Regional Anatomy of Paravertebral Nerves | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

 Pudental Nerve

• The pudental nerve is crucial because blocking it helps relax the penis in bulls, making it easier to examine without affecting movement.

Formation and Origin:

• Mainly formed by the central branch of the third sacral nerve.
• Receives some contribution from the second and fourth sacral nerves.
• Originates caudoventrally, medial to the sacro-sciatic ligament, and dorsal to the internal pudendal artery.

Location Identification:

• Located by rectal palpation along the sacro-sciatic ligament.
• Best judged by feeling the internal pudendal artery on the side of the pelvic cavity via rectum.
• The artery is positioned 1" below the nerve.

Procedure for Nerve Block:

• Insert the needle through the ischio-rectal fossa.
• Identify the lesser sciatic foramen by using the middle finger.
• Insert the needle into the cranio-dorsal quadrant of the foramen.

Highlight:

• Pudental nerve block facilitates penis examination in bulls by promoting relaxation.
• Rectal palpation is used to locate the nerve along the sacro-sciatic ligament.
• Precise identification is achieved by palpating the internal pudendal artery.
• The needle is inserted through the ischio-rectal fossa into the cranio-dorsal quadrant of the lesser sciatic foramen.
• The block is performed on both sides for effective results.

Fig: Head of ox showizg the course of the cornual nerve

Fig: Skuii of ox showing tho aite of injoction for blocking the cornual nerve

Fig: Head of ox showing anaesthesia of the cornual nerve

Seven and a Part of the Fifth Cranial Nerve

Median Nerve

Description of Median Nerve:

• It's a significant nerve in the brachial plexus, originating from spinal roots in the neck and upper chest.
• Found in the forearm, beneath the Pronator teres muscle on the back-inner side.
• It runs down between certain forearm muscles and divides into smaller nerves in the palm.

Functions and Branches:

• Provides branches to various muscles in the forearm, including pronator teris, flexor carpi radialis, and others.
• Also supplies nerves to muscles in the hand.

Medical Procedures Involving the Nerve:

• Median nerve block helps diagnose lameness in animals.
• Neurectomy, which involves removing part of the nerve, is done in incurable limb conditions to ease pain and prolong the use of draft animals.

Injection Site for Nerve Block:

• Injection is given just below a bony bump near the elbow, at the groove between the back of the radius bone and a muscle called flexor carpi radialis.

Ulnar Nerve 

• Arises along with the median nerve from the neck and upper chest area (brachial plexus).
• Travels down to the inner side of the forearm, passing below the bony bump on the inner elbow (medial epicondyle of humerus).

Course and Divisions:

• Runs between muscles (flexor carpi ulnaris and ulnaris lateralis) in the forearm.
• Divides into dorsal and palmar branches near the accessory carpal bone in the lower part of the limb.

Muscular Contributions:

• Provides branches to various muscles, including flexor carpi ulnaris, flexor digitorum superficialis and profundus, ulnaris lateralis, and the elbow joint.

Injection Site for Nerve Block:

• The injection point for ulnar nerve block is about 4 inches above the upper border of the accessory carpal bone.
• Located between two specific muscles in the forearm, a hand's breadth above the accessory carpal, under the forearm's fascia.

Desensitization as an Indicator:

• Successful nerve block is indicated by the numbness felt laterally above the carpus (wrist).

Diagnostic Value for Suspensory Ligament Issues:

• Blocking the ulnar nerve can be useful in diagnosing suspected lesions in the suspensory ligament of the limb.

Radial Nerve

• The thickest among the branches of the brachial plexus, a network of nerves in the neck and upper chest.
• Travels downward and backward across muscles like subscapularis and teres major, parallel to the brachial artery.

Path and Termination:

• Runs alongside the brachial artery, separated by another nerve called ulnar nerve.
• Disappears in front of the long head of the triceps muscle, then passes behind the humerus bone, ending in the musculospinal groove.

Course in the Musculospinal Groove:

• Lies on the brachialis muscle and later on the posterior border of this muscle.
• Reaches the front of the elbow joint, passing between the brachialis and extensor carpi radialis.

Branches of the Radial Nerve:

• First Set:
  • Muscular branches supply triceps and tensor fasciae antibrachii muscles.
• Second Set:
  • Muscular branches provide support to the lateral head of triceps, brachialis, and anconeus muscles.
  • Cutaneous branch penetrates the lateral head of triceps, supplying skin on the outer side of the forearm below the elbow.
• Third Set:
  • Branches go to muscles like extensor carpi radialis, medial, common, and lateral digital extensors, extensor carpi obliquas, and ulnaris lateralis.

