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    From Musculoskeletal System

    Occipital Bone
    Bone forming the back and base of the skull.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Diaphragm
    Primary muscle for breathing.
    Radius
    Forearm bone on the thumb side.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Mandible
    Lower jawbone that houses the teeth.
    Lacrimal Bones
    Bones forming part of the eye socket and housing the tear ducts.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Hinge Joints
    e.g., elbow, knee
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Deltoid
    Shoulder muscle responsible for arm abduction.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Nasal Bones
    Bones forming the bridge of the nose.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Sternum
    Breastbone located in the center of the chest.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Vomer Bone
    Bone forming the nasal septum.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.

    Levator Ani

    Reviewed by our medical team

    Pelvic floor muscle responsible for lifting the anus.

    1. Overview

    The levator ani is a broad, thin muscle group that forms the majority of the pelvic diaphragm, which supports the pelvic organs and separates the pelvic cavity from the perineum. It plays a vital role in maintaining continence, supporting pelvic viscera, and aiding in childbirth. The levator ani is a key component of the pelvic floor and works in coordination with other pelvic muscles and ligaments.

    2. Location

    The levator ani is located in the pelvic floor, forming a muscular sheet that spans the inner surface of the lesser pelvis:

    • Superiorly: Bounded by the pelvic cavity and pelvic organs (e.g., bladder, rectum, uterus).

    • Inferiorly: Borders the perineal region.

    • Medially: Meets the contralateral muscle at the midline (anococcygeal raphe).

    • Lateral attachments: Extends from the inner surface of the pubic bone and tendinous arch of the obturator fascia to the coccyx and sacrum.

    3. Structure

    The levator ani is not a single muscle but a group of muscles composed of three main parts:

    • Pubococcygeus: Arises from the pubis and inserts on the coccyx and anococcygeal ligament; often subdivided further (e.g., puborectalis, pubovaginalis/puboprostaticus).

    • Puborectalis: Forms a U-shaped sling around the rectum, important for fecal continence.

    • Iliococcygeus: Originates from the ischial spine and tendinous arch; inserts into the coccyx and anococcygeal raphe.

    Additional details:

    • Innervation: Mainly from the nerve to levator ani (S3–S4), with contributions from the pudendal nerve and inferior rectal branches.

    • Blood supply: Inferior gluteal artery, internal pudendal artery, and inferior vesical/vaginal arteries.

    4. Function

    The levator ani performs multiple vital functions:

    • Supports pelvic organs: Acts like a hammock to support the bladder, rectum, uterus, and prostate.

    • Maintains continence: Contracts to maintain urinary and fecal continence, especially during increased intra-abdominal pressure (e.g., coughing or sneezing).

    • Assists childbirth: Helps guide the fetal head during labor and supports the birth canal.

    • Facilitates defecation: The puborectalis part maintains the anorectal angle and relaxes during defecation.

    5. Physiological role(s)

    Beyond its mechanical role, the levator ani contributes to important physiological processes:

    • Pelvic stability: Helps maintain posture and core stability by supporting the pelvic viscera and resisting downward forces.

    • Intra-abdominal pressure regulation: Works with the diaphragm and abdominal muscles during activities such as lifting, straining, or coughing.

    • Sexual function: Supports erectile function and orgasm through pelvic floor contractions in both males and females.

    • Lymphatic and venous return: Assists venous and lymphatic drainage from the pelvic organs through rhythmic contraction and relaxation.

    6. Clinical Significance

    The levator ani is associated with several important clinical conditions:

    • Pelvic organ prolapse:

      • Weakness or tearing of the levator ani (especially during childbirth) can lead to prolapse of the bladder, uterus, or rectum into the vaginal canal.

    • Urinary and fecal incontinence:

      • Dysfunction or denervation of the levator ani can compromise continence mechanisms, especially in aging or post-surgical patients.

    • Levator ani syndrome:

      • Characterized by chronic pelvic pain, pressure, or aching due to muscle spasm or tension, often mistaken for rectal or urogenital disease.

    • Childbirth trauma:

      • During vaginal delivery, overstretching or avulsion of the levator ani from the pubic bone can lead to long-term pelvic floor dysfunction.

    • Pelvic floor rehabilitation:

      • Pelvic floor muscle training, including biofeedback and electrical stimulation, targets the levator ani to improve symptoms of prolapse or incontinence.

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