Fertilisation

Question 1

What is fertilisation?

Answer 1

The fusion of the male nuclei and female gametes that results in the production of new offspring.

Question 2

What is needed for fertilisation to occur?

Answer 2

Male sperm need to be brought into contact with a female ovum.

Question 3

What is insemination?

Answer 3

When an erect penis releases semen into the vagina through ejaculation during sex.

Question 4

How does an erection happen?

Answer 4

Results from blood rushing into the spaces of the penis’ erectile tissue initiated by sexual excitation

Question 5

What is ejaculation?

Answer 5

Muscular contractions that propel semen from the penis.

Question 6

What is semen?

Answer 6

The liquid that nourishes and aids the transport of sperm - aka seminal fluid

Question 7

What does semen contain?

Answer 7

Secretions of seminal vesicles, bulbo-urethral glands, and prostate gland

Question 8

What is the function of semen?

Answer 8

1. Nourishment
2. Provides sperm with fluid to swim
3. Neutralises the acid nature of the male urethra and vagina
4. Contains enzymes that activate sperm after ejaculation

Question 9

What does the vagina do to allow for easy entry of the penis?

Answer 9

Copious secretions of mucus by glands located around the cervix and in the vaginal opening region lubricate epithelial lining.

Question 10

What happens to sperm once within the vagina?

Answer 10

The sperm travel through the cervix and the uterus body into the uterine tube. They reach the upper portions within a few minutes

Question 11

What helps sperm through the female reproduction tract?

Answer 11

Muscular contractions of the uterus

Question 12

What helps transport ova towards the uterus after ovulation?

Answer 12

Muscular contractions of the uterine tube, together with the beating action of cilia

Question 13

How many sperm reach the uterine tubes

Answer 13

Only a few thousand reach the uterine tube

Question 14

What is sperm mortality?

Answer 14

The death rate of sperm - high

Question 15

Where does fertilisation occur?

Answer 15

In the uterine tubes when the ovum is about 1/3 of the way down the tube

Question 16

What are the two layers of the secondary oocyte?

Answer 16

1. Outer corona radiata
2. Inner zona pellucida

Question 17

What is the corona radiata?

Answer 17

Consists of follicle cells held together by cementing materials that contain acid.

Question 18

What is the zona pellucida?

Answer 18

A glycoprotein matrix surrounding the plasma membrane of the oocyte

Question 19

What is the function of the enzyme in the outer surface of the acrosome on the sperm’s head?

Answer 19

Capable of breaking down the acid in the cementing material that holds the cells of the corona radiata together

Question 20

Why are a large number of sperm required if fertilisation is to occur?

Answer 20

When several thousand sperm surround oocyte there is enough enzyme to loosen corona cells, allowing 1 sperm to penetrate corona radiata.

Question 21

What is the first step of fertilisation?

Answer 21

Hundreds of sperm attracted to corona radiata begin to break through barrier of granulosa cells and approach zona pellucida

Question 22

What is the second step of fertilisation?

Answer 22

Contact with zona pellucida triggers acrosome reaction, causing sperm secrete digestive enzymes that break down glycoprotein membrane of zona pellucida and help to expose oocytes plasma membrane

Question 23

What is the third step of fertilisation?

Answer 23

A single sperm succeeds in burrowing through corona radiate/zona pellucida and making contact with oocyte’s plasma membrane.

Question 24

What is the fourth step of fertilisation?

Answer 24

Sperm’s plasma membrane fuses with that of oocyte and sperm releases its nucleus into cytoplasm of oocyte.

Question 25

What is a male pronucleus?

Answer 25

The haploid nucleus of the sperm

Question 26

What is a female pronucleus?

Answer 26

The haploid nucleus of the oocyte

Question 27

How do identical twins form?

Answer 27

When zygote splits into two identical embryos immediately after the gametes fuse

Question 28

How do fraternal twins form?

Answer 28

Results from fertilisation of two eggs by two different sperm in the fallopian tube. - happens when female release 1+ egg during ovulation