Animal Body Function IX: Vertebral Muscles

• The presentation covers cervical, thoracic, lumbar, and juxta-vertebral muscles in Animal Body Function IX, with Ana Margarida Ribeiro presenting in March 2025.
• Focus is on extrinsic muscles of the head, juxta-vertebral neck muscles, and juxta-vertebral back muscles.

Extrinsic muscles of the head

• Functionally continue the muscles of the neck onto the head.
• Coordinate head movements, specifically at the atlanto-occipital and atlantoaxial joints.

Major Dorsal Straight Muscle of the Head (m. rectus capitis dorsalis major)

• Sits between the spine of the axis and the occiput.
• It has both deep and superficial portions.
• In carnivores and pigs, these muscles cojoin in the midline.
• In ruminants and horses, positioned lateral to the nuchal ligament.

Minor Dorsal Straight Muscle of the Head (m. rectus capitis dorsalis minor)

• Found between the atlas and the occiput.
• Work with major dorsal straight muscles to extend the atlanto-occipital joint.
• Action raises the head.

Lateral Straight Muscle of the Head (m. rectus capitis lateralis)

• Originates from the ventral surface of the wing of the atlas.
• Base of the paracondylar process of the occipital bone is its insertion point.

Ventral Straight Muscle of the Head (m. rectus capitis ventralis)

• Originates on the ventral arch of the atlas.
• It’s insertion point is on the basioccipital bone.
• Action of the muscle is to flex the atlanto-occipital joint and tilt the head together with other rectus muscles.

Cranial Oblique Muscle of the Head (m. obliquus capitis cranialis)

• Originates on the lateroventral surface and lateral border of the wing of the atlas.
• Inserts on the mastoid part of the temporal bone and the nuchal crest.
• Action is extension of the atlanto-occipital joint.

Caudal Oblique Muscle of the Head (m. obliquus capitis caudalis)

• Originates from the spinous process of the axis.
• Its insertion is on the wing of the atlas.
• When contracting bilaterally, they serve as fixators of the head.

Long Muscle of the Head (m. longissimus capitis)

• Cranial continuation of the long muscle of the neck.
• Originates on the transverse processes of the C2-C6 vertebrae.
• Insertion is on the muscular tubercle of the basioccipital bone, unites with the corresponding muscle on the opposite side in the midline.
• Action: Flexes the atlanto-occipital joint and draws the head sideways and the neck downward.
• Innervated by the Rami ventrales of the cervicales nerve.

External Fascia of the Trunk

• Superficial external fascia of the trunk covers the thorax and abdomen.
• They have no attachments with the dorsal ends of the thoracic and lumbar vertebrae.
• It covers the trapezius and latissimus dorsi muscles and portions of the pectoral muscles, omotransversarius, deltoideus, and triceps brachii.

Thoracolumbar Fascia

• Also known as deep external fascia of the trunk.
• Covers the erector spinae muscle in the thoracic and lumbar region.
• It attaches to the spinous processes of the thoracic, lumbar, and sacral vertebrae, the supraspinous ligament, the sacral tuberosity, the iliac crest, and the coxal tuberosity.
• Cranioventrally, it continues as the axillar fascia, caudally as the gluteal fascia and ventrally as the abdominal tunic.
• The superficial layer gives rise to the latissimus dorsi cranially and the two oblique abdominal muscles, and the serratus caudalis caudally.
• The deep leaf lies medial to the scapula and rhomboideus, and lateral to the erector spinae muscles.

M. Cutaneous Trunci

• This Muscle covers a great portion of the thorax and abdomen, extends out from the gluteal region to the thoracic region, slopes medially to the arm that has a deep pectoral muscle.
• Originates from the superficial gluteal fascia.
• Inserts at the axilla and on caudal border of the deep pectoral muscle.
• Action: Shakes the skin to remove foreign bodies and increase heat Production. It also tenses the skin when required.
• Nerve: Efferent supply, lateral thoracic, afferent supply, lateral thoracic and lateral branches of the intercostal nerves and the costoabdominalis, iliohypogastricus, ilioinguinlalis and genitofemorilis.

M. Latissimus Dorsi

• It is caudal to the muscles of the scapula and brachium found on the dorsal half of the lateral thoracic wall.
• Originates from the superficial leaf of the lumbosacral fascia and spinous processes of the lumbar vertebrae and the last 7-8th thoracic vertebrae.
• Originates muscularly from the last 2-3 ribs.
• It is inserted into the teres tubercle and the greater tubercle of the humerus.
• Action: moves the limb caudally and possibly medially, causes depression of the vertebral column, supports the limb.
• Draws the limb against the trunk, draws the free limb backward during flexion of the shoulder joint and decelerates forward motion of the limb.
• The nerves for that muscle are: Nn. pectorales caudales, and n.thoracodorsalis.

M. Serratus Dorsalis

• Split into cranial and caudal parts that have different innervation and different functions.

M. Serratus Dorsalis Cranialis

• Acts as the inspiratory part and lies on the dorsal surface of the cranial thorax.
• Originates at the thoracolumbar fascia and spines of the first 6-8 thoracic vertebra.
• Insertion goes to the cranial border and lateral surfaces of ribs 2-10. (cow 6-10th; horse 5-9th, pig 4-9th)
• Its action is to lift the ribs for inspiration.
• Innervation come from the intercostales.

