Principle Skeletal Muscles 2

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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

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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

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Rectus Abdominis

• Origin Pubis and Pubic Symphysis
• Insertion Costal Cartilage and Xiphoid Process
• Action Flexes vertebral column and compresses
  abdomen

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Linea Alba
Tendinous Intersections
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External Oblique

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

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Internal Oblique

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

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Transverse Abdominis

• Origin Ilium, inguinal ligament, lumbar fascia,
  and costal cartilage
• Insertion Xiphoid Process, linea alba and pubis
• Action Compress Abdomen

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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

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Diaphragm

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

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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

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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

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Pectoralis minor

• Origin Ribs 3-5
• Insertion Scapula
• Action depresses scapula, moves it laterally
  and forward

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Serratus Anterior

• Origin Upper 8 or 9 ribs
• Insertion Scapula
• Action Moves scapula laterally and forward.
• AKA the boxers muscle because it is important
  in horizontal arm movements like punching.

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Trapezius

• Origin occipital bone, spines of C7 and
  thoracic vertebrae
• Insertion clavicle and scapula
• Action Elevates clavicle, moves scapula medially

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Levator Scapulae

• Origin C1 C5
• Insertion Scapula
• Action elevates scapula

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Rhomboid Major

• Origin Spines of T2-T5
• Insertion Scapula
• Action Elevates scapula, moves it medially