Difference between revisions of "Bovine Forelimb - Anatomy & Physiology"

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<big><center>[[Musculoskeletal System - Anatomy & Physiology|'''BACK TO MUSCULOSKELETAL ANATOMY AND PHYSIOLOGY''']]</center></big>
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<big><center>[[Forelimb - Anatomy & Physiology|'''BACK TO FORELIMB''']]</center></big>
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==Structures of the Proximal Forelimb and Shoulder==
−
 
 
−
 
 
−
==Common structures of the Proximal Forelimb and Shoulder==
 
  
 
===Scapula===
 
===Scapula===
  
−
The Scapula forms the basis of the shoulder region, providing points of attachment of extrinsic and intrinsic muscles.  It is held in place by a synsarcosis of muscles and does not form a conventional articulation with the trunk.
+
The ox possesses a small '''tuber scapular''', it has an '''acromion''' present and has extensive scapular cartilage.
−
*In ungulates, the dorsal border is extended by a scapular cartilage, which enlarges the area for muscle attachment.  This ossifies with age.
 
−
*The bone is roughly triangular, with a prominent '''spine''' that can be palpated through the skin
 
−
*The spine defines '''Infraspinous''' and '''Supraspinous''' '''Fossae''', inhabited by muscles accordingly
 
−
*The spine serves as a point of attachment for the '''trapezius''' muscle
 
−
*The spine culminates in the '''acromion''' in all but the horse and pig
 
−
*Medial muscle attachment comprises mostly of the '''subscapularis''', with the '''serratus ventralis''' attaching dorsally
 
−
*The Scapula articulates with the humerus at the '''Glenoid cavity'''
 
−
 
 
−
===Clavicle===
 
−
 
 
−
The Clavicle is all but absent in most domestic species, with the notable exception of the avian skeleton.  In the dog and cat, a remnant of bone may remain embedded in the fibrous intersection in the brachiocephalicus, which may prove misleading in radiographic images.
 
  
 
===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 humerus is essentially the same conformation as that of the dog.
  
−
*The head of the humerus comprises '''greater''' and '''lesser tubercles''', separated by an '''intertubercular groove''' through which runs the tendon of the '''biceps brachii'''
+
===Radius and Ulna===
−
*The shaft of the humerus takes on a characteristically twisted shape via a groove carrying the '''brachialis''' and '''radial nerve'''
 
−
*Laterally, the '''deltoid tuberosity''' is palpable through the skin and connects to the head of the humerus via a ridge and merges distally with the '''crest of the humerus'''
 
−
*Distally, the humerus culminates in a '''condyle''' which articulates to form the elbow
 
−
**In large animals, it meets the radius via a '''trochlea'''
 
−
**In dogs and cats, it articulates with the radius medially via a trochlea and the ulna laterally via a '''capitulum'''
 
−
**Caudally, all species show an '''olecranon fossa''' which articulates with the '''olecranon''' of the ulna
 
−
*Medial and lateral epicondyles provide attachment for flexors and extensors of the carpus and digits
 
  
−
 
+
These are complete bones in the ox but are entirely fused. There is a proximal and distal '''interosseous space''' which are the only two places where the shafts are separated. The ulna's proximal end is caudal to the radius and its distal end forms the '''lateral styloid process''', distal to the radius and articulating with the ulnar carpal bone.
−
===Radius===
 
−
 
 
−
While in the human the radius and ulna are separated by an interosseus space and articulate only at their extremities, allowing for significant capability of supination and pronation, these movements are much more limited in domestic animals due to the gradual fusing of the two bones. The extreme case is exhibited by the horse. 
 
−
 
 
−
*The Radius forms the shaft-like rod of the distal limb, which is bowed to varying degrees amont species
 
−
*The radius articulates proximally with the distal humerus, caudally with the ulna, and distally with the carpus
 
−
*Medially on the distal articular process, a '''styloid process''' projects, which is mirrored laterally by the ulna
 
−
 
 
−
===Ulna===
 
−
 
 
−
The Ulna's greatest contribution to functional anatomy is in the formation of the '''Olecranon''', or the point of the elbow, which gives rise to the attachment of the '''triceps'''.  The olecranon articulates with the humerus via its anconeal process.  Distally (where unfused), the '''lateral styloid process''' articulates with the '''ulnar carpal bone'''.
 
