Regressive and progressive taxes

11. Explain how hormones control the menstrual cycle in human females.
The hypothalamus is a female brainstem that is the regulatory centre of the menstrual cycle. The hypothalamus produces ahormone know as gonadotrophin releasing hormone (GnRH). The target tissue of GnRH is the nearby pituitary gland and then it results in the pituitary. This produces and secretes two hormones into thebloodstream. One of these two hormones is Follicle Stimulating Hormone (FSH) and the other one is Luteinizing Hormone (LH). The target tissues for these two hormones are the ovaries. FSH and LH have severaleffects on the ovaries. FSH increases the production and secretion of another reproductive hormone by the follicle cells of the ovary. This hormone is called oestrogen. Oestrogen enters thebloodstream, its target tissue is the endometrium of the uterus. It increases the blood vessels of the endometrium and it becomes highly vascular. When the levels of oestrogen are too high oestrogen inhibitsFSH productions and stimulates LH production. LH stimulates ovulation and formation of the corpus leteum. Corpus leteum secretes progesterone. Progesterone maintains the uterus lining. Progesteroneinhibits FSH production and the corpus leteum disintegrates and progesterone level falls.
12. Compare the process of spermatogenesis and oogenesis.
Oogenesis | Spermatogenesis |
The resultinggametes are very large. | The resulting gametes are very small. |
The haploid nucleus results from meiosis. | Haploid nucleus results from meiousis |
The secondary oocyte is released during ovulation |Spermatozoa are released during ejaculation |
Ovulation starts at puberty, it occurs in each of the menstrual cycle and then stops during menopause. | Spermatogenesis can continue throughout yourlife, it starts at puberty. |
Occurs within ovaries (gonad tissue). | It occurs within the testis (gonad tissue). |
One gamete is produced for each germinal cell which begins meiosis. (Plus 3...