Pregnancy and Parturition Flashcards
What do high levels of progesterone during pregnancy inhibit?
inhibits contraction of the muscle cells which prevents premature expulsion of the foetus
What can an increase concentration of oestrogen do?
Increases the number of calcium channels/ receptors for oxytocin
Stimulates glandular cells in the cervix and vagina to secrete watery mucus which then softens the mucous plug
What is the main role of the placenta?
The allantois functions as a depot for excretory products
It also has the function of transport of metabolic substances
What is the function of placental lactogen?
It is a peptide hormone closely related to growth hormone that stimulates growth of the alveoli in mammary glands during pregnancy
What is the function of relaxin?
It is produced in both the placenta and ovaries, secreted throughout pregnancy and prevents uterine contractions alongside progesterone
What is the definition of pregnancy?
Pregnancy is the carrying and supporting of a developing embryo until it can survive in the outside world
What can placental lactogen also be called?
chorionic somatomammotropin
What produces progesterone during pregnancy?
Mainly the corpus luteum, however its role varies between species and in some the placenta will take over
What do high levels of progesterone block?
They inhibit contraction of muscle cells, which blocks premature expulsion of the fetus
What does foetal stress (lack of space, and high metabolic requirements) cause in the mother?
ACTH released from the foetal pituitary which stimulates the release of cortisol from the adrenal glands
What does cortisol do in a mother with foetal stress?
Synthesises enzymes that converts progesterone into oestradiol
What is the effect of oestrogen in a mother with foetal stress?
The oestrogen synthesises myofilaments in uterine smooth muscle (which increases the force of contraction) and increases the number of gap junctions (increases the number of action potentials/ increased depolarisation)
What do high oestrogen concentrations do in general during parturition?
Increases the number of calcium channels and uterine receptors for oxytocin
And stimulates glandular cells in the cervix and vagina to secrete a watery mucous which softens the mucous plug
What is the function of prostaglandin f2 alpha?
Stimulates luteolysis and contributes to the removal of the progesterone block
What is stage one of parturition?
Preparation of the reproductive tract and foetus for delivery
What is stage two of parturition?
Delivery of the foetus
What is stage three of parturition?
Expulsion of foetal membranes
Where does relaxin come from during stage one of parturition?
either from the corpus luteum or the placenta
What is the difference in foetus delivery between monotocous species and polytocous species?
In monotocous species stage 2 involves expulsion of the foetus but not the membranes
However in polytocous species stage two and three are inseparable because the foetus’s follow each other and the membranes are also expelled during this process
What ruptures during stage 2 (expulsion of the foetus)
The chorioallantois which causes the release of ‘urine-like’ allantoic fluid from the vulva
What causes the expulsion of foetal membranes?
The endometrium secretes pulses of PGF2 alpha which together with oxytocin causes the myometrial contractions to persist- the membranes are then expelled and are often eaten by the mother
What occurs during involution of the uterus?
The continued contraction of the uterus causes the uterus to reduce in size, the smooth muscle cells also decrease in size and the glands in the endometrium are then degraded
What are some substances that can diffuse freely across the epithelial barrier?
Lipid soluble substances such as CO2 or O2
Steroid hormones
What are some substances that have to be actively transported across the epithelial barrier
Glucose, amino acids, Calcium
What is another name for placental lactogen?
chorionic somatomammotropin
In what animals does foetal repositioning need to occur?
In foals and puppies (ventral to dorsal position)
What occurs during stage 2 (delivery of the foetus)
Abdominal wall contracts
Moves the foetus towards the pelvic inlet
contractions increase as the foetus moves through the pelvic canal
Oxytocin assists with the myometrial contractions
What occurs as structures begin appearing at the vulvic cleft?
Amnion traverses the vagina and appears at the vulva as a ‘water bag’
amnion is then expelled
contractions are maximal when head appears
rest period for mother may commence afterwards
How are the foetal membranes expulled in stage 3?
large pulses of pgf2 alpha, along with oxytocin helps myometrial contractions to perist
this disrupts the physical contact between the foetal membranes and the endometrium
What is the name of the organ that allows the embryo to take oxygen and nutrients from the mother?
The placenta
What are some behavioural changes related to stage 1 of labour?
restlessness, nesting activity, decrease in body temperature,