Highlight: The radial nerve is a major player in the brachial plexus, controlling various muscles in the arm and forearm, as well as providing sensation to the skin.

Fig: Brachial Plexus and its branches median, ulnar and radial: nerve with the forelimb reflected outwards and forwards

Fig: Ulnar and Radial Nerve (Lateral View) 

Tibial Nerve

• It's a continuation of the ischiatic nerve, found in the leg.
• Travels diagonally between the two heads of the calf muscle (gastrocnemius).

Division and Path:

• Splits into two plantar nerves in the upper part of the leg, either just above or around the ankle.
• Runs along the inner side of the superficial digital flexor muscle, beneath the gastrocnemius cover.

Lower Course and Accompanying Structures:

• Further down, it lies between the deep flexor muscle and the inner edge of the Achilles tendon.
• Accompanied by the recurrent tibial vein and artery.

Muscular Supply:

• Provides nerves to muscles like gastrocnemius, popliteus, soleus, and flexors of the toes.
• Also has small branches supplying sensation to the skin along its path.

Injection Site:

• For medical procedures involving the tibial nerve, the injection site is on the inner side of the leg.
• Located approximately a hand's breadth above the heel and half an inch in front of the Achilles tendon.

Highlight: The tibial nerve plays a crucial role in controlling muscles and providing sensation to the leg and foot.

Fibular Nerve

• It's a significant nerve branching off from the ischiatic nerve in the leg.
• Travels downward along with the main trunk until it reaches the origin of the calf muscle (gastrocnemius).

Path and Division:

• At the gastrocnemius, it takes a lateral and upward turn under the cover of the biceps femoris muscle.
• Divides into superficial and deep fibular nerves at the point where the extensor digitorum lateralis muscle begins.

Superficial Fibular Nerve:

• Supplies branches to the extensor digitorum lateralis muscle.
• Descends between this muscle and the long extensor of the toes, piercing the deep fascia.
• Branches out under the skin on the top and side of the foot or around the joint above the hoof (fetlock joint).

Deep Fibular Nerve:

• Continues from the fibular nerve and passes between specific muscles.
• Gives branches to muscles like extensor digitorum longus, extensor digitorum lateralis, tibialis cranialis, and fibularis tertius.
• Divides on the top side of the hock (ankle joint) into medial and lateral branches.

Nerve Block Site:

• For medical procedures involving the fibular nerve, the injection site is specified:
  • Below and behind the lateral bump of the shinbone (tibia) and
  • On the side of the leg, about 6 inches above the ankle (hock), in a groove between certain muscles.

Highlight: The fibular nerve is essential for controlling muscles and providing sensation in the leg and foot. Procedures involving this nerve often target specific injection sites for effective treatment.

Digital Nerves

• There are two sets of digital nerves: those in the forelimb, arising from the brachial plexus, and those in the hindlimb, arising from the lumbosacral plexus.

Forelimb Digital Nerves:

• Originating from the median nerve, the internal branch divides into internal and external divisions.
• The internal division supplies the medial accessory digit and continues as the postero-internal digital nerve along the inner aspect of the medial digit.
• The external division combines with a branch of the external branch of the median nerve to form the posterior common digital nerve.

Hindlimb Digital Nerves:

• The superficial peroneal nerve, after crossing beneath the peroneus longus muscle, passes down between the lateral digital extensors.
• It then travels between the lateral and common digital extensors, reaching the hock, and descending over the anterior annular ligament of the tarsus.
• This nerve divides into internal, middle, and external branches, each running down different aspects of the digits.

Branches and Divisions:

• The middle branch joins a branch from the deep peroneal nerve to form the anterior common digital nerve, which divides further into internal and external proper digital nerves.
• Another branch of the deep peroneal nerve divides into external and internal branches upon reaching the front of the tarsus.

Injection Sites and Paths:

• The internal branch of the deep peroneal nerve descends subcutaneously on the anterior face of the metatarsus.
• The external branch travels down the anterior groove of the metatarsus, eventually joining with the superficial peroneal nerve to form the anterior common digital nerve.

Highlight: Digital nerves supply sensation to the digits (fingers/toes) of animals. They arise from different nerve branches in the limbs and follow specific paths to reach their destinations.

Fig: Digital and Tibial Nerves

Fig: Digital nerves in the hind limb