Lesson 6 Ecorche: Shoulder and Upper Back

-Rhomboideus Minor and Major

-Teres Minor

-Infraspinatus

-Teres Major

-Latissimus dorsi

-Thoracolumbar fascia

-Trapezius

-Pectoralis Major

-Deltoideus


Attachments on the humerus

These diagrams from Gray's Anatomy are the same as those from Lesson 5.

Posterior view: Note the attachments of the Teres Minor and infraspinatus muscles up near the head of the humerus.

Anterior view: Note the attachments of the Teres Major and Latissimus dorsi muscles on the anterior surface.  This might seem surprising since these muscles have their origins on the dorsal surface of the scapula and back.  Both wrap under the arm, and insert between the coracobrachialis and triceps group.

Their insertions are covered partly by the pectoralis major and the deltoideus group.


Attachments on the Scapula

In these diagrams, again from Gray's Anatomy, we see the multitude of muscles that attach onto the scapula.

 


Rhomboideus Minor and Major

-Action is the retraction (pulling back) of the shoulder blades

-Note the angle sloping downwards from its origin points towards its insertion on the scapula - this creates a characteristic plane break that continues the plane breaks of the spines/acromion process of the scapula, creating a plane break roughly in a w shape across the top of the shoulders (see the section on the "Major Plane Breaks of the Shoulders" below the Trapezius).

 

Origin        

The seventh cervical vertebrae to the 5th thoracic vertebrae (C1 - T5)    

 

Insertion

Medial border (inside edge) of scapula)    

 

Colour on your model

Orange


Teres Minor

-The Teres minor is located inferiorly to the Infraspinatus, the bulk of this muscle is towards the humerus since it attaches to the lateral border of the scapula

 

Origin:

Lateral edge of the Scapula

 

Insertion:

Posterior surface of the head of the humerus    (above the Triceps.

 

Colour on your model:

Yellow


Infraspinatus

The most important thing about the Infraspinatus for our purposes here, is that it fills the bulk of the shoulder blade below the scapula spine

 

Origin:

Flat middle region of the scapula below the spine/acromion process    

 

Insertion:

posterior surface of the head of the humerus    

 

Colour on your model:

Orange


Teres Major

-Follows the path of the large latissimus dorsi in the sense that it inserts into inner arm between the triceps and biceps

-It crosses the Latissimusdorsi, inerting onto the the humerus further along (distally)

-It contributes to the noticeable form projecting out from the Latissimus dorsi. This form is also made up of the Scapula and other shoulder muscles.

 

Origin:

posterior surface of the interior angle (bottom tip) of the scapula    

 

Insertion:

Beside the latissimus dorsi on the anterior surface of the humerus, but it is medial, and distal to the latissimus dorsi    

 

Colour on your model:

Red


Latissimus Dorsi    

-Extremely broad, flat muscle stretched from roughly the medial edge of the bulge of the Multifidus around to the middle of the side of the ribcage    

-It fans out from a relatively small attachment on the front of the humerus, medial to the insertion of the Pectoralis Major. This insertion is also closer to the head of the humerus than the pectoral  

-Like the Pectoralis Major, its fibres spread out from the insertion tendon to a broad area of origin.  

-Also like the Pectoralis Major there is a twist in the muscle fibres when the arm is lowered, with the uppermost fibres inserting lower down the humerus than those orginating down near the pelvis

 

Origin:

T7-L5, Inferior 3 or 4 ribs, inferior angle of the scapula, the thoraco-lumbar fascia, the iliac crest posterior to the insertion of the external Oblique    

 

Insertion:

Lateral humerus.  Relative to the Pectoralis Major and the Teres Major, it is closest to the superior head of the humerus, and is located in between them    

 

Colour on your model:

Purple


Thoracolumbar Fascia

This is a complex, multilayered set of sheets of connective tissue, as the diagrams at right from Gray's Anatomy give some indication of.  For the artist of course, it is mostly of interest where it shapes surface anatomy.  It serves as attachment for the broad latissimus dorsi muscles which means that the muscle body of the latissimus begins to the side of the diamond shaped thoracolumbar fascia, contributing to the volume running down and outwards on either side of what we have called "the lumbar spine columns".

 

 


Trapezius    

-The medial border of the trapezius, where it attaches to the clavicle, is approximately in line with the medial border of the anterior head of the deltoid    

-The medial region of the trapezius muscle fibres can be thought of as fanning out from the medial end of the spine of the scapula

-Notice the plane breaks of the shoulders dividing the muscle up

-Also notice the diamond shape of tendinous tissue around the 7th Cervical spine (C7)

Origin:

Middle of the base of skull, C1-C6 spines(roughly speaking), C7-T12 spines    

 

Insertion:

posterior border of the lateral third of the clavicle, acromion process, and spine of scapula    

 

Colour on your model:

Green

 

Simplified planes of the Trapezius

More developed forms of the Trapezius


Major plane breaks of the shoulders

 

 

 


Pectoralis Major “Pectoral”    

-Fan shaped muscle    

-The top fibres (those originating on or nearer the clavicle) insert into the humerus distally to the bottom fibres(ie further down the arm), giving the Pectoralis Major a characteristic twist that results in the fold at the arm pit when the arm is lowered

-Three major parts: the clavicular portion, portion attaching to sternum and manubrium, ribs 1-6

- Note the way the lower borders of the pectoralis major seems to flow into sides of the rectus abdominis

 

Origin:

-Anterior surface of the medial (inner) half of the clavicle; anterior surface of sternum; top six rib cartilages, connective tissue laying over the abdominals (aponeurosis of the external oblique)    

 

Insertion:

Anterior surface of the humerus, outside the biceps, distal and lateral to the insertion of the Latissimus Dorsi (further from the shoulder and further towards the outside)     

 

Colour on your model:

Orange


Deltoid    

-Divided into three sections, all of which insert onto a tuberosity (protrusion) midway down the lateral face of the humerus    

-The deltoid can be thought of as a tear-drop shaped shoulder pad wrapping around the shoulder joint, covering sections of many of the muscles that pass across or are near this joint.

-That is why it is the very last muscle to be added to the shoulder region in this course

-As mentioned earlier, the medial border of the anterior fibres of the deltoid lines up with the medial border of the trapezius

 

Origin:

Anterior fibres: lateral third of the clavicle, 

lateral fibres: lateral face of the acromion process, 

Posterior fibres: inferior face of the spine of the scapula

 

Insertion:

Deltoid tuberosity of the humerus (lateral face of humerus, about half way down the bone.    

 

Colour on your model:

Purple


Examples of back anatomy:

Cropped torso from one of my digital sculptures:


All the models of figures below are available for free on Sketchfab.com, and I have collected various scans of figures into a collection in my account:

https://sketchfab.com/scottbreton/collections/scans-of-figures

Where there are textures applied (texture is a technical term for a coloured skin added to the model), you can see just the form itself by:

1. load the model

2. click on the little cube at the bottom right (it has a small blue circle with HD or LD in it)

3. click on "matcap" 

it will transform into the shiny metal looking version as at right above:

The scan itself:


Scan from Ten24 - 3Dscanstore.com: 

(Done with photogammetry - multiple photographs compiled into a model with software).


Scan by CIMtech Inc. done with an Artec scanner:

 


Scan by FredLucazeau (Photogammetry)

 


Scan of a body builder by LOFT22