A&P Chapter 9 Muscles

External intercostals

(on the outside of the ribcase) wrap around from the back of the rib almost to the end of the bony part of the rib in front. Fix intercostal spaces during respiration. Aids forced inspiration by elevating ribs

Omohyoid

is a flat muscle belonging to the infrahyoid muscle group. It is critical to neck surgeries, particularly in the case of lymph node metastasis, which is the spread of cancer through the lymph nodes

Hamstring Group

Biceps femoris Semimembranosus Semitendinosus

Sarcoplasm

Cytoplasm of a muscle fiber that contains organelles, such as myofibrils. The sarcoplasm is the specialized cytoplasm of a muscle cell that contains the usual subcellular elements along with the Golgi apparatus, abundant myofibrils, a modified endoplasmic reticulum known as the sarcoplasmic reticulum (SR), myoglobin and mitochondria. Transverse (T)-tubules invaginate the sarcolemma, allowing impulses to penetrate the cell and activate the SR. As shown in the figure, the SR forms a network around the myofibrils, storing and providing the Ca2+ that is required for muscle contraction.

Structure of skeletal muscle

Skeletal muscles are usually attached to bone by tendons composed of connective tissue. This connective tissue also ensheaths the entire muscle & is called epimysium. Skeletal muscles consist of numerous subunits or bundles called fasicles (or fascicles). Fascicles are also surrounded by connective tissue (called the perimysium) and each fascicle is composed of numerous muscle fibers (or muscle cells). Muscle cells, ensheathed by endomysium, consist of many fibrils (or myofibrils), and these myofibrils are made up of long protein molecules called myofilaments. There are two types of myofilaments in myofibrils: thick myofilaments and thin myofilaments

Internal oblique

This muscle originates at the lumbar fascia (a connective tissue that covers the lower back), the outer portion of the inguinal ligament (a ligament located on the bottom-outer edge of the pelvis), and back of the iliac crest (the upper-outside portion of the pelvis. This muscle supports the abdominal wall, assists in forced respiration, aids in raising pressure in the abdominal area, and rotates and turns the trunk with help from other muscles. The internal abdominal oblique muscle is an opposing force to the diaphragm, reducing upper chest cavity volume during exhalation. As the diaphragm contracts, the chest cavity is pulled down to increase lung size.

Extensor carpi radialis longus

belongs to one of the main five muscles which facilitate movement of the wrist. When it comes to the dimensions of this muscle, it is pretty long. It starts on lateral side of humerus and attaches to the base of the second metacarpal bone which is the metacarpal of the index finger.

Iliopsoas

belongs to the inner hip muscles. It comprises a complex of two muscles with different areas of origin. This muscle belongs to the striated musculature and the innervation is carried by the femoral nerve as well as direct branches of the lumbar plexus. The psoas major and iliacus muscle unify in the lateral pelvis shortly before the inguinal ligament becoming the iliopsoas muscle. The iliopsoas muscle is the strongest flexor of the hip joint (important walking muscle). In the supine position it decisively supports the straightening of the upper body (e.g. during sit-ups). Furthermore it rotates the thigh laterally. A unilateral contraction leads to a lateral flexion of the lumbar vertebrae column. Altogether the iliopsoas muscle plays a significant role in the movement and stabilization of the pelvis.

Auricularis posterior

facial muscle of external ear; origin, mastoid process; insertion, posterior portion of root of auricle; action, draws back the pinna; nerve supply, facial.

Popliteus

is a band of muscular tissue located in the leg. The muscle wraps around the bottom half of the femur, or thighbone. It inserts on the back of the shinbone, or tibia, and runs through a bony projection at the bottom of the femur known as the lateral condyle of the femur. The popliteus muscle provides the knee with an added degree of mobility. With the muscle, the knee is able to rotate within the body by prompting the femur to turn on top of the tibia. Standing requires the least amount of activity from the popliteus muscle.

Masseter

is a facial muscle that plays a major role in the chewing of solid foods. The muscle is shaped similar to a parallelogram, connecting to the mandible (lower jawbone) and the cheekbone

Transversus thoracis

is a thin muscle on the inner surface of the anterior thoracic wall. Its origin lies on the dorsal surface of the xiphoid process and the body of the sternum. From there five insertion tendons run craniolaterally to the cartilage of the 2nd to 6th ribs giving it a serrated appearance.

Flexor digitorum superficialis

is an extrinsic muscle that allows the four medial fingers of the hand to flex. These fingers include the index, middle, ring, and pinkie fingers. The term extrinsic means that the muscle is located in the forearm. This muscle has two distinct heads, which both originate in the forearm.

Rectus femoris

is attached to the hip and helps to extend or raise the knee. This muscle is also used to flex the thigh. The rectus femoris is the only muscle that can flex the hip.

Depressor anguli oris

is attached to the lower jaw (mandible). It ends at the orbicularis oris, which is the ring-like muscle that encompasses the lips. It is attached at the edge of the lips. The depressor anguli oris muscle is associated with frowning, as it works to pull down the edges of the lips. This is a paired set of muscles, with one on either side of the mouth

Pronator teres

muscle is located on the palmar side of the forearm, below the elbow. Aided by the pronator quadratus, its function is to rotate the forearm palm-down. This is also known as pronation. The pronator teres muscle has two heads: the humeral head and the ulnar head. The pronator teres is innervated by the median nerve

Abductor pollicis longus

muscle is one of three muscles in the forearm that facilitate the movements of the thumb. The others are the extensor pollicis brevis and extensor pollicis longus. These three muscles, along with the extensor indicis, make up the group of muscles called the deep extensors.

