Mammary Gland

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MAMMARY  GLAND

  • The breasts are a pair of modified sweat glands, without a distinct capsule.
  • Present in both males & females.

In males - Rudimentary.

In Females - Well developed after puberty, serves for lactation.

LOCATION :-

  • Superficial fascia of pectoral region.

SHAPE :-

  • Hemispherical / conical / pendulous.

PARTS :-

  • Base, Apex & Tail

Base -

Extent-

  • Vertically from 2nd to 6th rib in mid-clavicular line.
  • Horizontally from lateral border of sternum to mid-axillary line along the 4th rib.

Mammary Bed-

  • Base of the gland rests on the following structures..
  • Pectoralis major
  • Serratus anterior
  • External oblique aponeurosis

Retro-mammary Space-

  • Intervenes between the base of gland & pectoral fascia.
  • Contains loose connective tissue.
  • Allows the breast to move freely over the pectoralis major.

Apex - It shows nipple & areola.

Nipple-

  • It is a conical projection on the breast at the level of 4th intercostal space.
  • It is pierced by 15-20 lactiferous ducts.
  • It contains circular & longitudinal smooth muscles.
  • Skin over the nipple is devoid of hair & subcutaneous fat.

Areola-

  • It is a pigmented circular area of skin around the base of nipple.
  • Outer margin contains modified sebaceous glands, which enlarge during pregnancy & lactation known as tubercles of Montgomery.
  • Skin over the areola is devoid of hair & subcutaneous fat.

Tail -

  • Upper & outer quadrant of the gland sends a tail-like projection into the axilla through foramen of Langer.

STRUCTURE :-

  • Parenchyma of the gland is divided into 15-20 lobes.
  • Each lobe is further divided into number of lobules, which radiate from apex to base of the gland.
  • Parenchyma is made up of 3 components..
    • Glandular tissue
    • Fibrous tissue
    • Fatty tissue

Glandular Tissue -

  • It consists of tubulo-alveolar glands arranged in radiating manner in lobes & lobules.


The glands begin as clusters of alveoli (secretory)

Alveoli open into terminal ducts (Intralobular ducts)

Terminal ducts unite to form segmental ducts (Interlobular ducts)

Segmental ducts unite to form larger Lactiferous ducts

  • Lactiferous ducts are 15-20 in number, arranged in radiating manner & open at the summit of the nipple.
  • Beneath the areola each lactiferous duct dilates to form lactiferous sinus, which acts as reservoir of milk during lactation.

Fibrous Tissue -

  • Forms number of fibrous septa known as suspensory ligaments of Cooper.
  • They anchor the parenchyma to the overlying skin & underlying pectoral fascia.

Fatty Tissue -

  • It makes the organ rounded in contour.
  • Glandular tissue is embedded in the interlobar fatty tissue.
  • It is absent beneath the areola & nipple.



STRUCTURAL  CHANGES :-

  • Structure of the mammary gland changes with age, pregnancy & lactation.

From Birth to Pre-pubertal Life -

  • Presence of lactiferous ducts without alveoli.

At Puberty -

  • Ducts undergo branching under oestrogen effect.
  • Peripheral branches form solid masses of cells (precursors of alveoli) under progesterone effect.

In Pregnancy -

  • Alveoli increase in number per lobule.
  • Enlarged secretory alveoli are formed, under the effect of placental oestrogen & progesterone.
  • Milk secreted in later part of pregnancy Is known as colostrum.
  • Maternal oestrogen & foetal prolactin cause secretion of fat-free fluid from the breasts of neonates, known as witch’s milk.

During Lactation -

  • Alveolar epithelium becomes columnar in lactation.
  • Alveolar cells possess 2 types of secretory vacuoles.
  • Protein vacuoles, which are secreted in merocrine manner.
  • Lipid vacuoles, which are secreted in apocrine manner.
  • Prolactin & growth hormone maintain the lactation.
  • Oxytocin helps in milk ejection.

After Lactation -

  • The alveoli shrink & the remaining milk is absorbed.
  • Glandular tissue returns to the resting condition.

ARTERIAL  SUPPLY :-

Lateral Thoracic Artery -

  • It is a branch of 2nd part of axillary artery.
  • It provides lateral mammary branches to supply lateral part of the gland.

Superior Thoracic Artery -

  • It is a branch of 1st part of axillary artery.
  • It supplies upper part of the gland.

Perforating Branches -

  • They are branches of internal thoracic artery given off in the 2nd-4th intercostal spaces.
  • They form medial mammary branches & supply medial part of the gland.

2nd – 4th Intercostal Arteries -

  • They supply the deep surface of the gland through their lateral branches.

VENOUS  DRAINAGE :-

  • Veins form a plexus beneath the areola called circulus venosus.
  • From the plexus veins radiate & drain into the axillary, Internal thoracic & intercostal veins.

