Anatomy and physiology of the breast Flashcards
What stimulates myoepithelial cells?
Oxytocin
What is the name of the centre of the breast?
The lumen
Where is milk released?
The milk duct
What stimulates alveolar cells?
Prolactin
What are the inner cells of the breast? Which are the outer cells?
Inner=alveolar
Outer=myoepithelial
What blood enters the breast? What blood exits the breast?
Enters=arterial blood (vessel at the back)
Exits= venous blood (vessel at the front)
What are the 3 phases of lactation?
Lactogenesis I
Lactogenesis II
Lactogenesis III
What occurs is lactogenesis I?
Initiation of milk secretion
What happens in lactogenesis II?
Production of colostrum & transitional milk
What happens in lactogenesis III?
The development of milk & maintenance of established lactation
What controls Lactogenesis I & II?
The endocrine system hormones
What controls lactogenesis III?
Autocrine (local) control
When does lactogenesis I start and finish?
Mid pregnancy- Day 2 postnatally
What signifies the start of lactogenesis I?
Milk components are first seen in breasts and colostrum can be expressed in pregnancy
What can be found in maternal plasma from mid pregnancy during lactogenesis I?
Alpha lactalbumin (protein) that regulates production on lactose
What initiates lactogenesis II?
Birth
When does lactogenesis II start and finish?
Starts day 2
Finished day 8
What swaps in lactogenesis II?
Endocrine control swaps to autocrine control
During which stage of lactogenesis are there rapid cardiovascular changes?
Lactogenesis II
What is another term for lactogenesis III?
Galactopoiesis
When does lactogenesis III Begin?
8/10 days
What gets established in lactogenesis III?
Mature milk supply
In lactogenesis III what does the autocrine control allow?
Supply and demand of milk
Where is prolactin produced?
Anterior pituitary gland
What does progesterone do in the breast tissue?
Suppresses the action of prolactin
What does PIF do and where is it secreted?
Secreted by the hypothalamus and suppresses the action of prolactin
What drug surpresses lactation?
Bromocriptine
What does dopamine do?
Suppresses production of prolactin
Which drug is an agonist (encourager) of dopamine?
Bromocriptine
What drug encourages milk production?
Metoclopramide
How does metoclomapride work!
It inihibits the action of dopamine, to prevent inhibition of prolactin and increase milk supply
Which drug is an antagonist of dopamine? Which is an agonist?
Bromocriptine is an agonist
Metochlopramide is an antagonist
What three factors increase prolactin levels?
Stress, exercise, sex
What is the function of the circadian rhythm in breast feeding?
Helps with night feeds
What does nipple stimulation help with?
Release of prolactin
When does prolactin level return to baseline?
3-4 hrs after feed
Stages of the prolactin reflex?
1) Baby suckles
2) Sensory impulses pass from nipple to brain
3) Prolactin is secreted by the anterior gland and goes via the blood stream to the breasts
4) acini/lactocytes produce milk
What cells produce milk?
Lactocytes
Acini cells
When are prolactin levels highest?
At night
Why does prolactin level peak after a feed?
To produce milk for the next feed
What hormone suppresses ovulation?
Prolactin
How do receptor sites on acini cells become primed?
Prolactin receptor theory
Expulsion of placenta opens prolactin receptor sites
Prolactin binds to receptor sites (priming the sites)
What happens to unprimed prolactin receptor sites?
Prolactin receptor theory
They shut down, reducing their potential for milk production
What hormone must be present for milk synthesis?
Prolactin
What cells of the alveoli are milk producing cells?
Lactocytes
Where are Prolactin receptor sites?
On lactocyte alveolar cells
What allows prolactin in the blood to move into the lactocytes and stimulate synthesis of breast milk components?
Receptors on lactocytes
Hypothesis of feedback system of breast milk
When alveolus is full of milk
Walls stretch, altering shape of prolactin receptors
Prolactin cant bind and activate
Rate of milk synthesis slows as milk empties from alveolus
Prolactin receptors return to normal shape
Let down reflex
Oxytocin cause breasts to expel or ‘let down’ milk
What are 2 related aspects of oxytocin in the removal of milk from breast?
Let down reflex
Baby sucking role
What causes milk ducts to dilate?
Oxytocin
What hormone causes myoepithelial cells to contract?
Oxytocin
Oxytocin reflex (4 steps)
Baby suckles
Sensory impulses nipple—> brain
Oxytocin secreted by posterior pituitary gland goes via bloodstream to breasts
Myoepithelial cells contract and expel milk
Neuro-endocrine mechanism breastmilk
Hypothalamus maintaining homeostasis by releasing oxytocin
Causes of milk ejection as a Conditioned response?
