Muscles that form the Pelvic Floor The pelvic floor consists primarily of two

Muscles that form the pelvic floor the pelvic floor

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Muscles that form the Pelvic Floor
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The pelvic floor consists primarily of two flat muscle sheets and the attached fascia. These structures support the pelvic viscera and play a role in expelling the contents of the urinary bladder and rectum. Muscles of the Shoulder (Pectoral) Girdle and Arm Trapezius- The trapezius has its origin at the base of the occipital bone and the spines of all thoracic vertebrae; it inserts on the clavicle and scapula (shoulder blade). When contracted, the trapezius moves the clavicle and scapula and allows for a shrugging and rotating movement of the pectoral girdles. The trapezius causes medial rotation by pulling the shoulder blades (scapulae) together. The muscle gets its name because the right and left trapezius form the shape of a trapezoid. Serratus anterior- The serratus anterior is located on the sides of the chest and extends from the upper ribs (origin) to the scapula (insertion). The serratus muscle has a jagged shape, much like the jagged edge of a serrated knife blade. When the serratus anterior contracts, the shoulders are lowered, and the arm moves forward as if pushing a cart. The trapezius and serratus anterior attach the scapula to the axial skeleton. Pectoralis major- The pectoralis major is a large broad muscle that helps form the anterior chest wall. It connects the humerus (arm) with the clavicle (collarbone) and structures of the axial skeleton (ribs and sternum). Contraction of this muscle moves the arm across the front of the chest, as if pointing to an object in front of the body. (A more precise description of the function of the pectoralis major: It adducts and rotates the arm medially at the shoulder joint as well as flexes and extends the arm at the shoulder joint.) Many gym exercises are designed to hypertrophy the “pecs.” Latissimus dorsi - The latissimus dorsi is a large broad muscle located in the middle and lower back region. Its origin is on the lower thoracic vertebrae, lumbar vertebrae, sacrum, and lower ribs; it inserts on the posterior humerus. Contraction of this muscle lowers the shoulders and brings the arm back, as if pointing to an object behind you. Deltoid - The deltoid forms the rounded portion of the shoulder and forms the shoulder pad. The deltoid extends from its origins on the clavicle and scapula to its insertion on the humerus. Contraction of the deltoid muscle abducts the arm, raising it to a horizontal position (the scarecrow position). It also flexes, extends, and rotates the arm at the shoulder joint. Because of its size, location, and good blood supply, the deltoid is a common site of an intramuscular injection. Teres major- The teres major is a long, round muscle that has its origin on the scapula and inserts on the humerus. It extends the arm at the shoulder joint and assists with the medial rotation and adduction of the arm at the shoulder joint.
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Rotator cuff muscles- The rotator cuff muscles are a group of four muscles that attach the humerus (insertion) to the scapula (origin).
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  • Fall '19
  • muscle weakness, muscle atrophy, functions of muscles

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