EC

Muscle Anatomy Notes

Key Structures in Muscle Anatomy

  • M Line

    • Dark area indicating the thick filaments in a myofibril.

  • C Disc (Z line)

    • Area found in the thin part of the sarcomere; serves as the boundary between sarcomeres.

Muscle Types

  • Active Muscle
    • Muscles that are engaged, such as the M line visible in a muscle contraction.
  • I-line
    • Refers to the thin filaments in a muscle structure.

Muscle Structures and Coverings

  • Myofibers
    • Bundles of myocytes, indicating a collection of muscle fibers.
  • Endomysium
    • Connective tissue surrounding individual muscle fibers.

Tendons and Extrinsic vs Intrinsic Muscles

  • Superior Oblique Muscle
    • Identified by its tendon passing across the medial area of the eye, important for eye movement.
  • Extrinsic Muscles
    • Muscles originating outside of the target area but move the target. E.g., muscles of the eye and hand.
  • Intrinsic Muscles
    • Muscles that originate and insert within the target area. E.g., the iris muscles of the eye and muscles in the hand.

Major Muscle Groups in Human Anatomy

Torso Muscles

  • Trapezius
    • Major muscle around the neck and shoulders.
  • Latissimus Dorsi
    • Sweeping muscle in the lower back area, involved in shoulder movement and rotation.
  • Serratus Anterior
    • Located on the side, assists in the movement of the shoulder.
  • Erector Spinae
    • Group of muscles responsible for maintaining an erect posture.
    • Divided into:
    • Iliocostalis
    • Longissimus
    • Spinalis

Abdominal Muscles

  • Rectus Abdominis
    • Forms the front of the abdomen, contributes to flexion of the spine.
  • Linea Alba
    • Connective tissue running down the middle of the abdomen, important in structuring the abdomen.
  • Diaphragm
    • Critical muscle for respiration.
  • Psoas
    • Provides support for sitting posture and spine stability.

Arm Muscles

  • Biceps Brachii
    • Muscle with two heads, important for elbow flexion.
  • Brachialis
    • Positioned under the biceps, contributes to elbow flexion.
  • Triceps Brachii
    • Muscle with three heads, responsible for elbow extension.
  • Brachioradialis
    • Muscle of the forearm, helps flex the elbow.

Leg Muscles

  • Sartorius
    • Long muscle of the thigh, assists in crossing legs.
  • Quadriceps
    • Group of four muscles that extend the knee:
    • Rectus Femoris
    • Vastus Lateralis
    • Vastus Medialis
    • Vastus Intermedius
  • Hamstrings
    • Group of three muscles located at the back of the thigh, responsible for knee flexion:
    • Biceps Femoris
    • Semitendinosus
    • Semimembranosus

Calf Muscles

  • Gastrocnemius
    • Major calf muscle involved in plantarflexion of the foot.
  • Soleus
    • Underneath gastrocnemius; together they form the Achilles tendon.

Important Notes for Exam

  • Use full names for muscles (e.g., Biceps Brachii, Triceps Brachii) in exams.
  • Distinguish between intrinsic and extrinsic muscles, as it is critical for understanding muscle function in anatomy.