Appendicular musculature

The appendicular musculature stabilizes the pectoral and pelvic girdles and moves the upper and lower limbs.
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The appendicular musculature stabilizes the pectoral and pelvic girdles and moves the upper and lower limbs.
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A muscle of the appendicular skeleton may cross one or more joints between its origin and insertion. The position of the muscle as it crosses a joint helps determine the action of that muscle.
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The primary action of a muscle whose insertion is close to a joint is to produce movement, whereas a muscle whose insertion is farther from a joint helps stabilize that joint.
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Four groups of muscles are associated with the pectoral girdle and upper limb: (1) muscles that position the pectoral girdle, (2) muscles that move the arm, (3) muscles that move the forearm and hand, and (4) muscles that move the hand and fingers.
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The trapezius covers the back and parts of the neck to the base of the skull. The trapezius affects the position of the pectoral (shoulder) girdle, head, and neck.
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Deep to the trapezius, the rhomboid adduct the scapula, and the levator scapulae elevates the scapula. Both insert on the scapula.
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The serratus anterior, which abducts the scapula and swings the shoulder anteriorly, originates along the anterior superior surfaces of several ribs
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Two deep chest muscles arise along the anterior surfaces of the ribs. Both the subclavius and the pectoralis minor depress and protract the shoulder.
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The deltoid and the supraspinatus produce abduction at the shoulder. The subscapularis and the teres major rotate the arm medially, whereas the infraspinatus and teres minor rotate the arm laterally. The supraspinatus, infraspinatus, subscapularis, and teres minor are known as the rotator cuff. The coracobrachialis flexes and adducts the shoulder.
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The pectoralis major flexes the shoulder, and the latissimus dorsi extends it. Both muscles adduct and medially rotate the arm
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The primary actions of the biceps brachii and the triceps brachii (long head) affect the elbow joint. The biceps brachii flexes the elbow and supinates the forearm, and the triceps brachii extends the elbow. Both have a secondary effect on the arm.The brachialis and brachioradialis flex the elbow. The anconeus and the triceps brachii oppose this action. The flexor carpi ulnaris, the flexor carpi radialis, and the palmaris longus are superficial muscles of the forearm that cooperate to flex the wrist. Additionally, the flexor carpi ulnaris adducts the wrist, and the flexor carpi radialis abducts it. The extensor carpi radialis and extensor carpi ulnaris extend and abduct the wrist. The pronator teres and pronator quadratus pronate the forearm without flexion or extension at the elbow; their action is opposed by the supinator muscle.Extrinsic muscles of the hand provide strength and gross motor control of the fingers. Intrinsic muscles provide fine motor control of the fingers and hand.The extrinsic muscles of the hand flex and extend the finger joints.Fine motor control of the hand involves small intrinsic muscles of the hand.The deep fascia of the upper limb separates the soft tissues into separate compartments. The arm consists of an anterior compartment and a posterior compartment. The forearm consists of four compartments: superficial anterior, deep anterior, lateral, and posterior.The relationships of the deeper muscles of the arm and forearm are best seen in sectional viewsThree groups of muscles are associated with the pelvis and lower limb: (1) muscles that move the thigh, (2) muscles that move the leg, and (3) muscles that move the foot and toes.Gluteal muscles cover the lateral surface of the ilium. The largest is the gluteus maximus which extends and laterally rotates the hip. It shares an insertion with the tensor fasciae latae which flexes, abducts, and medially rotates the hip. Together, these muscles pull on the iliotibial tract to laterally brace the knee.The piriformis and the obturator are the most dominant lateral rotators.The adductor group (adductor magnus, adductor brevis, adductor longus, pectineus, and gracilis) adduct the hip. Individually, they can produce various other movements, such as medial or lateral rotation and flexion or extension at the hipThe psoas major and the iliacus merge to form the iliopsoas, a powerful hip flexor.Extensor muscles of the knee lie along the anterior and lateral surfaces of the thigh; flexor muscles lie along the posterior and medial surfaces of the thigh. Flexors and adductors originate on the pelvic girdle, whereas most extensors originate on the femur.Collectively, the knee extensors are known as the quadriceps femoris. This group includes the vastus intermedius, vastus lateralis, vastus medialis, and rectus femoris.The flexors of the knee include the biceps femoris, semimembranosus, and semitendinosus (these "hamstrings" also extend the hip), and the sartorius. The popliteus medially rotates the tibia (or laterally rotates the femur) to unlock the knee joint.Extrinsic muscles move the foot and toes.The gastrocnemius and soleus produce plantar flexion. The large tibialis anterior opposes the gastrocnemius and dorsiflexes the ankle. The fibularis produces eversion as well as plantar flexion.Smaller muscles of the leg position the foot and move the toes.Muscles originating on the tarsal and metatarsal bones provide precise control of the phalanges.In addition to the functional approach used in this chapter, many anatomists study the muscles of the lower limb in groups determined by their position within compartments.The thigh has anterior, medial, and posterior compartments; the leg has an anterior, a lateral, and superficial and deep posterior compartments.