What is the breast?
- Modified apocrine sweat gland.
- Part of the reproductive system: responds to sexual stimulation and to feed babies.
How do breasts develop?
- Breast buds appear in both sexes in 6th - 9th months of foetal life.
- At puberty, female breasts develop under influence of oestrogen and progesterone.
- Final maturation during 1st pregnancy: mammary glands branch out and expand in response to progesterone and prolactin.
- Regression following menopause.
Where are breasts located?
- Overlie pectoralis major muscles on left and right sides.
- From 2nd-6th ribs.
- From sternal edge to anterior axillary line.
What are breasts supported by?
Cooper’s suspensory ligaments
What is breast tissue made up of?
- Mostly of adipose tissue (supports glandular structures)
- Mammary glands
- 15-20 lobes encased in a network of myoepithelial cells (contract and squeeze down on glands to excrete milk)
- milk drained towards nipple via lactiferous ducts
- expelled through nipple pores
What are the functions of areolae?
- Contain areolar glands which secrete lipoid fluid - moisturises nipple during breastfeeding.
- Darkened areolae provide target for baby to aim for.
Describe the blood supply to the breast.
- Internal mammary arteries (derived from internal thoracic artery) - predominant blood supply.
- External mammary arteries (lateral thoracic and thoracoaromial) and posterior intercostal arteries - further blood supply.
- Axillary vein - venous drainage of breast.
What is lactation?
Process where milk is made and ejected from the mammary glands inside the female breasts.
How is lactation activated?
- Baby starts to suckle - activates nipple mechanoreceptors - signalling up spinal cord to hypothalamus.
- Hypothalamus releases:
i) Activatory signals to oxytocin neurons in posterior pituitary - oxytocin production.
ii) Inhibitory signals to PIH (prolactin inhibitory hormone) in anterior pituitary - prolactin production.
- Cascade stimulated by the sound of any babies’ cry.
What are the effects of prolactin and oxytocin?
- Prolactin: stimulates mammary gland to produce milk.
- Oxytocin: stimulates myoepithelial cells surrounding glands.
What is accessory breast tissue?
- Relatively common congenital condition: abnormal accessory breast tissue is seen in addition of normal breast tissue.
- Can present as a mass anywhere along the course of the embryologic mammary streak (axilla to inguinal region).
What is Poland syndrome?
Rare birth defect characterised by:
- underdevelopment/absence of chest muscle (pectoralis) on 1 side of the body
- webbing of the fingers (cutaneous syndactyly) of ipsilateral hand
What is the most common cancer in women in the UK?
- Breast cancer
- 1/8 women
- > 40,000 cases/year
- > 10,000 deaths/year
Which factors increase the risk of breast cancer?
- woman
- age
- family history
- personal history of breast cancer
- genetics
- alcohol
- obesity
- radiation
- high socioeconomic class
Which factors decrease the risk of breast cancer?
- 1st pregnancy before age 30
- breast feeding
- exercise
- healthy organic diet?