Female Physiology Flashcards
What are the two functions of the ovaries?
To produce oocytes in preparation for fertilisation
To produce sex steroids (oestrogen and progesterone)
What influences the production of oestrogen and progesterone?
Pituitary gonadotrophins (LH and FSH)
What is gametogenesis?
It occurs when a haploid cell is formed from a diploid cell through meiosis
What term is used to refer to female gametogenesis? What does this process result in the formation of?
Oogenesis
Ovum
When does oogenesis begin?
The foetus prior to birth
What oogenesis steps occur before birth?
Oogonia are formed within each ovary
They undergo mitotic division to form primordial follicle
What are the two features of primordial follicles?
An oocyte
A layer of granulosa cells
At what stage of cell division are primordial follicles halted at before birth?
Prophase I
What resumes meiotic division during puberty?
Gonadotrophins are released from the hypothalamus
What ooogensis steps occur during puberty?
The primordial follicle divides into the primary follicle (pre-antral)
The primary follicle divides into the secondary follicle (pre-antral)
The secondary follicle divides into the tertiary follicle (antral)
What stimulates the beginning of the antral stage?
FSH
What are the two features of primary follicles?
Zona pelludica
Increased no. of granulosa cells
What are the three features of secondary follicles?
Theca layer
FSH receptors
Follicular fluid formation
What is the inner theca layer referred to as? What is its function?
Theca interna
To secrete androgen hormones in response to LH release
What is the outer theca layer referred to as? What is it made up of?
Theca externa
Connective tissue cells containing smooth muscle and collagen
What are the two features of tertiary (Graffian) follicles?
The follicular fluid filled areas between the granulosa cells combine to form a central fluid filled space called the antrum
The corona radiata is made of granulosa cells and surrounds the zona pellucida and the oocyte
At what cell division stage is the tertiary follicle halted at after puberty?
Metaphase II
What resumes the secondary meiotic division of follicles?
When the egg is fertilised with sperm
What are the two types of chromosomal divisions?
Mitosis
Meiosis
When does mitosis occur during oogenesis?
Before birth, when the oogonium forms the primary oocyte
What is mitosis?
The division of a single cell into two identical daughter cells containing the same number of chromosomes
How many chromosomes are contained in the oogonium?
46
How many chromosomes are contained in the primary oocyte?
46
When does meiosis occur during oogenesis?
After puberty
What is meiosis?
This is when a single cell divides twice to produce four cells containing half the original amount of genetic information
What does meiosis result in the formation of?
The secondary follicle (n)
The smaller polar body (n)
How many chromosomes are contained in the secondary follicle?
23
How many chromosomes are contained in the smaller polar body?
23
How many chromosomes are contained in the fertilised egg? Explain this
46
The follicle (n) can undergo fertilisation with a sperm cell (n) to form a fertilised egg (2n)
Which axis regulates the female reproductive system?
Hypohypothalamic-pituitary-gonadal (HPG) axis
What is the hypothalamic-pituitary-gonadal (HPG) axis?
The hypothalamus releases gonadotrophin-releasing hormone (GnRH)
This stimulates the anterior pituitary gland to produce luteinising hormone (LH) and follicle stimulating hormone (FSH)
What is the overall function of LH and FSH?
To develop follicles
What does FSH bind to?
Granulosa cells
What are the three functions of FSH?
To stimulate follicle growth, by converting dormant secondary follicles into Graafian follicles
To permit the conversion of androgens to oestrogens
To stimulate inhibin secretion
What does LH bind to?
Theca cells
What is the function of LH?
To stimulate production and secretion of androgens
What type of hormone is oestrogen?
Steroid
What causes the production of oestrogen? Where does this production occur?
FSH and LH
Ovaries
What tissues does oestrogen act on?
Tissues with oestrogen receptors
What are the five functions of oestrogen?
Breast tissue development
Pubertal sex organ development & growth
Uterus blood vessel development
Endometrium development
Production of a thin alkaline cervical mucus to facilitate sperm transport
What type of hormone is progesterone?
Steroid
What causes progesterone production? Where does this production occur?
Ovulation
Corpus luteum
Where is progesterone produced during pregnancy? At what gestation does this production occur?
Placenta
10 weeks gestation
What tissue does progesterone act on?
The tissues which have previously been stimulated by oestrogen
What are the four functions of progesterone?
Endometrium thickening & maintenance
Cervical mucus thickening
Body temperature rise
Production of a thick acidic cervical mucus to facilitate sperm transport
What does progesterone turn the endometrium into?
Decidua
What positive feedback system controls the menstrual cycle?
