Session 16: posterior muscles Flashcards
Origin and insertion of the deltoid muscle
Originates from the inferior aspect of the spine of the scapula
Inserts into the mid shaft of the humerus
Origin and insertion of the trapezius muscle
Arises from the occiput on the back of the skull and the spinous processes of the cervical and thoracic vertebra
Innervation of the trapezius muscle
The spinal accessory nerve (C11).
Innervation of the sternocleidomastoid muscle
The spinal accessory nerve (C11)
Origin and insertion of the latissimusdorsi muscle (on dorsum of the thorax)
Arises from the thoracolumbar fascia
Inserts onto the humerus
The shape and borders of the scapula
- Has a triangular shape
- Has three borders: medial/inferolateral/superior border
Scapula creates a fossa above + below the spine for which two muscles?
The supraspinatus and infraspinatus muscles
From the inferolateral border of the scapula, which two muscles arise?
- ) Teres major: inserts into the humerus
2. ) Teres minor: inserts onto the inferior aspect of the greater tuberosity
What passes through the quadralateral space?
The axillary nerve and the posterior circumflex humeral blood vessels (to enter the posterior aspect of deltoid)
What would happen if you fractured the surgical neck of your humerus or if you dislocated your shoulder?
Would lose the sole motor to deltoid
Trapezius muscle fibre directions
- ) Mid portion: has horizonal fibres. When contracting they will pull the shoulder blade backwards towards the spine (retraction of the scapula)
- ) Lower + upper portions: if they contracted simultaneously they would rotate the scapula
For every 2 degrees of abduction at the shoulder joint there is…
… one degree of rotation of the scapula on the thoracic wall
What 3 muscles are attached to the medial border of the scapula
Rhomboid major/rhomboid minor/levator scapulae
Where does the lattisimus dorsi originate from
Arises from the thoraco-lumbar aponeurosis and the aponeurotic sheet. It runs upwards and outwards.
Where does the lattisimus dorsi insert onto?
The proximal humerus
Main action of the lattismus dorsi
To pull your arm downards when ringing a church bell etc
Nerve supply of the lattismus dorsi
The thoracodorsal nerve
Where does the thoracodorsal nerve arise from?
Arises from the posterior cord of the brachial plexus. Runs through posterior aspect of the axilla
What’s at risk with malignant disease of the axilla/surgery on the axilla or may be damaged with radiotherapy to the axilla
The thoracodorsal nerve
If you reflect the lattismus dorsi muscle what could you see?
The erecti spinae muscle/individual ribs and intercostal muscle
What other muscle arises from the medial border of the scapula?
Serratus anterior. Runs deep to the scapula + round to the front of thorax where it attaches to individual ribs
Function of serratus anterior
Contracts: will pull the medial
border of the scapula laterally (protraction of the scapula)
What happens when the trapezius and rhomboids combined contract?
Will pull the scapula posteriorly (retraction of the scapula). They are antagonists to serratus anterior
What nerve supplies the serratus anterior?
The long thoracic nerve
Origin of the long thoracic nerve
It arises from the roots of the brachial plexus (C5/6/7)
Where does the long thoracic nerve pass through?
The axilla. Can be damaged by disease within axilla/surgery/radiotherapy
Consequence of damage to the long thoracic nerve
Paralysis of the serratus anterior. Get winging of the scapula
What are the three origins of the triceps muscle
Originates from the inferior part of the glenoid cavity and the humerus
What is the single insertion of the triceps muscle
The olecranon of the ulna
What nerve lies posteriorly to the medial epicondyle of the humerus (the ‘funny’ bone)
The ulna nerve
