1: Physiology and pharmacology - Reproduction/Sex steroid axis Flashcards
Which endocrine glands are associated with the menstrual cycle?
Hypothalamus
Anterior pituitary gland
Ovaries
Which hormones are involved in the menstrual cycle?
GnRH
FSH
LH
Oestradiol (which is a type of oestrogen)
Progesterone
What are the four phases of the menstrual cycle?
Follicular phase
Ovulation
Luteal phase
Menstruation
How long does the menstrual cycle last on average?
28 days
Range = 21 - 35 days
How long does menstruation typically last?
3 - 8 days
When in the menstrual cycle does ovulation occur?
14 days
About halfway through
What is an ovarian follicle?
Fluid filled sac which contains an egg
During the follicular phase, oestrogen levels are (high / low).
Low oestrogen levels
What does the anterior pituitary do during the follicular phase?
Secretes FSH and LH
What type of special follicle develops in response to FSH secretion by the anterior pituitary gland?
Leading follicle
i.e the follicle which will actually release an egg
Which type of cells are found around the egg in the leading follicle?
Granulosa cells
What do granulosa cells release into the leading follicle?
Oestradiol
What particular processes does FSH cause in the leading follicle?
Growth of the follicle itself
Growth of granulosa cells, which release oestradiol
What effect does oestradiol have on the uterus?
Causes uterine wall to thicken
What is ovulation?
Release of an unfertilised egg from the ovaries
Happens at the end of the follicular phase
Which hormonal change triggers ovulation?
LH surge
What triggers the LH surge which causes ovulation?
Raised oestradiol
(produced by granulosa cells)
How does the follicle release the egg during ovulation?
Proteolytic enzymes digest the walls of the follicle
Where is the egg released during ovulation?
Into the Fallopian tubes
What are other names for the Fallopian tubes?
Uterine tubes
Salpinges
Which phase of the menstrual cycle occurs after ovulation?
Luteal phase
What colour are granulosa cells?
Yellow
What is the name given to the granulosa cells remaining after ovulation?
Corpus luteum
What hormone does the corpus luteum produce?
Progesterone
When does peak progesterone production by the corpus luteum occur?
Roughly one week after ovulation
e.g Day 21
What happens to the corpus luteum after the luteal phase if pregnancy occurs?
Placenta produces hCG which preserves the corpus luteum
=> Physiological amenorrhoea
Which phase occurs if there is no pregnancy after the luteal phase?
Menstruation
During menstruation, progesterone levels (increase / decrease).
Why?
decrease
Corpus luteum disintegrates
What is found in menses?
Tissue (mainly uterine wall)
Blood
Unfertilised egg
Changes in which hormones are seen in
a) ovulation
b) menstruation?
a) Ovulation => oestradiol increase, LH surge
b) Menstruation => progesterone decrease as corpus luteum disintegrates
Apart from triggering the LH surge in ovulation, what else does oestradiol cause?
Uterine wall thickening
Which axis controls the menstrual cycle?
Hypothalamic-pituitary-ovarian axis
Which hormone is released by the hypothalamus to stimulate secretion of TSH and LH from the anterior pituitary?
GnRH
TSH and LH are also known as what?
Gonadotrophins
Which precursor are female sex hormones produced from?
Cholesterol
Which part of the hypothalamus produces GnRH?
Arcturate nucleus
Which part of the pituitary gland produces FSH and LH?
Anterior pituitary gland
Which ligament fixes the ovary to the pelvic side wall?
IP ligament
(infundibulopelvic ligament)
What are the two parts of the ovary?
Cortex
Medulla
(as in adrenal glands)
What are the two parts of the uterus called?
Body
Cervix
from superior to inferior
What is the superficial layer of the uterus called?
Endometrium
Which hormone causes the endometrium to thicken?
Oestradiol
In the luteal phase, which two hormones must be produced to stop the endometrium sloughing off the uterine wall?
Progesterone (if corpus luteum disintegrates, levels fall)
hCG (human chorionic gonadotrophin, produced by placenta after implantation)
What is hCG?
