A8 - Muscles of the thoracic and pelvic girdle

Question 1

Give the superficial muscles of the pectoral girdle

Answer 1

Question 2

M. trapezius

Answer 2

• Divided into:
  
  1. Pars cervicalis
  2. Pars thoracica
• Origin: C3 → Th9 region
  
  • Pars cervicalis: From raphe of neck
  • Pars thoracica: from supraspinous ligament
• Insertion: Spina scapula
  
  • Pars cervicalis: proximal ³/₄ of spina scapula
  • Pars thoracica: proximal thrid of spina scapula
• Action: To elevate (lift) and abduct the forelimb, stabilize the shoulders

Question 3

Give the division of m. sternocleidomastoideus

Answer 3

Question 4

M. sternocephalicus

Answer 4

• Origin: manubrium of the sternum
• Insertion:
  
  • ​Divided into:
    
    1. M. sternomastoideus
       
       • Mastoid part of the temporal bone
    2. M. sterno occipitalis
       
       • Nucheal crest of the occipital bone
• Action: Draw the head and neck to the side

Question 5

M. brachiocephalicus

Answer 5

From humerus to head and neck

• Divided into:
  
  1. M. cleidobrachialis
     
     • Origin: Clavicle
     • Insertion: Distal part of the crest of humerus
  2. M. cleidocephalicus
     
     1. M. cleidomastoideus
        
        • Origin: Mastoid process of temporal bone
        • Insertion: Iscription clavicularis
     2. M. cleidocervicalis
        
        • Origin: The dorsal midline over the cranial half of the neck
        • Insertion: Inscription clavicularis
• Action:
  
  • If forelimb is fixed: unilateral contraction of the muscle moves head into the lateral direction, bilateral contraction fixes head and neck (or bends downward)
  • If limb is free (it’s in an elevated position), it will move forelimb cranially

Question 6

M. omotransversarius

Answer 6

• Origin: The ventral part of the scapular spine
• Insertion: The caudal border of the wing of the atlas (eq: also the transverse proc. of the 2-4 cervicals aswell)
• Action: To advance the limb (draw the shoulder cranially) or flex the neck laterally

Question 7

M. latissimus dorsi

Answer 7

• Origin:
  
  • Superficial layer of thoracolumbar fascia
  • From spinous process of last 7-8 thoracic and lumbar vertebrae
  • Proximally to the last few ribs
• Insertion: Tuberositas m. teres major (together with m. Teres major)
• Action:
  
  • Draws free limb caudally
  • With teres major: Flexes shoulder

Question 8

Mm. pectoralis superficialis

Answer 8

• Origin:
  
  • M. pectoralis descendens: Manubrium sterni
  • M. pectoralis transversus: From sternebrae 1-3.
• Insertion:
  
  • Crista tuberculi majoris of humerus
  • Upper part of crista humeri
• Action:
  
  • Ventral connection to forelimb
  • Adduction
  • Draws limb cranially or caudally depending its position.

Question 9

Give the deep muscles of the pectoral girdle

Answer 9

Question 10

M. pectoralis profundus

Answer 10

• Origin:
  
  • All sternebrae
  • Costal cartilage of true ribs
• Insertion:
  
  • Ca: Greater tubercle
  • Eq: The major and minor tubercles of the humerus
  • Sus: Lesser tubercle
• Action: Support the trunk, strong retractor and adductor of the forelimb

Question 11

M. subclavius

Answer 11

Ø Car

• Origin: The manibrium and adjacent parts of the sternum and ribs
• Insertion: The cranial border of the scapula and the clavicle

Question 12

M. rhomboideus

Answer 12

• Origin:
  
  • Pars capitis (ca): Crista nuca of occipital bone
  • Pars cervicis: From raphe of neck to spinous process of th1-3
  • Pars thoracis: Processus spinosus of th4-7.
• Insertion: Dorsomedial border of scapula
• Action:
  
  • Elevates limb
  • Pulls base of scapula against trunk forwards or backwards (depending on which part will contract more)

Question 13

M. serratus ventralis

Answer 13

• Divided into:
  
  1. Pars cervicalis
  2. Pars thoracis
• Origin:
  
  • Pars cervicalis: Transverse process of cervical 2-7
  • Pars thoracis: Middle of rib 1-8
• Insertion: Facies serrata on scapula (medially)
• Action:
  
  • Supports trunk
  • Helps inspiration
  • Carries shoulder cranially or caudally with respect to position of forelimb

Question 14

Give the muscles of the pelvic girdle

Answer 14

Question 15

M. psoas minor

Answer 15

• Origin: Corpus of the last few thoracic and first few lumbar vertebrae
• Insertion: Eminentia iliopubica
• Action:
  
  • When the vertebral column is fixed: To draw the pelvis into a deeper position
  • When the pelvis is fixed: To stabilize and arch the lumbar and vertebral column dorsally

Question 16

M. psoas major

Answer 16

• Origin: Corpus and transverse processes of the lumbar vertebrae
• Insertion: Trochanter minor of the femur
• Action: Draw the thigh forewards by flexing the hip and turning the stifle outwards

Question 17

M. iliacus

Answer 17

• Origin: Arising between linea arcurata and lateral border of iliac bone (sacroiliac joint)
• Insertion: Trochanter minor of femur (medially) between m. Rectus femoris and m. Pectineus (together with M. psoas major)
• Action: Enforcement of the sacroiliac joint

Question 18

M. quadratus lumborum

Answer 18

• Origin:
  
  • 11-13 thoracic vertebra ventrally
  • Last two ribs
  • Lumbar vertebra’s transverse processes
• Insertion: medial surface of iliac wing (between articular surface and cranial ventral iliac spine of tuber coxae)
• Action: fixation and dorsal flexion of vertebral column