Ga question

Questions

1. Deep antebrachial artery supplies what muscle?

2. Where are the proximal sesamoid bones located?

3. Which nerve is cranial to the medial epicondyle and what muscles does it innervate? (Bonus: What does the ulnar nerve innervate?)

4. What muscle turns the dorsal aspect of the paw lateral?

5. What nerve innervates the superficial pectoral muscle?

6. What parts of the spinal nerves make up the brachial plexus?

7. What muscles does the suprascapular nerve innervate?

8. What are the branches of subscapular artery?

9. What is the connection between superficial and deep venous supply?

10. Caudal pectoral nerve innervates which muscle?

11. What artery supplies the biceps brachii?

12. Shoulder is unable to flex. Which nerve is damaged?

13. Elbow is unable to flex. Which nerve is damaged?

14. Which brachial artery is located in the antebrachium?

15. What muscle is most likely damaged when accessory carpal bone is damaged with hyperextension?

16. What nerve runs with deep brachial artery?

17. Where does the suspensory ligament insert?

18. Horse sesamoids located where?

Answer Key

1. Flexors of antebrachium and manus

2. Metacarpophalangeal joint

3. Median nerve, DDF (+ SDF, pronator quadratus and pronator teres) (Bonus: Flexor carpi ulnaris + DDF)

4. Supinator muscle

5. Cranial pectoral nerve

6. $C_6$ to $T_2$

7. Supraspinatus muscle + infraspinatus muscle

8. Thoracodorsal artery and caudal circumflex humeral artery

9. Median cubital vein

10. Deep pectoral muscle

11. Cranial circumflex humeral artery

12. Axillary nerve

13. Musculocutaneous nerve

14. Common interosseous artery

15. Flexor carpi ulnaris

16. Radial nerve runs with deep brachial artery

17. Proximal sesamoid bones

18. Metacarpophalangeal joint

Step-by-Step VANS (Veins, Arteries, and Nerves) Breakdown

1. Arteries (Blood Flowing Down the Leg)

Think of the arterial system as one major highway running down the forelimb. As it traverses different regions, the main trunk changes names, and specific arterial branches split off:

1. Subclavian Artery: Originates near the chest/base of the neck.

2. Axillary Artery: Main continuation as blood enters the armpit (axillary region).

   • External Thoracic Artery: Supplies the superficial pectoral muscle.

   • Lateral Thoracic Artery: Supplies the deep pectoral muscle and axillary lymph node.

   • Subscapular Artery: Large branch that divides into:

     • Thoracodorsal Artery: Supplies the latissimus dorsi muscle.

     • Caudal Circumflex Humeral Artery: Encircles the proximal humerus.

   • Cranial Circumflex Humeral Artery: Arises near the distal axillary / proximal brachial region to supply the biceps brachii muscle.

3. Brachial Artery: The main highway running down the arm (brachium).

   • Deep Brachial Artery: Travels alongside the radial nerve.

   • Bicipital Artery: Directly supplies the biceps brachii.

   • Collateral Ulnar Artery: Runs caudally toward the elbow joint.

   • Transverse Cubital Artery: Passes cranial to the elbow joint.

   • Common Interosseous Artery: Located in the forearm (antebrachium), passing between the radius and ulna.

4. Median Artery: The main continuation down the forearm (antebrachium).

   • Deep Antebrachial Artery: Main supply to the deep flexor muscles of the antebrachium and manus.

   • Radial Artery: Runs distally to supply the medial aspect of the forepaw.

2. Veins (Blood Flowing Back UP to the Heart)

Veins are organized into superficial and deep systems that return blood back UP from the paw toward the heart:

1. Superficial Venous System:

   • Dorsal Common Digital Vein IV: Begins down in the paw/foot.

   • Accessory Cephalic Vein: Drains the dorsal paw and merges into the main cephalic vein.

   • Cephalic Vein: The primary superficial vein on the cranial/lateral surface of the limb. Key site for clinical venipuncture and intravenous catheter placement.

2. Deep Venous System:

   • Brachial Vein: Deep vein running alongside the brachial artery, receiving blood from deep structures and muscles of the forearm and arm.

3. Venous Connections & Return:

   • Median Cubital Vein: Acts as a crucial bridge vein at the elbow region, connecting the deep venous system (Brachial Vein) directly to the superficial system (Cephalic Vein).

   • Destination: The Cephalic vein empties into the External Jugular Vein, which drains into the Cranial Vena Cava and directly into the heart. Deep veins continue into the Axillary and Subclavian veins.

3. Nerves (The Electric Wires from the Spine)

All forelimb nerves originate from the Brachial Plexus (formed by spinal nerves $C_6$ to $T_2$):

• Cranial Pectoral Nerve: Innervates the superficial pectoral muscle (runs with the external thoracic artery).

• Caudal Pectoral Nerve: Innervates the deep pectoral muscle (runs with the lateral thoracic artery).

• Lateral Thoracic Nerve: Innervates the cutaneous trunci muscle (responsible for the skin-twitch reflex / panniculus reflex).

• Suprascapular Nerve: Passes through the scapular notch to innervate the supraspinatus and infraspinatus muscles.

• Subscapular Nerve: Innervates the subscapularis muscle.

• Axillary Nerve: Innervates flexors of the shoulder (deltoideus, teres major, teres minor) and provides sensory coverage to the craniolateral brachium.

• Thoracodorsal Nerve: Innervates the latissimus dorsi muscle (runs with the thoracodorsal artery).

• Musculocutaneous Nerve: Innervates elbow flexors (BBC: biceps brachii, brachialis, coracobrachialis) and provides sensory feeling to the antebrachium.

• Radial Nerve: Runs parallel to the deep brachial artery to power elbow, carpus, and digit extenders (such as triceps brachii, tensor fasciae antebrachii, and anconeus).

• Median & Ulnar Nerves: Originate from a common trunk and travel together down the limb:

  • Median Nerve: Passes cranial to the medial epicondyle to innervate carpal/digital flexors (pronator teres, pronator quadratus, flexor carpi radialis, SDF, and DDF).

  • Ulnar Nerve: Passes caudal to the medial epicondyle to innervate flexor carpi ulnaris and DDF, plus sensory to digit V and lateral/palmar paw.