B10.3 : Menstrual cycle and Pregnancy Flashcards
1
Q
The Stages of menstrual cycle
A
- The menstrual cycle can be divided into four stages depending on the levels of the hormones.
2
Q
Stage 1 of the menstrual cycle
A
The uterus lining breaks down, resulting in a ‘period’.
3
Q
Stage 2 of the menstrual cycle
A
The uterus lining starts to build up again into a thick, spongy layer full of blood vessels.
4
Q
Stage 3 of the menstrual cycle
A
Ovulation happens. This is when an egg is released from one of the ovaries.
5
Q
Stage 4 of the menstrual cycle
A
- The uterus lining is maintained, which means that it is now ready for the arrival of a fertilised egg (which will eventually grow into a baby).
- If no fertilised egg is attached to the uterus lining, the lining breaks down and the cycle begins again.
6
Q
Menstrual cycle
A
- The menstrual cycle is a monthly cycle, which involves the maturation and release of an egg.
- If sexual intercourse has occurred, it can result in pregnancy.
- usually one egg is released into the oviduct every month
7
Q
Eggs in the menstrual cycle
A
A female is born with all of her eggs ready, but only one egg will mature each month once the female reaches puberty.
8
Q
Duration of each stage of the menstrual cycle
A
- Stage 1 (days 1-4)
- Stage 2 (days 4-14)
- Stage 3 (day 14)
- Stage 4 (day 15-28)
9
Q
Pregnancy
A
Pregnancy starts with fertilisation, when the nucleus of a sperm fuses with the nucleus of an egg, and involves many more stages
10
Q
stages of pregnancy
A
- zygote
- embryo
- Connecting the embryo to the mother (placenta and umbilical cord)
- Foetus
11
Q
zygote
A
- Once an egg is fertilised by a sperm, it is called a zygote.
- The zygote cell then starts to divide to form a ball of cells
- Once a zygote is made, it slowly moves down the oviduct
12
Q
Embryo
A
- Once a ball of cells has formed from the zygote, this is called an embryo.
- The embryo then implants itself into the wall of the uterus.
- Embryo obtains food from the yolk of the egg
- It can take hours for the embryo to reach the uterus, by this time, it is usually a ball of 16 or 32 cells
13
Q
Connecting the embryo to the mother
A
- Once the embryo has implanted, various structures form to connect the embryo to its mother;
- A placenta forms between the embryo and the wall of the uterus.
- The umbilical cord is a thick knot of blood vessels that connects the embryo and the placenta.
- An amniotic sac filled with amniotic fluid forms around the embryo to protect it from damage in the uterus.
14
Q
Foetus
A
- 6 weeks after fertilisation, the embryo can be called a foetus.
- The foetus continues to grow and become more complex.
- The baby is fully formed at around 38 to 40 weeks.
- The foetus is connected to its mother via the umbilical cord and the placenta which forms on the wall of the mother’s uterus. The foetus is protected by an amniotic sac.
15
Q
Health during pregnancy
A
- It is important that the foetus is connected to the mother’s bloodstream through the placenta so it can get everything it needs.
- But, this means that any harmful substances in the mother’s blood can easily reach the foetus.
16
Q
Placenta
A
- As the embryo grows, a placenta also grows which connects it to the wall os the uterus
- The placenta is a soft and dark red. It is lined with villi which fit closely into the uterus wall. By the time of birth, it will be a flat disk
- The placenta is where the substances are exchanged (through diffusion) between the mother’s blood and the embryo’s. It is basically the embryo’s life support system. Nutrients are passed from the mother’s blood to the baby’s blood
- It provides the foetus with oxygen, nutrients for growth.
- It also removes excretory waste products such as carbon dioxide and urea from the foetus.
- The placenta acts as barrier and can stop many (but not all) toxins and pathogens from passing from the mother’s blood to the foetus.
- Blood is not transferred as the mother and baby may not be the same blood type
17
Q
Harmful substances while pregnant
A
- Pregnant women are advised not to smoke or drink alcohol, because nicotine (in cigarettes) and alcohol can pass through the placenta into the blood of the foetus.
- This can seriously harm its development.
- Pregnant women are also told to avoid foods that are more likely to carry pathogens such as undercooked meat.
- The rubella virus is a pathogen can pass through the placenta and harm the foetus.
18
Q
Successful fertilisation
A
- If the released egg is not fertilised by a sperm within 8-24 hours after ovulation, it will die
- By this time, it has travelled a short way along the oviduct. So a sperm must reach an egg while it is quite near the top of the oviduct if fertilisation is to be successful
19
Q
Sexual intercourse
A
- When a man is sexually excited, blood is pumped into spaces inside the penis, making it erect
- To bring the sperm as close as possible to the egg, the man’s penis is placed inside the vagina of a women, this is called sexual intercourse.
20
Q
Semen
A
- sperm mixed with a fluid
2. fluid containing the sperm
21
Q
Ejaculation
A
- sperm are pushed out of the penis into the vagina
- This happens when muscles in the walls of the tubes containing the sperm contract rhythmically
- The wave of contraction begins in the testes, travels along the sperm ducts, and into the penis
- The sperm are squeezed along, out of the man’s urethra and into the woman’s vagina
- This is known as ejaculation which is when semen is deposited at the top of the vagina, near the cervix
- Ejaculation involves depositing millions of sperm in the vagina
22
Q
Sperm swimming to the egg
A
- The sperm are still quite a long way from the egg after ejaculation
- They swim, using their tails, up through the cervix, through the uterus and into the oviduct
- Sperm don’t swim very fast so it takes quite a while for them to get there. many will never get there at all. Unsuccessful sperm will all die
- However, since so many are deposited, there is a good chance that at least some of them will reach the egg
23
Q
Fertilisation
A
- One sperm enters the egg. Only the head of the sperm goes in, the tail is left outside
- Fertilisation is when the nucleus of the sperm fuses with the nucleus of the egg to form a zygote
- As soon as the successful sperm enter the egg, the egg membrane becomes impenetrable so that no other sperm can get in
24
Q
Implantation
A
- The uterus has a thin, spongy lining that the embryo sinks into. This is called implantation
- After implantation, the embryo will continue to divide
25
Q
Giving birth
A
- The embryo grows and develops in the uterus for around 9 months
- After that time, muscles in the wall of the uterus contract and push the baby out through the cervix (which will open) and vagina
- The baby is still attached to the uterus by the umbilical cord and the placenta
26
Q
After birth
A
- The placenta falls away from the uterus wall and passes out through the vagina
- This is called afterbirth
27
Q
Umbilical cord
A
- The umbilical cord is a thick knot of blood vessels that connects the embryo and the placenta.
- Inside there are 2 arteries and a vein. The arteries take blood from the foetus into the placenta, and the vein returns the blood to the foetus
28
Q
Amnion
A
- Surrounds the foetus
2. Makes a liquid called amniotic fluid which supports the embryo and protects it
29
Q
testosterone
A
hormone produced by testis in males that instigate secondary sex characteristics at puberty and (primary) production of sperm
30
Q
Oestrogen
A
oestrogen is involved in repairing and thickening the uterus lining,
31
Q
Progesterone
A
progesterone maintains the uterine lining
