A23 - The vertebral column as a whole, epaxial and hypaxial muscles, statics of the trunk

Question 1

Give the general structures of a vertebrae

Answer 1

• Corpus vertebrae
  
  • Extremitas cranialis [=Caput vertebrae] (cranial covex)
  • Extremitas caudalis [=Fossa vertebrae] (caudal concave)
  • Crista ventralis
• Arcus vertebrae
  
  • Pediculus arcus vertebrae
  • Lamina arcus vertebrae
• Foramen vertebrale
• Incisura vertebralis cranialis
• Incisura vertebralis caudalis
• Foramen intervertebrale
• Processus spinosus
• Processus transversus
• Processus articularis cranialis
• Processus articularis caudalis
• Processus mamillare (on the arch of Th and L vertebrae, between proc. articularis cranialis and proc. articularis caudalis)
• Processus accessori
  
  • Proc. articularis caudalis → proc. transversus
  • ​Sus: caudal thoracic vertebrae
  • Car: Thoracic and lumbar vertebrae

Question 2

Give the number of vertebrae in different species

Answer 2

Question 3

Curvatures in the vertebral column

Answer 3

• In domestic animals, the vertebrae form a chain arranged horizontally, along which three major curvatures are recognized:
  
  1. Dorsal convex curvature (head → neck)
  2. Dorsal concave curvature (neck → chest)
  3. Dorsal convex curvature (thorax → lumbar region)

Question 4

Definition of epaxial muscles

Answer 4

• Muscles of the axial zone, which elevate, laterally flex and rotate the cervical, thoracic and lumbar vertebrae
• Innervation: dorsal branches of the spinal nerves

Question 5

Definition of hypaxial muscles

Answer 5

• Mainly in the cervical region
• Muscles which depress the cervical vertebrae
• Number of muscles are small compared to epaxional musculature

Question 6

Give the epaxial muscles

Answer 6

Long muscles:

1. M. splenius (superficial layer)
   
   • Pars capitis
   • Pars cervicalis
2. M. iliocostalis (middle layer)
   
   • Pars thoracica
   • Pars lumborum (ca)
3. ​M. longissimus (middle layer)
   
   • Pars lumborum
   • Pars thoracis
   • Pars cervicalis
   • Pars atlantis
   • Pars capitis
4. M. spinalis et semispinalis (deep layer)
   
   • Pars thoracis
   • Pars cervicalis
5. M. semispinalis capitis (deep layer)
   
   • M. biventer cervicis
   • M. complexus
6. M. multifidi (deep layer)
   
   • Pars lumborum
   • Pars thoracis
   • Pars cervicalis

Short muscles:

1. ​M. intertransversarii
2. Mm. interspinales
3. Mm. rotatores
   
   • Pars brevis
   • Pars longus

Question 7

M. splenius

Answer 7

• Divided into (ø ca):
  
  1. Pars capitis
  2. Pars cervicalis
• Origin:
  
  • Th1-3, processus spinosus
  • Lig. nucahe, caudal end
• Insertion:
  
  • Crista nucha
  • Mastoid part of os temporale
• Action:
  
  • Bilateral: Extend the neck, raises head
  • Unilateral: Draw head laterally
  • Eq: Movements of head when galopping, maintains balance when jumping

Epaxial

Question 8

M. iliocostalis (lateral)

Answer 8

• Ca, divided into:
  
  1. Pars lumborum (ca)
  2. Pars thoracica
• Origin: Crista iliaca and fascial sheet
• Insertion:
  
  • Eq, sus: Fuse with m. longissimus
  • Others:
    
    • Ribs on a**ngulus costae
    • C7 vertebra, processus transversus
• Action:
  
  • Fix/stabilize the vertebral column
  • Lateral flexion and expiration

Epaxial

Question 9

M. longissimus (medial)

Answer 9

• Divided into:
  
  1. Pars lumborum
  2. Pars thoracis
  3. Pars cervicalis
  4. Pars atlantis
  5. Pars capitis
• Origin: Sacrum and ilium
• Insertion:
  
  • _Lumborum and thoraci_s:
    
    • Processus transversus/mamillaris/spinosus of lumbar and thoracic vertebrae
    • Angula costae
  • Cervicis: Between processus transversus of thoracic vertebrae and cervical vertebrae
  • Atlantis: Between thoracic/cervical vertebrae and ala atlantis
  • Capitis: Processus mastoideus of temporal bone
• Action:
  
  • ​Bilateral: Stabilize and flex head, neck and back dorsally ! increase wightbearing capasity
  • Unilateral: Flex the vertebral column laterally, rotate atlantoaxial joint

Epaxial

Question 10

M. spinalis or M. spinalis et semispinalis

Answer 10

• M. spinalis (eq, sus)
• M. spinalis et semispinalis (ca, ru)
• Divided into:
  
  1. Pars thoracis
  2. Pars cervicalis
• Origin: Lumbar vertebrae, processus spinosus
• Insertion: C2-C3, processus spinosus
• Action:
  
