Extrinsic Back Muscles Flashcards
What are the origins of trapezius?
Medial 1/3 of superior nuchal line
EOP
Ligamentum nuchae
Spinous processes of C7 - T12
How are the fibers of trapezius classified? And what are their insertion attachments?
Descending fibers (Superior) : insert on lateral 1/3 of clavicle.
Middle fibers : insert on spine and acromion process of scapula.
Ascending fibers (inferior ): base of the spine of the scapula.
What are the actions of the descending middle and inferior fibers of trapezius?
What are the bilateral and unilateral actions of trapezius?
Descending fibers: lift shoulder
Middle fibers: moves scapula towards midline. Retract scapula.
Inferior fibers: move scapula down. Depressed scapula.
Bilateral action: extend head to look back/up
Unilateral action: lateral flexion, bend head to one side
What is the innervation of trapezius ?
Motor and Sensory
Motor: Cranial nerve 11 (CNXI)
Sensory : c3 and c4 ventral Rami
Where does cranial nerve 11 run?
Exits the brain stem through the jugular foramen of the skull.
Runs deep to the sternocleidomastoid muscle.
Runs obliquely from mastoid process and forms part of subtrapezial plexus.
What is a plexus?
A network of nerves
What artery supplies blood to the superior fibers of trapezius ?
The occipital artery
Where does the occipital artery Branch from and where does it run?
Branches from the external carotid artery.
Runs in occipital groove (medial to mastoid notch)
Ascends and runs along occipital bone.
What is the first branch from the subclavian artery and where does it run?
Bonus: what is the risk here?
The vertebral artery.
Runs in the transverse foramina of the cervical vertebrae.
Potential risk of dissection during adjustment.
Where does the thyroscervical trunk Branch from? In what section?
The thyrocervical trunk branches from the first section of the subclavian artery medial to the anterior scalene muscle.
What artery branches from thyrocervical trunk?
The transverse cervical artery
What artery supplies blood to the middle fibers of trapezius?
The transverse cervical artery
What trunk branches from the subclavian artery deep to the anterior scalene muscle?
The costocervical trunk
What artery branches from the subclavian lateral to anterior scalene and median to rib 1?
Dorsal scapular artery
What artery provides blood supply to ascending (inferior) fibers of trapezius?
Dorsal scapular artery
What is the variation to the branches of the subclavian artery?
Missing dorsal scapular artery.
Transverse artery divides into superficial and deep branches
Superficial branch - trapezius
Deep Branch - rhomboids
What are the origin attachments for latissimus dorsi?
Via thoracolumbar fascia:
SPs of T7- L5
Posterior iliac crest
Via bone:
Iliac crest
Lower 3-4 ribs
What is a convergent muscle?
A muscle with a broad origin and narrow insertion.
Convergent muscles have very powerful action.
What is the insertion attachment for latissimus dorsi?
Floor of bicipital (intertubercular) groove
What are the actions of latissimus dorsi?
Hyperextension of the arm: Back toward midline of body, behind body (sagittal plane)
Medial rotation: best seen with arm flexed at elbow. (Multiplane)
Adduction of arm: (coronal plane)
What is the innervation of latissimus dorsi?
The thoracodorsal nerve
Where does the thoracodorsal nerve run?
Ventral Rami of C8- C8
Branches from posterior cord of brachial plexus in axial area
Runs along the back of the thorax
Travels down the deep surface of latissimus dorsi.
What artery provides blood supply for latissimus dorsi?
The thoracodorsal artery
Where does the thoraco dorsal artery come from?
Axillary artery (just lateral to rib 1)> subscapular artery > thoracodorsal artery
What runs along with the thoracodorsal artery?
The thoracodorsal nerve.
Both run along the deep surface of latissimus dorsi.
What is the origin of levator scapula?
TPs of C1 - C4
What is the insertion of levator scapulae?
Medial border of the scapula from root of the spine to the superior angle.
What are the actions of levator scapulae?
When contracted levator scapula elevates the superior angle of the scapula which rotates the lateral side, or glenoid fossa inferiorly.
When talking about shoulder rotation movements, we always speak in terms of the glenoid fossa.
What are the motor and sensory innervations of levator scapulae?
Motor: ventral Rami of c3 and c4
Sensory: dorsal scapular nerve
What is the blood supply for levator scapulae?
The dorsal scapular artery.
In the variant where the dorsal scapular artery is missing, what is the blood supply for levator scapulae?
The deep branch of the transverse cervical artery.
What is the insertion for rhomboid minor?
The media border of the scapula at the base of the spine of the scapula (root of the spine)
What is the origin of rhomboid minor?
The lower portion of ligamentum nuchae
SPs of C7-T1
What are the actions of rhomboid major and minor?
Retract the scapula (adduction)
Inferiorly rotates the glenoid fossa
(By superiorly rotating the medial side of the scapula)
What is the innervation of rhomboid major and minor?
The dorsal scapular nerve
C4/c5 ventral Rami
What is the blood supply of the rhomboids major and minor?
The dorsal scapular artery
(Runs deep to levator and down medial surface of scapula)
In people with the variant that causes a missing dorsal scapular artery, what is the blood supply of the rhomboid major and minor muscles?
The deep branch of the transverse cervical artery
What is the origin of rhomboid major?
Spinous processes of T2 -T5
What is the insertion of rhomboid major?
The medial border of the scapula from inferior angle to root of spine.
What is the origin of serratus anterior?
Ribs 1-8
What is the insertion of serratus anterior?
Interior surface of the medial border of the scapula
What is the action of serratus anterior?
Protraction of the scapula (rolling the shoulder forward)
Elevation and upward rotation of scapula (when you’re lifting your arm over your head)
Boxing muscles: allow you to throw a punch.
What is the origin of serratus posterior superior?
Ligamentum nuchae
SPs C7-T2
What is the insertion of serratus posterior Superior?
Ribs 2 through 5
lateral to the angle of the rib
What is the innervation of serratus posterior Superior?
Ventral Rami of intercostal nerves 1-4
What is the blood supply of serratus posterior superior?
Highest intercostal artery
(Arises from costocervical trunk, at second section of subclavian artery deep to the scalene muscle)
Posterior intercostal arteries
(Branch from descending aorta)
Where does the highest intercostal artery branch from?
Costocervical trunk
(2nd section of subclavian artery)
What structures is serratus posterior superior immediately deep to?
The rhomboids and scapula
What is the origin attachment of serratus posterior inferior?
SPs T11 - L2
what is the insertion of serratus posterior inferior?
Lower four ribs lateral to angles
What is the action of serratus posterior inferior?
Depresses lower ribs
(During forced inspiration)
What is the innervation of serratus posterior inferior
Ventral Rami T9 through T12
(Intercostal nerves T9- T12)
What spinal levels does the dorsal scapular nerve emerge from?
C4 & C5
What is the sensory innervation of trapezius?
C3 and C4 ventral Rami
What does the highest intercostal artery supply blood to?
Where does it Branch from?
Serratus posterior Superior
Branches from subclavian>costocervical trunk>highest intercostal
