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The pyramidalis muscle is a small, triangular-shaped muscle that is part of the abdominal wall. It is located between the anterior surface of the rectus abdominis and the posterior surface of the rectus sheath. The function of the pyramidalis muscle is to tense the linea alba, which is an action that doesn't have a significant function on its own but contributes to a variety of abdominal wall functions when working with other muscles. The nerve supply to the pyramidalis muscle is from the ventral part of the T12 spinal segment, and it receives its blood supply from the inferior epigastric artery. The muscle is present in around 80% of the human population and is often unilateral, with considerable variation in size.
| Characteristics | Values |
|---|---|
| Shape | Small and triangular |
| Location | Between the anterior surface of the rectus abdominis and the posterior surface of the rectus sheath |
| Function | Tenses the linea alba |
| Nerve Supply | Ventral part of nerve T12 |
| Arterial Supply | Inferior epigastric artery and deep circumflex iliac artery |
| Variability | Not always present, often unilateral, and vary in size |
| Attachment Sites | Originates from the pubic crest and pubic symphysis, inserts into the linea alba |
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What You'll Learn
The pyramidalis muscle is a small, triangular muscle
The pyramidalis muscle is attached to the pubic symphysis and pubic crest, and it inserts into the linea alba at a point midway between the umbilicus and pubis. The muscle is innervated by the subcostal nerve, which is the anterior ramus of spinal nerve T12. The inferior epigastric artery supplies blood to the pyramidalis muscle.
The function of the pyramidalis muscle is to tense the linea alba. When the pyramidalis contracts, it works together with the other abdominal muscles to increase intra-abdominal pressure. This has been suggested to be important for the erection of the penis or the assumption of an upright posture in humans. Additionally, the contraction of the abdominal muscles can act as a defence mechanism, physically protecting the abdominal organs.
The pyramidalis muscle is not always present in humans, and its absence has been reported in around 20% of cases. It may also be unilateral, with muscles on the two sides being of unequal size. The presence and size of the pyramidalis muscle can vary greatly between individuals.
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It is located in the lower anterior abdominal wall
The pyramidalis muscle is a small, triangular-shaped muscle in the lower anterior abdominal wall. It is located between the anterior surface of the rectus abdominis and the posterior surface of the rectus sheath. The rectus sheath is a multilayered fascial compartment composed of the aponeuroses of the external abdominal oblique, internal abdominal oblique, and transversus abdominis muscles. The pyramidalis muscle is superficial to the inferior part of the rectus abdominis muscle.
The pyramidalis muscle is attached to the bony pelvis at the pubic symphysis and pubic crest. The fibres of the muscle run superiorly and medially to insert into the linea alba, a band of connective tissue that runs down the midline of the abdomen. The point of insertion is midway between the umbilicus and pubis.
The nerve supply to the pyramidalis muscle comes from the ventral part of the T12 spinal segment, also known as the subcostal nerve. The main arterial supply is from the inferior epigastric artery, with a minor contribution from the deep circumflex iliac artery.
The function of the pyramidalis muscle is to tense the linea alba when it contracts. This action contributes to increasing intra-abdominal pressure and has been associated with the erection of the penis or the assumption of an upright posture in humans. The muscle is also used as a surgical landmark in cesarean sections to define the midline of the linea alba.
The pyramidalis muscle is present in around 80% of the human population and may be absent or unilateral in some individuals. It can vary in size and may occasionally be doubled on one side.
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The muscle is innervated by the subcostal nerve
The pyramidalis muscle is a small, triangular muscle located in the anterior abdominal wall. It is found on each side of the linea alba, a tendinous band that runs down the midline of the abdomen. The pyramidalis muscle is positioned between the anterior surface of the rectus abdominis muscle and the posterior surface of the rectus sheath, a multilayered fascial compartment.
The primary function of the pyramidalis muscle is to tense the linea alba. When the pyramidalis muscle contracts, it works together with other abdominal muscles to increase intra-abdominal pressure. This contraction of the abdominal muscles serves as a defence mechanism, physically protecting the abdominal organs.
