Passive stay apparatus PDF

Preview

Summary

Lecture notes on the passive stay apparatus...

Description

1

Lecture 1

6.12.16

Passive stay apparatus • Large animals have evolved adaptations to anatomy to reduce muscular effort required for standing still These adaptations typically involve increasing content of collagenous connective tissue within • musculoskeletal structures supporting joints • These are positioned to resist the flexion/extension of joints which are put under tension through the body weight of the animal The forelimb 1. Weight of the trunk is applied primarily to the proximomedial scapula (serratis ventralis 2. When transferred down the leg: A. Shoulder flexes B. Elbow flexes slightly = The weight sits on top of the elbow joint so minimal tension required in triceps C. Carpus = Sits in line so could flex or hyperextend D. Fetlock and pastern joint will hyperextend • Attachment to the trunk = serratus ventralis • Shoulder = Biceps brachii • Elbow and carpus = Triceps, lacerates fibrosus and palmar fibrocartilage • Distal limb = Check, interosseous and sesmoidean ligaments • Serratis ventralis: - Interspersed with stout connective tissue - Supports most of the weight of the trunk • Biceps brachii: - Moulds over bicipital grooves either side of the intermediate tubercle - Major role in fixing the shoulder and to prevent flexion while standing - The internal tendon runs the length of the muscle and detaches a branch called the lacertus fibrosus which blends with the epimysium of the extensor carpi radialis • Elbow and carpus: - Triceps = keep the elbow extended and requires minor muscular effort as the centre of gravity is over the joint - Lacerates fibrosus = Fibrous branch to the extensor carpi radialis which forms a rigorous connection between the biceps insertion and ECR insertion • Palmar carpal fibrocartilage: - Resists carpal hyperextension • Check ligaments: - SDF and DDF both have check ligaments in forelimb - They provide a tendinous bride over the palmar surfaces of the joint to prevent hyperextension in the distal joints Palmar support prevents hyperextension • Interosseous: - Also known as the suspensory ligament - Solely tendinous - Extensor branch to common digital extensor - Distal sesmoidean ligaments which attach to each sesamoid bone Suspensory ligament

2

Lecture 1

The hindlimb • The hip, stifle and hock all tend to flex with weight bearing • The stay apparatus help prevent this in the hind leg • It comprises the patella locking mechanism and reciprocal apparatus proximally and the plantar support structures distally • The stifle: - Centre of gravity comes from the hip joint - Stifle movement limited by patella locking mechanism if engaged • The hock: - The stifle and hock movement are linked - Hindlimb SDF is almost entirely tendinous - SDF is the most important to resist hock flexion Deep digital flexor • Tendons pass medially to calcaneous • Small accessory (check) ligament on DDFT • Provides plantar support in the hindlimb Flexor tendons • DDF and SDF tendons provide resistance to hyperextension • Minimal, if any check ligaments from the flexor tendons in the hindleg • SDF attached to the calcaneous • Small check ligament on the DDF to the proximal metacarpal 3 Tarsal plantar support structure • Long plantar ligament = resist hyperextension • Crosses all distal tarsal joints

6.12.16...