Anterolateral Abdominal Wall
Consists of four pairs of muscles converging at the anterior midline:
External Obliques
Internal Obliques
Transversus Abdominis
Rectus Abdominis
Each muscle group has specific traits and functions as highlighted in the following table:
Movement:
Twisting at waist; bending to the side (External & Internal Obliques)
Squeezing abdomen during forceful exhalations, defecation, urination, and childbirth (Transversus Abdominis)
Sitting up; bending to the side (Rectus Abdominis)
Target Motion Direction:
External Obliques: Vertebral column lateral flexion
Internal Obliques: Compression of abdominal cavity
Transversus Abdominis: Flexion of vertebral column
Rectus Abdominis: Lateral flexion of vertebral column
Prime Mover:
External Obliques: External obliques, Internal obliques
Transversus Abdominis: Transversus abdominis
Rectus Abdominis: Rectus abdominis, Quadratus lumborum
Origin/Inserts:
External Obliques: Ribs 5-12; iliac crest
Internal Obliques: Ilium; ribs 7-10
Transversus Abdominis: Ilium; ribs 5-10
Rectus Abdominis: Pubis; ribs 5-7 (via the costal cartilage)
External Oblique: Superficial layer, extends inferiorly and medially.
Internal Oblique: Middle layer, extending superiorly and medially.
Transversus Abdominis: Deepest layer, arranged transversely.
Linea Alba: Fibrous band joining at the anterior midline enclosing rectus abdominis.
Rectus Abdominis: Long muscles segmented by collagen bands, contributing to "six-pack abs."
Formed by lumbar vertebrae, iliac bones, psoas major, iliacus, and quadratus lumborum.
Essential for posture and core stability.
Role in Breathing: Alter thoracic cavity size during inhalation and exhalation.
Movement:
Inhalation/Exhalation: Compression and expansion of thoracic cavity.
Prime Mover:
Diaphragm for inhalation, External and Internal Intercostals for both inhalation and exhalation.
Origin/Inserts:
Diaphragm: Originates from sternum, ribs 6-12, lumbar vertebrae; inserts into central tendon.
Intercostals: External (superior to ribs), Internal (inferior to ribs).
Dome-shaped muscle separating thoracic and abdominal cavities.
Critical for breathing by modifying thoracic cavity volume.
Works with abdominal muscles for functions like defecation and urination (Valsalva maneuver).
Central Tendon: Fuses with pericardial sac and pleura.
Openings in Diaphragm:
Caval Opening: For inferior vena cava.
Esophageal Hiatus: For esophagus and nerves.
Aortic Hiatus: For aorta, thoracic duct, and azygous vein.
Three sets (External, Internal, Innermost) aiding in breathing by changing rib cage dimensions.
External Intercostals: Aid in inhalation by expanding rib cage.
Internal Intercostals: Assist in exhalation by constricting rib cage.
Innermost Intercostals: Work synergistically with internal intercostals for effective exhalation.