Muscles of the Body (you need to know)

FACIAL MUSCLES

The facial muscles are the only group of muscles that insert into the skin. When contracting, the muscles pull on the skin and exert their effects.  

HERE IS WHAT SOME IF THEM DO:

• Nasalis- compresses the nares (nostrils) or opens nares  
• Orbicularis Oris- purses lips (Kissing muscle)
• Buccinator- pulls cheek inwards against teeth
• Platysma- draws corners of mouth downwards, tense neck
• Masseter, a muscle that runs from each cheek to each side of your jaw and helps your jaw close
• Temporalis, a fan-shaped muscle that helps your jaw close
• Orbicularis Oculi, which closes your eyelids (Squinting muscle)
• Frontalis- Wrinkles forehead (Need Botox anyone?)
• Zygomaticus (major and minor)- your SMILE muscles

NECK MUSCLES

ANTERIOR SHOULDER MUSCLES & UPPER THORAX (CHEST)

• Deltoid- stabilizes shoulder and moves arm in many directions
• Pectoralis Major- its major actions are adduction, or depression, of the arm and rotation of the arm forward about the axis of the body. 
• Pectoralis Minor- its major actions of this muscle include the stabilization, depression, abduction or protraction, upward tilt, and downward rotation of the scapula
• Subscapularis- muscle internally rotates and adducts the humerus

POSTERIOR SHOULDER MUSCLES & UPPER BACK (CHEST)

• Trapezius- used to tilt and turn the head and neck, shrug, steady the shoulders, maintain upright posture and twist the arms. The trapezius elevates, depresses, rotates, and retracts the scapula, or shoulder blade.
• Supraspinatus- is a rotator cuff muscle that abducts the arm and stabilizes the humeral head in the shoulder joint 
• Infraspinatus- is the main external rotator of the shoulder and acts to stabilize the head of the humerus 
• Rhomboid (Minor & Major)- Scapular Retraction & Scapular Elevation
• Latissimus Dorsi- Strong "lats" help you use your arms to pull your body weight up, accessory breathing muscle, and adduction of the arm
• Serratus Anterior- to lift the ribs, assisting with respiration and protracts the shoulder blades. This means that they pull them forward around your rib cage. Think of a boxer throwing a punch. 
• Serratus Posterior- The serratus posterior superior helps to elevate the upper ribs during inhalation. The serratus posterior inferior, inversely, helps to draw the lower ribs downward and backward during exhalation 
• Teres Minor- rotates the arm laterally and assists in bringing it toward the body, helps stabilize shoulder joint
• Teres Major-  also aids in rotating the arm but its function is just the opposite of the teres minor and other muscles in the rotator cuff
• Erector Spinae- straighten and rotate the back, used for lifting and posture

ANTERIOR ABDOMINAL WALL

APONEUROSIS (def)- a flat sheet or ribbon of tendon-like material that anchors a muscle or connects it with the part that the muscle moves.

THE 6 PACK 

Linea Alba (not a muscle)- the ab crack and it's a tendinous inscription between your ab muscles. Its function is to balance contractile forces from the muscles attached to it (formed by the fusion of the aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles form the rectus sheaths, which enclose the rectus abdominis muscles.

In muscular individuals its presence can be seen on the skin, forming the depression between the left and right halves of a "six pack". 

Tendinous Inscriptions (not a muscle)- three fibrous bands that cross the Linea Alba horizontally and allow the rectus abdominis muscles to contract in segments permitting greater control over the degree of forward flexion. 

• Rectus Abdominis- Flexion of the trunk (flexion of thoracic and lumber spine), while it works by drawing pubic symphysis and sternum toward each other. Tense the anterior wall of the abdomen and assist in compressing the contents of the abdomen. It works on posterior pelvic tilt with other abdominal muscles. Play a role in core stability.

• External Obliques- Bilateral contraction - Trunk flexion, compresses abdominal viscera, expiration. Unilateral contraction - Trunk lateral flexion (ipsilateral), trunk rotation (contralateral)
• Internal Obliques- flexes the trunk when bilaterally contracted and lateral flexion upon unilateral contraction, compression causes increase in the intraabdominal pressure
• Transverse Abdominals (TVA) - A weak TVA is often one of the many reasons people may experience low back pain

POSTERIOR LOWER BACK AND LEG MUSCLES

• Gracilis- flexes the knee, adducts the thigh, and medially rotate the tibia on the femur
• Adductor Magnus- Adduction of hip (both portions) flexion of hip (adductor portion) extension of hip (hamstring portion) 
• Iliotibial Tract- flex, extend, abduct, and laterally and medially rotate the hip
• Semimembranosus- knee flexion, knee internal rotation and hip extension
• Semitendinosus- Flexes and medially rotates knee. Extends hip 
• Biceps Femoris- Hip joint: thigh extension, thigh external rotation;
  Knee flexion, leg external rotation; stabilizes pelvis 

ANTERIOR THIGH

• Psoas Major- flexion of the hip joint
• Pectineus- both flexes and adducts the thigh at the hip joint when it contracts
• Adductor Longus- to adduct the thigh at the hip joint
• Rectus Femoris- is used powerfully when you kick a football or soccer ball. It is also used in cycling. Extends the lower leg at the knee joint and stabilizes the patella. Additionally facilitates rotation at the hip.  
• Vastus Lateralis- is the largest and most powerful part of the quadriceps, a muscle in the thigh. Extends the knee joint 
• Vastus Intermedius- Knee extension and patella stabilization
• Vastus Medialis- Knee extension and patella stabilization 
• Sartorius-  can move the hip joint and the knee joint, but all of its actions are weak, making it a synergist muscle 

POSTERIOR SHIN

• Gastrocnemius- is the larger calf muscle, forming the bulge visible beneath the skin. It is a powerful plantar flexor, also a powerful knee flexor. During walking, running, or jumping, the calf muscle pulls the heel up to allow forward movement
• Soleus- plantar flexor and posture while walking. Plays an important role in maintaining standing posture, making sure your body doesn't fall forward 
• Calcaneal (Achilles) Tendon- The Achilles tendon is the largest and strongest tendon in the body. When the calf muscles flex, the Achilles tendon pulls on the heel. This movement allows us to stand on our toes when walking, running, or jumping. 

In Greek mythology, when Achilles was an infant, it was foretold that he would perish at a young age. To prevent his death, his mother Thetis took Achilles to the River Styx, which was supposed to offer powers of invulnerability. She dipped his body into the water but, because she held him by his heel, it was not touched by the water of the river. Achilles grew up to be a man of war who survived many great battles. But was shot in the Achilles which killed him. This is why people say you may have an "Achilles Heel".

ANTERIOR SHIN

• Tibialis Anterior- acts to dorsiflex and invert the foot
• Tibialis Posterior- plantarflex and invert the ankle. It also plays an important role in stabilizing the medial longitudinal arch. Tibialis posterior dysfunction can lead to flat feet and weak arch control in adults.