Adductor Muscles

Adductor muscles move a limb toward the central line of the body or a digit toward the axis of a limb. It comes from the Latin word, "adductus," meaning "one that draws to". An adductor is also a muscle that closes the valves in a clam or other bivalve mollusk, but it isn't the one that snaps the human mouth shut.

Hamstring Muscles

As the name implies, the "biceps femoris" has two heads, or immovable ends, one attached to the ischium (bone in the pelvis) and the other attached to the femur (thigh bone). The muscle passes along the back of the thigh on the lateral side and connects close to the midline ends of the fibula and tibia (bones in the lower leg). The biceps femoris is one of the hamstring muscles, and its tendon (hamstring) can be felt as a ridge behind the knee. This muscle functions to flex and rotate the leg laterally and to extend the thigh. The "semitendinosus" is another of the hamstring muscles. It is a long, bandlike muscle on the back of the thigh toward the inside, connecting the ischium to the proximal end of the tibia. It is so named because it becomes tendinous in the middle of the thigh, continuing to its movable end as a long, cordlike tendon. It functions to flex and rotate the leg medially and to extend the thigh. The "semimembranosus" is the third hamstring muscle and is the most inner-located muscle in the back of the thigh. It connects the ischium to the tibia and functions to flex and rotate the leg medially and to extend the thigh.

Anconeus Muscle

The anconeus is a small, triangular muscle, which lies on the elbow joint and appears to be a continuation of the triceps brachii. It assists in extending the forearm and is supplied by a branch of the radial nerve.

Biceps Brachii

Some muscles have more than one origin (immovable end) or insertion (movable end). The "biceps brachii" in the upper arm, for example, has two origins. This is shown in its name, "biceps," which means "two heads." It is attached to the scapula (shoulderblade) in two places and extends along the front surface of the humerus (upper arm bone). It is inserted by means of a tendon on the largest part of the radius (lower arm bone). When it contracts, the movable end is pulled toward the origin, and the arm bends at the elbow.

Brachialis

The brachialis is a large muscle beneath the biceps brachii. It connects the shaft of the humerus (upper arm bone) to the ulna (longest) forearm bone) and is the strongest flexor of the elbow.

Brachioradalis Muscle

The brachioradalis connects the humerus (upper arm bone) to the radius (shortest lower arm bone) and aids in flexing the elbow.

Extensor Carpi Radialis Brevis

The extensor carpi radialis brevis is a companion of the extensor carpi radialis longus and extends toward the middle of it. This muscle runs from the humerus (upper arm bone) to the bones in the hand and functions to extend the wrist. It also assists in abducting the hand.

Extensor Carpi Radialis Longus

The extensor carpi radialis longus runs along the lateral side of the forearm, connecting the humerus (upper arm bone) to the hand. It functions to extend the wrist and assists in abducting the hand.

Extensor Carpi Ulnaris

The extensor carpi ulnaris is located along the outer surface of the ulna (longer forearm bone) and connects the humerus (upper arm bone) to the hand. It acts to extend the wrist and assists in abducting it.

Dorsal Flexors

A number of muscles that function to move the ankle, foot, and toes are located in the lower leg. They attach the femur (upper leg bone), tibia, and fibula (lower leg bones) and to various bones in the foot and are responsible for a variety of movements - moving the foot upward (dorsiflexion) or downward (plantar flexion), and turning the sole of the foot inward (inversion) or outward (eversion). The "dorsal flexor muscles" include the following: The "tibialis anterior" is a dorsal flexor and is an elongated, spindle-shaped muscle located on the front of the lower leg. It arises from the surface of the tibia to pass on the inside over the far end of the tibia, and attaches to bones of the ankle and foot. Contraction of the tibialis anterior causes dorsiflexion and inversion of the foot. The tibialis posterior muscle helps stabilize the foot while walking. The "peroneus tertius" is a muscle of variable size that connects the fibula to the outside of the foot. It functions in dorsiflexion and eversion of the foot. The"extensor digitorum longus" is situated along the outside of the lower leg, just behind the tibialis anterior. It comes from close to the midline of the tibia and the shaft of the fibula. Its tendon divides into four parts as it passes over the front of the ankle. These parts continue over the surface of the foot and attach to the four smaller toes. The actions of this muscle include dorsiflexion of the foot, eversion of the foot, and extension of the toes.