Endomysium

Inside each skeletal muscle, muscle fibers are organized into individual bundles, each called a fascicle, by a middle layer of connective tissue called the perimysium. This fascicular organization is common in muscles of the limbs; it allows the nervous system to trigger a specific movement of a muscle by activating a subset of muscle fibers within a bundle, or fascicle of the muscle. Inside each fascicle, each muscle fiber is encased in a thin connective tissue layer of collagen and reticular fibers called the endomysium. The endomysium contains the extracellular fluid and nutrients to support the muscle fiber. These nutrients are supplied via blood to the muscle tissue.

Myofibrils

Is a bundle of myofilaments that contracts. To reach the myofibrils, some of which are located deep in the muscle fibre, the muscular action potential travels through the T-tubule system (the "T" stands for "transverse"), which starts in the sarcolemma and penetrates into the heart of the fibre.

Adductor longus

Is a hip abductor muscle located in the inner thigh. This muscle controls the thigh bone's ability to move inward and from side to side. The muscle originates in the superior aspect of the pubis, below the pubic tubercle. It inserts at the middle third of the linea aspera of the femur along the medial lip. It adducts and flexes the thigh at the hip. It also contributes to lateral and medial rotation of the thigh. All adductor muscles in the thighs pull the legs toward the middle when walking, in order to maintain balance. The adductor longus, adductor magnus, and adductor brevis are the three most powerful muscles of the thigh.

Supinator

It is a broad, cylindrical-shaped muscle in the forearm that normally curves around the upper third of the radius. As the name suggests, the muscle causes supination, which describes movement at an ankle, foot, or a shoulder joint. Previously, "supinator longus" referred to the brachioradialis, a muscle of the forearm, and the term "supinator radii brevis" was given to this extensive muscle. The tricep extensor is an antagonist to this muscle.The primary role of the muscle is to supinate the upper arm, meaning turning the hand in such a position so that the palm points in the upward direction. In this way, the biceps brachii, simply called biceps, is able to perform movements. This is, however, possible due to its ability to rotate the radius. Coordination of these two groups of muscle aids in the rotation of the forearm and flexing of the elbow.

Sarcolemma

Plasma membrane of the muscle fiber. If enough of these sodium ions enter the muscle fibre to raise it from its resting potential of -95 mV to about -50 mV, they trigger a muscular action potential that spreads throughout the fibre. This potential travels first along the surface of the sarcolemma, the excitable membrane surrounding the various contractile cylindrical structures known as myofibrils

Rhomboideus minor

Small area of posteromedial border of scapula at level of spine, below levator scapulae Insertion: Vertebral border of the scapula, adjacent to the scapular spine. Action: Retraction of the scapula, downwar rotation of the scapula

Erector spinae group

The erector spinae are three different muscles that run along the spine from the head to the pelvis. They are extensor muscles that work to straighten the spine and maintain its erect posture. In yoga a perfect example of the erector spinae at work is coming up to stand from a flat back posture with the hands on the hips - Iliocostalis - Longissimus - Spinalis

Internal intercostals

The internal intercostal muscles are responsible for forced exhalation. They depress the ribs and decrease space in the chest cavity. They originate from ribs two through 12, with insertion from ribs one to 11. The innermost intercostal muscles are the deepest of the intercostal muscles. They are separated from the internal intercostal muscles by a grouping of nerves and blood vessels known as the nuerovascular bundle.

Sacromere

The is the functional contractile unit in a skeletal muscle fiber Region between 2 adjacent Z discs Each myofibril contains multiple and repeating sacromeres. A nerve impulse travels from neuromuscular junction, along sarcolemma, down T-tubules, stimulates calcium release from sarcoplasmic reticulum, which allows the thin filaments to slide to the center of the sarcomere, causing it to shorten and the muscle to contract.

Subscapularis

The largest and strongest muscle in this group is the subscapularis muscle. This triangle shaped muscle begins in the scapula, located on the underside of the shoulder blade, and extends up to the humerus, located on the front of the upper arm. The function of the muscle is to stabilize and rotate the shoulder joint to allow the arm to turn inward. When the arm is extended, it draws the humerus forward and downward. It also prevents the dislocation of the head of the humerus. The major arteries that run through the subscapularis muscle are the cervical artery and the subscapular artery.

Motor neuron

The long processes of neurones are called "axons". As the axon of a motor neurone enters the structure of skeletal muscle it forms many branches called "axon terminals". There is a bulbous swelling called a "synaptic end bulb" at the extreme/end of each axon terminal. Each synaptic end bulb contains many synaptic vesicles, each of which contains an important chemical neurotransmitter called "acetylcholine", which is often abbreviated to simply "ACh". . A motor unit is thus the smallest contractile element that the nervous system can activate.

Occipitalis

The occipital belly of epicranius muscle (also known as the occipitalis muscle) helps extend the scalp so that the eyebrows can come up and the forehead may wrinkle. This, along with the frontalis muscle is one of two parts, or bellies, of the epicranius

Serratus posterior (inferior)

The serratus posterior inferior muscle is thin but becomes more muscular at its lowest points. It is supplied with blood by the lowest posterior intercostal artery, the subcostal artery, and the first two lumbar arteries. The nerves in this muscle come from the ventral primary rami. The serratus posterior inferior muscle is a respiratory muscle. The function of the serratus posterior inferior muscle is to pull down the lower ribs, assisting with forced exhaling.

