the muscular system part d

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Human Anatomy & Physiology, Sixth EditionElaine N. Marieb

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky

08The Muscular System

Part D


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



Name: Pectoralis Major Origin:

Sternum, clavicle, & 1st to 6th rib

Insertion: Proximal humerus

Primary action: Adducts and flexes

humerus


Name: Latissimus Dorsi Origin:

Lower spine and iliac crest

Insertion: Proximal humerus

Primary action: Extends and adducts

humerous



Muscles crossing the shoulder

Name: Deltoid Origin: clavicle, acromion,

spine of the scapula Insertion: humerous

Primary action: Flex, extend and adduct

humerous



Figure 10.14a



Figure 10.14d



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



Name: Supraspinatus

Origin: Scapula

Insertion: Humerus

Primary action: abduct and stabilize humerus



Name: Infraspinatus

Origin: Scapula

Insertion: Humerus

Primary action: Lateral rotation of arm and stabilizes humerus


Name: Teres minor

Origin: scapula

Insertion: humerus

Primary action: laterally rotates arm



Name: Subscapularis

Origin: Subscapular fossa

Insertion: humerus

Primary action: rotates medially humerus; stabilizes shoulder



Name: coracobrachialis

Origin: coracoid process of scapula

Insertion: medial humerus

Primary action: adducts humerus , flexes the arm at glenohumeral joint



Name: Teres major

Origin: posterior aspect of the inferior angle of the scapula

Insertion: Humerus

Primary action: Internal rotation (medial rotation) of the humerus




Figure 10.14a



Figure 10.14d



Figure 10.14c


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


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


Muscles crossing the elbowName: 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



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



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



Name: brachioradialis

Origin: Lateral supracondylar ridge of the humerus

Insertion: Distal radius (Radial styloid process)

Primary action: flexion of forearm


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


Muscles of the Forearm: Anterior Compartment

These muscles are primarily flexors of the wrist and fingers

Figure 10.15a


Muscles of the Forearm: Anterior Compartment

Figure 10.15b, c


Muscles of the Forearm: Posterior Compartment

These muscles are primarily extensors of the wrist and fingers

Figure 10.16a


Muscles of the Forearm: Posterior Compartment

These muscles are primarily extensors of the wrist and fingers

Figure 10.16b


Muscle Action of the Arm: Summary

Figure 10.17a

The posterior extensor and anterior flexor muscles are shown


Muscle Action of the Forearm: Summary

Figure 10.17b

Posterior extensors of the wrist and fingers, and anterior flexor muscles are shown


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



Figure 10.18a



Figure 10.18b


Finger and Thumb Movements

Flexion

Thumb – bends medially along the palm

Fingers – bend anteriorly

Extension

Thumb – points laterally

Fingers – move posteriorly


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


Intrinsic Muscles of the Hand: Groups

Figure 10.18c, d

the muscular system part d

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