Practical topic 12

Question 1

Give the muscles of the thoracic girdle (except m. sternocleidomastoideus)

Answer 1

Superficial:

1. M. trapezius
2. M. omotransversarius
3. M. latissimus dorsi
4. Mm. Pectoralis superficialis

Deep:

1. M. pectoralis profundus/ Deep pectoral muscle/M. pectoralis ascendes
2. M. rhomboideus
3. M. serratus ventralis

Question 2

M. trapezius

Answer 2

Origin:

• Between c3-th9 region.
• Pars cervicalis:
  
  • From raphe of neck.
• Pars thoracica:
  
  • From supraspinous ligament.

Insertion:

• Pars cervicalis:
  
  • Proximal 3/4 of spina scapula (distally you can find omotransversius).
• Pars thoracis:
  
  • Proximally third of spina scapula.

Action:

• Supports trunk.
• Elevates (lifts) forelimb.
• Draws forelimb cranially.

Question 3

M. Omotransversarius

Answer 3

Origin: Distal part of spina scapula, then runs under m. sternocleidomastoideus.

Insertion: Caudal border of ala atlantis on atlas.

Action:

• If limb is free: draws shoulder cranially.
• If limb is fixed: flexes neck laterally.

Question 4

M. Latissimus dorsi

Answer 4

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 5

M. Pectoralis superficialis

Answer 5

Origin:

• M. pectoralis descendens:
  
  • Manubrium sterni
• M. pectoralis transversus:
  
  • From sternebrae 1-3.

Insertion:

• Crista tuberculi majoris
• Upper part of crista humeri.

Action:

• Ventral connection to forelimb.
• Adduction.
• Draws limb cranially or caudally depending its position.

Question 6

M. Pectoralis profundus

Answer 6

Origin:

• All sternebrae of sternum.
• Costal cartilages of true ribs.

Insertion:

• Main part inserts on tuberculum minor of humerus.
• A small aponeurosis joins to tuberculum majus.

Action:

• Supports trunk.
• Behaving as a strong retractor (draws limb caudally)
• Adductor of forelimb.

Question 7

M. Rhomboideus

Answer 7

Origin:

• Pars capitis:
  
  • 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 8

M. Serratus ventalis

Answer 8

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.