Rotator Cuff Muscles

There are four muscle tendons that connect to the shoulder that make up the rotator cuff. Together these four tendons stabilize the upper arm bone to the shoulder socket and allow the wide range of motion in the shoulder

Extensor carpi ulnaris

This muscle allows the wrist, or carpus, to extend and bend. It begins on the outer side of the elbow on the lateral epicondyle of the humerus and crosses the forearm downward. It inserts at the base of the 'pinky finger', or the fifth metacarpal. The muscle is supplied with blood by the ulnar artery and innervated by the deep branch of the radial nerve. The extensor carpi ulnaris muscle works in conjunction with the flexor carpi ulnaris muscle during the adduction of the wrist, meaning when the wrist bends toward the body's midline. However, the extensor carpi ulnaris muscle is the only muscle responsible for ulnar deviation. This refers to the movement of the hand sideways in the direction of the pinky

Nucleus

Vertebrate skeletal muscle fibers contain hundreds of nuclei, of which three to six are functionally specialized and stably anchored beneath the postsynaptic membrane at the neuromuscular junction (NMJ). The mechanisms that localize synaptic nuclei and the roles they play in neuromuscular development are unknown.

Orbicularis oris

controls movements of the mouth and lips. Specifically, it encircles the mouth, originating in the maxilla (upper jaw and palate) and mandible (lower jaw) bones. The muscle inserts directly into the lips. In common language, the orbicularis oris is often referred to as "the kissing muscle." It allows for facial expression, and more specifically, it is responsible for puckering the lips

Adductor magnus

creates the shape of a large triangle. As an adductor, it contracts and pulls the hip towards the body's midline. This action is a fundamental part of walking, sprinting, and a variety of other bipedal motions. The muscle also extends the hip. While an adductor, the muscle is often considered to be part of the hamstring group as well. The muscle originates in the pelvic region; specifically, it arises from the pubis and the tuberosity of the ischium, which are also known as the sitz or sitting bones. Then, the muscle inserts into several parts of the femur bone.

Sternocleidomastoid

flexes the neck and helps with movement of the head. Also, the muscle works with the scalene muscles in the neck during forced inspiration while breathing (inhaling), and it raises the sternum, the bone at the front of the rib cage. The muscle originates at the central portion of the collarbone. It inserts into the temporal bone's mastoid process near the ear and the base of the skull, and it stretches the entire length of the neck.

Transversus abdominis

function and its role in helping with back pain. The transverse abdominis, referred to as the corset in pilates, is the deepest of them from the belly button up to the rib cage. Below the rib cage.The transverse abdominis wraps horizontally from the back of the body to the front. There is one transverse muscle on each side joined by a fascial sheet that connects them and allows them to act as one solid muscle. The transverse abdominis function is to maintain tone of the abdominal organs; when one side works it bends and rotates the body to the side. And whenever we employ deep breathing, for sports or what have you, the transverse abdominis muscle gets involved. Throwing up, coughing, defecating, labor and also forced exhalation— like playing a wind instrument, blowing up balloons or moving heavy objects all bring the transverse abdominis function into play

Risorius

is a large facial muscle. This muscle is located on the sides of the mouth and is primarily responsible for creating facial expressions. The risorius begins around the parotid gland, a salivary gland in the back of the jaw, and wraps around the platysma muscle. It works with other facial muscles to create a whole facial motion that pulls the lips and face back.

Psoas major

is a lengthy fusiform (or 'spindle-shaped') muscle that can be found on the side of the lumbar region of the vertebral column. It is also adjacent to the brim of the lesser pelvis area. It connects the iliacus muscle to the iliopsosas. In some individuals, the muscle is assisted by the psoas minor. The psoas major assists with the flexion and external rotation of the hip joint. It is also considered part of the group of muscles that are known as the hip flexors. If this muscle tightens, the action may result in lower back pain.

Levator scapulae

is a long muscle of the shoulder girdle. It originates at the transverse processes of the atlas and axis as well as the posterior tubercles of the 3rd-4th cervical vertebrae. It inserts at the superior angle and medial border of the scapula. The upper part of this muscle lies under the splenius capitis and sternocleidomastoideus muscles, and its' lower part under the trapezius. he main function of the levator scapulae is the elevation of the scapula. Thereby it simultaneously pulls the entire scapula medially. This movement is helpful when bringing the elevated arm back to the neutral position. In addition, the muscle also moves the inferior angle away from the back causing a small upward tilt of the scapula

Sternohyoid

is a long, thin muscle located along the entire length of the front of the neck. This muscle is connected by tendons — strong, flexible tissue that usually connects muscle to bone — to the hyoid bone at its top end, and connected to the sternum at its lower end. The hyoid is a bone near the top of the throat. The sternum is the bone at the front of the rib cage. Due to its location, the sternohyoid is useful for several functions, including depression (lowering) of the hyoid bone, head and neck movement, and speech

Triceps brachii

is a major muscle of the upper arm in the human body. The triceps run along the humerus (the main bone of the upper arm) between the shoulder and the elbow. Along with the biceps, it enables extension and retraction of the forearm. When the triceps are contracted, the forearm extends and the elbow straightens; if the triceps are relaxed and the biceps flexed, the forearm retracts and the elbow bends. The triceps also serve to stabilize the shoulder joint at the top of the humerus. The shoulder has the greatest range of motion of any joint in the body, possessing the ability to turn and rotate in many directions. However, this movability means that the shoulder is a relatively unstable joint, and the triceps plays an important role in stabilizing it.

