Lecture 19 + 20 - 2018/2017 Flashcards
What is the breast?
Mammary gland.
Wha is the breast purpose?
- Milk production - nutrition of the young.
2. Spacing of pregnancies (lactational amennorhea).
What are the mammary glands?
Modified sweat glands.
Where are the mammary glands derived from?
Tissues that is first identified in the mammary (or milk) crests that arise between the axilla (armpits) and the groin. Abnormal breast development is likely to occur along the lines of the mammary crests.
When does breast development begin?
About 6 weeks - with the formation of mammary buds.
Where does the first development of breasts take place?
The take place as a down growth of the dermis to form the primary breast bud. Secondary buds develop from the primary buds.
What do secondary breast buds form?
Lactiferous ducts - by birth 15-20 lactiferous ducts are present.
What are lactiferous ducts?
Channels that carry milk from the alveoli to the nipple.
What happens as fetal gestation progresses?
The buds develop lumens - they become canalised.
What induces canalisation?
Canalisation is induced by placental steroids - progesterone and estrogen.
What happens to the breasts at birth?
The breasts are fully developed and could potentially make milk. However, milk production requires hormonal stimulus.
What is witches milk?
This is when a baby produces a colostrum-like secretion from the breast, because they have been exposed to the placental steroids and maternal hormones at birth.
What is gynaecomastia?
Condition in which men have breasts. It can occur when they are newborns or when they’re teenagers. It is due to reduced testosterone or increased estrogen.
What are the components of the breast?
- Internal.
2. External.
What are the external structures of the breast?
- Body of the breast.
- Nipple.
- Aerola.
Describe the nipple?
Raised (usually) cylindrical pigmented structure - the nipple can be inverted. The lactiferous ducts join the skin at the nipple.
Describe the aerola?
This is a pigmented circle of tissue surrounding the nipple, it contains sebaceous glands which give a granular texture to the surface.
What are the internal structures of the breast?
- Adipose tissue.
- Ligaments.
- Lobules and lactiferous duct.
- Lactiferous sinus.
Describe the adipose tissue in the breast?
It is a major component of the pectoral fat pad - adipose tissue gives the breast its texture and much of its shape.
Describe the ligaments in the breast?
Breasts are supported by ligaments - Suspensory Ligaments of Cooper. These ligaments are affected by age, hormones in pregnancy and can become less supportive.
How many lobules does each breast have?
15-20 lobules (each of these secrete milk) that are connected to a single lactiferous duct.
Describe the lactiferous sinus?
It is a sinus that opens onto the nipple that allows extraction of milk. The lactiferous ducts run towards the nipple and expand into a lactiferous sinus (widening of duct).
When do the breasts develop?
Puberty - until puberty the breast ducts don’t have alveoli. Alveoli start to develop during puberty - particularly under the influence of estrogen.
What dominates the resting (non-pregnant and non-lactating) breast?
Duct system and fat - not alveoli.
What happens to the breast during the menstrual cycle?
Estrogen and progesterone will promote growth of alveolar buds (successive cycles cause increased growth) - there can be noticeable pre-menstrual increase in the volume of the breast and tenderness.
What happens to the breasts during pregnancy?
They increase in size - particularly the alveolar tissue.
What hormones influence the growth of the breast during pregnancy?
- Estrogen - essential for breast growth (stimulates cell growth).
- Progesterone - induces side branching of ducts.
- Prolactin - necessary for alveolar development but also stimulates casein and alpha-lactalbumin mRNAs (lactose production).
- Growth hormone - important in some species.
- Insulin and cortisol - stimulates alveolar epithelial cell division.
What do these hormones cause?
Expansion of the alveoli and ductile system - the ducts grow, branch and bud.
What is the breast weight of a non-pregnant woman?
200g.
What is the breast weight of a near term pregnant woman?
400-600g.