Breast part 1
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Breast part 1
- 1. Anatomy and physiology of Breast By Dr.solomon 10/17/2017 Breast 1
- 2. Outline • Introduction • Embryology • Anatomy of the breast • Situation and deep relations • Structures • Blood supply • Nerve supply • Lymphatic drainage • Physiology of the breast • Some congenital anomalies of breast 10/17/2017 Breast 2
- 3. . Introduction • Studying the anatomy of breast is of great paramount for clinicians in the diagnosis and management of breast cancer • The breast is the most prominent superficial structure in the anterior chest wall • The breast is a group of large glands derived from the epidermis • They consist of glandular and supportive tissue embedded in a fatty matrix 10/17/2017 Breast 3
- 4. Embryogenesis of the Breast Milk lines • Two bands of slightly thickened ectoderm • Appeared on the ventral body wall during the fifth or sixth week of gestation, • Extending from above the axilla to below the groin • These bands represent potential mammary gland tissue • In humans, only the pectoral portion of these bands will persist 10/17/2017 Breast 4
- 5. • The glandular portion of the breast develops from the ingrowth of ectoderm which forms a primary bud • From this primary tissue bud,15 to 20 secondary buds developed into the dermis during the twelfth week • These buds, at first solid, will become canalized near term to form the lactiferous ducts • Canalization of these buds is induced by placental sex hormones entering the fetal circulation 10/17/2017 Breast 5
- 8. Functional Anatomy • The breast is composed of 15 to 20 lobes which are each composed of several lobules • Cooper’s suspensory ligaments: – Fibrous bands of connective tissue – Travel through the breast and insert perpendicularly into the dermis – provide structural support • The mature female breast extends Vertically – from second or third rib to the inframammary fold at the sixth or seventh rib 10/17/2017 Breast 8
- 9. Transversely • from the lateral border of the sternum to the anterior axillary line(midaxillary line ..moore) • It lies in investing superficial fascia derived from the dermis • The deep or posterior surface of the breast rests on the fascia of • pectoralis major (2/3), • serratus anterior • external oblique abdominal muscles, and (1/3) • the upper extent of the rectus sheath 10/17/2017 Breast 9
- 10. The retromammary bursa • Identified on the posterior aspect of the breast between – the investing fascia of the breast and – the fascia of the pectoralis major muscles • The axillary tail of Spence extends laterally across the anterior axillary fold 10/17/2017 Breast 10
- 12. • The mature breast is composed of three principal tissue types: – (1) glandular epithelium, – (2) fibrous stroma and supporting structures, and – (3) adipose tissue • composition of breast tissue varies with age • In adolescents, the predominant tissues are epithelium and stroma • In postmenopausal women, the glandular structures involute and are largely replaced by adipose tissue 10/17/2017 Breast 12
- 13. Mammary glands • form in the same manner as do sweat glands • they are often considered to be modified sweat glands • The areolar glands (of Montgomery) , appear to be transitional between sweat and lactiferous glands – They serve to lubricate the nipple during lactation Connective-tissue stroma • Formed from the mesoderm, – Form the dermis of the skin and – The superficial fascia (tela subcutanea) 10/17/2017 Breast 13
- 14. Each lobe of the breast lactiferous duct lactiferous sinus • lactiferous sinus, – lined with stratified squamous epithelium • Major ducts are lined with two layers of cuboidal cells, • Minor ducts are lined with a single layer of columnar or cuboidal cells Myoepithelial cells • ectodermal origin • reside between the epithelial cells and the basal lamina • contain myofibrils 10/17/2017 Breast 14
- 17. Nipple-Areola Complex The areola • The areola is said to be visible from the fifth month onward • contains sebaceous glands, sweat glands, and accessory glands (Montgomery’s tubercles) • Has smooth muscle bundle fibers – lie circumferentially in the dense connective tissue and – longitudinally along the major ducts, and – extend upward into the nipple • responsible for the nipple erection 10/17/2017 Breast 17
- 18. Nipple • At first, the surface of the nipple was a shallow pit • Near term or during infancy it becomes everted • proliferation of mesenchyme – Have no fat, hair, or sweat glands – The tips are fissured with the lactiferous ducts opening – composed of circularly arranged smooth muscle fibers • compress the lactiferous ducts during lactation • Note that an inverted nipple may be a developmental arrest 10/17/2017 Breast 18
- 19. • The dermal papilla at the tip of the nipple – contains numerous sensory nerve endings and Meissner’s corpuscles • This rich sensory innervation is of functional importance, – the sucking of the infant initiates – a chain of neurohumoral events – results in milk letdown 10/17/2017 Breast 19
