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Principle Skeletal Muscles 2. Muscles that act on the abdominal wall, muscles used in breathing and muscles that move the pectoral girdle. MUSCLES THAT ACT ON THE ANTERIOR ABDOMINAL WALL. The anterior abdominal wall is composed of skin, fascia and 4 pairs of muscles.
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Principle Skeletal Muscles 2 Muscles that act on the abdominal wall, muscles used in breathing and muscles that move the pectoral girdle
MUSCLES THAT ACT ON THE ANTERIOR ABDOMINAL WALL • The anterior abdominal wall is composed of skin, fascia and 4 pairs of muscles. • Tendinous Intersections – bands of connective tissue that divides the rectus abdominis • Linea Alba – tough fibrous band extending from xiphoid process to pubic symphysis
Rectus Abdominis • Origin – Pubis and Pubic Symphysis • Insertion – Costal Cartilage and Xiphoid Process • Action – Flexes vertebral column and compresses abdomen
Linea Alba Tendinous Intersections
External Oblique • Origin – Lower 8 ribs • Insertion – Crest of Ilium and Linea Alba • Action – Compresses abdomen, flexes vertebral column. Singularly rotates vertebral column
Internal Oblique • Origin – Ilium, inguinal ligament • Insertion – Costal Cartilage and linea alba • Action - Compresses abdomen, flexes vertebral column. Singularly rotates vertebral column
Transverse Abdominis • Origin – Ilium, inguinal ligament, lumbar fascia, and costal cartilage • Insertion – Xiphoid Process, linea alba and pubis • Action – Compress Abdomen
Muscles Used in Breathing • These muscles alter the size of the thoracic cavity so that breathing can occur. Inhalation occurs when the thoracic cavity increases in size and exhalation occurs when the thoracic cavity decreases in size
Diaphragm • Origin – xiphoid process, costal cartilage and lumbar vertebrae • Insertion – central tendon • Action – increases the vertical dimension of the thoracic cavity resulting in inhalation.
External and Internal Intercostals • Origin – ribs • Insertion – ribs • Action: • External – increases the anteroposterior and lateral dimensions of thoracic cage resulting in inhalation • Internal – decreases the antroposterior and lateral dimensions resulting in forceful exhalation
Muscles that Move the Pectoral Girdle • These muscles are divided into anterior (pectoralis minor and serratus anterior) and posterior (trapezius, levator scapulae and rhomboid major) thoracic muscles based on their location. • The main action of the muscles is to hold the scapula in place so that is can function as a stable origin for the muscles that move the humerus
Pectoralis minor • Origin – Ribs 3-5 • Insertion – Scapula • Action – depresses scapula, moves it laterally and forward
Serratus Anterior • Origin – Upper 8 or 9 ribs • Insertion – Scapula • Action – Moves scapula laterally and forward. AKA: “the boxer’s muscle” because it is important in horizontal arm movements like punching.
Trapezius • Origin – occipital bone, spines of C7 and thoracic vertebrae • Insertion – clavicle and scapula • Action – Elevates clavicle, moves scapula medially
Levator Scapulae • Origin – C1 – C5 • Insertion – Scapula • Action – elevates scapula
Rhomboid Major • Origin – Spines of T2-T5 • Insertion – Scapula • Action – Elevates scapula, moves it medially