Breast Anatomy: Structure, Breast Ducts, Functions, Embryology, Blood Supply, Mammography

Surgery Encyclopedia: Breast Anatomy: Structure, Breast Ducts, Functions, Embryology, Blood Supply, Mammography

Introduction to Breast Anatomy #

BREAST ANATOMY
BREAST ANATOMY

Breasts are hemispherical projections found attached by a dense layer of connected tissue fascia to the anterior muscles, pectoralis major, and serratus.

Each breast has a pigmented nipple containing lactiferous ducts from which the milk is sucked out.

The nipple is surrounded by the areola which appears rough because of the presence of sebum (a waxy matter which lubricates hairs and skin in mammals) producing sebaceous glands.

Cooper’s ligaments (also known as suspensory ligaments) connect the breast to the skin and fascia. These ligaments get loosen with aging and by heavy exercise.

Each breast has a mammary gland which is a modified sudoriferous gland that produces milk, containing 15-20 lobes separated by adipose tissue.

Lobes are further composed of smaller compartments called lobules which are also further composed of alveoli (milk-secreting glands). The milk produced in alveoli passes from mammary ducts which form slightly expanded regions, lactiferous sinuses that store milk. The milk from these lactiferous sinuses is carried out to the exterior by lactiferous ducts. (1)

Functions – Mammary glands has the functions of synthesis, secretion, and ejection of milk

Hormones – Milk production is stimulated by Prolactin from the anterior pituitary which gets contributions from other hormones, Progesterone, and Estrogen. While milk ejection is stimulated by the action of oxytocin in response to the suckling of milk from the nipple by the infant.

LACTATING BREAST

Points to Remember on Breast Anatomy #

  • It is a modified sweat gland
  • It has Glandular lobules which are drained by 15-20 lactiferous ducts
  • Extent of the breast is from the 2nd – 6th rib.
  • It has 4 quadrants. The majority of cancers develop in the upper outer quadrant as there is large amount of glandular tissue in upper outer quadrant.
  • The Retromammary space is a loose areolar tissue that separates the breast from the pectoralis major muscle. The retromammary space is often the site of breast implantation due to its location away from key nerves and structures that support the breast.
  • Cause of fixation of malignant breast lesion to chest wall: Tumors may grow through retromammary space and subsequently invade deep fascia & pectoralis major muscle. This leads to fixation of malignant breast lesion to the chest wall.
  • Cause of irregular dimpling or puckering of skin and retraction of the nipple: More than 80% of breast cancers show productive fibrosis that involves the epithelial and stromal tissues. With the growth of cancer and invasion of the surrounding breast tissues, the accompanying desmoplastic response entraps and shortens Cooper’s suspensory ligaments to produce a characteristic skin and nipple retraction.
  • Applied Clinical Anatomy: Skin dimpling, Nipple retraction, Peau d’orange, Lymphoedema of ipsilateral upper limb post-mastectomy
  • Localised edema (peau d’orange) develops when drainage of lymph fluid from the skin is disrupted
Puckering, Dimpling and Peau D Orange
A) Puckering/ Skin Retraction B) Peau d’ Orange appearance

Parts of Breast #

Nipple – Nipple is a small projection of breast present in the 4th intercoastal space. It allows suckling of milk upon stimulation. Nipples lack sweat glands, adipose tissues, and hair follicles.

Sulcus – The skin fold at the rising edge and intersection of nipple.

Areola – It is the dark pigmented area surrounding the nipple on the surface of breast, rich in modified sweat glands. As of nipple, it is also lack adipose tissue and hair follicles.

Breast Structure and parts

Montgomery glands – The modified sweat glands representing an intermediate stage between sweat and true mammary glands. It secretes a lubricating substance which act during breast feeding.

Montgomery glands are modified sweat glands that which has a function to lubricate breast during breastfeeding.

Lobes and ducts – Each breast have a mammary gland containing 15-20 lobes and a lactiferous duct drains each out of them, which expands a little forming the lactiferous sinuses which opens into the nipple. Milk is stored in lactiferous duct and sucked out through nipples.

Muscles and ligaments – The breast itself do not contain any muscles but it has suspensory ligaments called Cooper’s ligaments that supports the breast by connecting it to outer skin and inner fascial tissue. It has the major role of keeping the breast in shape.

Fatty stroma –The mammary glands are filled with high amount of adipose tissue but at the same time the nipple and areola are devoid of it. (3)

Functions of Breast #

Milk production and secretion – The primary and most important function of the breast is to secrete milk, which helps in the breastfeeding of infants.

Maintaining body posture – Though the weight of the breast is not much but still it plays a role in deciding the posture. When a woman stands upright the mass of her breasts generates a flexion torque about her thoracic spine due to the action of gravity. This flexion torque results in a change of posture over time and restricts the movement of the vertebral column and upper limbs in women having large breasts. These women more frequently complain about the torso and musculoskeletal pain and show more kyphosis and decreased shoulder motion and scapular retractor endurance strength. (4)

Maintaining body symmetry – The size of the breast is negatively linked to the total asymmetry of the body indicating that the larger the breast more symmetry it possesses.

