3.2 Fertilisation

Understand that fertilization involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo.

fertilization --> zygote --> embryo

1.  Process -
(Gametes are sex cells. The male gametes are the sperm, and the female gametes are the eggs.)

adult male  46 (diploid cell) --> (meiosis) --> half chromosome (number) set (Hoploid) --> Gametes 23

adult female 46 (diploid cell) --> (meiosis) --> half chromosome (number) set (Hoploid) --> Gametes 23

The cells that are formed by meiosis have half as many chromosomes as the cell that formed them.

2.  Fertilization occurs and the joining (fusion) of a male gamete and a female gamete. The new cell that is formed divides over and over again by meiosis. This creates the many cells that eventually form a new individual. Involves a half set of chromosomes (hoploid) + a half set of chromosomes (hoploid) = a diploid cell = Zygote

Stages of meiosis

3. Fertilization complete --> new cell (combo of the male+female chromosomes) --> process of cell division (Mitosis) --> both contain 46 chromosomes --> each of these divide (still containing 46 chromosomes) --> embryo.

3.10 Menstrual Cycle

Understand the roles of oestrogen and progesterone in the menstrual cycle. 

 1. Endocrine glands = produce hormones (chemical messengers) which are released into the blood from a gland and travel to a target organ. The main glands in the Menstrual cycle are the ovaries. "Endocrine gland ----> (hormones) --> target tissue ---> effect."

2. Endometruim = is the process of cell division of the human embryo that occurs during early stages of development. It exactly spans from the first moment of fertilization to the end of the 8th week of development.




3.  Menstrual cycle =  Lasts about 28 days
Main features of the menstrual cycle.

• The start of the cycle, day 1, is when bleeding from the vagina begins. This is caused by the loss of the lining of the uterus, with a little blood. This is called menstruation or having a period.
  
• By the end of about day 5, the loss of blood stops. The lining of the uterus begins to re-grow and an egg cell starts to mature in one of the ovaries.
  
• At about day 14, the mature egg cell is released from the ovary. This is called ovulation. The egg cell travels through the egg tube towards the uterus.
  
• If the egg cell does not meet with a sperm cell, the lining of the uterus begins to break down and the cycle repeats.
  

3.9b Female Reproductive System

The female reproductive system contains these parts:

Ovaries - The two ovaries contain hundreds of undeveloped female sex cells called egg cells
Egg tubes - Each ovary is connected to the uterus by an egg tube. The egg tube is lined with cilia. Every month, an egg develops and becomes mature, and is released from an ovary. The cilia waft the egg along inside the egg tube and into the uterus.
Uterus - The uterus is also called the womb. It is a muscular bag with a soft lining. The uterus is where a baby develops until its birth.
Cervix - Is a ring of muscle at the lower end of the uterus. It keeps the baby in place in pregnancy.
Vagina - The vagina is a muscular tube that leads from the cervix to the outside of the woman's body.

3.9a Male Reproductive System

Recall the structure and function of the male and female reproductive systems.


1. The male reproductive system contains these parts:

Bladder- stores urine
Testes - to carry out the process of "meiosis" which produce gamete sper
Penis - carries sperm cells into the vagina
Epididymis - is the coiled tube system - stores sperm cells
Vas deferens - is a tube - carries sperm cells to the penis during sex
Prostate - adds 20 to 30% of semen - contains sugars + alkalies
Seminal vesicles - add 70% of semen - contains sugars + alkalies (in which the sperm cells can travel)
Urethra - is the common tube which join the left and right testies - takes semen down the testes - carries urine as well.

3.12 Amniotic fluid

Understand how developing embryo is protected by Amniotic fluid

---> function : a) protects the developing embryo. b) the embryo"flouts" because the bones cannot support the child as they are not hard at that time.
1. Surrounding the uterus space is the Amniotic fluid which is mostly water.

2. It cannot be "compressed".  Any force applied to the uterus wall, the amniotic fluid will absorb the pressure and prevent any possible damage to the embryo.