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.
What is the breast weight of a lactating woman?
600-800g.
When does lactation occur?
After birth.
What hormone causes milk production?
Prolactin.
What prevents lactation during pregnancy?
Progesterone prevents lactation. Progesterone is also a smooth muscle relaxant.
What induces prolactin secretion?
An infant suckling on the nipple - prolactin secretion is stimulated by a neuroendocrine reflex (if you cut the nerves to the nipple it prevents this reflex).
What secretes prolactin?
Anterior pituitary.
How does suckling cause prolactin secretion?
It reduces the secretion of dopamine (prolactin inhibiting factor) into the portal blood - there is also an increase of secretion (by the paraventricular nuclei) of vasoactive intestinal peptide (VIP). Both of these factors act on the lactotrophs to secrete prolactin. Prolactin then induces the production of milk.
What is the milk ejection response?
It is where suckling stimulates synthesis and secretion of oxytocin by posterior pituitary.
What does oxytocin do in the MER?
Induces contraction of myoepithelial cells of alveoli causing ejection of milk into ducts.
Can milk let down occur when a woman is not lactating?
Yes - lactating women may have a milk let down during sex. This is due to stimulation of the female reproductive tract.
How does lactation affect fertility?
Prolactin suppresses secretion of gondaotropins FSH and LH. It is thought to be via the kisspeptin neuron in the hypothalamus. Therefore, alctating women often have no or irregular menstrual cycle.
What are supernumerourry breasts/nipples?
These are women to have additional breast tissue - usually found along the line of the embryonic milk ridge. Additional nipples can occur on the breast or along the milk ridge and lactiferous ducts can exit the breast at sites outside of the nipple.
What occurs in lactogenesis stage 1?
This can occur from mid gestation to day 2 post partum. There is withdrawal of the placental steroids - estrogen and particularly progesterone. Withdrawal of these hormones will allow for the onset of lactation.
When does lactogenesis stage 1 occur?
This can occur from mid gestation to day 2 post partum.
What occurs in lactogenesis stage 2?
Large scale milk production occurs. There is an increase in alpha-lactalbumin, decrease in sodium and decrease in chloride in the milk - this is due to the tight junctions in the alveolar epithelium reducing the passage of salt between cells.
When does lactogenesis stage 2 occur?
Day 3-8 post-partum.
What is glactopoiesis?
Maintenance of established milk secretion - starts day 8 post-partum till however long it lasts for.
What is involution?
When the breasts start to decrease in size - occurs 40 days after the last feed.
What happens during the first days after delivery?
A thick milk product called colostrum is made.
What is colostrum?
A product that contains less sugar and less fat than mature milk - less energy. It contains more total protein than mature milk, it is also rich in antibodies esp. IgA.
What is colostrum responsible for?
Immune function (via secretory antibodies IgA) - to protect against mum’s surrounding environment.
What are the major components of breast milk?
- Phagocytes (90%), lymphocytes (10%), T-cells (4%).
- Small soluble signalling molecules e.g. prostaglandins, cytokines, growth factors.
- Enzymes e.g. amylase, lipase.
- Lipids - long chained polyunsaturated fatty acids and triglycerides.
- Lactose - galactose and glucose combined.
- Proteins e.g. immunoglobulins (IgA).
- Lysozyme.
- Vitamins.
- Water (85.7% of breast milk by volume).
What is the function of phagocytes, lymphocytes and T cells in breast milk?
Immunological protection.
What is the function of small soluble signalling molecules (prostaglandins, cytokines, growth factors)?
They are immunomodulators which promote leukocyte movement across the gut e.g. TGF-Beta in colostrum, epithelial growth factor (EGF) helps with gut epithelium growth.
What is the function of enzymes (lipase, amylase)?
Helps the baby to digest polysachharides and hydrolyses fat in the baby’s intestine.
What is the function of lipids?
DHA is associated with increased visual acuity and cognitive ability. Lipids are the largest source of calories for an infant.
What is the function of lactose?
It is an important energy source - it breaks down to glucose and galactose. Galactose is important for myelin synthesis. Lactose promotes growth of lactobacillus bifidus - breastfed babies have more exclusive gut microflora whilst formula fed babies have more diverse gut microflora.
What is the function of proteins i.e. immunoglobulins?
Immunoprotection.
What is the function of lactoferin?
Antibacterial - soaks up iron, and damages bacterial membrane permeability.
What is the function of lysozome?
Antibacterial - lysis of the bacterial cell wall in gram positive bacteria.
What is the function of vitamins?
Nutritional and antioxidant.
What is the function of water?
Hydration.
Does size matter with breasts and lactation?
Larger breasts have a greater capacity for milk storage but it does not reflect milk production capacity. Storage capacity may be different in the left and right breasts. Milk yield from the righy breast tends to be greater on average than from left breasts.
What are the public/personal health benefits of breast feeding for the mother?
- Spacing of offspring.
- Bonding to offspring - eye contact.
- Enhances involution of the uterus.
- Appears to protect against development of type 2 diabetes mellitus.
- May protect against post-partum depression.
- Evidence that breast feeding may protect against ovarian cancer.
How does breast feeding help with spacing of offspring?
If you exclusively breastfeed for 6 months, it prolongs the duration of post-partum amenorrhea (lactational amenorrhea). This reduces the chance of getting pregnant. It can also enhance weight loss after pregnancy.
What are the public/personal benefits of breastfeeding for the baby?
- Protection against adult diabetes and obesity.
- Protection against disease.
- Protection against atopy (allergy) and asthma.
- Protection/prevention against sudden infant death syndrome (SIDS).
- Increase cognitive ability.
Describe how breastfeeding can protect against diabetes and obesity?
Breastfeed babies don’t tend to be over-fed. At 12 months of age, breastfeed babies are leaner than controls (breast feed for 9 months). Breastfeeding may put a slight protection against childhood obesity and diabetes.
Describe how breastfeeding can protect against disease?
It can help to reduce poor outcomes from infectious diseases. It prevents exposure to diarrhoea inducing pathogens. It provides protective factors e.g. antibodies. It protects against otitis media.
Describe how breastfeeding can protect against atopy?
Babies that are breastfeed are protected against developing atopic reaction (allergic). This is probably due to the baby being exposed to allergens that it has no protection against - however the transfer of IgA to the baby protects the baby from these allergens.
Describe how breastfeeding can protect against asthma?
Babies are less likely to develop asthma if they are breastfeed - 33% chance.
What diseases can be spread from mother to baby via breastfeeding?
- HIV.
2. Hepatitis B.
What is mastitis?
Infection of lactiferous lobe (breast appears red often in triangle). It is a bacterial infection, but not an indication to stop breastfeeding (not harmful to babies).
Describe alcohol transmission in breastfeeding?
Levels of alcohol are similar in milk and maternal plasma - comes across to baby. Babies do not suckle well after alcohol consumption. Alcohol may lead to feeding problems.
Describe caffeine transmission in breastfeeding?
Caffeine readily enters milk - the baby cannot process caffeine as well as adults. The baby can get a build up of caffeine in their system - excess caffeine can be associated with sleeplessness and irritability of the infant.
Describe nicotine transmission in breastfeeding?
Nicotine is found in the urine of both breast and bottle feed infants - smoking should be discouraged in women with infants.
