Reproduction In Man Flashcards
What happens if fertilisation does not occur?
- Egg breaks down
- High concentrations of progesterone inhibits LH production
- lowered LH levels result in the breakdown of the corpus luteum
- progesterone is no longer secreted
- uterine lining breaks down
- uterine lining is discharged along with blood through the vagina (marking the first day of menstruation)
- pituitary gland stimulates the production of the Follicle secreting hormone and the menstrual cycle repeats
What happens to the zygote and corpus luteum if fertilisation occurs?
The fertilised egg becomes a zygote , which develops into an embryo
- the embryo embeds itself in the uterine lining
- embryo secrets a hormone preventing the breakdown of the corpus luteum
- the corpus luteum continues to secrete oestrogen and progesterone until the placenta forms and is able to take over the production of both hormones
When are the fertile periods of the menstrual cycle ?
Days 11-16
Eggs can be fertilised up to 2 days after its release
Sperms can live up to 2-3 days in the female reproductive system
Stages in the menstrual cycle
Menstrual stage : day 1-5
First day of menstruation marks the first day of the menstrual cycle
Uterine lining breaks down and flows out of the body through the vagina
Pituitary gland stimulates follicle-secreting hormone into the bloodstream
Follicle stage : day 6 - 13
FSH stimulates
- follicles developing in the ovaries
- secretion of oestrogen by the follicles
Oestrogen causes the growth and repair of the uterine lining
High levels of oestrogen in the blood
- inhibits FSH production , prevents the maturation and growth of more follicles
- stimulates the pituitary gland to produce lutenising hormone (LH)
Ovulation : day 14
Lutenising hormone results in the release of a mature egg (Ovulation)
Lutenising hormone results in the production of the corpus luteum which secretes progesterone and some oestrogen
Corpus luteum stage : day 15-28
Progesterone prepares the uterine lining for the fertilised egg by;
- Thickens the uterine lining further
- Further supplying it with blood capillaries
High levels of progesterone inhibits
- ovulation
- FSH production
What is puberty
The stage of human growth and development in which the body becoming capable of reproduction
What happens during puberty?
- sex organs mature
- sex organs secrete sex hormones like oestrogen and progesterone for women and testosterone for men
- release of sex hormones result in the development of secondary sexual characteristics
What happens to males during puberty
Testicles and penis increase in size
Larynx enlarges and voice deepens
Hair begins growing at the pubic regions, face, and armpits
Production of sperm begins
What happens to females during puberty?
Hips broaden
Hair begins growing at the pubic region, armpits
Breasts increase in size
Menstruation and ovulation begins
What is the menstrual cycle?
The cycle of events that takes place in the female body every month
What is menstruation?
The process whereby blood is discharged from the uterus via the vagina every month
What affects the length of the menstrual cycle?
Stress, illness, unbalanced diet and/or malnutrition
Changes in a follicle during menstruation
Ovaries contain developing follicles. Young follicles are known as primary follicle. Each primary follicle consists of a potential egg cell surrounded by a layer of smaller cells known as follicle cells.
A primary follicle develops into a Graafian follicle during the follicle stage. A Graafian follicle contains a mature egg surrounded by a layer of follicle cells and a fluid filled space.
The Graafian follicle then ruptures to release the mature egg into the oviduct (ovulation) this usually occurs on the 14th day of each menstrual cycle . An egg is released every month and the ovaries take turns to release the egg
The Graafian follicle develop to form the corpus luteum which secretes progesterone and a bit of oestrogen (hormones needed to maintain a pregnancy)
If fertilisation doesn’t occur the corpus luteum will eventually break down
What is fertilisation?
The process whereby the haploid nucleus of a sperm fuses with the haploid nucleus of an ovum to form a diploid zygote
What happens during fertilisation ?
The sperm penetrates the egg
When the sperm makes contact with the egg the sperm’s acrosome releases an enzyme that
- disperses the follicle cells
- breaks down part of the egg membrane to allow the sperm to enter
Only one sperm enters the egg ; the haploid nucleus from the sperm fuses with the haploid nucleus of the egg to form a diploid zygote
As soon as a sperm enters the egg, the membrane of the egg changes such that no other sperm can enter it
The other sperms that were unable to fertilise the egg eventually die
What happens after fertilisation?
- Implantation
- Development of placenta
- Development of amniotic sac
What is implantation and what happens during implantation?
Implantation refers to the event when the embryo becomes embedded in the uterine lining
The cilia lining the oviduct sweep the fertilised egg towards the uterus
Zygote travels down the oviduct and undergoes Mitosis to form an embryo
It typically takes the embryo five days to reach the uterus
The embryo may float freely in the uterus for 2 days before it gets implanted into the uterine lining
What happens during the development of the placenta
After implantation, finger like projections called villi grow from the embryo into the uterine lining
Together with the embryonic villi and the uterine lining make up the placenta
An umbilical cord attaches the embryo to the placenta
What happens during the development of the amniotic sac?
An amniotic sac is the membrane that encloses the embryo in a fluid filled space called the amniotic cavity
Fluid in this cavity is known as the amniotic fluid
The embryo continues to develop, once all the major organs are formed it is known as a foetus
