fertilisation

Question 1

How can fertilisation of an egg alter the hormonal regulation of the menstrual cycle?

Answer 1

• Corpus luteum continues to secrete progesterone and oestrogen
• Endometrium is maintained which inhibits secretion of FSH from pituitary gland
• No more follicles in in the ovary begin to mature

Question 2

why is a Large number of sperm required for fertilisation?

Answer 2

• High sperm mortality
• Some travel up the wrong fallopian tube to the one the egg is in
• Some must break down the corona radiata/acrosomal reaction

Question 3

what is the first step of fertilisation?

Answer 3

Sperm moves through the cervix, up the uterus and into the fallopian tubes in search of a secondary oocyte

Question 4

what is the second step of fertilisation?

Answer 4

Sperm’s acrosome releases enzymes which break down the zona pellucida

Question 5

what is the third step of fertilisation?

Answer 5

Fertilisation membrane is formed when sperm enter oocyte-prevents more sperm entering

Question 6

what is the fourth step of fertilisation?

Answer 6

Entrance of the sperm initiates secondary oocyte to complete 2nd meiotic division

Question 7

what is the last step of fertilisation

Answer 7

Male and female pronuclei fuse and a zygote is formed

Question 8

what happens to the zygote after fertilisation?

Answer 8

• Zygote divides to become ball of cells-morula
• Morula divides = blastocyst
• Occurs as embryo moves through fallopian tube towards uterus
• Blastocyst consists of inner cell mass
• Blastocyst implants into endometrium after 6-12 days
• Inner cell mass has developed into three primary germ layers after the third week