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Structure
Intermediate
9 min read

Abdominal wall

The abdominal wall brings together four stacked muscles whose fibres cross. It flexes and rotates the trunk, but its most constant role is to resist movement and to manage internal pressure.
3D scene
The layers of the abdominal wall
The body map strips the layers away one by one, from the rectus abdominis and the external oblique down to the transversus. The crossing directions of the fibres then become visible. Without the 3D, remember this: four stacked layers, whose fibres run in four different directions, meet along a fibrous midline band.
Open in the explorer

Where the abdominal wall is located

The abdominal wall closes the space between the ribs and the pelvis, where the spine is the only bony structure. It is made of four paired muscles arranged in layers, whose fibres run in different directions. This crossing gives the wall resistance in several planes at once, like the successive plies of a reinforced fabric.

The rectus abdominis

It arises from the pubis and runs vertically up to the xiphoid process of the sternum and to the cartilages of the fifth, sixth and seventh ribs. It is crossed by transverse tendinous intersections, which draw the relief visible on an abdomen with little fat over it.

The obliques

  • The external oblique, the most superficial, arises from the outer surface of the lower ribs; its fibres run downward and inward, toward the iliac crest and the linea alba.
  • The internal oblique, lying beneath it, arises from the thoracolumbar fascia, the iliac crest and the inguinal ligament; its fibres run upward toward the last ribs and the linea alba, almost perpendicular to those of the external oblique.

The transversus abdominis

This is the deepest layer. Its fibres are horizontal and run from the lower costal cartilages, the thoracolumbar fascia, the iliac crest and the inguinal ligament to the linea alba, the fibrous midline band where all the aponeuroses meet.

Innervation and palpable landmarks

Innervation comes from the thoracoabdominal nerves, from roots T7 to T12, supplemented lower down by lumbar branches. The landmarks are the iliac crest, the costal margin and the linea alba, the vertical midline groove felt when the abdomen is lightly contracted.

What the abdominal wall does

  • Trunk flexion: the rectus abdominis brings the sternum toward the pubis.
  • Rotation: the obliques work diagonally, the external oblique on one side acting with the internal oblique on the opposite side.
  • Side bending: the obliques and the rectus abdominis on the same side tilt the trunk.
  • Management of abdominal pressure: the transversus and the obliques tighten the wall and raise internal pressure, which stiffens the whole trunk.
  • Resistance to movement: in most loaded situations, these muscles keep the trunk from extending, tilting or turning rather than producing a movement.
Intra-abdominal pressure
Pressure exerted inside the abdominal cavity by the combined contraction of the [diaphragm](/en/body/muscles/diaphragm), the abdominal wall and the pelvic floor. It increases the stiffness of the trunk during an effort.
abdominal pressure
Certainty level · Probable
A stiffened trunk transmits forces better between the lower and the upper limbs.
This principle rests on laboratory measurements showing that co-contraction of the trunk muscles increases its stiffness. Moving from that observation to a choice of exercises remains debated: the protocols studied differ, the populations are varied, and the results on performance or on prevention are not consistent. It is therefore a general orientation, not a rule that applies to every person.
McGill SM (2010)