- 20. • Girls - Breast development • Stage 1: Prepubertal • Stage 2: Breast bud stage with elevation of breast and papilla; enlargement of areola • Stage 3: Further enlargement of breast and areola; no separation of their contour • Stage 4: Areola and papilla form a secondary mound above level of breast • Stage 5: Mature stage: projection of papilla only, related to recession of areola Sexual maturity rating (Tanner staging) 10/17/2017 Breast 20
- 21. VASCULATURE OF BREAST • Arterial supply from: – (a) perforating branches of the internal mammary artery; 60% – (b) lateral branches of the posterior intercostal arteries –the 2nd, 3rd, and 4th intercostal (from thoracic aorta) – (c) branches from the axillary artery, including 30% –the highest thoracic, –lateral thoracic, and –pectoral branches of the thoraco acromial artery 10/17/2017 Breast 21
- 23. venous drainage • follow the course of the arteries, with venous drainage being toward the axilla • The three principal groups of veins are • (a) perforating branches of the internal thoracic vein • (b) perforating branches of the posterior intercostal veins, • (c) tributaries of the axillary vein • Batson’s vertebral venous plexus, • invests the vertebrae (skull to the sacrum) • provide a route for breast cancer metastases 10/17/2017 Breast 23
- 25. Innervation • Lateral cutaneous branches of the third through sixth intercostal nerves provide sensory innervation of the breast • Cutaneous branches from the cervical plexus, the anterior branches of the supraclavicular nerve • The intercostobrachial nerve is the lateral cutaneous branch of the second intercostal nerve 10/17/2017 Breast 25
- 26. Lymphatic drainage • Most lymph (>75%), drains to the axillary lymph nodes • The six axillary lymph node groups • (a) the axillary vein group (lateral) • (b) the external mammary group (anterior or pectoral group) • lower border of the pectoralis minor muscle contiguous with the lateral thoracic vessels • (c) the scapular group (posterior or subscapular) • (d) the central group • (e) the subclavicular group (apical) • (f) the interpectoral group (Rotter’s lymph nodes), 10/17/2017 Breast 26
- 29. • According to their anatomic r/n to the pectoralis minor muscle • level I lymph nodes: – lateral to or below the lower border of the pectoralis minor – include the axillary vein, external mammary, and scapular groups • level II lymph nodes: – superficial or deep to the pectoralis minor muscle – include the central and interpectoral groups • level III lymph nodes: – located medial to or above the pectoralis minor – consist of the subclavicular group 10/17/2017 Breast 29
- 31. PHYSIOLOGY OF THE BREAST Breast Development and Function • Estrogen, progesterone, and prolactin have profound trophic effects • Estrogen -initiates ductal development, • progesterone –for epithelium and lobular development • Prolactin -for lactogenesis in late pregnancy and the postpartum period • Works through Positive and negative feedback effects 10/17/2017 Breast 31
- 34. Inactive and Active Breast The inactive breast, – The epithelium is sparse and consists primarily of ductal epithelium Menstrual cycle • In the early phase - minor ducts are cordlike with small lumina • Late phase- estrogen stimulation at the time of ovulation • alveolar epithelium increases in height, • duct lumina become more prominent, and – When the hormonal stimulation decreases, • The alveolar epithelium regresses 10/17/2017 Breast 34
- 35. Pregnancy • ovarian and placental estrogens and progestin increase • The breast enlarges as the ductal and lobular epithelium proliferates, • In 1st ,2nd TM, the minor ducts branch and develop • During the 3rd trimester, – fat droplets accumulate in the alveolar epithelium and – colostrum fills the alveolar and ductal spaces • In late px, prolactin stimulates the synthesis of milk fats and proteins 10/17/2017 Breast 35
- 36. Lactation • Milk production -lactogenic action of prolactin – controlled by neural reflex arcs • Maintenance of lactation – regular stimulation of these neural reflexes • Oxytocin initiates contraction of the myoepithelial cells, – expulsion of milk into the lactiferous sinuses • Oxytocin release results from the auditory, visual, and olfactory stimuli associated with nursing 10/17/2017 Breast 36
- 37. • Senescence • Dormant milk causes increased pressure within the ducts and alveoli, which results in atrophy of the epithelium • With menopause there is a decrease in the secretion of estrogen and progesterone by the ovaries and involution of the ducts and alveoli of the breast • The surrounding fibrous connective tissue increases in density, and breast tissues are replaced by adipose tissues 10/17/2017 Breast 37
- 38. The breast at different physiologic stages. Central column contains three- dimensional depictions of microscopic structures. A.Adolescence. B.Pregnancy. C.Lactation. D.Senescence. 10/17/2017 Breast 38
- 39. Changes in rates of secretion of estrogens, progesterone, and prolactin for 8 weeks before parturition and 36 weeks thereafter. Note especially the decrease of prolactin secretion back to basal levels within a few weeks after parturition, but also the intermittent periods of marked prolactin secretion (for about 1 hour at a time) during and after periods of nursing 10/17/2017 Breast 39