  
 
==Joints of the Proximal Forelimb==
 
==Joints of the Proximal Forelimb==
 
===Shoulder Joint===
 
===Shoulder Joint===
  
−
The shoulder joint links the humerus and the scapula at the '''glenoid cavity''', which is much smaller than the head of the humerus. While structually it is a [[Joints - Anatomy & Physiology#Types of Joints|'''ball and socket''']] joint, it functions as a [[Joints - Anatomy & Physiology#Types of Joints|'''hinge joint''']] due to extensive muscling around the articulation.  The joint capsule is enlarged and extends under the tendon of the biceps, acting as a synovial sheath to protect the tendon.
+
The joint capsule attaches a very short distance from the periphery of the articular surfaces. The '''intertubercular (bicipital) bursa''' lies between the humeral tubercles cushioning the bicipital tendon. The bursa and tendon are held in place by the '''transverse humeral retinaculum''', running between the greater and lesser tubercles of the humerus.
  
 
===Elbow Joint===
 
===Elbow Joint===
  
−
Movement of the elbow joint is restricted to the [[Planes and Axes - Anatomy & Physiology|sagittal plane]].  It is bounded medially and laterally by collateral ligaments betweek the humerus and radius, caudally by the olecranon ligament between the humerus and olecranon, and further enforced by the annular radial ligament.  The elbow is a compound joint including:
+
The joint capsule attaches to the articular surface of the condyle, the periphery of the '''olecranon fossa''' and the articular  cartilage of the '''trochlear notch of the ulna'''. It fuses with the collateral ligaments. Paired collateral ligaments attach the epicondyles to the tuberosities of the radius and ulna.
−
*The [[Joints - Anatomy & Physiology#Types of Joints|'''hinge joint''']] between the humerus and the radius and ulna
 
−
*The [[Joints - Anatomy & Physiology#Types of Joints|'''pivot joint''']] between the radius and ulna
 
−
*The point of the elbow, or the '''olecranon''' is formed by the anconeal process of the ulna inserting into the olecranon fossa of the humerus
 
  
 +
==Structures of the Distal Forelimb==
  
 +
===Carpal bones===
  
−
==Common Structures of the Distal Forelimb==
+
The carpal bones comprise two rows:
−
 
 
  
−
===Carpal bones===
+
'''Proximally''' (mediolaterally), radial, intermediate, ulnar and accessory bones.
  
−
Carpal bones comprise two rows:
+
'''Distally''', 1st is missing, 2 and 3 are fused and there is also a 4th carpal bone.
−
*Proximally, (mediolaterally), radial, intermediate, ulnar and accessory bones
 
−
**The accessory bone serves as a landmark for palpation
 
−
*Distally, bones are numbered 1-5, though 5 is always fused with 4
 
−
*A small [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|'''sesamoid''']] bone embedded in the medial tissues of the joint can sometimes be mistaken as a chip fracture
 
  
 
===Metacarpal bones===
 
===Metacarpal bones===
  
−
The number of metacarpals varies widely among species, as the demand for their function changes: '''plantigrade''', or flat-footed, animals requiring the full complement of five metacarpal bones; the number is reduced in the upright stature of '''digitigrade''' animals such as the dog and cat, and shows the extreme in '''unguligrades''' like the horse, who depends entirely on the third metacarpal bone for its stature.
+
These are covered in detail in the [[Bovine Lower Limb - Anatomy & Physiology|bovine lower limb]] section.
−
*Colloquially, the third metacarpal of the horse is known as the '''canon''' bone, and the vestigial 2 and 4 as '''splint bones'''
 
  
 
==Joints of the Distal Forelimb==
 
==Joints of the Distal Forelimb==
Line 80: Line 41:
  
 
The carpal joint is a compound joint composed of:
 
The carpal joint is a compound joint composed of:
−
*The '''antebrachiocarpal joint''' between the radius/ulna and the proximal carpal bones
 
−
*The '''middle carpal joint''' between the two rows of carpal bones
 
−
*The '''carpometacarpal joint''' between the distal carpal bones and the proximal metacarpals
 
  
−
The joint is a synovial joint, comprised of a common outer fibrous capsule and three inner synovial pouches, one for each joint.  Numerous ligaments add to the stability of the joint and ensure movement is largely limited to the [[Planes and Axes - Anatomy & Physiology|sagittal plane]], although no collateral ligaments exist in the dog between the radius and the proximal metacarpals.  This allows a very small amount of rotation.
+
1. The '''antebrachiocarpal joint''' between the radius/ulna and the proximal carpal bones.
  
