Lesson 26: Anterior Axio-Appendicular Muscles and the Axilla

Introduction

• Focus on the axilla (armpit area)
• Examine location, organization, and details of anterior axio-appendicular muscles
• Discuss pathways of nerves for these muscles
• Identify and describe axilla borders and contents

Objectives

• Identify contributing anterior axio-appendicular muscles
• Describe muscle organization, attachments, innervation, and actions
• Identify and describe axilla borders (Apex, base, four walls)
• Understand structures passing through the axilla, focusing on the brachial plexus

Review of Posterior Axio-Appendicular Muscles

• List of five posterior muscles: Trapezius, Latissimus Dorsi, Levator Scapulae, Rhomboid Minor, Rhomboid Major
• Characteristics: Attach to axial and appendicular skeleton, superficial to deep fascia, control upper limb movement
• Innervation via anterior rami of spinal nerves (except Trapezius)
• Comparison with anterior muscles:
  • Anterior muscles originate from thoracic cage
  • Located on anterior-lateral body (pectorals and lateral thoracic wall)
  • Innervated by anterior rami, primarily branches of brachial plexus

Anterior Axio-Appendicular Muscles

Pectoralis Major

• Broad attachment, two heads (clavicular and sternal-costal)
• Actions: Adduction, medial rotation, flexion, special extension from flexed position
• Innervation: Medial and lateral pectoral nerves
• PLT mnemonic for insertion: Pectoralis Major (Lateral lip), Latissimus Dorsi (Floor), Teres Major (Medial lip)

Pectoralis Minor

• Originates from ribs 3-5, inserts on coracoid process of scapula
• Actions: Stabilization and protraction of scapula
• Innervation: Medial and lateral pectoral nerves

Serratus Anterior

• Originates from ribs 1-8, inserts on medial border of scapula
• Actions: Stabilizes scapula, protraction, upward rotation (boxer’s muscle)
• Innervation: Long thoracic nerve

Borders of the Axilla

• Apex: Cervical axillary canal, bounded by clavicle, rib 1, and superior scapula
• Base: Skin and fascia of the armpit
• Walls:
  • Anterior: Pectoralis Major and Minor
  • Posterior: Subscapularis, Teres Major, Latissimus Dorsi
  • Medial: Serratus Anterior and thoracic cage
  • Lateral: Humerus

Contents of the Axilla

• Axillary artery and vein
• Brachial plexus
• Lymphatic vessels and nodes
• Adipose tissue for protection

Activities

• Identify axilla structures and walls in laboratory schematic
• List structures contributing to axilla borders
• Practice identifying origin and insertion on osteology

These notes summarize key points from the lecture on the organization of anterior axio-appendicular muscles and the structure of the axilla. Focus on understanding muscle functions, innervation, and the anatomy of the axilla for further study and lab work.