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Muscles of The Body Part B

Explore the intricate muscles of the thorax, abdomen, and pelvic floor, including their functions and actions, innervation, and anatomical relationships. Dive into detailed diagrams and learn about key muscle groups and their importance in bodily functions.

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Muscles of The Body Part B

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  1. Muscles of The Body Part B • Adapted 2014-2015 H. Biology II • Muscles of the Thorax • Muscles of the back

  2. Muscles of the Thorax • Muscles of respiration • External intercostals—more superficial muscles that elevate ribs for inspiration • Internal intercostals—deeper muscles that aid forced expiration • Diaphragm • Partition between thoracic and abdominal cavities • Most important muscle in inspiration • Innervated by phrenic nerves

  3. External intercostal (a) Internal intercostal Figure 10.10a

  4. Xiphoid process of sternum Foramen for inferior vena cava Foramen for esophagus Costal cartilage Central tendon of diaphragm Diaphragm Foramen for aorta Lumbar vertebra 12th rib Quadratus lumborum Psoas major (b) Figure 10.10b

  5. Muscles of the Abdominal Wall • Four paired muscles; their fasciae and aponeuroses form the lateral and anterior abdominal wall • Internal obliques • External obliques • Transversus abdominis • Rectus abdominis

  6. Pectoralis major Serratus anterior Linea alba Tendinous intersection Transversus abdominis Internal oblique Rectus abdominis External oblique Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) Aponeurosis of the external oblique (a) Figure 10.11a

  7. Muscles of the Abdominal Wall • Fascicles of these muscles run at angles to one another, providing added strength • All are innervated by intercostal nerves • Actions of these muscles • Lateral flexion and rotation of the trunk • Help promote urination, defecation, childbirth, vomiting, coughing, and screaming

  8. Rectus abdominis Internal oblique External oblique Lumbar fascia IIiac crest Pubic tubercle Lumbar fascia Transversus abdominis Inguinal ligament (b) Figure 10.11b

  9. Muscles of the Pelvic Floor • Pelvic floor (pelvic diaphragm) is composed of two paired muscles • Levator ani • Coccygeus • Both are innervated by sacral nerves

  10. Muscles of the Pelvic Floor • Functions of the pelvic diaphragm • Seals the inferior outlet of the pelvis • Supports pelvic organs • Lifts pelvic floor to help release feces • Resists increased intra-abdominal pressure

  11. Muscles of the Perineum • Urogenital diaphragm • Anterior half of perineum, inferior to pelvic floor • Deep transverse perineal muscle • External urethral sphincter (voluntary control of urination)

  12. Anterior Symphysis pubis Pubococcygeus Levator ani IIiococcygeus Urogenital diaphragm Urethra Vagina Anal canal Obturator internus Coccyx Levator ani Piriformis Coccygeus Pelvic diaphragm Posterior (a) Figure 10.12a

  13. Urethral opening External urethral sphincter Vaginal opening Inferior pubic ramus Deep transverse perineal muscle Central tendon Anus External anal sphincter Male Female (b) Figure 10.12b

  14. Muscles of the Perineum • Muscles of superficial perineal space • Ischiocavernosus • Bulbospongiosus • Superficial transverse perineal muscles • External anal sphincter (in posterior half of perineum)

  15. Urethral opening Clitoris Vaginal opening Anus Penis Midline raphe Ischiocavernosus Bulbospongiosus Superficial transverse perineal muscle Levator ani Gluteus maximus Female Male (c) Figure 10.12c

  16. Superficial Muscles of the Thorax • Most are extrinsic shoulder muscles • Act in combination to fix the shoulder girdle (mostly the scapula) and move it to increase range of arm movements • Actions include elevation, depression, rotation, lateral and medial movements, protraction, and retraction • Two groups of muscles: anterior and posterior

  17. Superficial Muscles of the Thorax • Anterior extrinsic shoulder muscles • Pectoralis minor • Serratus anterior • Subclavius • (Pectoralis major considered later with muscles that act on the humerus)

  18. Subclavius Sternocleido- mastoid Clavicle Subscapularis Deltoid Pectoralis minor Pectoralis major Coracobrachialis Sternum Serratus anterior Biceps brachii Humerus (a) Figure 10.13a

  19. Superficial Muscles of the Posterior Thorax • Posterior extrinsic shoulder muscles • Trapezius • Levator scpulae • Rhomboids (major and minor) • (Latissimus dorsi considered later with muscles that act on the humerus)

  20. Levator scapulae Trapezius Supraspinatus Clavicle Deltoid Spine of scapula Rhomboid minor Infraspinatus Teres minor Rhomboid major Teres major Humerus Latissimus dorsi (c) Figure 10.13c

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