  • ​Bilateral: Extend/stabilize the back, elevate the neck
  • Unilateral: Flex nec/back laterally

Epaxial

Question 11

M. semispinalis capitis

Answer 11

• Divided into:
  
  • M. biventer cervicis (dorsal)
  • M. complexus (ventral)
• Origin:
  
  • M. biventer cervicis: Th2-4, processus transversus
  • M. complexus: C3-Th1, processus articularis caudalis
• Insertion: Os occipitale (crista nuchae, protubiranta occipitalis externa)
• Action:
  
  • Bilateral: Extends neck
  • Unilateral: Flexes head and neck laterally

Epaxial

Question 12

Mm. multifidi

Answer 12

• Divided into:
  
  1. Pars lumborum
  2. Pars thoracis
  3. Pars cervicalis
• Origin: Processus transversus
• Insertion: Cranial vertebrae, processus spinosus or arcus dorsalis
• Action: Stabilize the vertebral column in junction with other muscles
  
  • Lumbar region: Flex the back ventrally
  • Thoracic region: Rotate the vertebral column
  • Cervical region: Elevate/flex the neck laterally

Epaxial

Question 13

Mm. intertransversarii

Answer 13

• Extend mainly between the processus transversus of adjacent vertebrae
• Action: Stabilize and flex cervical and lumbar vertebral column

Epaxial

Question 14

Mm. interspinales

Answer 14

• Runs between the adjacent processus spinosus
• Action:
  
  • ​Stabilize the vertebral column
  • Ca: flex the spine ventrally

Epaxial

Question 15

Mm. rotatores

Answer 15

• Divided into:
  
  1. Pars brevis
  2. Pars longus
• Cranial part of thoracic vertebrae, between processus spinosus/transversus

Epaxial

Question 16

Give the hypaxial muscles

Answer 16

1. M. longus colli
   
   1. ​Pars thoracis
   2. Pars cervicis
2. M. scalenius
   
   1. ​Pars ventralis (ø ca)
   2. Pars medius
   3. Pars dorsalis (ø eq)

Question 17

M. longus colli

Answer 17

• Divided into:
  
  1. Pars thoracis
  2. Pars cervicalis
• T**h5/6, corpus vertebrae → atlas
• Action: Flex the neck

Hypaxial

Question 18

M. scalenius

Answer 18

• Divided into:
  
  • Pars ventralis (ø ca)
  • Pars medius
  • Pars dorsalis (ø eq)

In dog:

• Origin:
  
  • ​M. scalenus d__orsalis: C4-6, processus transversus
  • M. scalenus medius: C6-7, processus transversus
• Insetion:
  
  • ​Dorsal:
    
    • ​Dorsally situated: Rib 1-4
    • Ventrally situated: Rib 1-9
  • M. scalenus medius: Rib 1, cranial border
• Action:
  
  • Bilateral: Flex the neck ventrally
  • Unilateral: Flex the neck laterally
  • Inspiratory muscle

Question 19

Statics of the trunk

Answer 19

• Statics: Maintains the equilibrium of the body in a state of rest or in motion
• Dynamics: Analyses the movement of the body during locomotion
• Eq: More weight (55%) is carried by the forelimbs

“Bow and string” theory:

• ​Bow: The thoracolumbar vertebrae, their articulations and the ligaments and muscles provides a flexible structure
  
  • Dorsally it has a convex arch which gets its elasticity and nuchael and supraspinous ligaments
  • The two ends of the bow are fixed by:
    
    • Sternum
    • Linea alba
    • Abdominal muscles
• String: Abdominal muscles, which reaches from the thorax to the plevis
• The bow is indirectly attached to the string by interosition of the:
  
  • Cranially: Thoracic skeleton
  • Caudally: Pelvic bones
• The string attaches all along the bow
  
  • Abdominal wall region it is formed by:
    
    • Linea alba
    • Abdominal muscles
    • Aponeurosis
  • Thorax it is formed by:
    
    • Sternum
    • Ribs
    • Intercostl muscles
• Contraction of the abdominal muscle → flexion of bow
• Contraction of the epaxial muscles → straightens the bow
• Weight of the viscera attached to the vertebral column → straightens the bow
• Weight of the viscera on the abdominal muscles → bends the bow
• “Bow and string theory” can extend into the cervical region, but the curve is in the opposite direction to that of the thoracolumbar region
  
  • Cervical vertebrae and their articulations consititue the bow
  • Nuchal ligament acts as the string
• Role of the cantilevers (utstikker): equalize centrifugal push
• Division of the cantilevers:
  
  • Front: head and neck
  • Hind: sacrum and tail
    
    • Role: pusch against the bow, allowing the limb to reach gallop
• Sacrum serve as base of attachment of muscle mass of hindlimb, for mobile connection with last lumbar vertebra but immobile with pelvis
• Speed increases → thrust increases → lowering of head & lens neck muscles → reastablish equilibrium of body as a whole