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PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky
The Muscular System
Part D
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
08
Muscles Crossing the Shoulder
 Nine muscles cross the shoulder joint and insert into
the humerus
 Prime movers include:
 Pectoralis major – arm flexion
 Latissimus dorsi and posterior fibers of the deltoid
– arm extension
 Middle fibers of the deltoid – arm abduction
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Muscles Crossing the Shoulder

Name: Pectoralis Major

Origin:


Insertion:


Sternum, clavicle, & 1st
to 6th rib
Proximal humerus
Primary action:

Adducts and flexes
humerus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles Crossing the Shoulder

Name: Latissimus Dorsi

Origin:


Insertion:


Lower spine and iliac
crest
Proximal humerus
Primary action:

Extends and adducts
humerous
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles crossing the shoulder


Name: Deltoid
Origin: clavicle, acromion,
spine of the scapula

Insertion: humerous

Primary action:

Flex, extend and adduct
humerous
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles Crossing the Shoulder
Figure 10.14a
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Muscles Crossing the Shoulder
Figure 10.14d
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles Crossing the Shoulder
 Rotator cuff muscles – supraspinatus, infraspinatus,
teres minor, and subscapularis
 Function mainly to reinforce the capsule of the
shoulder
 Secondarily act as synergists and fixators
 The coracobrachialis and teres major:
 Act as synergists
 Do not contribute to reinforcement of the shoulder
joint
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles crossing the shoulder
Name: Supraspinatus
Origin: Scapula
Insertion: Humerus
Primary action: abduct and
stabilize humerus
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Muscles crossing the shoulder
Name: Infraspinatus
Origin: Scapula
Insertion: Humerus
Primary action: Lateral
rotation of arm and
stabilizes humerus
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Muscles crossing the shoulder
Name: Teres minor
Origin: scapula
Insertion: humerus
Primary action: laterally rotates arm
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Muscles crossing the shoulder
Name: Subscapularis
Origin: Subscapular fossa
Insertion: humerus
Primary action: rotates
medially humerus;
stabilizes shoulder
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles crossing the shoulder
Name: coracobrachialis
Origin: coracoid process of
scapula
Insertion: medial humerus
Primary action: adducts
humerus , flexes the arm at
glenohumeral joint
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles crossing the shoulder
Name: Teres major
Origin: posterior aspect of the
inferior angle of the scapula
Insertion: Humerus
Primary action: Internal rotation
(medial rotation) of the humerus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles Crossing the Shoulder
Figure 10.14a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles Crossing the Shoulder
Figure 10.14d
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles Crossing the Shoulder
Figure 10.14c
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles Crossing the Elbow
 Forearm extension
 The triceps brachii is the prime mover of forearm
extension
 The anconeus is a weak synergist
 Forearm flexion
 Brachialis and biceps brachii are the chief forearm
flexors
 The brachioradialis acts as a synergist and helps
stabilize the elbow
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles crossing the elbow
Name: triceps brachii
Origin:
long head: infraglenoid tubercle of scapula
lateral head: posterior humerus
medial head: posterior humerus
Insertion: olecranon process of ulna
Primary action:
extends forearm, long head adducts shoulder
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Muscles crossing the elbow
Name: Anconeus
Origin: lateral epicondyle of the humerus
proximally
Insertion: lateral surface of the olecranon
process and the superior part of the
posterior ulna distally
Primary action:
assists in extension of the forearm
stabilizes the elbow during pronation and
supination
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Muscles crossing the elbow
Name: brachialis
Origin: anterior surface of the
distal end of humerus
Insertion: coronoid process and
the tuberosity of the ulna
Primary action: flexion at elbow
joint
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Muscles crossing the elbow
Name: biceps brachii
Origin:
–
short head: coracoid process of the scapula.
–
long head: supraglenoid tubercle
Insertion: radial tuberosity
Primary action: flexes elbow and supinates forearm
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles crossing the elbow
Name: brachioradialis
Origin: Lateral supracondylar ridge of
the humerus
Insertion: Distal radius (Radial styloid
process)
Primary action: flexion of forearm
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Muscles of the Forearm
 The two functional forearm muscle groups are: those that
cause wrist movement, and those that move the fingers and
the thumb
 These muscles insert via strong ligaments called flexor and
extensor retinacula
 Most anterior muscles are flexors, and posterior muscles are
extensors
 The pronator teres and pronator quadratus are not flexors,
but pronate the forearm
 The supinator muscle is a synergist with the biceps brachii
in supinating the forearm
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles of the Forearm: Anterior Compartment
 These muscles
are primarily
flexors of the
wrist and fingers
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Figure 10.15a
Muscles of the Forearm: Anterior Compartment
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Figure 10.15b, c
Muscles of the Forearm: Posterior Compartment
 These muscles
are primarily
extensors of the
wrist and fingers
Figure 10.16a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscles of the Forearm: Posterior Compartment
 These muscles are
primarily extensors
of the wrist and
fingers
Figure 10.16b
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Muscle Action of the Arm: Summary
 The posterior
extensor and anterior
flexor muscles are
shown
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Figure 10.17a
Muscle Action of the Forearm: Summary
 Posterior extensors of
the wrist and fingers,
and anterior flexor
muscles are shown
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 10.17b
Intrinsic Muscles of the Hand
 These small muscles:
 Lie in the palm of the hand (none on the dorsal
side)
 Move the metacarpals and fingers
 Control precise movements (e.g., threading a
needle)
 Are the main abductors and adductors of the
fingers
 Produce opposition – move the thumb toward the
little finger
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intrinsic Muscles of the Hand
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Figure 10.18a
Intrinsic Muscles of the Hand
Figure 10.18b
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Finger and Thumb Movements
 Flexion
 Thumb – bends medially along the palm
 Fingers – bend anteriorly
 Extension
 Thumb – points laterally
 Fingers – move posteriorly
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intrinsic Muscles of the Hand: Groups
 There are three groups of intrinsic hand muscles
 The thenar eminence (ball of the thumb) and
hypothenar eminence (ball of the little finger) –
each have a flexor, an abductor, and an opponens
muscle
 The midpalm muscles, the lumbricals and
interossei, extend the fingers
 The interossei also abduct and adduct the fingers
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intrinsic Muscles of the Hand: Groups
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 10.18c, d