DEVELOPMENTAL ANATOMY OF THE FEMALE BREAST

Dr. E. T. Agida MBBS(IB), FWACS, MPA.

Chief Consultant Obstetrician and Gynaecologist,University of Abuja Teaching Hospital.

DEVELOPMENTAL ANATOMY OF THE FEMALE BREAST

Breasts are bilateral apocrine glands whose function is principally to provide nutrition by lactation for the new born.

Embroyology

Mammary buds begin to develop during the 6th week as solid downgrowth of the epidermis into the under-lying mesenchyme

These buds are downward growths from mammary crests which are thickened strips of ectoderm extending from the axillary to the inguinal regions

Embroyology Cont’d.. Each primary bud gives rise to several

secondary mammary buds that develop into lactiferous ducts and their branches

Canalization of these buds is induced by placental sex hormones entering foetal circulation

At term, 15-20 lactiferous ducts formed

The fibrous tissue and fat develop from the surrounding mesenchyme

Embroyology Cont’d..

Mammary pits are formed during late foetal period

Nipples rise from mammary pits due to proliferation of the surrounding connective tissue of the areola after birth

The mammary gland remains underdeveloped until puberty

Female Breast at Puberty

Enlarge mainly because of development of mammary glands and the accumulation of fat

Growth of duct system occurs due to raised levels of circulating oestrogen, progesterone, prolactin, corticosteroids and growth hormone

Anatomy of the Female Breast

Body of the female breast rests on a bed that extends transversely from the lateral border of the sternum to the midaxillary line

Vertically from the 2nd-6th ribs Two thirds of the bed of the breast

are formed by the pectoris fascia overlying the pectoralis major

The other third by the fascia covering serratus anterior

Anatomy of the Female Breast Cont’d..

Small part of the breast may extend along the inferolateral edge of the pectoralis major towards the axillary fossa (axillary tail)

The mammary gland is firmly attached to the dermis of the overlying skin by the suspensory ligaments (of cooper)

Breast size and shape determined by genetic, ethnic and dietary factors

Anatomy of the Female Breast Cont’d..

Lactiferous ducts give rise to buds that form 15-20 lobules of glandular tissue, which constitute the parenchyma of the mammary gland

Each lobule drained by a lactiferous duct, which opens independently on the nipple.

Deep to the areola, each duct has a dilated portion, the lactiferous sinus, in which a small droplet of milk accumulates or remain in the nursing mother

Anatomy of the Female Breast Cont’d..

The areola contains numerous sebaceous glands, which enlarge during pregnancy and secrete an oily substance

The mammary glands are modified sweat glands; no special capsule or sheat

The rounded shape is produced by subcutaneous fat, except in pregnancy when the mammary glands enlarge and new glandular tissue forms

Secreting alveoli are arranged in grape-like clusters

Blood Supply

Arterial Supply: Medial mammary branches of

perforating branches and anterior intercostal branches of the internal thorac artery, originating from subclavian artery

Lateral thoracic and thoracoaromial arteries, branches of the axillary artery

Posterior intercostal arteries, branches of the thoracic aorta in the 2nd, 3rd and 4th intercostal spaces

Venous drainage

Mainly to the axillary vein and some to internal thoracic vein

Lymphatic Drainage

Important because of cancer metastasis From the nipple, areola and lobules of the

gland to the subareolar lymphatic plexus From the lateral breast to the axillary

lymph nodes. Some may drain directly to other axillary nodes or interpectoral, deltopectoral, subclavicular, or inferior deep cervical nodes

The medial breast quadrants drain into the parasternal lymph nodes or to the opposite breast.

Lymphatic Drainage Cont’d.. Inferior quadrants may drain to abdominal

lymph nodes (inferior phrenic lymph nodes) Skin (except the nipple and areola) drain

into the ipsilateral axillary, interior deep cervical and infraclavicular lymph nodes and also into the parasternal lymph nodes both sides

Axilary nodes Clavicular (infraclavicular and supraclavicular) lymph nodes Suclavian lymphatic trunk

Parasternal nodes bronchomediastinal lymphatic trunk

Innervation

Nerves derived from anterior and lateral cutaneous branches of the 4th-6th intercostal nerves

Abnormalities of the Breast

1. Gynaecomastia-Breast hypertrophy in males

May occur in newborn, disappears in few weeks

About two third of boys develop it in mid puberty

Pathology-drugs (e.g. DES), liver disease, supra-renal or testicular cancers, klinefelter’s syndrome.

Abnormalities of the Breast Cont’d..

2. Absence of nipple (athelia) and breast (Amastia)

May be unilateral or bilateral Failure of dev. or disappearance of

mammary crests Failure of mammary bud to form

Abnormalities of the Breast Cont’d..

3. Hypoplasia of the breast Gonadal agenesis Turner’s syndrome4. Supernumerary breasts (polymastia

and nipple (polythelia) May develop in the axilla or anywhere

along the embryonic mammary ridge (the milk line).

Thank you