Axilla and Brachial Plexus Anatomy

The axilla is the armpit and contains important structures like arteries, veins, and nerves (brachial plexus).

The brachial plexus is a network of nerves that supply the arm, forearm, and hand.

The breast is primarily composed of mammary glands, subcutaneous fat, and connective tissue.

Breast size can change due to various factors including pregnancy, age, and disease.

Mammary glands are modified sweat glands that produce milk.

The breast extends from the 2nd to 6th ribs and across horizontally from the sternum to the anterior axillary line.

Muscles connecting the arm to the torso, including muscles involved in moving the arm.

Muscles that support the back and allow movement of the upper body.

Small, glandular units within the breast, each draining its own lactiferous duct.

Tubing that carries milk from the lobules to the nipple.

A dilated part of a lactiferous duct where milk collects before reaching the nipple.

Connects mammary glands to the surrounding skin.

The pigmented, circular area surrounding the nipple.

Lymph nodes located in the armpit that receive most lymph drainage (75%).

Breast cancer can spread through lymphatics, veins, and direct invasion.

Fat deposition and branching of lactiferous ducts occur in breasts at puberty.

Smaller breasts due to reduced fat and glandular atrophy after menopause.

Rudimentary breast glands similar in male and pre-pubertal female breasts.

The axilla is the armpit, a space between the arm and the chest wall.

The axilla is shaped like an irregular pyramid with four sides, an inlet, and a floor.

The inlet of the axilla is formed by the first rib, clavicle, coracoid process, and scapula.

The floor of the axilla is made up of fascia and a dome of skin.

The pectoralis minor muscle pulls the tip of the shoulder down and is innervated by the medial pectoral nerves.

The clavicular head of the pectoralis major muscle is responsible for flexing a fully extended arm.

The sternocostal head of the pectoralis major muscle extends a flexed arm. This means it brings the arm back down from a flexed or bent position.

The pectoralis major muscle is innervated by the medial and lateral pectoral nerves. This means these nerves carry signals to the muscle to make it contract.

The teres major muscle functions to extend (straighten) and medially rotate (turn inward) the arm.

The latissmus dorsi muscle is responsible for adducting (pulling towards the body), extending (straightening), and medially rotating (turning inward) the arm.

The serratus anterior muscle protracts (pulls forward) and rotates the scapula (shoulder blade).

When the long thoracic nerve (C5-7) is injured, it can cause paralysis of the serratus anterior muscle, resulting in a condition called winged scapula.

A condition where the medial border of the scapula (shoulder blade) moves away from the thoracic wall due to paralysis of the serratus anterior muscle caused by injury to the long thoracic nerve.

The axilla contains vital structures like blood vessels (axillary artery and vein), nerves (brachial plexus), and lymph nodes.

The axillary artery begins at the inferior margin of rib 1 and extends to the inferior margin of the teres major muscle.

The axillary artery is divided into three parts by the pectoralis minor muscle.

The axillary artery branches into several arteries that supply the shoulder and chest, including the superior thoracic, thoraco-acromial, lateral thoracic, subscapular, anterior circumflex, and posterior circumflex arteries.

The brachial plexus originates from the anterior rami of spinal nerves C5-C8 and T1.

The brachial plexus is organized into roots, trunks, divisions, cords, and terminal branches.

An injury to the brachial plexus can affect both muscle movement (paralysis) and sensation (anaesthesia) in the upper limb.

The lateral cord of the brachial plexus gives rise to the lateral pectoral nerve, lateral root of the median nerve, and musculocutaneous nerve.

The medial cord of the brachial plexus gives rise to the medial pectoral nerve, medial cutaneous nerve of the arm, and medial cutaneous nerve of the forearm.

The posterior cord of the brachial plexus gives rise to the upper subscapular nerve, lower subscapular nerve, thoracodorsal nerve, axillary nerve, and radial nerve.

The cutaneous (skin) innervation of the upper limb is provided by various branches of the brachial plexus that extend to specific regions.

Injuries to the brachial plexus can cause a variety of symptoms, including pain, numbness, weakness, and paralysis, depending on the specific nerves affected.

The space between the breast and the deep pectoral fascia, also known as a bursa.

They connect the mammary glands to the dermis, helping support the breast's shape.

They carry milk from the lobules of glandular tissue within the breast to the nipple.

The circular pigmented area surrounding the nipple of the breast.

A dilated portion of a lactiferous duct where milk collects before reaching the nipple.

Most (75%) of the lymph from the breast drains to the axillary lymph nodes. Some drains to parasternal lymph nodes, and a small amount to the abdominal lymph nodes.

During pregnancy, estrogen and progesterone stimulate breast tissue proliferation. Breasts increase in size and prepare for lactation.

An injury to the lower part of the brachial plexus (C8-T1 roots) causing hand paralysis, claw hand, and wasted hand muscles.

An injury to the upper part of the brachial plexus (C5-C6), causing a characteristic 'waiter's tip' position of the arm.

The muscles that help stabilize the shoulder joint are: supraspinatus, infraspinatus, teres minor, and subscapularis.

The deltoid muscle abducts the arm beyond 15 degrees, flexes and extends it.

The trapezius elevates, retracts, depresses, and rotates the scapula.

