Female Reproductive System Flashcards
Describe the basic structure of the female gonads
Ovary and uterine tube
What are the function of the gonads in females
Ovaries secrete large amount of oestrogen and small amounts of androgens
Production of gametes (oogenesis)
What is the ovary
Contains oocytes and releases 1 egg per month
What is the fimbriae
Connects ovary and fallopian tube, collects the released egg
What is the fallopian tube/ uterine tube/ oviduct
Tube that takes the oocyte towards the uterus, fertilisation occurs in the fallopian tube
What is the uterus
Where the fertilised egg implants
What is the endometrium
The uterus lining that grows in preparation for implanting and is lost as menstrual blood if implanting does not occur
What surrounds oocytes in the ovary
Primordial follicles
What are the three phases of the ovarian cycle
Follicular phase, ovulation and luteal phase
What is the ovarian cycle
The cycle that describes the maturation of oocytes and releases of androgens Production ovum
What is the duration of the follicular phase
Several months
What is the duration of ovulation
Few hours
What is the duration of the luteal phase
12-15 days
What happens during the follicular phase
Maturation of the follicles
What happens during ovulation
Release of an ovum from the ovary to the fallopian tube
What happens during the luteal phase
Formation of the corpus luteum
What other cycle does the ovarian cycle occur in line with
Uterine cycle
What are the three phases of the follicular phase
Pre antral phase, Antral phase, pre-ovulatory phase
What happens during the pre antral phase
- number of primordial follicles recruited to develop
- paracrine factors stimulate growth
- Antimullerian hormone limits number of follicles developing at the same time
-develop into mature pre antral follicles
What happens during the antral phase
- Fluid filled atria appears, zona granulosa increases in layers, theca interna becomes more apparent and zona pellucida becomes thicker
- Growth dependent on Follicle stimulating hormone (FSH)
Dominant follicle is selected and becomes steriodgenic gland - Androgen production from cholesterol by Theca cells and conversion of androgen to oestrogen by granulosa cells
What do theca cells catalyse
Androgen production from cholesterol
Why can granulosa cells convert androgens to oestrogen
Contain aromatase
What are the zona granulosa, zona pelluccida and theca interna
Layers of cells surrounding maturing oocyte
What happens in the pre ovulatory phase
- Dominant follicle responds to a surge in Luteinizing hormone (LH) by completing meiosis 1 and arresting in metaphase of meiosis 2
- Haploid secondary oocyte and polar body produced
- FSH increases
LH receptor and enzyme are expressed in granulosa cells, leading to progesterone production - theca and granulosa cells release inflammatory cytokines and and hydrolytic enzymes
What happens during ovulation
- inflammatory event erodes the wall of ovary and follicle
- oocyte, zona pellucida and corona radiata are release into the peritoneal cavity before being captured by the oviduct
- remnants of the follicle in the ovary form the corpus luteum
What is the role of the corona radiata
Crucial for capture of oocyte by the fimbrae and movement in the oviduct
What happens in the luteal phase
- corpus luteum develops
- granulosa cells fill with lipid
- progesterone is produced
- oestrogen; initially decreases but then rebounds
- hormone levels change dependent on pregnancy or not
Why does oestrogen initially decrease before it rebounds in the luteal phase
Due to the LH surge
What is the difference in the luteal phase between pregnancy vs no pregnancy
No preganancy- the corpus luteum degenerates into a corpus albicans, oestrogen and progesterone fall and FSH and LH rise
Pregnancy- placenta releases chorionic gonadotropin which enables the corpus luteum to persist
What are the important hypothalamic hormones in control of the ovarian cycle
Gonadotrophin releasing hormone (GnRH)
What is the function of Gonadotrophin releasing hormone in the ovarian cycle
Acts on pituitary gland, pulsatile release, high frequency = LH and low frequency= FSH
What are the important pituitary hormones
Follicular stimulating hormone (FSH) and luteinising hormone (LH)
What is the functions of FSH
- stimulates immature follicle recruitment and growth
- upregukatates aromatase activity and gene expression
- induces expression of LH receptors in granulosa cells fill
- prevents apoptosis of antral follicles
Why is aromatase important
Conversion of androgen to oestrogen
What is the functions of Luteinising hormone
- Acts on theca cells in follicles to promote androgen production
- LH surge triggers ovulation
- Acts on granulosa cells to secrete progesterone
- maintains corpus luteum
What are the important ovarian hormones
Oestrogens, progesterone and inhibin A and B
What are the three oestrogens involved in the ovarian cycle
Oestradiol, oestriol and oestrone
What is the function of oestrogens in the ovarian cycle
- prepares reproductive tract for fertilisation and pregnancy via growth of endometrium etc.
What is the dominant hormone secreted in the follicular phase
Oestrogens
What is the function of progesterone in the ovarian cycle
- promotes uterine and uterine and tube secretions to maintain and support fertilisation and egg implantation
What is the dominant hormone secreted in the luteal phase
Progesterone
Which ovarian hormones are secreted by granulosa cells
Inhibin A and B
What are the function of inhibin A and B
represses FSH secretion
Describe the hormonal control of the ovarian cycle in the luteal phase
- corpus luteum forms
- high progesterone negatively feedback and blocks positive feedback of high oestrogen
- so SH and LH levels drop
- corpus luteum regresses
- progesterone and oestrogen levels fall
- negative feedback lifted and FSH rises
