Biomech unit 4 Upper limb & Spine - deck 1 Flashcards
What 5 parts make up the upper limb?
- Shoulder girdle
- Arm
- Forearm
- Wrist
- Hand
What bones form the shoulder girdle ?
The clavicle and the scapula
What bone forms the arm ?
The humerus
What bones form the forearm ?
The ulna and radius
What bones form the wrist ?
The 8 carpal bones
What bones form the hand ?
The metacarpals and the phalanges
What are the 3 major joints of the upper limb which give the upper limb its wide range of motion?
Shoulder, elbow and wrist joints
What is the major function of the upper limb ?
To position the hand in space
What is the upper limb designed to achieve ?
A wide range of movement rather than for weight bearing. To position the hand in space
What bones make up the spine (also called vertebral column)?
24 vertebrae and the sacrum and the coccyx
What about the spines structure gives it a remarkable amount of flexibility as well as the strength required to support the upper body?
Its segmented structure
What joint is the most intricate joint complex in the human body?
The shoulder joint
What forms the shoulder joint ?
The humerus, the shoulder girdle (clavicle and scapula) and the thorax
Name the articulations which form the shoulder joint
- The glenohumeral
- The acromioclavicular
- The sternoclavicular
- The scapulothoracic
State what type of articulation each of the 4 articulations of the shoulder joint are
hint one of them is different from the others
- The glenohumeral, the acromioclavicular and the sternoclavicular, are synovial articulations
- The scapulothoracic, is a bone on-muscle-on-bone articulation
Specifically what type of joint is the glenohumeral joint ?
A ball-and-socket shaped synovial joint
What forms the glenohumeral joint
The humeral head and the glenoid fossa of the scapula
What about the glenoid fossa allows for a wide range of motion of the glenohumeral joint ?
The glenoid fossa is particularly shallow
What is the disadvantage of the shallow glenoid fossa in the glenohumeral joint ?
The articulation is less stable than it would be with a more developed socket therefore dislocations of the glenohumeral articulation are not infrequent
What 3 things help provide stability to the glenohumeral articulation?
- A thick cartilaginous rim called the glenoid labrum.
- The articulation is surrounded by a capsule
- The rotator cuff
What is the rotator cuff formed by?
A group of four muscles and their tendons:
- Subscapularis
- Infraspinatus
- Supraspinatus
- Teres minor
Think - SITS
Describe how the rotator cuff provides stability to the glenohumeral articulation
- They form a cuff of tissue, like the fingers of a hand cupping a ball, around the glenohumeral articulation.
- They provide dynamic restraints to anterior, posterior and inferior displacement. This is illustrated in Figure 4(B)
- The rotator cuff pushes on the humeral head, preventing any anterior-posterior movement, thereby stabilising the joint.
What type of joint is the acromioclavicular joint and what is the joint formed by ?
- It is a small synovial joint
- It is formed by the proximal acromion of the scapula and the distal clavicle
What provides stability to the acromioclavicular joint
The superior and inferior acromioclavicular ligaments which prevent the joint being pulled apart.
Further stability is provided by the two parts of the coracoclavicular ligament between the clavicle and coracoid process of the scapula which limit the upward movement of the clavicle
What is the range of motion of the AC joint and state why it is so limited
- Range of motion is a few degrees during arm abduction.
- It is restricted by the thorax and the muscle attachments
What type of joint is the sternoclavicular joint and what is it formed by ?
It is a small synovial joint formed by the manubrium of the sternum and the proximal clavicle
Name the only bony joint to connect the shoulder girdle to the trunk
The sternoclavicular joint
During arm elevation what also happens to the clavicle ?
It also elevates at the sternoclavicular joint
State the degree of elevation which occurs for the clavicle during arm elevation
- For the first 90 degrees of arm elevation the clavicle elevates by around 4 degrees for every 10 degrees of arm elevation.
- Beyond 90 degrees of arm elevation the elevation of the clavicle is almost negligible
During elevation and depression the clavicle rotates about an axis determined by what?
The attachment of the costoclavicular ligament
State what type of articulation the scapulothoracic articulation is and also state what it is formed by
- A bone-muscle-bone articulation between the scapula and the posterior thoracic wall
Why is the scapulothoracic articulation not a joint in the truest sense unlike the other 3 articulations/joints of the shoulder joint?
Because there are no direct bony or ligamentous connections between the scapula and thorax.
What is the function of the scapulothoracic articulation?
It contributes significantly to the wide range of motion of the scapula, which greatly enhances the mobility of the entire shoulder complex.
What is the anterior surface of the scapula separated from the posterior thoracic by ?
By two broad flat muscles: the serratus anterior and subscapularis muscles.
State the origin and insertion of the serratus anterior
It originates on the upper eight or nine ribs and inserts on the anterior surface of the scapula along its vertebral border
What is the functions of the serratus anterior muscle
It helps to hold the scapula against the thorax, thus preventing “winging”, and is a strong abductor that is useful in pulling or pushing movements.
State the origin and insertion of the subscapularis muscle
It s originates from the subscapular fossa and inserts on the lesser tubercle of the humerus
What is the function of the subscapularis muscle ?
It is one of the rotator cuff muscles (so acts to stabalise shoulder joint) and acts to medially rotate the humerus.
What do all 4 articulations of the shoulder joint act together to provide ?
The wide range of motion of the shoulder joint
Define what shoulder elevation and depression is
- Shoulder elevation = the movement of the humerus away from the side of the thorax in any plane
- Shoulder depression = the movement of the humerus towards the side of the thorax (i.e. When the arm is moved towards the trunk from an elevated position) in any plane
What is the amount of shoulder elevation quantified as ?
The angle of elevation
What forms the boundries of the angle of elevation ?
It is the angle between the axis passing through the shoulder joint centre parallel to the longitudinal axis of the trunk (this is simply describing the vertical line in pic) and the longitudinal axis of the humerus
For a subject in the anatomical position, with their arm against the side of their trunk what will the shoulder elevation angle be ?
0 degrees
For a subject in the anatomical position, with their arm held out so that it is horizontal what will the shoulder elevation angle be ?
90 degrees
