A16 - Vaginae et bursae synoviales of the equine forelimb

Question 1

Give the accessory structures of muscles and define them

Answer 1

• Recessus: dilation of the joint capsule (not in this topic)
• ​Retinaculum: Thickened part of the fascia, which participates in fastening of the tendons without synovial layer (not in this topic)
• Bursa: Closed cavity that contains synovia
• Vagina synovialis: tendon sheath

Question 2

Bursa

Give the structure of the bursa

Answer 2

• Closed cavity that contains synovia
• Major role: padding
• soma bursa may communicate with the cavity of a nearby joint
• Layers:
  
  • Stratum synoviale
  • Stratum fibrosum
• Types:
  
  • ​Bursa synovialis submuscularis
  • ​Bursa synovialis subfacialis
  • ​Bursa synovialis subtendinea
  • ​Bursa synovialis subcutanea

Question 3

Vagina synovialis

Answer 3

• Vagian synovialis = tendon sheath
• Some tendon sheaths may communicate with the cavity of nearby joint
• Role:
  
  • Padding
  • Providing sliding surface
  • Nutrition
• Vagina synoviales communis (contains more tendons)
• General structure (numbers on picture):
  
  1. Stratum fibrosum
  2. Stratum synoviale parietalis (lamina externa)
  3. Cavitas synovialis
  4. Stratum synoviale visceralis (lamina interna)
  5. Mesotendineum (blood and nerve supply of the tendon runs through this)

Question 4

Forelimb (eq)

Answer 4

• Bursa subligamentosa supraspinalis
  
  • Lig. nuchae/lig. supraspinale → proc. spinosus of the first thoracic vertebra (Th 2-5)
  • Role: formation of the withers and carrying the saddle load
• ​Bursa subcutanea prescapularis
  
  • ​Skin → spina scapulae
• ​Bursa intertubercularis
  
  • In the sulcus intertubercularis, under the originating tendon of the m. biceps brachii (origin: tub. supraglenoidale)
  • Communicates with the shoulder joint (!)
  • In canine there is a tendon sheath instead (vagina synovialis intertubercularis), which does not communicate with the shoulder joint
• ​Bursa subcutanea olecrani
  
  • ​Skin → olecranon
• ​Bursa intratendinea olecreani
  
  • ​M. triceps brachii, caput mediale & caput longum → olecranon
• ​Bursa subtendinea m. tricipitalis brachii
  
  • ​Inserting tendon of m. triceps brachii → olecranon

On the extensor side of the carpal joint:

• All muscles are running through in their own tendon sheath, in the corresponding groove of the distal cranial part on the radius
  
  • e.g.: sulcus tendinis m. extensor carpi radialis

On the flexor side of the carpal joint:

• ​Canalis carpi
  
  • ​Bony base: proximal row of carpus
  • Retinaculum flexorium closes it to be a channel where the digital flexors run through
• Vagina synovialis communis mm. flexorum (proximal common tendon sheath)
  
  • ​In the canalis carpi
  • Fastened by retinaculum flexorium
  • Contains the tendon for both digital flexors:​
    
    • M. flexor digitorum superficialis
    • M. flexor digitorum profundus
  • Includes the:
    
    • A. dig. palmaris communis II (palmari, final portion of a. mediana)
    • N. palmaris medialis (n. digitalis palmaris communis II, ex n. medianus)
• ​Vagina tendineum digitorum manus (distal common tendon sheath)
  
  • Behind the fetlock joint, on the surface of the scutum proximale
  • Fastened by lig. anulare digiti
  • Contains the tendons for both digital flexors:
    
    • ​M. flexor digitorum superficialis
    • M. flexor digitorum profundus
  • Contains manica flexoria
    
    • ​The superficial digital flexor’s tendon surrounds the deep digital flexor’s tendon
• ​​Bursa subtendinea m. extensorius digitorum communis
  
  • ​M. extensor digitorum communis → fetlock joint
• ​Bursae subtendinea mm. interosseum manus
  
  • ​Under the tractus appostus (ex. m. interosseus medius) on both sides, at the vental lateral/medial margins of the fetlock joint before they merge with the m. extensor digitorum communis
• ​Bursa podotrochlearis manus
  
  • ​M. flexor digitorum profundus → distal sesamoid bone