−
===Metacarpal Joint===
+
2. The '''middle carpal joint''' between the two rows of carpal bones.
−
 
 
−
The metacarpal joint is defined by the presence of palmar [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|'''sesamoids''']], which allow the flexor tendons to pass over the sharp change in angle presented by the joint.  These are paired on each digit, with the exception of the first digit where it exists.
 
  
 +
3. The '''carpometacarpal joint''' between the distal carpal bones and the proximal metacarpals.
  
 +
The joint is a synovial joint, consisting of a common outer fibrous capsule and three inner synovial pouches, one for each joint. '''Collateral ligaments''' extend from the radius to the metacarpal bones on the medial and lateral aspect of the carpus. The carpal canal houses both the deep digital flexor tendon, and the deep branch of the superficial digital flexor.
  
 
==Muscles of the Forelimb==
 
==Muscles of the Forelimb==
 
===Extrinsic Musculature===
 
===Extrinsic Musculature===
  
−
These muscle are responsible for joining tht 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''''':
−
*Origin: mid-dorsal raphe and supraspinous ligament
+
:Innervated by: Accessory n.
−
*Insertion: spine of the scapula
+
:Origin: mid-dorsal raphe and supraspinous ligament.
−
*Body: two parts, cervical and thoracic separated by aponeurosis
+
:Insertion: spine of the scapula.
−
*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.
  
−
'''''Brachiocephalic m.''''': Accessory n.
+
'''''Brachiocephalic m.''''':
−
*Two parts separated by the clavicle where it exists
+
:Innervated by: Accessory n.
−
*Origin: clavicle or vestigial fibrous intersection
+
:The two parts are separated by the clavicle, where it exists.
−
*Insertion: several places on the head and neck
+
:Origin: occipital bone, nuchal ligament and the mastoid process.
−
*Actions:  
+
:Insertion: deltoid tuberosity and fascia of the limb.
−
**advances the limb and extends the shoulder joint when limb is in motion
+
:Actions: advances the limb and extends the shoulder joint when limb is in motion. Draws the head and neck ventrally when the limb is fixed.
−
**draws head and neck ventrally when limb is fixed
 
  
−
'''''Omotransversarius''''': Accessory n.
+
'''''Omotransversarius''''':
−
*Origin: transverse processes of the atlas
+
:Innervated by: Accessory n.
−
*Insertion: acromion and adjacent scapula
+
:Origin: transverse processes of the atlas.
−
*Action: advancing the limb
+
:Insertion: acromion and spine of scapula.
−
*Innervation
+
:Action: advancing the limb.
  
−
'''''Latissimus dorsi''''': local branch of brachial plexus
+
'''''Latissimus dorsi''''':
−
*The '''broadest muscle of the back'''
+
:Innervated by: local branch of brachial plexus
−
*Origin: thoracolumbar fascia  
+
:The broadest muscle of the back.
−
*Insertion: teres tuberosity of the humerus
+
:Origin: thoracolumbar fascia.
−
*Actions: antagonist to the brachiocephalic m.
+
:Insertion: teres tuberosity of the humerus.
−
**cranial fibers strap scapula to the chest
+
:Actions: antagonist to the brachiocephalic m. The cranial fibers strap the scapula to the chest. It retracts the free limb and flexes shoulder joint. It draws the trunk forward over the fixed limb.
−
**retracts free limb and flexes shoulder joint
 
−
**draws trunk forward over the fixed limb
 
  
−
'''''Pectoral mm.''''': brachial plexus
+
'''''Pectoral mm.''''':
−
*Two superficial parts, cranial and caudal
+
:Innervated by: brachial plexus
−
**Origin: cranial sternum
+
:Two superficial parts, cranial and caudal, these aren't very distinct in the ox.
−
**Insertion:
+
:Origin: cranial sternum.
−
***cranial ('''descending'''): crest of the humerus distal to the deltoid tuberosity
+
:Insertion:  
−
***caudal ('''transverse'''): covers elbow joint to insert on the medial fascia of the forearm
+
::cranial ('''descending'''), crest of the humerus distal to the deltoid tuberosity.
−
**Action: adduct the forelimb, assist in protraction and retraction
+
::caudal ('''transverse'''): covers elbow joint to insert on the medial fascia of the forearm.
−
*One deep part ('''pectoralis profundus'''), with cranial and caudal parts
+
:Action: adduct the forelimb and assist in protraction and retraction.  
−
**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
 
