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The abdominal muscles are the muscles forming the abdominal walls, which encase the abdominal cavity and viscera. They support the trunk, allow movement, hold organs in place, and are distensible. The abdominal wall is formed of skin, fascia, and muscle. There are five main abdominal muscles: pyramidalis, rectus abdominis, external obliques, internal obliques, and transversus abdominis. Below the umbilicus, there are two layers of superficial fascia – Camper’s and Scarpa’s.
| Characteristics | Values |
|---|---|
| Number of abdominal muscles | 5 |
| Location of abdominal muscles | Between the ribcage and pelvis at the front of the body |
| Function | Hold organs in place, support the body during movement, protect the spine, stabilise the trunk, maintain internal abdominal pressure |
| Layers of the abdominal wall | Skin, superficial fascia, muscles and associated fascia, and parietal peritoneum |
| Superficial fascia above the umbilicus | A single sheet of connective tissue |
| Superficial fascia below the umbilicus | Two layers: Camper's fascia (fatty superficial layer) and Scarpa's fascia (membranous deep layer) |
| Blood vessels and nerves | Run between the two layers of superficial fascia below the umbilicus |
| Linea alba | A band of connective tissue that runs from the sternum to the pubic bone, separating the left and right sides of the rectus abdominis |
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What You'll Learn
- The rectus abdominis muscle is bisected by the linea alba
- The abdominal wall is made up of skin, fascia, muscle and the parietal peritoneum
- The linea alba is a band of connective tissue that runs from the sternum to the pubic bone
- The abdominal muscles are divided into two groups: vertical muscles and flat muscles
- The abdominal muscles support the trunk, allow movement, hold organs in place and are distensible
The rectus abdominis muscle is bisected by the linea alba
The rectus abdominis muscle is a long muscle that forms the top layer of the abdominal muscles, commonly referred to as the "six-pack". It is a pair of two flat and parallel muscles that run vertically on the anterior abdominal wall, on either side of the linea alba. The linea alba is a band of connective tissue that divides the rectus abdominis muscle into two halves vertically.
The rectus abdominis muscle is part of the core muscles, which include the transversus abdominis, erector spinae, and obliques. Together, these muscles act like a natural weight belt to protect the lower back from injury. The abdominal muscles work together to control the movement of the spine, pelvis, and rib cage during physical activities such as biking, running, and walking.
The rectus abdominis muscle is a shy muscle that usually hides behind a fatty layer of Camper's fascia and is therefore invisible in most people. It is located below the umbilicus, in the anterolateral abdominal wall, which is a large structure made up of multiple layers of skin, connective tissue, and muscles. The anterolateral abdominal wall can be divided into two main groups: flat muscles and vertical muscles.
The rectus abdominis muscle is enclosed within the rectus sheath, which is a multilayered aponeurosis formed by the aponeuroses of the three flat muscles. The rectus sheath has an anterior and posterior wall for most of its length. The anterior wall is formed by the aponeuroses of the external oblique and half of the internal oblique, while the posterior wall is formed by the aponeuroses of the other half of the internal oblique and the transversus abdominis.
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The abdominal wall is made up of skin, fascia, muscle and the parietal peritoneum
The abdominal wall is a complex structure that encases the abdominal cavity and viscera. It is made up of multiple layers, including skin, fascia, muscle, and the parietal peritoneum.
The outermost layer of the abdominal wall is the skin. Underneath the skin is a layer of superficial fascia, which is a type of connective tissue. The composition of this layer varies depending on its location. Above the umbilicus, it exists as a single sheet of connective tissue, while below the umbilicus, it is divided into two layers: Camper's fascia, a fatty superficial layer, and Scarpa's fascia, a thinner and denser membranous deep layer.
The next layer consists of muscles. The abdominal muscles support the trunk, facilitate movement, and hold organs in place. They can be divided into flat muscles and vertical muscles. The flat muscles include the external abdominal oblique, internal abdominal oblique, and transversus abdominis. These muscles have fibres that run in different directions, strengthening the wall and preventing abdominal contents from herniating through it. The vertical muscles include the rectus abdominis and pyramidalis, which are separated by the linea alba.
Deep to the muscles is the parietal peritoneum, a membrane that lines the abdominal and pelvic walls. It provides insulation and lubrication to the organs, helping to hold them in place and reduce friction. The parietal peritoneum shares the same somatic nerve supply as the abdominal wall it covers.