The pyramidalis muscle is innervated by the subcostal nerve, which is also known as the ventral portion of spinal nerve T12. Innervation refers to the supply of nerves to a particular muscle or body part. The subcostal nerve is responsible for carrying motor and sensory signals to and from the pyramidalis muscle, enabling its contraction and contributing to its role in abdominal wall functions.
The nerve supply to the pyramidalis muscle can vary, and it may receive innervation from different nerve sources in some individuals. This variation in nerve supply highlights the complex nature of human anatomy and the potential differences that can exist between individuals.
The pyramidalis muscle is present in approximately 80% of the human population. However, it may be absent in some individuals or present unilaterally, with a larger size on one side compared to the other. The muscle's presence and size can vary, showcasing the diverse nature of human anatomy and the importance of understanding anatomical variations in medical contexts.
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It is present in 80% of the human population
The pyramidalis muscle is a small, triangular-shaped muscle found in the abdomen. It is part of the anterior abdominal wall and lies within the rectus sheath, a multilayered fascial compartment. The muscle is innervated by the subcostal nerve, or the ventral portion of spinal nerve T12. The inferior and superior epigastric arteries supply blood to the pyramidalis muscle.
The function of the pyramidalis muscle is to tense the linea alba, which is an action that doesn't have a significant function on its own. However, when the pyramidalis muscle contracts together with the other abdominal muscles, it contributes to various abdominal wall functions, such as increasing intra-abdominal pressure.
The pyramidalis muscle is present in 80% of the human population. However, its presence can vary, with some studies reporting a higher presence of 92%. It may be absent in around 20% of cases, usually unilaterally, but can also be absent on both sides. The muscle is also known to vary in size, with some individuals having larger or more developed pyramidalis muscles than others. The frequency of the pyramidalis muscle in humans may be influenced by racial and ethnic characteristics, with varying incidences of unilateral and bilateral presence reported across different populations.
The pyramidalis muscle is considered a vestigial muscle, which means it is tendinous in larger part or reduced in size compared to homologous muscles in other species. Phylogenetically, the pyramidalis muscle is linked to the pouch inside monotremes, such as hedgehogs and platypuses, and marsupials, such as koalas and kangaroos.
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The function of the muscle is to tense the linea alba
The pyramidalis muscle is a small, triangular-shaped muscle that is part of the anterior abdominal wall. It is found on each side of the linea alba, a tendinous structure that runs down the midline of the abdomen. The linea alba is formed by the fusion of the aponeuroses of the right and left rectus abdominis muscles. The pyramidalis muscle originates from the bony pelvis, attaching to the pubic symphysis and pubic crest. From here, the fibres of the muscle run superiorly and medially, narrowing as they ascend, and insert into the linea alba midway between the umbilicus and pubis.
The function of the pyramidalis muscle is to tense the linea alba. When the pyramidalis muscle contracts, it works together with the other abdominal muscles to increase intra-abdominal pressure. This pressure increase helps to protect the abdominal organs by physically contracting the abdominal wall. Additionally, it supports certain physiological processes such as forced respiration, singing, micturition, and defecation.
The pyramidalis muscle is not always present in individuals, and its absence does not seem to affect abdominal function significantly. It is estimated to be absent in about 20% of cases, and even when present, it may vary in size and be unilateral. The nerve supply to the pyramidalis muscle is from the ventral part of nerve T12, and it receives its blood supply from the inferior epigastric artery and, to a lesser extent, the deep circumflex iliac artery.
The pyramidalis muscle also has clinical importance. Due to its location, it is used as a surgical landmark during a caesarean section to define the midline of the linea alba. Additionally, after long-term cryopreservation, the pyramidalis muscle can be used as a source of striated muscle stem cells for various treatments.
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Frequently asked questions
The pyramidalis muscle is a small triangular muscle of the anterior abdominal wall. It is located between the anterior surface of the rectus abdominis and the posterior surface of the rectus sheath.
The function of the pyramidalis muscle is to tense the linea alba. It does this by contracting with other abdominal muscles to increase positive abdominal pressure.
The nerve supply to the pyramidalis muscle is from the ventral part of nerve T12, also known as the subcostal nerve.
The blood supply to the pyramidalis muscle comes from the inferior epigastric artery and, to a lesser extent, the deep circumflex iliac artery.
