Anatomy 262 Chapter 11

Anterior, Lateral, Superficial posterior, Deep posterior Compartments

The tibia and fibula, crural interosseous membrane, and septa in the leg create four major compartments.

Muscles that Move the Leg

1. Most of the extensor muscles originate on the femoral surface and extend along the anterior and lateral surfaces of the thigh a. Collectively the knee extensors are called the quadriceps muscles or the quadriceps femoris. o The three vastus muscles originate along the body of the femur, and they cradle the rectus femoris muscle. • Vastus lateralis • Vastus medialis • Vastus intermedius b. All four muscles insert upon the tibial tuberosity via the quadriceps tendon, patella, and patellar ligament. c. The rectus femoris muscle originates on the anterior inferior iliac spine, so in addition to producing extension of the knee, it can assist in flexion of the hip. 2. Flexor muscles originate on the pelvic girdle and extend along the posterior and medial surfaces of the thigh a. The flexors of the knee include the biceps femoris, semimembranosus, semitendinosus and sartorius muscles o These muscles originate along the edges of the pelvis and insert upon the tibia and fibula. o Their contractions produce flexion at the knee. o The biceps femoris, semimembranosus, and semitendinosus muscles originate on the pelvis inferior and posterior to the acetabulum, their contractions also produce extension at the hip. • These muscles are often called the hamstrings. o The sartorius muscle is the only knee flexor that originates superior to the acetabulum • Its insertion lies along the medial aspect of the tibia. • It produces flexion and lateral rotation at the hip, as when crossing the legs. 3. The small popliteus muscle originates on the femur near the lateral condyle and inserts on the posterior tibial shaft a. This muscle contracts to produce a slight medial rotation of the tibia that unlocks the joint.

Muscles that Move the Forearm and Hand

1. Most of the muscles that move the forearm and hand originate on the humerus and insert upon the forearm and wrist. There are two noteworthy exceptions: a. The long head of the triceps brachii muscle originates on the scapula and inserts on the olecranon o The triceps brachii muscle extends the elbow b. The long head of the biceps brachii muscle originates on the scapula and inserts on the radial tuberosity of the radius o The biceps brachii muscle both flexes the elbow and supinates the forearm. 2. The brachialis and brachioradialis muscles also flex the elbow and are located on the anterior arm and lateral forearm. 3. The anconeus and the triceps brachii muscles are located on the posterior arm and elbow and extend the arm. 4. The flexor carpi ulnaris, the flexor carpi radialis, and the palmaris longus are superficial muscles that work together to produce flexion of the wrist a. These muscles can all be seen on the surface of the anterior forearm. b. The flexor carpi radialis muscle flexes and abducts c. The flexor carpi ulnaris muscle flexes and adducts. 5. The extensor carpi radialis muscle and the extensor carpi ulnaris muscle of the posterior forearm produce extension of the wrist. a. Extensor carpi radialis muscle produces extension and abduction b. Extensor carpi ulnaris muscle produces extension and adduction. 6. The pronator teres muscle and the supinator muscle are antagonistic muscles that originate on both the humerus and the ulna. a. They insert on the radius and cause rotation without flexing or extending the elbow. 7. The pronator quadratus muscle originates on the ulna and assists the pronator teres muscle in opposing the actions of the supinator muscle or biceps brachii muscle. a. The last three muscles are involved in pronation and supination