Seeing the abdominal wall in motion

The layers of the abdominal wall

The body map strips the layers away one by one, from the rectus abdominis and the external oblique down to the transversus. The crossing directions of the fibres then become visible. Without the 3D, remember this: four stacked layers, whose fibres run in four different directions, meet along a fibrous midline band.
Current step
Anterior view
The front of the body. Pectoralis major covers the upper chest, the deltoid caps the shoulder, the biceps fills the front of the arm, the abdominal wall links the ribs to the pelvis, and the quadriceps fills the front of the thigh. Further out on the limbs, the forearm muscles drive the wrist and hand, and tibialis anterior lifts the foot.
Scene description
A three-dimensional diagram of a standing human body, arms by the sides, built from simplified paper-coloured volumes. Twelve priority muscle groups are laid over this outline in terracotta: at the front, pectoralis major, the deltoid, biceps brachii, the abdominal wall and the quadriceps; at the back, the trapezius, latissimus dorsi, the erector spinae, triceps brachii, the glutes, the hamstrings and the calves. A simplified skeleton — skull, spine, ribcage, pelvis, humerus, femur and tibia — can be shown beneath the outline to reveal the bony levers these muscles pull on. Each group is selectable and opens its own reference page. This is a teaching diagram with stylised volumes, not an exact anatomical reconstruction.
Visible structures
  • Pectoralis major
    A thick sheet running from the clavicle, the sternum and the upper costal cartilages to the lateral lip of the bicipital groove of the humerus. It draws the arm towards the midline and forwards, and drives horizontal pushing.
  • Deltoids
    Three heads — anterior, lateral and posterior — running from the clavicle, the acromion and the spine of the scapula to the deltoid tuberosity of the humerus. Together they raise the arm; separately they carry it forwards, out to the side or backwards.
  • Biceps brachii
    Two heads arising from the scapula — the supraglenoid tubercle and the coracoid process — joining on the radial tuberosity. It flexes the elbow and supinates the forearm, and contributes to every pulling movement.
  • Abdominal wall
    Rectus abdominis, the external and internal obliques and transversus, running from the ribs and sternum to the pubis and iliac crest. They flex and rotate the trunk and, above all, stabilise the spine by regulating intra-abdominal pressure.
  • Quadriceps
    Four heads — rectus femoris, vastus lateralis, vastus medialis and vastus intermedius — joining through the quadriceps tendon onto the patella and then the tibial tuberosity. They extend the knee, and rectus femoris also flexes the hip.
  • Trapezius
    A diamond-shaped muscle spanning from the occiput and the cervical and thoracic spinous processes to the clavicle, the acromion and the spine of the scapula. Its upper, middle and lower portions elevate, retract and depress the scapula.
  • Latissimus dorsi
    A broad fan arising from the lower thoracic vertebrae, the thoracolumbar fascia, the iliac crest and the lowest ribs, converging on the bicipital groove of the humerus. It pulls the arm down and back, and drives vertical pulling.
  • Erector spinae
    Muscular columns — iliocostalis, longissimus and spinalis — running from the sacrum and iliac crest to the ribs, the vertebrae and the skull, on either side of the spinous processes. They extend the spine and control the trunk as it lowers.
  • Triceps brachii
    Three heads — long, lateral and medial — arising from the scapula and the back of the humerus and joining on the olecranon of the ulna. It extends the elbow, and its long head also assists shoulder extension.
  • Glutes
    Gluteus maximus, medius and minimus, arising from the iliac wing and the sacrum and inserting on the femur and the iliotibial tract. They extend, abduct and rotate the hip, and drive the pelvis upright in the hinge and the squat.
  • Hamstrings
    Biceps femoris, semitendinosus and semimembranosus, running from the ischial tuberosity to the tibia and fibula. They extend the hip and flex the knee, and control the trunk as it lowers in the hip hinge.
  • Calves
    The gastrocnemius and soleus, joining through the Achilles tendon onto the calcaneus. They plantarflex the ankle, and the gastrocnemius, which crosses the knee, also assists knee flexion.
  • Rotator cuff
    Four short muscles running from the shoulder blade to the top of the humerus. Their tendons merge into a sheet that holds the head of the bone against its socket while the deltoid moves the arm.
  • Serratus anterior
    A sheet hooked onto the upper ribs by triangular slips, passing under the shoulder blade and attaching to its inner border. It holds the blade against the ribcage and rotates it.
  • Iliopsoas
    The only muscle linking the lumbar spine directly to the femur. It descends from the vertebrae and the iliac fossa, curves around the rim of the pelvis and attaches to the lesser trochanter.
  • Hip adductors
    Five muscles running from the pubis to the back of the femur in overlapping layers. They draw the thigh towards the midline and control the pelvis in single-leg stance.
  • Forearm muscles
    Masses gathered near the elbow, continued by long tendons to the wrist and fingers. They drive the hand from a distance and carry grip strength.
  • Tibialis anterior
    A muscle pressed against the outer surface of the tibia, its tendon swinging towards the inside of the foot. It lifts the toes on every step and brakes the forefoot after heel strike.
  • Diaphragm
    A muscular dome running from the lower border of the ribs, the sternum and the lumbar vertebrae to a central tendon. As it contracts it descends, the chest gains volume and air enters: it is the engine of quiet breathing, and the ceiling of the abdominal cavity.
Guided steps
  • 1/5
    The front of the body. Pectoralis major covers the upper chest, the deltoid caps the shoulder, the biceps fills the front of the arm, the abdominal wall links the ribs to the pelvis, and the quadriceps fills the front of the thigh. Further out on the limbs, the forearm muscles drive the wrist and hand, and tibialis anterior lifts the foot.
  • 2/5
    The back of the body. The trapezius links the neck to the shoulder blades, the latissimus dorsi fans down to the pelvis, the erector spinae flank the spine, and the triceps fills the back of the arm. Glutes, hamstrings and calves form the posterior chain from hip to ankle.
  • 3/5
    Beneath the visible groups work muscles no silhouette shows. The rotator cuff holds the head of the humerus against the shoulder blade, serratus anterior keeps the shoulder blade flat on the ribcage, the iliopsoas links the lumbar spine to the femur, and the adductors fill the inner thigh. Deeper still, the diaphragm closes the trunk as a dome, inside the ribs. They orient and stabilise more than they move.
  • 4/5
    In a push, force starts at the ground, travels through the quadriceps and the abdominal wall, and then pectoralis major, the anterior deltoid and the triceps drive the load away from the trunk. The skeleton acts as the lever: no group works alone, and the quality of the movement comes from their sequencing.
  • 5/5
    In a pull, the latissimus dorsi and trapezius bring the arm and shoulder blade towards the trunk while the biceps flexes the elbow. Glutes, hamstrings and erector spinae hold the pelvis and spine so that force transfers without the trunk collapsing.
Model licence · Z-Anatomy et BodyParts3D — CC-BY-SA 4.0

