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    Related Topics

    From Musculoskeletal System

    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.
    Adductors
    Muscles that bring the thighs toward the midline.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Nasal Bones
    Bones forming the bridge of the nose.
    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.
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Sacrum
    Triangular bone at the base of the spine.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Triceps Brachii
    Muscle responsible for elbow extension.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Tibialis Anterior
    Muscle that dorsiflexes and inverts the foot.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Pivot Joints
    e.g., atlanto-axial joint
    Femur
    Thigh bone, the longest and strongest bone in the body.
    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.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Acromioclavicular Ligament
    Ligament that connects the acromion to the clavicle.
    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Vertebral Column
    Spinal column consisting of vertebrae.

    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? Bones in the feet form arches that provide balance and flexibility.