Anatomy III: Blood and the Cardiovascular and Respiratory Systems Presentation

Mammary Glands Overview

Breasts in Males

Breast are present in males and females, but normally they develop completely in women S In men: . They consist of only a few small ducts_or epithelial cords. Normally the glandular system does not develop . The fat present in male breasts is not different from that of subcutaneous tissue elsewhere · Breast are mostly an accentuation of the contour of the pectoralis major muscles · Nipple is in the 4th intercostal space, lateral to the midclavicular line

Breasts in Men: Topographic Lines

In athletic men, the contour of the pectoralis major muscles is apparent and we can see two topographic lines: · Between both breast: intermammary cleft overlying the sternum . Lateral border: forming the anterior axillary fold

Anterior axillary fold Intermammary cleft

Breasts in Women: Structure and Limits

In women they are accessory to reproduction

Sternum Axillary process of breast Axilla Lobules of fat Nipple Areola Serratus anterior · Superior limit: flattened superior surface that shows no sharp demarcation from the anterior surface of the thoracic wall · Lateral and inferior limits: submammary sulcus · They consist of glandular and supporting fibrous tissue embedded within a fatty matrix · At the matrix we can also find the vessels, lymphatic and nerves

Breasts in Women: Fatty Matrix and Movement

Sternum Axillary process of breast Axilla Lobules of fat Nipple Areola Serratus anterior The quantity of fatty matrix that surrounds the glandular tissue will determine the size in the non-lactating breasts

• Bed of the breast: formed by pectoralis major fascia and serratus anterior fascia - Lateral limits: from the lateral border of sternum to the midaxillary line - Vertical limits: from the 2nd to 6th ribs
• Retromammary space: between the breast and the pectoral fascia there is a potential space with loose subcutaneous tissue - It allows the breast some degree of movement on the pectoral fascia

Breasts in Women: Ligaments and Axillary Process

Axillary process Suspensory ligaments -2nd rib Pectoral fascia Fat lobule Retromammary space (bursa) Areola Subcutaneous tissue Pectoralis minor

• Axillary process or tail of the breast: extension of the mammary gland along the infero-lateral edge of the pectoralis major toward the axillary fossa
• Suspensory ligaments of Cooper: skin ligaments that firmly attach the mammary gland to the dermis of the overlying skin - They are well developed in the superior part of the gland - They help to support the lobes and lobules of the mammary gland

Changes in Breast Size

· The breast size and shape is determined by genetic, ethnic, and dietary factors, and it changes during the lifetime: · During female puberty (8-15 years), the breasts enlarge thanks to two mechanisms: - Glandular development - Increased fat deposition · The areolae and nipples also enlarge

• During menstrual period the glandular tissue enlarges slightly thanks to the LH and FSH hormones
• During pregnancy the mammary glands enlarge and new glandular tissue is formed

Mammary Glands and Breast Structure

Mammary Glands Characteristics

Mammary glands: Nipple · They are modified sweat glands · They do not have capsule or sheath · The milk-secreting alveoli are arranged in clusters · Mammary glands enlarge when FSH and LH hormones are released, for example during the menstrual period

Breast Structure: Lobules and Ducts

· Lobules: they constitute the parenchyma of the mammary gland. Each lobule is drained by a lactiferous duct . Lactiferous ducts: all of them converge to open independently at the areola - The final portion of the ducts is the lactiferous sinus, in which the milk can accumulate as drops . As the neonate begins to suckle, compression of the areola and lactiferous sinus beneath it expresses the accumulated droplets - This encourages the neonate to continue nursing . This stimulates the hormonal let-down reflex

Suspensory ligaments 2nd rib Pectoral fascia Fat lobule Retromammary space (bursa) Areola Subcutaneous tissue Lactiferous sinus Pectoralis minor Pectoralis major Nipple 4th intercostal space Lobules of mammary gland (resting) Lactiferous ducts 6th rib Lobules of mammary gland (lactating) Check the lactiferous sinus and ducts, and the change in mammary lobules during lactancy

