The reproductive system (17) Flashcards
What do the Fallopian tubes have that help move the egg towards the central components of the female reproductive tract?
cilia- help ‘waft’
spiral muscle- peristalsis
What do we cut in a vasectomy?
vas deferens
What would cause an ectopic pregnancy?
- any defect in cilia or spiral muscles of Fallopian tube (can lead to infertility bc fertilisation usually occurs in widest part- ampulla)
- if fertilisation occurs further up–> ectopic pregnancy: as embryo grows- Fallopian tubes rupture–> catastrophic haemorrhage
What is uterine prolapse?
loss of tone of the pelvic floor (levator ani and coccygeus)
What is the arterial blood supply to the female reproductive tract?
ovaries: ovarian arteries (from aorta)
uterus/vagina: uterine arteries (from internal iliac artery)
What are the 2 main functions of the gonads?
gametogenesis and reproductive hormone production
What is the lifespan of germ cells in males?
- gametogenesis begins at puberty
- spermatogonia differentiate and self-renew–> pool available for subsequent spermatogenic cycles throughout life (continuous fertility)
- produce around 1500 mature sperm/second
What is the lifespan of germ cells in females?
before birth
- multiplication of oogonia to around 6 million/ ovary
- form 1y oocytes (primordial follicles) within ovarian follicles–> get suspended in prophase of meiosis
- some degenerate (atresia)
- at birth, around 2 million/ovary
by puberty
- <0.5 million/ ovary (due to further atresia)
What is the process of spermatogenesis?
2n germ cell
2n spermatogonium–> mitosis
2n 1y spermatocytes–> 1st meiotic divison
n 2y spermatocytes–> 2nd meiotic division
n spermatids–> differentiation
spermatozoa/sperm
in seminiferous tubules- move inwards as develop
What are the Sertoli cells?
- within seminiferous tubules
- has FSH receptors
- supports developing germ cells: assists movement to tubular lumen, transfers nutrients from capillaries to developing germ cells, and involved in phagocytosis of damaged germ cells
- hormone synthesis: release inhibin and activin, AMH and ABP
What are the Leydig cells?
- between seminiferous tubules (not inside)
- pale cytoplasm bc cholesterol-rich
- has LH receptors
- hormone synthesis: when stimulated by LH, secrete androgens e.g. testosterone
What hormones are produced in the testes?
- androgens (testosterone, dihydrotestosterone, androstenedione)
- inhibin: acts on pituitary to inhibit FSH secretion
- oestrogens (from androgen aromatisation)
What is the process of oogenesis?
N.B. in 2nd trimester of pregnancy, all oogonia develop into 1y oocytes- locked here
2n germ cell
2n oogonium–> mitosis
2n 1y oocytes–> 1st meiotic division at menarche
n 2y oocytes (+1st polar bodies) –> 2nd meiotic divison when sperm fuses
n ootids (+2nd polar bodies)–> differentiation
n ova
What is menarche?
start of menstrual cycle
What is the process of folliculogenesis?
- PRIMORDIAL FOLLICULE- contains 1y oocyte at birth
- becomes 1Y FOLLICLE- surrounded by layers of granulosa and theca cells
- mature to form 2Y FOLLICLE w/ fluid-filled cavity (antrum) and FSH+LH receptors
- MATURE FOLLICLE/Graafian/Preovulatory- forms halfway through menstrual cycle- 2y oocyte in cumulus mass
- RUPTURED FOLLICLE- 2y oocyte ruptures out
- follicle degenerates into CORPUS LUTEUM- secretes progesterone
- degenerates into CORPUS ALBICANS
How can we tell if someone has ovulated?
- measure day 21 progesterone and
- maybe ultrasound (presence of corpus luteum)
if corpus luteum–> must be successful ovulation
What hormones are made by the ovaries?
- oestrogens (oestradiol, oestrone, oestriol)
- progestogens (progesterone)
- androgens (testosterone, androstenedione, DHEA)
- relaxin
- inhibin
What is a theca cell?