Muscles that Move the Thigh

1. Muscles originating on the surface of the pelvis and inserting on the femur will produce characteristic movements determined by their position relative to the acetabulum a. Gluteal muscles cover the lateral surface of the ilium o The gluteus maximus muscle is the largest and most superficial of the gluteal muscles. • It originates along the posterior gluteal line and adjacent portions of the iliac crest; the sacrum, coccyx, and associated ligaments; and the thoracolumbar fascia. • Acting alone, this massive muscle produces extension and lateral rotation at the hip. • The gluteus maximus muscle shares an insertion with the tensor fasciae latae muscle, which originates on the iliac crest and lateral surface of the anterior superior iliac spine. a. Together these muscles pull on the iliotibial tract, a band of collagen fibers that extends along the lateral surface of the thigh and inserts upon the tibia to produce abduction of the hip. • This tract provides a lateral brace for the knee that becomes particularly important when a person balances on one foot. o The gluteus medius and gluteus minimus muscles originate anterior to the gluteus maximus and insert upon the greater trochanter of the femur. • Both produce abduction and medial rotation at the hip joint. b. The six lateral rotators originate at, or are inferior to, the horizontal axis of the acetabulum and insert on the femur. o All cause lateral rotation of the thigh • The piriformis muscle produces abduction at the hip. o The piriformis and the obturator muscles are the dominant lateral rotators. c. The adductors are located inferior to the acetabular surface. o The adductors include the: • Adductor magnus muscle • Adductor brevis muscle • Adductor longus muscle • Pectineus muscle • Gracilis muscle o All originate on the pubis; and all of the adductors except the gracilis muscle insert on the linea aspera • The gracilis inserts on the tibia. o All of the adductors except the adductor magnus muscle originate both anterior and inferior to the hip joint, so they produce hip flexion as well as adduction. • The adductor magnus muscle can produce either adduction and flexion or adduction and extension, depending on the region stimulated. d. A single pair of muscles dominates the medial surface of the pelvis. o The psoas major muscle originates alongside the inferior thoracic and lumbar vertebrae, and its insertion lies on the lesser trochanter of the femur. o Before reaching this insertion, its tendon merges with that of the iliacus muscle, which lies nestled within the iliac fossa. • These two muscles, which are powerful flexors of the hip, pass deep to the inguinal ligament, and are often referred to as the iliopsoas muscle.

Muscles that Move the Hand and Fingers

1. Several superficial and deep muscles of the forearm perform flexion and extension at the joints of the fingers. a. Only the tendons of these muscles extend across the wrist joint. b. These are relatively large muscles and keeping them clear of the joints ensures maximum mobility at both the wrist and hand. o The tendons that cross the dorsal and ventral surfaces of the wrist pass through synovial tendon sheaths, elongated bursae that reduce friction. o The fascia of the forearm thickens on the posterior surface of the wrist to form a wide band of connective tissue, the extensor retinaculum • The extensor retinaculum holds the tendons of the extensor muscles in place. o On the anterior surface, the fascia also thickens to form another wide band of connective tissue, the flexor retinaculum • The flexor retinaculum retains the tendons of the flexor muscles a. Inflammation of the retinacula and tendon sheaths can restrict movement and irritate the median nerve, a sensory and motor nerve that innervates the hand. • This condition is known as carpal tunnel syndrome. c. The muscles of the forearm that provide strength and crude control of the hand and fingers are called the extrinsic muscles of the hand. 2. Fine control of the hand involves small intrinsic muscles that originate on the carpal and metacarpal bones

Muscles that Position the Pectoral Girdle

1. The large trapezius muscles cover the back and portions of the neck, extending to the base of the skull. a. These muscles originate along the middle of the neck and back and insert upon the clavicles and the scapular spines. b. Together, these triangular muscles form a broad diamond. c. The trapezius muscles are innervated by more than one nerve d. Because specific regions of the trapezius can be made to contract independently, its actions are quite varied. 2. Removing the trapezius reveals the rhomboid and the levator scapulae muscles a. These muscles are attached to the dorsal surfaces of the cervical and thoracic vertebrae. b. They insert along the vertebral border of each scapula, between the superior and inferior angles. c. Contraction of the rhomboid muscles adducts (retracts) the scapula, pulling it toward the center of the back. d. The levator scapulae elevate the scapula, as in shrugging the shoulders. 3. On the lateral wall of the chest, the serratus anterior muscle originates along the anterior and superior surfaces of several ribs a. This fan-shaped muscle inserts along the anterior margin of the vertebral border of the scapula. b. When the serratus anterior contracts, it abducts (protracts) the scapula and swings the shoulder anteriorly. 4. Two deep chest muscles arise along the ventral surfaces of the ribs. a. The subclavius muscle inserts upon the inferior border of the clavicle b. The pectoralis minor muscle attaches to the coracoid process of the scapula o Its contraction usually complements that of the subclavius.

