Upper limb Flashcards
Identify the major bones of the pectoral girdle and describe their main features.
The pectoral girdle consists of the scapula and clavicle. The scapula has a triangular shape with the following features:
Borders: Medial, lateral, and superior
Angles: Superior and inferior
Processes: Spine (divides posterior surface), Acromion (articulates with clavicle), Coracoid (projects antero-laterally)
Fossa: Subscapular (anterior), Supraspinous, and Infraspinous (posterior)
Glenoid fossa: Articulates with the head of the humerus.
The clavicle is an S-shaped bone that articulates medially with the sternum at the sternoclavicular joint and laterally with the acromion of the scapula at the acromioclavicular joint.
What type of joint is the shoulder joint, and how does it facilitate movement?
The shoulder joint is a ball and socket type of synovial joint, allowing movement in multiple axes (flexion, extension, abduction, adduction, rotation, and circumduction). The head of the humerus articulates with the glenoid cavity of the scapula, which is deepened by the glenoid labrum. Stability is provided by the joint capsule, ligaments (glenohumeral, coracohumeral, and transverse humeral), and the rotator cuff muscles.
Describe the function and importance of the rotator cuff muscles.
The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) stabilize the glenohumeral joint by holding the head of the humerus in the glenoid cavity of the scapula. These muscles allow for movements such as abduction, rotation, and elevation of the arm and are crucial for shoulder stability during motion.
How does the elbow joint allow for movement, and what are the key structures involved?
The elbow joint is a hinge type of synovial joint, allowing flexion and extension at the humero-ulnar and humero-radial joints, and pronation and supination at the proximal radio-ulnar joint. The joint capsule is weak anteriorly and posteriorly, but is reinforced by the medial and lateral collateral ligaments. The lateral ligament attaches to the annular ligament, which holds the radial head against the radial notch of the ulna.
What are the different types of synovial joints found in the upper limb, and provide examples for each.
The types of synovial joints in the upper limb include:
Plane (Gliding): Allows sliding or gliding movements. Example: acromioclavicular joint.
Hinge: Permits flexion and extension (uniaxial). Example: elbow joint.
Pivot: Allows rotation around a central axis. Example: proximal radio-ulnar joint.
Condyloid: Permits flexion, extension, abduction, adduction, and slight rotation. Example: metacarpophalangeal joints.
Saddle: Allows movements similar to condyloid joints but with a greater range. Example: carpometacarpal joint of the thumb.
Ball and Socket: Allows movement in multiple axes. Example: shoulder joint.
Describe the structure and function of the glenohumeral joint’s joint capsule and ligaments.
The glenohumeral joint capsule is a fibrous structure lined by a synovial membrane. It surrounds the joint and attaches to the margin of the glenoid cavity and the anatomical neck of the humerus. The capsule is strengthened by:
Glenohumeral ligaments (anterior)
Coracohumeral ligament (superior)
Transverse humeral ligament
These ligaments provide stability by holding the humeral head in place and preventing dislocation, particularly during arm movements.
What is the carrying angle of the elbow, and what is its clinical significance?
The carrying angle is the angle formed by the axes of the arm and forearm when the forearm is in full extension and supination. This angle is greater in females than in males and allows the forearms to clear the hips during walking or when carrying objects. Clinically, variations in the carrying angle can help assess injuries around the elbow and determine the type of fracture sustained after a fall on an outstretched hand.
Explain the consequences of a lesion to the axillary nerve following a fracture at the surgical neck of the humerus.
A lesion to the axillary nerve following a fracture at the surgical neck of the humerus can lead to:
Weakness in shoulder abduction due to impaired function of the deltoid muscle.
Sensory loss over the lateral aspect of the shoulder.
Atrophy of the deltoid muscle if the injury is severe and untreated.
Identify the major muscles involved in movements of the shoulder joint and their actions.
The major muscles involved in shoulder joint movements include:
Supraspinatus: Initiates abduction.
Deltoid (Middle fibers): Abduction.
Pectoralis major and Anterior deltoid: Flexion and medial rotation.
Latissimus dorsi and Posterior deltoid: Extension and lateral rotation.
Infraspinatus: Lateral rotation.
Subscapularis: Medial rotation.
These muscles work together to facilitate complex shoulder movements.
What are the main types of fractures that can occur in the wrist, and what are their typical causes?
The main types of wrist fractures include:
Distal radius fracture: Most common type, typically resulting from a fall on an outstretched arm.
Scaphoid fracture: Occurs from a fall onto an outstretched hand with the wrist extended and abducted, and is the second-most common type.
Anterior dislocation of the lunate: Caused by a fall on a dorsiflexed wrist, which can lead to carpal tunnel syndrome due to compression of the median nerve.
How does paralysis of the serratus anterior muscle affect the scapula, and what nerve is involved?
Paralysis of the serratus anterior muscle results in a condition known as winged scapula, where the medial border of the scapula protrudes posteriorly. This occurs due to a lesion of the long thoracic nerve, which innervates the serratus anterior. As a result, the scapula is unable to stay firmly against the thoracic wall during arm movements.
What movements are allowed by the wrist joint, and which muscles are involved in these movements?
The wrist joint, an ellipsoid type of synovial joint, allows the following movements:
Flexion: Flexor carpi radialis and flexor carpi ulnaris.
Extension: Extensor carpi radialis longus and brevis, extensor carpi ulnaris.
Abduction: Abductor pollicis longus, flexor carpi radialis, extensor carpi radialis longus and brevis.
Adduction: Flexor and extensor carpi ulnaris.
These movements are essential for hand positioning and manipulation.
What are the components of a synovial joint, and how do they contribute to joint stability and movement?
A synovial joint consists of:
Articular surfaces covered by hyaline cartilage: Reduces friction and absorbs shock.
Joint cavity filled with synovial fluid: Lubricates the joint.
Fibrous capsule: Surrounds the joint, providing structural support.
Synovial membrane: Lines the capsule and secretes synovial fluid.
Ligaments: Intrinsic and extrinsic ligaments provide additional stability by limiting excessive movements.
These components work together to facilitate smooth movement while maintaining joint stability.