- outer part of ovarian follicles
- support folliculogenesis: structural and nutritional
- hormone synthesis: make androgens- stimulated by LH (theca cell overactivity–> high androgen levels)
What is a granulosa cell?
- inner part of ovarian follicles
- hormone synthesis: convert androgens to oestrogen (by aromatase)- stimulated by FSH
AND secrete inhibin and activin (affect FSH) - after ovulation–> turn into granulosa lutein cells- produce progesterone (maintain endometrium) and relaxin (prepare endometrium for pregnancy)
What is the common initial substrate for all gonadal steroid hormones?
cholesterol
How does the Hypothalamic-Pituitary-Gonadal Axis (HPG) work?
kisspeptin neurons secrete kisspeptin onto receptors on GnRH neurons in hypothalamus–> secrete GnRH
- -> released via hypophyseal portal circulation in pulses to gonadotrophs in pituitary gland
- -> gonadotrophs make LH/FSH- enter systemic circulation
- -> these act on gonads to make oestrogen/testosterone (diurnal- high levels in morning)
- -> oestrogen/testosterone feedback directly onto pituitary AND kisspeptin neurons (mainly -ve)
What happens to the HPG axis in hyperprolactinaemia?
- prolactin binds to prolactin receptors on kisspeptin neurons in hypothalamus
- inhibits kisspeptin release
- dec. in downstream GnRH/LH/FSH/T/Oest
- leads to oligo or amenorrhoea/low libido/infertility/osteoporosis
What is the overall structure of the menstrual cycle?
day 1: first day of bleeding due to drop in progesterone- degradation of endometrial lining
1-14: follicle phase then luteal phase (potential pregnancy)
day 14: ovulation
then up to 28 days
What is it called when menstrual cycle >35 days?
oligomenorrhoea
Why does body temperature increase by at least 0.5 degrees the day after ovulation?
due to progesterone increase
What are the basic principles of pregnancy?
- semen formation and voyage
- capacitation
- fertilisation (acrosome and cortical reaction)
- implantation (attachment and decidualisation)
- hormonal changes of pregnancy
- parturition (labour)
- lactation
What structures does the spermatic cord contain?
- testicular artery
- paminiform plexus
- autonomic + GF nerves
- lymph vessels
- Vas deferens
Why are do the testes hang outside the body?
keep temperature slightly lower for sperm formation by 2-3 degrees
What are the 3 muscles in the penis?
2 X corpora cavernosa
1 X corpora spongiosum
What type of stimulation, sympathetic or parasympathetic, is responsible for erection/ejaculation?
Point and Shoot
parasympathetic- erection generation- arterial relaxation allowing blood into penis- inc. pressure- blocks venous drainage
sympathetic- ejaculation
What are the parts of the male reproductive system?
testes: make sperm
epididymis: where sperm mature + are stored
vas deferens/ductus deferens: tube from testes taking sperm to back of prostate
seminal vesicle: help provide seminal fluid together with prostate and bulbourethral gland- also important in secreting pre-ejaculate
What does seminal fluid contain?
- fructose and citric acid- nutrients
- bicarbonate- helps neutralise acidic environment of vagina
- fibrinogen- thickening agent
- fibrinolytic enzymes- help sperm break through
What is the arterial blood supply to the testes?
testicular arteries from the aorta via the spermatic cord
What is the lymphatic drainage to the testes?
para-aortic lymph nodes
What are the 3 layers of the capsule of the testes?
inside- tunica vasculosa
then tunica albuginea
then tunica vaginalis- covers both testes and epididymis
What are the linings of the uterus?
outside- perimetrium
myometrium- muscle
endometrium- specialised layer of endometrial cells- shed at menses due to vasoconstriction of arterioles
How is sterility maintained superior to the cervix?
- monthly shedding of endometrial lining
- thick cervical mucus
- narrow os
- pH <4.5 acidic
What is the lymphatic drainage to the ovaries?
para-aortic lymph nodes
What is the lymphatic drainage to the uterus/vagina?
iliac, sacral, aortic and inguinal lymph nodes
What happens to hormones levels during the menstrual cycle?
