Reproductive System Flashcards
What is the role of the SRY gene in sexual differentiation? How does the absence of this gene influence embryonic development?
Determines male or female embryo development. Presence of SRY gene = male, absence = female.
Describe the three layers of the uterus and briefly explain the primary function of each layer.
- Endometrium: Inner lining that thickens and is shed during the menstrual cycle to support a potential embryo.
- Myometrium: Thick muscular layer responsible for uterine contractions during childbirth.
- Perimetrium: Outer protective layer).
Outline the key differences between oogenesis and spermatogenesis in terms of timing and the number of viable gametes produced.
Oogenesis: Begins before birth, pauses during childhood, and resumes at puberty, releasing one viable ovum per cycle. Spermatogenesis: Begins at puberty and continuously produces millions of viable sperm.
Briefly explain the two-cell hypothesis of steroidogenesis in the ovary, highlighting the roles of the theca and granulosa cells.
- Theca cells are stimulated by LH to produce androgens from cholesterol.
- These androgens are then transported to granulosa cells, which, under FSH stimulation, convert them into oestradiol.
What are the key events that occur during the follicular phase of the ovarian cycle, and which hormones primarily regulate this phase?
- The follicular phase involves the growth and maturation of ovarian follicles.
- FSH primarily stimulates follicular development and oestrogen production by the developing follicles.
- Rising oestrogen levels exert negative feedback initially, followed by positive feedback leading to the LH surge.
Describe the hormonal cascade leading to ovulation, specifically mentioning the roles of GnRH, LH, and oestrogen.
- Hypothalamus releases GnRH with increasing frequency.
- This stimulates anterior pituitary to release FSH and LH.
- FSH promotes follicular growth, leading to increased oestrogen production.
- High oestrogen levels exert positive feedback on the hypothalamus and pituitary, causing a surge in LH, which triggers ovulation.
What changes occur in the ovary following ovulation, leading to the formation and function of the corpus luteum?
- Ruptured follicle collapses, and blood vessels invade.
- Granulosa and theca cells luteinise under the influence of LH, forming the corpus luteum, which becomes a temporary endocrine gland.
Explain the role of progesterone secreted by the corpus luteum on the uterus and the hypothalamic-pituitary axis.
- Prepares the endometrium of the uterus for embryo implantation by promoting glandular growth and vascularisation.
- Exerts negative feedback on the hypothalamus, reducing GnRH pulse frequency and inhibiting the release of FSH and LH.
Describe the process of luteolysis and the hormonal changes that accompany the degeneration of the corpus luteum.
Luteolysis is the degeneration of the corpus luteum in the absence of pregnancy. It is triggered by PGF2α released from the uterine endometrium, leading to a decrease in progesterone and oestrogen levels, and the formation of the corpus albicans (scar tissue).
Briefly outline two contrasting effects of oestrogen and progesterone on the tissues of the female reproductive system.
Oestrogen generally increases secretions, cilia activity, and muscle activity in the oviduct, while progesterone reduces these activities. In the uterus, oestrogen stimulates the growth of the endometrium, whereas progesterone promotes further glandular development and secretion of nutrient-rich fluids.