Injury to the long thoracic nerve (C5-C7) causes paralysis of the serratus anterior muscle, leading to winged scapula.

The axillary artery supplies the shoulder and chest with blood.

The brachial plexus is a network of nerves originating from C5-C8 and T1, responsible for innervating the upper limb.

The area of the humerus just below the head, where the humerus narrows and becomes more cylindrical.

The subscapularis muscle is located on the anterior surface of the scapula (shoulder blade) and helps rotate the arm medially.

The teres major muscle is located on the posterior surface of the scapula and helps extend and medially rotate the arm.

The Quadrangular space is a passageway in the posterior shoulder, allowing for the passage of the axillary nerve and posterior circumflex humeral artery.

The Triangular space is another passageway in the posterior shoulder, allowing for the passage of the circumflex scapular artery.

The Triangular interval is a passageway located between the teres major, long head of the triceps, and humerus, allowing for the radial nerve and profunda brachii artery to pass.

The axillary artery is divided into three parts by the pectoralis minor muscle.

A network of nerves originating from the spinal cord and providing innervation to the arm, forearm, and hand.

The brachial plexus is formed by the anterior rami of spinal nerves C5-C8 and T1.

The cords of the brachial plexus are named after their position relative to the axillary artery: lateral, medial, and posterior.

The lateral cord provides innervation to muscles of the anterior compartment of the arm as well as the skin on the lateral side of the forearm.

The medial cord provides innervation to the pectoralis major and minor muscles, as well as to the skin on the medial aspect of the arm and forearm.

The posterior cord provides innervation to muscles of the posterior compartment of the arm and forearm, as well as to the skin on the posterior surface of the arm, forearm, and hand.

The terminal branches of the brachial plexus are the nerves that directly innervate muscles and skin in the upper limb.

The space between the breast and the deep pectoral fascia, also known as a bursa.

These ligaments connect the mammary glands to the dermis, providing support for the breast's shape and structure.

The prominence of the breast where lactiferous ducts open.

The axilla is bordered by the clavicle, scapula, ribs, and humerus.

The axilla contains vital structures like blood vessels (axillary artery and vein), nerves (brachial plexus), and lymph nodes.

The pectoralis minor muscle pulls the tip of the shoulder down and helps stabilize the scapula.

The pectoralis major muscle flexes, adducts, and medially rotates the arm.

Modified sweat glands present in both sexes, responsible for milk production in females during lactation.

Most lymph from the breast drains to the axillary lymph nodes (75%), with a smaller amount draining to the parasternal nodes and a minimal amount to the abdominal nodes.

Composed mainly of mammary glands, subcutaneous fat, and connective tissue, with size and shape determined by these components.

The muscles that help stabilize the shoulder joint: supraspinatus, infraspinatus, teres minor, and subscapularis.

The deltoid muscle abducts the arm beyond 15 degrees, flexes and extends it.

The trapezius elevates, retracts, depresses, and rotates the scapula.

Injury to the long thoracic nerve (C5-C7) causes paralysis of the serratus anterior muscle, leading to winged scapula.

The axillary artery supplies the shoulder and chest with blood.

A network of nerves originating from the spinal cord and providing innervation to the arm, forearm, and hand.

Injury to the long thoracic nerve leads to paralysis of the serratus anterior muscle, causing winged scapula.

The lower edge of the subscapularis muscle, located on the anterior side of the scapula. This location is significant as it helps define boundaries in the axilla, a crucial space for nerves and blood vessels.

The constricted region of the humerus just below the head. It is a common site for fractures due to its narrowness, also important for understanding anatomical boundaries.

The upper edge of the teres major muscle, positioned on the posterior shoulder. It serves as a boundary for the axilla and helps define anatomical spaces.

The outer edge of the long head of the triceps brachii muscle, located on the posterior shoulder. It serves as a boundary for anatomical spaces in the posterior shoulder region.

The inner edge of the long head of the triceps brachii, located on the posterior shoulder. It helps define key spaces and boundaries in the axilla.

The upper edge of the teres minor muscle, located on the posterior shoulder. It helps define boundaries in the axilla.

The outer edge of the long head of the triceps brachii, located on the posterior shoulder. It serves as a boundary for important structures in the shoulder.

The main body of the humerus, the long bone connecting the shoulder to the elbow, providing structural support and surface for muscle attachments.

The quadrangular space, located in the posterior shoulder, allows the passage of the axillary nerve and posterior circumflex humeral artery. These structures are crucial for shoulder function and sensation.

The triangular space, located in the posterior shoulder, allows the passage of the circumflex scapular artery, which helps supply blood to the scapula.

The triangular interval, a space formed by muscles in the posterior shoulder, provides a passage for the radial nerve and profunda brachii artery, crucial for arm and forearm function.

The axilla, the armpit, houses five groups of lymph nodes: anterior/pectoral, posterior/subscapular, lateral/humeral, central, and apical. These nodes play a significant role in filtering lymph fluid and fighting infections.

The brachial plexus, a network of nerves innervating the upper limb, ends with five terminal branches: the musculocutaneous, median, ulnar, radial, and axillary nerves. These nerves provide motor and sensory function to different parts of the arm, forearm, and hand.