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Intercostal muscles are the intrinsic rib cage muscles that occupy the 11 intercostal spaces between the ribs. They are divided into three groups: external, internal, and innermost intercostal muscles. These muscles are crucial for breathing as they change the size of the chest cavity by expanding and contracting the rib cage. The external intercostals facilitate forced inspiration, while the internal and innermost intercostals aid in forced expiration.
| Characteristics | Values |
|---|---|
| Definition | Muscles that link the ribs together and contribute to breathing |
| Location | Between the ribs |
| Function | Expansion and contraction of the chest cavity |
| Groups | External, internal, and innermost intercostal muscles |
| Number of Internal Intercostal Muscles | 11 |
| Innervation | Anterior rami of spinal nerves T1-T11 |
| Blood Supply | Anterior and posterior intercostal arteries, costocervical trunk, internal thoracic, and musculophrenic arteries |
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What You'll Learn
- Intercostal muscles are a group of muscles located between the ribs
- They occupy the 11 intercostal spaces
- They are divided into three groups: external, internal, and innermost intercostal muscles
- They support the rib cage and are accessory respiratory muscles
- They are innervated by the anterior rami of spinal nerves T1-T11
Intercostal muscles are a group of muscles located between the ribs
The external intercostal muscles facilitate forced inspiration by elevating the ribs and bending them open, thereby expanding the chest cavity. They originate from ribs 1–11 and insert on ribs 2–12. The internal intercostal muscles, on the other hand, aid in forced expiration by depressing the ribs and bending them inward, reducing the size of the chest cavity. They originate from the costal groove of one rib and insert on the superior border of the rib below.
The innermost intercostal muscles are the deepest layer of intercostal muscles, originating from the costal groove of one rib and inserting on the superior border of the rib below. They work together with the external and internal intercostals to assist in breathing and maintain the integrity of the thoracic cage.
The intercostal muscles are innervated by the intercostal nerves and supplied by the intercostal arteries, with blood supply also coming from the costocervical trunk, internal thoracic, and musculophrenic arteries. Their function is crucial in the respiratory process, allowing for the expansion and contraction of the chest cavity, which is essential for breathing.
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They occupy the 11 intercostal spaces
The intercostal muscles occupy the 11 intercostal spaces between the 12 ribs. They are divided into three groups: external, internal, and innermost intercostal muscles. Each group has distinct functions and anatomical positions.
The external intercostal muscles, also known as intercostalis externus, aid in quiet and forced inhalation. They originate from ribs 1–11 and insert into ribs 2–12. During forced inspiration, these muscles elevate the ribs and bend them open, expanding the transverse dimensions of the thoracic cavity. The muscle fibres of the external intercostals are directed downwards, forwards, and medially in the anterior part.
The internal intercostal muscles, or intercostalis internus, aid in forced expiration, while quiet expiration is a passive process. They originate on ribs 2–12 and insert on ribs 1–11. The internal intercostals are responsible for depressing the ribs and bending them inward, reducing the transverse dimensions of the thoracic cavity. Their muscle fibres are directed downwards, forwards, and laterally, forming a right angle with the external intercostal muscle.
The innermost intercostal muscles, or intercostalis intimus, are deep layers of the internal intercostal muscles, separated by a neurovascular bundle. Their muscle fibres are directed in the same way as the internal intercostals. The innermost intercostals assist the internal intercostals in depressing the ribs during forced expiration.
All three groups of intercostal muscles support the rib cage and participate in forced breathing. While the external intercostals facilitate forced inspiration, the internal and innermost intercostals aid in forced expiration. These muscles also help move the chest wall and contribute to the mechanical aspect of breathing by expanding and shrinking the chest cavity.
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They are divided into three groups: external, internal, and innermost intercostal muscles
The intercostal muscles are the muscles that occupy the 11 intercostal spaces between the ribs. They are divided into three groups, from superficial to deep: 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 are the most superficial intercostal muscles. They originate on ribs 1–11 and have their insertion on ribs 2–12. The function of the external intercostal muscles is to elevate the ribs during forced inspiration. They are responsible for the elevation of the ribs and bending them more open, thus expanding the transverse dimensions of the thoracic cavity.
