Muscles of the thoracic limb (Extrinsic muscles)

Question 1

What are extrinsic muscles? (3)

Answer 1

• attach limb to trunk (thoracic wall & rib cage)
• move limb with respect to trunk & vice versa
• for shoulder movement & stabilization

Question 2

What is synsarcosis?

Answer 2

attachment of limb to axial skeleton with no conventional joint

Question 3

What are the 5 superficial extrinsic muscles?

Answer 3

• Brachiocephalicus
• Omotransversarius (extend from neck to shoulder)
• Trapezius
• Latissimus dorsi (sling/attach forelimb to trunk)
• Superficial pectoral

Question 4

What are the 3 deep extrinsic muscles?

Answer 4

• Rhomboideus (beneath trapezius)
• Serratus ventralis (beneath latissimus dorsi)
• Deep pectoral (lies partly beneath superficial pectoral)

Question 5

Brachiocephalicus is divided into? (2)

Answer 5

• Cleidocephalicus (Cleidocervicalis & cleidomastoideus)
• Cleidobrachialis

Question 6

Origin, insertion & actions of brachiocephalicus

Answer 6

• OR – Cervical and mastoid
• IN – cranial part of the distal third of humerus
• Actions – draw neck, extend limb & shoulder joint

Question 7

Origin, insertion & actions of cleidocephalicus

Answer 7

• OR – clavicular intersection
• IN – cervical vertebrae, mastoid bone

Question 8

Origin & insertion of cleidobrachialis

Answer 8

• OR – clavicular intersection
• IN – cranial part of the distal third of humerus

Question 9

Origin, insertion & actions of omotransversarius

Answer 9

OR – atlas (transverse wing)
* IN – distal end of the spine of scapula
* Actions – advance limb & extend neck

Question 10

Trapezius can be divided into 2 parts which are … and the action is?

Answer 10

• Cervical part
• Thoracic part
• Action – stabilize shoulder joint

Question 11

Origin & insertion of cervical part of trapezius

Answer 11

• OR – spine of the cervical vertebrae
• IN – spine of the scapula

Question 12

Origin & insertion of thoracic part of trapezius

Answer 12

• OR – spine of the thoracic vertebrae
• IN – spine of the scapula

Question 13

Superficial pectoral muscles are dived into 2 parts which are

Answer 13

• descending
• transverse

Question 14

Origin, insertion & actions of superficial pectoral

Answer 14

OR – cranial part of the sternum
* IN – proximal part of the humerus, near the deltoid tuberosity
* Action – mainly adduction, aids protraction & retraction of forelimb

Question 15

Latissimus dorsi is superficially covered by the

Answer 15

cutaneous trunci muscle

Question 16

Origin, insertion & actions of latissimus dorsi

Answer 16

• OR – thoracolumbar fascia, spinous
  process of the TL vertebrae
• IN – teres major tuberosity of
  humerus
• Actions – flexor of shoulder joint & retractor of forelimb

Question 17

Rhomboideus is divided into 2 in horses & ruminants, and 3 in carnivores

Answer 17

• Capitis (carnivores only), cervical and thoracic
• Hump in certain species – camel and brahman cattle

Question 18

Origin, insertion & actions of rhomboideus

Answer 18

• OR – from the polls to withers (skull to vertebrae)
• IN – dorsal border, medial side of the scapula
• Actions – raise limb, attach limb to trunk

Question 19

Serratus ventralis (large, fan shaped) can be divided into 2 parts and the actions are

Answer 19

• Cervical part
• Thoracic part
• Actions – support trunk & depress scapula

Question 20

Origin & insertion of cervical part of serratus ventralis

Answer 20

• OR – transverse process of the last 5 cervical vertebrae
• IN – dorsomedial aspect of scapula

Question 21

Origin & insertion of thoracic part of serratus ventralis

Answer 21

• OR – first 8/9 thoracic ribs
• IN – dorsomedial aspect of the scapula

Question 22

Origin, insertion & actions of deep pectoral

Answer 22

• OR – distal part of the sternum
• IN – caudomedial aspect of distal
  humerus
• Action – retractors of the forelimb