First are some muscles of the head, face, and the neck. We'll begin with the masseter muscle. The origin of the masseter is on the zygomatic arch and on the maxilla. The insertion of the masseter muscle is on the angle and ramus of the mandible. And it's action is to elevate the mandible or close the mouth. Cadaver, and the head to the chin, the masseter muscle is located here. It's counterpart on the other side. And again the origin on the zygomatic arch and the maxilla, and the insertion on the angle and ramus of the mandible. It's action to elevate the mandible, ie. close the mouth. The next muscle is the temporalis muscle. Also operating the TMJ joint. And the origin of the temporalis muscle is the temporal fossa, in this region right here. The insertion of the temporalis is the coronoid process of the mandible as well as the ramus of the mandible. It's action is to elevate the mandible and the temporalis also retracts the mandible. Again on the cadaver, the temporalis muscle has it's origin in the temporal fossa, on the temporal bone. The insertion passing underneath the zygomatic arch is on the coronoid process of the mandible and the ramus of the mandible, traveling underneath the masseter muscle. And it's action is to elevate the mandible, close the mouth, as well as retract the mandible. The next muscle is the zygomaticus major. It doesn't really operate a joint, it controls certain functions of the lips. It's origin is the zygomatic bone, right here in this area. And it's insertion is in the soft tissue surrounding the lips as well as partially in the orbicularis oris muscle. And it's action, the most obvious common action is to cause a person to smile. On the cadaver, the zygomaticus major is this muscle right here. It's origin on the zygomatic bone. It's insertion down here, where the orbicularis oris muscle comes around, as well as the soft tissue surrounding the orbicularis oris. And it's action, when it contracts is to pull the corners of the mouth superiorly, and when that happens on both sides, then the person smiles. Next we have the orbicularis oris muscle that surrounds the mouth. The origin is in the fascia surrounding and immediately attached to the maxilla and the mandible. The insertion is the mucosal layer of the lips themselves. And this muscle completely encircles the mouth. The action of this muscle is to close the lips and also produce the motions associated with whistling or kissing. On the cadaver, the orbicularis oris muscle surrounding the lips. The origin is in the fascia immediately attached to the maxilla and mandible themselves. The insertion point is in the mucosal layers surrounding the lips, and the action of the orbicularis oris muscle is to close the lips as well as produce the motions for whistling or kissing. Next we have the orbicularis oculi. Again a circular muscle like the orbicularis oris, it surrounds the eyes in this case. The origin of the orbicularis oculi muscles are the bones of the orbit here and here. The insertion is in the tissues of the eyelets themselves and the action of the orbicularis oculi is to close the eyes. On the cadaver, the orbicularis oculi muscles surround the eyes themselves. Both sides. The origin of the muscles are the bones of the orbital complex themselves. And the insertion is the tissue of the eyelids. And the action of the orbicularis oculi muscle is to close the eyelids. The next muscle is the sternocleidomastoid muscle, which operates the neck. The origin is the sternum and the clavicle. And the insertion point is the mastoid process of the skull, as well as the superior nuchal line. The action of the sternocleidomastoid is two-fold. Working in unison, both will flex the head, flex the neck, and working individually, they can rotate the head from side to side. On the cadaver, the sternocleidomastoid is here, companion on this side. The origin point the sternum. This is also known as the sternal head. And the clavicle, this is the clavicular head. And they come back and the insertion point is on the mastoid process as well as the superior nuchal line. And when they contract in unison, neck flexion occurs. And if they contract individually, head rotation occurs. Last muscle of the head and neck area is the platysma. It operates indirectly to TMJ joint as well as tenses the skin in the neck region. The origin is in the superior thorax between the second and third ribs in the cartilaginous areas extending out to the acromion of the scapula. The insertion is on the mandible and into some of the tissue of the cheek itself. The action of the platysma is to depress the mandible, as well as tense the skin in the neck. On the cadaver, the platysma is on the superior thorax it's origin, down to the first and second ribs underneath the clavicle area, extending out to the acromion, and then continuing