Hallucis

The hallux (plural, hallucis) are muscles pertaining to the big toe. The "extensor hallucis longus" are muscles used in extending the toe; the "flexor hallucis longus" are used in flexing it and moving it to the side.

Femur

The "femur" is the thigh bone, the longest bone in the body. The lower end joins the tibia (shin) to form the knee joint. The upper end is rounded into a ball (or "head" of the femur) that fits into a socket in the pelvis to form the hip joint. Just below the head is a constriction, or neck, and two large processes - an upper, lateral "greater trochanter" and a lower, medial "lesser trochanter." These processes provide attachments for muscles of the legs and buttocks. Femoral condyles are large, rounded bumps on the distal end of the femur. They articulate (come in contact) with the condyles of the tibia and form part of the knee joint. The neck of the femur gives the hip joint a wide range of movement, but it is a point of weakness and a common site of fracture.

Fibula

The fibula is the outer and thinner of the two long bones of the lower leg. It is much narrower than the other bone (the shin), to which it runs parallel and to which it is attached at both ends by ligaments. The upper end of the fibula does not reach the knee, but the lower end descends below the shin and forms part of the ankle. Its main function is to provide attachment for muscles. It doesn't give much support or strength to the leg, which explains why the bone can safely be used for grafting onto other bones in the body.

Flexor Muscles

A flexor muscle is one which decreases the angle between two bones, as in bending the arm at the elbow; raising the leg toward the stomach as in kicking a football; or bringing the lower leg up toward the thigh. Another flexor muscle will bring the thumb across the palm of the hand. A "dorsiflexior" is used for the movement at the ankle joint in trying to bring the foot in proximity to the leg

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Plantar Flexor Muscles

A number of muscles functioning to move the ankle, foot, and toes are located in the lower leg. They attach the femur (upper leg bone), tibia, and fibula (lower leg bones) and to various bones in the foot and are responsible for a variety of movements - moving the foot upward (dorsiflexion) or downward (plantar flexion), and turning the sole of the foot inward (inversion) or outward (eversion). The "plantar muscles" include the following: The "gastrocnemius," on the back of the lower leg, forms part of the calf. It comes from two immovable ends (or heads) located on the femur, one on the side and one toward the center. The far end of this muscle joins the strong "Achilles tendon," which descends to the heel and attaches to the calcaneus. The gastrocnemius is a powerful plantar flexor of the foot, that aids in pushing the body forward when a person walks or runs. It also works to flex the leg at the knee. The "soleus" is a thick, flat muscle located beneath the gastrocnemius. These two muscles make up the calf of the leg. The soleus rises from the tibia and fibula, and it extends to the heel by way of the Achilles tendon. It acts with the gastrocnemius to cause plantar flexion of the foot. The "flexor digitorum longus" extends from the back surface of the tibia to the foot. Its tendon passes along the plantar surface of the foot. There, it divides into four parts that attach to the terminal bones of the four small toes. It assists in plantar flexion of the foot, flexion of the four small toes, and inversion of the foot.

Flexor Digitorum Profundis

The flexor digitorum profundis is a large muscle that connects the ulna (longest forearm bone) to the bones of the fingers. It acts to flex the distal joints of the fingers, as when a fist is made.

Flexor Digitorum Superficialis

The flexor digitorum superficialis is a large muscle located beneath the flexor carpi ulnaris. It arises from three immovable muscles - one from the middle inside of the humerus (upper arm bone), one from the middle inside of the ulna (longest forearm bone), and one from the radius (shortest forearm bone). Its movable end is in the tendons of the fingers and acts to flex the fingers and, by a combined action, to flex the hand.

