BIOL110 Lecture Notes - Abductor Digiti Minimi Muscle Of Hand, Extensor Digiti Minimi Muscle, Hypothenar Eminence

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30 Jan 2013
Forearm and Hand
Key Points:
1. Each joint only allows certain movements
2. Movement occurs about an axis of rotation (= reference line thru a joint about which
movement occurs)
3. Position of muscles with relation to an axis of rotation allows you to know their effect
4. Prime movers = muscles that usually produce movement about an axis
5. Antagonists = muscles that oppose action of prime movers and stabilize joint
I. Elbow Joint (humero-ulnar & humero-radial joints)
a. Interlocking of bony surfaces => only flexion and extension
b. Ligaments restrain abduction/adduction
i. Medial: ulnar collateral ligament
ii. Lateral: annular ligament
c. Flexion is unrestrained; extension restrained by olecranon
d. Flexor M: Brachialis (primary), Biceps Brachii (primary), Brachoraidalis,
Pronator Teres
e. Extensor M: Triceps Brachii (posterior compartment)
II. Proximal/Distal Radio-Ulnar Joints
a. Radius = lateral (thumb side); Ulna = medial (pinky side)
b. Supination = palms face up; anatomical position = lateral rotation
i. Limited by ligaments between radius, ulna, and wrist
ii. Large size of biceps brachii => we are much stronger at supinating than at
pronating our forearm
iii. Muscles: Supinator, biceps brachii
c. Pronation = palms facing down/posterior = medial rotation
i. Medial rotation of humerus adds ~90 degrees to medial rotation
ii. Muscles: pronator teres, pronator quadratus
III. Wrist Joint (radiocarpal & intercarpal joints)
a. Flexion/Extension
i. Flexor Muscles
1. pass anterior to mediolateral axis
2. Muscles: Flexor carpi radialis, palmaris longus, flexor carpi
ii. Extensor Muscles
1. posterior to mediolateral axis
2. Muscles: extensor carpi radialis longus/ brevis, extensor carpi
b. Abduction/Adduction (occurs about anteroposterior axis)
i. Abduction (radial deviation)
1. Flexor carpi radialis, extensor carpi radialis longus/ brevis,
abductor pollicis longus
ii. Adduction (ulnar deviation)
1. flexor carpi ulnaris, extensor carpi ulnaris
iii. Palmaris Longus—NOT an abductor or adductor b/c it passes directly
thru the axis of rotation
IV. Carpometacarpal & Intermetacarpal Joints
a. Generally severely restricted in movement due to ligaments
b. NO muscles work on these joints except for digits 1 & 5
c. Digit 1 & 5 have opponens muscles which act to move digits in opposition
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