ECC Equine Anatomy & Physiology 3 — Questions and Answers
Question 1: What term describes the joint between the sacrum and the ilium in the horse, and what type of joint is it?
- Lumbosacral joint; cartilaginous symphysis
- Sacroiliac joint; synovial and syndesmotic composite (Correct answer)
- Coxofemoral joint; synovial ball-and-socket
- Sacrococcygeal joint; fibrocartilaginous
Correct answer: Sacroiliac joint; synovial and syndesmotic composite
The sacroiliac joint is a composite joint with a small synovial component cranioventrally and a large syndesmotic (fibrous) component, allowing minimal but critical motion.
Question 2: The digital flexor tendon sheath in the equine digit extends from approximately which anatomical landmarks?
- Mid-cannon to the distal pastern (Correct answer)
- Proximal pastern to the navicular bursa
- Fetlock to the middle of the middle phalanx
- Coronary band to the coffin bone
Correct answer: Mid-cannon to the distal pastern
The digital flexor tendon sheath extends from approximately the mid-metacarpal/metatarsal region to the distal pastern, encasing the flexor tendons through the fetlock.
Question 3: Which nerve plexus supplies the forelimb of the horse, and which nerve is most commonly injured in 'sweeney' (shoulder atrophy)?
- Lumbar plexus; femoral nerve
- Brachial plexus; suprascapular nerve (Correct answer)
- Cervical plexus; radial nerve
- Brachial plexus; musculocutaneous nerve
Correct answer: Brachial plexus; suprascapular nerve
The brachial plexus supplies the forelimb, and the suprascapular nerve is typically damaged in 'sweeney,' causing atrophy of the supraspinatus and infraspinatus muscles.
Question 4: In the equine vertebral column, what is the function of the articular facets (zygapophyseal joints) at the thoracolumbar junction?
- Allow unrestricted rotation in all planes
- Guide and limit spinal motion while transmitting compressive loads (Correct answer)
- Serve as primary attachment sites for the nuchal ligament
- Permit ventral flexion only
Correct answer: Guide and limit spinal motion while transmitting compressive loads
Zygapophyseal (facet) joints guide the direction of permitted movement and limit excessive motion while sharing compressive and shear loads with the intervertebral disc.
Question 5: The 'stay apparatus' of the equine hindlimb relies on which structure locking the stifle to maintain limb extension with minimal muscle effort?
- Patellar tendon locking over the medial trochlear ridge of the femur (Correct answer)
- Long digital extensor tendon looping around the hock
- Suspensory ligament hooking onto the fibula
- Peroneus tertius fixing the hock in extension
Correct answer: Patellar tendon locking over the medial trochlear ridge of the femur
The medial patellar ligament hooks over the medial trochlear ridge of the femur, locking the stifle in extension and engaging the hindlimb stay apparatus.
Question 6: Which joint in the equine tarsus (hock) provides the majority of flexion and extension motion?
- Proximal intertarsal joint
- Distal intertarsal joint
- Tarsocrural (tibiotarsal) joint (Correct answer)
- Tarsometatarsal joint
Correct answer: Tarsocrural (tibiotarsal) joint
The tarsocrural joint accounts for approximately 90% of hock flexion and extension, while the distal tarsal joints are largely immobile.
Question 7: What is the normal formula for the equine dental arcade, and how many teeth does an adult male horse typically have?
- I 3/3, C 1/1, P 3/3, M 3/3 = 40 teeth (Correct answer)
- I 3/3, C 1/1, P 4/4, M 3/3 = 44 teeth
- I 3/3, C 0/0, P 3/3, M 3/3 = 36 teeth
- I 3/3, C 1/1, P 3/3, M 3/3 = 42 teeth
Correct answer: I 3/3, C 1/1, P 3/3, M 3/3 = 40 teeth
Adult male horses typically have 40 teeth: 12 incisors, 4 canines, 12 premolars, and 12 molars; mares often lack canines, giving 36 teeth.
ECC Equine Anatomy & Physiology 3
What term describes the joint between the sacrum and the ilium in the horse, and what type of joint is it?