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The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups: external, internal, and innermost intercostal muscles. All three groups of muscles support the rib cage and participate in the process of forced breathing. The external intercostals facilitate forced inspiration, while the internal and innermost intercostals aid forced expiration.
| Characteristics | Values |
|---|---|
| Number of intercostal spaces | 11 |
| Number of groups | 3 |
| Names of groups | External, Internal, Innermost |
| Function of External Intercostals | Elevate the ribs during forced inspiration |
| Function of Internal Intercostals | Depress the ribs during forced expiration |
| Function of Innermost Intercostals | Aid forced expiration |
| Major muscle group for exhalation | Internal intercostals |
| Function | Change the volume of the thoracic cavity during respiration |
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What You'll Learn
External intercostals facilitate forced inspiration
The intercostal muscles are the muscles that occupy the 11 intercostal spaces between the ribs. They are divided into three groups: external, internal, and innermost intercostal muscles. All three groups of muscles support the rib cage and are accessory respiratory muscles that participate in the process of forced breathing.
The external intercostals are the most superficial intercostal muscles. They promote inhalation by facilitating forced inspiration. They do this by elevating the ribs, thereby expanding the chest wall and increasing the volume of the thoracic cavity. This action is particularly important in activities that require a large volume of air to be inhaled in a short amount of time, such as singing or sports that involve a lot of physical activity.
The function of the external intercostal muscles is to elevate the ribs during forced inspiration. Their fibre orientation means that they are well-suited for this task. The external intercostals remain active during inhalation, promoting the intake of air into the lungs. Once the lungs are full, stretch receptors within the external intercostals signal for them to shut off, which then triggers the internal intercostals to contract for active exhalation.
While the external intercostals facilitate inspiration, the internal and innermost intercostals aid forced expiration. The internal intercostals form the middle layer of the intercostal musculature, originating from the costal groove of one rib and inserting into the superior border of the rib below. They pull down on the rib cage, helping to collapse the lungs and push air out through the mouth and nose during speech or singing.
The innermost intercostals are the deepest intercostal muscles, originating from the costal groove of one rib and inserting into the superior border of the rib below, crossing more than one intercostal space. They assist the internal and external intercostals in their functions, helping to regulate the volume of the thoracic cavity during respiration.
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Internal intercostals aid forced expiration
The intercostal muscles are intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups: external, internal, and innermost intercostal muscles. The internal intercostal muscles form the middle layer of the intercostal musculature. They originate from the costal groove of one rib and insert themselves into the superior border of the rib below.
The internal intercostal muscles aid forced expiration by depressing the ribs. They are the major muscle group for exhalation and are the most important respiratory muscles for normal speech and singing. They pull down on the rib cage, thereby pushing air out of the lungs. The greater the pressure of the escaping air, the louder one's voice.
During vocalization, there is a short period of inhalation followed by a longer period of exhalation. Singers, or at least professional singers, regulate the amount of air they inhale and the speed with which they do so depending on the length and loudness of the phrase they are about to sing. After the lungs have filled with air, the rib cage recoils elastically from a state of complete or near-complete expansion. The external intercostals, which promote inhalation, remain active until receptors within them indicate that the lungs have been fully filled.
Once the lung volume has decreased to a critical value, the external intercostals shut off based on feedback from stretch receptors within them. This signals the internal intercostals to contract, allowing for active exhalation. The internal intercostals do not contract until the lungs have also begun to contract, allowing them to take advantage of the inertia of lung contraction. This is an example of the exploitation of physical mechanics. As air is expelled from the lungs, the activity of the internal intercostals increases.
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Innermost intercostals are the deepest muscles
The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups, namely external, internal, and innermost intercostal muscles, which are further categorised as superficial to deep. All three groups of muscles support the rib cage and are accessory respiratory muscles that participate in the process of forced breathing.
The external intercostals are the most superficial intercostal muscles. They facilitate forced inspiration by elevating the ribs. The internal intercostals form the middle layer of the intercostal musculature. They originate from the costal groove of one rib and insert themselves into the superior border of the rib below. The internal intercostals aid in forced expiration by depressing the ribs.