up and inserting on the mandible. And a portion inserting in the cheek tissue itself. And the action of the platysma is to depress the mandible, as well as it can tense the skin in the neck region. The next group of muscles are going to be of the upper back, chest and shoulder area, and the joints we're gonna be looking at are the scapula and the shoulder. And we'll begin with the levator scapulae. These muscles have an origin on the cervical vertebrae, one through four. And the insertion point is on the superior medial border of the scapula, which is here and here. And the action of the levator scapulae is simply to elevate the scapula. The next two muscles are the rhomboids. And there are two sets. The rhomboid major and the rhomboid minor. The rhomboid minors are superior to the rhomboid majors. The rhomboid minors, the origin is on cervical vertebra number seven, and on thoracic vertebra number one. The insertion point is on the medial border of the scapula, which is here and here. The rhomboid majors, origin point is thoracic vertebra number two, through vertebra number five. And the insertion point is also on the medial border of the scapula, more inferior to the rhomboid minors. These muscles when they contract, their action is to adduct the scapulae. The next muscle is the supraspinatus. And this operates the shoulder. The origin of the supraspinatus is the supraspinatus fossa of the scapula. The insertion point is the greater tubercle of the humerus. The action of the supraspinatus is abduction of the shoulder. Next we have the infraspinatus muscle, the origin of which is on the infraspinatus fossa of the scapula. The insertion again is on the greater tubercle of the humerus. And the action of the infraspinatus is lateral rotation of the humerus. Next we have a group of muscles the teres. There are two sets, the minor and the major. The teres minor has the origin on the lateral border of the scapula, and the insertion point is on the greater tubercle of the humerus. And the action of the teres minor is lateral rotation of the humerus. Next we have the teres major, which is inferior to the teres minor. The origin of the teres major is the inferior angle of the scapula coming up the lateral border just slightly. This muscle passes medially to insert on the intertubercular groove of the humerus. And thus the action of the teres major is medial rotation of the humerus. Our next muscle is the deltoid. The origin of the deltoid is the clavicle, the spine of the scapula, as well as the acromion. The deltoid muscle comes over the shoulder and inserts on the deltoid tuberosity on the humerus. And the action of the deltoid is abduction of the humerus as well as humeral flexion and humeral extension. On the cadaver, the deltoid muscle is here. This is an anterior aspect of it. The origin and on the clavicle, a portion on the spine of the scapula on the back, as well as on the acromion. The companion deltoid muscle on the other side. And the deltoid runs over the shoulder, and to it's insertion point on the deltoid tuberosity of the humerus, which is underneath these other muscles. The action of the deltoid is abduction of the shoulder, as well as flexion and extension of the shoulder. Next we have the pectoralis major, the big chest muscle everybody is familiar with. This also operates the shoulder. The origin of the pectoralis major is the clavicle, the sternum, and the costal cartilages of ribs two through six. The insertion point is the intertubercular groove or sulcus of the humerus. The action of the pectoralis major is adduction of the humerus, as well as flexion of the humerus and medial rotation of the humerus. On the cadaver, the pectoralis major muscles here, partially reflected. Origin on the clavicles, the sternum and the costal cartilages of ribs two through six. The insertion point the intertubercular groove of the humerus. And the action of the pectoralis major is adduction of the humerus, flexion of the humerus, and medial rotation of the humerus. Underneath the pectoralis major is the pectoralis minor. The origin of the pectoralis minor is the anterior surfaces of ribs three through five. The insertion point is the coracoid process of the scapula. And the action of the pectoralis minor is to depress the scapula. The pectoralis minor are underneath the pectoralis major. And on this side, this is the pectoralis minor. The origin on the anterior surface of ribs three through five. The insertion, the coracoid process of the scapula. And the action of this muscle is to depress the scapula. Our next muscle is the trapezius, which is a large muscle on the superior portion of the back and neck. The origin of the trapezius is the occipital bone, and specifically the superior nuchal line. The other origin is the processes of cervical vertebra number seven and thoracic