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Transcript

Upper Limb 1 The Pectoral Girdle and Shoudler Joint

Companion workbook and SDL

This Workbook contains core information and also contains questions for you to answer, diagrams to label and tables to complete. The purpose of this Workbook is to provide you with a written resource that:

  • Contains basic core information that you need to know
  • Should help you reinforce what you have learned about in the corresponding lecture and / or practical session.
In this guide through the anatomy of the pectoral girdle and shoulder, we will cover: 1. The structure & function of the pectoral girdle 2. The osteology of the pectoral girdle 3. The movements and muscles of the pectoral girdle 4. The shoulder (glenohumeral) joint

Digital Workbook and SDL

Learning Objectives

After completing this worksheet and attending teaching you should be able to:

  1. Identify the major bony landmarks on the clavicle, scapula and proximal humerus
  2. Describe the movements and muscles of the pectoral girdle
  3. Describe the shoulder joint, its movements and the structures which stabilise it
  4. Describe the rotator cuff and explain its contribution to shoulder joint stability.
  5. Describe the origins, insertions, actions and innervations of muscles that have been specifically documented in the worksheet, asked for in the worksheet or found in your lecture material
  6. Recognise bony landmarks and the attachment sites of the tendons and ligaments that have been specifically documented in the worksheet, asked for in the worksheet or found in your lecture material.

Wrong! The sternum is part of the axial skeleton.

Correct the scapula is part of the pectoral girdle.

Wrong! The head of the humerus articulates with the pectoral girdle to form the shoulder joint.

Correct the clavicle is part of the pectoral girdle

Wrong! The shaft of the humerus forms the arm.

Correct! This is the sternoclavicular joint.

Wrong this is the acromioclavicular joint

Wrong this is the glenohumeral (shoulder) joint

Axial vs Appendicular Skeleton

  • The pectoral (shoulder) girdle is part of the appendicular skeleton.
  • The articulation between the clavicle and the sternum (sternoclavicular joint) is the only joint attaching the upper limb to the trunk (axial skeleton).
  • This allows the upper limb to be highly mobile.

  • The clavicle is palpable throughout its length.
  • The lateral one third is concave, but the medial two thirds are convex.
  • The ends of the clavicle can be felt projecting to the acromion of the scapula laterally (forming the acromioclavicular joint) and the manubrium of the sternum medially (forming the sternoclavicular joint).
Use complete anatomy to investigate the clavicle further

The Clavicle

Case courtesy of Mohammad Osama Hussein Yonso, Radiopaedia.org, rID: 96861

Fracture of the clavicle

Well done, you spotted the fracture!

The Scapula

  • The scapula is a flat triangular bone, which lies on the back of the rib cage between the second and seventh ribs.
  • It articulates with the humerus at the glenoid fossa to form the shoulder (glenohumeral) joint.
  • The dorsal (posterior) surface of the scapula is divided into supraspinous and infraspinous fossae by the spine of the scapula.
  • The posterior surface of the spine widens laterally to become continuous with the flattened acromion.
  • The scapula is usually easily seen in slim people. The medial and lateral borders, inferior angle, spine and acromion can be palpated.

Posterior

Scapula: Key bony landmarks

Can you find these key bony landmarks:

  • Acromion
  • Spine
  • Coracoid process
  • Glenoid fossa
  • Supraglenoid tubercle
  • Infraglenoid tubercle
  • Supraspinous fossa
  • Infraspinous fossa
  • Subscapular fossa
  • Medial border
  • Lateral border
  • Superior border
  • Inferior angle
  • Superior angle
Click on the image to reveal the correct bony landmark (click again to hide)