  
−
'''''Serratis ventralis''''': branch of brachial plexus
+
'''''Serratis ventralis''''':
−
*Origin: C4 to 10th rib
+
:Innervated by: branch of the brachial plexus.
−
*Insertion: medial scapula and scapular cartilage
+
:Origin: C4 to 10th rib.
−
*Action: supporting the weight of the trunk
+
:Insertion: medial scapula and scapular cartilage.
−
**reinforced by strong fascia
+
: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.
−
**cervical portion can retract the limb
 
−
**caudal portion can advance the limb
 
  
−
'''''Rhomboids''''': brachial plexus, although in some species, dorsal spinal nerves can innervate
+
'''''Rhomboids''''':
−
*Origin: median connective tissue from poll to withers, lying deep to the trapezius
+
:Innervated by: brachial plexus
−
*Insertion: dorsal border and adjacent scapula
+
:Origin: nuchal ligament.
−
*Action: retracting the limb, may also raise limb
+
:Insertion: dorsal border and adjacent scapula.
 +
:Action: retracting the limb, may also raise the limb.
  
 
===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: 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: caudal border and spine of the scapula
 
−
****One head in the horse and two in species with an acromion (site of second origin)
 
−
***Insertion: deltoid tuberosity on the humerus
 
−
**'''Teres Major'''
 
−
***Origin: dorsal part of the caudal scapula
 
−
***Insertion: teres tuberosity midway down humerus
 
−
**'''Teres Minor'''
 
−
*There are no defined extensors of the shoulder.  Those involved (brachiocephalic m., biceps brachii, supraspinatus, and ascending pectorals) have other, more primary roles.
 
  
−
====Muscles of the Elbow====
+
===1. Lateral===
−
''Extensors'': Radial n. from the brachial plexus
+
 
−
*'''Triceps brachii''': Three heads, four in the dog
+
'''''Supraspinatus''''' and '''''Infraspinatus''''':
−
**Long head: caudal margin of the scapula
+
:Innervated by: Suprascapular n. of the brachial plexus.
−
**Lateral, medial, and accessory heads: shaft of the humerus
+
:Origin: the fossae of the scapula.
−
**Insertion: olecranon, proteced by tricipital bursa against the bone and subcutaneous bursa against the skin
+
:Insertion: both tubercles of the humerus.
−
*'''Tensor fasciae antebrachii'''
+
:Action: brace the shoulder.
−
**Overlies triceps extending from scapula to olecranon
+
:Clinical significance: bursa between the tendon of the infraspinatus and lateral tubercle of the humerus can be the site of inflammation.
−
*'''Anconeus'''
+
 
−
**Origin: distal humerus
+
===2. Medial===
−
**Insertion: lateral olecranon
+
 
 +
'''''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.
 +
 
 +
'''''Coracobrachialis''''':  
 +
:Innervated by: Musculocutaneous n. of the brachial plexus.
 +
:Origin: medial supraglenoid tubercle.
 +
:Insertion: proximal shaft of the humerus.
 +
:Action: fixator.
 +
 
 +
===3. Caudal (Flexors)===
 +
 
 +
'''''Deltoids''''':
 +
:Innervated by: Axillary n. of the brachial plexus.
 +
:Origin: Two heads of origin; the caudal border and spine of the scapula and the acromion.
 +
:Insertion: deltoid tuberosity on the humerus.
 +
:Action: Flexor of Shoulder.
 +
 
 +
'''''Teres Major''''':
 +
:Innervated by: Axillary n. of the brachial plexus.
 +
:Origin: dorsal part of the caudal scapula.
 +
:Insertion: teres tuberosity midway down humerus.
 +
 
 +
'''''Teres Minor''''':
 +
:Innervated by: Axillary n. of the brachial plexus.
 +
 
