Muscular System

Course 5,102 includes six specific anatomical models dedicated to the study of the muscular system.
General physiological functions of muscles throughout the body include:
- Facilitating skeletal movement.
- Maintaining cardiac contractions (heartbeat).
- Driving the flow of food through the intestinal tract.
- Executing eye focusing adjustments.
- Regulating arterial system adjustments to control blood flow and pressure.
Primary focus is on skeletal muscle groups involved in gross body movements rather than fine articulations.

Trapezius Muscle:
- Extends as a long string of muscle from the neck through the back and shoulder blade area, occupying the back plane of the upper shoulder.
- Responsible for the rotation and retraction of the shoulder blade.
- Prolonged sitting or supporting the head or neck in an awkward position leads to muscle tension and pain across this muscle group.
Latissimus Dorsi Muscle:
- Situated in the mid back region.
- Features the largest surface area of any muscle in the human body.
- Responsible for arm extension, rotation, lowering of the arms, and pulling the shoulders back.
Gluteus Medius Muscle:
- Controls hip abduction, thigh rotation, and pelvic tilting.
Gluteus Maximus Muscle:
- Characterized as the most bulkiest muscle in the body.
- Functions to straighten and pull back the hip during movement such as walking, running, and jumping.
Biceps Femoris Muscle:
- Forms part of two major muscle groups comprising the hamstring.
- Extends down the thigh at the hip, functioning to flex and rotate the leg.
- Highly susceptible to sports injuries including sprains, partial tears, or complete tears.
- Severe tears produce extensive swelling and bruising due to the significant size and blood supply of the muscle.
Gastrocnemius Muscle:
- Known as the primary calf muscle, consisting of two distinct sections: the medial head and the lateral head.
- Contracts and flexes the ankle, pulls up the heel, and aids in knee flexion.

Pectorals Major Muscle:
- Main chest muscle situated on the anterior chest wall.
- Responsible for arm movement.
Sartorius Muscle:
- Located on the anterior region of the lower body.
Rotator Cuff Muscle Group:
- Mnemonic for memorization: $SITS$ .
- Consists of four muscles that act in concert to achieve rotation, movement, and joint articulation in the shoulder:
- Supraspinatus Muscle: Located on the top aspect of the scapula area, directly superior on the shoulder ("supra" indicating top).
- Infraspinatus Muscle: Positioned at the midpoint or middle part of the shoulder, overlapping the backside around the scapular area.
- Teres Minor Muscle: Positioned almost inferior to the infraspinatus muscle; aids shoulder articulation.
- Subscapularis Muscle: Positioned more anteriorly to facilitate shoulder movement and articulation.
- Diagnostic Note: In cases of rotator cuff tears or injuries, enhanced imaging must be utilized to differentiate precisely which of the four muscles is involved.

Masseter Muscle:
- Large muscle involved in moving the lower jaw or mandible.
- Used during jaw clenching, pulling the jaw upward to close the mouth, and chewing articulations.
Dermocollidomastoid Muscle:
- Substantial muscle strand traversing the neck.
- Rotates and articulates the neck.
- Clinical Examination Landmark: Serves as a vital landmark during physical examination of the lymphatic system:
- Anterior cervical nodes lie in front of the dermocollidomastoid muscle.
- Posterior cervical nodes lie behind the dermocollidomastoid muscle.
Scalene's Muscles (Scalenes):
- Small muscle strands situated deeper, behind the trapezius muscle.
Levitator Scapula Muscles:
- Muscle structures associated with neck and scapular alignment, located near the scalenes.