The Muscular System

1. The Muscular System

2. Muscles in the Body • There are over 650 muscles in the human body. • They are named due to many factors.

3. Naming Skeletal Muscles (1) • Location of muscle • Bone or body region associated with the muscle • Shape of muscle • Ex: deltoid (triangular) • Relative size • Ex: maximus (large), minimus (small), longus (long) • Direction of fibers • Ex: rectus (fibers run straight), transversus, oblique (fibers run at angles to an imaginary defined axis.

4. Naming Skeletal Muscles (2) • Number of origins • Ex: biceps (2 origins) and triceps (3 origins) • Location of attachments • Named according to point of origin or insertion. • Action • Ex: flexor or extensor, as in the names of muscles that flex or extend.

5. Muscles of the Scalp • Epicranius 2 part muscle consisting of the following: • Frontalis • Primary function is to raise the eyebrows. • Occipitalis • Works with the frontalis

7. Temporalis • Located on the side of your forehead. • One of the major muscles of mastication (chewing) • Allows you to raise your cheeks

8. Sternocleidomastoid Muscles • Anterior muscles of the neck that act to flex and rotate the head.

9. Trapezius • Large muscle that extends from the neck to a person’s back. • Responsible for: • Shrugging • Turn head side to side. • Drawing the shoulder bones toward the midline. • Pulling the shoulder blades down. • Elevate the scapula • Rotate the scapula

10. Deltoid • Muscle forming the round contour of the shoulder. • Responsible for: • Shoulder abduction • Lifts the arm from to the side of the body. • Flexion • Extension

11. Biceps Brachii • Muscles in the upper arm • Have several functions: • Flex the elbow • Rotate the forearm

12. Triceps • Found in the upper arm. • An extensor muscle, unlike the biceps which act as flexors. • Allows for elbow extension, which allows for pressing activities.

13. Pectoralis Major • Also known as the “pecs.” • Thick, fan-shaped muscle at the upper front of the chest wall. • Actions: • Flexes the humerus (upper arm) • Draws the scapula anteriorly (back) and inferiorly (down)

14. Rectus Abdominis • Paired muscle running vertically on each side of the anterior wall of the human abdomen. • Commonly known as the “abs” • Functions • Key posturalmuscle • Responsible for flexing the lumbar spine as when doing a “crunch.” • Can play a role in respiration

16. Oblique Muscles • Located on the sides of the abdomen. • Allow you to twist.

17. Latissimus • Large flat dorso-lateral muscle of the trunk. • Also known as the “lat.” • Responsible for: • Extension, adduction, transverse extension, and internal rotation of the shoulder joint. • It also has a synergistic role in extension and lateral flexion of the lumbar spine.

19. Gluteus Maximus • It is a large muscle in the butt. • One of the strongest muscles in your body. • Responsible for: • Extends the femur • Keeps body upright when motion is occurring and when motion stops.

21. Rectus fermoris • One of the four quadriceps muscles • Located in the middle, front of the thigh. • Functions: • Hip flexion • Knee extension

22. Sartorius • A long, thin muscle that runs down the length of the thigh. • Longest muscle in the human body. • Responsible for: • Abduction, flexion, and lateral rotation of the hip • Medial rotation of the knee

23. Hamstrings • Located in the back of your leg. • Responsible for: • Flexion of the knee • Walking, running, jumping, and controlling some movement of the trunk.

24. Gastrocnemius • Located in the back part of the lower leg. • Also called the calf. • Involved in: • Standing, walking, running, and jumping.

25. Tibialis anterior • Muscle in the shin that spans the length of the tibia. • Functions to stabilize the ankle and foot.