Spine

Acromion

Acromion

Acromion

Spine

Glenoid fossa

Coracoid process

Supraglenoid tubercle

Infraglenoid tubercle

Infraglenoid tubercle

Coracoid process

Glenoid fossa

Supraspinous fossa

Infraspinous fossa

Subscapular fossa

Medial border

Lateral border

Lateral border

Medial border

Lateral border

Inferior angle

Inferior angle

Inferior angle

Superior angle

Superior angle

Posterior

Anterior

Lateral

Acromioclavicular Joint

Extremely strong ligaments hold the scapula and clavicle together. You do not need to know the names of the individual ligaments. If these ligaments tear, the clavicle and the scapula separate from each other (hover over image to reveal AC dislocation)

The clavicle and scapula are arranged together as shown below:

Surgical neck

Anatomical neck

Deltoid tuberosity

Greater tuberosity

Lesser tuberosity

Head

Proximal Humerus

Can you find:Head of the humerusGreater tuberosityLesser tuberosityBiciptal groove (intertubercular sulcus)Deltoid tuberosityClick on the image for the answersBoth the surgical neck and the shaft of the humerus are common sites for fracturesNow investigate the proximal humerus in Complete Anatomy

Bicipital groove

Shaft of the humerus

  • Although not a true joint, the sternoclavicular and the acromioclavicular joints, in combination with the fascial space between the scapula and underlying chest wall, are known collectively as the ‘scapulothoracic joint’.
  • They allow the scapula to glide across the thoracic wall.
  • The glenoid fossa (cavity) of the scapula articulates with the head of the humerus at the shoulder joint, so a movement of the scapula will also move the shoulder joint and humerus.

Movements of the scapula (1)

The scapula can move:

  • up and down (elevation and depression)
  • forwards (protraction = reaching the arm out in front, as if to push open a door, or throw a punch)
  • backwards (retraction = ‘squaring’ the shoulders) over the chest wall.

Movements of the scapula (2)

Movements of the scapula (3)

  • Additionally, the scapula can rotate so that the inferior angle can be moved laterally and upwards from the anatomical position (red arrow).
  • This movement brings the face of the glenoid cavity upwards and thus allows the arm to be lifted above the head.

Retractors and protractors

Elevators and depressors

Rotators

Serratus anterior

Serratus anterior

Pectoralis minor

TrapeziusRhomboid minorRhomboid majorLevator scapulaeSerratus Anterior

Trapezius

Levator scapulae

Rhomboid major

Rhomboid minor

Serratus anterior

Can you find these muscles?

Click on the image for the answers

Trapezius

Trapezius is a large muscle with several bony attachments.What are its attachemnts? Use the mouse to hover over the image to see if you are rightWhen you look at the diagram, you can see that in different parts of trapezius the muscle fibres are orientated in different directions.

  • Upper fibres elevate the scapula and assist in upward rotation.
  • Middle fibres retract the scapula.
  • Lower fibres depress the scapula

The origin of trapezius is the posterior skull and the cervical and thoracic vertebae

The insertion of trapezius is the spine of the scapula, the acromion and the lateral 1/3 of the clavicle

1. Superior fibres

2. Middle fibres

3. Inferior fibres

There are three deep dorsal muscles of the pectoral girdle which all arise from the medial border of the scapula, deep to trapezius. These are: • Levator scapulae • Rhomboid major • Rhomboid minor

Deep dorsal muscles of the scapula

The Rhomboids

What are the attachments of the rhomboid major and minor?Click on the image to see if you are right?

Both muscles arise from the cervical or thoracic vertebrae in the midline

Rhomobid minor inserts into the medial border of the scapula above the spine

Rhomobid major inserts into the medial border of the scapula below the spine

Levator scapulae

Click on the image to find the attachments of levator scapulae

Inserts in the upper medial border of the scapula

Arises from the upper cervical vertebrae

Answer

There are 2 muscles on the ventral (front) aspect of the pectoral girdle which are involved in movement of the scapula. The muscles we are interested in are: • Serratus anterior • Pectoralis minor Can you identify them on this image?

