Anatomy of the Canine Spine

Original Editor - Ansi van der Walt Top Contributors -

Joints and Ligaments of the Skull[edit | edit source]

Temporo-mandibular joint:[1]

  • A condylar joint, with an articular disc, that sits between the mandibular condyles and the mandibular fossa of the temporal bones
  • It has a loose joint capsule with thickening, which forms a lateral ligament
  • The temporals muscle closes the jaw and the joint is innervated by cranial nerve V

Mandibular symphysis

Joints of the hyoid apparatus:[1]

  • Tympanohyoid cartilage - skull (a syndesmosis joint)
  • Interhyoid joints (synovial joints)
  • Thyrohyoid bone - cranial cornu of thyroid cartilage (synovial joint)

[2]

Canine Spine[edit | edit source]

The anatomy of the canine skull and spine is quite similar to the human spine. Like in people, the canine spine supports weight and encloses the spinal cord. The spine is located along the dorsal / top side of the canine's body and runs from the base of the head to the end of the tail.[3]

Figure 1. The Canine Skeleton

The canine spine is divided into five regions: cervical, thoracic, lumbar, sacral, and caudal. There are 7 cervical vertebrae, 13 thoracic vertebrae, 7 lumbar vertebrae and 3 sacral vertebrae. The number of caudal vertebrae varies according to the species.[4]

Cervical vertebrae[edit | edit source]

The atlas and axis are cervical vertebrae 1 and 2.

The atlanto-occipital joint is a condylar modified synovial hinge joint. The capsule of the joint is strengthened by three thickenings: dorsal, ventral, and lateral.[1] The transverse process of the atlas is the wing that allows the articulation of the occipital condyles and the spine.The atlas and axis are fused in embryonic life.[4] The transverse atlantal ligament holds the dens of the axis against the ventral arch of the atlas.[1]

The axis is the second and longest cervical vertebra. The atlantoaxial joint is a pivot joint and has a loose joint capsule. The dens of the axis is connected to the occipital bone through the apical ligament.[1]

The cervical vertebrae are obliquely oriented in the transverse plane. The cranial articular processes face dorsomedially whereas the caudal articular processes face ventrolaterally. [1]

The nuchal ligament is a paired band of connective tissue that connects the spinous processes of cervical vertebrae to the spinous processes of thoracic vertebra (from C1 to T1).[4][1] The canine ligamentum flavum, dorsal longitudinal ligament and, ventral longitudinal ligament are similar to those in people:

  • The ligamentum flavum connects the lamina of adjacent lamina
  • The anterior longitudinal ligament attaches to the front of each vertebra
  • The posterior longitudinal ligament runs along the posterior aspect of spine and inside of the spinal cord[1]
Muscles of the cervical spine (table extracted from a presentation of Ansi Van Der Walt )[1]
Muscle Origin Insertion Innervation Action
Omotransversarius Lower spine of scapula Wing of atlas Ventral branches of local cervical spinal nerve Advances limb

Moves neck laterally

Brachiocephalicus The clavicle divides the muscle into two:

cleidobrachialis and cleidomastoideus

Cleidobrachialis Clavicular intersection Crest of the humerus Axillary nerve Advances limb

Adducts Limb

Cleidomastoideus Clavicular intersection Mastoid process of the temporal bone Ventral branch of the accessory nerve

(cranial nerve XI)

Forms dorsal border of jugular groove

Advances limb

Flexes neck

Turns head

Sternocephalicus

(sternomandibularis)

Manubrium of the sternum Mastoid part of temporal bone

Nuchal crest

Ventral branch of Accessory nerve (Cranial nerve XI) Forms ventral border of jugular groove

Flexes neck

Turns head

Opens mouth

Omohyoideus Subscapular Fascia Lingual process of basihyoid bone Spinal nerve C1 Forms medial border of jugular groove

Retracts basihyoid bone and tongue

Trapezius (cervical and thoracic parts) Nuchal ligament and supraspinous ligament of C2-10 Cervical part: entire scapular spine

Thoracic part: dorsal third of scapular spine

Dorsal branch of accessory nerve (cranial nerve XI) Advances thoracic limb

Abducts thoracic limb

Elevates shoulder

Rhomboiudeus muscle (cervical and thoracic) Nuchal ligament and dorsoscapular ligaments of C2-T8 Scapular cartilage Local thoracic nerve

Local cervical nerve

Elevates neck

Draws scapula cranially and dorsally

Serratus ventralis cervicis Transverse processes of C4-7 Scapular cartilage and medial scapula Ventral branches of local cervical nerve Supports trunk between forelimbs

Raises neck when the limb is fixed

Splenius (capitis and cervicis) Nuchal ligament and spinous processes of T3-5 via the thoracolumbar fascia Nuchal crest and the mastoid process of temporal bone Dorsal branch of accessory nerve (cranial nerve XI) and dorsal branch of local spinal nerve Extends neck

Elevates neck

Bends neck laterally

Longissimus

(cervicis,capitis, atlantis)

