1. Principle Skeletal Muscles 2
Muscles that act on the abdominal wall, muscles used in breathing and muscles that move the pectoral girdle

2. 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

3. Rectus Abdominis Origin – Pubis and Pubic Symphysis
Insertion – Costal Cartilage and Xiphoid Process
Action – Flexes vertebral column and compresses abdomen

4. Linea Alba
Tendinous Intersections

5. External Oblique Origin – Lower 8 ribs
Insertion – Crest of Ilium and Linea Alba
Action – Compresses abdomen, flexes vertebral column. Singularly rotates vertebral column

7. Internal Oblique Origin – Ilium, inguinal ligament
Insertion – Costal Cartilage and linea alba
Action - Compresses abdomen, flexes vertebral column. Singularly rotates vertebral column

9. Transverse Abdominis
Origin – Ilium, inguinal ligament, lumbar fascia, and costal cartilage
Insertion – Xiphoid Process, linea alba and pubis
Action – Compress Abdomen

12. 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

13. Diaphragm
Origin – xiphoid process, costal cartilage and lumbar vertebrae
Insertion – central tendon
Action – increases the vertical dimension of the thoracic cavity resulting in inhalation.

15. 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

17. 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

18. Pectoralis minor Origin – Ribs 3-5 Insertion – Scapula
Action – depresses scapula, moves it laterally and forward

20. 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.

22. Trapezius Origin – occipital bone, spines of C7 and thoracic vertebrae
Insertion – clavicle and scapula
Action – Elevates clavicle, moves scapula medially

24. Levator Scapulae Origin – C1 – C5 Insertion – Scapula
Action – elevates scapula

25. Rhomboid Major Origin – Spines of T2-T5 Insertion – Scapula
Action – Elevates scapula, moves it medially