Male and Female Physiology Flashcards
What is GnRH?
Gonadotrophin releasing hormone
Produced by hypothalamus stimulates release of FSH and LH from anterior pituitary
What are the gonadrotrophins?
LH (lutenising hormone) and FSH (follicle stimulating hormone)
What do the gonadotrophins do?
Stimulate release of oestrogen, progesterone and testosterone
What is the HPO axis?
Hypothalamus produces GnRH
Acts on anterior pituitary to produce LH and FSH
FSH stimulates egg follicles to grow and selects dominant follicle
LH midcycle surge triggers ovulation
LH and FSH also responsible for the production of oestrogen & progesterone
Describe the HPO axis feedback?
Negative feedback to the ant. pituitary and hypothalamus as oestrogen & progesterone levels start to rise with develop of follicle leads to less LH and FSH being produced so that there is only one egg produced per cycle
Positive feedback as oestrogen levels reach a certain threshold lead to LH surge (day 12-14) which triggers ovulation
What are the two phases of the ovarian cycle?
Follicular
Luteal
Describe the follicular phase of the ovarian cycle
Progesterone levels drop at end of menstrual cycle
Neg feedback –> GnRH production by hypothalamus –> LH and FSH produced by pituitary
FSH acts on granulosa cells of primordial follicle & cause it to change into primary follicle
Granulosa cells also produce oestrogen
Midcycle surge of LH leads to release of the egg
Describe the luteal phase of the ovarian cycle
Follicle after egg release = corpus luteum
Corpus luteum produces progesterone which acts on the lining of the womb
Corpus luteum matures and if no pregnancy - it generates and goes white (corpus albicans)
Which phase of the uterine cycle corresponds with the follicular phase of the ovarian cycle?
Proliferative
Which phase of the uterine cycle corresponds with the luteal phase of the ovarian cycle?
Secretory
What occurs in the proliferative phase of the uterine cycle?
As follicular phase is occurring, oestrogen is being secreted –> proliferation of the womb
Endometrium grows thick for implantation
What occurs in the secretory phase of the uterine cycle?
Progesterone released by corpus luteum dilates the vessels in the endometrium increasing the BS to the endometrium
Also causes endometrium to produce hormones making endometrium receptive to implantation
If there is no fertilisation what occurs to the endometrium?
All hormones drop and endometrium cannot sustain itself so there is a menstrual bleed
What is the action of oestrogen on the endometrium?
Causes proliferation of endometrial stroma and development of the endometrial glands
What is the action of progesterone on the endometrium?
Induces secretory functions of the endometrium
Responsible for spinal artery development
What are the functions of oestrogen?
- Proliferation of endometrium
- Promotes development of genitalia
- Promotes growth of follicle
- Causes LH surge
- Responsible for female fat distribution
- Increases hepatic synthesis of transport proteins
- Upregulates oestrogen, progesterone and LH receptors
- Increases TBG levels
What are the functions of progesterone?
- Maintenance of endometrium and pregnancy
- Thickens cervical mucous
- Decreases myometrial excitability
- Increases body temperature
- Responsible for spiral artery development
What determines the no. of eggs a woman has?
Girls born with no. of eggs for lifetime
Predetermined by mother’s health and genetic factors
When do the ovaries have the maximum no. of eggs?
At 5m gestation
How many eggs will the ovaries have at birth?
2 million on average
Describe the process of oogenesis
Oogonium (stem cells) undergo mitotic divisions –> primary oocytes (this is completely at/shortly after birth)
Meiosis starts but arrested in the prophase
Group of primary oocytes are hormone responsive in each cycle - one grows rapidly to complete first meiotic division & releases haploid secondary oocyte at ovulation
Extra genetic information released as 1st polar body
Secondary oocyte completely second meiotic division when fertilised by a sperm to form the mature ovum and second polar body
When is peak fertility?
20-30
When does fertility tend to dip?
After 35
Where is testosterone produced?
Leydig cells in testes
What is the function of FSH in males?
Acts on Sertoli cells and stimulates sperm production
What is the function of LH in males?
Acts on Leydig cells leading to testosterone production
What do the germ cells in the seminiferous tubules do?
Produce sperm
What does testosterone do?
Maintains secondary male sex characteristics
Describe the path of sperm travel and release
Sperm aggregate & move towards the epididymis
Epididymis connected to vas deferens which combines with secretions from seminal vesicles and prostate and joints penile urethra
Describe spermatogenesis
Mitosis of spermatogonium never stops
Spermatogonium under go mitosis into primary spermatocyte
Primary spermatocyte undergoes meiosis 1 into secondary spermatocyte which undergoes meiosis 2 into spermatids
What is the process of spermiogenesis?
Spermatids becoming mature sperm
Occurs in epididymis - develop tail function, heads grow, genetic material grows stronger
When do men stop producing sperm?
They don’t
Sperm quality reduces after 45
How many sperm are produced per day?
30 million
How long does it take to produce sperm?
60-75 days
How long does it take to transport sperm to epididymis?
10-14 days
What factors can affect oogenesis & spermatogenesis?
Problem with hormonal control (genetic, tumours, medications, function (e.g. stress/losing/gaining wt)
Problem at site of production (genetic, cancer Rx induced, surgery, trauma, infections)