Muscles that Move the Arm

1. The muscles that move the arm are easiest to remember when grouped by primary actions. a. The deltoid muscle is the major abductor of the arm o The supraspinatus muscle assists at the start of this movement. b. The subscapularis and teres major muscles rotate the arm medially c. The infraspinatus and teres minor muscles perform lateral rotation. o All of these muscles originate on the scapula. d. The small coracobrachialis muscle is the only muscle attached to the scapula that produces flexion and adduction at the shoulder joint. e. Two large muscles can work together to produce adduction and medial rotation of the humerus at the shoulder joint. o The pectoralis major muscle extends between the anterior portion of the chest and the crest of the greater tubercle of the humerus. • The pectoralis major muscle also flexes the shoulder joint o The latissimus dorsi muscle extends between the thoracic vertebrae at the posterior midline and the floor of the intertubercular groove of the humerus • The latissimus dorsi muscle also extends the shoulder joint. 2. The surrounding muscles provide substantial support for the highly mobile but relatively weak shoulder joint. a. The tendons of the supraspinatus, infraspinatus, subscapularis, and teres minor muscles support the joint capsule and limit the range of movement. o These muscles form the rotator cuff

Muscles that Move the Foot and Toes

1. The muscles that move to foot may be extrinsic or intrinsic to the foot. The extrinsic muscles are: a. Two very large muscles move the ankle produce the plantar flexion involved with walking and running movements. o The large gastrocnemius muscle of the calf is an important plantar flexor • The gastrocnemius muscle arises from two tendons attached to the medial and lateral condyles and adjacent portions of the femur. o The underlying soleus muscle • The gastrocnemius and soleus muscles share a common tendon, the calcaneal tendon, or the Achilles tendon. b. The two fibularis muscles, also known as the peroneus muscles, are partially covered by the gastrocnemius and soleus muscles. o Peroneus muscles produce eversion of the foot as well as plantar flexion of the ankle. c. Inversion of the foot is caused by contraction of the tibialis muscles o The large tibialis anterior muscle opposes the gastrocnemius muscle and dorsiflexes the ankle d. Important muscles that move the toes originate on the surface of the tibia, the fibula, or both o Large tendon sheaths surround the tendons of the tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles where they cross the ankle joint. • The positions of these sheaths are stabilized by the superior and inferior extensor retinacula. 2. The small intrinsic muscles that move the toes originate on the bones of the tarsus and foot a. Some of the flexor muscles originate at the anterior border of the calcaneus; their muscle tone contributes to maintenance of the longitudinal arch of the foot. b. As in the hand, small interosseus muscles originate on the lateral and medial surfaces of the metatarsal bones.

Deep Fascia

A dense fibrous layer bound to capsules, periostea, epimysia, and other fibrous sheaths surrounding internal organs.

Superficial Fascia

A layer of areolar tissue deep to the skin.

Subserous Fascia

A layer of areolar tissue separating a serous membrane from adjacent structures.

Anterior Compartment of the Upper Limb

Compartment containing the biceps brachii, coracobrachialis, and brachialis muscles.

Posterior Compartment of the Upper Limb

Compartment containing the the triceps brachii muscle.

Posterior Compartment of the Lower Limb of the Thigh

Contains the Hamstrings.

Medial Compartment of the Lower Limb of the Thigh

Contains the adductors.

Anterior Compartment of the Lower Limb of the Thigh

Contains the quadriceps group.

Appendicular Musculature

Muscles that are responsible for stabilizing the pectoral and pelvic girdles and for moving the upper and lower limbs. 1. __________ ___________ account for roughly 40 percent of the skeletal muscles in the body.