  
−
''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 next to biceps
 
  
−
====Muscles of Supination and Pronation ====
+
There are no defined extensors of the shoulder. Those involved (brachiocephalic m., biceps brachii, supraspinatus, and ascending pectorals) have other, more primary roles.
−
''Supinators'': Radial n. from the brachial plexus
 
−
*'''Brachioradialis'''
 
−
**Origin: lateral epicondyle of the humerus
 
−
**Insertion: distal medial forearm within superficial fascia
 
−
**Prominent in the cat but nearly absent in the dog
 
−
*'''Supinator'''
 
−
**Deep to extensor muscles,  passing from lateral humeral epicondyles to upper medial radius
 
  
−
''Pronators'': Median n. from the brachial plexus
 
−
*'''Pronator teres''': only functional in cat and dog
 
−
**Origin: medial epicondyle of the humerus
 
−
**Insertion: supinator
 
−
*'''Pronator quadratus''': only found in carnivores
 
−
**Origin: shaft of the ulna
 
−
**Insertion: shaft of the radius
 
  
−
====Muscles of the Carpal and Digital Joints====
 
−
''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 2nd/3rd metacarpal bone
 
−
*'''Ulnaris lateralis''': most lateral, inserts on accessory carpal bone
 
−
*'''Extensor carpi obliquus''': aka '''abductor pollicis longus'''
 
−
**Origin: cranial radius
 
−
**Insertion: most medial metacarpal bone
 
−
*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 dewlcaw and medial digits in all but horse and cat
 
−
*'''Lateral Digital Extensor'''
 
−
**Insertion: dorsal proximal phalanx
 
  
−
''Flexors'': Median or Ulnar n. of the brachial plexus
+
==Muscles of the Elbow==
−
*Caudal position on the forearm
 
−
*Originate from the caaudal 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'''
 
−
**Branches according to the number of digis and inserts in proximal interphalangeal joint
 
−
*'''Deep Digital Flexor'''
 
−
**Passes through carpal canal before branching and continues to palmar distal phalanges
 
  
−
''Interosseus muscles''
+
===Extensors===
−
*Support metacarpophalnageal joints
 
−
*Arise from palmar proximal metacarpal bones and insert on sesamoid bones within the joints, continued by ligaments to phalanges
 
  
 +
'''''Triceps brachii''''':
 +
:Innervated by: Radial n. from the brachial plexus
 +
:Has three heads, the medial branch is the most developed. The long head is at the caudal margin of the scapula; The lateral, medial, and accessory heads are at the shaft of the humerus.
 +
:Insertion: olecranon, proteced by tricipital bursa against the bone and subcutaneous bursa against the skin.
 +
 +
'''''Tensor fasciae antebrachii''''':
 +
:Innervated by: Radial n. from the brachial plexus.
 +
:Overlies the triceps extending from the scapula to the olecranon.
 +
 +
===Flexors===
 +
 +
'''''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. It runs through the intertubercular groove of the humerus.
 +
 +
'''''Brachialis''''':
 +
:Innervated by: Musculocutaneous n. from the brachial plexus.
 +
:Origin: proximocaudal humerus.
 +
:Insertion: spirals to insert next to biceps.
 +
 +
==Muscles of the Carpal and Digital Joints==
 +
 +
===Extensors===
 +
 +
All have innervation from the radial n. from the brachial plexus. They have a craniolateral position on the forearm and almost all of them originate from the lateral epicondyle of the humerus.
 +
 +
'''''Extensor carpi radialis'''''
 +
:The most medial, inserts on 2nd/3rd metacarpal bone.
 +
 +
'''''Ulnaris lateralis'''''
 +
:The most lateral, inserts on accessory carpal bone.
 +
 +
'''''Extensor carpi obliquus''''' (aka- abductor pollicis longus)
 +
:Origin: cranial radius.
 +
:Insertion: most medial metacarpal bone .
 +
 +
'''''Common Digital Extensor'''''
 +
:Insertion: extensor process of the distal phalanx of each digit.
 +
 +
'''''Lateral Digital Extensor'''''
 +
:Insertion: dorsal proximal phalanges.
 +
 +
'''''Medial Digital Extensor'''''
 +
:Insertion: middle and distal phalanges.
 +
 +
===Flexors===
 +
 +
All innervated by the median or ulnar n. of the brachial plexus. Have a caudal position on the forearm and originate from the caudal medial epicondyle of the humerus.
 +
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'''''Flexor carpi radialis'''''
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:The most medial, inserts on upper 2nd/3rd metacarpal bone.
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'''''Flexor carpi ulnaris'''''
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:The most lateral, inserts on the accessory carpal bone.
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'''''Superficial Digital Flexor'''''
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:Insertion: palmar surface of middle phalanges.
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'''''Deep Digital Flexor'''''
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:Passes through carpal canal before branching and continues to palmar distal phalanges.
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'''''Interosseus muscles'''''
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:This is covered in more detail in the [[Bovine Lower Limb - Anatomy & Physiology|bovine lower limb]] section.
  
