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Canine Forelimb - Anatomy & Physiology (view source)
Revision as of 14:40, 14 January 2011
, 14:40, 14 January 2011no edit summary
==Structures of the Proximal Forelimb and Shoulder==
==Structures of the Proximal Forelimb and Shoulder==
===[[Forelimb - Anatomy & Physiology#Humerus|Humerus]]===
===[[Forelimb - Anatomy & Physiology#Humerus|Humerus]]===
The Humerus is the long bone of the forearm, articulating with the scapula to form the shoulder and the radius and ulna to form the elbow. In situ, it lies obliquely along the ventral thorax and is more horizontal in larger species. The greater tubercle is not seperated into two parts like in other species. In dogs and cats, it articulates with the ulna medially via a trochlea and the radius laterally via a '''capitulum'''.
The Humerus is the long bone of the forearm, articulating with the scapula to form the shoulder and the radius and ulna to form the elbow. In situ, it lies obliquely along the ventral thorax and is more horizontal in larger species. The greater tubercle is not separated into two parts like in other species. In dogs and cats, it articulates with the ulna medially via a '''trochlea''' and the radius laterally via a '''capitulum'''.
===[[Forelimb - Anatomy & Physiology#Radius|Radius]]===
===[[Forelimb - Anatomy & Physiology#Radius|Radius]]===
A radial tuberosity provides a site of attachment for brachialis and biceps brachii. This roughened area is very variable in size in dogs and can be non-exsistent.
A radial tuberosity provides a site of attachment for brachialis and biceps brachii mm. This roughened area is very variable in size in dogs and can be non-existent.
===[[Forelimb - Anatomy & Physiology#Ulna|Ulna]]===
===[[Forelimb - Anatomy & Physiology#Ulna|Ulna]]===
===[[Forelimb - Anatomy & Physiology#Shoulder Joint|Shoulder Joint]]===
===[[Forelimb - Anatomy & Physiology#Shoulder Joint|Shoulder Joint]]===
The joint capsule barely extends past the areas of articulation, except where it continues distally into the intertubercular groove of the humerus. This provides cushioning and synovial support for the bicipital tendon. The bicipital tendon and the joint capsule pouch are held in place by the '''transverse humeral retinaculum''', which lies between the greater and lesser tubercles of the humerus.
===[[Forelimb - Anatomy & Physiology#Elbow Joint|Elbow Joint]]===
===[[Forelimb - Anatomy & Physiology#Elbow Joint|Elbow Joint]]===
The radius articulates with the capitulum and lateral trochlear surface of the humeral condyle. Whilst the medial part articulates with the trochlear notch of the ulna. To allow the radius to rotate slightly the radial head has a marginal band of cartilage making the articular circumference. It faces the radial notch of the ulna between the medial and lateral coronoid processes. The joint capsule runs from just proximal to the articular surface of the condyle of the humerus to the periphery of the olecranon fossa; it pouches between the ulna and radius, and under the tendinous attachments of some muscles.
'''Collateral ligaments''' are paired and lie medially and laterally. They both attach proximally to the epicondyle and distally to the tuberosities of the radius and ulna.
'''Annular ligament''' of the radius attaches to the sides of the coronoid process of the ulna. This runs deep to the collateral ligaments and forms a ring for the radial head to turn in during pronation and supination.
The radius and ulna are joined mid-shaft by the '''interosseous ligament''', the remainder is filled by the interosseous membrane.
==Structures of the Distal Forelimb==
==Structures of the Distal Forelimb==
===[[Forelimb - Anatomy & Physiology#Carpal Joint|Carpal Joint]]===
===[[Forelimb - Anatomy & Physiology#Carpal Joint|Carpal Joint]]===
The '''synovial membranes''' form three compartments corresponding to each joint. The proximal is the largest whilst the middle carpal and carpometacarpal sacs communicate and extend into the intermetacarpal articulations. The fibrous joint capsule is common to all three joints, and attaches to the individual bones and various intercarpal ligaments. The '''extensor retinaculum''' is fibrous collagenous tissue on the dorsal aspect that allows passage of the extensor tendons. On the palmar aspect lies the '''palmar carpal fibrocartilage''', that provides attachment for some metacarpal bones. Paired '''collateral ligaments''' bridge the sides of the three main articulations.
