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    Related Topics

    From Musculoskeletal System

    Hinge Joints
    e.g., elbow, knee
    Interspinous Ligament
    Spinal ligament between adjacent vertebral spinous processes.
    Phalanges (14 bones)
    14 bones forming the toes.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Patellar Tendon
    Tendon connecting the patella to the tibia.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Acetabulum
    The acetabulum is the pelvic socket that connects with the femoral head to form the hip joint, vital for stability, movement, and weight-bearing.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Triceps Brachii
    Muscle responsible for elbow extension.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Wormian Bones
    Sutural bones in the skull.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Diaphragm
    Primary muscle for breathing.
    Pivot Joints
    e.g., atlanto-axial joint
    Acromioclavicular Ligament
    Ligament that connects the acromion to the clavicle.
    Trapezius
    Muscle responsible for moving, rotating, and stabilizing the scapula.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Carpals (8 bones)
    8 wrist bones.
    Vomer Bone
    Bone forming the nasal septum.
    Symphyses
    Cartilaginous joints where bones are connected by fibrocartilage.
    Sternocleidomastoid
    Muscle that rotates and flexes the neck.

    Rectus Abdominis

    Reviewed by our medical team

    Abs muscle that flexes the trunk.

    1. Overview

    The rectus abdominis is a long, flat, paired muscle that runs vertically along the anterior abdominal wall. Commonly referred to as the “six-pack” muscle due to its segmented appearance, it plays a major role in flexing the trunk, stabilizing the pelvis, and increasing intra-abdominal pressure. It is a key muscle in core strength and postural stability.

    2. Location

    The rectus abdominis is located in the midline of the anterior abdominal wall:

    • Extends from: The pubic symphysis and pubic crest (inferiorly) to the xiphoid process and costal cartilages of ribs 5–7 (superiorly).

    • Medially: Meets its contralateral counterpart at the linea alba.

    • Enclosed within: The rectus sheath, formed by the aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles.

    3. Structure

    The rectus abdominis is a strap-like, segmented muscle divided horizontally by fibrous bands called tendinous intersections:

    • Shape: Long, vertical, and narrow, running parallel to the midline.

    • Tendinous intersections: Transverse fibrous bands that give rise to the “six-pack” appearance; typically three per side.

    • Linea alba: A fibrous midline seam that separates the left and right rectus muscles.

    • Innervation: Supplied by lower thoracoabdominal nerves (T7–T12).

    • Blood supply: Primarily from the superior and inferior epigastric arteries.

    4. Function

    The rectus abdominis performs several key musculoskeletal functions:

    • Trunk flexion: Flexes the vertebral column, particularly during activities like sit-ups or bending forward.

    • Posterior pelvic tilt: Stabilizes the pelvis by preventing anterior tilt, especially during leg raises.

    • Assists in forced expiration: Helps in expelling air by depressing the ribs and compressing the abdomen.

    • Contributes to abdominal compression: Works with other abdominal muscles to compress the abdominal cavity during defecation, childbirth, and lifting.

    5. Physiological role(s)

    Beyond mechanical movement, the rectus abdominis supports important physiological processes:

    • Core stability: Provides stability to the trunk, supporting the spine and preventing injury during dynamic movement.

    • Intra-abdominal pressure regulation: Works with the diaphragm and pelvic floor to maintain pressure needed for urination, defecation, and parturition.

    • Breathing support: Acts as an accessory muscle of respiration during forceful exhalation (e.g., coughing, blowing).

    • Spinal health: Protects the lumbar spine by resisting excessive extension and rotation.

    6. Clinical Significance

    The rectus abdominis is clinically significant in several conditions:

    • Muscle strain:

      • Common in athletes, especially during activities involving sudden trunk flexion or rotation.

    • Diastasis recti:

      • Separation of the rectus abdominis along the linea alba, often seen postpartum or in individuals with significant abdominal distension.

    • Hernias:

      • Weakness in the anterior abdominal wall near the rectus sheath may lead to epigastric or umbilical hernias.

    • Surgical relevance:

      • The rectus sheath is often incised in abdominal surgeries; care must be taken to avoid damaging underlying structures.

    • Cosmetic and functional rehabilitation:

      • Targeted in physical therapy and fitness programs for strengthening, posture correction, and aesthetic training (e.g., six-pack formation).

    Did you know? The average adult human has 206 bones, but this number can vary slightly due to additional bones in the hands or feet.