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==Introduction==

==Introduction==

Tendons are composed of bundles of collagen, predominantly type I, surrounding parallel rows of fibroblasts known as '''tenocytes'''. Tenocytes synthesize the collagen fibres that they surround. Many collagen fibres make up a '''fascicle'''. Within the fascicle, collagen fibres are parallel with a ‘crimp’ waveform. This arrangement allows lateral cohesion between fibres, preventing slippage between fibres or fibrils. The ‘crimp’ straightens when the tendon is loaded and then recoils when the load is removed; this allows the elastic function of tendons.

Tendons are composed of bundles of collagen, predominantly type I, surrounding parallel rows of fibroblasts known as '''tenocytes'''. Tenocytes synthesize the collagen fibres that they surround. Many collagen fibres make up a '''fascicle'''. Within the fascicle, collagen fibres are parallel with a ‘crimp’ waveform. This arrangement allows lateral cohesion between fibres, preventing slippage between fibres or fibrils. The ‘crimp’ straightens when the tendon is loaded and then recoils when the load is removed; this allows the elastic function of tendons.

There are no muscles in the equine digit, instead there are the tendons of insertion of the two extensor muscles and the two flexor muscles of the digit.

There are no muscles in the [[Phalanges - Horse Anatomy|equine digit]], instead there are the tendons of insertion of the two extensor muscles and the two flexor muscles of the digit.

==Thoracic Limb==

==Thoracic Limb==

===Extensors===

===Extensors===

'''''Common Digital Extensor Tendon'''''  

'''''Common Digital Extensor Tendon'''''  

*'''Action''': Extends the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|carpus]] and [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpophalangeal]] joint

*'''Action''': Extends the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|carpus]] and [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpophalangeal]] joint

The lateral digital extensor muscle arises from the lateral [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humeral]] epicondyle and forms the lateral digital extensor tendon on the lateral aspect of the antebrachium; caudal to the common digital extensor tendon. The tendon is enclosed within a synovial sheath as it extends distally over the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpus]] to insert on the dorsolateral aspect of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]].

The lateral digital extensor muscle arises from the lateral [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humeral]] epicondyle and forms the lateral digital extensor tendon on the lateral aspect of the antebrachium; caudal to the common digital extensor tendon. The tendon is enclosed within a synovial sheath as it extends distally over the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpus]] to insert on the dorsolateral aspect of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]].

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The suspensory ligament (middle interosseous muscle) is an entirely tendinous structure. The SL originates on the proximal aspect of the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]] (cannon) and distal [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|carpal bones]].  It lies within the groove between the second and fourth [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|metacarpals]] (splint bones), deep to the SDFT and DDFT. Running distally, it bifurcates into two extensor branches which insert on the proximal sesamoid bones. Each branch extends laterally and medially, either side of the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpophalangeal]] (feltlock) joint, to join the common digital extensor tendon. The major function of the SL is as part of the '''suspensory apparatus'''. It provides support to the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpophalangeal]] (fetlock) joint by preventing hyperextension and also limits palmar flexion.

The suspensory ligament (middle interosseous muscle) is an entirely tendinous structure. The SL originates on the proximal aspect of the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]] (cannon) and distal [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|carpal bones]].  It lies within the groove between the second and fourth [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|metacarpals]] (splint bones), deep to the SDFT and DDFT. Running distally, it bifurcates into two extensor branches which insert on the proximal sesamoid bones. Each branch extends laterally and medially, either side of the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpophalangeal]] (feltlock) joint, to join the common digital extensor tendon. The major function of the SL is as part of the '''suspensory apparatus'''. It provides support to the [[Joints and Ligaments - Horse Anatomy#Thoracic Limb|metacarpophalangeal]] (fetlock) joint by preventing hyperextension and also limits palmar flexion.

[[Image:Equine thoracic limb tendons ML.jpg|200px|thumb|right|'''Tendons of the thoracic limb, mediolateral view''']]

[[Image:Equine thoracic limb tendons palmar.jpg|200px|thumb|left|'''Tendons of the thoracic limb, palmar view''']]

[[Image:Equine pelvic limb tendons plantar.jpg|200px|thumb|right|'''Tendons of the pelvic limb, plantar view''']]

 

[[Image:Equine tendons pelvic limb LM.jpg|200px|thumb|right|'''Tendons of the pelvic limb, lateromedial view''']]

 

[[Image:Equine pelvic limb tendons ML.jpg|200px|thumb|right|'''Tendons of the pelvic limb, mediolateral view''']]

 

 

 

 

 

 

 

 

 

 

 

===Extensors===

===Extensors===

'''''Long Digital Extensor Tendon'''''  

'''''Long Digital Extensor Tendon'''''  

Originating from the proximal aspect of the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metatarsal]] (cannon) and [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|distal tarsal bones ]], the SL of the pelvic limb is relatively thinner and longer than that of the thoracic limb.  It lies within the metatarsal groove deep to the DDFT. Continuing distally it bifurcates into two '''extensor branches''', as in the thoracic limb, which insert on the '''proximal sesamoid bones'''. Identical to in the thoracic limb, medial and lateral branches then join the long digital extensor tendon.

Originating from the proximal aspect of the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metatarsal]] (cannon) and [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|distal tarsal bones ]], the SL of the pelvic limb is relatively thinner and longer than that of the thoracic limb.  It lies within the metatarsal groove deep to the DDFT. Continuing distally it bifurcates into two '''extensor branches''', as in the thoracic limb, which insert on the '''proximal sesamoid bones'''. Identical to in the thoracic limb, medial and lateral branches then join the long digital extensor tendon.

*Pasquini, C, Spurgeon, T.L., An Anatomy of Domestic Animals: A Systemic and Regional Approach, 10th Edition (2003), Bowker

*Pasquini, C, Spurgeon, T.L., An Anatomy of Domestic Animals: A Systemic and Regional Approach, 10th Edition (2003), Bowker

[[Category:Horse Anatomy]]

 

[[Category:To Do - AP Review]]

 

[[Category:Musculoskeletal System- Horse Anatomy]]