Week 3 Flashcards
The humerus
Classified as a long bone
Articulations:
-proximal aspect: articulates with the glenoid fossa of the scapula, forming the glenohumeral joint
-distally aspect: articulates with the head of the radius and Trochlear notch of the ulna forming the elbow joint
Proximal landmarks of humerus
Head: the upper end of the humerus
Anatomical neck: separates the head from the greater and lesser tubercles
The greater tubercle: located laterally, it serves as an attachment site for 3 of the rotator cuff muscles: supraspinatus, infraspinatus, teres minor
The lesser tubercle: smaller, located more medially, it provides attachment for the subscapularis
Intertubercular sulcus: a deep groove which separates the 2 tubercles. The tendon of the long head of the biceps brachii emerges from the shoulder joint and runs through this groove
Lips: the edges of the intertubercular sulcus, pectoralis major, teres major and latissimus dorsi insert on the lips of the intertubercular sulcus
The surgical neck: runs from the tubercles to the shaft of the humerus, frequent site of fracture, axillary nerve and posterior circumflex artery at risk
Shaft landmarks of the humerus
The deltoid tuberosity: located on the lateral side of the numeral shaft, where the deltoid muscle attaches
The radial groove: a shallow depression that runs diagonally down the posterior surface of the humerus, the radial nerve lies within this groove
Provides attachment for a lot of muscles
Distal region of humerus
Medial and lateral supraepicondylar ridges: formed by the lateral and medial borders of the distal humerus
Lateral and medial epicondyles: immediately distal to the supraepicondylar ridges
Trochlea: articulates with the trochlea notch of the ulna to form the elbow joint
Capitulum: articulates with the head of the radius to form the elbow joint
Coronoid, radial and olecranon fossae: 3 depressions which accommodate the forearm bones during flexion or extension at the elbow
What part of humerus articulates with radius
Capitulum
Forms radio-capitellar joint
What part of humerus articulates with the ulna
Trochlea
Pectoral girdle
Formed by two bones: the scapula posteriorly and the clavicle anteriorly
These bones are part of the appendicular skeleton
Connect upper limb to axial skeleton
The clavicle
S-shaped long bone that extends between the manubrium of the sternum and the acromion of the scapula
The medial 2/3 of the shaft of the clavicle are convex anteriorly
The lateral 1/3 is flattened and concave anteriorly
-these curvatures increase the resilience of the clavicle
The clavicle is divisible into 3 regions:
-the sternal end: contains a large facet for articulation with the manubrium of the sternum at the sternoclavicular joint
-the shaft: acts as a point of origin and attachment for several muscles- deltoid, trapezius, subclavius, pectoralis major, sternocleidomastoid and sternohyoid
-the acromial end: contains a small facet for articulation with the acromion of the scapula at the acromioclavicular joint (a gliding synovial joint)
Surfaces of the clavicle
The superior surface of the clavicle is smooth
The inferior surface of the clavicle is rough has following surface markings:
-Conoid tubercle: near the acromial end, gives attachment to the conoid ligament
-trapezoid line: near acromial end, gives attachment to trapezoid ligament
-Subclavian groove: site of attachment of the subclavius muscle
-impression for the costoclavicular ligament: at the sternal end gives attachment to the ligament binging the 1st rib to the clavicle, limiting elevation of the shoulder
Scapula
Flat bone
It lies on the posterolateral aspect of the thorax overlying the 2-6/7 rib
The convex posterior surface: divided by the spine of the scapula into the supraspinous fossa and infraspinous fossa
- the infraspinatus muscle originates from the infraspinatus fossa and the supraspinatus muscle originates from the supraspinatus fossa
The concave anterior surface:
-contains a large subscapular fossa, the subscapularis muscle originates from here
The spine of the scapula continues laterally as the acromion
The lateral surface:
-the lateral surface of the scapula faces the humerus
-its the site of the glenoid fossa and therefore the glenohumeral joint, also where teres minor originates
-supraglenoid tubercle located superior to glenoid fossa, the place of attachment of the long head of the biceps brachii
-infraglenoid tubercle located inferior to glenoid fossa, the place of attachment of the long head of the triceps brachii
The coracoid process: projects anterolaterally, pectoralis minor, coracobrachialis, short head of biceps brachii
Joints of the pectoral girdle
Sternoclavicular joints anteriorly
Acromioclavicular laterally
Glenohumeral joints laterally
Scapulothoracic joint posteriorly: there’s muscular connection between the shoulder girdle and rib cage which is formed by muscles including the trapezius, rhomboids and Serratus anterior
Sternoclavicular joint
Only articulation between upper limb and axial skeleton
Saddle type synovial joint (high mobility) between clavicle and manubrium
Articulating surfaces: the Sternoclavicular joint consists of the sternal end of the clavicle, the manubrium and part of the 1st costal cartilage
The joint is separated into 2 compartments by the articular discs
Articular disc allows the clavicle and the manubrium to slide over eachother more freely allowing for the rotation and movement in a 3rd axis
The sc joint is made stable and strengthened by?
