PREGNANCY
Fertilisation Process
Copulation and Site of Fertilisation
● Sexual intercourse involves insertion of erect penis into the vagina.
● Semen containing sperm is deposited near the cervix.
● This process is called copulation.
● Fertilisation usually occurs in the upper part of the fallopian tube.
Passage of Sperm
● Sperm enter through the cervix, pass the uterus, and reach the fallopian tube.
● Tail of the sperm propels it forward using whip-like movements.
● Mitochondria in the midpiece provide energy for movement.
,Fusion of Sperm and Ovum
● Fimbriae help suck the ovum into the fallopian tube from the ovary.
● Ovulation releases a mature ovum from the ovary.
● Sperm use hydrolytic enzymes in the acrosome to break down follicle cells around the
ovum.
● Nucleus of sperm (23 chromosomes) fuses with ovum nucleus (23 chromosomes).
● Fertilisation is the fusion of two haploid nuclei to form a diploid zygote (46
chromosomes).
Zygote to Blastocyst Development
● After fertilisation, the zygote moves through the fallopian tube to the uterus.
, ● Movement is aided by peristaltic movements and cilia in the fallopian tube.
● The zygote undergoes mitotic divisions to form a blastocyst.
Implantation
● The blastocyst remains in the uterus for 2–5 days before implanting.
● Implantation occurs in the endometrium of the uterus.
● Oestrogen and progesterone prepare the endometrium by thickening and increasing
vascularisation.
● The blastocyst continues to develop into an embryo, and later a foetus.
Pregnancy and Embryo Development
Pregnancy Overview
Fertilisation Process
Copulation and Site of Fertilisation
● Sexual intercourse involves insertion of erect penis into the vagina.
● Semen containing sperm is deposited near the cervix.
● This process is called copulation.
● Fertilisation usually occurs in the upper part of the fallopian tube.
Passage of Sperm
● Sperm enter through the cervix, pass the uterus, and reach the fallopian tube.
● Tail of the sperm propels it forward using whip-like movements.
● Mitochondria in the midpiece provide energy for movement.
,Fusion of Sperm and Ovum
● Fimbriae help suck the ovum into the fallopian tube from the ovary.
● Ovulation releases a mature ovum from the ovary.
● Sperm use hydrolytic enzymes in the acrosome to break down follicle cells around the
ovum.
● Nucleus of sperm (23 chromosomes) fuses with ovum nucleus (23 chromosomes).
● Fertilisation is the fusion of two haploid nuclei to form a diploid zygote (46
chromosomes).
Zygote to Blastocyst Development
● After fertilisation, the zygote moves through the fallopian tube to the uterus.
, ● Movement is aided by peristaltic movements and cilia in the fallopian tube.
● The zygote undergoes mitotic divisions to form a blastocyst.
Implantation
● The blastocyst remains in the uterus for 2–5 days before implanting.
● Implantation occurs in the endometrium of the uterus.
● Oestrogen and progesterone prepare the endometrium by thickening and increasing
vascularisation.
● The blastocyst continues to develop into an embryo, and later a foetus.
Pregnancy and Embryo Development
Pregnancy Overview
