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    Related Topics

    From Musculoskeletal System

    Glenohumeral Ligaments
    Shoulder ligaments that stabilize the shoulder joint.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Ischium
    Part of the pelvis that supports weight while sitting.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    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.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    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.
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Phalanges (14 bones)
    14 bones forming the toes.
    Adductors
    Muscles that bring the thighs toward the midline.
    Quadriceps
    Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Anterior Scalene Muscle
    The anterior scalene muscle is a deep neck muscle that elevates the first rib during inspiration and aids in neck flexion and stability, located between key neurovascular structures.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Tarsals (7 bones)
    7 ankle bones.
    Ethmoid Bone
    Bone forming part of the nasal cavity and the orbit.
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Rotator Cuff Tendons
    Tendons of the rotator cuff muscles.
    Lateral Collateral Ligament (LCL)
    Knee ligament that stabilizes the outer knee.
    Patella
    Knee cap, protecting the knee joint.
    Vomer Bone
    Bone forming the nasal septum.

    Sternum

    Reviewed by our medical team

    Breastbone located in the center of the chest.

    1. Overview

    The sternum, or breastbone, is a flat, elongated bone located in the center of the anterior thoracic wall. It forms the anterior portion of the rib cage and provides protection to vital thoracic organs, including the heart and major blood vessels. The sternum also serves as an essential anchor point for ribs and clavicles.

    2. Location

    The sternum is situated in the midline of the anterior thorax:

    • Anterior to: The heart, great vessels, and upper mediastinum.

    • Medial to: The ribs and costal cartilages.

    • Superiorly: Articulates with the clavicles and the first pair of ribs.

    • Inferiorly: Ends just above the xiphoid process and costal arch.

    3. Structure

    The sternum is a flat bone composed of three parts:

    • Manubrium:

      • Uppermost, triangular portion.

      • Articulates with the clavicles (at the sternoclavicular joints) and first two pairs of ribs.

      • Features include the jugular (suprasternal) notch and clavicular notches.

    • Body (gladiolus):

      • Longest central portion of the sternum.

      • Articulates with costal cartilages of ribs 2 to 7.

      • Connected to the manubrium at the sternal angle (Angle of Louis), a key clinical landmark.

    • Xiphoid process:

      • Small, cartilaginous projection at birth that ossifies with age.

      • May vary in shape and size; serves as an attachment for muscles like the diaphragm and rectus abdominis.

    The sternum has an internal spongy bone structure with a thin layer of compact bone externally and is rich in red bone marrow.

    4. Function

    The sternum performs several structural and protective roles:

    • Protects thoracic organs: Shields the heart, great vessels, and part of the lungs from trauma.

    • Attachment point: Provides anchorage for ribs (via costal cartilages) and clavicles, maintaining the structural integrity of the thoracic cage.

    • Supports respiration: Moves slightly during breathing, facilitating thoracic expansion and contraction.

    • Muscle origin: Serves as an attachment site for the pectoralis major, sternocleidomastoid, sternohyoid, and other muscles.

    5. Physiological role(s)

    Though primarily structural, the sternum contributes to physiological processes:

    • Hematopoiesis: Contains red bone marrow, especially in the manubrium and body, active in producing blood cells.

    • Landmark for procedures: Used for sternal puncture or bone marrow biopsy in adults.

    • Postural alignment: Acts as a central anchor for rib movements and spinal posture in the thoracic region.

    6. Clinical Significance

    The sternum plays a role in various clinical and surgical contexts:

    • Sternal fractures:

      • Often due to blunt trauma (e.g., motor vehicle collisions); can injure underlying heart or great vessels.

    • Sternal angle (Angle of Louis):

      • Important landmark for rib counting and auscultation; marks the level of the 2nd rib and bifurcation of the trachea.

    • Sternal puncture:

      • Used to access bone marrow in diagnostics for leukemia, lymphoma, or anemia.

    • Mediastinal surgery:

      • The sternum is often divided (median sternotomy) to access the heart and lungs in procedures like open-heart surgery.

    • Xiphoid process issues:

      • Can cause xiphodynia—pain or discomfort from inflammation or trauma.

    • Congenital anomalies:

      • Includes cleft sternum or pectus carinatum/excavatum, which may require surgical correction for functional or cosmetic reasons.

    Did you know? The tibia is the second largest bone in the body after the femur.