Anatomy Class Quiz on Clavicle and Body Regions

The axilla, also known as the armpit, is a crucial region where nerves and blood vessels from the neck connect to the upper limb. It is a vital passageway for these structures.

The axilla is located between the upper arm and the chest wall, forming a triangular space.

The axilla is bordered by the following:

1. Apex: Where the first rib, clavicle, and scapula meet.
2. Base: The skin of the armpit.
3. Anterior Wall: Pectoralis major and minor muscles.
4. Posterior Wall: Scapula and latissimus dorsi muscles.
5. Medial Wall: Ribs and intercostal muscles.
6. Lateral Wall: Humerus bone.

The axilla's primary function is to allow the passage of vital structures, including nerves and vessels, from the neck to the upper limb.

The apex of the axilla is the narrowest part, formed by the convergence of the first rib, clavicle, and scapula.

The base of the axilla is the widest part, formed by the skin of the armpit.

The axilla contains various structures, including nerves (brachial plexus), blood vessels (axillary artery and vein), lymph nodes, and fat.

Knowledge of the axilla's anatomy is important for understanding the spread of breast cancer, as the lymph nodes within are often involved in the disease process.

The humerus is the largest bone in the upper limb. It connects the shoulder to the elbow.

The head of the humerus is a ball-shaped structure that articulates with the glenoid cavity of the scapula, forming the glenohumeral joint.

The anatomical neck is a groove separating the head of the humerus from the greater and lesser tubercles.

The greater tubercle is the most lateral part of the proximal end of the humerus, and it provides attachment points for three muscles: supraspinatus, infraspinatus, and teres minor.

The lesser tubercle projects anteriorly and is located on the medial side of the humerus, providing attachment for the subscapularis muscle.

The intertubercular groove, also known as the bicipital groove, is a depression between the greater and lesser tubercles that serves as a passageway for the tendon of the biceps brachii muscle.

The surgical neck is the narrow part of the humerus located distal to the tubercles. This is a common site for fractures, especially in falls.

The shaft of the humerus is the long, cylindrical part of the bone between the proximal and distal ends. It provides structural support and serves as an attachment point for various muscles.

The clavicle is one of the most commonly fractured bones in children, often at the junction of its middle and lateral thirds. This fracture can cause the shoulder to drop as the medial fragment is pulled upwards by the sternocleidomastoid muscle, while the lateral fragment is unable to be supported by the weakened trapezius muscle.

The clavicle is the first long bone to ossify, undergoing intramembranous ossification starting during the 5th and 6th embryonic weeks. The process begins with two ossification centers that fuse together in the shaft of the clavicle.

While the majority of the clavicle undergoes intramembranous ossification, the ends of the clavicle later transition to endochondral ossification.

A secondary ossification center forms at the sternal end of the clavicle, developing as a scale-like epiphysis that fuses with the shaft between 18 and 25 years of age. This fusion process is completed between 25 and 31 years of age, making it the last epiphysis of long bones to fuse.

The clavicle is the only bone in the body that ossifies completely through intramembranous ossification, except for the sternal end, which undergoes endochondral ossification.

The coracobrachialis is a muscle that helps flex and adduct (move toward the midline) the arm. It also prevents the shoulder joint from dislocating.

The triceps brachii is the primary extensor of the forearm, responsible for straightening the elbow. It has three heads: long, lateral, and medial, all contributing to its extension function.

The long head of the triceps brachii originates from below the glenoid cavity of the scapula. This allows it to help stabilize the shoulder joint, especially during abduction (moving the arm away from the body).

The anconeus muscle is located on the back side of the elbow, and it assists the triceps in extending the forearm. It also helps stabilize the elbow joint and possibly assists in subtle movements of the ulna during pronation (rotating the palm downward).

The brachial plexus is a network of nerves originating from the spinal cord. It supplies all the muscles and sensory structures of the upper limb, from the shoulder to the hand.

The glenoid cavity, located on the lateral border of the scapula, is a shallow socket that articulates with the head of the humerus, forming the glenohumeral joint.

The coracoid process, a beak-like projection on the scapula, lies superior to the glenoid cavity.

The thin medial border of the scapula runs parallel to the spinous processes of the thoracic vertebrae, explaining its name.

The lateral border of the scapula runs superolaterally towards the apex of the axilla, giving rise to its name.

The thickest part of the scapula where the broadened head is located.

The thin, shortest border of the scapula.

This joint, also known as the scapulothoracic articulation, allows for a considerable range of movement of the scapula on the thoracic wall.

The suprascapular nerve arises from the superior trunk of the brachial plexus, supplying the muscles responsible for rotating and stabilizing the shoulder joint.

The long thoracic nerve originates from the brachial plexus, specifically from roots C5, C6, and C7. It runs along the side of the chest and innervates the serratus anterior muscle, which helps protract the scapula.

The lateral pectoral nerve branches from the lateral cord of the brachial plexus and innervates the pectoralis major muscle, which helps lower and adduct the arm.

The musculocutaneous nerve originates from the lateral cord of the brachial plexus and innervates muscles in the anterior compartment of the arm. It also provides sensory innervation to the lateral forearm.

The medial cutanous nerve of the arm arises from the medial cord of the brachial plexus and provides sensory innervation to the medial aspect of the arm.

The medial cutanous nerve of the forearm arises from the medial cord of the brachial plexus and provides sensory innervation to the medial aspect of the forearm.

The ulnar nerve originates from the medial cord of the brachial plexus and innervates muscles in the forearm and hand. It controls the flexor carpi ulnaris muscle, the medial part of the flexor digitorum profoundus muscle, and muscles in the hand.

The medial root of the median nerve originates from the medial cord of the brachial plexus and joins the lateral root to form the median nerve. It supplies muscles in the forearm and the hand.