Comparative Muscles/Passive Stay Flashcards
What are the primary components of the passive stay apparatus in the thoracic limb of horses?
Prox sesamoids, sesamoidean ligaments, suspensory ligament
## Footnote
These structures allow horses to doze while standing with minimal muscular activity.
List the superficial pectoral muscles.
- Descending pectoral
- Transverse pectoral
These muscles are involved in the movement and stabilization of the thoracic limb.
What is the clinical importance of the muscles and structures of the passive stay apparatus?
They relate to the weight bearing and movement of the horse
Understanding these structures is crucial for diagnosing and managing equine lameness.
How do the structures of the passive stay apparatus prevent joint flexion or extension in resting horses?
By supporting weight through tendons and ligaments
This system allows horses to maintain posture without muscular contraction.
What is the role of the serratus ventralis muscle?
It attaches the forelimb to the trunk and assists with shock absorption
This muscle is crucial for the stability of the thoracic limb.
What modifications occur at the shoulder joint in horses?
Thickened bicipital tendon of origin of biceps brachii
This tendon helps resist shoulder flexion.
True or False: The triceps muscle in horses has four heads.
False
The triceps has three heads in ungulates and no accessory head in horses.
Fill in the blank: The __________ of the deep digital flexor passes through the carpal canal.
Deep belly
The deep digital flexor has multiple bellies, with specific roles in joint movement.
What is the function of the lacertus fibrosus?
Transmits force to keep the carpus in position
It connects the biceps brachii to the extensor carpi radialis.
List the components of the suspensory apparatus.
- Suspensory ligament
- Sesamoids
- Sesamoidean l
These components work together to support the fetlock joint.
What prevents flexion of the elbow joint in horses?
Collateral ligaments and passive resistance from tendons
Flexion requires active contraction of the biceps.
What is the average length of sleep for horses?
3 hours
This includes a shorter REM sleep compared to humans.
What anatomical feature helps prevent collapse of the thoracic limb joints?
The passive stay apparatus
This system allows horses to stand and doze without collapsing.
True or False: The distal check ligament is an accessory ligament of the superficial digital flexor.
False
The distal check ligament is an accessory ligament of the deep digital flexor.
What does the term ‘flying scapula’ refer to?
Rupture of the dorsoscapular ligament / serratus ventralis mm
This condition affects the stability and movement of the scapula.
Fill in the blank: The __________ joint is supported by proximal and distal check ligaments.
Carpal
These ligaments are crucial for maintaining joint stability.
What is the average REM sleep duration for horses?
½ hour
This is significantly shorter than that of humans.
List the joints in the thoracic limb.
- Shoulder
- Elbow
- Carpus
- Fetlock
- Pastern
- Coffin
These joints are critical for limb movement and stability.
Which muscle wraps around the shoulder that gives it its roundness in horses; it is a part of the deep pectoral?
Subclavius
Where does the dorsocapular ligament fuse to?
surface of thoracolumbar fascia and to the scapula
How many heads of the deltoideus are there in the horse?
1, the scapular part
How many tricep heads in ungulates?
3, no accessory in equine
What connects the biceps brachial and extensor carpi radialis mm?
Lacertus fibrosis
What is the only flexor of the carpus that is innervated by the radial n?
Ulnaris lateralis
How many bellies in ruminants for the common digital extensor m?
2: medial and lateral
Which belly of the common digital extensor inserts on the 3rd digit and is larger?
Medial belly
Which belly of the common digital extensor splits and inserts on both digits?
Lateral belly
How many bellies are there for the SDF in equine?
One
Does the superficial belly of the SDF run outside or inside the flexor retinaculum?
Outside
How many bellies does the DDF have?
3: humeral, smaller radial and ulnar
Describe the relationship between SDFT and the DDFT in the distal limb
The SDFT will split distally to allow the DDFT to pass onto P3
Which check ligament is associated with the SDF muscle?
Proximal
Which ligament is associated with flexural deformities in young foals and calves?
The contraction of DDFT and distal check ligament
What generates tension in the thoracic limb?
Weight on the shoulder
(Flexion/extension) ______________ is prevented by _______________ in the shoulder joint.
Flexion; biceps brachii internal tendon
Which tendon travels with the external carpi radialis?
Internal tendon of biceps brachii
Describe the effect of lacertus fibrosus and its relationships
Weight applied at shoulder; tension is transmitted through internal tendon of biceps brachii to lacertus fibrosis, through its connection to the extensor carpi radialis keeps the carpus in position
When the shoulder is fixed, the weight rests on the ?
Radius
In which joint is Flexion prevented by the carpal and digital flexors resting and the collateral l location?
Cubital/elbow
What naturally resists Flexion at the cubital joint?
Collateral ligaments being caudal to the point of rotation
What needs to happen for Flexion to occur?
Active contraction by the biceps to stretch the collateral ligaments
At the carpus, __________ is prevented by ___________ , ____________, and _____________.
Hyperextension; SDFT/DDF mm with their check ligaments; carpal bone shape, palmar carpal ligament
List the carpal modifications
- Proximal and distal check ligaments
- palmar carpal ligament
- flexor tendons
- flexor retinaculum
True or false: the distal limb has muscles
False
At the _____________ joint, hyperextension is prevented by SDFT/DDFT and check ligaments and the suspensory apparatus
Fetlock joint
The suspensory ligament is a modification association with which joint?
Fetlock
Which ligament attaches to the common digital extensor tendon to passively resist the pull of the flexors?
Extensor branch of the suspensory ligament
Describe the function of the suspensory apparatus
Form a sling to prevent hyperextension of the fetlock
In the pastern joint, what prevents hyper extension?
- Suspensory apparatus
- straight sesamoidean ligament
- DDFT
Which structure prevents hyperextension of the coffin joint?
DDFT