- both slowly rise during follicular phase
- stimulates more oestrogen production–> gets to high point and switches to +ve feedback
- causes LH surge–> triggers final steps of follicle maturation
- then forms corpus luteum produces progesterone- levels increase until corpus luteum dies–> levels dec.
How far does the sperm have to travel from testis to Fallopian tube?
100,000 x its length
What is inside semen?
- spermatozoa
- seminal fluid
- leukocytes
- potential viruses e.g. HIV
What is capacitation of sperm?
achieving ability to fertilise- occurs in the female reproductive tract:
- lose glycoprotein coat
- change in surface membrane characteristics
- develop whiplash movements of tail
N.B. takes place in ionic + proteolytic environment of Fallopian tube… dependent on oestrogen and calcium
What is the acrosome reaction?
- when capacitated sperm gets to egg in ampulla (widest part of Fallopian tube)
- sperm binds to ZP3 glycoprotein
- acrosome releases hyaluronidase and proteolytic enzymes
- can then penetrate zona pellucida
What happens during fertilisation and the cortical reaction?
- occurs within fallopian tube (ampulla)
- triggers cortical reaction to stop more sperm entering
AND final step of maturation 2y oocyte–> ovum - cortical granules degrade zona pellucida–> so no more ZP3 binding sites
- haploid–> diploid zygote
What happens after fertilisation with the development of conceptus?
- zygote continues to divide as it moved down Fallopian tube to uterus for implantation
- receives nutrients from uterine secretions driven by progesterone
- ‘free living’ phase can last for up to 9-10 days
*What happens during implantation?
attachment phase: outer trophoblast cells contact uterine surface epithelium
THEN
decidualisation: changes in underlying uterine stromal tissue
N.B. requires progesterone domination in the presence of oestrogen
What is LIF?
leukaemia inhibitory factor
- from endometrial cells
- stimulates adhesion of blastocyst to endometrium
*What is IL11?
interleukin-11
- from endometrial cells
- released into uterine fluid
- may be involved in attachment
*What is decidualisation?
endometrial changes due to progesterone:
- glandular epithelial secretion
- glycogen accumulation in stromal cell cytoplasm
- growth of capillaries
- inc. vascular permeability –> oedema
What factors are involved in decidualisation?
IL11, histamine, certain prostaglandins and TGFb
Where is hCG produced?
placenta
What is measured in a pregnancy test?
hCG (human chorionic gonadotrophin)
What is progesterone and oestrogen production like during pregnancy?
first 40 days
- progesterone and oestrogen made by corpus luteum in maternal ovary (stimulated by hCG- taking over role of LH)
- essential for developing fetoplacental unit
- inhibit maternal LH+ FSH by -ve feedback
from day 40
- placenta starts to take over in production of hormones^
*What are the hormones involved in parturition?
oxytocin–> uterine contraction and cervical dilation
cortisol, oestrogen
*What hormones increase during pregnancy?
ACTH, adrenal steroids, prolactin, IGF2, iodothyronines, PTH related peptides
*What hormones decrease during pregnancy?
gonadotrophin, pituitary GH, TSH
What is the endocrine control involved in lactation (both mechanisms)?
- mechanical stimulation of nipple and surrounding area activates afferent pathways
- afferent signals integrated in the hypothalamus–> stimulate oxytocin-releasing neuron activity and inhibit dopamine release from dopaminergic neurons
- less dopamine in hypothalamic-pituitary portal system–> less inhibition of anterior pituitary lactotrophs
- APs travel down oxytocin neurones–> oxytocin secreted into bloodstream
- less dopamine in hypothalamic-pituitary portal system–> less inhibition of anterior pituitary lactotrophs
- inc. plasma prolactin inc. milk secretion in mammary glands
- inc. plasma oxytocin inc. milk ejection in mammary glands
- inc. plasma prolactin inc. milk secretion in mammary glands