Peroneus longus or Fibularis longus

is a muscle inside the outer area of the human leg, which everts (bends in an outward direction) and flexes the ankle. The muscle is attached to the head of the fibula and is controlled by the fibular nerve. It runs the length of the fibula and eventually turns into a tendon at the lateral malleolus (the bony projection at the outer edge of the ankle). It stretches to the underside of the foot and attaches to the first metatarsal and the medial cuneiform bones. The fibularis longus works in conjunction with the tendons of the peroneal retinaculum to help to stabilize the leg on top of the foot. Blood flow to this muscle is provided by the fibular artery.

Gastrocnemius

is a muscle located on the back portion of the lower leg, being one of the two major muscles that make up the calf. The gastrocnemius branches at the top behind the knee; the two branches are known as the medial and lateral heads. The flexing of this muscle during walking and bending of the knee creates traction on the femur, pulling it toward the tibia in the lower leg and causing the knee to bend. Both the gastrocnemius muscle and the soleus join onto the Achilles tendon, which is the strongest and thickest tendon in the human body

Zygomaticus

is a muscle of the human body. It is a muscle of facial expression which draws the angle of the mouth superiorly and posteriorly to allow one to smile

Abductor digiti minimi

is a muscle that shares its central margin with the lateral plantar nerves and vessels. The muscle begins at the calcaneal tuberosity (the back part of heel bone) and the plantar aponeurosis (the thick, connective tissue that runs along the sole of the foot). This muscle controls the movement of the metatarsophalangeal joint located between the base of the little toe and the head of the fifth metatarsal bone. It is what allows the little toe to flex and move. In rare cases of polydactyly, a condition where a person has extra digits, the muscle connects to the sixth toe.

Mentalis

is a paired muscle located at the lower end of the chin, which acts as the primary muscle of the lower lip. This muscle originates from the mandible (lower jaw), and provides stability to the lower lip to allow it to pout. It causes protrusion of the lower lip and elevates the skin of the chin. As the lower lip is raised, it results in elevation and wrinkling of the chin's skin. The mentalis is so named because of its association with emotional and thoughtful facial expressions.

Vastus medialis

is a part of the quadriceps muscle group, located on the front of the thigh. It is the most medial, or inner, of the quadriceps muscles. It extends the entire length of the thigh. The portion of the muscle that is just above the knee is sometimes referred to as the vastus medialis obliquus, or VMO. This muscle is used to extend the leg at the knee and to stabilize the patella, which is also known as the kneecap.

Tibialis posterior

is a relatively small muscle located within the back side of the calf. It is also the most centrally located muscle in the leg, arising from the inner borders of the fibula and tibia on the posterior (rear) side. The muscle's tendon runs down behind the medial malleolus (bony protrusion on the inside of the ankle) and ends by segregating into the main, plantar, and recurrent portions. The primary function of this muscle is to provide stability to the lower leg. It also facilitates foot inversion (swiveling inward) and aids the ankle's plantar flexion (flexing the foot or toes downward). Additionally, the muscle performs a key role in providing support to the foot's medial arch

Supraspinatus

is a rotator cuff muscle located in the shoulder, specifically in the supraspinatus fossa, a concave depression in the rear portion of the scapula, or shoulder blade. It stretches horizontally to the scapula's spine (elevated ridge), allowing it to pass under the acromial process, a bony structure at the top edge of the scapula. The muscle is attached to a flat, strong tendon that is connected to the shoulder joint capsule. Along with the deltoid and pectoralis major muscles, the supraspinatus muscle helps initiate horizontal abduction (raising the arms skyward) of the shoulder.

Peroneus brevis or Fibularis brevis

is a short, peroneal muscle that lies just underneath the peroneus longus muscle. The peroneal muscles extend along the outer portion of the lower leg and foot. The peroneus brevis attaches to the lower two-thirds of the fibula bone and the fifth metatarsal bone of the foot. The peroneus brevis plays an important role in the motor functions of the foot. The muscle assists in the flexion that moves the ball of the foot away from the body. The muscle also assists with the eversion (turning outward) of the inner portion of the foot. Each of these movements helps keep the body balanced when walking on uneven surfaces

Teres minor

is a slim, narrow muscle within the rotator cuff, located in the shoulder. It is involved in the external rotation of the shoulder joint. The other muscles composing the rotator cuff are the supraspinatus, infraspinatus, and subscapularis. It connects the scapula to the humerus, along with the teres major and infraspinatus muscles, which lie on either side and overlap the teres minor. Along with the infraspinatus, the muscle keeps the head of the humerus in place where it joins with the scapula. It is possible for the two muscles to be interconnected by a few fibers

Iliacus

is found in the lower portion of the trunk, covered in a thick fascia (connective tissue). This muscle is shaped like a triangle, flat, and an exact fit of the iliac fossa — the curved surface of the largest pelvic bone. Together with the psoas major muscle, it is also called the iliopsoas muscle. The iliacus is part of the hip rotator muscles, which are responsible for the flexing of the thigh on the pelvis and the forward tilting of the pelvis. It is also one of the key muscles that helps to maintain proper body posture.

