ted - sample limbs

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Ted - Sample Limbs

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MCD: Introductions to Cells - Cells and Organelles

The Shoulder & Arm

1. Name the bones and joints of the upper limb from the shoulder girdle to the elbow.

Clavicle: the collarbone.

The clavicle is the only bony attachment between the trunk and the upper limb.

It is palpable along its entire length and is an S-shaped contour.

The acromial end is flat, whereas the sternal end is more robust and quadrangular in shape.

The acromial end has a small oval facet on its surface for articulation with the medial end of the acromion of the scapula.

The sternal end has a larger facet for articulation with the manubrium of the sternum.

The inferior surface of the lateral third of the clavicle possesses a tuberosity containing the conoid tubercule and trapezoid line. It is the first bone to ossify in utero and does so by intramembranous ossification.

Scapula: a large flat triangular bone with:

three angles (lateral, superior, and inferior);

three borders (superior, lateral, and medial);

two surfaces (costal and posterior); and

three processes (acromion, spine, and coracoid process)

The lateral angle is marked by the glenoid cavity (articulates with the head of the humerus glenohumeral joint).

The large triangular shaped roughening (the infraglenoid tubercule) inferior to the glenoid cavity is the site of attachment for the long head of the triceps brachii.

The supraglenoid tubercule is the site of attachment of the long head of the biceps.

The prominent spine divides up the posterior surface (into infraspinous and supraspinous).

The acromion (Greek = acromius meaning summit) is an anterolateral projection of the spine articulates with the clavicle.

The lateral border is thick and strong as it is used for muscle attachments.

The superior border is marked on its lateral end by:

Coracoid process: crows beak like structure

Suprascapular notchNB: the spine and coracoid process are easily palpable

Proximal Humerus: the hind bone of the arm. The head is a half-spherical shape and projects medially and somewhat superiorly to articulate with the much smaller glenoid cavity of the scapula.

There are 2 tubercles (greater and lesser) that are prominent landmarks for attachment sites for rotator cuff muscles:

Greater Tubercle:

Supraspinatus

Infraspinatus

Teres minor

Lesser tubercle:

- Subscapularis.

It is important to note the surgical neck because the neck is weaker than the proximal regions of the bone, fractures are common there. The associated axillary nerve and posterior circumflex humeral artery can be damaged by fractures here.

2. Identify in a living subject and in appropriate imaging;

a) The clavicle and its sternoclavicular and acromioclavicular jointsb) The lateral and medial borders and inferior angle of the scapula, the scapula spine, acromion process, coracoid process and glenoid fossa.9. Explain the significance of the term synovial ball-and-socket joint using the shoulder joint as an example.

10. Summarise the main factors stabilising the shoulder joint.

Joints

Sternoclavicular: this is the only real bony joint between the upper limb and the rest of the body.

This is between the medial end of the clavicle and the clavicular notch on the manubrium of the sternum and the first costal cartilage.

It is synovial and is held in place by 4 ligaments:

1. anterior sternoclavicular ligament

2. posterior sternoclavicular ligament

3. interclavicular ligament

4. costoclavicular ligament

These ligaments make it particularly strong joint.

It allows for movement of the clavicle mainly in the anteroposterior and vertical planes although some rotation occurs

It is surrounded by a joint capsule and articular disc and can be damaged resulting in sternoclavicular subluxation and dislocation.

Acromioclavicular: small synovial joint between the acromion of the scapula and the acromial end of the clavicle. It is held together by:

acromioclavicular ligament minor dislocations occur when this ligament is torn coracoclavicular ligament important as is provides most of the weightbearing support for the upper limb on the clavicle and maintaining the position of the clavicle on the acromion. Major dislocations occur if this ligament if torn. coraco-acromial ligamentIt allows for movement in the anteroposterior and vertical planes together with some axial rotation.This is often injured by falls onto an outstretched hand (ligaments are torn).

Glenohumeral: the shoulder joint.

It is a synovial ball and socket joint between humerus and glenoid process of the scapula.

It allows for great mobility at the expense of stability (any stability comes from the ligaments rather than the articulation itself). It is very shallow and the head of the humerus lies in the glenoid labrum which is a fibrocartalaginous collar which attaches to the margin of the fossa.