Human chorionic gonadotrophin
Produced by placenta after implantation; stops sloughing of uterine wall i.e menstruation
Which cells are found in ovarian follicles and produce androgen?
Theca cells
Which hormone stimulates Theca cells to produce androgen?
LH
Which cells are found in ovarian follicles and produce aromatase?
Granulosa cells
Which hormone stimulates granulosa cells to produce aromatase?
FSH
Aromatase combines with ___ to form oestradiol.
androgen
Progesterone is produced by the ___ ___.
Progesterone can then be converted into androgen in ___ cells.
This product is then combined with aromatase to form oestrogen in ___ cells.
corpus luteum
Theca cells
Granulosa cells
GnRH is released in a ___ fashion by the hypothalamus.
pulsatile
What is FSH’s role in the HPO axis?
Stimulates leading follicle
Granulosa cell growth and aromatase activity
What does LH do?
Surge causes ovulation
Activates theca cells, which convert androgens to oestrogens
Which peptide hormones decrease FSH secretion by negative feedback?
Inhibins
Which peptides stimulate FSH secretion?
Activins
The testes can be split into which two compartments?
Seminiferous tubules
Interstitial fluid
Which cells are found in the
a) seminiferous tubules
b) interstitial fluid
of the testes?
a) Tubular cells - Sertoli cells, Germ cells
b) Interstitial cells - Leydig cells
What do Sertoli cells do?
Support Germ cells during their development into spermatozoa
What do Germ cells do?
Differentiate into spermatozoa
What do Leydig cells do?
Secrete testosterone in response to LH
Testosterone is secreted by which cell of the testes?
Leydig cells
What process does testosterone stimulate in the seminiferous tubules?
Spermatogenesis
Testosterone has what sort of effect on LH and GnRH secretion?
Negative feedback
Which hormone, along with testosterone, also stimulates spermatogenesis?
FSH
Which hormone reduces FSH secretion by the anterior pituitary and therefore reduces the rate of spermatogenesis?
Inhibin
Name a specific way in which Sertoli cells support Germ cells as they undergo spermatogenesis.
Secrete androgen-binding globulin (ABG) which mops up excess testosterone
Controlling the rate of spermatogenesis
What does dihydrotestosterone do?
Enlarges testes
Causes expression of male sexual characteristics
Anabolism
What is an acrosome?
Sac, found in the sperm cell head, which contains digestive enzymes
These enzymes break down the outer membrane of the oocyte to help with fertilisation
Sperm cells have large numbers of which organelle?
Mitochondria
Why are oocytes much larger than spermatozoa?
They contain:
Yolk proteins (food source)
Ribosomes
tRNA and mRNA
Where is the site of fertilisation?
Ampulla of Fallopian tubes
What happens to the cervical mucus when spermatozoa are detected in the uterus?
Cervical mucus thins
Which type of muscular movements bring the unfertilised oocyte to the ampulla of the Fallopian tubes?
Peristalsis
Where do spermatozoa mature?
In the female genital tract
Which process do spermatozoa undergo in the female genital tract before they are capable of fertilising an egg?
Capacitation
Following capacitation, which organelle do spermatozoa use to penetrate the egg?
Acrosome
Fertilisation occurs when which organelles of the oocyte and spermatozoa fuse?
Nuclei
What is the outer membrane of an oocyte called?
Zona pellucida
Once a spermatozoa has penetrated the zona pellucida using its acrosomal enzymes, what reaction occurs?
What does this reaction prevent?
Zona reaction - zona pellucida becomes impenetrable to any more sperm cells
Polyspermy
When a sperm cell penetrates the zona pellucida, the levels of certain ions changes to
a) prevent polyspermy
b) activate the egg.
Which ions?
Na+
Ca2+
Which process begins in an oocyte once it has been activated by sperm penetration?
Meiosis
Once an oocyte has been activated, its rate of protein synthesis (increases / decreases).
rate of protein synthesis & metabolism increases
The ___ sperm cell nucleus and ___ egg cell nucleus fuse to form a ___ zygote.
(haploid , diploid)
haploid sperm and egg
diploid zygote