The Shoulder muscles
The joint capsule: consists of a fibrous outer layer and inner synovial membrane that produces synovial fluid to reduce friction between the articulating structures
Ligaments:
-Sternoclavicular ligaments (anterior and posterior) these strengthen the joint capsule anteriorly and posteriorly
-interclavicular ligament spans the gap between the sternal ends of each clavicle and reinforces the joint capsule superiorly
-Costoclavicular ligament the 2 parts of this ligament (often separated by bursa) bind at the 1st rib and cartilage inferiorly and to the anterior and posterior borders of the clavicle superiorly
Acromioclavicular joint
Plane type of synovial joint between the acromial end of clavicle and acromion of the scapula
2 atypical features: the articular surfaces of the joint are lined with fibrocartilage instead of hyaline, the joint cavity is partially divided by an articular disc
What is the AC joint strengthened by to ensure stability?
The joint capsule
Trapezius muscle: reinforces the posterior aspect of the joint capsule
The acromioclavicular ligament: intrinsic runs horizontally from the acromion to the lateral clavicle
The coracoclavicular ligament : extrinsic:
-trapezoid ligament runs from coracoid process of scapula to the trapezoid line of the clavicle
-vertical conoid ligament- runs vertically from the coracoid process of the scapula to the conoid tubercle of the clavicle
The shoulder joint/ glenohumeral joint
Ball and socket synovial joint between scapula and humerus
Large mobility at expense of stability
Articulating surfaces:
-articulation of head of humerus with glenoid fossa of scapula
-head of humerus much larger than glenoid fossa
To increase stability the glenoid fossa is deepened by a fibrocartilage rim (increases its surface) called the glenoid labrum
Factors that contribute to mobility of shoulder joint
Type of joint- ball and socket synovial joint
Bony surfaces- shallow glenoid cavity and large humeral head
Inherent laxity of the joint capsule
The joint capsule is lax, permitting greater mobility (particularly abduction)
Factors that contribute to stability of shoulder joint
1.Glenoid labrum
2.Ligaments of the shoulder joint:
- glenohumeral ligaments (superior,middle, inferior)
These groups of ligaments form the joint capsule and stabilise anterior aspect of the joint
-coracohumeral ligament: attaches coracoid process to greater tubercle and supports superior part of joint capsule
-coracoacromial ligament: between acromion and coracoid process of scapula forming coracoacromial arch, prevents superior displacement humeral head
-transverse humeral ligament: between two tubercles of humerus, holds tendon of long head of biceps in intertubercular groove
3.Rotator cuff muscles: surround shoulder joint and attach to tuberosities of humerus while fusing with joint capsule, the resting tone of these muscles act to compress the humeral head into glenoid cavity
4.Biceps tendon: acts as a minor humeral head depressor
Bursae of the shoulder joint
To reduce friction in shoulder joint
5 bursae
3 are contiguous: subacromial, subcoracoid, subscapular
Subdeltoid
Suprascapular
Subacromial bursa
Located deep to the deltoid and acromion
Superficial to supraspinatus tendon and joint capsule
The subacromial bursa reduces friction beneath deltoid promoting free motion of the rotator cuff tendons