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    Related Topics

    From Musculoskeletal System

    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Facial Bones
    Bones forming the structure of the face.
    Lacrimal Bones
    Bones forming part of the eye socket and housing the tear ducts.
    Sacrum
    Triangular bone at the base of the spine.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Gliding (Plane) Joints
    e.g., between carpals
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Cranial Bones
    Bones of the skull that protect the brain.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Clavicle
    Collarbone connecting the arm to the body.
    Nasal Bones
    Bones forming the bridge of the nose.
    Hinge Joints
    e.g., elbow, knee
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Occipital Bone
    Bone forming the back and base of the skull.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.

    Obliques (External and Internal)

    Reviewed by our medical team

    Muscles responsible for torso rotation.

    1. Overview

    The external and internal oblique muscles are key components of the abdominal wall and play essential roles in trunk movement, stability, respiration, and protection of internal organs. These paired muscles run diagonally on either side of the torso and work together with other abdominal muscles (transversus abdominis and rectus abdominis) to maintain posture and assist in complex motions involving the spine and pelvis.

    2. Location

    The obliques are located on the anterolateral aspect of the abdominal wall:

    • External oblique: The outermost muscle, located just beneath the skin and subcutaneous tissue.

    • Internal oblique: Lies deep to the external oblique and superficial to the transversus abdominis.

    • Laterally: Extend from the thoracic cage to the pelvis.

    • Medially: Both muscles contribute to the formation of the rectus sheath and linea alba.

    3. Structure

    Both muscles are flat and broad, consisting of fascicles arranged in a diagonal orientation:

    External Oblique

    • Origin: External surfaces of ribs 5–12.

    • Insertion: Linea alba, pubic tubercle, and anterior half of the iliac crest.

    • Fiber direction: Inferomedial (like hands in pockets).

    • Features: Its inferior margin forms the inguinal ligament (Poupart’s ligament).

    Internal Oblique

    • Origin: Thoracolumbar fascia, iliac crest, and lateral half of the inguinal ligament.

    • Insertion: Inferior borders of ribs 10–12, linea alba, and pubis via the conjoint tendon.

    • Fiber direction: Superomedial (perpendicular to external oblique fibers).

    Both muscles are innervated by thoracoabdominal nerves (T7–T11) and the subcostal nerve (T12); the internal oblique also receives innervation from L1 via the iliohypogastric and ilioinguinal nerves.

    4. Function

    Together, the external and internal obliques perform various coordinated functions:

    • Trunk rotation: External oblique on one side and internal oblique on the opposite side contract together to rotate the torso.

    • Lateral flexion: Unilateral contraction of either muscle bends the torso to the same side.

    • Trunk flexion: Bilateral contraction flexes the spine forward.

    • Compress abdominal contents: Aid in increasing intra-abdominal pressure for activities such as defecation, coughing, and childbirth.

    • Stabilize pelvis and spine: Work with other core muscles to maintain posture and protect spinal integrity during movement.

    5. Physiological role(s)

    Beyond movement, the obliques support vital physiological processes:

    • Core stability: Form part of the abdominal cylinder that stabilizes the lumbar spine during lifting or dynamic movement.

    • Respiration: Assist in forced expiration by compressing the abdomen and elevating the diaphragm.

    • Visceral protection: Act as a muscular shield for abdominal organs like the intestines and liver.

    • Venous return support: Help increase intra-abdominal pressure during muscular contraction, aiding venous return from the lower limbs.

    6. Clinical Significance

    The external and internal oblique muscles are involved in several medical and athletic conditions:

    • Muscle strain:

      • Common in athletes, especially those performing sudden twisting movements (e.g., tennis, baseball); may result in localized pain and reduced mobility.

    • Hernia formation:

      • Weakness in the aponeurotic layers formed by the obliques (especially near the inguinal canal) can lead to inguinal hernias.

    • Core dysfunction:

      • Imbalance or weakness in the obliques can lead to poor posture, low back pain, and spinal instability.

    • Post-surgical considerations:

      • Incisions through the obliques (e.g., appendectomy or hernia repair) require careful closure to prevent weakening of the abdominal wall.

    • Functional rehabilitation:

      • Strengthening of obliques is crucial in physical therapy programs for spine health, postural correction, and athletic performance enhancement.

    Did you know? Your bones are constantly adapting to the mechanical forces placed on them.