muscular system part 1

MuscularSystemOrigin -  Point of attachment which is

more proximal and more fixed Insertion -  The more distal and more

movable (flexible) point of attachment

Belly -  Fleshy or middle part of a

muscle

TypesofMuscles

Flexors -  bend or flex a part

Extensor -  straighten of extend a

part

Abductors -  pull a part away from the

median line or axis of the body

Adductors - Pull a part toward the

median line of the body

Synergist -  muscles that help the prime mover by producing the

same movement or reducing undesirable or unnecessary movement

ex. Sternoradialis – synergist of Biceps brachii Antagonist - muscle working in opposition to another muscle

Naming of Skeletal Muscles 1. Location and direction of muscle fibers ex External Oblique Rectus abdominis Rectus femoris 2. Number of origin ex. Biceps – muscle of the arm with 2 heads Triceps – muscle with 3 heads 3. Action ex. Extensor cruris Flexor tarsi anterior 4. Shape of the muscle ex. Deltoid 5. Attachment ex. Scapulohumeralis (origin – scapula, insertion – deltoid ridge of

humerus 6. Size of the muscle ex. Gracilis major Gracilis minor

Dorsal Muscles of the Head and TrunkTemporalis -  Muscle posterior to the eye

and about the level of tympanic membrane

Action – raise the lower jaw and closes the mouth

Depressor mandibulae -  Flattened muscle posterior

to the temporalis muscle Action – depress the jaw Dorsalis scapula(e) -  large, broad muscle

underneath the depressor mandibulae

Action – abduct the arm

Temporalis

Latissimus dorsi -  large, flat, triangular

muscles posterior to the depressor mandibulae

Action – draws the forelimbs upward and backward

Longissimus dorsi -  Muscle posterior to the L.

dorsi tapering posteriorly Action – extends the back

and elevates the head

Iiolumbaris -  muscle lateral to the Longissimus dorsi Action – bends the back Coccygeosacralis -  paired -  small V shaped muscle immediately posterior to

Longissimus dorsi Action – draws the back and the urostyle nearer to each other Coccygeoiliacus -  pair of V shaped muscle posterior to the coccygeo-

sacralis Action - fixes the urostyle and helps extend the back

Ventral Muscle of the Head, Trunk and AbdomenMylohyoid -  thin, broad, transverse

muscle divided into halves my median longitudinal c. tissue (median raphe) on the ventral side of the floor of the mouth

Action – raises the floor of the mouth during swallowing and breathing

Geniohyoid -  flat muscle underneath the

mylohyoid Action – draws the hyoid

forward and upward

Sternoradialis - median pair of muscles partly covered by the

mylohyoid Action – flexor of the forearm Deltoid (Scapulohumeralis) - thick muscle that passes obliquely to the

sternoradialis Action – prime mover for arm adduction Triceps brachii (upper arm) - large muscle on the posterior side of the

upper arm Action – prime mover for extension of the

forearm Biceps brachii (upper arm) Action – flex the forearm Pectoralis muscle -  (anterior, middle and posterior) Action – adductor and rotator of the arm

Rectus abdominis - large muscle that forms the ventral

abdominal wall linea alba- median ventral connective tissue dividing the muscle into longitudinal halves inscriptiones tendinae - divides the muscle into segments Action - compress and support the abdomen External oblique - outer muscle that forms the lateral wall of

the abdomen - fibers obliquely directed Action – constrict the abdomen Transversus abdominis - innermost muscle of the abdomen - thin muscle underneath the external oblique Action – constrict the abdomen

Dorsal Muscles of the ThighTriceps femoris - largest and most anterior 3

headed muscle of the thigh Action – draws the hind limb

forward and extends the leg Gluteus - small but thick muscle found

anterior to the Vastus externus and medial to the Rectus femoris anticus

Action – rotates the femur forward

Biceps femoris (Iliofibularis ) - slender muscle posterior to the

triceps Action – flex the leg

Semimembranosus - large muscle with oblique

markings posterior to Biceps femoris

Action – adducts the thigh, flex and extend the shank

Pyriformis - slender, short muscle found

between the V. externus and proximal end of Semimembranosus

Action – pulls the urostyle to one side

Dorsal Muscles of the Shank

Gastrocnemius -  largest and most posterior muscle of the shank Action – flexor of the leg and

extensor of the foot Peroneus - anterior to the Gastrocnemius - antagonist of Gastrocnemius Action - ? Tibialis anticus - most anterior muscle of the shank and splits into two slips Action – extensor of the leg ,

flexor of the foot

Ventral Muscles of the Thigh

Sartorius - flat muscle that runs obliquely

downwards Action – flexor of the thigh Adductor longus - flat muscle underneath the Sartorius Action – pulls thigh ventrally and forward Adductor magnus - thick, triangular muscle posterior

to the adductor longus Action – pulls the thigh forward,

adductor or abductor of the thigh