M. Serratus Dorsalis Caudalis

• Acts as the Expiratory part of the thorax and thorax is defined by 3 relatively isolated portions.
• It originates from the Thoracolumbar fascia.
• Inserts at the Caudal border of the 11-13th ribs. (horse 11-18th, pig 11-15th, cow 10-13th).
• Action draws the last three or four ribs caudally for expiration.
• Innervation comes from the Intercostalis .

Epaxial vs Hypaxial muscles

• Epaxial muscles lie dorsal to the transverse vertebral processes.
• Hypaxial muscles are ventral (beneath).

Epaxial Muscles

• Juxta-vertebral muscles form a continuous column through most of the vertebral column.

Erector Spinae Muscles

• It is a dorsal musculature associated with the vertebral column and ribs.
• Divisions: iliocostalis, longissimus, and transversospinalis muscles.
• Action: Extensors of the vertebral column; unilateral action produce lateral movements of the trunk.

Iliocostalis m.

• A series of longitudinal fascicles lateral to the other epaxial muscles.
• It composed of a series of overlapping fascicles.
• Its a slim elongated muscle, it is divided its lumbar, thoracic and cervical portions.
• It originates from the crest of the ilium, the transverse processes of the lumbar vertebrae and the fascial sheet.
• It ends with one common tendon of insertion on the last cervical vertebra (cervical portion).
• In carnivores, well distinguished as an independent muscle, it attaches to the ends of the transverse processes of the lumbar vertebrae and inserts with fleshy serrations on the 11th to 13th ribs.
• Originates from the Sacrum/ Illiac Crest/ Spinous processes of lower lumbar/ thoracic vertebrae, and lumbar fascia.
• Inserts on the Ribs and last cervical vertebra

Action of the vertebral column or lateral movement

• Fixation of the when only one side contracts; aids in expiration with the ribs caudally pulled inward.
• Innervation in the dorsal and branches of the nn. Thoraci lumbares.

Longissimus Muscle

• Is an Erector spinae muscle that likes medial to the m. ilocostalis.
• Composes the major portion of the epaxial muscle portion.
• Extends from the Ilium to the Head.
• The divided is capital, cervical, thoracic and lumbar portions.

Long muscle of the head (m. longissimus capitis)

• Lies medial to the mm. longissimus cervicis and splenius. Covers the m. semispinalis capitis along its ventral border and extends from the first 3 thoracic vertebrae to the temporal bone.
• Originates from the transverse processes of the first thoracic and last cervical vertebrae.
• Insertion point in the wing of the atlas

Role and Innervation

• Action: Extension of the atlantooccipital joint, rotation of the atlantoaxial joint as well as fixing the movement inn bilateral action.
• Dorsal branches of the cervical nerves (nn. cervicales) carry the innervation.

###Long muscle of the neck (m. longissimus cervicis)

• Originates from a Continuation of the longissimus thoraci Insertion last cervical vertebra
• In unilateral action extends, raise the neck/turn it to a side
• Dorsal: branches of the thoracic nerves

Long muscle of the thorax (m. longissimus thoracis)

• iliac crest to the last cervical vertebra
• All thoracic ribs

Actions and Nerve

• Extension of the vertebral column
• raising the head of the boyd section from pelvis and sacrum
• The other muscles that have fixation of the vertebral collumn
• Dorsal branches of the thoracic nerve.

Long muscle of the lombar region (m. longissimus lumborum)

• Iliac crest and ventral surface of the ilium and spinous processes and supraspinous ligament.
• Ends on accessory processes of the sixth to first lumbar vertebrae.

Action/Nerve

• Dorsal extension of the vertebral column
• Raasing of the cranial portion with assistance of other muscles
• Dorsal branches of thoracic/lumbar nerve

Transversospinalis System

• The epaxial muscle mass is on the central side. Made out of different types of fiber bundles for different parts. That's joined by one fiber bundle of more.

Muscle Groups

• Splenius
• Semispinalis
• Rotator
• Interspinal
• Intertransverse

Spinalis Cervicis

• medial side of the erector spinal group attached the side.
• The spinal is the cervical part also by the muscle that has cervical vertebral spinus process.
• Has the attached of the vertebral side spinis side. A process

Origin

• extends across the spinous processes of one or more thoracic vertebrae, and sometimes last cervical vertebra. Insertion: spinous processes of 2nd to 5th cervical vertebrae

Action

• To fix thoracic vertebral column and to extended the neck

Innervation

• Dorsal branches of cervical and thoracic process

Semispinalis Capitis

• Is Large continuation to the head of the spinalis and semispinalis thoracic and cervical muscles.

Nerve/Action

• Nerve Greaters Occiptial nerve
• It has to extend the head.

The divided muscle are two parts

• Biventor cervicis muscle: the morsmedeal, divesionl of semisipinalis, capitals are going to go from the thracolumbar facia or transverse proccing
• Complemus muscle: what. they vemtolerate division, and what they've been

Multifidus:

• It's made of individual bundles that over lap.
• Are two vertebraes which pass by.
• It's used for animals with tails, used for sacral and caudis, doorsailis and medalis for tails

Multifidi

• Laterals/medials/profoundis rotate Vertebral column
• Lumbar/thoracis/cervical region

Origin

• Articular process that has multifidus that has bundles which has spinalis capitus

Multifidus thoracis:

• Distinctly isolated part of the mammary and tranverse.

- Interspinal m

• located deep, spinal muscle, they are short that extends to short animals deep to multifidi

Interspinal cervival

: the neck muscle are different humans

Intertransverse :

• Small. It passes between transvers process with mammilary process

• Dorsalis: horizontal bundles

• Med: cranivernal articular processes for bundle

• Veltralis: goes horizontal end that