from breathing molecular oxygen at high pressures such as from oxygen tanks in scuba diving. Oxygen toxicity can effect your central nervous system and pulmonary functions.

Chronic Obstructive Pulmonary Diseases (COPD) COPD's are very common lung diseases. There are 2 main forms of COPD- Chronic Bronchitis and Emphysema. Both are normally caused by smoking or air pollution. In chronic bronchitis, the bronchi become inflated, and goblet cells produce unusually high amounts of mucus. This is seen by mucus-spitting coughs as well as fatigue. Emphysema is a long term disease in which lung tissue and alveolar walls are destroyed, making the lungs have less surface area. As a result, emphysema can cause a shortness of breath because the lungs are not able to absorb as much oxygen.

Asthma Asthma is a disorder in which the airways are of the lung swell and narrow. This can lead to wheezing, shortness of breath and coughing. Asthma is usually caused by allergic reactions or irritants in the air.

Lung Cancer Cancer of the lungs

Acute Rhinitis Acute Rhinitis is a fancy word for the common cold. The common symptoms are a runny nose, wheezing, teary eyes, and impairment of smell. It is caused by bacterial/viral infections of the nose as well as inhaled irritants.

Laryngitis Laryngitis is basically inflammation of the vocal folds. This is usually caused by viruses.

Pneumonia Pneumonia is an infection of the lungs. Common symptoms include coughing, fever, and shaking chills. This can be treated by injections of fluids or antibiotics into your veins, as well as oxygen therapy.

Sleep apnea Sleep apnea is a sleeping disorder which is characterized by pauses in breathing (apneas) that occur unnaturally in sleep. This can be tested for by a polysomnography. Sleep apnea can be treated through surgery or breathing therapy, depending on the results of the test.

Tuberculosis Tuberculosis is a contagious bacterial infection of the lungs (but can spread to other organs). Tuberculosis is shown by weight loss, excessive sweating, and coughing up blood. It can be treated with drugs such as Isoniazid and Rifampin.