📝 STANDARD DESCRIPTION:
Tendon — dense regular connective tissue cord that attaches muscle → bone. Inelastic, very strong.
Ligament — dense connective tissue band attaching bone → bone. Some elastic (e.g., nuchal ligament).
Aponeurosis — flat, sheet-like tendon (e.g., epaxial muscles, abdominal muscles).
Synovial Bursa — closed fluid-filled sac between two structures (tendon + bone, skin + bone). Reduces friction.
Examples: bicipital bursa, supraspinous bursa.
Synovial Sheath — sleeve-like double-walled tube wrapping a tendon where it crosses a joint. Contains synovial fluid.
Examples: digital flexor tendon sheath, carpal tendon sheaths.
📚 DETAILED DESCRIPTION:
ACCESSORY STRUCTURES OF MUSCLES
1. TENDON (Tendo): A cord or band of dense regular connective tissue (>90% Type I collagen). Transmits muscle force to bone. Almost inelastic (stretches <5% before rupture). White, glistening, avascular except at periphery (paratenon).
2. LIGAMENT (Ligamentum): Connective tissue band joining bone to bone. Most are collagenous (white, inelastic) — e.g., collateral ligaments. A few are elastic (yellow) — e.g., ligamentum nuchae in horse/ox, ligamentum flavum.
3. APONEUROSIS: A flat, sheet-like tendon. Found where a thin muscle attaches over a wide area:
• Bicipital aponeurosis at the elbow.
• Aponeurosis of external abdominal oblique → linea alba.
• Galea aponeurotica of the scalp (in humans).
• Plantar aponeurosis of the foot.
4. RAPHE: Linear interlacing of tendon fibres of opposing muscles (e.g., median raphe of mylohyoideus, linea alba — though linea alba is also classified as aponeurosis).
5. SYNOVIAL BURSA (Bursa synovialis): A small, closed sac with synovial fluid that lies between two structures that move on each other.
• Subtendinous bursa — between tendon and bone (e.g., bicipital bursa).
• Subligamentous bursa — between ligament and bone.
• Subfascial bursa — between fasciae.
• Subcutaneous bursa — between skin and bone (e.g., precarpal bursa).
• Bursitis — inflammation → painful swelling. Examples: capped elbow (precarpal/olecranon bursitis in cattle), capped hock (calcaneal bursitis), bicipital bursitis (horse).
6. SYNOVIAL TENDON SHEATH (Vagina synovialis tendinis): A two-layered tube of synovial membrane wrapping a tendon where it changes direction or rubs against bone, especially over joints.
• Inner (visceral) layer attaches to tendon.
• Outer (parietal) layer attaches to surrounding tissue.
• Between them: a thin film of synovial fluid.
• Tenosynovitis — inflammation of sheath; classic in equine fetlock and digital sheath ('windgall').
// COMPARATIVE ANALYSIS
| HORSE |
Massive nuchal ligament (yellow elastic) supports head from withers — saves muscle energy. Stay apparatus uses ligament-only structures for standing rest. |
| OX |
Tendons of digital flexors very strong; cattle commonly suffer 'corkscrew claw' due to chronic tendon strain. |
| DOG |
Common cranial cruciate ligament rupture in stifle — major orthopaedic problem. |
CLINICAL RELEVANCE
Capped Hock / Capped Elbow — bursitis from lying on hard surfaces. Tenosynovitis — inflamed tendon sheath; e.g., 'windgall' in horse fetlock; carpal tunnel syndrome. Bowed tendon in racehorses — superficial digital flexor tendon strain.