vertebrae one through 12. The insertion point of the trapezius is the clavicles, the acromion, and the spine of the scapula. The action of the trapezius is to elevate, adduct, and depress the scapula. And the trapezius also functions to extend the head. On the cadaver the trapezius is located here. We have the right shoulder and right arm, the right clavicle. And the right side of the neck in this portion. And this is simply showing the insertion point of the trapezius on the clavicle and we can extend that out to the acromion of the scapula as well. The rest of the insertion points on the spine of the scapula are on the back, the origin points are on the back of the cadaver as well. The next muscle, the serratus anterior. This muscle also operates the scapula. The origin is the anterior surface of ribs one through eight, or one through nine it varies. The insertion is the anterior surface of the medial border of the scapula. In other words the serratus anterior runs between the superficial portion of the ribs and the deep portion of the scapula. Essentially running inside the subscapular fossa. The action of the serratus anterior is to protract the shoulder. On the cadaver, the serratus anterior can be seen between here and here. These extensions coming up, these are the origin points, ribs one through eight or perhaps nine, and then the serratus anterior runs posteriorly to go in between the ribs and the anterior portion of the scapula, the subscapular fossa, to insert on the interior border of the medial border of the scapula. And the action of the serratus anterior is to protract the shoulder. Our last muscle in this group is the latissimus dorsi. It operates the shoulder. The origin of the latissimus dorsi, or the spinous processes of a number of vertebra beginning with T5 in the thoracic area, and going all the way down to L5 in the lumber region. And we also include the thoracal lumber fascia, as well as ribs nine through 12. Here to there. The insertion point is the intertubercular sulcus of the humerus located right here. The action of the latissimus dorsi is to extend, adduct, and medially rotate the humerus. On the cadaver, the latissimus dorsi we can see coming from behind the back, and a good portion of it is right here. From here to here. Coming from it's origins on the spinous processes of vertebrae T5 through L5. The thoracal lumbar fascia as well as ribs nine through 12 and going on to it's insertion point in the intertubercular sulcus of the humerus. Our next group of muscles are going to be those of the upper arm. And we'll begin with the biceps brachii. The biceps brachii operates both the elbow and the shoulder. The origin of the biceps brachii is on the scapula near the glenoid fossa. It also has an origin on the coracoid process of the scapula. The insertion of the biceps brachii is on the radial tuberosity. The function of the biceps brachii is flexion and supination of the forearm, as well as flexion of the humerus. On the cadaver, The biceps brachii is this muscle right here. Again the origin is on the scapula near the glenoid cavity, as well as on the coracoid process of the scapula. The insertion is on the radial tuberosity. It's function is flexion of the humerus, as well as flexion of the elbow and supination of the elbow. Next we have a smaller muscle, the coracobrachialis, which also operates the shoulder. The origin is the coracoid process of the scapula. The insertion is the medial margin of the humerus, and it's action is flexion and adduction of the humerus. On the cadaver, the coracobrachialis muscle is right here. Coming from it's origin on the coracoid process of the scapula, and inserting on the medial margin of the humerus. It's action is flexion of the humerus and adduction of the humerus. Next is the brachialis muscle. The brachialis operates the elbow. The origin of the brachialis is the anterior distal surface of the humerus. It's insertion is the coronoid process of the ulna. And it's action is to flex the elbow. On the cadaver, the brachialis muscle is here. Underneath in this orientation, the biceps brachii. It's origin the distal anterior surface of the humerus. The insertion the coronoid process of the ulna. And it's action is flexion of the elbow. Our next muscle the brachioradialis also operates the elbow. The brachioradialis, the origin is on the lateral distal ridge of the humerus. And it's insertion is the styloid process of the radius. It's action is elbow flexion. On the cadaver, the brachioradialis muscle is seen here and working this way into the forearm, the origin, the distal lateral ridge of the humerus. The insertion, the styloid process of the radius which is now on this side since this is not an anatomical position. The action of the brachioradialis is flexion of the elbow. Our last muscle of the upper arm