Skeletal Muscles Of A Toad/frog 3f6m4x

SKELETAL MUSCLES – consists of the origin and the insertion - taper at their ends into the tendons TENDONS – tough white cords of connective tissue - serve to attach SM to bones or other M ORIGIN – fixed end INSERTION- movable end HEADS – end with more than one origin SLIPS – more than one point of insertion BELLY – 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 part 2. FLEXORS-bend one part toward another part 3. 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 cavity B. Pectoral or Chest - inserted on ventral side of humerus - draw the arm toward the chest and expand abdominal activity C. Lower jaw D. Dorsal side of Head & Trunk E. Ventral surface of Thigh (upper leg) F. Dorsal side of Thigh G. Shank (lower leg) A. ABDOMINAL MUSCLES 1. Rectus Abdominis - occupy mid-ventral part - divided longitudinally by LINEA ALBA - Transversely by INSCRIPTIONES TENDINAE 2. External Oblique - cover sides of the body from the ilium & inserts on the Linea Alba 3. 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 humerus 1. Pectoralis Epicoracoidea - arises from coracoid & epicoracoid 2. Pectoralis Sternalis - arises from sternum & xiphisternum 3. Cutaneous Pectoralis - pocket-shaped M. covering Pectoralis sternalis 4. Pectoralis Abdominis - arises from anterior half of Rectus abdominis C. LOWER JAW MUSCLES 1. Mylohyoid - superficial M. originating from medial surface of mandible & inserted on the median raphe 2. Geniohyoid - lateral, underlying muscle w/c originates from tip & border of lower jaw & inserts onto the processes & body of the hyoid & a more medial Hyoglosus 3. Genioglosus – anterior to the Hyoglosus 4. Submentalis – small muscle at tip of lower jaw 5. 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 cranium 2. Temporalis - large muscle posterior to the eyes at the level of the tympanic membrane - from middorsal line of cranium & extends ventrally ing bet. the eyes and the eardrums 3. Depressor mandibulae – posterior to the temporalis 4. Masseter - short M. wedged bet. temporalis and depressor mandibulae inserted on the mandible 5. 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 anteriorly 8. 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 ilium b.) middle Rectus femoris anticus w/c arises from ventral border of the posterior third of the ilium in front of the acetabulum c.) 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 Thigh 1. Gluteus - medial & anterior to the triceps femoris - orig. from ilium & inserted on the femur 2. 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 fibula 3. 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