Ventral muscles of the scapula

Serratus anterior

Pectoralis minor

Serratus Anterior

  • The serratus anterior originates ribs 1 to 9.
  • The muscle forms a flattened sheet, which passes posteriorly around the thoracic wall to insert medial border of the scapula.
  • Serratus anterior pulls the scapula forward over the thoracic wall (protraction) and contributes to upwards rotation .
  • It also keeps the costal surface of the scapula closely opposed to the thoracic wall.
  • It is innervated by the long thoracic nerve, which passes through the axilla (armpit)

Functions of serratus anterior

Clinical Case 1

A patient undergoes an axillary node clearance during treatment for breast cancer. During a follow-up examination the patient is asked to push against a wall.What abnormality is seen?Can you explain why this abnormality has occured?

Answer

Clinical Case 1

Answer

This abnormality is known as winging of the scapula.Winging of the scapula occurs after axillary lymph node clearance because the procedure can damage the long thoracic nerve as it passes through the axilla (armpit).The long thoracic nerve innervates the serratus anterior muscle. This muscle plays a crucial role in holding the scapula flat against the rib cage. When the long thoracic nerve is injured, the serratus anterior becomes weak, causing the scapula to protrude outward (winging). This condition is more noticeable when the patient tries to push against a wall, as the scapula fails to stay in place.

  • Pectoralis minor is a small muscle that lies deep to pectoralis major.
  • It originates from ribs 3-5 and inserts on the coracoid process of the scapula.
  • It stabilises the scapula and contributes to protraction of the scapula.

Pectoralis Minor

Shoulder (glenohumeral) joint

A good understanding of the anatomy and functioning of the shoulder joint is required to take a history from, and examine a patient with, a shoulder problem. Knowledge of normal anatomy and function is vital for making a differential diagnosis and organising appropriate referral or further management.

The shoulder joint is a synovial joint, formed by the articulation between the glenoid fossa of the scapula and the head of the humerus. Muscles attached to the pectoral girdle and upper limb act on the shoulder joint. Movements at the shoulder joint can take place independently but are usually accompanied by movements of the scapula and clavicle.

Anatomy of the shoulder joint

What movements take place at the shoulder joint

Can you name these movements? Click on the image for the answer

Answer

Answer

Answer

Answer

Answer

Answer

Answer

The great degree of movement possible at the shoulder comes at the expense of stability, and as a result the shoulder joint is prone to dislocation. For this reason, there are some important features of the joint that work hard (and successfully) to maintain stability The long head of biceps runs from the supraglenoid tubercle, through the joint capsule to the biciptal groove and helps stabiise the shoulderWhat other factors help to maintain stability at the shoulder joint?

Structures that stabilise the shoulder joint

Answer

Factors stabilising the shoulder joint: Tendon of biceps brachiiGlenoid labrum Fibrous joint capsule Ligaments Rotator cuff muscles

The Rotator Cuff

The glenoid cavity is very shallow, this is compensated for by a group of 4 short muscles known as the rotator cuff. They attach the sacpula to the humerus. They each have individual actions but work together to hold the humeral head securely within the glenoid cavity thus stabilising the joint. This arrangement allows the large muscles around the shoulder to move the joint freely.Can you find 3 of the rotator cuff muscles on the image of the posterior scapula opposite? What is the 4th muscle and why can't you see it on this image?

Subscapularis (the only muscle located on the anterior aspect of the scapula)

Supraspinatus

Infraspinatus

Teres minor

Answer

Rotator cuff and stabilisation of the shoulder joint

The rotator cuff muscles form a tendinous cuff (or ring) that is continuous with the joint capsule and surrounds the shoulder joint. They help to stabilise the shoulder by:

  1. Centralising the humerus in the glenoid cavity
  2. Creating tension to compresses the humeral head into the glenoid fossa
  3. Providing dynamic stabilisation by fine-tuning the movements of the humeral head when the arm moves.
  4. Tightening the joint capsule

Click here

Can you name the attachments and innervation of supraspinatus?

Subscapularis

Which nerves supply subscapularis?

