Lecture 3: Pectoral girdle Flashcards
What does the “pectoral girdle” refer to and what is its main function
These are the two bones: (scapula + clavicle) part of the upper limb that link it to the axial skeleton. Its main purpose is to allow the wide range of movement of upper limb required for manipulation of the environment by acting as a mobile base for muscle attachment which stabilises the shoulder joint
Differentiate pectoral girdle vs shoulder joint
Pectoral girdle is clavicle and scapula which articulate at the acromioclavicular joint whereas shoulder joint is between glenoid fossa of the scapula and the head of the humerus
Describe the clavicle main purpose and appearance
A sinuous long bone with medial convexity pointing anteriorly, largely subcutaneous forming a strut between manubrium and acromial process of scapula, holding it out against the chest muscles pulling it in. It takes a lot of the force from the arm, therefore more likely to break in the medial curve where it isn’t supported by muscle attachments.
What are the three main features on the inferior view of the clavicle for attachment of ligaments/ muscle (medial to lateral). What are these important for
All important for stabilising the clavicle.
- First costoclavicular roughened area for attachment of costoclavicular ligament
- Subclavian groove for subclavius muscle attachment
- Coracoclavicular ligament attachement ridge
What are the anterior muscles that have origin from the axial skeleton and insert on the humerus
Pectoralis major
What are the anterior muscles that have origin from the axial skeleton and insert on the pectoral girdle
Pectoralis minor, Subclavius and Serratus anterior
Describe innervation, origin and insertion of pectoralis major
Nerve: Lat & med pectoral n.
2 Origins: Sternocostal head and clavicular head (closer to sternum)
Insertion: Lateral intertubercular groove of humerus
Primary movements of pectoralis major
Attaches horizontal across the chest so
- adducts humerus
- internally rotate humerus
- protract scapula by pulling on humerus
Describe innervation, origin and insertion of pectoralis minor
Nerve: med pectoral n.
O: 3,4,5 ribs
I: coracoid process of the scapula
Primary movements of pectoralis minor
Attaches northeast on the chest so
-can depress scapula
Describe innervation, origin and insertion of subclavius
Nerve: C5
O: costal cartilage of 1st rib
I: subclavian groove of clavicle
Primary movements of subclavius
Braces the clavicle by stopping it being pulled out when clavicle moves up
Describe innervation, origin and insertion of Serratus anterior
Nerve: Long thoracic n.
O: ribs 1-8 or 1-9
I: medial border of the scapula
Primary movements of Serratus anterior
Protracts scapula (scapular abduction) and its lower fibres can help to superiorly rotate scapula (lowkey abduct)
Describe the general appearance of scapula
A flat triangular bone that covers the posterolateral surface of ribs 2-7, with 3 angles(corner), borders, protuberences and surfaces. Lateral end is the end of the 3 protuberences that allow the glenohumeral joint to articulate and acromioclavicular joint. Lateral end is stiff and thick to allow lots of muscles to attach
Describe the 3 protuberences and therefore surfaces of the scapula with respect to 3 angles and borders
On the posterior surface of scapula is protuberence of spine which runs from medial border to lateral, ending in the corner of glenoid fossa (lateral angle). This divides the post. surf. of scapula into supraspinous fossa (closer to superior angle/border) and infraspinous fossa (closer to inferior angle/border).
The last surface is the anterior surface called subscapula fossa.
Protuberence of coracoid process is more anterior than acromion which is at the lateral end of the spine.
Describe the inside of sternoclavicular joint
It is a saddle shaped synovial joint between medial end of clavicle and the manubrium of sternum. There is a a meniscus (intra articular fibrocartilagionous disc) that lies between the articulating surfaces of the two bones.
Describe the 4 ligaments that strengthen the sternoclavicular joint
- Anterior + Posterior sternoclavicular ligament that is a thickening of the capsule of S.C joint (posterior one stronger).
- Interclavicular ligament which links across the jugular notch
- Costoclavicular ligament which is a fulcrum for upper clavicular movements and chief stabiliser of joint (follows subclavius).
Describe the inside of the acromioclavicular joint
It is a synovial joint between the lateral end of the clavicle and the medial border of the acromion. There is a wedge shaped fibrocartilagenous intra articular disc between the articulating surfaces of the two bones.
Describe the ligaments that support the acromioclavicular joint
The joint capsule itself is strengthened by the intrinsic acromioclavicular ligament.
The joint is supported by two parts of the coracoclavicular ligament-> conoid + trapezoid. these help to save energy to fight the pull of the trapezius muscle on the acromion.
What are the 4 posterior muscles that originate from axial skeleton to pectoral girdle
Trapezius, levator scapulae and rhomboid major and minor
What is the innervation, origin and insertion of the trapezius (all three parts)
N: accessory nerve (Cranial nerve 11)
Origin: external occipital proturberance, spinous processes of c7- T12
Insertion: anatomical horseshoe
Superior- clavicle, Middle: acromion Inferior: spine of scapula
What are the primary movements of trapezius (all, sup, mid, inf, sup+inf only on the scapula
All together : Retract the scapula Sup: elevates scapula (suspends neck) Mid: retracts Lower: depresses Sup + Inf: superior rotation
What is the innervation, origin and insertion of levator scapulae
N: Dorsal scapular nerve (C3&C4)
Origin: cervical spinous processes 1-4
Insert: superior angle of the scapula
Are levator scapulae and rhomboid maj+ minor superficial or deep to trapezius
deep
What are the 1’ movements of levator scapulae
elevate scapula
What is the innervation, origin and insertion of Rhomboid minor and major
N: Dorsal scapular nerve
Origin: Minor is spinous processes C7,T1. Major is T2 to T5
Insert: medial border of scapula, with minor inline with spine of scapula and major lower than that.
What is the primary movement of rhomboid major and minor
retracts the scapula.
What is the innervation, origin and insertion of Latissimus dorsi- which has a aponeurosis before the muscle belly
N: Thoracodorsal n
O: spinous processes of T7 to S5
I: floor of the intertubercular groove on the anterior of the humerus.
What is the primary movement of latissimus dorsi
Adduct the humerus, internally rotates humerus and the lower fibres can depress scapula by pulling on the humerus
