(a) Briefly explain the events of fertilisation and implantation in an adult human female.

• Fertilisation

Fertilisation occurs in the ampulla / ampullary-isthmic junction of the fallopian tube, when sperm comes in contact with the ovum, it induces changes in the zona pellucida of the ovum that block the entry of additional sperms and thus ensures only one sperm, the secretions of the acrosome help the sperm to enter the cytoplasm of the ovum by dissolving the zona pellucida and plasma membrane , after the entry of sperm into the cytoplasm of ovum induces completion of meiosis II (of secondary oocyte), fusion occurs between the nucleus of ootid (ovum) and that of sperm to form a diploid zygote

• Implantation:

− The trophoblast layer gets attached to the endometrium.

− The uterine cells divide rapidly and cover the blastocyst as a result the blastocyst becomes embedded in the endometrium of uterus

Hormones in sequence of their secretion in a pregnant woman.

FSH; LH; hCG; Relaxin.

− FSH:

Source: Anterior Pituitary.

Function: Stimulates follicular development

− LH: Source: Anterior Pituitary.

Function: It causes rupture of Graafian follicle and release of ovum into fallopian tube / Ovulation

− hCG:

Source: Placenta.

Function: It supports foetal growth, metabolic changes in mother and maintenance of pregnancy.

− Relaxin:

Source: Ovary.

Function: It facilitates parturition.