Upper and lower subscapular nerves

Answer

Infraspinatus and teres minor

There are 4 large muscles attaching the trunk and the scapula to the arm:

  • Latissimus dorsi
  • Teres major
  • Pectoralis major
  • Deltoid
These four muscles act on the shoulder joint and their role is to move the arm in space. This allows us to position the hand and the elbow correctly to grasp objects.

Muscles which move the arm in space

Latissimus Dorsi is a large, flat, triangular muscle that sweeps over the lumbar region and lower thorax and converges to a narrow tendon that inserts on the anterior surface of the humerus. In taking this path, it contributes to the posterior wall of the axilla (armpit). It is responsible for extension, adduction, and medial rotation of the shoulder (like when you pull something towards you or reach behind your back).. Teres Major is a smaller muscle arising from inferior angle of the posterior aspect of the scapula and inserting onto the anterior surface of the humerus. It also allows extension, adduction and medial rotation of the shoulder joint. Label these muscles on the diagram opposite:

Latissimus dorsi and teres major

Teres major

Latissimus dorsi

Insertion and innervation of latissimus dorsi and teres major

Make sure that you can identify, on a humerus, the area where latissimus dorsi and teres major insert (use the image opposite or compete anatomy to help)Which nerve supplies latissimus dorsi?Which nerve supplies teres major?

Answer

Answer

Lower subscapular nerve

Thoracodorsal nerve

Pectoralis major

The pectoralis major muscle is the largest and most superficial muscle of the anterior wall Its inferior margin makes up the anterior wall axilla. It has two heads. Label the sternal head and the clavicular head of pectoralis major on the image opposite. Where does pectoralis major insert?What is its nerve supply?

Sternal head

Clavicular head

Answer

Answer

Intertubercular sulcus (anterior humerus)

Medial and lateral pectoral nerves

Deltoid

Deltoid is a large muscle which is responsible for the rounded shape of the shoulder. It is a powerful abductor of the arm it is vital for the activities of daily living, but it does not initiate this movement (see supraspinatus)

Locate these bony landmarks on a skeleton or use complete anatomy

Case courtesy of Frank Gaillard, Radiopaedia.org, rID: 18279

Clinical Case 2

A patient sustains a fracture of the surgical neck of the humerus. At a 6 week follow-up the patient is unable to abduct the affected arm at the shoulder against resistance and has a patch of numbness of skin overlying deltoid.What is the diagnosis? Explain your reasoning?

Answer

A fracture of the surgical neck of the humerus commonly affects the axillary nerve, which runs posteriorly through the quadrilateral space and comes into close contact with the surgical neck of the humerus.The axillary nerve supplies deltoid muscle. Inability to abduct the arm against resistance suggests weakness of the deltoid muscle which is primarily responsible for shoulder abduction.The axillary nerve also provides sensory innervation to the skin overlying the deltoid muscle, specifically in the "regimental badge" area of the shoulder. Given these findings, the most likely diagnosis is an axillary nerve injury resulting from the fracture.

Clinical Case 2: Answer

Quadrilateral space and axillary nerve

You have now come to the end of this Workbook and SDL. Well done! Next, test yourself by using the following two active learning techniques, alone or with friends: 1. Without looking at any notes, what can you say / draw / write about the structures in the following checklist? Tick them off if you can say something about them! Bones & joints Clavicle,s capula and proximal humerus The shoulder joint Factors that stabilise the shoulder joint Muscles and movements Muscles that move the scapula; trapezius; levator scapulae; rhomboid major; rhomboid minor; serratus anterior; pectoralis minor The rotator cuff muscles; supraspinatus; infraspinatus; subscapularis; teres minor Muscles that move the arm in space; latissimus dorsi; teres major; pectoralis major, deltoid Nerves Axillary nerveLong thoracic nerveAccessory nerve Thoracodorsal nerveDorsal scapular nerveMedial and lateral pectoral nerves 2. Try the UL1 formative MCQs on Minerva.