SKELETAL MUSCLES– consists of the origin and the insertion- taper at their ends into the tendonsTENDONS – tough white cords of connective tissue - serve to attach SM to bones or other MORIGIN – fixed endINSERTION- movable endHEADS – end with more than one originSLIPS – more than one point of insertionBELLY – fleshy middle portion ACTION – movement of effect caused by M

*Each SM has a characteristic origin, insertion and action.*They are arranged in antagonistic pairs/groups that have opposing actions*Effective study: time, patience & good dissection technique

General Classes of SM accdg. to Action:

1. EXTENSORS –straighten or extend a part2. FLEXORS-bend one part toward another part3. ADDUCTORS- pull a part back toward the axis of the body.4. ABDUCTORS- draw a part away from Axis of the Body

Skinning the Toad Ventral surface up Cut along midventral line from anterior tip of

jaw to region of cloaca Transverse cut thru skin Loosen skin with blunt instrument FASCIA- thin white sheets of C.T. between

the skin and muscles Subcutaneous lymph sacs- large areas

where skin is not attached to muscles and where colorless fluid collects in a living toad.

Turn skin inside out Carefully free & separate M with blunt probe Follow direction of muscle fibers in separating In exposing deeper muscles, reflect covering

muscle by cutting it thru its belly

THE PRINCIPAL MUSCLES

A. Abdominal – contract the body cavityB. Pectoral or Chest - inserted on ventral side of humerus- draw the arm toward the chest and expand abdominal activityC. Lower jaw D. Dorsal side of Head & TrunkE. Ventral surface of Thigh (upper leg)F. Dorsal side of ThighG. Shank (lower leg)

A. ABDOMINAL MUSCLES1. Rectus Abdominis- occupy mid-ventral part- divided longitudinally by LINEA ALBA- Transversely by INSCRIPTIONES TENDINAE2. External Oblique- cover sides of the body from the ilium & inserts on the Linea Alba3. Internal Oblique/Transversus- beneath external oblique- forms innermost layer of abdominal muscles

B. PECTORAL MUSCLES- anterior to abdominal muscles- inserted on the ventral side of humerus1. Pectoralis Epicoracoidea - arises from coracoid & epicoracoid2. Pectoralis Sternalis- arises from sternum & xiphisternum3. Cutaneous Pectoralis- pocket-shaped M. covering Pectoralis sternalis4. Pectoralis Abdominis- arises from anterior half of Rectus abdominis

C. LOWER JAW MUSCLES1. Mylohyoid- superficial M. originating from medial surface of mandible & inserted on the median raphe2. Geniohyoid- lateral, underlying muscle w/c originates from tip & border of lower jaw & inserts onto the processes & body of the hyoid & a more medial Hyoglosus3. Genioglosus – anterior to the Hyoglosus 4. Submentalis – small muscle at tip of lower jaw5. Sternoradialis – lies posterior to Geniohyoid & partly covered by Mylohyoid.- originates from sternum & inserts on to radius.6. Deltoid/Scapulo-humeralis-postero-lateral to mylohyoid w/c originates from scapula & inserts onto the humerus - it extends the arm. D. Dorsal side of Head & Trunk 1. Pterygoideus – at eye level

- from middorsal line of the cranium2. Temporalis - large muscle posterior to the eyes at the level of the tympanic membrane- from middorsal line of cranium & extends ventrally passing bet. the eyes and the eardrums3. Depressor mandibulae – posterior to the temporalis4. Masseter - short M. wedged bet. temporalis and depressor mandibulae inserted on the mandible5. Dorsalis scapulae- large broad muscle posterior to Depressor mandibulae- from dorsal surface of suprascapula & scapula, extends ventrally & inserts on lateral side of humerus.6. Latissimus Dorsi - large flat muscle posterior and partly covering Dorsalis scapulae - from lumbo-dorsal fascia & inserts on lateral side of the proximal end of humerus.7. Longissimus Dorsi- mass of muscles that tapers posteriorly & posterior to Latissimus dorsi - from anterior third of urostyle extending anteriorly8. Iliolumbaris- lateral to longissimus dorsi w/c came from anterior part of ilium- inserts onto transverse processes of the trunk vertebrae.9. Coccygeosacralis- small V-shaped m. posterior to Longissimus dorsi 10. Coccygeoiliacus- bigger V-shaped m. posterior to Coccygeosacralis

E. Ventral surface of Thigh (upper leg)1. Triceps femoris- large muscle covering entire of lateral surface of the thigh- its 3 heads: a.) outer Vastus externus w/c arises from posterior end of the crest of the iliumb.) middle Rectus femoris anticus w/c arises from ventral border of the posterior third of the ilium in front of the acetabulumc.) inner Vastus internus w/c arises from the inner border of acetabulum

2. Sartorius- slender muscle transversing the thigh obliquely w/c arises from lower end of ilium & inserted on the proximal end of the tibio-fibula

3. Adductor longus

- partly covered by Sartorius whose small portion is exposed along the pre-axial side of the Sartorius. 4. Adductor magnus- stout muscle lying behind Sartorius crossing it as its distal end. - arises from the ischium & pubis and inserts at the distal end of the femur.5. Gracilis major- large muscle at the posterior margin of the thigh w/c bears an oblique marking near its posterior portion.6. Gracilis minor- slender m. closely attached to Gracilis majorw/c runs along the inner margin of the thigh.7. Semitendinosus- slender shiny m. that can be seen by pushing aside the gracilis major and originated by two heads from the ischium.

F. Dorsal side of Thigh1. Gluteus- medial & anterior to the triceps femoris - orig. from ilium & inserted on the femur2. Biceps femoris- long slender m. partly covered by the triceps’ Vastus externus - originating from posterior end of the dorsal crest of the ilium & inserting into the proximal end of the fibula3. Semimembranosus- large muscle posterior to biceps femoris with an oblique marking across it. 4. Piriformis- small muscle near the cloacal opening, between the biceps femoris & the semimembranosus

G. Shank (lower leg)1. Gastrocnemius- biggest muscle at the medial surface of the shank- has two heads & is inserted by means of the

tendon of Achilles

2. Peroneus- lateral to & partly covered by the Gastrocnemius

3. Tibialis posticus- long narrow muscle beneath the gastrocnemius & posterior to the tibio-fibula