is the triceps brachii. The origin of the triceps brachii is near the glenoid cavity on the scapula, as well as the posterior and lateral borders of the proximal humerus. The insertion of the triceps brachii is the olecranon, or olecranon process of the ulna. And like the biceps brachii, this muscle operates both the shoulder and the elbow. It's action is to extend the forearm as well as extend the humerus. On the cadaver, the triceps muscle is right here. The origins again near the glenoid cavity, and the posterior and lateral portions of the proximal humerus. The insertion, the olecranon of the ulna. And the actions of the triceps brachii are extension of both the humerus and the elbow. Couple muscles of the lower arm, beginning with the flexor carpi radialis. It operates the wrist. The origin of the flexor carpi radialis is the medial epicondyle of the humerus. The insertion of the flexor carpi radialis is the second and third metacarpal. And the action of the flexor carpi radialis is flexion and abduction of the wrist. Next is the palmaris longus, also operates the wrist. The origin of the palmaris longus is also the medial epicondyle of the humerus. The insertion of the palmaris longus is the palmar aponeurosis, as well as the flexor retinaculum, which is a tough connective tissue that surrounds the wrist. The action of the palmaris longus is flexion of the wrist. Third muscle in the forearm, the flexor capri ulnaris. The origin is the medial epicondyle of the humerus. This muscle also operates the wrist. The insertion is the pisiform and the hamate, as well as the fifth metacarpal. The action of the flexor carpi ulnaris is flexion and adduction of the wrist. And one final muscle of the forearm, the pronator teres. This operates the radioulnar joint. The origin of the pronator teres is the medial epicondyle of the humerus, as well as the coronoid process of the ulna. And the insertion is the midlateral portion of the radius. The action of the pronator teres is pronation of the forearm. On the cadaver, the pronator teres is this muscle here. The origin on the medial epicondyle of the humerus and the coronoid process of the ulna. And the insertion on the lateral aspect of the radius. And the action of the pronator teres is pronation of the forearm. Our next group of muscles are of the chest and abdomen, the thoracic area and the abdominal area. We'll begin with the intercostal muscles. There are two sets, the external and the internal intercostals. The external intercostals, their origin is the inferior border of the superior rib. And the insertion is the superior border of the inferior rib. Basically they run from the top down. And they run at an angle pointing toward the midline, running medially. The action of the external intercostals is to elevate the ribs. On the cadaver, one set of external intercostals are shown here and here. And their orientation is running medially. Their origin from the inferior border of the rib above, to the superior border of the rib below, above to below. The action is to elevate the ribs. The internal intercostal muscles, their origin is the superior border of the inferior rib. The insertion is the inferior border of the superior rib. And they run at an angle medially this way, heading up. Their action is to depress the ribs. On the cadaver, the internal intercostal muscles here and here, show their origin the superior border of the rib below. The insertion, the inferior border of the rib above. And their fibers are running medially in a superior direction. The action of the internal intercostals is to depress the ribs. The diaphragm is the large muscle that separates the thoracic and abdominal cavities. The origin of the diaphragm is the xyphoid process, the costal cartilages of ribs four through 10, and the interior surfaces of the lumbar vertebrae. The insertion of the diaphragm is the central tendon in the anterior abdominal wall. The action of the diaphragm is to increase the vertical dimension of the thorax. It's the primary muscle used for inhalation and exhalation. Our next group of muscles are the abdominal muscles, beginning with the rectus abdominis, the most superficial of the four. The origin of the rectus abdominis is the pubic crest. And the insertion of the rectus abdominis is the xyphoid process and the costal cartilages of ribs five through seven. The action of the rectus abdominis is flexion of the spine, as well as compression of the abdomen. On the cadaver, the rectus abdominis muscles are here and here, separated in the center by the linea alba. The origin, the pubic crest. The insertion, the xyphoid process and the costal cartilages of ribs five through seven. The action of the rectus abdominis is flexion of the spine and abdominal compression. Muscles are the external abdominal obliques. The origin of these