Movements of Breathing Mechanism of Inhalation and Exhalation

Respiration consists of rhythmically repeated inhalations and exhalations. Inhalation takes place as follows: the muscles participating in inhalation contract under the influence of nerve impulses. While contracting the diaphragm descends (flattens) increasing the vertical size of thoracic cavity. Contraction of the external intercostal and certain other muscles elevates the ribs increasing both the anteroposterior and transverse size of the thoracic cavity. Thus muscular contrac­tion increases the capacity of the thorax. Since the pleural cavity contains no air and the pressure in it is negative both lungs expanding, the air pressure in them drops and atmospheric air rushes into the lungs through the air passages. Hence an inhalation involves a contraction of muscles, an increase in the capacity of the thorax, an expansion of the lungs, and entrance of atmospheric air into the lungs through the air passages.

Inhalation is followed by exhalation. The muscles participating in inhalation relax, the diaphragm rising. The ribs drop as a result of contraction of the internal intercostal and other muscles and because of their own weight. The capacity of the thorax decreasing, the lungs be­come compressed, the pressure in them rises and the air rushes out through the air passages.

The respiratory movements are rhythmic. An adult at rest makes 16—20 respiratory movements per minute, children make more move­ments (a newborn child makes up to 60 movements a minute). Physical exertion, particularly in untrained people, is usually accompanied by faster respiration. Accelerated respiration is also observed in many dis­eases. Sleep is accompanied by a slowing of respiration.

Movements of breathing. Changes in the volume of air in the lungs are brought about by movements both of the diaphragm and ribs. Con­traction of the diaphragm increases the length of the capacity of the chest, while the upward movement of the ribs increases the cross sec­tion of the chest. Inspiration is due to contraction of the diaphragm and of the muscles attached to the ribs. These contractions are in­duced by nervous impulses. Expiration is a less active process than inspiration, for when the muscles relax the elasticity of the lungs them­selves tends to drive out the air previously inhaled. Any impediment to breathing due to pressure or constriction in the respiratory passages is especially noticeable during expiration, because it is usually of a pas­sive character. When the volume of breathing is increased by physical exercise many assessory muscles are involved while producing deeper inspirations. Expiration also involves a vigorous action of the abdom­inal muscles.

Послетекстовые упражнения:

1) Прочтите и переведите текст А. Первый абзац переве­дите письменно. 2) Найдите в тексте А ответы на следующие вопросы и зачитайте их.

1. How is contraction of the muscles participating in inhalation regulated? 2. Why does the size of the thoracic cavity increase? 3. When is impediment to breathing especially noticeable? 4. What processes does the inhalation (exhalation) involve? 5. What do the movements of the diaphragm and ribs bring about?

3) Составьте письменно план текста А.

Упражнение 1. Подберите пары синонимов.

inspiration, to take place, to induce, per minute, respiration, breathing, to cause, to produce, inhalation, to occur, a minute

Упражнение 2. Подберите пары антонимов.

to compress, inhalation, to contract, to increase, to drop, upward, to decrease, to rise, downward, exhalation, to expand, to relax

Упражнение 3. Переведите следующие предложения, определите функции причастий.

1. For mechanical analysis the respiratory system may be divided into three parts: the gas (in the airways and air spaces), the lung structure, containing the gas, and the thorax containing the lungs. 2. Dynamic increases in airway resistance during expiration set the limit on the ventilatory capacity of the respiratory system in normal and diseased lungs. 3. While flowing through the capillaries the blood accepts the oxygen from the alveolus and deposits carbon dioxide into the alveolus. 4. Airway pressures are not everywhere equal, being most negative in the alveoli. 5. During inspiration pleural pressures become more negative, the widening tendency increasing.

Упражнение 4. Опишите анатомическое строение легких, используя текст. Направлено на развитие компетенции ОК-6.