Respiratory infection – Breasts play an important function in respiratory infection i.e., the bigger the breasts are the more frequent chances of infections it has.

Inter-female rivalry – Breasts among women are seen as interfemale rivalry organs particularly for individuals unreliably signaling their high quality.

Attracting sexual partners – Bigger breasts are more attractive to men while at the same time women with sagging breasts are found to be unattractive to men.

Physical activeness – Weight, and unsteadiness which raises various forms of pains become a limiting factor for women with large breasts to take active participation in vigorous-intensity physical activities. (5)

Embryology of Breast #

4th week of gestation – Mammary ridge or the milk line starts developing on the ventral surface of the human embryo

5th week of gestation – The primary bud starts proliferating

7th week of gestation – The primary bud begins downward growth as a solid diverticulum

8th week of gestation – At the end of the 8th week the rudimentary breasts are formed

10th week of gestation – Branching of primary buds starts from the 10th week

12th week of gestation – Small lumina develops within buds that will later form lactiferous ducts.

5th month of gestation – Nipple surrounding areola is formed by the 5th month of gestation (6)

Arterial supply of breast #

The derma of the breasts gets the supply of their blood from the intersecting blood vessels underlying it. These minute blood vessels in turn connects to arterioles that delivers to the parenchyma of the breasts. Following arteries serve the breasts in supplying blood: –

  • Thoracoacrimal artery
  • Internal mammary perforations (2nd to 5th)
  • Lateral thoracic artery
  • Thoracodorsal artery
  • Terminal branches of the intercoastal perforators (3rd to 8th) (7)

Venous drainage of breast #

Mammary glands are drained by veins that follow arteries and are renamed according to them. These veins form non-connecting venous regions surrounding the nipple and are characterized into following parts: –

Superficial veins drain into internal thoracic and superficial veins of the lower neck

Deep veins drain into internal thoracic, axillary, and posterior intercoastal veins.

Lymphatic drainage of breast #

Principal lymph node – The lymphatic outflow of the breast is mostly directed to the lymph nodes listed below.

  • Axillary nodes
  • Internal mammary nodes

Axillary nodes are found in the axillary pad of the adipose tissue and are classified into following groups: –

(i)         Anterior group – This collection of lymph nodes drains the outside quadrants of the breast and is located on the lower border of the pectoralis minor along the lateral thoracic arteries.

(ii)        Posterior group – This group is found at the lower border of the subscapularis on the axilla’s posterior wall. It drains the breast’s bottom outer quadrant.

(iii)       Lateral group – This collection of lymph nodes, located next to the humerus on the axilla’s lateral wall, drains a little amount of lymph from the breast.

(iv)       Central group – This group, which is located near the base of the axilla, receives lymph from the anterior, posterior, and lateral lymph nodes.

(v)        Apical group – These are located deep in the axilla’s apex and gets lymph from all of the lymph nodes listed above.

Internal mammary nodes – These lymph nodes drain the medial quadrants of the breast and are located along the sternum’s lateral border, enclosing the internal mammary artery. Some pass to the other side and drain to the opposite set of parasternal nodes; this is how ipsilateral breast metastasis spreads to the other side and becomes bilateral.

The primary group of lymph nodes that drain lymph from the breasts is the axillary group of lymph nodes. The axillary group drains nearly 75% to 80% of the lymph from the breasts. The anterior group is the primary drainage site among these. The remaining 20 to 25% of lymph from the breasts is drained by the internal mammary group.

Cutaneous nerves supply of breast #

A lot of research works are already present in PubMed literature about the innervation of the breast but still, there are some knowledge gaps that to work out. While studying from already present research these conclusions could be made mentioned below.

The breast has an interconnected network of nerves fund majority underneath the nipple and areola; this is the reason that makes them very sensitive to touch and plays a very important role in the nipple’s sensation and women’s sexuality. The main innervating branches of nerves include: –

(i)         Anterior cutaneous branches

(ii)        Lateral cutaneous branches

(iii)       Supraclavicular nerves

It is advised to surgeons and medical professionals that to not to dissect the inferolateral quadrant of the breast. Improper handling of these nerves may lead to loss of nipple and areolar sensation.

These branches mentioned above comes from the 2nd, 3rd,4th, 5th, and 6th intercostal nerves.4th intercostal nerve is the major intercoastal nerve to supply the nipple and areola complex. The nerves sensation is carried to the spine from the T4 spinal nerve dermatome. (8), (9), (10), (11)

Breast anatomy on mammography #

Mammography is the study of the breast using X-Ray imaging and is performed to screen the breast cancer in women that show no symptoms or signs.

Film screen mammography and digital mammography (also known as the full-field digital mammography) are two of the biophysical techniques used for this purpose.

These techniques have shown significant promise in terms of providing quantitative image-derived measures that relate to breast cancer risks.

