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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
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*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+
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+*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 limb is in motion+
−**draws head and neck ventrally when limb is fixed+
+*Origin: transverse processes of the atlas
−*Insertion: acromion and distal spine of the scapula
−*Action: advancing the limb
−*Innervation
−*The '''broadest muscle of the back'''+
−*Origin: thoracolumbar fascia +*Insertion: teres tuberosity of the humerus+
−*Actions: antagonist to the brachiocephalic m.+**cranial fibers strap scapula to the chest+
−**retracts free limb and flexes shoulder joint+**draws trunk forward over the fixed limb+
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+'''''Pectoral mm.''''': brachial plexus+*Two superficial parts, cranial and caudal
−**Origin: cranial sternum
−**Insertion:
−***cranial ('''descending'''): crest of the humerus distal to the deltoid tuberosity
−***caudal ('''transverse'''): covers 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
−***draw trunk forward when limb is fixed
−*Origin: C4 to 10th rib+
−*Insertion: medial scapula and scapular cartilage+*Action: supporting the weight of the trunk+
−**reinforced by strong fascia+**cervical portion can retract the limb+
−**caudal portion can advance the limb+
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+*Origin: nuchal ligament, 4th - 6th thoracic spine+
−*Insertion: dorsal border and adjacent scapula+*Action: retracting the limb, may also raise limb+
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+*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: 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): Axillary n. of the brachial plexus+
−**'''Deltoids'''+***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'''+***Origin: dorsal part of the caudal scapula +
−***Insertion: teres tuberosity midway down humerus+
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+''Extensors'': Radial n. from the brachial plexus
−*'''Triceps brachii''': Has four heads in the dog
−**Long head: caudal margin of the scapula
−**Lateral, medial, and accessory heads: shaft of the humerus
−**Insertion: olecranon, protected by tricipital bursa against the bone and subcutaneous bursa against the skin
−*'''Tensor fasciae antebrachii'''
−**Origin: tendon and lateral surface of the latissimus dorsi
+''Flexors'': Musculocutaneous n. from the brachial plexus+*'''Biceps brachii'''
−**Origin: supraglenoid tubercle of the scapula
−**Insertion: medial tuberosity of proximal radius and adjacent ulna
−**Runs through the intertubercular groove of the humerus
−*'''Brachialis'''
−**Origin: proximocaudal humerus
−**Insertion: spirals to insert just proximal to biceps
''Supinators'': Radial n. from the brachial plexus
−*'''Brachioradialis'''
−**Origin: lateral epicondyle of the humerus
−**Insertion: distal part of medial radius
−**Often much reduced and sometimes absent
−*'''Supinator'''
−**Deep to extensor muscles, passing from lateral humeral epicondyles to upper medial radius
−*'''Pronator teres'''+
−**Origin: medial epicondyle of the humerus+**Insertion: dorsal surface and medial border of radius+
−*'''Pronator quadratus'''+**Origin: palmar surface of radius and interosseous ligament+
−**Insertion: interosseous border of the ulna+
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+''Extensors'': Radial n. from the brachial plexus
−*Craniolateral position on the forearm
−*Almost all originate from the lateral epicondyle of the humerus
−*'''Extensor carpi radialis''': most medial, inserts on middle metacarpal bone
−*'''Ulnaris lateralis''': 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 dew caw
−*'''Lateral Digital Extensor'''
−**Insertion: dorsal proximal phalanges of 3rd to 5th digit
−*Caudal position on the forearm+
−*Originate from the caudal medial epicondyle of the humerus+*'''Flexor carpi radialis''': most medial, inserts on upper 2nd/3rd metacarpal bone+
−*'''Flexor carpi ulnaris''': 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 carpal canal before branching and continues to palmar distal phalanges+
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+''Interosseus muscles''+*Support metacarpophalnageal joints
−*Arise from palmar proximal metacarpal bones and insert on sesamoid bones within the joints, continued by ligaments to phalanges
==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==