Lecture 6 -- Forelimb Anatomy and Nerve Supply Flashcards

Describes the labelling features.

A: Carpal pad

• Protect accessory carpal bone

B: Dew clew

C: Metacarpal pad

• Overlies metacarpo-phalangeal joint

D:Digital pad

• Overlies distal interphalangeal joint

E: Claw

What is the function of the carpal pad specifically?

Protects the accessory carpal bone

What are the functions of footpads?

1. Resistance to trauma/wear and tear

2. Traction = Prevent slipping

3. Anti-concussive 防震

4. Protection of deep structures

5. Support of the digit → Allow weight bearing over DP, MP, PP and MCP joints

What are the modifications to the epidermis of the footpad for trauma resistance?

1. Increased skin thickness

2. Increased turnover of cells (Active germinative layer = Stratum basale)

3. Deposition of keratin (Keratinised stratified squamous epithelium)

4. Rough surface

5. Sweat glands

6. Variable amounts of pigmentation

7. Hairless, thick skin.

What are the components of a footpad?

• Skin

  1. Epidermis

     1. Stratum corneum

     2. Stratum lucidum

     3. Stratum granulosum

     4. Stratum spinosum

     5. Stratum basale = Germinative layer

  2. Dermis

• Superficial fascia

• Digital cushion

What is the function of the digital cushion in the footpad?

Vacular supply and Shock absorption

What clinical consideration of footpad?

1. Damage of DDFT → Stubbed toes (Hyperextension of digits)

2. Careful with bandaging → Sweat gland around footpad

3. Wounds (Contain excessive vascular channels)

Describe the normal position of a claw.

How is the normal claw position maintained?

Tip touches ground.

Extensor tendons, dorsal elastic ligament, balanced by DDFT, continuous growth where the tip wears naturally.

What are the two germinative area in claws?

1. Horn (Epidermis that is heavily keratinised) grows over dorsal and lateral surfaces of ungual process

2. Horn overs palmar surface

What happens to the dermis of the claw?

It fuses directly to periosteum of unfurl process of digital phalanx

As the claw continues to grow, the tip wears naturally. What factors may reduce the wearing?

1. Not walking

2. Walking on soft ground

3. Dew claw

4. DDFT damage = Subbed toe

Which part of the claw can be cut, and which cannot?

Horn = Epidermis = Insensitive = Can cut

BUT dermis → Contain blood and nerve supply = Cannot cut

What are the similarities and difference between the claws of cats and dogs?

Similarities:

1. Same number of pads and claws

2. Same components and function

Difference:

1. Cat claws are retractable by adding more pressure on DDFT, while dog claws are not

2. Cat claws tend to be sharper.

What is the function of lymph nodes?

Filters lymph

Prevents contaminants from reaching systemic circulation

Contains defense cells → Removes invading organisms

What are the forelimb lymph nodes?

Prescapular (Located at the cranial aspect of scapular - In front of the should joint)

Axillary lymph nodes (Located under the axilla)

Which selected extrinsic muscles does the brachial plexus supply?

Pectoral muscles, latissimus dorsi, and serratus ventralis.

Which intrinsic muscles nerves does the brachial plexus supply?

Subscapular, suprascapular, musculocutaneous, axillary, radial, median, and ulnar nerves.

What type of nerve is the subscapular nerve (sensory, motor, or both)? Where is it located, and which muscle does it supply?

Motor nerves only

Located at the medial aspect

Supply subscapularis muscle

What type of nerve is the suprascapular nerve (sensory, motor, or both)? Where is it located, and which muscle does it supply?

Motor nerve only

Located at the lateral aspect

Supplies supraspinatus and infraspinatus muscles

Which nerve is shown in this picture?

Musculocutaneous nerve

What type of nerve is the musculocutaneous nerve (sensory, motor, or both)? Where is it located, and which muscles does it supply, and how do they function?

Sensory:

1. Cranial & medial aspect of elbow

2. Medial aspect of antebrachium.

Motor:

1. Biceps brachii

2. Brachialis

What happens if there is damage to the musculocutaneous nerve? Is there any compensation?

No compensation → Loss of elbow flexion

Which nerve is shown in this picture?

Axillary nerve

• Located between teres major and subscapularis

Where else can the axillary nerve be found besides the teres major?

Deep to the deltoid muscle

What type of nerve is the axillary nerve (sensory, motor, or both)? Where is it located, and which muscles does it supply, and how do they function?

Sensory:

1. Lateral aspect of shoulder and brachium

Motor:

1. Deltoid

2. Teres major

What happens if there is damage to the musculocutaneous nerve? Is there any compensation?

Yes

Should flexor can be compensated by latissimus doors and long head triceps

= !! Even axillary nerve is damaged, the shoulder of animals can still be fixed !!

What type of nerve is the median and ulnar (sensory, motor, or both)? Where is it located, and which muscles does it supply, and how do they function?

Sensory:

1. Caudal & palmar aspect limb

2. Dorsal aspect 5th digit

Motor:

1. All carpal & digital flexor

What happens if there is damage to the median and ulnar nerve? Is there any compensation?

No compensation → Loss of distal limb flexion

How does the radial nerve run?

The radial nerve originates from the medial aspect of the scapula → Passes caudal to the shoulder → Follows the musculospiral groove of the humerus → Passes through the triceps

What type of nerve is the radial (sensory, motor, or both)? Where is it located, and which muscles does it supply, and how do they function?

Sensory;

1. Dorsal & cranial aspect limb, except dorsal aspect 5th digit

Motor:

1. All extensor of carpus and digits

2. Triceps

What happen if the proximal level of radial nerve damage?

• Motor:

  All extensor muscles affected → Cannot extend elbow, carpus and digits

• Sensory:

  Sensory losses of dorsal + cranial aspect of limb, except 5th digit

What happen if the distal level of radial nerve damage?

• Motor:

  Triceps intact → Can still extend elbow

  Extensor of carpus and digits affected → Cannot extend the carpus and digits

• Sensory:

  Sensory losses of dorsal + cranial aspect of limb, except 5th digit

What happen if brachial plexus damage?

Motor:

• Trapezius, Rhomboideus and Brachiocephalius are not supplied by the brachial plexus → Can still protract and abduct the limb

• Cannot retract/ adduct/ extend/ flex limb + weight bearing

Sensory:

• No cutaneous sensation on limb or lateral thorax to level of 3rd intercostal space