Pregnancy and Parturition

Question 1

What do high levels of progesterone during pregnancy inhibit?

Answer 1

inhibits contraction of the muscle cells which prevents premature expulsion of the foetus

Question 2

What can an increase concentration of oestrogen do?

Answer 2

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

Question 3

What is the main role of the placenta?

Answer 3

The allantois functions as a depot for excretory products
It also has the function of transport of metabolic substances

Question 4

What is the function of placental lactogen?

Answer 4

It is a peptide hormone closely related to growth hormone that stimulates growth of the alveoli in mammary glands during pregnancy

Question 5

What is the function of relaxin?

Answer 5

It is produced in both the placenta and ovaries, secreted throughout pregnancy and prevents uterine contractions alongside progesterone

Question 6

What is the definition of pregnancy?

Answer 6

Pregnancy is the carrying and supporting of a developing embryo until it can survive in the outside world

Question 7

What can placental lactogen also be called?

Answer 7

chorionic somatomammotropin

Question 8

What produces progesterone during pregnancy?

Answer 8

Mainly the corpus luteum, however its role varies between species and in some the placenta will take over

Question 9

What do high levels of progesterone block?

Answer 9

They inhibit contraction of muscle cells, which blocks premature expulsion of the fetus

Question 10

What does foetal stress (lack of space, and high metabolic requirements) cause in the mother?

Answer 10

ACTH released from the foetal pituitary which stimulates the release of cortisol from the adrenal glands

Question 11

What does cortisol do in a mother with foetal stress?

Answer 11

Synthesises enzymes that converts progesterone into oestradiol

Question 12

What is the effect of oestrogen in a mother with foetal stress?

Answer 12

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)

Question 13

What do high oestrogen concentrations do in general during parturition?

Answer 13

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

Question 14

What is the function of prostaglandin f2 alpha?

Answer 14

Stimulates luteolysis and contributes to the removal of the progesterone block

Question 15

What is stage one of parturition?

Answer 15

Preparation of the reproductive tract and foetus for delivery

Question 16

What is stage two of parturition?

Answer 16

Delivery of the foetus

Question 17

What is stage three of parturition?

Answer 17

Expulsion of foetal membranes

Question 18

Where does relaxin come from during stage one of parturition?

Answer 18

either from the corpus luteum or the placenta

Question 19

What is the difference in foetus delivery between monotocous species and polytocous species?

Answer 19

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

Question 20

What ruptures during stage 2 (expulsion of the foetus)

Answer 20

The chorioallantois which causes the release of ‘urine-like’ allantoic fluid from the vulva

Question 21

What causes the expulsion of foetal membranes?

Answer 21

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

Question 22

What occurs during involution of the uterus?

Answer 22

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

Question 23

What are some substances that can diffuse freely across the epithelial barrier?

Answer 23

Lipid soluble substances such as CO2 or O2
Steroid hormones

Question 24

What are some substances that have to be actively transported across the epithelial barrier

Answer 24

Glucose, amino acids, Calcium

Question 25

What is another name for placental lactogen?

Answer 25

chorionic somatomammotropin

Question 26

In what animals does foetal repositioning need to occur?

Answer 26

In foals and puppies (ventral to dorsal position)

Question 27

What occurs during stage 2 (delivery of the foetus)

Answer 27

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

Question 28

What occurs as structures begin appearing at the vulvic cleft?

Answer 28

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

Question 29

How are the foetal membranes expulled in stage 3?

Answer 29

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

Question 30

What is the name of the organ that allows the embryo to take oxygen and nutrients from the mother?

Answer 30

The placenta

Question 31

What are some behavioural changes related to stage 1 of labour?

Answer 31

restlessness, nesting activity, decrease in body temperature,