muscles is ribs five through 12. The insertion is the linea alba, between the rectus abdominis muscles, and the iliac crest. Which is here and here. The action of the external obliques is flexion and rotation of the spine, as well as compression of the abdomen. On the cadaver the external abdominal obliques are here and here. Their origin again, ribs five through 12. The insertion is the linea alba underneath the rectus abdominis, as well as the iliac crest. And the action of the external obliques is spinal rotation and flexion, as well as compression of the abdomen. Deep to the external abdominal obliques are the internal abdominal oblique muscles. The origin of these muscles is the iliac crest and the lumbar fascia. The insertion of the internal obliques is the linea alba, the costal cartilages of ribs eight through 10. The action of the internal obliques is flexion and rotation of the spine and compression of the abdomen. On the cadaver, the internal abdominal obliques here and here. The origin, the iliac crest and the linea alba. The insertion is the costal cartilages of ribs eight through 10. The action of the internal obliques is flexion and rotation of the spine and abdominal compression. Our final abdominal muscle is the transverse abdominis. This is the deepest of the four abdominal muscles. The origin of the transverse abdominis is the iliac crest, the lumbar fascia, as well as ribs six through 12. The insertion of the transverse abdominis is the linea alba, as well as the pubic crest. The action of the transverse abdominis muscles is abdominal compression. On the cadaver, the transverse abdominis muscles are located here and here. We have two muscles that originate in the abdominal cavity and extend into the leg area. The first is the psoas major. It has it's origin on the transverse processes of thoracic vertebra number 12, and lumber vertebrae one through five. And it runs across the ilium, exits the inguinal canal and inserts on the lesser trochanter of the femur. The action of the psoas major is flexion of the femur. A so-called companion muscle to the psoas major is the iliacus. The origin of the iliacus is on the iliac fossa. And it joins with the psoas major through the inguinal canal to insert via a common tendon onto the lesser trochanter of the femur. And the action of the iliacus is the same as that of the psoas major, flexion of the femur. On the cadaver, the psoas major is this muscle right here. The origins on the transverse processes of thoracic vertebra 12 and lumbar vertebrae one through five. The iliacus muscle is this muscle here. The origin on the iliac fossa of the ilium, and they join shortly before the inguinal canal, and exit to insert on the lesser trochanter of the femur. The action of both muscles is flexion of the femur. Our next group of muscles are those focusing on the femur or upper leg. The first is the tensor fascia latae, which operates the hip. The origin of the tensor fascia latae is the iliac crest. The insertion is the IT band or iliotibial tract, also called the iliotibial band. And the action of the tensor fascia latae is to flex and abduct the femur as well as tense the IT band. Okay on the cadaver, the tensor fascia latae is a muscle in a small pouch essentially, located right here on the lateral side of the leg. The origin of the iliac crest and the insertion is the IT band, or the iliotibial tract, which is a heavy connective tissue that stabilizes the lateral portion of the thigh as well as the knee. The action of the tensor fascia latae is flexion and abduction of the thigh, as well as tension of the IT band. Our next muscle the sartorius. This muscle operates both the knee and hip. The origin of the sartorius is the anterior superior iliac spine. The insertion of the sartorius is the proximal and medial surface of the tibia. The action of the sartorius is flexion of the knee, and flexion and rotation of the femur. On the cadaver, the sartorius muscle is the slender strap running across the thigh, it's companion on the other side. The origin of the sartorius, the anterior superior iliac spine. The insertion of the sartorius is the proximal medial portion of the tibia. And the action of the sartorius is flexion and rotation of the hip, as well as flexion of the knee. Next we have the gracilis, also operates the knee and hip. The gracilis is a muscle that runs on the medial aspect of the thigh. The origin is the pubic bone, and the insertion like that of the sartorius is the proximal medial surface of the tibia. The action of the gracilis is flexion of the knee and adduction of the femur. On the cadaver, the gracilis is this strap like muscle here, as well as this strap muscle here. The origin, the pubic bone. The insertion coming together with the sartorius, the medial proximal aspect of the tibia. And the action of