Lab Practical 1 (Muscle Identification) - ANS 2140L

Biceps Femoris

On lateral part of hind leg.

Cutaneous Trunci

Directly under skin, horizontal striations, and is usually separated with the skin. Responsible for skin twitching reflexes.

Gastrocnemius

In the middle of the hind leg and contracts when the leg moves.

Gluteus Group

Located anterior of tail and is dark pink in color.

Gracilis

On the medial part of the hind leg and is a thin sheet.

Latissimus Dorsi

Located caudal of the shoulder. Striations fan out caudal/dorsal.

Longissimus Dorsi

Runs along exterior of the spine. Loin + chop cut of meat.

Obliquus Externus Abdominis

Located lateral of rectus abdominis. Striations run diagonally cranial and dorsal.

Pectoralis Profundi

Wraps around medial parts of front legs.

Quadriceps femoris

Located near the stifle, on cranial part of hind leg.

Rectus Abdominis

Located in the stomach region, “abs.” Bacon cut of meat.

Semimembranosus

Located on inner leg, lateral to gracilis.

Semitendinosus

Located on caudal part of hind leg, below the tail. Tendon-like.

Serratus Ventralis

Medial, beneath the Latissimus Dorsi. Large white lines make it look serrated.

Supraspinatus

Located in front of the scapula ridge.

Trapezius

Located dorsal of the shoulder, looks like a large dark triangle.

Triceps Group

Located on caudal part of the front leg.

Subscapularis

Located on the back of the scapula.

Psoas Major

Begins at the medial surface caudal to the last rib, ventral to the vertebrae.

Supraspinatus

Located “above” the scapula.

Infraspinatus

Located “below” the scapula.

Smooth Muscle

• Not striated, involuntary, single nucleus

• Found in GI, reproductive, ureters, blood vessels

• Circular and longitudinal layers, individual cells

• Involved in two types of contractions:

  • Peristalsis = progressive alternating wave of coordinated contraction + relaxion of smooth muscle = movement of material (esophagus)

  • Segmentation = stationary rhythmic contraction + relaxation of circular intestinal smooth muscle = mixing of material (stomach)

Cardiac Muscle

• Striated, involuntary, 1-2 nuclei

• Found in heart

• Connected by intercalated discs (connects cell membrane of one cell to the next, increasing electrical and molecular connections)

Skeletal Muscle

• Striated, voluntary, multinucleated

• Attached to bones

• Longitudinal layers, NOT branched —> elongated cells = fibers

  • Functions to maintain posture and allow for movement

  • Origin = end of muscle that is attached to stationary part of bone

  • Insertion = end of muscle attached to mobile section of bone