Canine Forelimb Flashcards
(70 cards)
What are the basic functions of the canine forelimb?
- Bodyweight support for cranially positioned structures – anything in the thoracic region, head and neck.
- Involved in locomotion, particularly in directional control
- Object manipulation
Briefly state the innervation and supply to the canine forelimb.
- Innervation via structures of the brachial plexus
- Arterial supply via the axillary artery
- Venous drainage mainly via the external jugular vein
Describe the neurological input to the brachial plexus.
- Spinal nerves C6-T2
- Nerve roots converge and then diverge to innervate specific areas of the limb
- Complex neurological structure found in the axillary region
What are brachial plexus avulsion injuries?
When the forelimb has been pulled further away from the body than it normally would be, which damages and stretched out the structures of the brachial plexus and neurological inputs are prevented from coming through these nerves.
Name 6 important nerves of the brachial plexus.
Subscapular
Suprascapular
Musculocutaneous Axillary
Median
Ulnar
Radial
What is the location of the radial nerve?
Extends the elbow, carpus and digits. Runs caudomedially to humerus and then wraps cranially over brachialis to extensor muscles of cranial antebrachium.
Can be identified running medial to lateral between accessory head of triceps and brachialis.
What is the function of the radial nerve?
Important for weightbearing anti-gravity muscles.
What does the median nerve supply?
Provides sensory innervation to the palmaromedial paw
What does the ulnar nerve supply?
Provides sensory innervation to the caudal antebrachium, palmar paw and the lateral side of the 5th digit
What is similar between the radial and ulnar nerves?
Both median and ulnar nerves have the same motor innervation and provide all carpal and digital flexion supply to carpal and digital flexion muscles.
Define autonomous sensory zones.
The areas in the limb where only 1 nerve is supplying that region, there is no overlap of other nerves. Which means, if an animal is unable to feel in that region, there is a problem with the sensory nerve from that particular nerve.
State the autonomous sensory zones of the radial, ulnar and median nerves.
Radial – craniolateral antebrachium and dorsal paw
Ulnar – caudal antebrachium, palmarolateral paw and lateral 5th digit
Median – palmaromedial paw
Describe the blood supply to the canine forelimb.
- Axillary artery comes in through the axilla
- Branches to give off thoracodorsal artery
- Then becomes the brachial artery in the upper part of the limb
- Branches into ulnar and median arteries
- Also branches into an interosseous branch, which runs between the 2 distal limb bones of the limb
- Median artery branches to the palmar arteries just distal to the accessory carpal
Where can a palpable pulse be felt in the distal forelimb? Why is this important?
Median artery branches to the palmar arteries just distal to the accessory carpal and is a region where you can find a palpable pulse in the distal limb of the dog.
Peripheral pulses are important for checking peripheral circulation and patient monitoring.
Describe the venous drainage of the forelimb.
- Some blood returned to the body via the axillary vein but the majority of blood return is via the cephalic vein
- Cephalic vein runs up the dorsal side of the limb and is joined by venous return from the medial veins more palmarly via the median cubital vein, which crosses across the elbow joint
- Cephalic vein into the external jugular vein
Cephalic and accessory cephalic veins are important clinically for venepuncture in dogs and cats.
What is synsarcosis?
Forelimb is attached to the body by synsarcosis, a muscular sling supporting the torso between the forelimbs. If laid down and forelimbs where extended and straight, muscles such as the serratus ventralis would allow the ribcage to be sort of sling.
Why is synsarcosis useful?
Synsarcosis is useful in locomotion, as it allows craniocaudal translation across the thorax. Along with spinal extension and flexion, increases stride length in locomotion.
Distinguish extrinsic and intrinsic muscles.
Extrinsic muscles attach the limb to the body
Muscles with origin and insertion within the limb are intrinsic
Name the extrinsic musculature of the forelimb.
Trapezius
Omotransversarius
Brachiocephalicus
Latissimus dorsi
Pectorals
Describe the structure and function of trapezius.
Large triangular shaped muscles, 2 bellies, one cranially and one caudally. These attach from the scapula spine to cervical midline cranially and thoracic dorsal midline caudally.
Describe the position of omotransversarius.
Runs from distal scapula spine to transverse processes of C1-C2.
Describe the structure of brachiocephalicus.
Runs between the arm and head. Split into 2 portions at the clavicular intersection, the area where a clavicle would be if the animal had it and where you may find a vestigial clavicle, particularly on feline radiographs. 2 parts:
- Cleidobrachialis – goes to the arm
- Cleidocephalicus – going from the clavicular intersection to the head
Describe the structure and position of latissimus dorsi.
Large fan shaped muscle from teres major tuberosity on caudal humerus to the thoracolumbar fascia and last 2-3 ribs.
Describe the position of the pectorals.
Across the thorax more ventrally.
- Superficial pectoral – runs from 1st 2-3 sternebrae to the great tubercle of the humerus
- Deep pectoral – runs from lesser tubercle and brachial fascia
