Oestrous Cycle Flashcards
What is the oestrous cycle
Female mammals reach sexual maturity, reproductive system undergoes a recurring cycle of changes, enables successful reproduction. Aims to release ova.
What is polyoestrous
Becomes fertile more than once a year
What species are polyoestrous
Cattle, pigs, mice
What is seasonally polyoestrous
More than one cycle but only during certain periods
What species of animals have seasonally polyoestrous
Horses, sheep, goats and deers
What is monooestrous
One oestrous cycle every year
What animals have monooestrous
Dogs, wolves, foxes and bears
What are the four hormones involved in oestrous cycle
FSH
LH
Oestrogen
Progesterone
What is the follicle stimulating hormone
Stimulates one or more follicles to mature
What is the Luteinising hormone
Stimulates mature follicles to produce more oestrogen
Prevents production of FSH and LH
What is Oestrogen
From mature follicles
Prevents secretion of FSH
Prevents maturation of more follicles
Rebuilds endometrium after menstruation
What is Progesterone
Mainly produced by corpus luteum
Maintains uterine lining for fertilised ovum
What are follicles
Where the eggs sit
Where eggs are released from
What is the endometrium
Lining of the uterus
What happens in the dioestrous
Luteal phase- corpus luteum is main structure
What happens in the pro-oestrous and oestrous
Follicular phase
Follicles are dominant structures
Ends with ovulation
What happens in the metoestrous
Luteal phase where corpus luteum is main structure
What is the first step of the oestrous cycle
Dioestrous
Oestrogen levels are low
Progesterone levels are high
Oestrogen is needed for ovulation
What is the second stage of the oestrous cycle
Pro-oestrous
Follicles within ovary enlarges
Progesterone decreases
Oestrogen increases
GnHR is secreted
LH and FSH increases
What is the third step of the oestrous cycle
Oestrous
Oestrogen increases
FSH and LH increases
Stimulates eggs and ovulation happens
What is the fourth step of the oestrous cycle
Metoestrous
Corpus luteum starts to decay
Progesterone increases
Oestrogen decreases
Prevents oestrogen release
EXAM QUESTION
State the two stages of the oestrous cycle that makes up the Luteal phase ( 2 marks)
Dioestrous and metoestrous
EXAM QUESTION
Describe how the level of oestrogen changes during the pro oestrous and oestrous phases of the cycle (4 marks)
During the pro oestrous phase, the follicle within the ovary enlarges. this causes the progesterone to decrease and oestrogen to increase.
The GnHR is secreted and this causes the LH and FSH to increase.
During the oestrous phase, oestrogen increases, FSH and LH increases and this stimulates eggs and ovulation happens.
Seasonal polyoestrous in sheep
Short day breeders-
What is melatonin
Light levels decrease
Increase breeding when days are shorter and less light
Released by pituitary gland when light levels are high, prevents release of FSH and LH
LH and FSH increase, stimulating oestrous happen
