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    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
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    Vertebrae in the upper and mid-back (T1-T12).
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    Bones of the skull that protect the brain.
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    Part of the pelvis that supports weight while sitting.
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    12 pairs of bones that form the sides of the thoracic cage.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Gliding (Plane) Joints
    e.g., between carpals
    Vomer Bone
    Bone forming the nasal septum.
    Mandible
    Lower jawbone that houses the teeth.
    Nasal Bones
    Bones forming the bridge of the nose.
    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.
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    Bone forming part of the nasal cavity and the orbit.
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    Shoulder ligaments that stabilize the shoulder joint.
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    Shoulder muscle responsible for arm abduction.
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    e.g., thumb joint
    Trapezius
    Muscle responsible for moving, rotating, and stabilizing the scapula.
    Pivot Joints
    e.g., atlanto-axial joint
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Sesamoid Bones
    e.g., patella, some found in hands/feet.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Sutures (in the skull)
    Fibrous joints between skull bones.

    Zygomaticus

    Reviewed by our medical team

    Muscle that raises the corners of the mouth.

    1. Overview

    The zygomaticus muscles are a pair of facial expression muscles that play a major role in elevating the corners of the mouth, particularly during smiling. There are two main components: the zygomaticus major and zygomaticus minor. These muscles belong to the group of mimetic muscles and are essential for social and emotional expression.

    2. Location

    The zygomaticus muscles are located in the midface region, extending obliquely from the zygomatic bone toward the mouth:

    • Zygomaticus major: Originates from the lateral aspect of the zygomatic bone and inserts into the skin at the corner of the mouth (modiolus).

    • Zygomaticus minor: Originates slightly superior and medial to the major, also from the zygomatic bone, and inserts into the upper lip, medial to the corner of the mouth.

    Both muscles lie superficial to the buccinator and deep to the skin, with the minor muscle positioned just above the major.

    3. Structure

    The zygomaticus muscles are slender, strap-like muscles with the following characteristics:

    • Muscle type: Skeletal, voluntary muscle.

    • Innervation: Both are innervated by the facial nerve (cranial nerve VII), specifically the buccal and zygomatic branches.

    • Blood supply: Supplied by the facial artery and the transverse facial artery.

    • Fiber direction: Oriented obliquely downward and medially toward the mouth.

    4. Function

    The primary function of the zygomaticus muscles is to facilitate facial expressions:

    • Zygomaticus major: Pulls the corner of the mouth upward and laterally — the primary muscle involved in smiling.

    • Zygomaticus minor: Elevates the upper lip, exposing the maxillary teeth, and contributes to expressions like disdain or smugness.

    Together, these muscles help express joy, happiness, and other positive emotions through facial movement.

    5. Physiological role(s)

    While the zygomaticus muscles have no internal physiological functions, they serve important roles in:

    • Nonverbal communication: Critical for expressing emotions such as joy, friendliness, or sarcasm.

    • Speech and articulation: Assist in subtle lip movements necessary for phoneme formation and oral articulation.

    • Social bonding: Smiling and expressive gestures foster interpersonal connections and influence perception in social interactions.

    6. Clinical Significance

    Disorders and injuries affecting the zygomaticus muscles can have both functional and aesthetic consequences:

    • Facial nerve palsy (e.g., Bell's palsy):

      • Damage to cranial nerve VII may result in paralysis or weakness of the zygomaticus muscles, leading to an asymmetric smile or drooping of the mouth on one side.

    • Stroke-related facial weakness:

      • Upper motor neuron lesions may impair voluntary control of smiling, while reflexive emotional expression may remain intact (emotional facial paresis).

    • Botox injections:

      • Incorrectly placed cosmetic Botox may temporarily paralyze the zygomaticus major, resulting in an unnatural or asymmetric facial appearance.

    • Facial reconstructive surgery:

      • Reanimation procedures may use muscle grafts or nerve transfers to restore smile function if the zygomaticus is damaged or nonfunctional.

    • Congenital facial asymmetry:

      • Conditions like Moebius syndrome may involve hypoplasia or absence of the zygomaticus muscles.

    Did you know? The clavicle is the only bone in the body that connects the arm to the body trunk.