The '''synovial membranes''' form three compartments corresponding to each joint. The proximal is the largest whilst the middle carpal and carpometacarpal sacs communicate and extend into the intermetacarpal articulations. The fibrous joint capsule is common to all three joints and attaches to the individual bones and various intercarpal ligaments. The '''extensor retinaculum''' is fibrous collagenous tissue on the dorsal aspect that allows passage of the extensor tendons. On the palmar aspect lies the '''palmar carpal fibrocartilage''', that provides attachment for some metacarpal bones. Paired '''collateral ligaments''' bridge the sides of the three main articulations.
The '''flexor retinaculum''' is the carpal fascia on the palmar aspect, and lies between the accessory carpal bone and the medial aspect of the carpus. This with the joint capsule and medial surface of the accesory carpal bone, makes up the '''carpal canal'''. It houses just the deep digital flexor tendon in the dog. The intermetacarpal joints, are tight joints between the proximal ends of the metacarpals. The joint capsules are continuous with that of the carpal joint. They are held together by the '''interosseous metacarpal ligaments'''.
The '''flexor retinaculum''' is the carpal fascia on the palmar aspect, and lies between the accessory carpal bone and the medial aspect of the carpus. This with the joint capsule and medial surface of the accessory carpal bone, makes up the '''carpal canal'''. It houses just the deep digital flexor tendon in the dog. The intermetacarpal joints, are tight joints between the proximal ends of the metacarpals. The joint capsules are continuous with that of the carpal joint. They are held together by the '''interosseous metacarpal ligaments'''.
==Muscles of the Forelimb==
==Muscles of the Forelimb==
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''''':
:Innervated by: Accessory n.
Origin: mid-dorsal raphe and supraspinous ligament.
:Origin: mid-dorsal raphe and supraspinous ligament
:Insertion: spine of the scapula
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.
Body: two parts, cervical and thoracic separated by aponeurosis.
Action: raises scapula against the trunk and swings cranially to advance the limb.
'''''Serratis ventralis''''': branch of brachial plexus.
'''''Brachiocephalic m.''''':
:Innervated by: 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.
Origin: C4 to 10th rib.
'''''Omotransversarius''''':
:Innervated by: Accessory n.
:Origin: transverse processes of the atlas
:Insertion: acromion and distal spine of the scapula
:Action: advancing the limb
Insertion: medial scapula and scapular cartilage.
'''''Latissimus dorsi''''':
:Innervated by: local branch of brachial plexus
:It is 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.
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.
'''''Pectoral mm.''''':
:Innervated by: 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 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.
'''''Rhomboids''''': brachial plexus
'''''Serratis ventralis''''':
:Innervated by: 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.
Origin: nuchal ligament, 4th - 6th thoracic spine.
'''''Rhomboids''''':
:Innervated by: brachial plexus
Insertion: dorsal border and adjacent scapula.
:Origin: nuchal ligament, 4th - 6th thoracic spine
:Insertion: dorsal border and adjacent scapula
Action: retracting the limb, may also raise limb.
:Action: retracting the limb, may also raise limb.
===[[Forelimb - Anatomy & Physiology#Intrinsic Musculature|Intrinsic Musculature]]===
===[[Forelimb - Anatomy & Physiology#Intrinsic Musculature|Intrinsic Musculature]]===
These muscles are grouped:
These muscles are grouped:
'''Lateral'''
<u>'''Lateral'''</u>
Action: fixator.
'''''Supraspinatus''''' and '''''Infraspinatus''''':
:Innervated by: 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.
'''Caudal (Flexors)'''
<u>'''Medial'''</u>
'''''Deltoids''''': Axillary n. of the brachial plexus.
'''''Supscapularis''''':
:Innervated by: 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
Origin: acromion, the length of the scapular spine.
'''''Coracobrachialis''''':
:Innervated by: Musculocutaneous n. of the brachial plexus
:Origin: medial supraglenoid tubercle
:Insertion: proximal shaft of the humerus
:Action: fixator
<u>'''Caudal (Flexors)'''</u>
Action: Flexor of Shoulder, Abductor and outward rotator of the arm.
'''''Deltoids''''':
:Innervated by: 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.
