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Thoracic Limb Extrinsic Muscles - Horse Anatomy (view source)
Revision as of 16:36, 3 January 2023
, 16:36, 3 January 2023no edit summary
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==Introduction==
==Introduction==
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 [[Bones and Cartilages - Horse Anatomy|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 [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula]].
====Superficial Musculature====
====Superficial Musculature====
:'''Innervatation''': Accessory n.
:'''Innervatation''': 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 [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula]]
:'''Body''': Two parts, cervical and thoracic, separated by aponeurosis
:'''Body''': Two parts, cervical and thoracic, separated by aponeurosis
:'''Action''': Raises the scapula against the trunk and swings cranially to advance the limb
:'''Action''': Raises the [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula]] against the trunk and swings cranially to advance the limb
'''''Brachiocephalic'''''
'''''Brachiocephalic'''''
:Two parts ('''cleidobrachial''' and '''cleidocephalic''' muscle) separated by the clavicle, where it exists
:Two parts ('''cleidobrachial''' and '''cleidocephalic''' muscle) separated by the clavicle, where it exists
:'''Origin''': Mastoid process of temporal bone, nuchal crest, wing of atlas and the transverse processes of the 2nd-4th cervical vertebrae
:'''Origin''': Mastoid process of temporal bone, nuchal crest, wing of atlas and the transverse processes of the 2nd-4th cervical vertebrae
:'''Insertion''': Deltoid tuberosity and crest of the humerus
:'''Insertion''': Deltoid tuberosity and crest of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]]
:'''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 [[Joints and Ligaments - Horse Anatomy#Shoulder Joint|shoulder]] joint when limb is in motion. Draws the head and neck ventrally when the limb is fixed
'''''Cleidomastoid'''''
'''''Cleidomastoid'''''
:'''Innervatation''': Accessory n. and Axillary n.
:'''Innervatation''': Accessory n. and Axillary n.
:'''Origin''': Mastoid process of the temporal bone and nuchal crest
:'''Origin''': Mastoid process of the temporal bone and nuchal crest
:'''Insertion''': Deltoid tuberosity, crest of the humerus and fascia of the shoulder as the '''cleidobrachialis''' muscle
:'''Insertion''': Deltoid tuberosity, crest of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]] and fascia of the [[Joints and Ligaments - Horse Anatomy#Shoulder Joint|shoulder]] as the '''cleidobrachialis''' muscle
:'''Action''': If acting bilaterally, it draws the head and neck down and backwards. If the acting with one shoulder fixed, it draws the head, upper arm fascia and neck to one side.
:'''Action''': If acting bilaterally, it draws the head and neck down and backwards. If the acting with one [[Joints and Ligaments - Horse Anatomy#Shoulder Joint|shoulder]] fixed, it draws the head, upper arm fascia and neck to one side.
'''''Latissimus dorsi'''''
'''''Latissimus dorsi'''''
:The broadest muscle of the back
:The broadest muscle of the back
:'''Origin''': Thoracolumbar fascia
:'''Origin''': Thoracolumbar fascia
:'''Insertion''': Teres tuberosity of the humerus
:'''Insertion''': Teres tuberosity of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]]
:'''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 [[Joints and Ligaments - Horse Anatomy#Shoulder Joint|shoulder]] joint. It also draws the trunk forward over the fixed limb.
'''''Superficial Pectorals'''''
'''''Superficial Pectorals'''''
::Caudal ('''transverse''') - First six costal cartilages and ventral sternum
::Caudal ('''transverse''') - First six costal cartilages and ventral sternum
:'''Insertion''':
:'''Insertion''':
::Cranial ('''descending''') - The crest of the humerus, distal to the deltoid tuberosity
::Cranial ('''descending''') - The crest of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]], distal to the deltoid tuberosity
::Caudal ('''transverse''') - Covers the elbow joint to insert on the medial fascia of the forearm
::Caudal ('''transverse''') - Covers the elbow joint to insert on the medial fascia of the forearm
:'''Action''': Adducts the forelimb, assist in protraction and retraction
:'''Action''': Adducts the forelimb, assist in protraction and retraction
:The cranial ('''descending''') pectoral muscle forms a visible prominence cranial to the sternum; extending between the manubrium and the humeral crest.
:The cranial ('''descending''') pectoral muscle forms a visible prominence cranial to the sternum; extending between the manubrium and the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humeral crest]].
====Deep Musculature====
====Deep Musculature====
:'''Innervation''': Cranial and caudal thoracic n.
:'''Innervation''': Cranial and caudal thoracic n.
:'''Origin''': Xiphoid and 4th costal cartilages of the sternum
:'''Origin''': Xiphoid and 4th costal cartilages of the sternum
:'''Insertion''': Two branches on the lesser and greater tubercles of the humerus, supraglenoid tubercle of scapula
:'''Insertion''': Two branches on the lesser and greater tubercles of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]], supraglenoid tubercle of [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula]]
:'''Action''':Draws the limb back, supports the trunk, moves the trunk cranially over an advanced limb and extends the shoulder.
:'''Action''':Draws the limb back, supports the trunk, moves the trunk cranially over an advanced limb and extends the [[Joints and Ligaments - Horse Anatomy#Shoulder Joint|shoulder]].
:'''Innervation''': Dorsal and ventral Cervical n., long thoracic n.
:'''Innervation''': Dorsal and ventral Cervical n., long thoracic n.
:'''Origin''': 1st-7th rib, transverse process of cervical vertebrae
:'''Origin''': 1st-7th rib, transverse process of cervical vertebrae
:'''Insertion''': Medial scapula and scapular cartilage
:'''Insertion''': Medial [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula and scapular cartilage]]
:'''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.
::Thoracic - Spinous processes of 2nd-6th cervical and 7th thoracic vertebrae
::Thoracic - Spinous processes of 2nd-6th cervical and 7th thoracic vertebrae
:'''Insertion''':
:'''Insertion''':
::Cervical - Unites with trapezius to insert on scapular cartilage
::Cervical - Unites with trapezius to insert on [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapular cartilage]]
::Thoracic - Scapula
::Thoracic - [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula]]
:'''Action''': Draws the limb forward and elevates the limb and neck. Fixes the scapula against the trunk.
:'''Action''': Draws the limb forward and elevates the limb and neck. Fixes the [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula]] against the trunk.
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[[Category:Muscles - Horse Anatomy]]