The innermost intercostals are the deepest intercostal muscles. They originate from the same costal groove as the internal intercostals but posteriorly. They follow a similar course as the internal intercostals, inserting themselves into the superior border of the rib below. The innermost intercostals, along with the internal intercostals, aid in forced expiration. The blood supply to the innermost intercostals, similar to the internal intercostals, comes from the anterior and posterior intercostal arteries, as well as the costocervical trunk.
The innermost intercostal muscles, along with the other intercostal muscles, play a crucial role in changing the volume of the thoracic cavity during respiration. They are innervated by the intercostal nerves, which arise from the anterior rami of spinal nerves T1 to T11. The innermost intercostals are also involved in processes such as vocalization, where they contract to allow for active exhalation and the production of speech and singing.
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Intercostals are accessory respiratory muscles
The intercostal muscles are intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups: external, internal, and innermost intercostal muscles. All three groups of muscles support the rib cage and are accessory respiratory muscles that participate in the process of forced breathing.
The external intercostals are the outermost layer of intercostal muscles. They lie directly under the skin and originate from the lower border of the rib above, running obliquely and inserting into the upper border of the rib below. The function of the external intercostal muscles is to elevate the ribs during forced inspiration, thereby expanding the chest wall during inhalation. They remain active until receptors within them indicate that the lungs have been fully filled.
The internal intercostals are the intermediate layer of intercostal muscles. They originate from the costal groove near the inferior border of the rib above and insert into the upper border of the rib below. They form the middle layer of the intercostal musculature. The internal intercostals aid in forced expiration by depressing the ribs and helping to collapse the lungs during exhalation. They are the most important respiratory muscles for normal speech and singing, as they propel air out through the mouth and nose.
The innermost intercostals are the deepest layer of intercostal muscles. They originate from the costal groove of one rib and insert into the superior border of the rib below, crossing more than one intercostal space. They assist the internal and external intercostals in their function. All three layers of intercostal muscles work together to change the volume of the thoracic cavity during respiration.
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Intercostals support the rib cage
The intercostal muscles are intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups: external, internal, and innermost intercostal muscles. All three groups of muscles support the rib cage and are accessory respiratory muscles that participate in the process of forced breathing.
The external intercostals are the outermost layer of intercostal muscles. They lie directly under the skin and originate from the lower border of the rib above, running obliquely and inserting into the upper border of the rib below. The function of the external intercostal muscles is to elevate the ribs during forced inspiration, thereby expanding the chest wall during inhalation. They remain active until receptors within them indicate that the lungs have been fully filled.
The internal intercostals are the intermediate layer of intercostal muscles. They originate from the costal groove near the inferior border of the rib above and insert into the upper border of the rib below. They form the middle layer of the intercostal musculature. The internal intercostals depress the ribs during forced expiration, helping to collapse the lungs during exhalation. They are the major muscle group for exhalation and are the most important respiratory muscles for normal speech and singing, as they propel air out through the mouth and nose.
The innermost intercostals are the deepest layer of intercostal muscles. They originate from the costal groove of one rib and insert into the superior border of the rib below, crossing more than one intercostal space. They assist the external and internal intercostals in their function.
In summary, the intercostal muscles support the rib cage by aiding in the process of breathing. The external intercostals facilitate inspiration, while the internal and innermost intercostals aid expiration. Together, they help to regulate the volume of the thoracic cavity during respiration.
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Frequently asked questions
Intercostal muscles are the muscles that occupy the 11 intercostal spaces within the rib cage. They are divided into three groups: external, internal, and innermost intercostal muscles.
The external intercostal muscles elevate the ribs during inhalation, facilitating forced inspiration. They remain active until receptors within them indicate that the lungs have been fully filled.
The internal intercostal muscles depress the ribs during forced exhalation, aiding in forced expiration. They contract after the lungs have begun to contract, taking advantage of the inertia of lung contraction.
The innermost intercostal muscles are the deepest layer of intercostal muscles, assisting the internal and external intercostals in their function. They help in changing the volume of the thoracic cavity during respiration.
The intercostal muscles are accessory respiratory muscles that participate in the process of forced breathing. The external intercostals promote inhalation, while the internal and innermost intercostals facilitate exhalation.
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