Pectoral Region Anatomy Quiz

Pectoral Region

• The pectoral region is located on the anterior chest wall
• It comprises four muscles that move the pectoral girdle: pectoralis major, pectoralis minor, subclavius, and serratus anterior

Pectoralis Major

• The largest and superior muscle of the anterior chest wall
• A thick, fan-shaped muscle beneath the breast tissue
• Forms the anterior wall of the axilla
• Has clavicular and sternocostal heads
• Its inferior border forms the anterior axillary fold
• Works together with the deltoid

Pectoralis Minor

• Lies in the anterior chest wall, mostly covered by the pectoralis major
• Triangular in shape
• Its base is formed by fleshy slips attached to the 3rd-5th ribs near their coastal cartilages
• Apex connects to the coracoid process of the scapula
• This muscle is a useful anatomical and surgical landmark for axillary structures, like the axillary artery
• Creates a passage for vessels

Pectoralis Minor in Relation to Vessels and Nerves

• Diagrams show the muscle's location relative to vessels and nerves in the axillary region

Subclavius

• Almost horizontally positioned in anatomical position
• A small, triangular muscle between the first rib and clavicle
• Stabilizes the clavicle and protects the subclavian vessels and brachial plexus
• Helps prevent clavicle dislocation at sternoclavicular joint

Serratus Anterior

• Named for its "saw-toothed" appearance
• A fan-shaped muscle
• Originates on the superolateral surfaces of the first to eighth ribs
• Inserts along the anterior surface of the medial border of the scapula, including the inferior angle
• Holds the scapula against the thoracic wall during movements like push-ups

Pectoral Muscles

• Detailed descriptions of proximal and distal attachments, innervation, and main actions of each pectoral muscle (pectoralis major, pectoralis minor, subclavius, and serratus anterior)
• Includes specific nerves like medial pectoral, nerve to subclavius and long thoracic nerve

The Breasts

• The most prominent superficial structure in the anterior thoracic wall
• Composed of glandular, supportive fibrous tissue, embedded in a fatty matrix, with blood vessels, lymphatics, and nerves.
• Well-developed only in females
• The nipple is the most prominent part of the breast

The Mammary Glands

• Located in the subcutaneous tissue overlying the pectoralis major and minor muscles
• Accessory to reproduction in women
• Rudimentary and functionless in men, with only a few ducts or cords.
• The fat in male breasts is similar to subcutaneous tissue elsewhere. In females the glandular system rarely fails to develop
• The glandular tissue within the female breasts increases in volume following puberty.

The Female Breasts

• Roughly circular shape, resting on the sternum, extending from the lateral border of sternum to midaxillary line
• Vertically runs from the second to sixth ribs, including the axillary tail of Spence (axillary process)
• Minor portion extends along the inferolateral edge of the breast

Extent of the Breast

• 2/3 of the breast rests on deep pectoral fascia overlying the pectoralis major
• 1/3 rests on the fascia covering the serratus anterior muscle
• The space between the breast and pectoral fascia is the retromammary space

Retromammary Space

• A loose subcutaneous tissue/potential space
• Contains a small amount of fat
• Allows breast movement over the pectoral fascia

Structure of breast tissue (layers)

• Describes the layers within the breast, including the epidermis, dermis, Cooper's ligaments, breast ducts, and retromammary space and other components of the breast

Suspensory Ligaments of Cooper

• Dense fibrous connective tissue bands supporting the lobes and lobules of the mammary gland.
• Well-developed in the superior part of the gland
• Help support the lobes and lobules during puberty in females

The Glandular Tissue of the Breast

• Lactiferous ducts give rise to 15-20 lobules of mammary gland parenchyma
• Each lobule drains into a lactiferous duct
• These ducts converge towards the nipple (like spokes on a wheel)
• Deep to the nipple, the ducts enlarge (in lactiferous sinuses)

Areolae

• Contains numerous sebaceous glands that enlarge during pregnancy
• Secrete an oily substance lubricating the areola and nipple

Nipples

• Conical/cylindrical prominences in the centre of the areola
• Lack fat, hair, and sweat glands.
• Fissured tips that contain opening of lactiferous ducts
• Mostly composed of smooth muscle that compresses the ducts during lactation

Mammary Glands

• Modified sweat glands, without a capsule
• Breast contour primarily composed of fat, except during pregnancy when glandular tissue develops
• Milk-secreting alveoli form clusters resembling grapes
• Breast size and composition may vary depending on factors like menstrual cycle or pregnancy

Blood Supply of Breasts

• Arterial supply: internal thoracic, lateral thoracic, thoracoacromial, and posterior intercostal arteries
• Venous return: axillary, internal thoracic, and intercostal veins

Lymphatic Drainage of Breasts

• Very important due to metastasis
• Lymph from nipples, areola, and lobules gathers in a subareolar plexus
• Most lymph (75%) drains from the lateral quadrants through axillary nodes to pectoral nodes
• Some lymph drains directly into the deltopectoral/supraclavicular/interpectoral/inferior deep nodes

Clinical Anatomy of Breasts

• Breast quadrants
• Carcinoma (breast cancer)
• Mastectomy
• Gynecomastia
• Polymastia, polythelia, and amastia
• Mammography

Mammogram Types

• Images demonstrating fatty, scattered fibroglandular, heterogeneously dense, and extremely dense breast tissue

Mammogram Examples

• Images showing normal, benign cyst, cancer, and calcification in the breasts