Reproductive system Flashcards
Hypothalamus releases …… which acts on ……
GnRH- Gonadotropin releasing hormone
Pituitary gland
Pituitary gland releases ….. which acts on …..
Lutenising hormone, FSH
Gonads
Gonads
Produce germ cells
Produce sex steroid hormones
Ovaries release
Oestrogens (ERs- oestrogen receptors) eg oestrone, oestradiol
Progesterone (PRs)
Testes release
Androgens: testosterone
Dihydrotestosterone (DHT) is the common form in the body
seminiferous tubules
In the testes
The site of sperm production (spermatogenesis) and hormone synthesis
2 cell types in the seminiferous tubules
Leydig- testoterone producing
Serroli- in wall of tubules where sperm are derived from
Spermatogenesis
FSH/testosterone drive production of sperm
Testosterone acts locally on serrolis, and gets into bloodstream via testicular vein
Precursors of androgens
cholesterol, pregnenolone, progesterone
Androgens effect on Hypo
decr GnRH secretion
-ve feedback
Androgen effects on Pituitary
decr LH secretion
-ve feedback
Androgens effect on metabolism
‘anabolic steroids’
Protein anabolism
Bone growth
Stimulates erythropoietin
Androgen effects on testes
spermatogenesis
Androgens effect on male sex charateristics
Differentiation of male reproductive organs
Secondary sex characteristics
Sex drive
Sertoli cells also release
Inhibin, -vely feeds back onto pituitary to inhibit production of only FSH
Ovarian functions
Oogenesis
Maturation of the oocyte
Ovulation
Secretion of female sex steroid hormones
Oogenesis
Ovum production
Occurs monthly in ovarian follicles
Part of ovarian cycle
Ovarian cycle consists of
Follicular phase (preovulatory) Luteal phase (postovulatory)
The follicular phase
Maturation of primary follicles in under control of FSH
Follical cells develop into granulosar cells and follicle cells around the oocyte develop into theca cells
Luteal phase
Ovulation and corpus luteum formation under control of LH
Corpus luteum starts to make progesterone once egg leaves
Corpus luteum forms albicans if egg doesn’t implant
Functions of the uterus
- Muscular organ
- mechanical protection
- nutritional support
- waste removal for the developing embryo and fetus
Uterine cycle involves changes in the uterine wall
Uterine wall has 3 layers
Myometrium- outer muscular layer
Endometrium- thin, inner glandular mucosa
Perimetrium- incomplete serosa continuous with the peritoneum
Ovarian cycle summary
In the ovary the egg develops, released into fallopian tube- implants into uterus wall if meets a sperm
Uterus develops endometrium to receive implanted egg- shed if no egg
Uterine cycle
repeating series of changes in the endometrium
Continues from menarche (1st menstruation) to menopause
3 stages: menses, proliferative phase, secretory phase
Menses
Degeneration of the endo = menstruation
Proliferative phase
Restoration of the endo
Secretory phase
Endometrial glands enlarge and accelerate their rates of secretion
FSH
stimulates follicular development
LH
maintains structure and secretory function of corpus luteum
Oestrogens
multiple functions
Progesterones/Progestogens
Stimulate endometrial growth and secretion
Hormonal control of ovarian function
Hypo secretion of GnRH, acts on pituitary to secrete FSH and LH
FSH acts on granulosa cells, which influence oocytes and release inhibin- negatively feeds back onto pituitary (primarily FSH inhibition)
LH acts on theca cells which release androgen substrate required for estrogen biosynthesis
Oestrogen engatively feeds back onto Pituitary and hypothalamus
GnRH
Function of gonads controlled by hypo and AP, under influence of higher brain centres in the cortex
Leads to pulsatile GnRH release (freq 60-90 mins) and hence incr in pulsatile gonadotrophin secretion from the pituitary at puberty
Ovulation day
14
When is LH highest
day 14