The main structural differences between synovial and fibrous joints is the existence of capsules surrounding the articulating surfaces of a synovial joint and the presence of lubricating synovial fluid within that capsule (synovial cavity). The capsule of the glenohumeral joint can protrude through the holes in the fibrous membrane that surrounds the joint forming bursae (a fluid filled sac):

The subacromial bursa (between the humeral head and the acromial process often a site of pathology for shoulder interference)

The subtendinous bursa of subscapularis (between the subscapularis muscle and the fibrous membrane)

The synovial sheath that extends along down the long head of the biceps brachii.

The coraco-acromial arch lies above the shoulder joint and stops the humerus rising superiorly against the acromion. It is held in place by the rotator cuff muscles and stabilised by a number of ligaments:

Gleno-humeral ligaments strengthen the anterior portion of the shoulder capsule Coraco-humeral ligament strengthens the capsule superiorly Transverse humeral ligament holds the tendon of the long head of biceps in the inter-tubercular groove

Scapulo-thoracic: movements of the scapulo-thoracic joints are important and occur mainly when the arm is abducted more than 90. It is a theoretical concept but allows for certain sorts of movement. The main movements are:

Elevation and depression of the scapula

Protraction of the scapula forward and lateral movement against the chest wall

Retraction backward and medial movement against the chest wall

Rotation of the scapula

NB: Movement is not only occurring at the shoulder joint. Movement occurs at the scapulo-thoracic joint as well as the shoulder joint proper.

2. Demonstrate the main movements of the shoulder girdle, shoulder joint and elbow

Movements of the Joints and muscles creating themShoulder Joint:

Flexion:

Clavicular head of pectoralis major Anterior fibres of deltoid Coraco-brachialis Biceps Extension Latissimus dorsi Abduction:

Supraspinatus (first 30 degrees) Central fibres of deltoid (after 30 degrees) Adduction:

Pectoralis major Latissimus dorsi Internal rotation subscapularis External rotation infraspinatus Circumduction a combination of all movementsMuscles involved in preventing shoulder dislocation: Rotator cuff muscles depress the humeral head into the glenoid

Deltoid

Coraco-brachialis

Short and long heads of biceps

The scapulo-thoracic joint:

Elevation superior trapezius, levator scapulae, rhomboids Depression inferior trapezius, pectoralis minor, serratus anterior Protraction pectoralis minor, serratus anterior Retraction rhomboids, middle trapezius, latissimus dorsi Rotation elevation and depression of the glenoid fossa: Elevation superior trapezius, inferior trapezius, serratus anterior Depression pectoralis minor, latissimus dorsi, rhomboids and levator scapulaeThe Elbow Joint:

Flexion biceps, brachialis, brachioradialis (pronator teres) Extension triceps (anconeus)4. Name and demonstrate the position, main attachments and actions of;MuscleOriginInsertionInnervationFunction

Anterior Pectoral Muscles

Pectoralis majorClavicular head-anterior surface of medial half of clavicle; sternocostal head-anterior surface of sternum; first seven costal cartilages; sternal end of sixth rib; aponeurosis of external obliqueLateral lip of inter-tubercular sulcus of humerusMedial and lateral pectoral nerves; clavicular head [C5,C6]; sternocostal head [C6,C7,C8,T1]Flexion, adduction, and medial rotation of arm at gleno-humeral joint;.clavicular head-flexion of extended arm; sternocostal head- extension of flexed arm

SubclaviusFirst rib at junction between rib and costal cartilageGroove on inferior surface of middle one-third of clavicleNerve to subclavius [C5,C6]Pulls tip of shoulder down; pulls clavicle medially to stabilize sternoclavicular joint

Pectoralis minorAnterior surfaces and superior borders of ribs III to V; and from deep fascia overlying the related intercostal spacesCoracoid process of scapula (medial border and upper surface)Medial pectoral nerve [C6,C7,C8]Pulls tip of shoulder down; protracts scapula

Serratus anteriorLateral surfaces of upper 8-9 ribs and deep fascia overlying the related intercostal spacesCostal surface of medial border of scapulaLong thoracic nerve [C5,C6,C7]Protraction and rotation of the scapula; keeps medial border and inferior angle of scapula opposed to thoracic wall

Posterior Pectoral Muscles