Oestrous Cycle

Question 1

What is the oestrous cycle

Answer 1

Female mammals reach sexual maturity, reproductive system undergoes a recurring cycle of changes, enables successful reproduction. Aims to release ova.

Question 2

What is polyoestrous

Answer 2

Becomes fertile more than once a year

Question 3

What species are polyoestrous

Answer 3

Cattle, pigs, mice

Question 4

What is seasonally polyoestrous

Answer 4

More than one cycle but only during certain periods

Question 5

What species of animals have seasonally polyoestrous

Answer 5

Horses, sheep, goats and deers

Question 6

What is monooestrous

Answer 6

One oestrous cycle every year

Question 7

What animals have monooestrous

Answer 7

Dogs, wolves, foxes and bears

Question 8

What are the four hormones involved in oestrous cycle

Answer 8

FSH
LH
Oestrogen
Progesterone

Question 9

What is the follicle stimulating hormone

Answer 9

Stimulates one or more follicles to mature

Question 10

What is the Luteinising hormone

Answer 10

Stimulates mature follicles to produce more oestrogen
Prevents production of FSH and LH

Question 11

What is Oestrogen

Answer 11

From mature follicles
Prevents secretion of FSH
Prevents maturation of more follicles
Rebuilds endometrium after menstruation

Question 12

What is Progesterone

Answer 12

Mainly produced by corpus luteum
Maintains uterine lining for fertilised ovum

Question 13

What are follicles

Answer 13

Where the eggs sit
Where eggs are released from

Question 14

What is the endometrium

Answer 14

Lining of the uterus

Question 15

What happens in the dioestrous

Answer 15

Luteal phase- corpus luteum is main structure

Question 16

What happens in the pro-oestrous and oestrous

Answer 16

Follicular phase
Follicles are dominant structures
Ends with ovulation

Question 17

What happens in the metoestrous

Answer 17

Luteal phase where corpus luteum is main structure

Question 18

What is the first step of the oestrous cycle

Answer 18

Dioestrous

Oestrogen levels are low
Progesterone levels are high
Oestrogen is needed for ovulation

Question 19

What is the second stage of the oestrous cycle

Answer 19

Pro-oestrous

Follicles within ovary enlarges

Progesterone decreases

Oestrogen increases

GnHR is secreted

LH and FSH increases

Question 20

What is the third step of the oestrous cycle

Answer 20

Oestrous

Oestrogen increases
FSH and LH increases
Stimulates eggs and ovulation happens

Question 21

What is the fourth step of the oestrous cycle

Answer 21

Metoestrous

Corpus luteum starts to decay

Progesterone increases

Oestrogen decreases

Prevents oestrogen release

Question 22

EXAM QUESTION
State the two stages of the oestrous cycle that makes up the Luteal phase ( 2 marks)

Answer 22

Dioestrous and metoestrous

Question 23

EXAM QUESTION
Describe how the level of oestrogen changes during the pro oestrous and oestrous phases of the cycle (4 marks)

Answer 23

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.

Question 24

Seasonal polyoestrous in sheep

Short day breeders-

What is melatonin

Light levels decrease

Answer 24

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