Transverse processes of cervical and thoracic vertebrae Wing of atlas and mastoid process of temporal bone Dorsal branches of local spinal nerve Elevates head and neck

Bends head and neck laterally

Stabilizes and extends vertebral column

Semispinalis capitis Articular processes of C2/3-7 and transverse processes of T1-6/7 Occipital bone Dorsal branches of local spinal nerve Elevates head and neck

Bends head and neck laterally

Longus capitis Transverse processes of C3-5 Mastoid process Ventral branch of local spinal nerve
Longus colli
cervical part Transverse processes of C3-7 Ventral tubercle of atlas and bodies of cervical vertebrae Ventral branches of local spinal nerve Flexes head
thoracic part Bodies of T1-6 Transverse processes of C6-7 Ventral branches of local spinal nerve Flexes head

Bends head laterally

Obliquus capitis caudalis Spinous process of the axis Wings of the atlas Dorsal branch of C2 Rotates atlas and head
Rectus capitis dorsalis muscle
major Spinous process of the axis Nuchal crest Dorsal branch of C1 Elevates head
minor Dorsal arch of the atlas Occipital bone Dorsal branch of C1 Elevates head
Scalenes

(composed of two unequal parts and the lower one is larger)

From the transverse process of the last four cervical vertebrae Into the anterior border and outer surface of the first rib Assists inspiration by drawing the first rib forward

With rib fixed draws the neck downward and to one side

Thoracic vertebrae[edit | edit source]

The thoracic vertebrae differ from other vertebrae in a number of ways. The thoracic vertebrae articulate with the corresponding rib (i.e. T1 to rib 1). Each thoracic vertebra has a short body, flattened extremities, short articular processes and a long spinous process. The caudal articular processes of the thoracic vertebrae face ventrally and are at the base of the spinous process. The cranial articular processes of the thoracic vertebrae are oval facets on the arch of vertebrae and face dorsally. All thoracic vertebrae have a pair of costal facets on the dorsal body (except T13) forming costal fovea. There are costal facets on the transverse processes of the vertebrae and cranial and caudal fovea on the extremities of the vertebral bodies.[5] The 11th thoracic vertebra is also known as the anticlinal vertebra. The anticlinal vertebra is the point at which vertebral anatomic features change and the spinous process becomes perpendicular to the body and the preceding vertebra incline caudally. [6]

[7]

The costovertebral joint has two articulations between the rib and the vertebral column. The head of the rib articulates with the cranial and costal facets of the adjacent vertebrae and is a ball and socket synovial joint. Similarly, the tubercle of the rib articulates with the transverse process of the vertebra and is a plane synovial joint. The ligaments of the costovertebral joint are the radiate ligament of the head, inter capital ligament (connects the head of the pair of opposite rib), costotransverse ligaments and ligament of the neck.[1]

Lumbar spine[edit | edit source]

Lumbar vertebrae are more uniform and longer in shape than the thoracic vertebrae.[4] The cranial articular process of the lumbar spine is fused with the mamillary processes and the articular processes are concave dorsally and mostly in sagittal alignment. The caudal processes are convex ventrally and correspond with the convexity of cranial articular processes. The lumbar vertebrae are differentiated from the thoracic vertebrae by their lack of costal facets. The lumbar spine allows flexion and extension of the spine. Lateral flexion and rotation are very limited, especially at the L4-L5 due to the intertransverse joints. [1]

Ligaments of the thoracolumbar joint[edit | edit source]

  • The dorsal longitudinal ligament forms a part of the floor of the vertebral canal from the axis to the sacrum and prevents hyperflexion of the spine[1]
  • An interspinous ligament connects the spines of adjacent vertebrae from the axis to the sacrum[1]
  • Intertransverse ligament[1]
  • Interarcuate ligament / ligamentum flavum / yellow ligaments are the elastic ligaments filling dorsal spaces between the arches of adjacent vertebrae[1]
  • The supraspinous ligament is made up of heavy bands of the connective tissue that run over the top of the spinous processes (T2/T3 caudally). This ligament prevents abnormal separation of spinous processes during flexion of the spine. The supraspinous ligament is a direct continuation of the funicular part of the nuchal ligament[1]
  • The ventral longitudinal ligament runs ventrally from axis to sacrum. It widens caudally and is strongest in the lumbar spine. This prevents hyperextension of the spine[1]

Sacral vertebrae[edit | edit source]

The sacrum is formed by the fusion of the sacral vertebrae and articulates with the pelvic girdle.The sacrum narrows and forms a curve caudally and forms a concave surface for the pelvic cavity.[4]

Caudal vertebrae[edit | edit source]

The number of caudal vertebrae differs from species to species. [4]

Muscles of the trunk (table extracted from a presentation of Ansi Van Der Walt [1]
Muscle Origin Insertion Innervation Action
Lattisimus dorsi Supraspinous ligament from T3 and thoracolumbar fascia Teres major tuberosity of humerus Thoracodorsal nerve Flexes shoulder and draws limb caudally

