Placental function and endocrinology of pregnancy Flashcards
(26 cards)
what are the functions of the placenta?
replace the function of adult:
- lungs - delivery of gases
- gut - delivery of nutrients
- kidney - excrete waste
- liver - store energy
- endocrine - placental derived hormones
- protective - toxic substances
Describe the overall pattern of placental and foetal growth
Most placental growth in 1st half of pregnancy
Most foetal growth in last trimester
Placental efficienct must increase with gestation to support foetal growth
How is placental efficiency increased with gestation?
increased uterine and umbilical blood flow
What factors influence the passive diffusion of substanes across the placenta?
blood flow
structure - area for exchange
morphology - tissue barriers against exchange
electrical gradient
conc gradient
Describe the link between placental morphology and efficiency
Describe active transport of nutrients across the placenta
amino acids and glucose
specific carrier molecules required
requires energy
What do placental hormones do?
stimulate ovaria/uterine function
maintain pregnancy
modulate foetal growth
assist in parturition
stimulate mammary function
What is the source and function of progestogens in pregnancy?
Produced by CL and placenta
Stimulated by LH, prolactin and oestrogens
Function:
- stimulate histotroph production (uterine milk proteins)
- suppress myometrial contractility
- stimulate mammary gland development
In which species does the placenta ‘takeover’ progesterone production?
Cow
Ewe
Mare
Where are placental oestrogens produced?
fetal cotyledons - trophoblast cells
What is the function of oestrogens in pregnancy?
stimulate placental growth
increase uterine blood flow
stimulate myometrial growth
preparation for parturition
stimulate mammary development
Where is prolactin produced?
lactotrophs of anterior pituitary gland and placenta
stimulated by ostradiol
inhibited by dopamine
what is the function of prolactin in pregnancy?
Stimulates progesterone production from the CL
Induces lobuloalveolar growth (secrete milk) and lactogenesis in the mammary gland
Stimulates maternal behaviour
What is the source of relaxin?
Produced by CL (sow)
and placenta (rabbit, mare, dog, cats)
Relaxin-like factor in cattle (equivalent)
What is the action of relaxin in pregnancy?
Softening of connective tissue enabling growth of fetus
Relaxation of pelvic ligaments
Parturition (stimulation by PGF)
Used to diagnose pregnancy in dogs and cats
Where is placental lactogen produced?
by binucleate cells
released into maternal and foetal circulation
What is the function of placental lactogen?
modulates foetal metabolism
stimulates mammary gland development
What placental hormones are produced by binucleate cells?
Placental lactogen
Pregnancy specific protein B (PSPB)
Pregnancy associated glycoprotein (PAG)
PSPB and PAG can be used for pregnancy diagnosis in cattle
Why do you see low levels of progestogens in the blood in animals where the placenta takes over production?
Placenta produces local progestogens
Label the hormonal profile of the pregnant mare
What is the function ofeCG in mares?
eCG = equine chorionic gonadotrophin
Produced from endometrial cups
Has FSH and LH-like activity:
- increases progesterone from primary CL
- induces formation of accessory CL
What is the main progestogen in mares?
5-alpha-pregnane
How are equine unique oestrogens made?
fetus produces androgens e.g., dehydroandrosterone (DHA)
androgens converted to oestrogens by placenta
When is placental ‘takeover’ in the cow?
150 days