the gracilis is flexion of the knee and adduction of the femur. Group of muscles are known as the quadriceps group. This group contains four separate muscles. They have the commonality of all going into the tibial tuberosity via the patellar ligament. The first of this group, and the most superficial is the rectus femoris. This muscle operates both the knee and the hip. The origin of the rectus femoris is the inferior anterior iliac spine. And the insertion via the patellar ligament is the tibial tuberosity. The action of the rectus femoris is flexion of the femur and extension of the knee. On the cadaver, the rectus femoris, the superficial slender muscle. The origin is the anterior inferior iliac spine. The insertion via the patellar ligament is the tibial tuberosity. The action of the rectus femoris is flexion of the hip and extension of the knee. The other three muscles of the quadriceps group have a common name of vastus. And the first of the vastus muscles is the vastus lateralis. This muscle operates the knee. The origin of the vastus lateralis is the greater trochanter of the femur, as well as the linea aspera of the femur on it's posterior side. The insertion of the vastus lateralis is the tibial tuberosity via the patellar ligament. The vastus lateralis, it's action is extension of the knee. On the cadaver the vastus lateralis, this large muscle here, the origin is the greater trochanter of the femur. The insertion via the patellar ligament, the tibial tuberosity. The action of the vastus lateralis is extension of the knee. The other muscle, the vastus medialis, the origin of the vastus medialis is the proximal medial surface of the femur. The insertion is the tibial tuberosity via the patellar ligament. And the action of the vastus medialis is extension of the knee. On the cadaver, the vastus medialis is this large muscle here. The origin is the proximal medial surface of the femur to the linea aspera. The insertion via the patellar ligament is the tibial tuberosity. And the action of the vastus medialis is extension of the knee. The final muscle in the quadriceps group is the vastus intermedius. This muscle also operates the knee. The origin is on the anterior and lateral borders of the femur. The insertion via the patellar ligament to the tibial tuberosity. And the action of the vastus intermedius is extension of the knee. On the cadaver, the vastus intermedius is best seen by moving the rectus femoris to the side and underneath this fascia lies the vastus intermedius. The origin is the anterior and lateral surfaces of the femur. The insertion via the patellar ligament to the tibial tuberosity. And the action of this muscle also is extension of the knee. Another muscle in the thigh area is the pectineus. This muscle operates the hip. The origin of the pectineus is the pubic bone. The insertion of the pectineus is the medial surface of the femur, inferior to the lesser trochanter. The action of the pectineus is adduction of the femur. On the cadaver, the pectineus is best found by moving the adductor longus out of the way, and the pectineus muscle itself is directly underneath. The origin is the pubic bone. The insertion, the medial surface of the femur immediately inferior to the lesser trochanter. And the action of the pectineus is adduction of the femur. Our next two muscles are adductor muscles. The adductor longus and the adductor magnus. The adductor longus and the adductor magnus both operate the hip. The origins of both are on the pubic bone. The insertion of both is on the linea aspera on the posterior aspect of the femur. And the action of both muscles is adduction of the femur. On the cadaver, the adductor longus is this large muscle here. The adductor magnus is medial and deep to the adductor longus. The origin of both is the pubic bone. The insertion of both, the linea aspera of the femur. And the action of both is adduction of the femur. One of the muscles on the rear of the leg, one of the hamstring muscles, the semimembranosus, operates the knee and the hip. The origin is the ischial tuberosity and the insertion is the posterior surface of the medial condyle of the tibia. Posterior surface of medial condyle of the tibia. The semimembranosus muscle operates both the knee and the hip. This muscle flexes the knee and extends the femur. On the cadaver, the semimembranosus is this large medial muscle here. The origin is the ischial tuberosity. The insertion is the medial surface of the medial condyle of the tibia. The action of the semimembranosus muscle is flexion of the knee and extension of the femur. Muscles of the lower leg beginning with the gastrocnemius muscle. This muscle operates both the knee and the ankle. The origin of the gastrocnemius muscle is the femoral condyles. The insertion of the gastrocnemius is the calcaneus via the Achilles