The internal intercostals form the middle layer of the intercostal musculature. They originate from the costal groove of one rib and insert to the superior border of the immediate rib below. They are located deep to external intercostals from which they are separated by a thin fascia. The internal intercostals are responsible for depressing the ribs during forced expiration, bending them inward and decreasing the transverse dimensions of the thoracic cavity.
The innermost intercostals are the deepest intercostal muscles. They originate from the costal groove of one rib, posteriorly to the origin of the internal intercostals. They course in the same fashion as the internal intercostals and insert to the superior border of the immediate rib below. The innermost intercostals are deep layers of the internal intercostal muscles, separated from them by a neurovascular bundle.
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They support the rib cage and are accessory respiratory muscles
The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups, from superficial to deep: external, internal, and innermost intercostal muscles. All three groups of muscles support the rib cage and are accessory respiratory muscles.
The external intercostal muscles are the most superficial intercostal muscles. They originate from the inferior border of one rib, course inferomedially, and insert into the superior border of the immediate rib below. The function of the external intercostal muscles is to elevate the ribs during forced inspiration.
The internal intercostal muscles form the middle layer of the intercostal musculature. They originate from the costal groove of one rib, course inferolaterally, and insert into the superior border of the immediate rib below. The internal intercostal muscles are responsible for depressing the ribs during forced expiration.
The innermost intercostal muscles are the deepest intercostal muscles. They originate from the costal groove of one rib, posteriorly to the origin of the internal intercostals. They course inferomedially, in the same fashion as the internal intercostals, and insert into the superior border of the immediate rib below. The innermost intercostal muscles assist the internal intercostals in depressing the ribs during forced expiration.
The intercostal muscles work in synchronisation, with the external intercostals expanding the rib cage during inhalation and the internal and innermost intercostals working to shrink the rib cage during exhalation. This mechanical process of altering the size of the rib cage is essential for breathing and facilitates forced breathing during exercise or respiratory dysfunction.
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They are innervated by the anterior rami of spinal nerves T1-T11
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 external intercostals facilitate forced inspiration, while the internal and innermost intercostals aid forced expiration.
The intercostal muscles are innervated by the anterior rami of spinal nerves T1-T11, also known as the intercostal nerves. These nerves arise from the anterior divisions of the thoracic spinal nerves. The intercostal nerves are part of the somatic nervous system, which controls muscle contraction and provides sensory information about the skin and parietal pleura.
The anterior rami of spinal nerves are also called ventral rami. They are responsible for the majority of the body's sensorimotor innervation. After branching from the spinal cord, the thoracic nerve root divides into two nerve bundles: the ventral ramus and the dorsal ramus. The ventral rami provide the spinal contributions to all major neural plexuses.
The first thoracic nerve, T1, is part of the brachial plexus, a complex network of nerves formed by the ventral roots C5-C8 and T1. T1 and T2 feed into nerves that go into the top of the chest, arm, and hand. T3, T4, and T5 feed into the chest wall and aid in breathing, while T6, T7, and T8 can feed into the chest and/or abdomen.
The intercostal nerves run between the ribs and are distributed to the thoracic pleura and abdominal peritoneum. They are involved in the functions of organs and glands in the head, neck, thorax, and abdomen.
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Frequently asked questions
Intercostal muscles are the muscles that link your ribs together and play a crucial role in the respiratory process by assisting with the expansion and contraction of the chest cavity.
There are three groups of intercostal muscles: external, internal, and innermost intercostal muscles.
The function of the external intercostal muscles is to elevate the ribs during forced inspiration or inhalation.
The internal intercostal muscles are responsible for depressing the ribs and bending them inward during forced expiration or exhalation.
The innermost intercostal muscles are deep layers of the internal intercostal muscles, separated from them by a neurovascular bundle. They have similar functions to the internal intercostal muscles, aiding in forced expiration.
