Quick questions on Fertilisation, implantation and the hormonal control of pregnancy: HSC Biology Module 5

Before pregnancy, the menstrual cycle prepares an egg and the uterus each month. FSH (follicle stimulating hormone) from the anterior pituitary makes a follicle mature; the follicle secretes oestrogen, which thickens the endometrium. A mid-cycle surge of LH (luteinising hormone) triggers ovulation (release of the egg) around day 14. LH then turns the empty follicle into the corpus luteum, which secretes progesterone to maintain the endometrium for a possible pregnancy.

The placenta has two jobs. As an exchange organ, it brings maternal and foetal blood close together (without mixing) so oxygen, glucose, amino acids and antibodies pass to the foetus and carbon dioxide and wastes pass to the mother. As an endocrine organ, from the late first trimester it secretes the progesterone and oestrogen that maintain the endometrium and the pregnancy, taking over from the corpus luteum.

If a question touches pregnancy maintenance, say "negative feedback"; if it touches birth, say "positive feedback" - and justify it (opposes change vs amplifies change).

A strong answer reads as a chain: hCG → corpus luteum → progesterone → endometrium maintained → FSH/LH suppressed. Each arrow is worth marks.

Zygote, morula, blastocyst, trophoblast, endometrium, corpus luteum - use the exact term the marking guidelines expect, and label diagrams correctly (homologue stages, the implanting blastocyst, the hormone curves).