tendon. The action of the gastrocnemius muscle is extension of the foot and flexion of the knee. On the cadaver, the gastrocnemius muscle is here. And the companion on the other side. The origins, the condyles of the femur. The insertion via the Achilles tendon is the calcaneus. The action of the gastrocnemius muscle is flexion of the knee and extension of the foot. Our next muscle is the soleus, which lies deep to the gastrocnemius. It also operates the ankle. The origin of the soleus is the head of the fibula and the posterior lateral surface of the tibia. The insertion via the Achilles tendon is the calcaneus. And the action of the soleus is extension of the foot. On the cadaver, the soleus, positioned here underneath the gastrocnemius. The origin is the head of the fibula and the posterior lateral surface of the tibia. The insertion via the Achilles tendon is the calcaneus. And the action of the soleus is extension of the foot. Another muscle of the lower leg is the tibialis anterior. This muscle operates the ankle. And the origin of the tibialis anterior is the lateral condyle of the tibia, as well as the proximal surface of the tibia and it proceeds distally. The insertion of the tibialis anterior is the medial cuneiform and the first metatarsal. The action of the tibialis anterior is flexion of the ankle. On the cadaver, the tibialis anterior is this muscle here. The origin, the lateral condyle of the tibia, as well as the posterior lateral surface of the tibia. The insertion via the tendon is the medial cuneiform and the first metatarsal. The action of the tibialis anterior is flexion of the foot. A companion to the tibialis anterior is the tibialis posterior muscle. This one also operates the ankle. The origin is the interosseous membrane between the tibia and the fibula. The tendon passes underneath the calcaneus, and the insertion of the tibialis posterior includes metatarsals two, three and five. The action of the tibialis posterior is extension of the foot and inversion of the foot. On the cadaver, the tibialis posterior can be seen deep to the soleus, extending out inferiorly. And the origin again is the interosseous membrane between the tibia and the fibula. The tendon of the tibialis posterior proceeds under the calcaneus. And the insertion includes metatarsals two, three and five. The action of the tibialis posterior is extension of the foot and inversion of the foot. One of our last muscles of the lower leg is the fibularis longus, also known as the peroneus longus. This muscle operates the ankle. The origin of the fibularis longus is the head and proximal portion of the fibula. The tendon proceeds underneath the calcaneus, and the insertion is the medial cuneiform and metatarsal number one. The action of the fibularis longus is extension of the foot and eversion of the foot. On the cadaver, the fibularis longus can be seen laterally coming out from behind the gastrocnemius. The origin is the head and proximal portion of the fibula. The muscle continues and then via the tendon, proceeds underneath the calcaneus and the insertion is the medial cuneiform and metatarsal number one. The action of the fibularis longus is extension of the foot and eversion of the foot. Muscles of the posterior thigh include the gluteus maximus, which operates the hip. The origin of the gluteus maximus is the iliac crest, the sacrum and the coccyx. The insertion of the gluteus maximus is the gluteal tuberosity, as well as the iliotibial band. The action of the gluteus maximus is extension of the femur. The second muscle in the gluteal group is the gluteus medius, also operating the hip. The origin of the gluteus medius is the superior lateral surface of the iliac crest. And the insertion of the gluteus medius is the greater trochanter. The action of this muscle is abduction and medial rotation of the femur. The third muscle of the gluteal group is the gluteus minimus, also operating the hip. This muscle the origin is the inferior lateral surface of the ilium. The insertion is the greater trochanter. And the action of this muscle is abduction and medial rotation of the femur. Other muscles of the posterior thigh include the biceps femoris. This muscle operates both the knee and the hip. The origin of the biceps femoris is the ischial tuberosity, as well as the linea aspera of the femur. The insertion of the biceps femoris is the head of the fibula and the lateral condyle of the tibia. The action of the biceps femoris is flexion of the knee and extension of the femur. Okay. The third muscle of the hamstring group is the semitendinosus. This muscle operates the knee and the hip. The origin of the semitendinosus is the ischial tuberosity. And the insertion is the medial surface of the proximal tibia. The action of the semitendinosus is flexion of the knee and extension of the femur.