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Pregnancy (Fertilisation (Occurs when the nucleus of the sperm fuses with…
Pregnancy
Fertilisation
Occurs when the nucleus of the sperm fuses with the nucleus of the egg, forming a diploid zygote.
Events leading to fertilisation: 1. Insemination takes place in the vagina.
2.Sperm swim to the fallopian tubes.
- Sperm swarm around the egg.
- Head of the sperm enters the egg and tail breaks away.
- Fertilisation membrane forms around the egg.
- Fertilisation occurs.
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Implantation
Happens about 6-9 days after fertilisation. By this time the zygote has grown to form an embryo. The amnion is the membrane that surrounds the embryo and secretes an amniotic fluid, which will surround and protect the embryo(shock-absorber). During the first 4 weeks the developing embryo gets nutrients from the endometrium but as it gets bigger it gets them from the placenta.
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Placenta
Is made up of the outer membrane called the chorion and the endometrium. It becomes fully functional 3 months into pregnancy. The umbilical chord connects the baby to the placenta.
Functions:
1.Exchange: allows gases, nutrients, waste, antibodies, drugs and some hormones to be exchanged by diffusion.
2.Prevents bloods from mixing: blood groups might not be compatible and the blood pressure from the mothers system would damage the embryo.
3.Hormone production: produces progestrone.
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Embryonic Development
Day10: the inner cell mass of the blastocyst form 3 layers of cells called primary germ layers: the ectoderm, mesoderm and endoderm.
Ectoderm: hair,nervous system
Mseoderm: muscles, respiratory system
Endoderm: inner lining of digestive, respiratory system.
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Birth
Hormones associated with birth: 10-12 weeks progestrone is produced by the corpus lutem and after 12 weeks it is made by the placenta but stops right before birth. The pituitary gland produces oxytocin which causes stronger contractions of the uterus
Stages: 1.Contractions of the uterus push the head of the foetus towards the cervix; the amnion bursts and amniotic fluid is released.
- The head of the baby is forced out through the vagina.
- The afterbirth(placenta and foetal membranes) are expelled from the vagina.
Breastfeeding
Colostrum: a thick yellow fluid produced by the breast and has less fat and sugar than breastmilk but is higher in minerals, proteins and antibodies
Prolactin: stimulates milk production and continues to be produced as long as the baby breastfeeds.
Benefits: ideal balance of nutrients, antibodies in the milk meaning the baby has extra resistance to most common infections and it is sterile.
Contraception
is the deliberate prevention of fertilisation or pregnancy. Natural Contraception: not having intercourse during the fertile period.
Mechanical Contraception: barriers to sperm from reaching the egg ie: condom or cap
Chemical Contraception: use of spermicides ie:the pill
Surgical Contraception:** sterilisation for females and vasectomy for males.
*Birth Control: refers to methods taken to limit the number of children that are born.