4. Muscles of Axial Skeleton

remove the lamina of the vertebra to gain access to spinal cord. used for surgical repair for dorsal extrusions of intervertebral disks

dorsal laminectomy

which muscles are generally stronger? epaxial or hypaxial

epaxial

-muscles that lie dorsal to the transverse processes of the vertebrae. -function mainly as extensors of the vertebral column

epaxial group

-Decrease volume of thorax; opposite of inspiration -Ribs drawn caudally, decreasing transverse diameter and volume of thorax (Internal intercostal mm., serratus dorsalis caudalis m., abdominal muscles)

expiration

-biventer cervicis (dorsal with tendinous intersections) -complexus of the semispinalis captious of the transverse spinalis system

semispinalis capitis

often split into two parts; cranial and caudalis

serratus dorsalis

is much smaller and found on the dorsal surface of the caudal thorax, with attachments to the thoracolumbar fascia and the caudal borders of the last three (3) ribs. -Draws the last 3 ribs caudally in expiration.

serratus dorsalis caudalis

will be found on the dorsal surface of the cranial thorax, with attachments by a broad aponeurosis deep to the rhomboideus m. to the median raphe of the neck and will insert on the craniolateral surface of the ribs. -It will lift the ribs as part of inspiration

serratus dorsalis cranialis

large muscle on dorsolateral aspect of neck, deep to rhomboideus capitis -Arises from spinous processes of first 3 thoracic vertebrae, thoracolumbar fascia, and median raphe of neck and inserts on nuchal crest and mastoid region of temporal bone (skull)

splenius

what muscles are included in iliocostalis system of epaxial muscles?

1. Iliocostalis lumborum -Located in the lumbar region -Pins are across the lumbar region 2. Iliocostalis thoracis Located on the thorax Pins are across the lumbar

what muscles are included in the longissimus system of epaxial muscles?

1. Longissimus thoracis and lumborum 2. Longissimus cervicis 3. Longissimus capitis

there are ___ parallel muscle masses, or systems, affiliated with the dorsal vertebral column (epaxial muscles)

3 *backstrap muscles

identify the structures

A, Transverse section of the canine neck at the level of the fifth cervical vertebra. B, Left external jugular vein raised by thumb pressure at the base of the neck. 1, Nuchal ligament; 2, trapezius; 3, rhomboideus; 4, splenius; 5, cleidocervicalis; 6, omotransversarius; 7, cleidomastoideus; 8, sternocephalicus; 9, sternothyrohyoideus; 10, trachea; 11, esophagus; 12, external jugular vein; 13, common carotid artery, vagosympathetic trunk, and recurrent laryngeal nerve; 14, superficial cervical vessels; 15, superficial cervical lymph nodes; 16, fifth cervical vertebra; 17, vertebral vessels.

what muscles are included in the lateral group of epaxial muscles?

Iliocostalis system ilium to ribs

what muscles are included in the intermediate group of epaxial muscles?

Longissimus system ilium to head

what muscles are included in the medial group of epaxial muscles?

Transversospinalis system -Transversing the spine (sacrum to head) -sacrum to head

-multipurpose limbs -flexible trunks: allows increase stride length

biomechanics of carnivores

-trachea -esophagus -thyroid and parathyroid glands -recurrent laryngeal nerves -tracheal lymph nodes -carotid sheath: common carotid arteries, vagosympathetic trunks, internal jugular veins

cervical visceral space

there are 12 of these muscles on each right & left sides of the thoracic wall -Run caudoventrally from the caudal border of a cranial rib to the cranial border of the adjacent caudal rib -The caudal border of these muscles is near the costochondral junction -Function in respiration by drawing the ribs together

external intercostal

-muscles that lie ventral to the vertebral bodies and transverse processes. -includes the muscles of the thoracic and abdominal walls.

hypaxial group

flexors of the neck

hypaxial muscles

lie ventral to the transverse processes of the vertebrae -Will include muscles of the vertebral column and muscles of the thoracic and abdominal walls

hypaxial muscles

longus coli: -located on the ventral surfaces of the vertebral bodies (T6-C1) -extends into the thorax longus capitis: -located immediately ventral to the cervical vertebral transverse processes

hypaxial muscles

originates on wing of ilium, inserts on transverse processes of lumbar vertebrae and caudal 4-5 ribs o Fused medially with longissimus lumborum, difficult to distinguish

iliocostalis lumborum

• Attachments: ilium & transverse processes of lumbar vertebrae; inserts on cranial lumbar vertebrae and ribs with a weaker connection to the neck • Assists in bending the trunk laterally

iliocostalis system

originates on the 12th rib to the transverse process of the 7th cervical vertebra, with individual components that transverse the ribs

iliocostalis thoracis

-Increase volume of the thorax, allowing expansion of lungs -Ribs pulled cranially (External intercostal mm., rectus thoracis m., serratus dorsalis cranialis m., scalenus m)

inspiration

Longissimus system (ilium to head)

intermediate group of epaxial muscles

will be found just deep to the external intercostal mm. -Fibers run cranioventrally from caudal border of a cranial rib to the cranial border of the adjacent caudal rib -Medial to these muscles is the thoracic pleura (and therefore access to the thoracic cavity) -Function is similar to external intercostal mm.

internal intercostal

Iliocostalis system (ilium to ribs)

lateral group of epaxial muscles

distinct muscles, medial to longissimus cervicis m. and splenius m. -Originates from thoracic vertebrae 1-3 and inserts on the mastoid part of temporal bone (skull)

longissimus capitis

cranial continuation of the longissimus thoracis et lumborum system -Will be found in angle between cervical and thoracic vertebrae; insert on transverse process of caudal few cervical vertebrae

longissimus cervicis

difficult to distinguish from iliocostalis system in lumbar region -Originates from iliac crest and medial wing of ilium and supraspinous ligament and spines of lumbar and thoracic vertebrae -Inserts on various processes of lumbar and thoracic vertebrae, thoracic portion inserts on ribs and 7th cervical vertebra

longissimus thoracis et lumborum system

lies lateral to longus colli m.; extends from transverse processes of midcervical vertebrae to a process on the basioccipital bone of the skull

longus capitis

form the dorsal border of the vertical visceral space

longus coli longus capitis

spans from the cranial thoracic region to atlas, covering ventral surfaces of vertebral bodies

longus colli

Transversospinalis system -Transversing the spine (sacrum to head)

medial group of epaxial muscles

Serratus dorsalis m. -Cranialis & caudalis External intercostal mm. Internal intercostal mm. -Deep to externalcostal Scalenus m. Rectus thoracis m.

muscles of the thoracic wall

what lies between the medial surfaces of the 2 semispinalis captious muscles?

nuchal ligament

-Biventer cervicis m.: has distinct tendinous intersections; arises from thoracic vertebrae and inserts on caudal surface of the skull -Complexus m.: will be ventral to biventer cervicis m. and arises from cervical vertebrae and inserts on the nuchal crest (skull)

semipinalis capitis

Will be found deep to splenius m. Composed of two muscles

semipinalis capitis

what muscles are included in the transversospinalis system of epaxial muscles?

semispinalis capatis

the muscles of the thoracic wall are primary used for?

respiration

a group of muscles (divided into several slips that may be identified as separate dorsal, middle, and ventral parts) that will be located ventral to the cervical portion of the serratus ventralis m. -Attachments: first few ribs and transverse processes of cervical vertebrae

scalenus