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    Related Topics

    From Musculoskeletal System

    Sutures (in the skull)
    Fibrous joints between skull bones.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Cranial Bones
    Bones of the skull that protect the brain.
    Annular Ligament
    The annular ligament is a strong fibrous band encircling the head of the radius, stabilizing the proximal radioulnar joint and allowing smooth rotation of the forearm.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Facial Bones
    Bones forming the structure of the face.
    Vertebral Column
    Spinal column consisting of vertebrae.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Pivot Joints
    e.g., atlanto-axial joint
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Anterior Cruciate Ligament (ACL)
    Knee ligament that stabilizes the joint.
    Diaphragm
    Primary muscle for breathing.
    Vomer Bone
    Bone forming the nasal septum.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Radius
    Forearm bone on the thumb side.
    Occipital Bone
    Bone forming the back and base of the skull.
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Sternocleidomastoid
    Muscle that rotates and flexes the neck.
    Masseter
    Muscle that elevates the mandible.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.

    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? Sesamoid bones are bones that form within tendons, like the patella.