Muscles of the thoracic limb (Extrinsic muscles) Flashcards
What are extrinsic muscles? (3)
- attach limb to trunk (thoracic wall & rib cage)
- move limb with respect to trunk & vice versa
- for shoulder movement & stabilization
What is synsarcosis?
attachment of limb to axial skeleton with no conventional joint
What are the 5 superficial extrinsic muscles?
- Brachiocephalicus
- Omotransversarius (extend from neck to shoulder)
- Trapezius
- Latissimus dorsi (sling/attach forelimb to trunk)
- Superficial pectoral
What are the 3 deep extrinsic muscles?
- Rhomboideus (beneath trapezius)
- Serratus ventralis (beneath latissimus dorsi)
- Deep pectoral (lies partly beneath superficial pectoral)
Brachiocephalicus is divided into? (2)
- Cleidocephalicus (Cleidocervicalis & cleidomastoideus)
- Cleidobrachialis
Origin, insertion & actions of brachiocephalicus
- OR – Cervical and mastoid
- IN – cranial part of the distal third of humerus
- Actions – draw neck, extend limb & shoulder joint
Origin, insertion & actions of cleidocephalicus
- OR – clavicular intersection
- IN – cervical vertebrae, mastoid bone
Origin & insertion of cleidobrachialis
- OR – clavicular intersection
- IN – cranial part of the distal third of humerus
Origin, insertion & actions of omotransversarius
OR – atlas (transverse wing)
* IN – distal end of the spine of scapula
* Actions – advance limb & extend neck
Trapezius can be divided into 2 parts which are … and the action is?
- Cervical part
- Thoracic part
- Action – stabilize shoulder joint
Origin & insertion of cervical part of trapezius
- OR – spine of the cervical vertebrae
- IN – spine of the scapula
Origin & insertion of thoracic part of trapezius
- OR – spine of the thoracic vertebrae
- IN – spine of the scapula
Superficial pectoral muscles are dived into 2 parts which are
- descending
- transverse
Origin, insertion & actions of superficial pectoral
OR – cranial part of the sternum
* IN – proximal part of the humerus, near the deltoid tuberosity
* Action – mainly adduction, aids protraction & retraction of forelimb
Latissimus dorsi is superficially covered by the
cutaneous trunci muscle
Origin, insertion & actions of latissimus dorsi
- OR – thoracolumbar fascia, spinous
process of the TL vertebrae - IN – teres major tuberosity of
humerus - Actions – flexor of shoulder joint & retractor of forelimb
Rhomboideus is divided into 2 in horses & ruminants, and 3 in carnivores
- Capitis (carnivores only), cervical and thoracic
- Hump in certain species – camel and brahman cattle
Origin, insertion & actions of rhomboideus
- OR – from the polls to withers (skull to vertebrae)
- IN – dorsal border, medial side of the scapula
- Actions – raise limb, attach limb to trunk
Serratus ventralis (large, fan shaped) can be divided into 2 parts and the actions are
- Cervical part
- Thoracic part
- Actions – support trunk & depress scapula
Origin & insertion of cervical part of serratus ventralis
- OR – transverse process of the last 5 cervical vertebrae
- IN – dorsomedial aspect of scapula
Origin & insertion of thoracic part of serratus ventralis
- OR – first 8/9 thoracic ribs
- IN – dorsomedial aspect of the scapula
Origin, insertion & actions of deep pectoral
- OR – distal part of the sternum
- IN – caudomedial aspect of distal
humerus - Action – retractors of the forelimb