The X-Rays emitting from the equipment travels through the breasts and show the inside view of the body. It detects the malfunctions such as abnormal masses, abnormal areas, and calcium deposits which could later have the chance to get transformed into cancerous masses.

Women generally more than 40 years of age show better results with the test. (12)

Difference between female and male breast anatomy #

Biologically everyone is breasted no matter what their sexes are. Before puberty, both the sexes have the same size of breast, but the difference is created when they reach puberty. At puberty, the male testosterone hormone predominates and stops the breasts from growing.

Males’ breasts also differ from the female breasts because they lack the lobules and alveoli that are responsible for the production of milk.  Men’s breasts are usually less protruding and smaller as compared to women’s breasts but in a disorder named gynecomastia men also develop bigger breasts.

(13) (14) (15)

PropertiesFemaleMale
Milk production and secretionSecrete milkDoes not secrete milk
Role in maintaining body postureBreasts because of its bigger size generate flexion torque about the thoracic spineSmaller breast size does not create much pressure and thus no flexion torques generation is seen
Respiratory infectionMore frequent respiratory infectionLess frequent respiratory infection
Maintaining body symmetryPlay an important role in body symmetry. Bigger the breast size, the more symmetry is observedNot much role
AlveoliPresent and is the major gland that has the role in producing milkAbsent or underdeveloped
NippleProjected outside that helps in easing the suckling of milk by the babyPresent and does not secrete milk though physically similar and lack sweat glands, adipose tissues, and hair follicles
Lactiferous ductPresent and are highly specialized that stores milk before the milk is sucked outAbsent or underdeveloped
Fatty stromaHigh amount of adipose tissueComparatively less
Physical activenessBecause of heavy weight and size restricts women in physical activities and is associated in chest pains and bad posturesUsually low weight that does not interfere in body’s movement

Acknowledgment

Article Written By: Jaud Ansari BSc, MSc Biophysics

Article Medically Reviewed By: Dr Sandeep Moolchandani MS, MHA, DrNB

References

  • Principles of anatomy & Physiology, Fifteenth edition, Gerard J. Tortora/Bryan Derrickson
  • Image attribution – User:Mikael Häggström, Public domain, via Wikimedia Commons https://upload.wikimedia.org/wikipedia/commons/6/60/Imframammary_fold.jpg
  • https://www.ncbi.nlm.nih.gov/books/NBK547666/
  • McGhee DE, Steele JR. Breast Biomechanics: What Do We Really Know? Physiology (Bethesda). 2020 Mar 1;35(2):144-156. doi: 10.1152/physiol.00024.2019. PMID: 32027563.
  • Kościński K, Makarewicz R, Bartoszewicz Z. Stereotypical and Actual Associations of Breast Size with Mating-Relevant Traits. Arch Sex Behav. 2020 Apr;49(3):821-836. doi: 10.1007/s10508-019-1464-z. Epub 2019 Sep 27. PMID: 31562583; PMCID: PMC7058577.
  • Allen Gabriel, MD, FACS Professor, Department of Plastic Surgery, Loma Linda University School of Medicine (https://emedicine.medscape.com/article/1275146-overview#a3)
  • Rivard AB, Galarza-Paez L, Peterson DC. Anatomy, Thorax, Breast. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519575/
  • Schulz S, Zeiderman MR, Gunn JS, Riccio CA, Chowdhry S, Brooks R, Choo JH, Wilhelmi BJ. Safe Plastic Surgery of the Breast II: Saving Nipple Sensation. Eplasty. 2017 Nov 21;17:e33. PMID: 29213346; PMCID: PMC5700452
  • Rivard AB, Galarza-Paez L, Peterson DC. Anatomy, Thorax, Breast. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519575/
  • Zucca-Matthes G, Urban C, Vallejo A. Anatomy of the nipple and breast ducts. Gland Surg. 2016 Feb;5(1):32-6. doi: 10.3978/j.issn.2227-684X.2015.05.10. PMID: 26855906; PMCID: PMC4716863.
  • Zucca-Matthes G, Urban C, Vallejo A. Anatomy of the nipple and breast ducts. Gland Surg. 2016 Feb;5(1):32-6. doi: 10.3978/j.issn.2227-684X.2015.05.10. PMID: 26855906; PMCID: PMC4716863.
  • Gastounioti A, Hsieh MK, Cohen E, Pantalone L, Conant EF, Kontos D. Incorporating Breast Anatomy in Computational Phenotyping of Mammographic Parenchymal Patterns for Breast Cancer Risk Estimation. Sci Rep. 2018 Nov 30;8(1):17489. doi: 10.1038/s41598-018-35929-9. PMID: 30504841; PMCID: PMC6269457.
  • https://www.healthline.com/health/mens-health/why-do-men-have-nipples#early-development
  • https://www.medicinenet.com/breast_anatomy/article.htm
  • https://my.clevelandclinic.org/health/articles/8330-breast-anatomy

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