Oestrogen (in the absence of progesterone) acts to increase the GnRH and the LH surge from the anterior pituitary
When does the positive feedback system act on the menstrual cycle?
This occurs mid-menstrual cycle – specifically around the twelfth to fourteenth day
What two negative feedback systems control the menstrual cycle?
As the levels of oestrogen increase, there is increased suppression on the hypothalamus and anterior pituitary to suppress the release of GnRH, LH and FSH.
As the levels of progesterone increase, there is increased suppression on the hypothalamus and anterior pituitary to suppress the release of GnRH, LH and FSH
What are the three phases of the menstrual cycle?
Follicular phase
Ovulation
Luteal phase
When does the follicular phase of the menstrual cycle occur?
It occurs from the start of menstruation to the moment of ovulation
This tends to occur in the first 14 days in a 28-day cycle
What occurs during the follicular phase of the menstrual cycle?
At the start of a new cycle, there is little ovarian hormone production, and the follicle begins to develop independently of gonadotropins or ovarian steroids
Due to the low steroid and inhibin levels, there is little negative feedback at the HPG axis – resulting in an increase in FSH and LH levels
These hormones cause oestrogen levels to rise, which allows only one dominant follicle to continue to maturity and complete each menstrual cycle and the other weaker follicles to form polar bodies
Once oestrogen levels have peaked mid-cycle, a positive feedback response on the HPG axis is initiated
This increases the release of GnRH and gonadotrophins
However, the effect is only reflected with a surge in LH levels due to increased follicular inhibin selectively inhibiting FSH production at the anterior pituitary
What causes ovulation?
LH surge
What is ovulation?
The follicle ruptures and the secondary oocyte is released into the fallopian tube by the fimbria
What two hormones does the follicle secrete after ovulation? What effect does this have?
Oestrogen
Progesterone
This stimulates a negative feedback response on the HPG axis, which stalls the cycle in anticipation of fertilisation
Which hormone is released after ovulation occurs and can be used as a marker of fertility?
Progesterone
When does the luteal phase of the menstrual cycle occur?
It occurs from the moment of ovulation to the start of menstruation, which tends to occur in the final 14 days in a 28-day cycle
What occurs during the luteal phase of the menstrual cycle?
The corpus luteum is the tissue in the ovary that forms at the site of a ruptured follicle following ovulation
It secretes high levels of progesterone, which thickens and vascularises the endometrial lining whilst also thickening the cervical mucus
The hormone is therefore involved in maintaining conditions for fertilisation and implantation (decidualisation)
The corpus luteum also secretes a small amount of oestrogen
What happens if fertilisation doesn’t occur during the menstrual cycle?
The corpus luteum spontaneously regresses after 14 days into corpus albicans and stops producing oestrogen and progesterone
This fall in oestrogen and progesterone causes the endometrium to break down and menstruation to occur
In addition to this, the stromal cells of the endometrium release prostaglandins, which is a hormone that encourages the endometrium to break down and the uterus to contract
The negative feedback from oestrogen and progesterone on the hypothalamus and anterior pituitary ceases allowing the levels of LH and FSH to rise and the cycle to restart
What happens if fertilisation occurs during the menstrual cycle?
The synchtiotrophoblast of the embryo produces human chorionic gonadotropin (HcG), which is a hormone that maintains the corpus luteum
B-hCG results in progesterone levels continuing to rise
On fertilisation of the egg, the sperm stimulates the release of which substance to prevent polyspermy?
Calcium ions
What is the chorion?
The outermost membrane around the embryo
What cells are found in the outer edge of the chorion?
Trophoblast cells
What do trophoblast cells produce?
Beta-human Chorionic Gonadotrophin (B-hCG)
What is the target of B-hCG?
Corpus luteum in ovary
What is the function of B-hCG?
To stimulate the corpus luteum to produce progesterone, which stops decidua from shedding
What is the function of B-hCG in a clinical setting?
It is used to assess whether a patient is pregnant or not
What are the four phases of the uterine cycle?
Proliferative phase
Ovulation
Secretory phase
Menstruation
When does the follicular phase of the menstrual cycle coincide with the uterine cycle?
It exists between ovulation and the secretory phase
What hormone dominates during the proliferative phase of the uterine cycle?
Oestrogen
When does the luteal phase of the menstrual cycle coincide with the uterine cycle?
It exists between menstruation and the proliferative phase
What hormone dominates during the secretory phase of the uterine cycle?
Progesterone
What is menstruation?
It marks the beginning of a new menstrual cycle
When does menstruation occur?
It occurs in the absence of fertilisation
Once the corpus luteum has broken down and the internal lining of the uterus is shed
How long does menstrual bleeding occur?
2-7 days
