Functions and functioning of the respiratory system the respiratory system provides for the tissues of oxygen and carbon dioxide removed.
Respiration is composed of:
- Pulmonary ventilation, which is the movement of air into, and means out of the alveoli,
- Diffusion of oxygen and carbon dioxide between the blood and alveoli,
- Transport of oxygen and carbon dioxide to and from the tissue
- Regulation of the respiration.
Functions and functioning of the respiratory system
Mechanism of pulmonary ventilation
Lung volume increases and decreases when the thorax is larger and smaller. Each time when the length and thickness of the chest increases or decreases at the same time, there occur changes in lung volume.
- The diaphragm (diaphragm) is responsible for breathing calmly. During inhalation (= inspiration), causing contraction of the diaphragm for the downward movement of the lungs. During exhalation, the diaphragm relaxes and creates the elasticity of the lungs, the pressure of the chest wall and the abdominal contents for moving back to the lungs.
- During breathing, the elastic forces are not strong enough for a quick expiration. The extra strength caused by contraction of the abdominal muscles.
Up and down movement of the rib cage causing the expansion and contraction of the lungs when the rib cage moves up, the breast volume and thus the lung volume increases.
- Muscles pulling the ribcage up, his muscles to help with the inspiration. These include them. Sternocleidomastoideus, them. Serrati, them. Scalene and external intercostal muscles.
- Muscles that pull down the rib cage, his muscles that help with the expiration. These include internal intercostal muscles and m. Recti abdominous. Other abdominal muscles are pressing the abdominal contents against the diaphragm.
The movement of air into and out of the lungs
Pleural pressure is the fluid pressure in the space between the lung pleura the pleura and the chest wall. The normal pleural pressure at the start of inspiration is -5 cm water pressure is the suction needed to keep the lungs open. During inspiration, causes expansion of the chest for an increase in the negative pressure and may increase to -7.5 cm water pressure. Alveolar pressure is the pressure in the alveoli. When the glottis is open, there is no air flow, the pressure within the respiratory tract is equal to atmospheric pressure, and will, therefore, be 0 centimeters of water pressure.
- During inspiration, the pressure drops in the alveoli to -1 cm of water pressure causes the inflow of 0.5 liters of air in the lungs during 2-second inspiration.
- During exhalation, the opposite happens: the alveolar pressure rises to 1-centimeter pressure. The 0.5 liter of air inhaled removed during the 2-3 seconds expiration.
Compliance of the lung is the change in lung volume for each unit change in transpulmonary pressure. Transpulmonary pressure, the difference in pressure between alveolar pressure and pleural pressure. The average total compliance (imparting) of the two lungs is in a healthy adult is 200ml / cm of water. Compliance is dependent on the following elastic forces:
- Elastic forces of lung tissue are dependent of elastin and called fibrils.
- Elastic forces caused by surface tension in the alveoli determine two-thirds of the total elastic force of healthy lungs.
Surfactant, surface tension pneumothorax
Water molecules attract each other. The water that is present in the alveoli, pulling each other. As a result, air can be squeezed out of the lungs and fold in the lungs. However, the net effect is an elastic force of the entire lung, which is called the surface elastic force. Surfactant (a substance in the lungs) increases compliance by reducing the alveolar surface tension. A surfactant produced by type II alveolar epithelial cells. The most important component of phospholipid surfactant is dipalmitoylphosphatidylcholine. Surfactant spreads over the inside of the alveoli and reduces the surface tension to a twelfth of the surface tension of small water alveoli threaten earlier collapse the tendency for collapsing alveoli is inversely proportional to the radius of the alveoli.
- Press = (2 x Surface) / Radius
Surfactant, pulmonary mutual dependence, and connective tissue are important in the stabilization of the size of the alveoli. When some alveoli are small, and the other large, small alveoli tend to collapse earlier. These large alveoli would be even greater. This instability of the alveoli occurs for the following reasons not to:
- Mutual dependence. The alveoli, alveolar tubes and other spaces with air distributing each other in a manner that there can be no small alveoli for since they share the same space.
- Connective tissue. The lung consists of approximately 50,000 functional units containing one or more alveolar tubes and alveoli. These are all surrounded by fibrous septa.
- Surfactant. Surfactant reduces the surface tension; thereby preceding factors keep open the lung. When an alveolus is liable to be smaller, the surfactant molecules are pressed into one another, so that the surface tension decreases still further.
Lung volume to high capacities.
The lung volumes and lung capacities measured with a spirometer.
- Tidal volume (Vt) is the amount of air (about 500 ml), which is inhaled or exhaled with each breath.
- Inspiratory reserve volume (IRV) is the extra amount of air (about 3000 ml), which in addition to the tidal volume can still be inhaled.
- Expiratory reserve volume (ERV) is the additional amount of air (about 1000 ml) to give after an average expiration can still exhale with power.
- Residual volume (RV) is the volume (about 1200 ml) which remains in the lungs after a powerful exhalation.
Lung Capacity is the combination of two or more lung volumes.
- Inspiratory capacity (IC) is the tidal volume increased with the inspiratory reserve volume (about 3500 ml). It is the amount of air that can inhale after a regular inspiration.
- Functional spare capacity (FRC) is equivalent to the expiratory reserve volume, residual volume together. It is the amount of air remaining after a normal expiration.
- Vital capacity (VC) equals the inspiratory reserve volume, tidal volume, and expiratory reserve volume together. It is the maximum amount of air that can be exhaled after a maximum inhalation (about 4600 ml).
- Total lung capacity (TLC), the maximum volume to which the lungs can be stretched (5800 ml). It equals the vital capacity and residual volume together.
Minute Ventilation and Alveolar ventilation
The AMV is the total amount of fresh air that moves every minute by the respiratory tract. The AMV is equal to the tidal volume multiplied by respiratory rate. Normally, the tidal volume of 500 ml. Normally, the respiratory rate 12 times per minute. The AMV is 6L / min.
Alveolar ventilation is the rate at which new air inhaled to reach the areas of the lungs where gas exchange can take place. During inspiration, not all air enters the gas wiselings genie den of the lung, but fill the dead space. The alveolar volume is the amount of fresh air that reaches the alveoli.
- VA=Freq X (VT-VD)
VA is the alveolar volume per minute. Freq is the respiratory rate per minute. VT is the tidal volume, and VD is the volume of air in the dead space. With the normal tidal volume of 500 ml, the volume is in the dead space 150 ml. The alveolar volume is then: X 12 (500-150) = 4200 ml / min.
There are three types of dead air spaces:
- Anatomical dead space is the amount of air in the airways which do not take part in gas exchange.
- Alveolar dead space is the volume of air in the gas wiselings hidden that can not participate in the actual gas exchange.
- Physiological dead space is the sum of the above points.