Draws trunk cranially when limb is flexed

Serratus ventralis thoracis Ribs 1-8/9 Scapular cartilage and medial scapula Long thoracic nerve Supports trunk between forelimbs

Raises neck when limb is flexed

Serratus dorsalis
cranialis Supraspinous ligament Cranial border of ribs 5-11 Intercostal nerve Muscle of inspiration
caudalis Thoracolumbar fascia Caudal border of ribs 11-13 Intercostal nerve Muscle of expiration
External intercostal muscles Muscles run caudodorsally in the intercostal spaces Intercostal nerve Muscles of inspiration
Internal intercostal muscles Muscles run craniodorsally in the intercostal spaces Intercostal nerve Muscles of expiration
External abdominal oblique muscle Thoracolumbar fascia and lateral aspect of ribs 4-13 Linea alba

Prepubic tendon

Pelvic tendon

Coxal tuber

Inguinal ligament

Ventral branches of lumbar nerve and local intercostal nerve Abdominal press

Flexes the trunk

Internal abdominal oblique muscle Coxal tuber and inguinal ligament Linea alba,

Prepubic tendon

last rib

Cartilages of ribs 14-18

Ventral branches of lumbar nerve and local intercostal nerve Abdominal press

Flexes the trunk

Transversus abdominis Medial surface of costal cartilages 7-18 and transverse processes of lumbar vertebrae Linea alba Ventral branches of lumbar nerve and lumbar intercostal nerve Abdominal press

Flexes the trunk

Rectus abdominis lateral surface of costal cartilages 4-9 Prepubic tendon and head of the femur (via accessory ligament) Ventral branches of lumbar nerve and local intercostal nerve Abdominal press

Flexes the trunk

Flexes lumbar spine

and lumbosacral joint

Longisimus thoracis and lumborum Spinous processes of thoracic, lumbar and sacral vertebrae and wings of illium Transverse processes of vertebrae and tubercles of rib Dorsal branches of lumbar nerve Stabilises and extends vertebral column
Semispinalis thoracis and lumborum From the sacrum and from the articular processes of the lumbar vertebrae and from the transverse processes of the dorsal vertebrae Each slip inserts into the spinous process of the third or fourth vertebra in front of the one from which it arises Dorsal branches of local spinal nerve To fix the bones during the action of the large spinal muscles, and to assist in extending the spine
Iliocostalis thoracis and lumborum Runs obliquely between the transverse processes of the vertebrae to the bodies of the adjacent vertebrae and/or the tuberosities of the rib Dorsal branches of local spinal nerves Expiration

Thoracolumbar extension

Cutaneous trunci Superficial trunk fascia

(from the withers to the fold of the flank)

Superficial shoulder fascia and medial surface of the humerus Lateral thoracic nerve and intercostobrachial nerve Moves the skin of the abdomen (and the trunk )
Longissimus thoracis and lumborum muscle are continuous from pelvis through thorax Spinous processes of thoracic, lumbar and sacral vertebrae and wings of illium Transverse processes of vertebrae and tubercles of ribs Dorsal branches of local spinal nerve Stabilises and extends vertebral column
Multifidus lumborum muscle (continuous with thoracis and cervicis) Articular processes of each vertebra from C2 to sacrum Spinous process of the preceding vertebra Dorsal branches of local spinal nerve Stabilises vertebral column

Rotates vertebral column

Psoas major muscle

Part of iliopasoas muscle

Lumbar transverse processes and ventral surface of last two ribs Lesser trochanter of femur (as fused iliopsoas muscle) Ventral branches of lumbar and local intercostal nerve and lumbar plexus Rotates pelvic limb outwards

Flexes hip and advances limb

Stabilises vertebral column when limb is fixed

References[edit | edit source]

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 Van der Walt A. Managing Disorders of the Canine Spine Course. Physioplus, 2021
  2. VNatomy. VNatomy - Canine Skull overview. Available from: https://www.youtube.com/watch?v=xzYrXq6aGdc [last accessed 14/3/2021]
  3. Cuteness. Canine Spine Anatomy.(Accessed on 2021/03/06). Available from https://www.cuteness.com/article/anatomy-dog-brain
  4. 4.0 4.1 4.2 4.3 4.4 4.5 Wikivet. Spinal Column - Anatomy & Physiology. Accessed on:2021/03/06. Available from: https://en.wikivet.net/Spinal_Column_-_Anatomy_%26_Physiology
  5. IMAIOS.Vet Anatomy. Thoracic vertebrae - Vertebrae thoracicae. Accessed on: 2021/03/10. available from https://www.imaios.com/en/vet-Anatomy/Vet-Anatomical-Part/Thoracic-vertebrae
  6. IMAIOS. Vet Anatomy. Anticlinal vertebra - Vertebra anticlinalis. Accessed on 2021/03/10. Available from: https://www.imaios.com/en/vet-Anatomy/Vet-Anatomical-Part/Anticlinal-vertebra
  7. Peabodydvm.Canine Skeleton overview. Available from https://youtu.be/Crg4jKtHRqk [last accessed 14/3/2021]