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    Related Topics

    From Musculoskeletal System

    Occipital Bone
    Bone forming the back and base of the skull.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Patella
    Knee cap, protecting the knee joint.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Ilium
    Uppermost and largest part of the hip bone.
    Skull
    Bony structure of the head that encases the brain.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Sternum
    Breastbone located in the center of the chest.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Vomer Bone
    Bone forming the nasal septum.
    Sacrum
    Triangular bone at the base of the spine.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Masseter
    Muscle that elevates the mandible.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Clavicle
    Collarbone connecting the arm to the body.
    Brachioradialis
    Muscle responsible for forearm flexion.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Facial Bones
    Bones forming the structure of the face.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.

    Diaphragm

    Reviewed by our medical team

    Primary muscle for breathing.

    1. Overview

    The diaphragm is a large, dome-shaped skeletal muscle that plays a primary role in respiration. It separates the thoracic cavity from the abdominal cavity and contracts rhythmically and involuntarily to facilitate breathing. As both a muscular and tendinous structure, it also contributes to functions such as intra-abdominal pressure regulation, posture, and even vocalization. The diaphragm is essential for life and is the principal muscle of ventilation.

    2. Location

    The diaphragm is located at the inferior boundary of the thoracic cavity:

    • Superiorly: In contact with the lungs and heart (covered by pleura and pericardium).

    • Inferiorly: Lies above the liver, stomach, spleen, and kidneys (covered by peritoneum).

    • Laterally: Attaches to the inner surface of the lower six ribs.

    • Posteriorly: Connected to the lumbar vertebrae via crura and arcuate ligaments.

    • Anteriorly: Inserts onto the xiphoid process of the sternum.

    3. Structure

    The diaphragm has a musculotendinous structure consisting of peripheral muscular fibers and a central tendon:

    • Muscular portions: Arise from three origins:

      • Sternal part: From the xiphoid process.

      • Costal part: From the inner surfaces of the lower six ribs and their costal cartilages.

      • Lumbar part: From the right and left crura attaching to the L1–L3 vertebrae and arcuate ligaments.

    • Central tendon: Flat aponeurotic sheet into which all muscular parts converge; lies just below the pericardium.

    • Openings: Three major openings allow passage of structures:

      • Caval opening (T8): For inferior vena cava.

      • Esophageal hiatus (T10): For esophagus and vagus nerves.

      • Aortic hiatus (T12): For descending aorta, thoracic duct, and azygos vein.

    • Innervation: Primarily via the phrenic nerve (C3–C5).

    • Blood supply: Inferior phrenic arteries, internal thoracic arteries, and musculophrenic arteries.

    4. Function

    The diaphragm serves several critical functions:

    • Primary muscle of inspiration: Contracts and flattens during inhalation, increasing thoracic volume and drawing air into the lungs.

    • Assists in expiration: Relaxes during exhalation, allowing passive recoil of the lungs and thoracic wall.

    • Pressure regulation: Increases intra-abdominal pressure to aid in actions such as defecation, urination, and childbirth.

    • Valve function: The crura assist in closing the lower esophageal sphincter, preventing gastric reflux.

    5. Physiological role(s)

    In addition to mechanical ventilation, the diaphragm plays broader physiological roles:

    • Postural stabilization: Works with abdominal and pelvic muscles to support spinal posture, especially during lifting or straining.

    • Lymphatic flow: Facilitates venous and lymphatic return to the heart via changes in thoracoabdominal pressure during respiration.

    • Phonation and vocal control: Regulates airflow from the lungs for speech and singing.

    • Coordination with pelvic floor: Acts synergistically with the pelvic diaphragm during core engagement and pressure regulation.

    6. Clinical Significance

    Dysfunction or pathology of the diaphragm can lead to serious medical conditions:

    • Diaphragmatic paralysis:

      • Due to phrenic nerve injury (e.g., during surgery, trauma, or neurological conditions); results in elevated hemidiaphragm and respiratory compromise.

    • Hiatal hernia:

      • Protrusion of the stomach through the esophageal hiatus; may cause gastroesophageal reflux disease (GERD).

    • Congenital diaphragmatic hernia (CDH):

      • Defective development of the diaphragm allows abdominal contents to enter the thoracic cavity; often life-threatening in neonates.

    • Hiccups (singultus):

      • Involuntary spasms of the diaphragm, often triggered by irritation or distention of the stomach.

    • Respiratory disorders:

      • Chronic obstructive pulmonary disease (COPD) and restrictive lung diseases can alter diaphragmatic function and shape, reducing ventilatory efficiency.

    • Surgical relevance:

      • The diaphragm must be carefully preserved during abdominal or thoracic surgery to maintain respiratory function and prevent complications.

    Did you know? The ischium is the part of the pelvis you sit on.