L1: The Pectoral Girdle Flashcards
What are the 3 neuromuscular spaces in the upper limb?
The axilla (armpit), the cubital fossa and the carpal tunnel.
What are the the joints of the upper limb?
- The wrist
- The shoulder
- The elbow
- There are also lots of small joints in the hand
What landmarks are visible on the anterior scapula?
The anatomical borders: The medial border, lateral border, inferior border (and angle) and superior border (and angle).
The coronoid process - an attachment for several muscles on the lateral region.
The acromion posterior to this. This is a flat projection. This attaches to the clavicle forming the acromioclavicular joint. Its also is a site of attachment for many muscles.
The glenoid fossa. This is where the humorous articulates with the scapula.
On the anterior surface is a hollow area called the sub scapula fossa.
What landmarks are visible on the posterior scapula?
On the posterior surface we still see the different borders. The ridge of bone on the back is called the spine of the scapula. This is continuous with the acromion. It separates the posterior surface into an upper supraspinous fossa and an infraspinous fossa. The acremonium is a more posterior landmark.
How does the humorous articulate with the scapula?
It attaches at the glenoid fossa forming the glenohumeral joint.
Why is the shoulder joint describes as incongruent? What is the advantage of this?
The glenoid fossa is not very hollow. There is also a loose capsule. It is not a good fit. This however means there is a great range of motion at the shoulder joint.
What are the movements available at the shoulder joint?
Abduction; Adduction; Circumflexion; Flexion; Extension; Medial rotation and lateral rotation.
Abduction - away from the body Adduction - towards the body
Medial and lateral rotation sometimes called internal and external rotation. The humorous is rotating on its axis.
What is the role of the pectoralis major and pectoralis minor?
They are adductors and medial rotators of the shoulder joint.
The pectoralis major has a clavicular part and a sternal part. It insertion is on the humorous. When the muscle contracts is adduction and medial rotation of the shoulder joint. When it contracts it pulls on the bone it is attached to. It is attached to fixed bone. It cannot pull the clavicle and the sternum out of place. The humorous however can move at its articulation with the shoulder joint. When it contracts it pulls the humorous towards the body and internally rotating.
Pectorals minor is a small muscle. It lies deep to the pectroalis minor. Its origin point is rib 3-5. an inserts on the coracoid process of the scapula. It cannot pull on the ribs as they are foxed in position. The scapula is the more movable joint. It pulls on its attachment in the coracoid process. It stabilises the scapula and assists with the protraction.
What is the role of the serrates anterior?
The serratus anterior attaches onto the anterior medial border of the scapula. The muscle sweeps around towards the anterior chest wall and inserts on ribs 1-8. This results in protraction of the scapula and lengthening of the upper limb.
What are the muscles of the posterior pectoral girdle?
The superficial muscles:
The Lattisimus dorsi
- The Trapezius
The deep muscles:
- The Rhomboid major (attaches to T1-T5 and the medial border of the scapula)
- The Rhomboid minor (attaches to C7-T1 and the root of the scapula)
- The Levator scapulae (attaches to C1-4 and the medial aspect of the scapula)
What is the role of the deltoid and teres major?
The deltoid muscle sits over the shoulder joint. Its origin is the clavicle and the scapula. It inserts on the deltoid tuberosity on the humorous. It pulls the humorous out - it is an abductor. It can also contribute to flexion and extension of the joint. The anterior fibres can assist with flexion and the posterior fibres can assist with extension.
The teres major has an origin from the scapula posteriorly but inserts anteriorly on the humorous. Due to the orientation of the fibres and the direction, it pulls and medially rotates and adducts the shoulder.
What muscles make up the rotatory cuff?
- Supraspinatous - starts abduction (first ~20 degrees after that deltoid takes over ). Sits in the supraspinous fossa. They travel under the acremonium and inserts of the greater tubercle of the humorous.
- Infraspinatus and teres minor: laterally rotate the shoulder - found on the posterior aspect. Also inserts on the greater tubercle of the humorous. They act on the shoulder joint in a similar way. They both, laterally rotate the shoulder.
- Subscapularis: adducts and medially rotates the shoulder - on the anterior aspect of the scapula. Lies in the subscapular fossa. Inserts on the anterior lesser tubercle of the humorous.
What are the major nerves and vessels of the pectoral region and shoulder?
- The axillary artery which becomes the brachial artery (and vein)
- The axillary artery gives rise to the anterior and posterior cephalic humeral arteries around the surgical neck fo the humorous
- The cephalic vein is a superficial vein that runs up the lateral side of the arm, when it gets into the axilla, to drains into the axilla vein.
- The brachial plexus is found in the axilla
Give examples of pathology of the pectoral girdle.
• Bones and joints can be fractured or dislocated, or less commonly, become infected (osteomyelitis). Joint surfaces can be come worn (osteoarthritis) – this is very common.
• Muscles and tendons can be torn, become inflamed (tendonitis) or trapped (this is called impingement)
Nerves can be injured in various ways (cut, torn, stretched, compressed, avulsed) or they may become inflamed (neuritis)
Give examples of tendon pathology.
Rotator cuff tendons can be torn or become inflamed. The most common problem is the supraspinatous tendon becoming trapped (impinged) between the humeral and the acromion and becoming inflamed. Injury leads to impaired movement, instability and pain.