- 40. Congenital Anomalies of breast • Polymastia-Accessory breasts • Polythelia- – accessory nipples may occur along the milk line when normal regression fails – occur in <1% of infants – may be associated with other abnormalities • Amastia- – Absence of the breast is rare – results from an arrest in mammary ridge development • Symmastia – – a rare anomaly recognized as webbing between the breasts across the midline 10/17/2017 Breast 40
- 41. • Poland’s syndrome – hypoplasia or complete absence of the breast, – costal cartilage and rib defects, – hypoplasia of the subcutaneous tissues of the chest wall, and – brachysyndactyly – aplasia or hypoplasia of the sternocostal portion of the pectoralis major muscle 10/17/2017 Breast 41
- 42. Thank you 10/17/2017 Breast 42
- 43. Reference 1.Schwartz’s principles of surgery,10th edition 2.Skandalakis Surgical Anatomy 3. Longman embryology 4.Guyton physiology,11th edition 5. Moore clinically oriented anatomy,7th edition 10/17/2017 Breast 43
Editor's Notes
- Fibrous strands or sheets consisting of condensations of connective tissue extend between the layer of deep fascia that covers the muscles of the anterior chest wall and the dermis. These suspensory ligaments (of Astley Cooper) are often well developed in the upper part of the breast and support the breast tissue, helping to maintain its non-ptotic form
- With the hormonal stimulation that accompanies pregnancy and lactation, the breast becomes larger and increases in volume and density, whereas with senescence, it assumes a flattened, flaccid, and more pendulous configuration with decreased volume
- Nonejected milk in the alveoli effects the cessation of milk production. Fibers forming the suspensory ligaments (of Cooper) will develop from both layers Although minor changes occur during each menstrual cycle, pregnancy and lactation bring about the ultimate development of the breasts Progesterone, prolactin, and placental lactogen are key hormones in stimulating the formation of secretory alveoli As development continues, the cells of the secretory alveoli acquire increased organelles related to protein synthesis and secretion.
- The epidermis of the nipple-areola complex is pigmented During puberty, becomes darker and the nipple assume an elevated configuration small elevations on the surface of the areola (Montgomery’s tubercles
- proliferation of mesenchyme transforms the mammary pit into a nipple The tips of the buds will gives the acini during lactation
- The second, third, and fourth anterior intercostal perforators and branches of the internal mammary artery arborize in the breast as the medial mammary arteries The lateral thoracic artery gives off branches to the serratus anterior, pectoralis major and pectoralis minor, and subscapularis muscles It also gives rise to lateral mammary branches.
- These branches exit the intercostal spaces between slips of the serratus anterior muscleCutaneous branches that arise from the cervical plexus, specifically the anterior branches of the supraclavicular nerve, supply a limited area of skin over the upper portion of the breast The intercostobrachial nerve is the lateral cutaneous branch of the second intercostal nerve and may be visualized during surgical dissection of the axillaResection of the intercostobrachial nerve causes loss of sensation over the medial aspect of the upper arm
- The sentinel lymph node is functionally the frst node in the axillary chain and anatomically is usually found in the external mammary group
- The plexus of lymph vessels in the breast arises in the interlobular connective tissue and in the walls of the lactiferous ducts and communicates with the subareolar plexus of lymph vessels
- Enlargement of the neonatal breast may be evident and a secretion, historically referred to as witch’s milk, may be produced. These transitory events occur in response to maternal hormones that cross the placenta Polythelia- accessory nipples may occur along the milk line when normal regression fails occur in <1% of infants may be associated with other abnormalities of the urinary tract (renal agenesis and cancer), abnormalities of the cardiovascular system (conduction disturbances, hypertension, congenital heart anomalies), and other conditions (pyloric stenosis, epilepsy, ear abnormalities, arthrogryposis) Inverted nipple- During infancy, a proliferation of mesenchyme transforms the mammary pit into a nipple If there is failure of a pit to elevate above skin level This congenital malformation occurs in 4% of infants
- Breast hypoplasia also may be iatrogenically induced before puberty by trauma, infection, or radiation therapy. Turner’s syndrome (ovarian agenesis and dysgenesis) and Fleischer’s syndrome (displacement of the nipples and bilateral renal hypoplasia) may have polymastia as a component Accessory axillary breast tissue is uncommon and usually is bilateral