Lastly the rhomboids can also elevate the scapula as a whole. This is true for all the muscles in the body. When studying anatomy, learn to look closely at the direction of the muscle fibers, and determine which end is the origin and which end is the insertion.
That information will take you a long way in figuring out what actions a muscle can do. It has two heads which means it originates in two spots: the top of the manubrium sternum and the medial third of the clavicle.
Its insertion is up behind the ear on the mastoid process and the outer portion of the occiput. The terms origin, insertion, and action are important to the language of kinesiology.
They can help us communicate with one another about body movement. A more open-minded way to think about this is that muscles have at least two attachments.
Whichever one is more mobile will move toward the other when the muscle that connects them contracts. We have a course that teaches you 65 muscles in 79 lessons using high-quality 3D models. What do the terms origin, insertion, and action mean? Fibrous bands called retinacula sheath the tendons at the wrist. The flexor retinaculum extends over the palmar surface of the hand while the extensor retinaculum extends over the dorsal surface of the hand.
The intrinsic muscles of the hand both originate and insert within it Figure These muscles allow your fingers to make precise movements for actions, such as typing or writing. These muscles are divided into three groups. The thenar muscles are on the radial aspect of the palm.
The hypothenar muscles are on the ulnar aspect of the palm, and the intermediate muscles are midpalmar. The thenar muscles include the abductor pollicis brevis , opponens pollicis , flexor pollicis brevis , and the adductor pollicis.
These muscles form the thenar eminence , the rounded contour of the base of the thumb, and all act on the thumb. The movements of the thumb play an integral role in most precise movements of the hand. The hypothenar muscles include the abductor digiti minimi , flexor digiti minimi brevis , and the opponens digiti minimi.
These muscles form the hypothenar eminence , the rounded contour of the little finger, and as such, they all act on the little finger. Finally, the intermediate muscles act on all the fingers and include the lumbrical , the palmar interossei , and the dorsal interossei. The appendicular muscles of the lower body position and stabilize the pelvic girdle , which serves as a foundation for the lower limbs.
Comparatively, there is much more movement at the pectoral girdle than at the pelvic girdle. There is very little movement of the pelvic girdle because of its connection with the sacrum at the base of the axial skeleton and because the deep acetabulum provides a stable point of articulation with the head of the femur.
If the center of gravity were not to remain fixed, standing up would be difficult. Most muscles that insert on the femur the thigh bone and move it, originate on the pelvic girdle. The major flexors of the hip are the psoas major and iliac which make up the iliopsoas group.
Some of the largest and most powerful muscles in the body are the gluteal muscles or gluteal group. The gluteus maximus , one of the major extensors of the thigh at the hip, is the largest; deep to the gluteus maximus is the gluteus medius , and deep to the gluteus medius is the gluteus minimus , the smallest of the trio Figure The tensor fascia latae is a thick, squarish muscle in the superior aspect of the lateral thigh.
It acts as a synergist of the gluteus medius and iliopsoas in flexing and abducting the thigh. It also helps stabilize the lateral aspect of the knee by pulling on the iliotibial tract band , making it taut. Deep to the gluteus maximus, the piriformis , obturator internus , obturator externus , superior gemellus , inferior gemellus , and quadratus femoris laterally rotate the thigh at the hip.
The muscles in the medial compartment of the thigh responsible for adducting the femur at the hip are the adductor group including the adductor longus , adductor brevis , and adductor magnus which all adduct and medially rotate the thigh. The adductor longus also flexes the thigh, whereas the adductor magnus extends it. Like the adductor longs, the pectineus adducts and flexes the femur at the hip.
The pectineus is located in the femoral triangle , which is formed at the junction between the hip and the leg and includes the femoral nerve, the femoral artery, the femoral vein, and the deep inguinal lymph nodes.
The strap-like gracilis adducts the thigh in addition to flexing the leg at the knee. The muscles of the anterior compartment of the thigh flex the thigh and extend the leg. This compartment contains the quadriceps femoris group , which is comprised of four muscles that extend the leg and stabilize the knee.
Within the compartment the rectus femoris is on the anterior aspect of the thigh, the vastus lateralis is on the lateral aspect of the thigh, the vastus medialis is on the medial aspect of the thigh, and the vastus intermedius is between the vastus lateralis and vastus medialis and deep to the rectus femoris.
The tendon common to all four is the quadriceps tendon patellar tendon , which inserts into the patella and continues below it as the patellar ligament. The patellar ligament attaches to the tibial tuberosity. In addition to the quadriceps femoris, the sartorius is a band-like muscle that extends from the anterior superior iliac spine to the medial side of the proximal tibia. This versatile muscle flexes the leg at the knee and flexes, abducts, and laterally rotates the thigh at the hip.
This muscle allows us to sit cross-legged. The posterior compartment of the thigh includes muscles that flex the leg and extend the thigh. The three long muscles on the back of the thigh are the hamstring group , which flexes the knee. These are the biceps femoris , semitendinosus , and semimembranosus. The tendons of these muscles form the upper border of the popliteal fossa , the diamond-shaped space at the back of the knee.
