Prim Health

Mechanism of Respiration :

Introduction :-

There are two stages to respiration: inspiration and expiration. The process of respiration involves an organism exchanging gases with its surroundings, mainly oxygen (O₂) and carbon dioxide (CO₂). To facilitate easy air entry into the lungs, inspiration causes the thoracic cage and lungs to expand. In order to facilitate the easy exhalation of air, the thoracic cage and lungs shrink and settle into the preinspiratory position during expiration.
The active phase of regular, silent breathing is inspiration, while the passive phase is expiration. The widening of the thoracic cavity in all of its dimensions caused by the relaxing of the respiratory muscles is followed by the growing popularity of the lungs during inspiration. They’re listed below.

Muscles of Respiration :-

There are two kinds of respiratory muscles:
1. Inspiratory muscles
2. Expiratory muscles.
However, there are two general categories into which respiratory muscles are divided:
1. The primary or major respiratory muscles, which alter the size of the thoracic cage during quiet, normal breathing
2. During forced breathing, accessory respiratory muscles support the main respiratory muscles.

Inspiratory Muscle :-

Inspiratory muscles correspond to those that are used in inspiratory motions.
  Primary inspiratory muscles: The diaphragm receives its supply from the phrenic nerve (C3 to C5), while the external intercostal muscles are supplied by the intercostal nerves (T1 to T11).
The pectorals, elevators of the scapulae, anterior serrati, scalene, and sternocleidomastoid are the supplementary inspiratory muscles.

Expiratory Muscle :-

Primary expiratory muscles
The internal intercostal muscles are connected via the intercostal nerves and are the primary expiratory muscles.
Extramuscular expiratory dysbiosis
The abdominal muscles are further expiratory dysbiosis.

1. Diaphragm :-

 The thoracic cavity and abdominal wall are divided by a dome-shaped muscle, which is composed of horizontally extending fibers that terminate in the central tendon at the center and vertically extending fibers at the periphery. Phrenic nerves (C3, C4, and CS) innervate it. The muscle is connected to mobile structures like the lower ribs along the sides, as well as fixed structures like the vertebrae and the sternum in front.

Mechanism of Inspiration :

1. It starts with the diaphragm contracting, which causes the chest’s vertical width to increase as the diaphragm’s central tendon goes downward. The diaphragm contracts due to signals from the phrenic nerve, which is mostly responsible for this contraction.
2. The lateral and anteroposterior diameters of the chest are increased concurrently with a slight upward shift of the lower ribs. The pressure inside the pleural cavity—the area behind the respiratory tract and the chest wall—drops as a result of the thoracic cavity expanding.
The lungs expand as a result of the decreased intrapleural pressure inside the pleural cavity.
3. As the diaphragm descends, the abdominal muscles relax and the contents of the abdomen move downhill alongside it.
Silent breathing is considered to cause the diaphragm to descend by about 1.5 cm. Because its surface area is 350 square centimeters, the diaphragm can accommodate the entire 500 ml of inspired air during a single quiet breathing session.

Mechanism of Expiration :

When you exhale, your diaphragm relaxes and is raised in the dome by the contraction of your abdominal muscles. This expels air from your lungs as you exhale.
The decrease in thoracic volume increases the pressure in the cavity between the pleura and the lungs themselves (intracerebral pressure).
The decrease in air pressure causes intrapulmonary pressure to increase.
The pressure gradient causes air to move through areas of high pressure (the lungs) to areas of low pressure (the atmosphere).
 

2. Intercostal Muscles :-

The diaphragmatic breathing pattern is the norm.
Important Points
1. There may be differences in the proportional amounts of diaphragmatic and intercostal contribution among people and age groups. The infant’s ribs, for instance, are often horizontal.
On neighboring ribs, the external and intercoastal sets of muscle fibers begin and end.
2. From rib to rib, the muscular fibers of the internal intercostal group run downhill and backward, whereas those of the external intercostal group go forward and downward.
3. The ribs’ cephalad mobility suggests that the upper and lower ribs are fixed in place. The rib cage descends when the lower ribs are fixed by the contraction of the abdominal muscle fibers during a cough or forced inspiration.
4. Intercostal nerves (T1 to T1J) innervate these intercostal muscle fibers. Studies using electromyography show that during forced inspiration, calm inspiration, and forced expiration, the intercostal muscles contract. Normal calm expiration occurs without any electrical change and is caused by the intercostal muscles passively relaxing.

3. Motion of the Thoracic Cag :-

During Inspiration :

The ribs are almost semicircular bones that articulate with the sternum or coastal cartilages at one end and the vertebrae at the other. The elevation of the rib shaft causes the sternum to rise and push forward during inspiration, whereas during expiration, the sternal ends are lower than the vertebral ends. The anteroposterior diameter of the chest increases as a result of the contraction of the external intercostal muscles.

Bucket handle movement- The rotation of the ribs along an axis connecting two points of attachment at the sternum and vertebrae is referred to as “bucket handle motion” in rib motion. The thorax’s crosswise diameter expands as a result of this rotation.
Pump handle movement- These ribs rise when their external intercostal muscles contract, and the sternum moves forward and upward. Pump handle movement is the term for this motion. It widens the thoracic cage’s anteroposterior diameter.

During Expiration :

The reverse occurs when the rib shaft is depressed during expiration. The intercostal muscles, which are in charge of the ribs and sternum’s movement as previously mentioned, relax during expiration. As a result, the thorax’s anteroposterior and transverse diameters shrink, and the lung volume also does.
Diagrammatically, the model illustrates how the diaphragm and thorax change position during inspiration and expiration.

There is variation in the thoracic rib motion. The top ribs are arcs of smaller circles, more or less horizontal than the lower ribs.
All of the superior ribs move during inspiration, which affects the lower ribs. Rather of just focusing on the nearby interspace, their motion is, in some way, the culmination of numerous smaller ones. Owing to these variations, the lower chest experiences larger alterations in the lateral diameter of the thorax than the upper chest. The force of the intercostal contraction and the position of the ribs before the intercostal contraction determine how much costal motion contributes to breathing.

 

4. Motion of the Lungs :-

As the rib cage grows, negative pressure increases within the rib cage during inhalation. This causes the lungs to expand. When you exhale, the chest contracts to the size it was before you inhaled. Furthermore, the pressure in the chest returns to the state it was before you inhaled. This causes the lung tissue to contract, expelling air from the lungs.

Scroll to Top