Structures and function of the Vertebral Column 2

• Understand the components and functions of the:

  • Thoracic wall

  • Abdominal wall

  • Pelvic wall

• Describe vertebral column movements and joints.

• Recognize functional muscle groups of the vertebral column.

• Know blood vessels and nerve supply to the body walls.

Body Cavities

Thoracic Cavity

• Components include:

  • Thoracic inlet

  • Diaphragm

  • Thoracic vertebrae

  • Sternum

  • Ribcage

Abdominal Cavity

• Key features include:

  • Diaphragm

  • Pelvic inlet

  • Lumbar vertebrae

  • Muscular wall

Pelvic Cavity

• Located within the pelvis.

Relevance of Body Cavities

• Importance lies in:

  • Functions of the cavities

  • Anatomical landmarks

  • Auscultation (listening to internal sounds)

  • Surgical considerations

Thoracic and Abdominal Body Walls

Thoracic Wall Composition

• Canine ribcage consists of:

  • 13 thoracic vertebrae

  • 13 ribs

  • 12 intercostal spaces

  • 8 sternebrae forming the sternum

• Ribs articulate with:

  • Vertebrae

  • Sternum

• Thoracic wall functions:

  • Muscle attachment

  • Support

  • Protection

  • Respiration

  • Lateral compression

Movement of the Vertebral Column

Synovial Joints

• Features:

  • Articular facets: 4 per vertebra (2 cranial, 2 caudal)

  • Cranial facets are lateral/ventral to caudal facets.

• Exceptions in joints:

  • Atlanto-occipital joint

  • Sacral region

  • Caudal/coccygeal region.

• Characteristics of synovial joints influence mobility.

Specific Joints

• Atlanto-occipital Joint:

  • Connects Atlas (C1) to the occipital condyles of the skull.

  • Limited to flexion & extension (the 'Yes' joint).

• Atlanto-axial Joint:

  • Connects Atlas (C1) and Axis (C2).

  • Allows lateral rotation, no flexion/extension due to the dorsal spinous process of C2 (the 'No' joint).

• Occipito-atlanto-axial complex enables full range of motion without spinal cord damage.

Thoracic Body Wall Components

Muscles of the Thoracic Wall

• Skin and Muscular Layers:

  • Cutaneous Trunci

  • Superficial and deep fascia

  • Ribs

  • Endothoracic and pleural fasciae

• Muscle Groups:

  • Epaxial muscles (above transverse processes)

  • Hypaxial muscles (below transverse processes)

Epaxial vs. Hypaxial Muscles

• Epaxial Muscles:

  • Provide extension and lateral movement of the vertebral column.

  • Connective nuchal ligament supports the head.

• Hypaxial Muscles:

  • Contribute to flexion and lateral movement, involving ventral neck and abdominal wall muscles.

Muscles of Thoracic Wall

Epaxial Muscles - Longitudinal Groups

• Transversospinalis: medial group

• Longissimus: middle group

• Iliocostalis: lateral group

• Primary function is extension and lateral movement of the vertebral column.

Hypaxial Muscles - Major Groups

• Superficial Muscles:

  • Latissimus dorsi

  • Pectoral muscles

  • External abdominal oblique muscles

• Deep Muscles:

  • Serratus ventralis (accessory inspiratory)

Intercostal Muscles

• External Intercostal Muscles:

  • Fibres extend caudoventrally up to costochondral junction.

• Internal Intercostal Muscles:

  • Fibres extend to sternum, aiding in both inspiration and expiration.

Blood and Nerve Supply

Intercostal Supply

• Intercostal vein, artery, and nerve run along the caudal aspect of the ribs to their costochondral junction.

• They branch further to supply various parts of the thorax.

• Intercostal artery connects with the internal thoracic artery.

Respiration

• Diaphragm

  • Primary muscle for respiration:

  • Inspiration: Active process (contracts, ribs move cranially and laterally).

  • Expiration: Passive process (relaxation causes ribs to collapse).

Accessory Muscles in Inspiration

• Serratus ventralis, Scalenus, Rectus thoracis, and Serratus dorsalis cranialis enhance inhalation.

Accessory Muscles in Expiration

• Muscles assist in forced expiration by pulling the ribs caudally and medially, such as:

  • External abdominal oblique

  • Serratus dorsalis caudalis

  • Transversus thoracis

Clinical Considerations

Intercostal Spaces

• Radiographic interpretation and auscultation focused on the 5th intercostal space (olecranon overlies).

Surgery Considerations

• Surgical challenges involving latissimus dorsi, and consideration of the internal thoracic artery.

Abdominal Wall Muscles - Ventral View

• Linea Alba: fibrous cord connecting sternum to pelvis.

• Rectus Abdominus Muscle:

  • Origin at the sternum, insertion at the pelvis with cranio-caudal fibres.

Inguinal Canal

• Important structures include:

  • External pudendal artery and vein

  • Genitofemoral nerve

  • Male: testes and spermatic cord

  • Female: vaginal process (rudimentary).

Blood Supply - Superficial and Deep

Deep Blood Supply

• Cranial abdominal artery, cranial and caudal epigastric arteries, and deep circumflex iliac artery.

Superficial Blood Supply

• Cranial and caudal superficial epigastric arteries. Difficulties may arise in avoiding vessels during surgery.

Clinical Applications

• Surgical techniques for spaying in cats and performing caesarian sections in cows, along with corrections for displaced abomasum considering muscle layers.