Vastus intermedius

is located along the upper portion of the femur, which is also known as the thighbone. This muscle covers the front part of the femur and the side of the femur. It is directly underneath and ends at the rectus femoris muscle, which is part of the quadriceps cluster of muscles. The muscle is closely related to the vastus medialis muscle and may look attached to that muscle. When the rectus femoris flexes, a small area is visible between the two muscles. The two muscles move in a contiguous line, but each is a separate muscle. It is hard to stretch the muscle because of its location in the quadriceps; hip extension exercises are ineffective and massage therapy cannot reach the muscle

Rhomboideus major

is located in the back region and helps keep the scapula, or shoulder blade, attached to the ribcage. It also rotates the scapula and retracts it towards the spinal column. It has origination points in the second, third, fourth, and fifth thoracic vertebrae (T2 though T5). The rhomboid major muscle receives oxygenated blood from the dorsal scapular artery, which arises from the subclavian artery. The dorsal scapular nerve provides innervation and a connection to the spinal column

Gluteus maximus

is located in the buttocks and is regarded as one of the strongest muscles in the human body. It is connected to the coccyx, or tailbone, as well as other surrounding bones. The gluteus maximus muscle is responsible for movement of the hip and thigh. Standing up from a sitting position, climbing stairs, and staying in an erect position are all aided by the gluteus maximus.

Flexor digitorum brevis

is located in the foot. Its precise location is within the sole of the foot, directly above the plantar aponeurosis, which supports the arch of the foot. It goes deep into the foot and only a very thin layer of fascia (connective tissue) divides it from the lateral plantar vessels. The flexor digitorum brevis muscle originates in the calcaneus (heel bone) and the plantar fascia (the fascia in the sole of the foot). It then inserts into the middle phalanges, which are the middle bones of the second through fifth toes. This muscle enables the four lateral (outer) toes to be flexed. As the flexor digitorum brevis muscle moves forward, it divides into four separate tendons, so that each of the four lateral toes has its tendon. These tendons each divide at the base of the first phalanges, which are the backmost bones of the toes, in order to allow the tendon of the flexor digitorum longus to pass through

Brachioradialis

is located in the forearm. It enables flexion of the elbow joint. The muscle also assists with pronation and supination of the forearm. These two movements allow the forearm and hand to turn so that the palm faces up or down. The arms are the only part of the body with this ability. The muscle originates on the lateral supracondylar ridge of the humerus. This rough margin is located on the lower end of the humerus. From there, the brachioradialis travels the length of the forearm

Rectus abdominis

is located in the front of the body, beginning at the pubic bone and ending at the sternum. It is located inside the abdominal region. The muscle is activated while doing crunches because it pulls the ribs and the pelvis in and curves the back. The muscles are also used when a child is delivered, during bowel movements, and coughing. Breathing in and holding the rectus abdominis in pulls in the abdomen. When this muscle is exercised and layers of fat disappear from the abdomen, the exposed rectus abdominis muscle creates the look of a "six pack." Strengthening the muscle also improves performance in sports that require jumping.

Deltoid

is located on the outer aspect of the shoulder and is recognized by its triangular shape. The deltoid muscle is constructed with three main sets of fibers: anterior, middle, and posterior. These fibers are connected by a very thick tendon and are anchored into a V-shaped channel. This channel housed in the shaft of the humerus bone in the arm. The deltoid muscle is responsible for the brunt of all arm rotation and allows a person to keep carried objects at a safer distance from the body. It is also tasked with stopping dislocation and injury to the humerus when carrying heavy loads.

Vastus lateralis

is located on the side of the thigh. This muscle is the largest of the quadriceps group (often called quads) which also includes the rectus femoris, the vastus intermedius, and the vastus medialis. Collectively, the quadriceps muscle is the largest in the human body and its purpose is to extend the knee. The specific task of the vastus lateralis muscle is to extend the lower leg and allow the body to rise up from a squatting position. On the upper end, the muscle attaches to the femur; on the lower end it attaches to the patella, or kneecap. Taken together, the muscles of the legs allow strength and stability. They provide power for and absorb the impact of daily activities such as walking, running, and jumping.

Palmaris longus

is one of five muscles that act at the wrist joint. The palmaris longus muscle is a long muscle that runs to the palm and activates flexibility at the wrist. Muscles assist in movement, blood flow, speech, heat production, body shaping, and protection of some internal organs

Temporalis

is one of several chewing muscles that is necessary for crushing and grinding objects between the molars. Due to its location and frequent use, this muscle may be a primary focal point for a recurring condition known as "tension headaches." The temporal muscle is broad, fan-shaped, and situated along the side of the head, occupying a depression in the skull called the temporal fossa

Splenius Capitis

is one of the deep (or intrinsic) muscles of the back. It is a broad straplike muscle in the back of the neck. Deep to Sternocleidomastoid at the mastoid process. It also assists in supporting the head in the erect position

Infraspinatus

is one of the four muscles that comprise the rotator cuff. The other muscles are the supraspinatus, teres minor, and subscapularis. It is a triangular shoulder muscle that rises above and is attached to the infraspinatous fossa, which is more commonly known as the shoulder blade. This muscle aids in the lateral motion and horizontal extension of the arm as well as overall joint stability. This thin shoulder muscle is attached to the suprascapular nerve and is therefore associated with the fifth and sixth cervical vertebrae.

Extensor digitorum (communis)

is one of the key muscles on the backside of the forearm. The extensor digitorum muscle helps in the movements of the wrists and the elbows. It also provides extension for fingers 2 through 5, as well as for the hand and wrist. The muscle originates from the lateral epicondyle, and then sub-divides down into four separate tendons. The chief function of the EDC is extension of the digits, but it also abducts the digits as it extends. This action centers on the middle finger, which does not deviate radially or ulnarly upon extension.

Latissimus dorsi

is one of the largest muscles in the back. There muscle is divided into two segments, which are configured symmetrically along the backbone. The muscle is located in the middle of the back, and it is partially covered by the trapezius. The muscle also covers the lower tip of the scapula, or shoulder blade. When flexed, the muscle works at extending, adducting and rotating the arm. Once aggravated, the latissimus dorsi muscle is often the source of chronic shoulder and neck pain, and it can cause tendonitis of the shoulder joint.

