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Deciphering Models
Muscle models are designed so that the right side of the model will have all muscles in place. You can only see what is superficialNear the surface of the body.. On the left side of most models, certain elements are intentionally altered. I mean the model’s left side, not your left side. Some aponeuroses and even some superficial muscles are removed. This is the case with the abdominal muscles.
The abdominal muscles can be ordered from deepAway from the surface of the body. to superficial: transverse abdominisCompressor Deepest abdominal layer; squeezes abdominal contents and stabilizes core., internal obliqueFlexor / Rotator Under external oblique; helps twist and compress abdomen., rectus abdominis, external obliqueFlexor Runs vertically along belly; flexes spine, the ‘six-pack’ muscle.. Think of them like aprons that you are putting on. The transverse abdominis is the apron with fibers running right to left across your squishy guts. This is also the muscle that, when cut in a C-section, refuses to go back to its prior state. There are three more aprons over the transverse abdominis. They include the internal oblique, the rectus abdominis, and the external oblique. This is their order from deep to superficial.
The muscles on the left side of a muscle model are removed. However, the transverse abdominis is still not visible without removing the front plate of the model. This is what you see in the picture below. That is the inside of the ribsCurved bones forming the rib cage; articulate with thoracic vertebrae and most with the sternum. and abdomen. This is usually the only way you can see the transverse abdominis in a muscle model.
Rectus Abdominis
The rectus abdominis is a prominent paired muscle. It is located in the anteriorThe front of the body or toward the front when standing in the anatomical position. abdominal wall. This muscle forms the “six-pack” appearance in well-defined individuals.
Origin
The rectus abdominis originates from the pubic symphysisCartilaginous joint connecting the two pubic bones at the midline. and the pubic crestRidge on superior surface of pubic body; attachment for abdominal muscles..
Insertion
The rectus abdominis extends upwards along the midline of the abdomen. It inserts into the xiphoid processSmall, cartilaginous tip at the inferior end of the sternum; often pointed. of the sternumFlat bone forming the center of the chest; anchor for ribs and clavicles. Appears as a vertical dagg and into the costal cartilages of the fifth, sixth, and seventh ribs.
Actions
- Posture and Movement
Trunk Flexion
External Oblique
The external abdominal obliques require you to do those sideways-turning sit-ups.
Origin
The rectus abdominis originates from the pubic symphysis and the pubic crest.
Insertion
The rectus abdominis extends upwards along the midline of the abdomen. It inserts into the xiphoid process of the sternum and into the costal cartilages of the fifth, sixth, and seventh ribs.
Actions
- Posture and Movement
- Trunk Flexion
Photography, text, and labels by Rob Swatski, Assistant Professor of Biology, Harrisburg Area Community College – York Campus, York, PA.
Internal Oblique
The internal abdominal obliques are sandwiched between the transverse abdominis and the rectus abdominis. They are just as difficult to work out as the external obliques.
Origin
The internal abdominal obliques originate from several points: the inguinal ligament, iliac crestSuperior ridge of the ilium; easily felt along the waistline., and thoracolumbar fascia. They also have attachments to the lower three or four ribs.
Insertion
Fibers converge and attach to the linea alba. They also attach to the pubic crest, the xiphoid process of the sternum, and the cartilages of the lower three or four ribs.
Actions
- Posture and Movement
- Lateral Flexion
- Trunk Rotation and Flexion
Photography, text, and labels by Rob Swatski, Assistant Professor of Biology, Harrisburg Area Community College – York Campus, York, PA.
Transverse Abdominis
The transversus abdominis is a crucial muscle of the human abdomen. It plays a significant role in core stability and overall posture.
Origin
The transversus abdominis muscle originates from the lower six costal cartilages, the anterior two-thirds of the iliac crest, and the lateralAway from the midline of the body. third of the inguinal ligament. Its origin is on the inner surface of the lower ribs, the lumbar vertebraeLargest and thickest vertebrae; short, blunt spinous processes for weight-bearing stability., and the pelvis.
Insertion
The muscle inserts into the linea alba, the pubic crest, and the pecten pubisAnterior portion of the hip bone; meets its pair at the pubic symphysis..
Actions
- Posture and Movement
- Pelvic Stability
- Spinal Support
Identify More Muscles
Link to more Muscle Identification
Upper Arm Muscles
Forearm Muscles
Calf Muscles
Anterior Thigh Muscles
Posterior Thigh Muscles
Knee Structures
Chest Muscles
Back Muscles
Abdominal Muscles
Neck Muscles
Head Muscles
List of terms
- superficial
- deep
- transverse abdominis
- internal oblique
- external oblique
- ribs
- anterior
- pubic symphysis
- pubic crest
- xiphoid process
- sternum
- iliac crest
- anatomy
- lateral
- lumbar vertebrae
- pubis