Physiology Flashcards
Where is sperm produced?
Produced by Sertoli cells
In the seminiferous tubules of the testes
Describe the hypothalamic-pituitary-gonadal axis?
Hypothalamus releases gonadotropin releasing hormone (GnRH) in a pulsatile manner
GnRH stimulates the release of FSH + LH from the anterior pituitary
FSH + LH act on the gonads (ovaries/testes) to stimulate synthesis and release of sex hormones
–> oestrogen, progesterone + testosterone
What is the first sign of puberty in females are when does it usually occur?
Thelarche –> breast buds develop
Around age 9-10
Which staging system is used to stage puberty?
Tanner staging
What is the second sign of puberty in females?
Pubarche –> growth of pubic hair
What is the third stage of puberty in females?
Menarche –> first menstrual period
What is the first sign of puberty in males?
Increase in testicular size
Where is testosterone synthesised in males?
By Leydig cells in testes
What are the other signs of puberty in males?
Enlargement of the penis
Growth of pubic hair
When is puberty considered precocious?
Development of secondary sexual characteristics
- before age 8 in girls
- before age 9 in boys
When is puberty considered delayed/absent?
Absence of secondary sexual characteristics by the age of:
- 13 in girls
- 16 in boys
What are the phases of the ovarian cycle during a menstrual cycle?
Follicular phase
Ovulation
Luteal phase
What happens during the follicular phase?
Follicles mature and grow
Increase in FSH + LH stimulate follicular growth and oestrogen production
Oestrogen levels rise
One dominant follicle continues to maturity
Finally –> LH surge
What happens in the ovulation phase?
LH surge –> follicle ruptures + mature oocyte is assisted to fallopian tubes by fimbria
The follicle continues secreting oestrogen + now progesterone - stalls cycle in anticipation of fertilisation
How long does the oocyte remain viable for fertilisation?
about 24 hours
What is the corpus luteum?
Tissue in the ovary that forms at the sight of a ruptured follicle following ovulation
What happens in the luteal phase?
Corpus luteum produces oestrogen, progesterone + inhibin to maintain conditions for fertilisation + implantation
In absence of fertilisation –> corpus luteum regresses after 14 days
–> significant fall in hormones
What happens to the corpus luteum if fertilisation occurs?
The syncytiotrophoblast of the embryo produces human chorionic gonadotrophin (HcG) –> exerts luteinising effect and maintains the corpus luteum (produces hormones to support pregnancy)
What are the phases of the uterine cycle?
Proliferative phase
Secretory phase
Menses
Which hormone is responsible for the proliferative phase of the uterine cycle?
Oestrogen
What happens during the proliferative phase of the uterine cycle?
Occurs along side the follicular phase of ovarian cycle
–> preparing for fertilisation + implantation
Oestrogen initiates:
- thickening of endometrium
- growth + motility of myometrium
- production of a thin alkaline cervical mucus (to facilitate sperm transport)
Which hormone is responsible for the secretory phase of the uterine cycle?
Progesterone
What happens in the secretory phase of the uterine cycle?
Occurs alongside the luteal phase
Progesterone stimulates:
- further endometrial thickening into glandular secretory form
- thickening of myometrium
- reduced motility of myometrium
- thick, acidic cervial mucus production (hostile to sperm - prevents polyspermy)
What happens during menses?
In the absence of fertilisation, once corpus luteum has broken down –> lining of uterus is shed
What is considered a normal volume of blood loss during menses?
10-80 mls
What is the average age of menopause (final menarche)?
51
Which hormone change characterises the menopause?
Reduction in oestrogen
+ increase in FSH and LH
Which symptoms are associated with the perimenopause/menopause?
Hot flushes Urinary incontinence Increased UTIs Irregular vaginal bleeding Dyspareunia (due to vaginal atrophy with drop in oestrogen) Reduced bone mass
How is the menopause defined?
Amenorrhoea for 12 months
What is considered ‘early menopause’?
Age between 40 - 45
How is the menopause ‘diagnosed’?
Serum FSH > 40
Which treatment can be offered for women who cannot tolerate the symptoms of menopause?
HRT
- tablets
- transdermal patches
- oestrogenic vaginal ring
What are the risks associated with HRT?
Increased risk of breast, endometrial + ovarian cancers
Increased risk of VTE + ischaemic stroke
Where does conception usually occur?
Ampulla of the fallopian tube
