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Limb Muscles - Horse Anatomy (view source)
Revision as of 14:55, 11 October 2012
, 14:55, 11 October 2012→Thoracic Limb
These muscles 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 to stabilize the scapula.
These muscles 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 to stabilize the scapula.
'''''Trapezius''''':
'''''Trapezius'''''
:'''Innervatation''': Accessory n.
:'''Innervatation''': Accessory n.
:'''Origin''': Mid-dorsal raphe and supraspinous ligament
:'''Origin''': Mid-dorsal raphe and supraspinous ligament
:'''Action''': Raises the scapula against the trunk and swings cranially to advance the limb
:'''Action''': Raises the scapula against the trunk and swings cranially to advance the limb
'''''Brachiocephalic m.''''':
'''''Brachiocephalic'''''
:'''Innervation''': Accessory n.
:'''Innervation''': Accessory n.
:Two parts separated by the clavicle, where it exists
:Two parts separated by the clavicle, where it exists
:'''Action''': Advances the limb and extends the shoulder joint when limb is in motion. Draws the head and neck ventrally when the limb is fixed
:'''Action''': Advances the limb and extends the shoulder joint when limb is in motion. Draws the head and neck ventrally when the limb is fixed
'''''Latissimus dorsi''''':
'''''Latissimus dorsi'''''
:'''Innervation''': local branch of brachial plexus
:'''Innervation''': local branch of brachial plexus
:The broadest muscle of the back
:The broadest muscle of the back
:'''Action''': Antagonist to the brachiocephalic m. It retracts the free limb and flexes shoulder joint. It also draws the trunk forward over the fixed limb.
:'''Action''': Antagonist to the brachiocephalic m. It retracts the free limb and flexes shoulder joint. It also draws the trunk forward over the fixed limb.
'''''Pectoral mm.''''':
'''''Pectoral'''''
:'''Innervation''': brachial plexus
:'''Innervation''': brachial plexus
:Two superficial parts, cranial and caudal
:Two superficial parts, cranial and caudal
:'''Action''': Adducts the forelimb, assist in protraction and retraction
:'''Action''': Adducts the forelimb, assist in protraction and retraction
'''''Serratis ventralis''''':
'''''Serratis ventralis'''''
:'''Innervation''': branch of brachial plexus
:'''Innervation''': branch of brachial plexus
:'''Origin''': C4 to 10th rib
:'''Origin''': C4 to 10th rib
:'''Action''': Supports 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.
:'''Action''': Supports 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''''':
'''''Rhomboids'''''
:'''Innervation''': brachial plexus, although in some species, dorsal spinal nerves can innervate
:'''Innervation''': brachial plexus, although in some species, dorsal spinal nerves can innervate
:'''Origin''': Median connective tissue from poll to withers, lying deep to the trapezius
:'''Origin''': Median connective tissue from poll to withers, lying deep to the trapezius
:'''Insertion''': Dorsal border and adjacent scapula
:'''Insertion''': Dorsal border and adjacent scapula
:'''Action''': Retracts the limb, may also raise limb
:'''Action''': Retracts the limb, may also raise limb
===Intrinsic Musculature===
====Muscles of the Shoulder====
These muscles are grouped:
====='''Lateral'''=====
'''''Supraspinatus ''''' and '''''Infraspinatus'''''
:'''Innervation''':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 the lateral tubercle of the humerus can be the site of inflammation (bursitis).
====='''Medial'''=====
'''''Supscapularis'''''
:'''Innervation''': Subscapular n. from the brachial plexus
:'''Origin''': Deep surface of the scapula
:'''Insertion''': Medial tubercle of the humerus
:'''Action''': braces medial shoulder joint and is a potential adductor
'''''Coracobrachialis'''''
:'''Innervation''': Musculocutaneous n. of the brachial plexus
:'''Origin''': Medial supraglenoid tubercle
:'''Insertion''': Proximal shaft of the humerus
:'''Action''': fixator
====='''Caudal (Flexors)'''=====
'''''Deltoids'''''
:'''Innervation''': Axillary n. of the brachial plexus
:'''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'''''
:'''Innervation''': Axillary n. of the brachial plexus
:'''Origin''': Dorsal part of the caudal scapula
:'''Insertion''': Teres tuberosity midway down the humerus
'''''Teres Minor'''''
:'''Innervation''': Axillary n. of the brachial plexus
NB// 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'''''
:'''Innervation''': Radial n. from the brachial plexus
:It has three heads:
:'''Origin''':
::''Long head'': caudal margin of the scapula
::''Lateral'' and ''medial heads'': shaft of the humerus
:'''Insertion''': Olecranon, proteced by the tricipital bursa against the bone, and subcutaneous bursa against the skin
'''''Tensor fasciae antebrachii'''''
:'''Innervation''': Radial n. from the brachial plexus
:Overlies the triceps extending from the scapula to the olecranon
'''''Anconeus'''''
:'''Innervation''': Radial n. from the brachial plexus
:'''Origin''': distal humerus
:'''Insertion''': lateral olecranon
====='''Flexors'''=====
'''''Biceps brachii'''''
:'''Innervation''': Musculocutaneous n. from the brachial plexus
:'''Origin''': Supraglenoid tubercle of the scapula
:'''Insertion''': Medial tuberosity of the proximal radius and adjacent ulna
:It runs through the intertubercular groove of the humerus.
'''''Brachialis'''''
:'''Innervation''': Musculocutaneous n. from the brachial plexus
:'''Origin''': Proximocaudal humerus
:'''Insertion''': Spirals to insert next to biceps
====Muscles of the Carpal and Digital Joints====
====='''Extensors'''=====
The craniolateral position on the forearm, almost all originate from the lateral epicondyle of the humerus. All innervated by the radial n. from the brachial plexus.
'''''Extensor carpi radialis'''''
:The most medial, inserts on the metacarpal tuberosity.
'''''Ulnaris lateralis'''''
:The most lateral, inserts on the accessory carpal bone.
'''''Extensor carpi obliquus''''' (aka '''''abductor pollicis longus''''')
:'''Origin''': Cranial radius
:'''Insertion''': Head of the metacarpal II
'''''Common Digital Extensor'''''
:'''Insertion''': Extensor process of the distal phalanx
'''''Lateral Digital Extensor'''''
:'''Insertion''': Dorsal proximal phalanx
====='''Flexors'''=====
Caudal position on the forearm, originate from the caaudal medial epicondyle of the humerus. All innervated by the median or ulnar n. of the brachial plexus.
'''''Flexor carpi radialis'''''
:The most medial, inserts on the proximal part of metacarpal II (medial splint)
'''''Flexor carpi ulnaris'''''
:The most lateral, inserts on the accessory carpal bone.
'''''Superficial Digital Flexor'''''
:Inserts on the proximal extremity of middle phalanx and the distal extremity of proximal phalanx.
'''''Deep Digital Flexor'''''
:Passes through the carpal canal before branching and continues to palmar distal phalanx.
'''''Interosseus muscle/Suspensory ligament'''''
:This is covered in more detail in the [[Equine Tendons - Anatomy & Physiology|Equine Tendons]] section.
==Pelvic Limb==
==Pelvic Limb==