для студентов I курса медицинского института

Зачетная карточка № 15

для студентов I курса медицинского института

(1 семестр)

AIR FLOW

It has long been estimated that air moves from areas of higher pressure to areas of lower pressure just as fluids do. A pressure gradient needs to be established to move air.

Alveolar pressure becomes less than atmospheric one when the muscles of inspiration enlarge the chest cavity, thus lowering the intrathoracic pressure. Intrapleural pressure decreases, causing expansion of the alveoli and reduction of intra-alveolar pressure. The pressure gradient between the atmosphere and the alveoli is to drive air into the airways. The pressure difference necessary to produce gas flow is directly related to the resistance caused by friction at the airway walls.

Lung volume is one of the factors affecting airway resistance. High lung volumes lower airway resistance because the surrounding lung parenchyma pulls airways open by radial traction. Low lung volumes lead to increased airway resistance bescause of a lesser traction on the airways. It is at very low lung volumes that bronchioles may collapse.

It has been shown that the viscosity or density of inspired gases is also able to affect airway resistance. The density of gas increases with deep sea diving, leading to increased resistance and work of breathing. Low-density gases like helium can lower airway resistance. During a forced expiration the airways are compressed by increased intrathoracic pressure. Regardless of how forceful the expiratory effort is, the flow rate plateaux cannot be exceeded. Therefore, the air flow is effort-independent.

Gradient – градиент, уклон

Traction – вытяжение, мышечная тяга

Задания

Найдите в тексте:

1) глаголы-сказуемые в пассивном залоге;

2) усилительный оборот;

3) прилагательные в различных степенях сравнения и сравнительные конструкции;

4) слово one в различных функциях;

5) модальные глаголы и их эквиваленты;

6) причастия в различных функциях.

Дата добавления: 2015-11-05