Session 16: posterior muscles

Question 1

Origin and insertion of the deltoid muscle

Answer 1

Originates from the inferior aspect of the spine of the scapula
Inserts into the mid shaft of the humerus

Question 2

Origin and insertion of the trapezius muscle

Answer 2

Arises from the occiput on the back of the skull and the spinous processes of the cervical and thoracic vertebra

Question 3

Innervation of the trapezius muscle

Answer 3

The spinal accessory nerve (C11).

Question 4

Innervation of the sternocleidomastoid muscle

Answer 4

The spinal accessory nerve (C11)

Question 5

Origin and insertion of the latissimusdorsi muscle (on dorsum of the thorax)

Answer 5

Arises from the thoracolumbar fascia

Inserts onto the humerus

Question 6

The shape and borders of the scapula

Answer 6

• Has a triangular shape

- Has three borders: medial/inferolateral/superior border

Question 7

Scapula creates a fossa above + below the spine for which two muscles?

Answer 7

The supraspinatus and infraspinatus muscles

Question 8

From the inferolateral border of the scapula, which two muscles arise?

Answer 8

1. ) Teres major: inserts into the humerus

2. ) Teres minor: inserts onto the inferior aspect of the greater tuberosity

Question 9

What passes through the quadralateral space?

Answer 9

The axillary nerve and the posterior circumflex humeral blood vessels (to enter the posterior aspect of deltoid)

Question 10

What would happen if you fractured the surgical neck of your humerus or if you dislocated your shoulder?

Answer 10

Would lose the sole motor to deltoid

Question 11

Trapezius muscle fibre directions

Answer 11

1. ) Mid portion: has horizonal fibres. When contracting they will pull the shoulder blade backwards towards the spine (retraction of the scapula)
2. ) Lower + upper portions: if they contracted simultaneously they would rotate the scapula

Question 12

For every 2 degrees of abduction at the shoulder joint there is…

Answer 12

… one degree of rotation of the scapula on the thoracic wall

Question 13

What 3 muscles are attached to the medial border of the scapula

Answer 13

Rhomboid major/rhomboid minor/levator scapulae

Question 14

Where does the lattisimus dorsi originate from

Answer 14

Arises from the thoraco-lumbar aponeurosis and the aponeurotic sheet. It runs upwards and outwards.

Question 15

Where does the lattisimus dorsi insert onto?

Answer 15

The proximal humerus

Question 16

Main action of the lattismus dorsi

Answer 16

To pull your arm downards when ringing a church bell etc

Question 17

Nerve supply of the lattismus dorsi

Answer 17

The thoracodorsal nerve

Question 18

Where does the thoracodorsal nerve arise from?

Answer 18

Arises from the posterior cord of the brachial plexus. Runs through posterior aspect of the axilla

Question 19

What’s at risk with malignant disease of the axilla/surgery on the axilla or may be damaged with radiotherapy to the axilla

Answer 19

The thoracodorsal nerve

Question 20

If you reflect the lattismus dorsi muscle what could you see?

Answer 20

The erecti spinae muscle/individual ribs and intercostal muscle

Question 21

What other muscle arises from the medial border of the scapula?

Answer 21

Serratus anterior. Runs deep to the scapula + round to the front of thorax where it attaches to individual ribs

Question 22

Function of serratus anterior

Answer 22

Contracts: will pull the medial

border of the scapula laterally (protraction of the scapula)

Question 23

What happens when the trapezius and rhomboids combined contract?

Answer 23

Will pull the scapula posteriorly (retraction of the scapula). They are antagonists to serratus anterior

Question 24

What nerve supplies the serratus anterior?

Answer 24

The long thoracic nerve

Question 25

Origin of the long thoracic nerve

Answer 25

It arises from the roots of the brachial plexus (C5/6/7)

Question 26

Where does the long thoracic nerve pass through?

Answer 26

The axilla. Can be damaged by disease within axilla/surgery/radiotherapy

Question 27

Consequence of damage to the long thoracic nerve

Answer 27

Paralysis of the serratus anterior. Get winging of the scapula

Question 28

What are the three origins of the triceps muscle

Answer 28

Originates from the inferior part of the glenoid cavity and the humerus

Question 29

What is the single insertion of the triceps muscle

Answer 29

The olecranon of the ulna

Question 30

What nerve lies posteriorly to the medial epicondyle of the humerus (the ‘funny’ bone)

Answer 30

The ulna nerve