Additionally, the abdominal wall includes associated fascia, such as the rectus sheath and transversalis fascia, which provide structural support and protection to the underlying organs and muscles. Overall, the layers of the abdominal wall work together to provide stability, balance, and protection to the body's core.
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The linea alba is a band of connective tissue that runs from the sternum to the pubic bone
The linea alba is part of the anterolateral abdominal wall, which consists of four main layers: skin, superficial fascia, muscles and associated fascia, and parietal peritoneum. The superficial fascia layer, which is located just below the skin, consists of connective tissue. Superior to the umbilicus, it is made up of a single layer of connective tissue. However, inferior to the umbilicus, it is divided into two layers: the fatty superficial layer (Camper's fascia) and the membranous deep layer (Scarpa's fascia).
The linea alba is not a tendon, but it does have tendinous structures in the surrounding area with which its fibres blend. It is formed by the union of aponeuroses, which make up the rectus sheath. The rectus sheath encloses the rectus abdominis and pyramidalis muscles. The linea alba is an important anatomical landmark, and a median incision through it is a common surgical approach for abdominal surgery.
The primary function of the linea alba is to keep the right and left abdominal muscles separated. It helps to stabilize and brace the core muscles. However, it can become weak or damaged from overstretching, especially during pregnancy, leading to a condition called diastasis recti, where the abdominal muscles separate. Exercises and physical therapy are typically recommended as treatment for this condition.
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The abdominal muscles are divided into two groups: vertical muscles and flat muscles
The abdominal muscles are a group of strong bands of muscles that line the walls of the abdomen, supporting the trunk, allowing movement, and holding the organs in place. The abdominal wall, which encases the abdominal cavity, can be divided into anterolateral and posterior sections. The abdominal muscles can be further divided into two groups: vertical muscles and flat muscles.
Vertical Muscles
There are two vertical muscles, situated near the midline of the body. These are the rectus abdominis and the pyramidalis. The rectus abdominis is a pair of long, straight muscles that run vertically on either side of the anterior abdominal wall. They are separated by the linea alba, a fibrous line that splits the rectus abdominis into two. The linea alba is a vertical groove extending inferiorly from the xiphoid process. The rectus abdominis muscles help hold the internal organs in place and keep the body stable during movement. The pyramidalis is a small, triangular vertical muscle located at the base of the pubic bone, in front of the rectus abdominis.
Flat Muscles
There are three flat muscles located laterally in the abdominal wall, stacked upon one another. Their fibres run in differing directions and cross each other, strengthening the wall and decreasing the risk of abdominal contents herniating through the wall. The flat muscles are the external oblique, internal oblique, and transversus abdominis. The external obliques are the largest of the flat muscles and sit at the bottom of the stack. They run from the sides of the body toward the middle and allow the trunk to twist from side to side. The internal obliques are much thinner and smaller than the external obliques and are located on top of them. They work together with the external oblique muscles to allow the trunk to twist and turn. The transversus abdominis is the deepest of the flat muscles, layered on top of the internal obliques. It helps to stabilize the trunk and maintain internal abdominal pressure.
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The abdominal muscles support the trunk, allow movement, hold organs in place and are distensible
The abdominal muscles are strong bands of muscles that line the walls of the abdomen, which is the portion of the trunk connecting the thorax and pelvis. They are located between the ribs and the pelvis on the front of the body.
The abdominal muscles have many important functions. Firstly, they support the trunk, allowing movement and flexibility. For example, twisting the trunk to the left requires the left side internal oblique and the right side external oblique to contract together. The abdominal muscles also help with counter-rotation, which occurs between the upper and lower parts of the body, and when the arm and leg are moving in opposite directions.
Secondly, the abdominal muscles hold the internal organs in place, such as the stomach, intestines, pancreas, liver, gallbladder, and other organs. They also protect these organs by regulating internal abdominal pressure.
Lastly, the abdominal muscles are distensible, meaning they can accommodate dynamic changes in the volume of abdominal contents. For example, during inhalation, the abdominal muscles assist the diaphragm and fix the 12th rib. The deep abdominal muscles, together with the intrinsic back muscles, make up the core muscles. They help keep the body stable and balanced and protect the spine.
There are five main abdominal muscles: pyramidalis, rectus abdominis, external obliques, internal obliques, and transversus abdominis.
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Frequently asked questions
The transversus abdominis is the deepest abdominal muscle and is located just under the umbilicus.
The transversus abdominis helps to stabilise the trunk and maintain internal abdominal pressure.
The linea alba is a band of connective tissue that runs from the sternum to the pubic bone. It helps to stabilise and brace the core muscles.