Communications -

  • They may communicate with intracranial sagittal & transverse sinuses via internal vertebral venous plexus of Batson.
  • They also establish venous communications with clavicle, humerus & cervical vertebrae.





LYMPHATIC  DRAINAGE :-

  • Lymphatics draining the gland are arranged in 2 sets.. Deep & Superficial.

Deep Set -

  • Lymph vessels form plexuses within the gland & join with subareolar plexus of Sappey.
  • They drain the parenchyma, areola & nipple.
  • 75% of lymph from deep set drains into axillary nodes by following the lateral thoracic artery.
  • 20% of lymph drains into parasternal nodes by following the perforating branches of internal thoracic artery.
  • 5% of lymph drains into posterior intercostal nodes following the posterior intercostal vessels.

Superficial Set -

  • They drain the skin over the gland excluding areola & nipple.
  • From upper outer quadrant, lymph vessels drain into supra-clavicular group of deep cervical lymph nodes.
  • From upper inner quadrant, lymph vessels drain into parasternal group of lymph nodes.
  • From lower outer quadrant, lymph vessels drain into axillary group of lymph nodes.
  • From lower inner quadrant, lymph vessels drain into sub-diaphragmatic & hepatic lymph nodes, after piercing the upper part of linea alba.
  • They communicate with those of rectus sheath & form sub-peritoneal plexus.

NERVE  SUPPLY :-

  • Nerves are derived from anterior & lateral cutaneous branches of 4th-6th intercostal nerves.
  • They carry sensory fibres, which supply skin over the gland.
  • They also convey sympathetic fibres, which are primarily vaso-motor.

DEVELOPMENT :-

  • In 7th week of intra-uterine life 2 ectodermal milk ridges appear from axillae to inguinal regions.
  • They persist only in the pectoral regions & give rise to breasts.
  • Epithelial lining of the ducts & alveoli is derived from surface ectoderm.
  • Fibro-fatty stroma is derived from mesoderm.
  • Post pubertal growth of female breast is known as thelarche.

APPLIED  ASPECTS :-

Breast Cancer (Malignancy) :-

  • Carcinoma of breasts usually arises from the larger ductal epithelium.

Symptoms & Signs -

  • A hard & fixed breast lump.
  • Gland is fixed to pectoralis major- when cancer cells invade the retro-mammary space.
  • Fibrosis of ligaments of Cooper, Retraction & Dimpling of the overlying skin- when malignant cells Infiltrate along the suspensory ligaments of Cooper.
  • Fibrosis of the ducts & Retraction of the nipple- when cancer cells grow along the lactiferous ducts.
  • Peau d’orange skin-
    • Obstruction of the cutaneous lymphatics by cancer cells leads to oedema of the skin around the hair follicles.
    • It gives an appearance of retracted hair follicles resembling the skin of an orange.
Metastatic spread of cancer cells leads to..
  • Obstructive jaundice- due to enlargement of hepatic nodes around the bile duct.
  • Krukenberg’s tumour- secondary deposits on the surface ovary form when cancer cells from sub-peritoneal plexus drop into the peritoneal cavity, undergo trans-coelomic migration.
  • Spread to the bones by retrograde venous flow.

Examination -

  • Axillary lymph nodes of both sides should be examined for enlargements.
  • As cutaneous lymphatics communicate across the middle line causing unilateral disease becomes bilateral.

Diagnosis - can be made by..

  • Fine Needle Aspiration Cytology (FNAC)
  • Mammography
  • Ultrasonography

Treatment -

  • Surgical incisions over the gland should be made in a radial direction to avoid cutting through the lactiferous ducts, as they are arranged radially from the nipple.
  • Breast lump up to 4cm- treated by tumour excision, removal of axillary lymph nodes & radiotherapy.
  • Larger lumps- treated by modified radical mastectomy followed by radiotherapy & chemotherapy.

Prognosis -

  • Prognosis of female breast carcinoma depends on the stage of metastasis.
  • Prognosis of breast carcinoma of male is worse than that of female, as male breasts are richly drained by lymphatics.

Intraductal Papilloma :-

  • It is a non-malignant condition of the breast.
  • Symptom- Blood-stained nipple discharge without a palpable mass.
  • Treated by- Excision of the affected duct in radial manner.

Fibro-adenoma :-

  • It is a painless benign lesion of the breast.
  • A soft & mobile breast lump arises from distal smaller ducts.

Lactocele / Galactocele :-

  • It is a retention cyst resulting from lactiferous duct occlusion.
  • Usually seen on cessation of lactation as a painless benign breast lump.
  • It may lead to breast abscess.

Congenital Anomalies :-

  • Amastia - Bilateral agenesis of mammary glands
  • Polymastia- accessory breasts along the milk ridge.
  • Polythelia - Supernumerary nipples over the breast.
  • Gynaecomastia-
    • Abnormal, bilateral hypertrophy of male breasts.
    • Observed in Klinefelter’s syndrome.





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