PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College
C H A P T E R
Copyright © 2010 Pearson Education, Inc.
10
The Muscular System: Part B
Copyright © 2010 Pearson Education, Inc.
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
Copyright © 2010 Pearson Education, Inc. Figure 10.10a
Externalintercostal
(a) Internalintercostal
Copyright © 2010 Pearson Education, Inc. Figure 10.10b
Foramen foresophagusCostal cartilage
Lumbarvertebra
Xiphoid process of sternum
Diaphragm
Quadratuslumborum Psoas major
Foramen for inferiorvena cava
Centraltendon ofdiaphragm
Foramenfor aorta
12th rib
(b)
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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
Copyright © 2010 Pearson Education, Inc. Figure 10.11a
Transversus abdominis
Internal oblique
External oblique
Aponeurosis of theexternal oblique
(a)
Pectoralis major
Linea alba
Tendinousintersection
Rectusabdominis
Inguinal ligament(formed by free inferior border of the external oblique aponeurosis)
Serratus anterior
Copyright © 2010 Pearson Education, Inc.
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
Copyright © 2010 Pearson Education, Inc. Figure 10.11b
Transversusabdominis
Inguinalligament
Lumbarfascia
Lumbarfascia
Internaloblique
Pubictubercle
Rectusabdominis
Externaloblique
(b)
IIiac crest
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Muscles of the Pelvic Floor
• Pelvic floor (pelvic diaphragm) is composed of two paired muscles
• Levator ani
• Coccygeus
• Both are innervated by sacral nerves
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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
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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)
Copyright © 2010 Pearson Education, Inc. Figure 10.12a
Pelvicdiaphragm
Symphysis pubis
(a)
Levator aniPiriformis
Posterior
Anterior
Coccyx
Coccygeus
Obturatorinternus
IIiococcygeusLevatorani
PubococcygeusUrogenital diaphragm
UrethraVaginaAnal canal
Copyright © 2010 Pearson Education, Inc. Figure 10.12b
Inferior pubic ramus
External urethralsphincter
Urethralopening
Vaginalopening
Deeptransverseperineal muscleCentral tendon
Anus
External analsphincter
Male(b) Female
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Muscles of the Perineum
• Muscles of superficial perineal space
• Ischiocavernosus
• Bulbospongiosus
• Superficial transverse perineal muscles
• External anal sphincter (in posterior half of perineum)
Copyright © 2010 Pearson Education, Inc. Figure 10.12c
Male Female
PenisMidline rapheIschiocavernosus
ClitorisUrethralopening
Anus Vaginalopening
BulbospongiosusSuperficialtransverseperineal muscle
Levator ani
(c)
Gluteus maximus
Copyright © 2010 Pearson Education, Inc.
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
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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)
Copyright © 2010 Pearson Education, Inc. Figure 10.13a
Subclavius
Clavicle
SubscapularisPectoralis minor
Coracobrachialis
Serratus anterior
Humerus
Sternocleido-mastoid
DeltoidPectoralismajor Sternum
Biceps brachii
(a)
Copyright © 2010 Pearson Education, Inc.
Superficial Muscles of the Posterior Thorax
• Posterior extrinsic shoulder muscles
• Trapezius
• Levator scapulae
• Rhomboids (major and minor)
• (Latissimus dorsi considered later with muscles that act on the humerus)
Copyright © 2010 Pearson Education, Inc. Figure 10.13c
Trapezius
(c)
Levatorscapulae
Supraspinatus
Clavicle
Spine ofscapula
InfraspinatusTeres minor
Humerus
Deltoid
Teres major
Latissimusdorsi
RhomboidminorRhomboidmajor