Muscles of the Head, Neck, & Trunk

1. Muscles of theHead, Neck, & Trunk Facial muscles Chewing muscles Neck muscles Anterior trunk muscles Posterior trunk muscles

2. Facial Muscles Allow humans to produce a wide variety of expressions Found within layers of superficial fascia(connective tissue beneath the skin), and their origins are either within this fascia, or in the bones of the skull The moveable “bone” or the insertion is skin, rather than a bone/joint

3. Facial Muscles • Frontalis • Covers the forehead, inserts to the skin of the eyebrows. • Draws scalp forward , raises eyebrows, wrinkles skin of forehead horizontally • Orbicularisoculi • Fibers run circularly around the eyes • Closes eye, allows you to squint, blink, wink

4. Facial Muscles • Zygomaticus • Corner of the mouth to the cheek bone (zygomatic bone) • Draws mouth upward and outward, as in laughing and smiling • Orbicularisoris • Muscle fibers surrounding mouth circularly • Closes and protrudes lips, shapes lips during speech; “kissing muscle”

5. Facial Muscles • Temporalis • Fan-shaped muscle overlying the temporal bone (sides of head) • Inserts into the mandible and acts as a synergist of the masseter in closing the jaw • Buccinator (facial/chewing) • Runs horizontally across the cheek and inserts into the orbicularisoris • Presses cheeks against tongue teeth and lips (ie whistling), assists in chewing • Masseter (chewing) • Runs from cheekbone to lower jaw • Closes jaw by elevating the mandible (lower jaw)

6. Facial Muscles • Sternocleidomastoid (neck) • Originates from sternum and clavicle, inserts at mastoid process • Flexes the neck, rotates the head • Trapezius (neck/posterior trunk) • Runs from occipital bone down vertebral column to lower thoracic vertebrae • Extends the neck, elevates/depresses/adducts the scapula

7. Muscles of Trunk and Neck: Anterior muscles • Sternocleidomastoid • Paired muscles found on each side of the neck, arising from the sternum and clavicle. • inserts into the temporal bone • functions to rotate the head toward one side and to flex your neck

8. Muscles of Trunk and Neck: Anterior muscles • Pectoralis major • Large muscle covering the upper part of the chest • Origin is from the shoulder girdle and ribs; it inserts on the humerus • Adducts and flexes the arm

9. Muscles of Trunk and Neck: Anterior muscles • Intercostal muscles • Deep muscles found between the ribs • External intercostals = raise rib cage (breathing in) • Internal intercostals = depress rib cage (breathing out)

10. Muscles of Trunk and Neck: Anterior muscles • Rectus abdominus • Paired, medial, strap-like muscles; most superficial of abdomen; run from pubis to the rib cage  6-pack muscles! • Flexes the vertebral column (bending over) • Also compresses abdominal contents

11. Muscles of Trunk and Neck: Anterior muscles • External oblique • Paired, superficial muscles that make up the lateral walls of the abdomen • Fibers run downward and medially from the ribs and insert into the pelvis • Flexes vertebral column, rotates trunk, bends trunk laterally

12. Muscles of Trunk and Neck: Anterior muscles • Internal oblique • Deep to the external obliques; fibers run at right angles to the external obliques • Arises from iliac crest and inserts into the last three ribs • Functions = same as external obliques

13. Muscles of Trunk and Neck: Anterior muscles Deltoid (anterior/posterior) Triangular muscles which form the rounded shape of your shoulders Originates in shoulder girdle and inserts in proximal humerus Abducts arm (prime mover)

14. Muscles of Trunk and Neck: Anterior muscles • Transversus abdominus • Deepest muscle of the abdominal wall; fibers run horizontally • Arises from the lower ribs and iliac crest, inserts into the pubis • Compresses the abdominal contents

15. Muscles of Trunk and Neck: Posterior muscles Trapezius Most superficial muscles of the posterior neck & upper trunk; form a diamond-shaped muscle mass together Each runs from the occipital bone (back of head), down the vertebral column, and insert on the scapular spine and clavicle Shrugs the shoulders

16. Muscles of Trunk and Neck: Posterior muscles Latissimusdorsi Large, flat muscle pair that covers the lower back; originates in lower spine/ilium and inserts into the proximal end of the humerus Extends and adducts the humerus

17. Muscles of Trunk and Neck: Posterior muscles Erector spinae deep muscles of the back; muscle columns spanning the entire length of the vertebral column Help control the action of bending at the waist; are a common source of lower back pain