Posterior triangle

Question 1

Describe the boundaries of the posterior triangle?

Answer 1

bounded by the posterior border of SCM, middle 3rd clavicle and anterior border of trapezius

Question 2

What structures are located within the posterior triangle?

Answer 2

Contents of the posterior triangle:
- spinal accessory nerve
- subclavian artery and vein
- brachial plexus
- omohyoid (inferior belly)

Question 3

Which 3 structures cross the SCM?

Answer 3

structures crossing SCM:
- EJV
- greater auricular nerve
- transverse cervical nerve

Question 4

What does the spinal accessory nerve supply and describe its course

Answer 4

CN IX supplies motor control to SCM and trapezius
CN IX exits the skull along with CN IX and X and descends along ICA to the SCM

Question 5

What is the brachial plexus?

Answer 5

A plexus of nerves formed of anterior rammi C5-8 and T1, supplies the upper limbs

Question 6

Describe the origin and insertion of SCM

Answer 6

SCM:
origin- manubrium of sternum and superior surface of medial 3rd of clavicle
insertion- lateral surface of mastoid process and lateral half of superior nuchal line

Question 7

what is the function and innervation of SCM

Answer 7

SCM draws the head forward/ lifts chin and tilts head towards ipsilateral side, while turning face contralaterally
innervated by spinal accessory nerve (CN XI)

Question 8

describe the origin and insertion of trapezius

Answer 8

Trapezius:
origin- Superior nuchal line, external occipital protuberance, ligamentum nuchae and spinous processes (C7-T12)
insertion- lateral 3rd of clavicle, acromion, spine of scapula

Question 9

what is the function and innervation of trapzius?

Answer 9

function of trapezius is to rotate scapula during abduction of humerus, upper fibres elevate, middle fibres fibres adduct and lower fibres depress scapula
innervated by spinal accesory nerve (CN XI)

Question 10

what is the cervical plexus?

Answer 10

Cervical plexus= a cluster of nerves formed by anterior rami C1-C5 which gives of deep motor branches and superficial sensory branches
sensory- Lets Go To Sleep (lesser occipital nerve, great auricular nerve, transverse cervical nerve, supraclavicular nerve)
motor- MAP (muscular branches to SCM, ansa cervicalis, phrenic nerve)

Question 11

What is Ansa cervicalis and what structures does it supply?

Answer 11

secondary loop of cervical plexus which loops around the carotid sheath
supplies all infrahyoid muscles except thyrohyoid

Question 12

what nerve supplies thyrohyoid?

Answer 12

thyrohyoid is supplied by anterior rami C1 (but fibres run with CN XII)

Question 13

Where is the brachial plexus located?

Answer 13

brachial plexus lies deep to SCM and anterolateral to levator scapulae

Question 14

which muscles are found in the posterior triangle?

Answer 14

SCM
Trapezius
Levator Scapulae
Anterior and Middle scalene

Question 15

Which structure runs between middle and anterior scalene?

Answer 15

Subclavian artery runs between anterior and middle scalene

Question 16

What is the function of anterior scalene?

Answer 16

to flex the head

Question 17

describe the origin, insertion and function of levator scapula?

Answer 17

origin- posterior tubercle of transverse process of C1-4
insertion- superior part of medial border of scapula

function- lift the scapula

Question 18

what is the function of middle scalene?

Answer 18

function of middle scalene is to flex head laterally, lifts 1st rib