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CHAPTER # 10(b)
THE MUSCULAR SYSTEM
(ANATOMY)
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
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External
intercostal
(a)
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Internal
intercostal
Figure 10.10a
Muscles of the Thorax
PLAY
A&P Flix™: External intercostals
PLAY
A&P Flix™: Internal intercostals
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Xiphoid process of sternum
Foramen for inferior
vena cava
Central
tendon of
diaphragm
Foramen
for aorta
12th rib
(b)
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Foramen for
esophagus
Costal cartilage
Diaphragm
Lumbar
vertebra
Quadratus
lumborum
Psoas major
Figure 10.10b
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
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Pectoralis major
Serratus anterior
Linea alba
Transversus abdominis
Internal oblique
External oblique
Aponeurosis of the
external oblique
(a)
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Tendinous
intersection
Rectus
abdominis
Inguinal ligament
(formed by free
inferior border of
the external oblique
aponeurosis)
Figure 10.11a
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
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Rectus
abdominis
Internal
oblique
External
oblique
IIiac crest
Pubic
tubercle
Transversus
abdominis
Inguinal
ligament
Lumbar
fascia
Lumbar
fascia
(b)
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Figure 10.11b
Muscles of the Abdominal Wall
PLAY
A&P Flix™: External obliques
PLAY
A&P Flix™: Internal obliques
PLAY
A&P Flix™: Rectus abdominis
PLAY
A&P Flix™: Transversus abdominis
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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)
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Anterior
Levator
ani
Symphysis pubis
Urogenital diaphragm
Urethra
Vagina
Anal canal
Pubococcygeus
IIiococcygeus
Obturator
internus
Coccyx
Levator ani
Coccygeus
Piriformis
(a)
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Posterior
Pelvic
diaphragm
Figure 10.12a
Urethral
opening
External urethral
sphincter
Inferior pubic ramus
Deep
transverse
perineal
muscle
Central tendon
Vaginal
opening
Anus
External anal
sphincter
(b)
Male
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Female
Figure 10.12b
Muscles of the Perineum
• Muscles of superficial perineal space
• Ischiocavernosus
• Bulbospongiosus
• Superficial transverse perineal muscles
• External anal sphincter (in posterior half of
perineum)
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Urethral
opening
Vaginal
opening
Clitoris
Anus
Penis
Midline raphe
Ischiocavernosus
Bulbospongiosus
Superficial
transverse
perineal muscle
Levator ani
Gluteus maximus
(c)
Male
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Female
Figure 10.12c
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
A&P Flix™: Muscles that act on the shoulder joint
and humerus: An overview (a)
PLAY
A&P Flix™: Muscles that act on the shoulder joint
and humerus: An overview (b)
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PLAY
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)
PLAY
A&P Flix™: Muscles of the pectoral girdle (a)
PLAY
A&P Flix™: Muscles of the pectoral girdle (b)
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Sternocleidomastoid
Subclavius
Clavicle
Subscapularis
Pectoralis minor
Deltoid
Pectoralis
major
Sternum
Coracobrachialis
Serratus anterior
Biceps brachii
Humerus
(a)
PLAY
A&P Flix™: Muscles that act on the shoulder joint
and humerus: An overview (b)
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Figure 10.13a
Superficial Muscles of the Thorax
PLAY
A&P Flix™: Pectoralis minor
PLAY
A&P Flix™: Serratus anterior
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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)
PLAY
A&P Flix™: Muscles of the pectoral girdle (c)
PLAY
A&P Flix™: Movement of the pectoral girdle
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Levator
scapulae
Trapezius
Supraspinatus
Clavicle
Deltoid
Rhomboid
minor
Rhomboid
major
Spine of
scapula
Infraspinatus
Teres minor
Teres major
Humerus
Latissimus
dorsi
(c)
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Figure 10.13c
Superficial Muscles of the Posterior Thorax
PLAY
A&P Flix™: Trapezius
PLAY
A&P Flix™: Levator scapula
PLAY
A&P Flix™: Rhomboid major
PLAY
A&P Flix™: Rhomboid minor
Copyright © 2010 Pearson Education, Inc.