Posterior Thigh Muscles

The "gluteus maximus" is the strongest muscle in the body and covers a large part of the buttock. It connects the ilium, sacrum, and coccyx to the femur by tissues of the thigh and acts to extend the thigh. The gluteus maximus causes the leg to straighten at the hip when a person walks, runs, or climbs. It is also used to raise the body from a sitting position. The "gluteus medius" is partly covered by the gluteus maximus. Its fibers extend from the ilium to the femur, and they function to move the thigh out and rotate it medially. The "gluteus minimus" lies beneath the gluteus medius and is its companion in attachments and functions. The "tensor fasciae latae" connects the ilium to the tissues of the thigh, which continues downward to the tibia (bone in the lower leg). This muscle functions to abduct and flex the thigh and to rotate it.

Gracilis Muscle

The "gracilis" is a long, straplike muscle that passes from the pubic bone to the tibia in the lower leg. It functions to adduct the thigh and to flex and rotate the leg medially at the knee.

Humerus

The humerus is the bone of the upper arm. The smooth, dome-shaped head of the bone lies at an angle to the shaft and fits into a shallow socket of the scapula (shoulder blade) to form the shoulder joint. Below the head, the bone narrows to form a cylindrical shaft. It flattens and widens at the lower end and, at its base, it joins with the bones of the lower arm (the ulna and radius) to make up the elbow. Some people say the "funny bone" is named because it is next to the humerus. It really isn't a bone at all, but is the ulnar nerve, which passes under a prominence of the humerus, where it is vulnerable. To find the funny bone, put the point of the right elbow on a table. Above and to the left of the point is a big knob. When it is struck, the blow pushes the nerve against this knob, causing temporary paralysis. It is no laughing matter, but it is a "funny" feeling.

Iliopsoas Muscles

The iliopsoas muscle is frequently regarded as a single muscle, because it is a blending of two muscles, the psoas major and the iliacus. The "psoas major" is a powerful flexor muscle of the thigh at the hip joint. If both psoas major muscles are fixed from below, they act as important flexors of the trunk on the hip, as in sitting up from a lying-down position. The "psoas minor" is a weak flexor of the trunk and the lumbar spinal column. It is supplied by a branch of the first lumbar nerve. The "iliacus" works with the psoas major as a powerful flexor of the thigh at the hip joint. It joins the psoas in a number of other actions as the "iliopsoas."

Triceps Brachii Muscles

The triceps brachii has three heads (connective immovable muscle) and is the only muscle on the back of the upper arm. It connects the humerus (upper arm bone) and the scapula (shoulder blade) to the ulna (longest of the forearm bones) and is the primary extensor of the elbow. The three heads are the "lateral," the "medial," and the "long head."

Adductor Longus

The adductor longus is a long, triangular muscle that runs from the pubic bone to the femur. It functions to adduct, or move the thigh inward, and assists in flexing and rotating it to the side.

Palmaris Longus

The palmaris longus is one of the most variable muscles in the body and is sometimes (10%%) absent. It may be mostly tendon near the point of attachment and muscular at the far end, or it may be muscular in the center with tendons above and below. It may have two bundles of muscle with a central tendon, or it may be made up of a tendinous band, or the muscle make-up may be doubled. Its function is to flex the hand at the wrist.

Pectineus Muscle

The pectineus is a flat, quadrangular muscle, situated at the front part of the upper and middle part of the thigh. It arises from the pectin pubis (called the "pectineal line") and, to some extent, from the surface of the bone just in front of it. Some fiber also comes from the tissue covering the front surface of the muscle itself. The pectineus muscle flexes and moves the thigh toward the body and rotates it toward the center.

Peroneus Brevis Muscle

The peroneus brevis muscle originates from the mid portion of the shaft of the fibula and inserts on the base of the #5 metatarsal bone. It extends and abducts the foot.

