4.5 Human fertilisation

• Biologie
• Middelbare school
• vwo
• Leerjaar 3

One + one = three

Benodigheden

- iPad

- Pen, pencil

- note book

- binder

For a mark

- No

Lessonup

- Yes

Bags

in bag closet

Phones 

in phone closet

today''s program 

1-test: revision... 

learning objectives: you will be able to answer the following questions (20 minutes) 

• what is fertilisation?
• what happens right before and after fertilisations takes place?

start ticket...

1. which hormones are involved in the menstrual cycle? 
2. why does the hormone production stop in the menopause?
   

1. LH and FSH, oestrogen en progesterone

2. the pituitary gland does not produce enough LH and FSH

what is fertilisation?

1. ovulation & ejaculation
2. egg cell waits 12-24h in oviduct; sperm cells swim to oviduct
3. sperm cell opens cell membrane of egg cell; cell membrane becomes impenetrable for the other sperm cells;
4. head  of sperm cell enters egg cell
5. fertilisation = nucleus of sperm cell fuses with nucleus egg cell. 

• ovulation on day 14/15 of menstrual cycle
• egg cell lives 12-24 hrs after ovulation = fertile period 
• sperm cells have to swim about 15 cm
• zygote becomes embryo at implantation time 
• embryo implantates endometrium 5 days after fertilisation
• with fertilisation also the hereditary information is combined

why is it impossible for a second sperm cell to enter the egg cell

1. the nuclei of the first sperm cell and the egg are already fused
2. the cell membrane of the egg cell has become impenetrable
3. after the first sperm cell has entered, the egg starts producing poisonous substances
4. the tail of the first sperm cell starts to kill the others

twins = two offspring from one pregnancy

identical: monozygotic

Siamese/conjoined: monozygotic 

fraternal: dizygotic

how do identical twins emerge

1. by coincidence two sperm cells enter the same egg cell and the zygote breaks in two halves
2. parallel ovulations + parallel fertilisation and parallel implantation
3. after cleavages a group of cells separates from the embryo before implantation in the lining of the uterus
4. after cleavages a group of cells separates from the embryo just after implantation in the lining of the uterus

homework

lrn par. 4.5 Human fertilisation

do exercises 1-5 and 7-9 (skip exercise 6)