External oblique

is one of the largest parts of the trunk area. Each side of the body has an external oblique muscle. The external oblique muscle is one of the outermost abdominal muscles, extending from the lower half of the ribs around and down to the pelvis. Its lowest part connects to the the top corner of the pelvis (called the crest of the ilium), the bottom-front of the pelvis (the pubis)

Gracilis

is one of the muscles found in the groin. It starts at the external point of the ischiopubic ramus (on the pubic bone) and extends down to the upper medial (middle) shaft of the tibia, or shinbone. The gracilis is responsible for hip adduction and assists knee flexion. Adduction means the body part is moved from the outside toward the center of the body. In this case, it is bringing both legs together or across the body. This muscle also assists in stabilizing and rotating the knee inward.

Orbicularis oculi

is one of the two major components that form the core of the eyelid, the other being the tarsal plate. The orbicularis oculi muscle is composed of skeletal muscle fibers, and receives nerves from the facial nerve. It is an important muscle in facial expression. The orbicularis oculi muscle lies directly underneath the surface the skin, around the eyes. Its function is to close the eyelid, and to help in the passing and draining of tears through the punctum, canaliculi, and lacrimal sac, all parts of the tear drainage systm

Auricularis superior

is one of three extrinsic muscles of the ear. It is a thin, fan-shaped muscle that arises from the temporal fascia (connective tissue along the side of the head) and descends into the root of the auricle, or ear. The other muscles in this region include the auricularis posterior and the auricularis anterior. The Latin term pinna is another word for auricula or auricle, which refers to the externally visible, cartilaginous structure of the external ear (the part we usually refer to as the ear). The primary action of the auricularis superior is to draw the auricula of the ear upward and backward.

Gluteus medius

is partially covered, on its lower-third part, by the gluteus maximus muscle. This makes up what is commonly referred to as the buttocks. The gluteus medius works to provide rotation of the thigh outward from the center of the body, which enables a steady walking gait. The gluteus medius attaches to the leg at the top of the femur (thigh bone), close to the hip joint, on a bony prominence called the greater trochanter.

Tibialis anterior

is the largest muscle located in the anterior (front) compartment of the leg. The blood supply to the tibialis anterior muscle comes primarily from the anterior tibial artery and its branches. In general, muscles of this compartment help to flex the foot in an upward direction at the ankle and also extend the toes. The tibialis anterior muscle helps with dorsiflexion, which is the action of pulling the foot toward the shin. It also inverts (tilts inward) the foot at the subtalar and midtarsal joints and holds up the medial longitudinal arch of the foot

Longissimus thoracis

is the longest continuation of the sacrospinalis and lies intermediate to it. It begins at the sacrum and the spinous process (bony projections at the back of each vertebra) of the lumbar spine, where a part of its fibers connect with the entire length of the back side of the lumbar vertebrae and the front surface of the lumbodorsal fascia, a sheath of connective fibers that covers the sacrospinalis muscle group.

Buccinator

is the major facial muscle underlying the cheek. It holds the cheek to the teeth and assists with chewing. The buccinator muscle is served by the buccal branch of cranial nerve VII, also known as the facial nerve. The buccinator is one of the first muscles that a human can control; the sucking reflex of a baby depends on it. Smiling, chewing, and whistling are all dependent upon it, and speech would be difficult and slurred without its proper function

Soleus

is the plantar flexor muscle of the ankle. It is capable of exerting powerful forces onto the ankle joint. It is located on the back of the lower leg and originates at the posterior (rear) aspect of the fibular head and the medial border of the tibial shaft. The soleus muscle is primarily used for pushing off the ground while walking. It may be exercised through calf raises while standing up or sitting down. The soleus is vital to everyday activities such as dancing, running, and walking. The soleus muscle helps to maintain posture by preventing the body from falling forward.

Diaphragm

is the primary muscle used in the process of inspiration, or inhalation. It is a dome-shaped sheet of muscle that is inserted into the lower ribs. Lying at the base of the thorax (chest), it separates the abdominal cavity from the thoracic cavity. It is a thin, skeletal muscle that can contract voluntarily. During contraction, the diaphragm pushes downward and pulls the pleura, a serous membrane surrounding the lungs, with it. This action causes the pleural pressure and the alveolar pressure to drop, which in turn, facilitates air to flow into the lungs.

Levator labii superioris

is used when a person makes facial expressions. It is shaped like a broad, flat sheet that starts next to the nose and extends to the zygomatic bone. This muscle arises from the top portion of the upper jaw's frontal process and passes in a downward direction, dividing into two lateral slips. One of the slips goes into the skin and cartilage of the nose. The other slip blends into the orbicularis oris (a muscle that encircles the mouth) and infraorbital head (located below the eye socket) after extending into the top of the lip. In addition to making general facial expressions, the levator labii superioris muscle is primarily responsible for elevating the upper lip.

Pectoralis minor

lies beneath the pectoralis major. The pectorals are predominantly used to control the movement of the arm, with the contractions of the pectoralis major pulling on the humerus to create lateral, vertical, or rotational motion. The pectorals also play a part in deep inhalation, pulling the ribcage to create room for the lungs to expand. Six separate sets of muscle fiber have been identified within the pectoralis major muscle, allowing portions of the muscle to be moved independently by the nervous system.

