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Canine Forelimb - Anatomy & Physiology (view source)
Revision as of 14:15, 9 January 2011
, 14:15, 9 January 2011→Muscles of the Forelimb
==Muscles of the Forelimb==
==Muscles of the Forelimb==
===[[Forelimb - Anatomy & Physiology#Extrinsic Musculature|Extrinsic Musculature]]===
===[[Forelimb - Anatomy & Physiology#Extrinsic Musculature|Extrinsic Musculature]]===
These muscle are responsible for joining the forelimb to the trunk, forming a synsarcosis rather than a conventional joint. Collectively, they act to transfer the weight of the body to the forelimbs as well as stabilize the scapula.
These muscle are responsible for joining the forelimb to the trunk, forming a synsarcosis rather than a conventional joint. Collectively, they act to transfer the weight of the body to the forelimbs as well as stabilize the scapula.
'''''Trapezius''''': Accessory n.
'''''Trapezius''''': Accessory n.
Origin: mid-dorsal raphe and supraspinous ligament.
Insertion: spine of the scapula.
Body: two parts, cervical and thoracic separated by aponeurosis.
Action: raises scapula against the trunk and swings cranially to advance the limb.
'''''Brachiocephalic m.''''': Accessory n.
'''''Brachiocephalic m.''''': Accessory n.
There are two parts separated by the clavicle.
Origin: clavicle.
Insertion: median raphe of the neck and the occipital bone. The ventral part attaches to the mastoid process.
Actions: advances the limb and extends the shoulder joint when the limb is in motion; draws the head and neck ventrally when the limb is fixed.
'''''Omotransversarius''''': Accessory n.
'''''Omotransversarius''''': Accessory n.
'''''Latissimus dorsi''''': local branch of brachial plexus
Origin: transverse processes of the atlas.
Insertion: acromion and distal spine of the scapula.
Action: advancing the limb.
'''''Latissimus dorsi''''': local branch of brachial plexus.
The broadest muscle of the back.
Origin: thoracolumbar fascia.
Insertion: teres tuberosity of the humerus.
Actions: antagonist to the brachiocephalic m. It retracts the free limb and flexes the shoulder joint. It also draws the trunk forward over the fixed limb.
'''''Pectoral mm.''''': brachial plexus.
Two superficial parts; cranial and caudal.
Origin: cranial sternum.
'''''Serratis ventralis''''': branch of brachial plexus
Insertion: Cranial ('''descending'''): crest of the humerus distal to the deltoid tuberosity. Caudal ('''transverse'''): covers the elbow joint to insert on the medial fascia of the forearm.
Action: adduct the forelimb, assist in protraction and retraction.
One deep part ('''pectoralis profundus'''), with cranial and caudal parts.
Origin: ventral sternum and adjacent cartilage
Insertions: cranial (subclavius): supraspinatus m. Caudal (pectoralis ascendens): lesser tubercle of the humerus.
Actions: slinging trunk between forelimbs, may also retract free limbs. It draws the trunk forward when the limb is fixed.
'''''Serratis ventralis''''': branch of brachial plexus.
Origin: C4 to 10th rib.
Insertion: medial scapula and scapular cartilage.
Action: supporting the weight of the trunk. It is reinforced by strong fascia. The cervical portion can retract the limb and the caudal portion can advance the limb.
'''''Rhomboids''''': brachial plexus
'''''Rhomboids''''': brachial plexus
Origin: nuchal ligament, 4th - 6th thoracic spine.
Insertion: dorsal border and adjacent scapula.
Action: retracting the limb, may also raise limb.
===[[Forelimb - Anatomy & Physiology#Intrinsic Musculature|Intrinsic Musculature]]===
===[[Forelimb - Anatomy & Physiology#Intrinsic Musculature|Intrinsic Musculature]]===
====Muscles of the Shoulder====
====Muscles of the Shoulder====
These muscles are grouped:
These muscles are grouped:
'''Lateral'''
'''''Supraspinatus''''' and '''''Infraspinatus''''', Suprascapular n. of the brachial plexus.
Origin: the fossae of the scapula.
Insertion: both tubercles of the humerus.
Action: brace the shoulder.
Clinical significance: the bursa between the tendon of the infraspinatus and lateral tubercle of the humerus, can be the site of inflammation.
'''Medial'''
'''''Supscapularis''''': Subscapular n. from the brachial plexus.
Origin: Deep surface of the scapula.
Insertion: medial tubercle of the humerus.
Action: braces medial shoulder joint, potential adductor.
'''''Coracobrachialis''''': Musculocutaneous n. of the brachial plexus.
Origin: medial supraglenoid tubercle.
Insertion: proximal shaft of the humerus.
Action: fixator.
