The primary muscles involved in causing hiccups are the inspiratory muscles of the chest and abdomen, most notably the diaphragm.
How Hiccups Happen: A Muscular Perspective
Hiccups are essentially a reflex action. Here’s a breakdown of how the muscles contribute:
- Diaphragm Contraction: The process starts with a sudden, involuntary contraction of the diaphragm, which is a large, dome-shaped muscle located beneath the lungs, separating the chest from the abdomen. The reference states that hiccups are a result of "a sudden spasmodic contraction of the diaphragm".
- Inspiratory Muscle Involvement: This contraction is not limited to just the diaphragm. It extends to other inspiratory muscles located in the chest and abdomen, enhancing the rapid inhalation phase of the hiccup. The provided reference clearly indicates that the hiccup involves "shaking of the inspiratory muscles of the chest and abdomen".
- Glottis Closure: The sharp inhalation caused by the muscles is immediately followed by a swift closure of the glottis, which is the opening between the vocal cords. This closure is what causes the characteristic "hic" sound because it generates a noise due to the air being expelled violently.
Muscles Involved in Detail
Here's a more detailed list of muscles that play a role in the hiccup process:
- Primary Muscle:
- Diaphragm: As mentioned, the primary trigger of a hiccup is a spasm in the diaphragm.
- Secondary Muscles:
- Intercostal Muscles: These are the muscles between the ribs, which help in breathing. They contract during the quick inspiration phase.
- Abdominal Muscles: These muscles can be recruited during the forced inspiration, further influencing the abdominal cavity and diaphragm.
Why Does This Happen?
While we know which muscles are involved, the exact reason why these muscle spasms happen is complex and not fully understood. It's thought to be related to a disturbance in the neural pathway that controls these muscles.
Conclusion
In summary, hiccups are caused by the sudden contraction of the diaphragm, along with the involvement of other inspiratory muscles of the chest and abdomen, followed by the closure of the glottis. The rapid contraction of these specific muscle groups generates the unique characteristic hiccup sound.
