lecture 17

Muscle Location and Actions:

• Pectoralis Major:

  • Location: Upper chest

  • Action: Abduction and forward rotation of the arm.

  • Mechanics: Origin on the sternum, insertion on the humerus. Always remember, the insertion pulls towards the origin.

Serratus Anterior:

• Location: Under the arm between the ribs.

• Action: Rotates the trunk and helps in overall body rotation.

Breathing Muscles:

• Internal Intercostals: Exhale.

• External Intercostals: Inhale.

• Diaphragm: Aids in both inhalation and exhalation.

External Oblique:

• Location: Side of the abdomen.

• Action: Lateral flexion of the trunk (leans sideways).

Rectus Abdominis:

• Location: Anterior abdomen (abs).

• Action: Flexion of the trunk forward.

Sternocleidomastoid:

• Location: Side of the neck.

• Action: Flexes head forward (both sides) or rotates head (if one side contracts).

Biceps Brachii:

• Location: Anterior upper arm.

• Action: Flexion of the lower arm.

Triceps Brachii:

• Location: Posterior upper arm.

• Action: Extension of the lower arm.

Deltoid:

• Location: Shoulders.

• Actions:

  • Abduction of the arm (moves away from midline).

  • Flexion of the arm (moves forward).

Rotator Cuff:

• Location: Under shoulder.

• Action: Rotates the arm.

Latissimus Dorsi:

• Location: Lower back (posterior).

• Actions:

  • Abduction of the arm.

  • Extension and hyperextension of the arm.

Trapezius:

• Location: Upper back.

• Action: Elevates or shrugs shoulders.

Splenius Group:

• Location: Posterior neck.

• Action: Extension and hyperextension of the head.

Hamstrings:

• Location: Posterior upper leg.

• Actions: Flexes the lower leg.

• Members:

  • Biceps femoris

  • Semitendinosus

  • Semimembranosus.

Quadriceps:

• Location: Upper front leg.

• Action: Extension of the lower leg.

• Members:

  • Rectus femoris

  • Vastus lateralis

  • Vastus medialis

  • Vastus intermedius.

Sartorius:

• Location: Front of the thigh.

• Action: Flexion of the leg laterally (used when crossing legs).

Gastrocnemius:

• Location: Posterior lower leg (calf).

• Action: Plantar flexion (pointing toes down).

Tibialis Anterior:

• Location: Anterior lower leg (shin).

• Action: Dorsiflexion (pulling toes up).

Iliacus and Psoas Major:

• Location: Groin.

• Action: Flexion of the leg.

Gluteal Group:

• Location: Buttocks.

• Actions:

  • Abduction of the leg (moving out to the side).

  • Extension and hyperextension of the leg (pulling back).

Adductors:

• Location: Inner thigh.

• Action: Adduction of the leg (bringing the leg back to the midline).

Facial Muscles:

• Epicranius: Raises eyebrows (facial expression).

• Masseter and Temporalis:

  • Location: Cheek area.

  • Action:

    • Masseter: Pulls the jaw up and back.

    • Temporalis: Moves jaw up and forward for chewing.

Assessment Preparation:

• Aim to understand the action and location of each muscle.

• Create stick figures to illustrate actions and identify associated muscles with flexion, abduction, and other essential movements.

• For the exam, know origins, insertions, and actions for the specified muscles, and understand the mechanics of how they function.

• Employ critical thinking to assess movements based on muscle location and actions rather than rote memorization.