Question

Study the flow chart given below. Name the hormones involved at each stage and explain their functions.

Hypothalamus
↓
Pituitary
↓
Ovary
↓
Pregnancy

Hint:

Hypothalamus GnRH, pituitary FSH and LH, ovary oestrogen and progesterone, then placental hormones.

Answer 1

Step 1: Understanding the flow chart:
The chart follows the hormonal control of the female cycle and then pregnancy. We name the hormone at each stage.

Step 2: Hypothalamus:
It secretes Gonadotropin Releasing Hormone (GnRH). GnRH acts on the anterior pituitary and makes it release LH and FSH.

Step 3: Pituitary:
FSH stimulates the growth of follicles in the ovary and the secretion of oestrogen.
LH causes ovulation (LH surge) and helps the ruptured follicle become the corpus luteum.

Step 4: Ovary:
Oestrogen repairs and thickens the endometrium and brings secondary sexual characters.
Progesterone, from the corpus luteum, maintains the endometrium for implantation and supports pregnancy.

Step 5: Pregnancy:
The placenta releases hCG, which keeps the corpus luteum active, and hPL, which helps the mammary glands and growth.
Relaxin softens the pelvic ligaments. Oestrogen and progesterone rise in high amounts to maintain pregnancy.
At childbirth, oxytocin from the posterior pituitary causes uterine contractions.

Final Answer:
GnRH; FSH and LH; oestrogen and progesterone; hCG, hPL, relaxin (plus oxytocin at delivery).