The muscles in the anterior compartment of the leg all contribute to dorsiflexion: the tibialis anterior , a long and thick muscle on the lateral surface of the tibia, the extensor hallucis longus , deep under it, and the extensor digitorum longus , lateral to it.
The fibularis tertius , a small muscle that originates on the anterior surface of the fibula, is associated with the extensor digitorum longus and sometimes fused to it, but is not present in all people. Thick bands of connective tissue called the superior extensor retinaculum transverse ligament of the ankle and the inferior extensor retinaculum , hold the tendons of these muscles in place during dorsiflexion.
The lateral compartment of the leg includes two muscles which contribute to eversion and plantar flexion: the fibularis longus peroneus longus and the fibularis brevis peroneus brevis. The superficial muscles in the posterior compartment of the leg all insert onto the calcaneal tendon Achilles tendon , a strong tendon that inserts into the calcaneal bone of the ankle, all contribute to plantar flexion.
The muscles in this compartment are large and strong and keep humans upright. The most superficial and visible muscle of the calf is the gastrocnemius. Deep to the gastrocnemius is the wide, flat soleus. The plantaris runs obliquely between the two; some people may have two of these muscles, whereas no plantaris is observed in about seven percent of other cadaver dissections.
The plantaris tendon is a desirable substitute for the fascia lata in hernia repair, tendon transplants, and repair of ligaments.
There are four deep muscles in the posterior compartment of the leg as well: the popliteus , flexor digitorum longus , flexor hallucis longus , and tibialis posterior all contribute to plantar flexion or inversion of the foot.
The foot also has intrinsic muscles, which originate and insert within it similar to the intrinsic muscles of the hand.
These muscles primarily provide support for the foot and its arch, and contribute to movements of the toes Figure The intrinsic muscles of the foot include the extensor digitorum brevis on the dorsal aspect and a plantar group , which consists of four layers. Muscles are either axial muscles or appendicular.
The axial muscles are grouped based on location, function, or both. Some axial muscles cross over to the appendicular skeleton. The muscles of the head and neck are all axial.
The muscles in the face create facial expression by inserting into the skin rather than onto bone. Muscles that move the eyeballs are extrinsic, meaning they originate outside of the eye and insert onto it.
Tongue muscles are both extrinsic and intrinsic. The genioglossus depresses the tongue and moves it anteriorly; the styloglossus lifts the tongue and retracts it; the palatoglossus elevates the back of the tongue; and the hyoglossus depresses and flattens it. The muscles of the anterior neck facilitate swallowing and speech, stabilize the hyoid bone and position the larynx.
The muscles of the neck stabilize and move the head. The sternocleidomastoid divides the neck into anterior and posterior triangles. The muscles of the back and neck that move the vertebral column are complex, overlapping, and can be divided into five groups. The splenius group includes the splenius capitis and the splenius cervicis. The erector spinae has three subgroups. The iliocostalis group includes the iliocostalis cervicis, the iliocostalis thoracis, and the iliocostalis lumborum. The longissimus group includes the longissimus capitis, the longissimus cervicis, and the longissimus thoracis.
The spinalis group includes the spinalis capitis, the spinalis cervicis, and the spinalis thoracis. The transversospinales include the semispinalis capitis, semispinalis cervicis, semispinalis thoracis, multifidus, and rotatores. The segmental muscles include the interspinales and intertransversarii. Finally, the scalenes include the anterior scalene, middle scalene, and posterior scalene. Made of skin, fascia, and four pairs of muscle, the anterior abdominal wall protects the organs located in the abdomen and moves the vertebral column.
These muscles include the rectus abdominis, which extends through the entire length of the trunk, the external oblique, the internal oblique, and the transversus abdominus. The quadratus lumborum forms the posterior abdominal wall. The muscles of the thorax play a large role in breathing, especially the dome-shaped diaphragm. When it contracts and flattens, the volume inside the pleural cavities increases, which decreases the pressure within them.
As a result, air will flow into the lungs. The external and internal intercostal muscles span the space between the ribs and help change the shape of the rib cage and the volume-pressure ratio inside the pleural cavities during inspiration and expiration. The perineum muscles play roles in urination in both sexes, ejaculation in men, and vaginal contraction in women. The pelvic floor muscles support the pelvic organs, resist intra-abdominal pressure, and work as sphincters for the urethra, rectum, and vagina.
The mastoid process is a little projection of bone located behind your ear. To feel the mastoid process, you can touch that tag of bone behind your ear with your finger. The origin of the SCM actually divides into two parts, with each attaching to different, but nearby areas. Each section of the origin is described as a head. One head of the SCM originates on the top of the collarbone, close to the center of your body.
The other head originates at the outside surface of the top of your breastbone. Next, let's look at the latissimus dorsi muscle. This is a very large back muscle that starts mainly from the area around your hips and back and goes all the way to your upper extremity. This large muscle originates at the pelvis, ribs, thoracolumbar fascia, and some vertebrae. Despite its size, the latissimus dorsi muscle eventually tapers to an insertion point that is located on the inside of your humerus.
The humerus is the upper arm bone. Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Your Privacy Rights.
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