Muscular system

Connective tissues-endomysium (innermost), perimysium, and epimysium (superficial)- make a tendon

Tendons connect muscle to bone. Aponeuroses connect muscles to other muscles.

Most muscles span a joint and connect articulating bones. When the muscle contracts, movement occurs. Points of attachment are the origin and the insertion

Origin does not move when the muscle contracts (generally proximal)

Insertion moves when the muscle contracts (generally distal)

Muscle actions- prime mover-directly performs a function

Antagonists oppose the action of the prime mover when contracting

Synergists- facilitate the action of the prime mover

Fixators- are joint stabilizers

Movement is caused by contraction of the belly of the muscle, generally proximal to the moved part

Movement occurs by contraction of sarcomeres within the sarcoplasm of the muscle cells. Each sarcomere is composed of actin and myosin fibers arranged in formation. (see figure in textbook and review sliding filament theory). Muscular contraction requires oxygen and ATP. Without ATP there is rigor mortis (death)

Naming of muscles is based on:

# of parts- biceps, triceps, quadriceps

Direction of fibers- rectus, transversus, oblique, orbicularis..)

Location in the body- femoris, radialis, gluteus, pectoralis, capitis, cervicis..)

Shape- deltoid, trapezius

Action- flexor, exntensor, adductor, levator..

Points of attachment- sternocleidomastoid, occipitofrontalis..

Muscles of facial expression (1 point of attachment is to deep layers of skin)

Occipitofrontalis- from occipital bone to skin over frontal bone- raises eyebrows

Orbicularis oris- around mouth- closes lips (sometimes called the kissing muscle)

Orbicularis oculi- around eyes- closes eyes

Zygomaticus major- zygomatic bone to corners of mouth- smiling

Muscles of mastication (chewing)

Masseter- from zygomatic arch to mandible- closes jaw

Temporalis- from parietal bone to mandible- closes jaw

Movement of the head

Sternocleidomastoid- from sternum and clavicle to mastoid process of temporal bone- flexes head (one can also rotate head)- sometimes called the praying muscle

Muscles of the thorax

Diaphragm (only muscle required for breathing)- responsible for involuntary inspiration

External intercostals- from each rib to the rib below in the direction of hands in pockets- voluntary inspiration

Internal intercostals- from each rib to the rib above in the opposite direction of hands in pockets- voluntary expiration

Muscles of the abdominal wall

External oblique- ribs to os coxa all work together in straining

Internal oblique- os coxae to ribs to compress the abdomen

Rectus abdominus- os coxae to ribs (flexes trunk in sit-ups) some flex more to the side or

Transversus abdominus- os coxae to ribs rotate the trunk

Muscles of the pelvic floor-

Levator ani-pubis and ischium to coccyx-floor of the pelvic cavity

Back muscles

Trapezius-occipital bone and vertebrae to clavicle and scapula ( origin and insertion can rreverse) –either extend the head or raise ( shrug) shoulders

Latissimus dorsi-vertebrae and ilium to humerus-extends and adducts arms posteriorly

Chest muscles-

Pectoralis major-clavicle, sternum and ribs to humerus- flexes and adducts upper arm

Serratus anterior-ribs to scapula. Abductor (rotator)- punching (boxer’s muscle)

Shoulder-

Deltoid- clavicle and scapula to humerus ( abducts ( and may rotate) the shoulder

Upper arm

Biceps brachii- scapula to radius- flexes and supinates foream

Triceps brachii-scapula and humerus to ulna-extends forearm

Brachialis-humerus to ulna- flexes and pronates forearm

Forearm

Flexor carpi__-humerus or ulna to carpals and metacarpals- flexes wrist

Extensor carpi__-humerus or ulna to metacarpals- extends wrist

Buttocks

Gluteus maximus- posterior ilium, sacrum and coccyx to femur- extends and rotates thigh outward

Gluteus medius-posterior ilium to femur- extends thigh

Gluteus minimus-posterior ilium to femur- extends thigh

Tensor fascia latae- ilium to lateral tibia- abducts leg at thigh

Thigh (anterior)-Quadriceps femoris- vastus lateralis, vastus medialis, vastus intermedius, rectus femoris femur and os coxae-extends knee (and flexes thigh)

Sartorius- ilium to medial tibia (flexes and rotates thigh and knee (tailor’s muscle)

(medial)- Gracilis- pubic bone to medial tibia- adducts leg at thigh

Adductor group (brevis, magnus, longus) pubic bone to medial tibia-adducts leg at thigh

(posterior) Hamstring group semitendinosus, semimebranosus, biceps femoris) –ischium or femur to tibia or fibula-flex knee and extend thigh

Leg (anterior) tibialis anterior- tibia to tarsal (med cun)- flexes foot

(posterior)-gastrocnemius ( superficial- femur to tarsals- extends foot, flexes knee

Soleus- tibia and fibula to tarsal- extends foot

Gastrocnemius and soleus insert together via Achilles tendon