 
==Vasculature of the Forelimb==
 
==Vasculature of the Forelimb==
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*'''[[Arteries of the Forelimb - Anatomy & Physiology|Arteries of the Forelimb]]'''
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*'''[[Veins of the Forelimb - Anatomy & Physiology|Veins of the Forelimb]]'''
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Click here for information on:
−
*'''[[Lymphatics of the Forelimb - Anatomy & Physiology|Lymphatics of the Forelimb]]'''
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 +
'''[[Arteries of the Forelimb - Anatomy & Physiology|Arteries of the Forelimb]]'''
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'''[[Veins of the Forelimb - Anatomy & Physiology|Veins of the Forelimb]]'''
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'''[[Lymphatics of the Forelimb - Anatomy & Physiology|Lymphatics of the Forelimb]]'''
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==Webinars==
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<rss max="10" highlight="bovine lameness arthritis feet">https://www.thewebinarvet.com/orthopaedics/webinars/feed</rss>
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[[Category:Musculoskeletal System - Anatomy & Physiology]][[Category:Musculoskeletal Anatomy - Cattle]]
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[[Category:A&P Done]]

Latest revision as of 19:34, 27 October 2022


Structures of the Proximal Forelimb and Shoulder

Scapula

The ox possesses a small tuber scapular, it has an acromion present and has extensive scapular cartilage.

Humerus

The humerus is essentially the same conformation as that of the dog.

Radius and Ulna

These are complete bones in the ox but are entirely fused. There is a proximal and distal interosseous space which are the only two places where the shafts are separated. The ulna's proximal end is caudal to the radius and its distal end forms the lateral styloid process, distal to the radius and articulating with the ulnar carpal bone.

Joints of the Proximal Forelimb

Shoulder Joint

The joint capsule attaches a very short distance from the periphery of the articular surfaces. The intertubercular (bicipital) bursa lies between the humeral tubercles cushioning the bicipital tendon. The bursa and tendon are held in place by the transverse humeral retinaculum, running between the greater and lesser tubercles of the humerus.

Elbow Joint

The joint capsule attaches to the articular surface of the condyle, the periphery of the olecranon fossa and the articular cartilage of the trochlear notch of the ulna. It fuses with the collateral ligaments. Paired collateral ligaments attach the epicondyles to the tuberosities of the radius and ulna.

Structures of the Distal Forelimb

Carpal bones

The carpal bones comprise two rows:

Proximally (mediolaterally), radial, intermediate, ulnar and accessory bones.

Distally, 1st is missing, 2 and 3 are fused and there is also a 4th carpal bone.

Metacarpal bones

These are covered in detail in the bovine lower limb section.

Joints of the Distal Forelimb

Carpal Joint

The carpal joint is a compound joint composed of:

1. The antebrachiocarpal joint between the radius/ulna and the proximal carpal bones.

2. The middle carpal joint between the two rows of carpal bones.

3. The carpometacarpal joint between the distal carpal bones and the proximal metacarpals.

The joint is a synovial joint, consisting of a common outer fibrous capsule and three inner synovial pouches, one for each joint. Collateral ligaments extend from the radius to the metacarpal bones on the medial and lateral aspect of the carpus. The carpal canal houses both the deep digital flexor tendon, and the deep branch of the superficial digital flexor.

Muscles of the Forelimb

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.

Trapezius:

Innervated by: 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.:

Innervated by: Accessory n.
The two parts are separated by the clavicle, where it exists.
Origin: occipital bone, nuchal ligament and the mastoid process.
Insertion: deltoid tuberosity and fascia of the limb.
Actions: advances the limb and extends the shoulder joint when limb is in motion. Draws the head and neck ventrally when the limb is fixed.

