Cyclicity across the species

Question 1

What hormones control gonadotropins?

Answer 1

GnRH (+ve)
Inhibin (-ve)
Oestradiol (-ve)

Question 2

Label this schematic representation of the 21-day oestrus cycle

Answer 2

Question 3

What causes an extension of 7 days to the oestrus cycle in primates?

Answer 3

proliferation of uterus to enable placenta to invade during luteal phase - no pregnancy - growth of endometrium has to be removed - this is menstruation -> bleeding - extends cycle

Question 4

Why does is oestrus in the bitch followed by a long period of anoestrus?

Answer 4

Progesterone has a slow decline if not pregnant
There is no PGF2a production so there is no maternal recognition

Question 5

Describe the role of prolactin in the bitch

Answer 5

Prolactin is the principal leutotrophic hormone
Declining progesterone levels stimulates prolactin secretion which results in support of the CL and maintenance of progesterone
Progesterone levels still continue to decline

Question 6

how can luteal phase be terminated in the bitch?

Answer 6

Prolacting inhibitor
Repeated administration once prolactin is principal luteotrophic hormone

Question 7

Label the stages of the oestrus cycle in the non-pregnant bitch

Answer 7

Question 8

What occurs in every non-pregnant bitch during the luteal phase and pseudopregnancy?

Answer 8

Elevated progesterone;
- mammary enlargement
- potential milk secretion
Elevated prolactin:
- milk production
- behavioural changes typical of pregnancy

Question 9

Describe the oestrus cycle in queens

Answer 9

Poly-oestrus, seasonal long-day breeder
No cycling in winter

Question 10

Describe the onset of puberty in queens

Answer 10

Influenced by season
Time from birth - puberty can be less than 6 months (varies)
Always come into puberty in spring

Question 11

Describe the induction of ovulation in the queen

Answer 11

Only ovulates if mated
If not mated -> no ovulation -> regression of follicles -> new follicular wave (no luteal phase)
Magnitude of LH surge due to mating varies on different days of cycle (greatest mid oestrus), summation of LH surges when matings occur close together

Question 12

Describe the luteal phase in queens

Answer 12

If ovulated but not pregnant -> long luteal phase (pseudopregnancy)
If ovulated and pregnant -> luteal phase = 68 days