Touch, smell, sound of baby
What causes milk ejection as an unconditioned response?
Nipple stimulation
Three steps of oxytocin and prolactin release from suckling to action?
Nipple stimulation by baby suckling sends sensory impulse to hypothalamus
Hypothalamus stimulates posterior pituitary to release oxytocin and anterior pituitary to release prolactin
Oxytocin stimulates milk release from breast, Prolactin stimulates milk production
What neuron pathway does nipple stimulation sensory impulse travel down to the hypothalamus?
Afferent sensory neurons
What nervous system does milk production signals occur in?
Central nervous system
What receptors in nipple are stimulated my sucking (that send signal to brain)?
Sensory proprioreceptors
FIL
Feedback inhibitor of lactation
What causes milk to be produced by prolactin?
Removal of milk from breast
What is autocrine regulator?
FIL
A protein secreted in milk that inhibits synthesis of milk constituents
Why does milk in breast inhibit production of milk constituents?
The presence of autocrine regulator protein (FIL) in milk inhibits synthesis of milk
Why does removal of milk cause production of milk constituents?
Because the autocrine regulator protein in the milk is removed to milk synthesis is no longer inhibited and prolactin can produce milk
Inhibitor of milk synthesis=?
Milk producer=?
Cause of milk secretion=?
FIL Feedback Inhibitor (autocrine regulator protein)
Prolactin
Oxytocin
Alveolus
Small sac in the mammary gland
Where is the lobe? (Breast diagram)
From where the breast starts to protrude to the base of the nipple
Montgomery tubercles location
On the areola (bumps on areola)
Lactiferous duct location?
Stringlike lines going into nipple have rounded area like balloon that is the duct
What are alveolar lactocytes surrounded by?
Myoepithelial cells
Centre of alveolus?
Lumen
What surrounds the lumen of the alveolus? (Making up the alveolar wall)
Lactocytes
How do lactocytes expel milk?
When myoepithelial cells contract they contract lactocytes
What causes glandular and ductal growth in the breast during puberty?
Oestrogen, progesterone and growth hormones
What happens to the areola in puberty?
They enlarged and darken
What causes breasts to enlarge during puberty?
Deposition of adipose tissue
When do breasts develop and when do they stop?
Every menstrual cycle until ages 35
What hormones cause breasts to develop in pregnancy?
Progesterone, Prolactin, human placental lactogen and growth hormone
When in pregnancy can collistrun be secreted?
Starting at 16-20 weeks
What causes delay in lactogenesis II?
Preterm delivery (<28 weeks)
Location of the breasts?
Anterior chest wall
Where do the breasts extend from? (Ribs)
2nd to 6th intercostal cartilage (rib)
What level is the nipple on the breast in coordinance to the ribs?
4th intercostal space
What 3 types of tissue are in the breast?
Glandular tissue, embedded fatty tissue, fibrous connective tissue
What ligaments are in the breast?
Suspensory ligaments
What are the epithelial cells of the alveoli?
Lactocytes
What two things surround lactocytes
Rich vascular supply
Myosepithelial cells
What hormones in high levels suppress milk production during pregnancy?
Oestrogen
Progesterone
What is the result of large gaps between lactocytes in the first 4 days post partum?
Enhanced passage of milk components such as immunoglobulins, lymphocytes and macrophages into the milk (properties of colostrum)
What type of cells are myoepithelial cells
Smooth muscle, contraction cells
What reflex are myoepithelial cells a part of as a result of which hormone?
Let down reflex
Oxytocin
What part of the breast is made up of 5-10 ducts and smooth muscle fibres with a rich blood supply and sensory nerve endings?
Nipple
What’s the purpose of Montgomery tubercles on the areola?
They produce secretions to lubricate and protect the areola and nipple during pregnancy and lactation also the odour of these is to direct the baby towards the breast
What does the lymph supply do in the breast?
Collects excess fluid, bacteria and cast off cell parts
Where is the lymph drainage channelled to?
Axiliary notes
What nerves are in the breast?
Branches of the 4th, 5th and 6th intercostal nerves
When are prolactin levels highest?
At night
How do Prolactin levels affect lactogenesis at night?
More feeds at night to increase production
What physiciological affect does oxytocin have?
Contraction of the uterus
Where is oxytocin secreted from
Posterior pituitary gland
