Exam 3 Review:  Chapter 22:  Breathing

inspiration - The act of drawing in, inhaling, air into the lungs, using the external intercostals and, if necessary, the diaphragm, to increase the volume of the pleural cavities to create a favorable negative pressure gradient; this action is normally under autonomic control by means of the inspiratory area of the medullary rhythmicity area.

intrapleural pressure - The pressure (i.e., the force applied uniformly against the pleural cavity walls) within the pleural cavity, which, in life, is always negative; this negative force acts as a suction to keep the lungs inflated; the negative intrapleural pressure is due to the surface tension of the alveolar fluid, the elasticity of the lungs, and the elasticity of thoracic wall; changes in the intrapleural pressure contribute to the movement of air during ventilation; the intrapleural pressure between breathes is less than atmospheric pressure by about 4 mm Hg.  aka - intra-thoracic pressure

intra-alveolar pressure - The pressure (i.e., the force applied uniformly against the alveolar  walls) within the alveoli; when this pressure is less than atmospheric pressure, air will move into the alveoli; when this pressure is greater than atmospheric pressure, air will move out of the alveoli.


transpulmonary pressure - The difference in pressures (i.e., pressure gradient) between intra-alveolar pressure and intrapleural pressure during an inspiration or an expiration.

  Inspiration Expiration
Intra-Alveolar Pressure* -3.0 mm Hg +3.0 mm Hg
Intrapleural Pressure* -6.0 mm Hg -3.0 mm Hg
Difference in Pressures*

(i.e., Pressure Gradient)*

+3.0 mm Hg

[ -3 - (-6) = +3 ]

+6.0 mm Hg

[ +3 - (-3) = +6 ]

[* Note:  All pressures in the table are compared to the atmospheric pressure at whatever location.]


expiration  - The act of forcing out, exhaling, air from the lungs, using the internal intercostals and the natural elastic recoil of the lungs, chest wall, and the relaxing diaphragm (and gravity), to decrease the volume of the pleural cavities to create a favorable positive pressure gradient; this action is normally under autonomic control by means of the expiratory area of the medullary rhythmicity area.

elastic recoil - The ability of the lungs and the alveoli to return to their original volume and shape passively as a result of the flexible ductile strength of the elastic tissue in the alveolar, lobular, and lobar walls of the lungs; this ability promotes passive lung constriction and outward air flow during expiration and contributes to the always negative intrapleural pressure; any loss of elastic recoil will require increased muscular assistance with exhalation.

diaphragmatic breathing - Ventilation produced chiefly by movements of the diaphragm and abdominal muscles, i.e., inspiration using the diaphragm and expiration using the abdominal muscles.

costal breathing - Ventilation produced chiefly by movements of the ribs, i.e., inspiration using the external intercostals and expiration using the internal intercostals.

compliance - The ability of the alveoli and lung tissue to expand on inspiration; in clinical terms it is defined as the volume increase in the lungs per unit increase in the lung pressure; while clearly not a complete description of the pressure-volume properties of the lung, it is nevertheless useful in practice as a measure of the comparative stiffness of the lung; the stiffer the lung, the less the compliance; compliance is reduced by diseases which cause an accumulation of fibrous tissue in the lung or by edema in the alveolar spaces; it may be secondarily increased in progressed pulmonary emphysema due to the loss of elastic alveolar tissue and also similarly with increasing age, probably because of alterations in the elastic alveolar tissue in both cases.

airway resistance - The measure of the ease with which air flows through tubular respiratory structures; higher resistance occurs in smaller tubes such as bronchioles and alveoli which have not emptied properly; it is a ratio of pressure to flow (R=V/I); thus, for the determination of airway resistance, intra alveolar pressure and airflow measurements are required.

pulmonary perfusion - The injection or pumping of blood into the pulmonary circulation in order to reach the lungs and alveolar capillary beds to supply lung tissues with nutrients and permit the exchange of oxygen and carbon dioxide between the alveolar air and the blood; the actual rate is dependent on cardiac output and appropriate flow through the pulmonary circulation.

Describe:

1. The pulmonary ventilation pressure changes during inspiration and expiration.

Pulmonary pressure changes during ventilation are quite modest.  Intrapulmonary pressure (in the alveolar spaces of the lungs) varies by only a mm or Hg or two from atmospheric pressure under most circumstances.  During inspiration, the intrapulmonary pressure (in the alveolar spaces of the lungs) is further reduced, by 2 or 3 mm Hg compared to atmospheric pressure, when thoracic cavity (pleural space) volume is expanded by the elevation of the ribs by the contraction of the external intercostals and, perhaps, by the contraction and depression of the diaphragm.  During expiration the intrapulmonary pressure (in the alveolar spaces of the lungs) is slightly increased, by 2 or 3 mm Hg compared to atmospheric pressure, when thoracic cavity (pleural space) volume is reduced by the elastic recoil of the ribs and the action of gravity and, perhaps, by the contraction of the internal intercostals and, if needed, the abdominals.

 7.  The names and actions of the muscles involved in ventilation (external respiration).

Inspiration
external intercostals elevate ribs and therefore increase the volume of the pleural cavities
diaphragm depress the inferior wall of the thoracic cavity and, therefore, increase the volume of the pleural cavities
Expiration
internal intercostals compress and lower the ribs and therefore decrease the volume of the pleural cavities
abdominals compress the abdominal cavity which elevates the abdominal organs and passively elevates the diaphragm and, therefore, decreases the volume of the pleural cavities