Mammary glands and lactation Flashcards
What is mammogenesis?
How mammary glands are formed
What is isometric growth?
growth that occurs at the same rate for all tissues so that the shape is consistent
When does isometric growth occur for mammary glands?
From birth to puberty
What is allometric growth?
growth that is faster than the growth rate of other tissues
When is the fastest stage of mammary gland proliferation?
From conception to parturition
What is milk secretion?
synthesis of milk by the alveolar cell and its transfer from the alveolar cell into the alveolar lamina.
What two things does progesterone block?
Parturition and lactation
What is the function of oestrogen (in terms of lactation)?
High levels can prevent lactation
What does cortisol induce growth of?
Rough endoplasmic reticulum and golgi apparatus
Why do we need golgi apparatus and RER in the epithelial cells?
allows prolactin to initiate lactation
What is the main function of prolactin?
Removes the progesterone block so that parturition can be initiated
What is galactopoiesis?
The maintenance of milk production
What two factors play a role in milk production?
Both hormonal and local
Where is prolactin produced from?
The anterior pituitary gland
What is prolactin inhibited by?
dopamine
What does suckling do to dopamine?
It has an inhibitory effect
What hormone stimulates contraction of myoepithelial cells?
Oxytocin
What is the milk ejection reflex?
A neuroendocrine reflex that allows milk to be let down/released by causing the posterior lobe of the pituitary to release oxytocin
What does activation of the sympathetic nervous system do to milk let-down?
Inhibits it, e.g if they are anxious/ there is painful external stimuli
What does FIL do?
reduces milk synthesis by reducing milk flow
What is the composition of colostrum in comparison to regular milk?
Contains more fat, protein, minerals and vitamins
than regular milk and lower levels of lactose
What animals is colostrum particularly important in and why?
ruminants, foals and piglets as they cannot receive nutrients via the placenta
When is intestinal absorption of immunoglobins at its maximum
In the first 6 hours
What enzymes facilitate the production of glucose?
lactose synthase and a-lactalbumin
Where are Milk fats synthesised?
They are synthesised in the smooth ER (from precursor fatty acids and glycerol)
What does suckling inhibit the secretion of?
Dopamine,
What does progesterone stimulate the development of during pregnancy?
lobulo-alveolar development
What do high levels of oestrogen prevent during pregnancy?
Lactation
What is agalactia?
A failure to produce milk which will then lead to a failure to reproduce
How does pro-lactin increase milk secretion?
Removal of the progesterone block also removes inhibition of the prolactin receptor synthesis
Increased binding of membrane receptors means that there is increased production of milk-protein genes (synthesis of lactose)
Which hormone inhibits prolactin secretion?
Dopamine
How do insulin and growth hormone effect milk production?
They regulate the metabolism to ensure there is adequate supplies
When do FIL levels increase?
Suckling stops so milk builds up in the alveoli
this reduces milk synthesis
and eventually apoptosis of the secretory cells
autocrine effect, can be inhibited by milking
this is mammary gland involution (essential process)
What is the final stage of lactose production and what enzymes regulate it?
UDP galacatose + glucose -> Lactose
this is regulated by lactose synthase and
a-lactoalbumin (milk protein)
Where is milk fat synthesised and by what
It is synthesised in the smooth ER from precursor fatty acids and glycerol
the milk fat then moves towards the apical membrane in droplets
What acids make up the preformed fatty acids?
C16 and C18
it is synthesised from adipose stores early on in lactation
Where are the non-essential amino acids for milk proteins produced?
They are synthesised within the mammary epithelial cells
How can you use urea to assess health in cattle?
Easily diffuses into milk
* Same concentration in milk as blood
Too low – nitrogen content in feed too low so animal must catabolise muscle protein and vicer versa
high urea could also be a sign of deydration
How could acetone be used to assess cattle health
Easily diffuses into milk
* Same concentration in milk as blood
* Detected by colour reaction (Rothera’s test)
* Used for clinical investigation of ketosis
How could progesterone be used to assess health in cattle?
- Lipid-soluble steroid hormone
- Low in non-cycling animals or in follicular phase
- Higher in luteal phase or pregnancy
- Used to assess reproductive status
What do low fat levels in milk indicate?
High levels of concentrate feeding
What kind of infection would increase the SCC of a cow?
Mastitis/ mammary infection
When do FIL levels increase?
When the young stop suckling/weaning
due to increased pressure in the intramammary glands
What happens to the secretory cells after lactation stops?
They are removed by apoptosis