'''Caudal (Flexors)'''
'''''Deltoids''''': Axillary n. of the brachial plexus.
Origin: acromion, the length of the scapular spine.
Insertion: deltoid tuberosity on the humerus, fascia of the lateral arm.
Action: Flexor of Shoulder, Abductor and outward rotator of the arm.
'''''Teres Major''''': Axillary n. of the brachial plexus.
Origin: dorsal part of the caudal scapula.
Insertion: teres tuberosity midway down humerus.
====[[Forelimb - Anatomy & Physiology#Muscles of the Elbow|Muscles of the Elbow]]====
====[[Forelimb - Anatomy & Physiology#Muscles of the Elbow|Muscles of the Elbow]]====
1. '''Extensors'''
'''''Triceps brachii''''': Radial n. from the brachial plexus.
Has four heads in the dog.
Long head: From the caudal margin of the scapula.
Lateral, medial, and accessory heads: From the shaft of the humerus.
Insertion: olecranon, protected by tricipital bursa against the bone, and subcutaneous bursa against the skin.
'''''Tensor fasciae antebrachii''''': Radial n. from the brachial plexus.
Origin: tendon and lateral surface of the latissimus dorsi.
2. '''Flexors'''
'''''Biceps brachii''''': Musculocutaneous n. from the brachial plexus.
Origin: supraglenoid tubercle of the scapula.
Insertion: medial tuberosity of proximal radius and adjacent ulna.
Runs through the intertubercular groove of the humerus.
'''''Brachialis''''': Musculocutaneous n. from the brachial plexus.
Origin: proximocaudal humerus.
Insertion: spirals to insert just proximal to biceps.
====[[Forelimb - Anatomy & Physiology#Muscles of Supination and Pronation|Muscles of Supination and Pronation]]====
====[[Forelimb - Anatomy & Physiology#Muscles of Supination and Pronation|Muscles of Supination and Pronation]]====
''Pronators'': Median n. from the brachial plexus
1. '''Supinators'''
'''''Brachioradialis''''': Radial n. from the brachial plexus.
Origin: lateral epicondyle of the humerus.
Insertion: distal part of the medial radius.
Often much reduced, and sometimes absent.
'''''Supinator''''': Radial n. from the brachial plexus.
Deep to the extensor muscles, passing from the lateral humeral epicondyles to the upper medial radius.
2. '''Pronators'''
'''''Pronator teres''''': Median n. from the brachial plexus.
Origin: medial epicondyle of the humerus.
Insertion: dorsal surface and medial border of radius.
'''''Pronator quadratus''''': Median n. from the brachial plexus.
Origin: palmar surface of radius and interosseous ligament.
Insertion: interosseous border of the ulna.
====[[Forelimb - Anatomy & Physiology#Muscles of the Carpal and Digital Joints|Muscles of the Carpal and Digital Joints]]====
====[[Forelimb - Anatomy & Physiology#Muscles of the Carpal and Digital Joints|Muscles of the Carpal and Digital Joints]]====
''Flexors'': Median or Ulnar n. of the brachial plexus
1.'''Extensors'''
Craniolateral position on the forearm. They almost all originate from the lateral epicondyle of the humerus and are all innervated by the radial n. from the brachial plexus.
'''''Extensor carpi radialis'''''
The most medial, inserts on middle metacarpal bone.
'''''Ulnaris lateralis'''''
The most lateral, inserts on accessory carpal bone and 5th metacarpal.
'''''Extensor carpi obliquus''''' (aka '''''abductor pollicis longus''''')
Origin: cranial radius.
Insertion: 1st metacarpal.
Last two may also serve in medial deviation of the paw.
'''''Common Digital Extensor'''''
Insertion: extensor process of the distal phalanx of each digit.
Sends a medial branch to the dew caw.
'''''Lateral Digital Extensor'''''
Inserts on the dorsal proximal phalanges of the 3rd to 5th digit.
2. '''Flexors'''
Caudal position on the forearm. Originate from the caudal medial epicondyle of the humerus and all innervated by the median or ulnar n. of the brachial plexus
'''''Flexor carpi radialis'''''
The most medial, inserts on the upper 2nd/3rd metacarpal bone.
'''''Flexor carpi ulnaris'''''
The most lateral, inserts on the accessory carpal bone.
'''''Superficial Digital Flexor'''''
It divides into four branches, which insert on the middle phalanges of all digits.
'''''Deep Digital Flexor'''''
Passes through the carpal canal before branching, and continues to the palmar distal phalanges.
'''''Interosseus muscles'''''
Support the metacarpophalnageal joints. They arise from the palmar proximal metacarpal bones, and insert on the sesamoid bones within the joints. They are continued by ligaments to the phalanges.
==Vasculature of the Forelimb==
==Vasculature of the Forelimb==