Brachialis

located in the upper arm. It lies underneath the biceps muscle. It acts as a structural bridge between the humerus, which is the bone of the upper arm, and the ulna, which is one of the forearm bones. The muscle is innervated by both the musculoskeletal nerve and the radial nerve. In some people, the muscle may appear doubled. Also called the brachialis anticus, its primary action is to flex the forearm muscles at the elbow. Due to its high contractile strength, the branchialis makes many arm and elbow movements possible.

Coracobrachialis

long, thin muscle that acts exclusively on the shoulder joint. Its main functions are to draw the arm forward and to pull the arm toward the midline of the body. The muscle originates from the coracoid process, a small part of the scapula. It inserts midway along the inside of the humerus, a long bone in the upper arm. The muscle's insertion at the humerus lies between the attachments of two other arm muscles, the triceps and brachialis. Another key role of this muscle is to help stabilize the head of the humerus inside the shoulder joint. The muscle is innervated by the musculocutaneous nerve.

Extensor carpi radialis brevis

muscle aids in moving the hand. Specifically, it abducts and extends the hand at the wrist joint. The muscle works in concert with the extensor carpi radialis longus, which is situated nearby. However, the extensor carpi radialis brevis is much shorter and thicker than its longus counterpart. The muscle originates along the lateral supracondylar ridge, which is a narrow, raised region of the humerus. It inserts into the third metacarpal of the hand. Within the palm this is the bone connected to the phalanges of the index finger. The radial artery delivers oxygenated blood to the muscle. It is innervated by the radial nerve

Pectoralis major

muscle is a large muscle in the upper chest, fanning across the chest from the shoulder to the breastbone. The two pectoralis major muscles, commonly referred to as the "pecs," are the muscles that create the bulk of the chest. A developed pectoralis major is most evident in males, as the breasts of a female typically hide the pectoral muscles

Quadratus lumborum

muscle is a muscle of the posterior abdominal wall lying deep inside the abdomen and dorsal to the iliopsoas. In order to palpate the muscle one needs place the fingers above the posterior iliac crest at the level of the hip. Starting from the iliac crest of the ilium and from there it runs craniomedially, and attaches to the 12th rib and the transverse processes of the 1st to 4th lumbar vertebrae. the quadratus lumborum contributes to the stabilization and movement of the spine and the pelvis. A bilateral contraction leads to an extension of the lumbar vertebral column. When the muscle is only activated on one side, the trunk is bent towards that direction (lateral flexion). In addition, the muscle fixes the 12th rib during movements of the thoracic cage and this way supports expiration (accessory muscle of expiration).

Flexor carpi radialis

muscle is a relatively thin muscle located on the anterior part of the forearm. It arises in the humerus epicondyle, close to the wrist area. It is a superficial muscle that becomes very visible as the wrist comes into flexion. The muscle travels on the outside of the flexor digitorum superficialis. It inserts at the base of the index finger. The innervation of this muscle is provided by the median nerve and it receives its blood supply through the radial artery. It performs the function of providing flexion of the wrist and assists in abduction of the hand and wrist.

Extensor digitorum longus

muscle is located at the front of the leg and is adjacent to the peroneus brevis muscle and the tibialis anterior muscle. This wing-shaped muscle works to extend the foot at the ankle, along with the four smallest toes. The upper two-thirds to three-fourths of the muscle extends over the fibula and the muscle passes below the cruciate crural and transverse ligaments. After passing these ligaments, the muscle divides to provide motor function to the toes and is joined to the second, third, and fourth toe by tendons from the extensor digitorum brevis.

Auricularis anterior

muscle is located between the ear and the eye. It is in an area with few other points of insertion or origination, which is unusual for regions on the face. The auricularis anterior arises from the temporal fascia (a fibrous tissue that covers the temporalis muscles on the sides of the head) and it inserts into the major helix, which is the upper rim portion of the ear. This point is closer to where the ear connects to the head, and this muscle works to pull the ear forward.

Extensor pollicis brevis

muscle is located on the dorsal side of the forearm. It originates from the trapezium and the flexor retinaculum. It is connected with the extensor pollicis longus to make up the interosseous membrane. It inserts at the base of the proximal phalanx of the thumb. This muscle also forms the radial side of the anatomical snuff box at the wrist. Working with the extensor pollicis longus, this muscle allows the thumb, wrist, and fingers to straighten and bend

Flexor digitorum longus

muscle is located on the inner side of the leg by the tibia. There are two bones in the lower leg: the tibia and fibula. The tibia is located on the inner part of the leg and is the larger of the two bones; it may also be referred to as the shinbone. This muscle is thin where it begins, but the size gradually increases as it descends to the end. The origin of the muscle begins at the tibia and extends to the sole of the foot through the ankle joint while splitting into four tendons. The flexor digitorum longus muscle is responsible for the movement and curling of the second, third, fourth and fifth toes. This muscle makes it possible for the toes to grip the surface of floors, which is important when it comes to maintaining postural balance on surfaces that are rough or uneven.

Frontalis

muscle is thin, of a quadrilateral form, and intimately adherent to the superficial fascia. It is broader than the occipitalis and its fibers are longer and paler in color. It is located on the front of the head. The muscle has no bony attachments. The frontal belly of epicranius muscle (also known as the frontalis muscle), with assistance from the occipital belly, pulls the scalp back so that the eyebrows are lifted and the forehead can wrinkle.

Flexor hallucis longus

muscle lies within the sole of the foot. The muscle connects to the bottom of the cuboid bone (located in the middle of the foot) and extends across the sole to the base of the hallux bone, better known as the big toe. The muscle plays a dual role in both movement of the big toe and the arching of the foot. The hallucis brevis is one of several muscles located along the sole of the foot that are responsible for the flexing or curling of the toes. It works opposite of the extensor hallucis longus muscle located on the top of the foot, with the two muscles pulling on the hallux bone to create the motions of the big toe.