The movements it takes part in

The abdominal wall is involved in almost every loaded movement. In the squat, it holds the position of the trunk while the quadriceps and the glutes produce the movement. In the hip hinge, it resists excessive extension of the lumbar spine at the end of the movement.
It also works during the vertical push: as the load passes above the head, the abdominal wall limits the backward tilt of the rib cage.

Synergists

  • The diaphragm and the pelvic floor muscles close the abdominal cavity above and below, a necessary condition for pressure to build.
  • The quadratus lumborum assists side bending.
  • The latissimus dorsi receives fibres from the external oblique and shares the thoracolumbar fascia.

Antagonists

  • The erector spinae extend the spine, the opposite action to trunk flexion.
  • The psoas helps tilt the pelvis forward, the opposite of the tilt produced by the rectus abdominis.

What the 3D model simplifies

Limit
Four layers, a single wall
The model displays the four muscles separately to make the orientation of their fibres visible. In the body, their aponeuroses merge along the midline and form a continuous sheath around the rectus abdominis: the wall behaves as one unit, not as four independent muscles.
The scene shows here neither the pelvic floor nor the viscera, even though they take part in the mechanical behaviour of the abdomen. The diaphragm has since joined the body map, in the deep muscle layer. The number of tendinous intersections and the width of the linea alba vary from person to person: the visible relief is therefore not an indicator of function.

Sources

Key sources

  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
  • McGill SM (2010). Core training: evidence translating to better performance and injury prevention. Strength and Conditioning Journal.
Put it into practice in Shapier

Train anti-extension with the dead bug

Setting up the dead bug and tracking your practice happens in Shapier; Body Lab only explains why the abdominal wall resists movement under load.
Train anti-extension with the dead bug
Body Lab explains; Shapier lets you act and track.

Check my understanding

In the squat, what is the main role of the abdominal wall?
Is a sharply drawn abdominal relief the sign of a more functional abdominal wall?
What should be remembered about the link between a stiffened trunk and force transmission?
Choose an answer

Read next

  • Erector spinae
    The erector spinae form three muscular columns running along the spine. They straighten it, control its forward bending and hold the trunk during hip hinge movements.
    With a 3D scene
  • Glutes
    The three gluteal muscles cover the back and the side of the pelvis. The gluteus maximus extends the hip, while the gluteus medius and minimus steady the pelvis as soon as the body is supported on one leg.
    With a 3D scene
  • Latissimus dorsi
    The latissimus dorsi is the broadest muscle of the back. It links the pelvis and the spine to the humerus, and draws the arm down and backward in every pulling movement.
    With a 3D scene

Where to go next

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Trust and method

Author
equipe-editoriale-shapier
Editorial review
Thanh Chau
Scientific review
Pending
Published on
August 2, 2026
Reviewed on August 2, 2026
Next review due August 2, 2027
Limits of this page
  • The four muscle layers are displayed separately, whereas they merge into shared aponeuroses along the midline.
  • The pelvic floor takes part in managing abdominal pressure and is shown in no scene; the diaphragm now is, but in the deep layer rather than here.
  • The number and the position of the tendinous intersections of the rectus abdominis vary markedly from person to person.
Sources
  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
  • McGill SM (2010). Core training: evidence translating to better performance and injury prevention. Strength and Conditioning Journal.
Educational content. Body Lab does not diagnose and does not replace professional advice.
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