Microscopic view
Step 1
Choose an organ
Step 2
Explore it in 3D
- Deltoid: The rounded cap of the shoulder, its three parts able to lift the arm in almost any direction; the standard site for an intramuscular injection
- Biceps Brachii: Two heads crossing both the shoulder and the elbow, flexing the elbow and turning the forearm to face the palm up
- Pectoralis Major: The broad fan of the chest wall, drawing the arm across the body and forming the anterior wall of the armpit
- Rectus Abdominis: The paired vertical strap of the abdominal wall, its tendinous intersections giving a lean abdomen its visible segments
- Gluteus Maximus: The largest and most powerful muscle in the body, driving the hip from a bent to a straight position in climbing and sprinting
- Gastrocnemius: The calf's two-headed muscle, crossing both knee and ankle to point the foot and power the push-off of every stride
- Trapezius: A broad sheet from skull to mid-back that lifts, rotates and steadies the shoulder blade against the trunk
- Latissimus Dorsi: The widest muscle of the back, pulling the raised arm down and back — the muscle a pull-up is built on
- Triceps Brachii: The elbow's sole extensor, three heads converging on one tendon at the point of the elbow
- External Oblique: The outermost of the abdominal wall's three angled sheets, rotating the trunk and bracing it against the muscle beneath
- Quadriceps Femoris: Four heads sharing one tendon around the patella, the body's principal knee extensor and the muscle that fails first climbing stairs
- Hamstrings: Three muscles down the back of the thigh, extending the hip and flexing the knee — and among the most commonly strained in sprinting
- Tibialis Anterior: The shin's prominent tendon, lifting the front of the foot clear of the ground during the swing of each step
- Masseter: The strongest muscle for its size in the body, closing the jaw with a bite force that can exceed body weight
- Sternocleidomastoid: The cord that stands out turning the head to one side, running from behind the ear to the collarbone and breastbone
- Diaphragm: The dome of muscle separating chest from abdomen; its flattening on contraction is what actually draws air into the lungs
Step 3
Keep learning
Compare organs
Muscles vs. skeleton
Function animation
Moves the skeleton, holds every joint stable against gravity, generates most of the body's resting heat, and powers breathing, swallowing and speech
Clinical notes
Red flags
- A limb that is tensely swollen, painful out of proportion to the injury, and worse on passive stretch of the muscles inside it is compartment syndrome — a surgical emergency measured in hours, not days, because pulses can stay normal until the damage is already done.
- Sudden weakness or drooping on one side of the face or body is a stroke until imaging says otherwise, and progressive weakness that climbs from the legs upward, or that worsens with repeated effort and threatens the breathing muscles, needs same-day neurological assessment.
- Dark, tea-coloured urine after unaccustomed or extreme exertion is rhabdomyolysis — muscle breakdown releasing myoglobin that can block the kidneys — and needs urgent fluids and a creatine kinase level before the kidneys are harmed.
- Muscle strain
- Tendinopathy
- Compartment syndrome
- Rhabdomyolysis
- Myasthenia gravis
- Muscular dystrophy
- Polymyositis
- Contracture
Where it works