Areolae Characteristics

Areolae: · They contain numerous sebaceous glands · They enlarge during pregnancy · They secrete an oily substance that provides a protective lubricant for the areola and nipple, which are very susceptible to abrasion and irritation at the beginning of the nursing

Areolae Pigmentation and Glands

Areolae: · The areola usually darkens during pregnancy and retains the darkened pigmentation thereafter · The areola is normally dotted with the papular openings of the areolar glands, that are sebaceous glands in the skin of the areola

Nipples Composition and Function

Nipples: · The nipples have no fat, hair, or sweat glands · The nipples are composed mostly of circularly arranged smooth muscle fibers with two functions: - Compress the lactiferous ducts during lactation - Erect the nipples in response to stimulation, as when a baby begins to suckle

Nipples Level and Anomalies

Nipples: · In young nulliparous women its level is the 4th intercostal space, 10 cm from the axillary midline, but in adults it is not a reliable guide to find this space · Sometimes one or both nipples are inverted or retracted. This minor congenital anomaly may make breast feeding difficult

Nipple retraction

Vascularization and Innervation

Arterial Supply to the Breast

Blood is supplied by the arteries highlighted in red: · Subclavian artery: - Internal thoracic artery: · Anterior intercostal branches · Medial mammary branches

• Axillary artery: - Lateral thoracic arteries - Thoraco-acromial arteries
• Thoracic aorta: - 2nd, 3rd 4th posterior intercostal arteries

Subclavian a. Thoraco-acromial trunk Axillary a. Internal thoracic a. and its perforating branches Brachial a. Lateral thoracic a. Lateral mammary branches Medial mammary branches Lateral mammary branches of lateral cutaneous branches of posterior intercostal aa.

Venous Drainage of the Breast

· The breast veins will go to: - Axillary vein - Internal thoracic vein

• The venous pattern over the breasts is often visible through the skin, especially during pregnancy

Internal jugular v. Subclavian v. Cephalic v. Axillary v. Lateral thoracic v. Internal thoracic v. and its perforating branches Lateral mammary vv. Medial mammary v.

Lymphatics of the Breast and Cancer Metastasis

Very important due to its role in the metastasis of cancer cells Lymph passes from the nipple, areola, and lobules of the gland to the subareolar lymphatic plexus . ~ 75% of the lymph of this plexus drains to the axillary lymph nodes, specially the lateral quadrants and the lymph of the skin · ~ 25% drains to the parasternal lymph nodes or to the opposite breast, specially the medial quadrants

Lymphatic Drainage Pathways

· From the axillary nodes lymph will go to the: - Clavicular lymph nodes and later to the: · Subclavian lymphatic trunk, which receives also lymph from the arm · From the parasternal nodes enter the bronchomediastinal lymphatic trunks, which also drain lymph from the thoracic viscera

• Both trunks can drain: - Into the jugular trunk, that will end at the thoracic duct (left) or right lymphatic duct (right) - Or open independently into the venous angles

*Central nodes *Apical nodes Clavicular (supraclavicular and infraclavicular) nodes Internal jugular vein Right jugular lymphatic trunk Right lymphatic duct Subclavian vein Right brachiocephalic vein *Humeral nodes Right bronchomediastinal lymphatic trunk *Subscapular nodes Right subclavian lymphatic trunk *Pectoral nodes *Axillary lymph nodes

Nerves of the Breast

. Anterior and lateral cutaneous branches of the 4th, 5th, 6th intercostal nerves . They pass through the pectoral fascia anterior to the pectoralis major to achieve the subcutaneus tissue and skin of the breast

• They have: - Sensory fibers from the breast skin - Sympathetic fibers to the blood vessels and smooth muscle of the skin and nipple

Bibliography

Anatomy References

. Moore Clinically oriented anatomy 8th edition / Moore, Keith L. Published 2018 . Moore Essential Cllinical anatomy 6th edition. Published 2019 · Gray's Anatomy for students / Drake, Richard L. 4th Edition Published 2019 · Color atlas of anatomy 7h edition, Rohen, Yokochi · Manual de embriología y anatomía general. V Smith Agreda · Anatomía: estructura y morfología del cuerpo humano, 4ª Edición, Lippert