Omotransversarius:

Innervated by: Accessory n.
Origin: transverse processes of the atlas.
Insertion: acromion and spine of scapula.
Action: advancing the limb.

Latissimus dorsi:

Innervated by: 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. The cranial fibers strap the scapula to the chest. It retracts the free limb and flexes shoulder joint. It draws the trunk forward over the fixed limb.

Pectoral mm.:

Innervated by: brachial plexus
Two superficial parts, cranial and caudal, these aren't very distinct in the ox.
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 and assist in protraction and retraction.

Serratis ventralis:

Innervated by: branch of the 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:

Innervated by: brachial plexus
Origin: nuchal ligament.
Insertion: dorsal border and adjacent scapula.
Action: retracting the limb, may also raise the limb.

Intrinsic Musculature

Muscles of the Shoulder

These muscles are grouped:

1. Lateral

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: bursa between the tendon of the infraspinatus and lateral tubercle of the humerus can be the site of inflammation.

2. Medial

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.

Coracobrachialis:

Innervated by: Musculocutaneous n. of the brachial plexus.
Origin: medial supraglenoid tubercle.
Insertion: proximal shaft of the humerus.
Action: fixator.

3. Caudal (Flexors)

Deltoids:

Innervated by: Axillary n. of the brachial plexus.
Origin: Two heads of origin; the caudal border and spine of the scapula and the acromion.
Insertion: deltoid tuberosity on the humerus.
Action: Flexor of Shoulder.

Teres Major:

Innervated by: Axillary n. of the brachial plexus.
Origin: dorsal part of the caudal scapula.
Insertion: teres tuberosity midway down humerus.

Teres Minor:

Innervated by: Axillary n. of the brachial plexus.


There are no defined extensors of the shoulder. Those involved (brachiocephalic m., biceps brachii, supraspinatus, and ascending pectorals) have other, more primary roles.


Muscles of the Elbow

Extensors

Triceps brachii:

Innervated by: Radial n. from the brachial plexus
Has three heads, the medial branch is the most developed. The long head is at the caudal margin of the scapula; The lateral, medial, and accessory heads are at the shaft of the humerus.
Insertion: olecranon, proteced by tricipital bursa against the bone and subcutaneous bursa against the skin.

Tensor fasciae antebrachii:

Innervated by: Radial n. from the brachial plexus.
Overlies the triceps extending from the scapula to the olecranon.

Flexors

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. It runs through the intertubercular groove of the humerus.

Brachialis:

Innervated by: Musculocutaneous n. from the brachial plexus.
Origin: proximocaudal humerus.
Insertion: spirals to insert next to biceps.

Muscles of the Carpal and Digital Joints

Extensors

All have innervation from the radial n. from the brachial plexus. They have a craniolateral position on the forearm and almost all of them originate from the lateral epicondyle of the humerus.

Extensor carpi radialis

The most medial, inserts on 2nd/3rd metacarpal bone.

Ulnaris lateralis

The most lateral, inserts on accessory carpal bone.

Extensor carpi obliquus (aka- abductor pollicis longus)

Origin: cranial radius.
Insertion: most medial metacarpal bone .

Common Digital Extensor

Insertion: extensor process of the distal phalanx of each digit.

Lateral Digital Extensor

Insertion: dorsal proximal phalanges.

Medial Digital Extensor

Insertion: middle and distal phalanges.

Flexors

All innervated by the median or ulnar n. of the brachial plexus. Have a caudal position on the forearm and originate from the caudal medial epicondyle of the humerus.

Flexor carpi radialis

The most medial, inserts on upper 2nd/3rd metacarpal bone.

Flexor carpi ulnaris

The most lateral, inserts on the accessory carpal bone.

Superficial Digital Flexor

Insertion: palmar surface of middle phalanges.

Deep Digital Flexor

Passes through carpal canal before branching and continues to palmar distal phalanges.

Interosseus muscles

This is covered in more detail in the bovine lower limb section.

Vasculature of the Forelimb

Click here for information on:

Arteries of the Forelimb

Veins of the Forelimb

Lymphatics of the Forelimb


Webinars

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