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Overview of Muscle Anatomy

  • Understanding muscles is crucial for studying anatomy, particularly their functions and locations.

Key Muscle Groups and Functions

Upper Body Muscles

  • Extensor Digitorum Longus: A muscle responsible for extending the fingers.

  • Levator Labii Superioris Alkenazii: A muscle of facial expression.

  • Orbicularis Muscles:

    • Orbicularis Oculi: Circular muscle surrounding the eye, responsible for closing the eyelids.

    • Orbicularis Oris: Circular muscle around the mouth, responsible for constricting the lips.

  • Zygomatic Muscles: Responsible for smiling (Zygomatic Major and Minor).

  • Sternocleidomastoid: Attaches from the mastoid process to the sternum and clavicle; involved in neck rotation.

  • Trapezius: Muscle responsible for moving shoulder blades and supporting the arm.

Muscle Groups of Breathing

  • External Intercostal Muscles: Elevate ribs during inhalation.

    • Internal Intercostal Muscles: Involved in forced exhalation, with fibers going in the opposite direction of external intercostals.

  • Diaphragm: Main muscle of respiration controlled by the phrenic nerve (C3, C4, C5). It is essential for breathing in and out.

Core Muscles

  • Rectus Abdominis: Known as the 'six-pack,' involved in trunk flexion and stabilization.

  • External Obliques: Run diagonally downwards, involved in trunk rotation and lateral flexion.

  • Internal Obliques: Run diagonally upwards, providing similar functions to external obliques.

  • Transverse Abdominis: Deepest abdominal muscle, important for core stability.

  • Linea Alba: Connective tissue separating the left and right rectus abdominis.

Shoulder Muscles

  • Deltoid: Responsible for shoulder abduction and gives contour to the shoulder area.

  • Pectoralis Major: Primary muscle of the chest; assists in shoulder movement.

    • Minor Over Major Rule: Minor muscle is superior to major muscle.

  • Serratus Anterior: Assists in the protraction and rotation of the scapula.

  • Latissimus Dorsi: Known for shoulder extension, internal rotation, and adduction.

Rotator Cuff Muscles

  • Supraspinatus and Infraspinatus: Serve to stabilize the shoulder joint and facilitate movement.

    • Teres Major: Not a part of the rotator cuff but works closely with these muscles.

  • Subscapularis: Located on the anterior side of the scapula; involved in internal rotation of the shoulder.

Arm Muscles

  • Biceps Brachii: Involved in elbow flexion and is made up of two heads.

  • Triceps Brachii: Responsible for elbow extension.

  • Brachioradialis: Muscle that flexes the elbow and involves radial deviation.

  • Pronator Teres and Supinator Muscles: Involved with forearm rotation.

Hip and Thigh Muscles

  • Rectus Femoris: A part of the quadriceps, responsible for knee extension and hip flexion.

  • Sartorius: A long muscle aiding in flexion, external rotation, and abduction of the hip.

  • Iliopsoas: Key muscle complex consisting of the iliacus and psoas major; responsible for hip flexion.

  • Adductor Group: Including Adductor Magnus, Brevis, and Longus, these muscles are responsible for hip adduction and are located medially on the thigh.

Gluteus Muscles

  • Gluteus Medius: Responsible for hip abduction.

  • Gluteus Maximus: Major muscle involved in hip extension and lateral rotation.

Lower Body Muscles

  • Gastrocnemius: Major calf muscle involved in plantar flexion.

  • Soleus: Works with the gastrocnemius for plantar flexion when seated.

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