Anatomy Week 1 - Vertebrae and Back Muscles

Thoracic Vertebrae

• 12

• small(est) vertebral foramen/canal

• transverse processes articulate with ribs

• long spinous processes which slope downwards

Cervical Vertebrae

• 7

• small body

• prominent transverse processes which contain vertebral artery and vein + sympathetic nerves

• muscle and ligament attachments at spinous process including nuchal ligament

Lumbar Vertebrae

• 5

• thick, large bodies

• triangular vertebral foramen/canal. smaller than cervical but larger than thoracic

• muscle and ligament attachments at transverse and spinous processes

Typical Vertebrae

• body

• seven processes: 1 spinous, 2 transverse, 4 articular

  • transverse for muscle/ligament attachments

  • articular connect with superior and inferior vertebrae. they articulate :D

(Inter)Verterbral Discs

• Fibrocartilage cushion that functions as the joint between two vertebrae

• Components:

  • inner, spongy nucleus pulposus - essential for providing flexibility, shock absorption

  • surrounding annulus fibrosus - tough, fibrous structure, keeps NP in place

Ligaments of the Spine

Includes 5 of note:

• Anterior longitudinal ligament

• Posterior longitudinal ligament

• Interspinal/-spinous ligament

• Supraspinal/-spinous ligament

• Ligamenta Flava

Atlas - C1

• no body or spinous process

• articulates with the skull. this articulation allows for flexion/extension of the head with the neck (nodding)

• also responsible for rotation of the skull from side-to-side

Axis - C2

• provides a pivot point for atlas to rotate from side-to-side at the odontoid process/dens

Intrinsic Back Muscles

• all innervated by dorsal rami of spinal nerves

• deeper muscles, “true” back muscles

• involved in movements of the vertebral column. help with posture and stability

Extrinsic Back Muscles

• superficial muscles

• connect spinal column to shoulders/upper limbs — involved in their movements + movement of the scapula

• mostly innervated by the ventral rami of spinal nerves

Superficial Extrinsic Back Muscles

• Trapezius

• Latissimus dorsi

• Levator scapulae

• Rhomboid minor

• Rhomboid major

Intermediate Extrinsic Back Muscles

• Serratus posterior superior

• Serratus posterior inferior

  • both insert on ribs and assist with forced inspiration

Superficial Intrinsic Back Muscles

• splenius cervicis

• splenius capitis

  • these muscles laterally flex / rotate the head to their respective sides when acting alone. they work together to extend the head and neck

Intermediate Intrinsic Back Muscles

Erector Spinae Group:

• Iliocostalis

• Longissimus

• Spinalis

• these muscles are important in maintaining posture, vertebral extension, and lateral flexion

Deep Intrinsic Back Muscles

Transversospinalis Group:

• Semispinalis (most superficial)

• Rotatores

• Multifidus

  • do not attach to the thoracolumbar aponeurosis

  • function in extension, rotation, lateral bending, and stabilize the vertebral column

  • these muscles generally run from transverse processes inferiorly to spinous processes superiorly

Trapezius

• innervation: spinal accessory nerve (CN XI)

• vasculature: transverse cervical artery

• Divisions

  • Upper: elevates shoulder, upward/superior rotation of scapula

  • Middle: retracts scapula

  • Lower: depresses scapula

Latissimus Dorsi

• innervation: thoracodorsal nerve

• vasculature: thoracodorsal artery

Levator Scapulae

• originates on transverse processes C1-C4

• innervation: dorsal scapular and cervical nerves

• vasculature: dorsal scapular artery

• also functions in inferior/downward rotation of scapula

Rhomboid Minor

• Origin: Nuchal ligament and spinous processes of C7 and T1

• innervation: dorsal scapular nerve

• vasculature: dorsal scapular artery

• retraction + downward rotation

Rhomboid Major

• Origin: Spinous processes of T2-T5

• innervation: dorsal scapular nerve

• vasculature: dorsal scapular artery

• rhomboids stretch from medial border @ spine to the inferior angle

Serratus Posterior Superior

• Origin: Spinous process and supraspinous ligaments C7-T2

• Insertion: Posterior aspect of ribs 2-5

• Innervation: ventral primary rami T2-T5

• Vasculature: intersegmental artery

Serratus Posterior Inferior

• Origin: Spinous process and supraspinous ligaments T11-T12

• Insertion: Posterior aspect of ribs 9-12

• Innervation: ventral primary rami T9-T12

• Vasculature: intersegmental artery

Erector Spinae Group NV

• Innervation: Dorsal rami of spinal nerves

• Vasculature: Dorsal branch of segmental artery

• Insertions:

  • Iliocostalis (lumborum, thoracis and cervicis) - fibers run superiorly to angles of lower ribs, and to transverse processes of cervical vertebrae near top

  • Longissimus (thoracis, cervicis, capitis) - fibers run superiorly to ribs, angles towards thoracic/cervical transverse processes, and to mastoid process

  • Spinalis - (thoracis, cervicis, capitis) fibers run superiorly to spinous processes in upper thoracic region, and to cranium

Triangle of Auscultation

A small, triangular area on the back where breathing sounds can be heard most clearly. It is bounded by the following structures:

• Laterally: Medial border of the scapula

• Inferomedially: Lateral border of the latissimus dorsi muscle

• Superomedially: Inferior border of the trapezius muscle

Fascia Functions

Structural Support: Fascia provides a supportive and flexible framework for muscles, helping to maintain their shape and alignment.

Force Transmission: When muscles contract, the fascia helps transmit the force generated to the tendons and bones, aiding in movement.

Separation and Protection: Fascia separates different muscles and muscle groups, preventing friction between them during movement. It also protects muscles and other structures from injury.

Pathway for Nerves and Blood Vessels: Fascia contains channels for nerves and blood vessels, ensuring they can reach muscles and other tissues.

Facilitating Movement: The fascia allows muscles to glide smoothly over each other, reducing resistance and enhancing movement efficiency.

Role in Sensation and Proprioception: Fascia contains sensory receptors that contribute to the body's ability to sense position, movement, and pain.

Thoracolumbar fascia

• covers deep muscles of the back + has 3 layers

• aka thoracolumbar aponeurosis

• aka lumbodorsal fascia

Splenius Muscles NV

• innervation: dorsal rami of spinal nerves

• vasculature: occipital artery

• Capitis — inserts on mastoid process & lateral occipital bone

• Cervicis — inserts on transverse processes of cervical vertebrae

Transversospinalis Group NV

• innervation: dorsal rami of spinal nerves

• Semispinalis — inserts on occipital bone, spinous process in cervical/thoracic region going 4-6 segments superiorly

  • semispinalis capitis receives blood from occipital artery

• Multifidus — thickest in lumbar region, spans all spinous processes and inserts 2-4 segments superiorly

• Rotatores — inserts on junction of lamina/transverse process or spinous processes. Inserts either 1 (brevis) or 2 (longus) segments superiorly

Blood Supply to the Transversospinalis Muscles

• Posterior Intercostal Arteries

• Lumbar Arteries

• Deep Cervical Artery

• Vertebral Artery

• Occipital Artery