Serratus anterior

muscle that originates on the top surface of the eight or nine upper ribs. The serratus anterior muscle inserts exactly at the front border of the scapula, or shoulder blade. The muscle has three sections: the superior, intermediate or medial, and the inferior. The function of the serratus anterior muscle is to allow the forward rotation of the arm and to pull the scapula forward and around the rib cage. The scapula is able to move laterally due to the serratus anterior muscle, which is vital for the elevation of the arm. The serratus anterior muscle also allows the upward rotation of the arm, which allows a person to lift items over their head

Trapezius

one of the major muscles of the back and is responsible for moving, rotating, and stabilizing the scapula (shoulder blade) and extending the head at the neck. It is a wide, flat, superficial muscle that covers most of the upper back and the posterior of the neck. Like most other muscles, there are two trapezius muscles - a left and a right trapezius - that are symmetrical and meet at the vertebral column.

Teres major

one of the six muscles within the scapulohumeral muscle group. The muscle is located on the underside of the upper arm, in the area between the shoulder and elbow. It has a flat shape and is supplied with nerves from the lower subscapular nerve. The arteries supply blood and oxygen to the muscle. The teres major starts just below the armpit and stops at the top of the humerus, the large bone of the upper arm. It is considered a medial rotator and helps control certain movements of the humerus. The muscle helps the latissimus dorsi in moving the humerus back and down when extended, and also stabilizes the upper portion, or head, of the humerus.

Sartorius

pans the distance of the thigh. It originates at anterior superior iliac spine (a bony projection on the uppermost part of the pelvis) and travels to the upper shaft of the tibia, or shinbone. As such, the sartorius is the longest muscle in the human body. The muscle helps flex, adduct, and rotate the hip. In addition, it helps with the knee's flexion. The femoral artery supplies oxygen-rich blood to the muscle. It is innervated by the femoral nerve as well as the intermediate cutaneous nerve of the thigh.

Extensor digiti minimi

refers to a muscle located in the forearm of the human body. It is also known as the extensor digiti quinti proprius. The muscle is connected to the extensor digitorium communis, which controls the muscles in the four fingers of the hand. On the backside of the arm and lower part of the hand is the dorsal radiocarpal ligament. This ligament keeps the muscles and tendons from moving or shifting in the arm and is connected to the digiti minimi. It stops when it reaches the first bone of the pinky finger. The function of the extensor digiti minimi is to control the movement of the little finger. When the muscle moves, it forces the little finger to bend and stretch.

Abductor hallucis

runs along the medial, or interior, border of each foot, covering the origins for most of the plantar (sole of foot) nerves and vessels. The abductor hallucis abducts the big toe (spreads it outward), whereas the adductor hallucis muscle adducts the big toe (moving it in toward to other toes). Both muscles insert into the first phalanx of the big toe. This muscle also plays a vital role in posture and gait by supporting the foot's medial arch

Anconeus

small triangular elbow muscle connecting the medial side of the ulna to the lateral side of the humerus. It functions mainly to allow a person to extend his elbow and rotate the forearm. This action is used to carry something, as a food server would carry a tray. Because of its location and function, many anatomists believe it is more accurately categorized as an extension of the triceps brachii muscle. The anconeus muscle is not considered to be a critical piece of the arm's musculature. However, its absence would make it more difficult to extend the arm. It also functions to prevent the ulna and humerus from pinching the elbow joint capsule when the arm is flexed and released

Biceps brachii

sometimes known simply as the biceps, is a skeletal muscle that is involved in the movement of the elbow and shoulder. It is a double-headed muscle, meaning that it has two points of origin or "heads" in the shoulder area. The short head of each biceps brachii originates at the top of the scapula (at the coracoid process). The long head originates just above the shoulder joint (at the supraglenoid tubercle). Both heads are joined at the elbow. The biceps brachii is a bi-articular muscle, which means that it helps control the motion of two different joints, the shoulder and the elbow. The function of the biceps at the elbow is essential to the function of the forearm in lifting. The function of the biceps brachii at the shoulder is less pronounced, playing minor roles in moving the arms forward, upward, and sideways.

Flexor carpi ulnaris

t arises, along with the other superficial muscles, from the medial epicondyle of the humerus. But the flexor carpi ulnaris muscle has an additional attachment point on the head of the ulna. It inserts at two wrist bones: the pisiform bone and the hook of the hamate. It also inserts at the base of the pinky finger. The flexor carpi ulnaris muscle works in tandem with the extensor carpi ulnaris. These muscles flex the wrist and adduct it (move it laterally in the direction of ulnar).

Tensor fasciae latae

tiny muscle, inferior to the iliotibial band. This band, also called the IT band, is an elongated strip of fascia — a type of connective tissue — located in the thigh and knee. The muscle originates in the ilium (the largest bone in the pelvis) and the front portion of iliac crest (the top, outer part of the ilium). It goes into the lateral condyle of the tibia (the outer side of the top of the tibia, or shinbone) through the iliotibial band. It performs the functions of hip flexion and abduction. These actions help to maintain one foot ahead of the other, as occurs in walking. It also provides lateral (side-to-side) stability to the knee. The muscle performs the role of a supplement ligament, and works with the minimus, medius, and upper maximum fibers. The tensor fasciae latae also helps to stabilize the pelvis on the top of the femur (thigh) bone when a person is standing up straight