Control of lactation Flashcards
When is colostrum produced?
secretion accumulated at the end of last pregnancy and secretion formed during first 24 h after parturition.
What does colostrum contain?
Contains more proteins, fat, minerals and vitamins than regular milk. However lactose concentration is lower.
Proteins: transfer of IgG, IgM, IgA from blood to milk.
What is the function of colostrum?
Supplies the newborn with immunoprotection.
Very important in equidae and bovidae.
Why is colostrum slightly less important in dogs, cats and primates?
This immunoprotection is o also provided by blood exchange through the placenta
What does normal milk contain?
¥ contains mostly fat, protein, carbohydrate and water
What is the osmolality of milk?
Milk has the same osmolarity as blood: 300 mosmol/l.
Lactose is the principal contributor of osmolarity.
What is the pH of milk?
Milk has a pH of 6.6-6.9 .
What traces does milk contain?
Milk contains vitamins, trace elements, hormones, ions (Na+, K+, Cl-, HCO3-, Ca2+, Mg2+, HPO42-, SO42-, citrate
Epithelial cells in the milk alveoli have high numbers of ………………….. for what?
Mitochondria
The synthesis of fatty acids and non-essential aminoacids.
What other organelles are important in the milk alveoli epithelial cells?
RER: synthesis of secretory proteins (Golgi).
SER: synthesis of phospholipids and triglycerides.
How Do Compounds Get Into Milk?
Protein (casein) is secreted in the form of granules by exocytosis.
Lactose is secreted with protein.
Lipid (triglyceride) is secreted in the form of membrane-limited lipid droplets by incorporation into the cell membrane. May contain elements from the cytoplasm.
Water follows the lactose by osmotic pressure.
How is lipid (triglyceride) synthesised in the mammary gland?
Triglyceride is made from fatty acids in chylomicrons and LDL in the blood.
And from:
glucose (non-ruminants) or acetate and β-hydroxybutyrate (in ruminants).
Pathway of fatty acid synthesis in mammary gland are the same as in other tissues (e.g. adipose tissue).
How is lactose synthesised in the golgi body?
Glucose + ATP –> Glucose-6-P + ADP
Glucose-6-P –> glucose-1-P
Glucose-1-P +UDP –> UDP-Glucose –> UDP-Galactose
UDP-Galactose + Glucose –> Lactose + UDP
What enzyme is responsible for: UDP-Galactose + Glucose –> Lactose + UDP
Lactose synthase
What cells can be found in milk?
Milk contains leukocytes and dislodged mammary epithelial cells.
How many cells are in a healthy cows milk? Why is it good to have this many cells in the milk rather than none at all?
In healthy cows: 30,000-300,000 cells/ml.
Too low increases risk of E.coli mastitis.
During infection how much does the cell count of the milk increase? why?
During inflammation the number of cells increases 10-100 times
Due to neutrophil invasion
What causes involution of the mammary gland?
Involution can be gradual (following peak yield), initiated by loss of young or senile.
Involution involves apoptosis, phagocytes, etc.
Where is placental lactogen produced?
Do sows use placental lactogen to stimulate mammary growth?
Produced by binucleate cells of placenta.
Sows have relaxin instead of placental lactogen
What hormones stimulate lactogenesis?
Cortisol from a stressed fetus causes a fall in progesterone which releases the prolactin inhibition on the mammary gland.
Where is fetal cortisol produced? What is its effect?
Produced by fetal adrenal cortex (specialized cortical cells – not the same regions as in the adult).
Cortisol induces placental enzymes to shift synthesis away from P4 to E2:
Uterus becomes sensitive to oxytocin.
Progesterone induces storage of arachidonic acid during pregnancy, why is this significant?
Oestrogen induces phospholipase A, thus arachidonic acid is converted to PGF2α, this leads to luteolysis in species with a CL (bovidae, carnivoridae).
Softens the cervix (aided by PGE).
PGF2α induces myometrial contractions.
Oestrogen exposes myometrial oxytocin receptors.
In primates and equidae, the PGF2α causes myometrial contractions even though P4 still high.
Increase in udder volume during pregnancy follows increase in which hormones?
Oestrogen and placental lactogen
The density of prolactin receptors is regulated by what hormones?
thyroid, adrenal and ovarian hormones