Evertor Muscle

The "peroneus longus" is the evertor muscle, meaning to turn the sole of the foot outward. It is a long, straplike muscle located on the outside of the lower leg. It connects the tibia and the fibula (the lower leg bones) to the foot by means of a stout tendon that passes behind the lateral malleolus (network of nerves and muscles around the ankle). It functions in eversion of the foot, assists in plantar flexion (moving it downward), and helps support the arch of the foot. The corresponding muscle in the hand and forearm is called the "peroneus brevis" muscle.

Pronator Teres

The pronator teres is a short muscle connecting the ends of the humerus (upper arm bone) and ulna to the radius (forearm bones). It functions to rotate the arm toward the inside, as when the hand is turned so the palm is facing downward (pronation).

Radius

The radius is the shorter of the two long bones of the forearm. The other is the ulna. The radius is the bone on the thumb side of the arm. The shaft of the radius has a broad base that joins the lower end of the ulna and the upper bones of the wrist at a large process called the radial styloid. The disk-shaped head of the radius, which is smaller than the base, joins the lower end of the humerus (bone in the upper arm) to form the elbow joint.

Quadriceps Femoris Muscles

A large, fleshy group called the "quadriceps femoris" occupies the front and sides of the thigh and is primary extensor of the knee. It is composed of four parts - "rectus femoris," "vastus lateralis," "vastus medialis," and "vastus intermedius." These parts connect the ilium and femur to a common "patellar tendon," which passes over the front of the knee and attaches to the patella (knee cap). This tendon then continues as the "patellar ligament" to the tibia (lower leg bone.)

Sartorius Muscle

The sartorius is the longest muscle in the body. It is narrow and ribbon-like and stems from the iliac spine and the upper half of the notch below it. It slants across the front of the upper thigh from the side to the middle and then descends vertically to the knee. It ends in a tendon that expands to be inserted into the surface of the body of the tibia (leg bone). The sartorius flexes, abducts (moves away from the body), and rotates the thigh sideways at the hip. It also flexes the leg at the knee joint and rotates it slightly after flexing. These actions draw the lower extremities into a sitting position and place the heel of one foot on the knee of the other. This is sometimes called a "tailor's position".

Supinator Muscle

The supinator is a short muscle whose fibers run from the ulna (long forearm bone) and the lateral end of the humerus (upper arm bone) to the radius (short forearm bone). It assists the biceps brachii in rotating the forearm laterally (supination).

Tibia

The tibia is the inner and thicker of the two long bones in the lower leg. It is also called the shin bone. Its upper end is expanded into "medial" and "lateral condyles," which have concave surfaces and unite with the condyles of the femur. The tibia is the supporting bone of the lower leg and runs parallel to the other, smaller bone (the fibula) to which it is attached by ligaments. The front of the tibia, or tibial tuberosity, lies just below the skin and can easily be felt. The tibial tuberosity is a region on the bone where muscles and tendons attach (or an "apophysis"). The upper end joins the femur to form the knee joint, and the lower end forms part of the ankle joint. On the inside of the ankle, the tibia widens and sticks out to form a large bony prominence called the "medial malleolus." On the outside of the ankle is a protrusion called the "lateral malleolus," which is sometimes called the ankle bone, and is the most common area for ankle sprains. The lateral meniscus of the knee is a thick, crescent-shaped piece of cartilage which acts as padding. It lies between the joint where the femur and tibia articulate (come in contact with each other) on the outside of the knee. Likewise, the medial meniscus lies in the joint on the inside of the knee. The menisci are vital to absorbing shock from the knees, as well as providing lubrication and stabilization. Therefore, every attempt is made to repair (and more recently even to replace) worn or injured menisci.

Ulna

The ulna is the longer of the two bones of the forearm; the other being the radius. When the palm faces forward, the ulna is the inner bone (the one nearest the body) running down the forearm parallel to the radius. The upper end joins with the radius and extends into a rounded projection that fits around the lower end of the humerus (the upper arm bone) to form the elbow joint. The lower end of the ulna is rounded and forms a joint with the wrist bones and lower end of the radius.