'''''Teres Major''''':
:Innervated by: Axillary n. of the brachial plexus
Origin: dorsal part of the caudal scapula.
:Origin: dorsal part of the caudal scapula
:Insertion: teres tuberosity midway down humerus
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'''
<u>1. '''Extensors''' </u>
'''''Biceps brachii''''': Musculocutaneous n. from the brachial plexus.
'''''Triceps brachii''''':
:Innervated by: Radial n. from the brachial plexus
:Has four heads in the dog
:Origin:
::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
Origin: supraglenoid tubercle of the scapula.
'''''Tensor fasciae antebrachii''''':
:Innervated by: Radial n. from the brachial plexus
:Origin: tendon and lateral surface of the latissimus dorsi
<u>2. '''Flexors'''</u>
Runs through the intertubercular groove of the humerus.
'''''Biceps brachii''''':
:Innervated by: 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.
'''''Brachialis''''':
:Innervated by: Musculocutaneous n. from the brachial plexus
Origin: proximocaudal humerus.
:Origin: proximocaudal humerus
:Insertion: spirals to insert just proximal to biceps
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]]====
1. '''Supinators'''
<u>1. '''Supinators'''</u>
Origin: medial epicondyle of the humerus.
'''''Brachioradialis''''':
:Innervated by: 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''''':
:Innervated by: Radial n. from the brachial plexus
:Deep to the extensor muscles, passing from the lateral humeral epicondyles to the upper medial radius
'''''Pronator quadratus''''': Median n. from the brachial plexus.
<u>2. '''Pronators'''</u>
Origin: palmar surface of radius and interosseous ligament.
'''''Pronator teres''''':
:Innervated by: Median n. from the brachial plexus
:Origin: medial epicondyle of the humerus
:Insertion: dorsal surface and medial border of radius
Insertion: interosseous border of the ulna.
'''''Pronator quadratus''''':
:Innervated by: 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]]====
1.'''Extensors'''
<u>1.'''Extensors'''</u>
They are located at the 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'''''
'''''Extensor carpi radialis'''''
:The most medial, inserts on middle metacarpal bone.
The most medial, inserts on middle metacarpal bone.
'''''Ulnaris lateralis'''''
'''''Ulnaris lateralis'''''
:The most lateral, inserts on accessory carpal bone and 5th metacarpal.
The most lateral, inserts on accessory carpal bone and 5th metacarpal.
'''''Extensor carpi obliquus''''' (aka '''''abductor pollicis longus''''')
'''''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'''''
'''''Common Digital Extensor'''''
:Insertion: extensor process of the distal phalanx of each digit
Insertion: extensor process of the distal phalanx of each digit.
:Sends a medial branch to the dew caw.
Sends a medial branch to the dew caw.
'''''Lateral Digital Extensor'''''
'''''Lateral Digital Extensor'''''
:Inserts on the dorsal proximal phalanges of the 3rd to 5th digit.
2. '''Flexors'''
<u>2. '''Flexors'''</u>
They are at the caudal position on the forearm, originate from the caudal medial epicondyle of the humerus and all are innervated by the median or ulnar n. of the brachial plexus.
'''''Flexor carpi radialis'''''
'''''Flexor carpi radialis'''''
:The most medial, inserts on the upper 2nd/3rd metacarpal bone.
The most medial, inserts on the upper 2nd/3rd metacarpal bone.
'''''Flexor carpi ulnaris'''''
'''''Flexor carpi ulnaris'''''
:The most lateral, inserts on the accessory carpal bone.
The most lateral, inserts on the accessory carpal bone.
'''''Superficial Digital Flexor'''''
'''''Superficial Digital Flexor'''''
:It divides into four branches, which insert on the middle phalanges of all digits.
It divides into four branches, which insert on the middle phalanges of all digits.
'''''Deep Digital Flexor'''''
'''''Deep Digital Flexor'''''
:Passes through the carpal canal before branching, and continues to the palmar distal phalanges.
Passes through the carpal canal before branching, and continues to the palmar distal phalanges.
'''''Interosseus muscles'''''
'''''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.
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==
'''[[Lymphatics of the Forelimb - Anatomy & Physiology|Lymphatics of the Forelimb]]'''
'''[[Lymphatics of the Forelimb - Anatomy & Physiology|Lymphatics of the Forelimb]]'''
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